1/*
2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
| 1/*
2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
|
34 * $FreeBSD: head/sys/netinet/tcp_input.c 121285 2003-10-20 16:19:01Z ume $
| 34 * $FreeBSD: head/sys/netinet/tcp_input.c 121628 2003-10-28 05:47:40Z sam $
|
35 */
36
37#include "opt_ipfw.h" /* for ipfw_fwd */
38#include "opt_inet6.h"
39#include "opt_ipsec.h"
40#include "opt_mac.h"
41#include "opt_tcpdebug.h"
42#include "opt_tcp_input.h"
43
44#include <sys/param.h>
45#include <sys/kernel.h>
46#include <sys/mac.h>
47#include <sys/malloc.h>
48#include <sys/mbuf.h>
49#include <sys/proc.h> /* for proc0 declaration */
50#include <sys/protosw.h>
51#include <sys/signalvar.h>
52#include <sys/socket.h>
53#include <sys/socketvar.h>
54#include <sys/sysctl.h>
55#include <sys/syslog.h>
56#include <sys/systm.h>
57
58#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
59
60#include <net/if.h>
61#include <net/route.h>
62
63#include <netinet/in.h>
64#include <netinet/in_pcb.h>
65#include <netinet/in_systm.h>
66#include <netinet/in_var.h>
67#include <netinet/ip.h>
68#include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
69#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
70#include <netinet/ip_var.h>
71#include <netinet/ip6.h>
72#include <netinet/icmp6.h>
73#include <netinet6/in6_pcb.h>
74#include <netinet6/ip6_var.h>
75#include <netinet6/nd6.h>
76#include <netinet/tcp.h>
77#include <netinet/tcp_fsm.h>
78#include <netinet/tcp_seq.h>
79#include <netinet/tcp_timer.h>
80#include <netinet/tcp_var.h>
81#include <netinet6/tcp6_var.h>
82#include <netinet/tcpip.h>
83#ifdef TCPDEBUG
84#include <netinet/tcp_debug.h>
85#endif /* TCPDEBUG */
86
87#ifdef FAST_IPSEC
88#include <netipsec/ipsec.h>
89#include <netipsec/ipsec6.h>
90#endif /*FAST_IPSEC*/
91
92#ifdef IPSEC
93#include <netinet6/ipsec.h>
94#include <netinet6/ipsec6.h>
95#include <netkey/key.h>
96#endif /*IPSEC*/
97
98#include <machine/in_cksum.h>
99
100MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
101
102static const int tcprexmtthresh = 3;
103tcp_cc tcp_ccgen;
104
105struct tcpstat tcpstat;
106SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
107 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
108
109static int log_in_vain = 0;
110SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
111 &log_in_vain, 0, "Log all incoming TCP connections");
112
113static int blackhole = 0;
114SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
115 &blackhole, 0, "Do not send RST when dropping refused connections");
116
117int tcp_delack_enabled = 1;
118SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
119 &tcp_delack_enabled, 0,
120 "Delay ACK to try and piggyback it onto a data packet");
121
122#ifdef TCP_DROP_SYNFIN
123static int drop_synfin = 0;
124SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
125 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
126#endif
127
128static int tcp_do_rfc3042 = 0;
129SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW,
130 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)");
131
132static int tcp_do_rfc3390 = 0;
133SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
134 &tcp_do_rfc3390, 0,
135 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
136
137struct inpcbhead tcb;
138#define tcb6 tcb /* for KAME src sync over BSD*'s */
139struct inpcbinfo tcbinfo;
140struct mtx *tcbinfo_mtx;
141
142static void tcp_dooptions(struct tcpopt *, u_char *, int, int);
143static void tcp_pulloutofband(struct socket *,
144 struct tcphdr *, struct mbuf *, int);
145static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
146 struct mbuf *);
147static void tcp_xmit_timer(struct tcpcb *, int);
148static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
149static int tcp_timewait(struct tcptw *, struct tcpopt *,
150 struct tcphdr *, struct mbuf *, int);
151
152/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
153#ifdef INET6
154#define ND6_HINT(tp) \
155do { \
156 if ((tp) && (tp)->t_inpcb && \
157 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \
158 (tp)->t_inpcb->in6p_route.ro_rt) \
159 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
160} while (0)
161#else
162#define ND6_HINT(tp)
163#endif
164
165/*
166 * Indicate whether this ack should be delayed. We can delay the ack if
167 * - there is no delayed ack timer in progress and
168 * - our last ack wasn't a 0-sized window. We never want to delay
169 * the ack that opens up a 0-sized window and
170 * - delayed acks are enabled or
171 * - this is a half-synchronized T/TCP connection.
172 */
173#define DELAY_ACK(tp) \
174 ((!callout_active(tp->tt_delack) && \
175 (tp->t_flags & TF_RXWIN0SENT) == 0) && \
176 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
177
178static int
179tcp_reass(tp, th, tlenp, m)
180 register struct tcpcb *tp;
181 register struct tcphdr *th;
182 int *tlenp;
183 struct mbuf *m;
184{
185 struct tseg_qent *q;
186 struct tseg_qent *p = NULL;
187 struct tseg_qent *nq;
188 struct tseg_qent *te;
189 struct socket *so = tp->t_inpcb->inp_socket;
190 int flags;
191
192 /*
193 * Call with th==0 after become established to
194 * force pre-ESTABLISHED data up to user socket.
195 */
196 if (th == 0)
197 goto present;
198
199 /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */
200 MALLOC(te, struct tseg_qent *, sizeof (struct tseg_qent), M_TSEGQ,
201 M_NOWAIT);
202 if (te == NULL) {
203 tcpstat.tcps_rcvmemdrop++;
204 m_freem(m);
205 return (0);
206 }
207
208 /*
209 * Find a segment which begins after this one does.
210 */
211 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
212 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
213 break;
214 p = q;
215 }
216
217 /*
218 * If there is a preceding segment, it may provide some of
219 * our data already. If so, drop the data from the incoming
220 * segment. If it provides all of our data, drop us.
221 */
222 if (p != NULL) {
223 register int i;
224 /* conversion to int (in i) handles seq wraparound */
225 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
226 if (i > 0) {
227 if (i >= *tlenp) {
228 tcpstat.tcps_rcvduppack++;
229 tcpstat.tcps_rcvdupbyte += *tlenp;
230 m_freem(m);
231 FREE(te, M_TSEGQ);
232 /*
233 * Try to present any queued data
234 * at the left window edge to the user.
235 * This is needed after the 3-WHS
236 * completes.
237 */
238 goto present; /* ??? */
239 }
240 m_adj(m, i);
241 *tlenp -= i;
242 th->th_seq += i;
243 }
244 }
245 tcpstat.tcps_rcvoopack++;
246 tcpstat.tcps_rcvoobyte += *tlenp;
247
248 /*
249 * While we overlap succeeding segments trim them or,
250 * if they are completely covered, dequeue them.
251 */
252 while (q) {
253 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
254 if (i <= 0)
255 break;
256 if (i < q->tqe_len) {
257 q->tqe_th->th_seq += i;
258 q->tqe_len -= i;
259 m_adj(q->tqe_m, i);
260 break;
261 }
262
263 nq = LIST_NEXT(q, tqe_q);
264 LIST_REMOVE(q, tqe_q);
265 m_freem(q->tqe_m);
266 FREE(q, M_TSEGQ);
267 q = nq;
268 }
269
270 /* Insert the new segment queue entry into place. */
271 te->tqe_m = m;
272 te->tqe_th = th;
273 te->tqe_len = *tlenp;
274
275 if (p == NULL) {
276 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
277 } else {
278 LIST_INSERT_AFTER(p, te, tqe_q);
279 }
280
281present:
282 /*
283 * Present data to user, advancing rcv_nxt through
284 * completed sequence space.
285 */
286 if (!TCPS_HAVEESTABLISHED(tp->t_state))
287 return (0);
288 q = LIST_FIRST(&tp->t_segq);
289 if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
290 return (0);
291 do {
292 tp->rcv_nxt += q->tqe_len;
293 flags = q->tqe_th->th_flags & TH_FIN;
294 nq = LIST_NEXT(q, tqe_q);
295 LIST_REMOVE(q, tqe_q);
296 if (so->so_state & SS_CANTRCVMORE)
297 m_freem(q->tqe_m);
298 else
| 35 */
36
37#include "opt_ipfw.h" /* for ipfw_fwd */
38#include "opt_inet6.h"
39#include "opt_ipsec.h"
40#include "opt_mac.h"
41#include "opt_tcpdebug.h"
42#include "opt_tcp_input.h"
43
44#include <sys/param.h>
45#include <sys/kernel.h>
46#include <sys/mac.h>
47#include <sys/malloc.h>
48#include <sys/mbuf.h>
49#include <sys/proc.h> /* for proc0 declaration */
50#include <sys/protosw.h>
51#include <sys/signalvar.h>
52#include <sys/socket.h>
53#include <sys/socketvar.h>
54#include <sys/sysctl.h>
55#include <sys/syslog.h>
56#include <sys/systm.h>
57
58#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
59
60#include <net/if.h>
61#include <net/route.h>
62
63#include <netinet/in.h>
64#include <netinet/in_pcb.h>
65#include <netinet/in_systm.h>
66#include <netinet/in_var.h>
67#include <netinet/ip.h>
68#include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
69#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
70#include <netinet/ip_var.h>
71#include <netinet/ip6.h>
72#include <netinet/icmp6.h>
73#include <netinet6/in6_pcb.h>
74#include <netinet6/ip6_var.h>
75#include <netinet6/nd6.h>
76#include <netinet/tcp.h>
77#include <netinet/tcp_fsm.h>
78#include <netinet/tcp_seq.h>
79#include <netinet/tcp_timer.h>
80#include <netinet/tcp_var.h>
81#include <netinet6/tcp6_var.h>
82#include <netinet/tcpip.h>
83#ifdef TCPDEBUG
84#include <netinet/tcp_debug.h>
85#endif /* TCPDEBUG */
86
87#ifdef FAST_IPSEC
88#include <netipsec/ipsec.h>
89#include <netipsec/ipsec6.h>
90#endif /*FAST_IPSEC*/
91
92#ifdef IPSEC
93#include <netinet6/ipsec.h>
94#include <netinet6/ipsec6.h>
95#include <netkey/key.h>
96#endif /*IPSEC*/
97
98#include <machine/in_cksum.h>
99
100MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
101
102static const int tcprexmtthresh = 3;
103tcp_cc tcp_ccgen;
104
105struct tcpstat tcpstat;
106SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
107 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
108
109static int log_in_vain = 0;
110SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
111 &log_in_vain, 0, "Log all incoming TCP connections");
112
113static int blackhole = 0;
114SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
115 &blackhole, 0, "Do not send RST when dropping refused connections");
116
117int tcp_delack_enabled = 1;
118SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
119 &tcp_delack_enabled, 0,
120 "Delay ACK to try and piggyback it onto a data packet");
121
122#ifdef TCP_DROP_SYNFIN
123static int drop_synfin = 0;
124SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
125 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
126#endif
127
128static int tcp_do_rfc3042 = 0;
129SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW,
130 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)");
131
132static int tcp_do_rfc3390 = 0;
133SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
134 &tcp_do_rfc3390, 0,
135 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
136
137struct inpcbhead tcb;
138#define tcb6 tcb /* for KAME src sync over BSD*'s */
139struct inpcbinfo tcbinfo;
140struct mtx *tcbinfo_mtx;
141
142static void tcp_dooptions(struct tcpopt *, u_char *, int, int);
143static void tcp_pulloutofband(struct socket *,
144 struct tcphdr *, struct mbuf *, int);
145static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
146 struct mbuf *);
147static void tcp_xmit_timer(struct tcpcb *, int);
148static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
149static int tcp_timewait(struct tcptw *, struct tcpopt *,
150 struct tcphdr *, struct mbuf *, int);
151
152/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
153#ifdef INET6
154#define ND6_HINT(tp) \
155do { \
156 if ((tp) && (tp)->t_inpcb && \
157 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \
158 (tp)->t_inpcb->in6p_route.ro_rt) \
159 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
160} while (0)
161#else
162#define ND6_HINT(tp)
163#endif
164
165/*
166 * Indicate whether this ack should be delayed. We can delay the ack if
167 * - there is no delayed ack timer in progress and
168 * - our last ack wasn't a 0-sized window. We never want to delay
169 * the ack that opens up a 0-sized window and
170 * - delayed acks are enabled or
171 * - this is a half-synchronized T/TCP connection.
172 */
173#define DELAY_ACK(tp) \
174 ((!callout_active(tp->tt_delack) && \
175 (tp->t_flags & TF_RXWIN0SENT) == 0) && \
176 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
177
178static int
179tcp_reass(tp, th, tlenp, m)
180 register struct tcpcb *tp;
181 register struct tcphdr *th;
182 int *tlenp;
183 struct mbuf *m;
184{
185 struct tseg_qent *q;
186 struct tseg_qent *p = NULL;
187 struct tseg_qent *nq;
188 struct tseg_qent *te;
189 struct socket *so = tp->t_inpcb->inp_socket;
190 int flags;
191
192 /*
193 * Call with th==0 after become established to
194 * force pre-ESTABLISHED data up to user socket.
195 */
196 if (th == 0)
197 goto present;
198
199 /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */
200 MALLOC(te, struct tseg_qent *, sizeof (struct tseg_qent), M_TSEGQ,
201 M_NOWAIT);
202 if (te == NULL) {
203 tcpstat.tcps_rcvmemdrop++;
204 m_freem(m);
205 return (0);
206 }
207
208 /*
209 * Find a segment which begins after this one does.
210 */
211 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
212 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
213 break;
214 p = q;
215 }
216
217 /*
218 * If there is a preceding segment, it may provide some of
219 * our data already. If so, drop the data from the incoming
220 * segment. If it provides all of our data, drop us.
221 */
222 if (p != NULL) {
223 register int i;
224 /* conversion to int (in i) handles seq wraparound */
225 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
226 if (i > 0) {
227 if (i >= *tlenp) {
228 tcpstat.tcps_rcvduppack++;
229 tcpstat.tcps_rcvdupbyte += *tlenp;
230 m_freem(m);
231 FREE(te, M_TSEGQ);
232 /*
233 * Try to present any queued data
234 * at the left window edge to the user.
235 * This is needed after the 3-WHS
236 * completes.
237 */
238 goto present; /* ??? */
239 }
240 m_adj(m, i);
241 *tlenp -= i;
242 th->th_seq += i;
243 }
244 }
245 tcpstat.tcps_rcvoopack++;
246 tcpstat.tcps_rcvoobyte += *tlenp;
247
248 /*
249 * While we overlap succeeding segments trim them or,
250 * if they are completely covered, dequeue them.
251 */
252 while (q) {
253 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
254 if (i <= 0)
255 break;
256 if (i < q->tqe_len) {
257 q->tqe_th->th_seq += i;
258 q->tqe_len -= i;
259 m_adj(q->tqe_m, i);
260 break;
261 }
262
263 nq = LIST_NEXT(q, tqe_q);
264 LIST_REMOVE(q, tqe_q);
265 m_freem(q->tqe_m);
266 FREE(q, M_TSEGQ);
267 q = nq;
268 }
269
270 /* Insert the new segment queue entry into place. */
271 te->tqe_m = m;
272 te->tqe_th = th;
273 te->tqe_len = *tlenp;
274
275 if (p == NULL) {
276 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
277 } else {
278 LIST_INSERT_AFTER(p, te, tqe_q);
279 }
280
281present:
282 /*
283 * Present data to user, advancing rcv_nxt through
284 * completed sequence space.
285 */
286 if (!TCPS_HAVEESTABLISHED(tp->t_state))
287 return (0);
288 q = LIST_FIRST(&tp->t_segq);
289 if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
290 return (0);
291 do {
292 tp->rcv_nxt += q->tqe_len;
293 flags = q->tqe_th->th_flags & TH_FIN;
294 nq = LIST_NEXT(q, tqe_q);
295 LIST_REMOVE(q, tqe_q);
296 if (so->so_state & SS_CANTRCVMORE)
297 m_freem(q->tqe_m);
298 else
|
299 sbappend(&so->so_rcv, q->tqe_m);
| 299 sbappendstream(&so->so_rcv, q->tqe_m);
|
300 FREE(q, M_TSEGQ);
301 q = nq;
302 } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
303 ND6_HINT(tp);
304 sorwakeup(so);
305 return (flags);
306}
307
308/*
309 * TCP input routine, follows pages 65-76 of the
310 * protocol specification dated September, 1981 very closely.
311 */
312#ifdef INET6
313int
314tcp6_input(mp, offp, proto)
315 struct mbuf **mp;
316 int *offp, proto;
317{
318 register struct mbuf *m = *mp;
319 struct in6_ifaddr *ia6;
320
321 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
322
323 /*
324 * draft-itojun-ipv6-tcp-to-anycast
325 * better place to put this in?
326 */
327 ia6 = ip6_getdstifaddr(m);
328 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
329 struct ip6_hdr *ip6;
330
331 ip6 = mtod(m, struct ip6_hdr *);
332 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
333 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
334 return IPPROTO_DONE;
335 }
336
337 tcp_input(m, *offp);
338 return IPPROTO_DONE;
339}
340#endif
341
342void
343tcp_input(m, off0)
344 register struct mbuf *m;
345 int off0;
346{
347 register struct tcphdr *th;
348 register struct ip *ip = NULL;
349 register struct ipovly *ipov;
350 register struct inpcb *inp = NULL;
351 u_char *optp = NULL;
352 int optlen = 0;
353 int len, tlen, off;
354 int drop_hdrlen;
355 register struct tcpcb *tp = 0;
356 register int thflags;
357 struct socket *so = 0;
358 int todrop, acked, ourfinisacked, needoutput = 0;
359 u_long tiwin;
360 struct tcpopt to; /* options in this segment */
361 struct rmxp_tao *taop; /* pointer to our TAO cache entry */
362 struct rmxp_tao tao_noncached; /* in case there's no cached entry */
363 int headlocked = 0;
364 struct sockaddr_in *next_hop = NULL;
365 int rstreason; /* For badport_bandlim accounting purposes */
366
367 struct ip6_hdr *ip6 = NULL;
368#ifdef INET6
369 int isipv6;
370#else
371 const int isipv6 = 0;
372#endif
373
374#ifdef TCPDEBUG
375 /*
376 * The size of tcp_saveipgen must be the size of the max ip header,
377 * now IPv6.
378 */
379 u_char tcp_saveipgen[40];
380 struct tcphdr tcp_savetcp;
381 short ostate = 0;
382#endif
383
384 /* Grab info from MT_TAG mbufs prepended to the chain. */
385 for (;m && m->m_type == MT_TAG; m = m->m_next) {
386 if (m->_m_tag_id == PACKET_TAG_IPFORWARD)
387 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data;
388 }
389#ifdef INET6
390 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
391#endif
392 bzero((char *)&to, sizeof(to));
393
394 tcpstat.tcps_rcvtotal++;
395
396 if (isipv6) {
397 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
398 ip6 = mtod(m, struct ip6_hdr *);
399 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
400 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
401 tcpstat.tcps_rcvbadsum++;
402 goto drop;
403 }
404 th = (struct tcphdr *)((caddr_t)ip6 + off0);
405
406 /*
407 * Be proactive about unspecified IPv6 address in source.
408 * As we use all-zero to indicate unbounded/unconnected pcb,
409 * unspecified IPv6 address can be used to confuse us.
410 *
411 * Note that packets with unspecified IPv6 destination is
412 * already dropped in ip6_input.
413 */
414 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
415 /* XXX stat */
416 goto drop;
417 }
418 } else {
419 /*
420 * Get IP and TCP header together in first mbuf.
421 * Note: IP leaves IP header in first mbuf.
422 */
423 if (off0 > sizeof (struct ip)) {
424 ip_stripoptions(m, (struct mbuf *)0);
425 off0 = sizeof(struct ip);
426 }
427 if (m->m_len < sizeof (struct tcpiphdr)) {
428 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) {
429 tcpstat.tcps_rcvshort++;
430 return;
431 }
432 }
433 ip = mtod(m, struct ip *);
434 ipov = (struct ipovly *)ip;
435 th = (struct tcphdr *)((caddr_t)ip + off0);
436 tlen = ip->ip_len;
437
438 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
439 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
440 th->th_sum = m->m_pkthdr.csum_data;
441 else
442 th->th_sum = in_pseudo(ip->ip_src.s_addr,
443 ip->ip_dst.s_addr,
444 htonl(m->m_pkthdr.csum_data +
445 ip->ip_len +
446 IPPROTO_TCP));
447 th->th_sum ^= 0xffff;
448#ifdef TCPDEBUG
449 ipov->ih_len = (u_short)tlen;
450 ipov->ih_len = htons(ipov->ih_len);
451#endif
452 } else {
453 /*
454 * Checksum extended TCP header and data.
455 */
456 len = sizeof (struct ip) + tlen;
457 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
458 ipov->ih_len = (u_short)tlen;
459 ipov->ih_len = htons(ipov->ih_len);
460 th->th_sum = in_cksum(m, len);
461 }
462 if (th->th_sum) {
463 tcpstat.tcps_rcvbadsum++;
464 goto drop;
465 }
466#ifdef INET6
467 /* Re-initialization for later version check */
468 ip->ip_v = IPVERSION;
469#endif
470 }
471
472 /*
473 * Check that TCP offset makes sense,
474 * pull out TCP options and adjust length. XXX
475 */
476 off = th->th_off << 2;
477 if (off < sizeof (struct tcphdr) || off > tlen) {
478 tcpstat.tcps_rcvbadoff++;
479 goto drop;
480 }
481 tlen -= off; /* tlen is used instead of ti->ti_len */
482 if (off > sizeof (struct tcphdr)) {
483 if (isipv6) {
484 IP6_EXTHDR_CHECK(m, off0, off, );
485 ip6 = mtod(m, struct ip6_hdr *);
486 th = (struct tcphdr *)((caddr_t)ip6 + off0);
487 } else {
488 if (m->m_len < sizeof(struct ip) + off) {
489 if ((m = m_pullup(m, sizeof (struct ip) + off))
490 == 0) {
491 tcpstat.tcps_rcvshort++;
492 return;
493 }
494 ip = mtod(m, struct ip *);
495 ipov = (struct ipovly *)ip;
496 th = (struct tcphdr *)((caddr_t)ip + off0);
497 }
498 }
499 optlen = off - sizeof (struct tcphdr);
500 optp = (u_char *)(th + 1);
501 }
502 thflags = th->th_flags;
503
504#ifdef TCP_DROP_SYNFIN
505 /*
506 * If the drop_synfin option is enabled, drop all packets with
507 * both the SYN and FIN bits set. This prevents e.g. nmap from
508 * identifying the TCP/IP stack.
509 *
510 * This is a violation of the TCP specification.
511 */
512 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
513 goto drop;
514#endif
515
516 /*
517 * Convert TCP protocol specific fields to host format.
518 */
519 th->th_seq = ntohl(th->th_seq);
520 th->th_ack = ntohl(th->th_ack);
521 th->th_win = ntohs(th->th_win);
522 th->th_urp = ntohs(th->th_urp);
523
524 /*
525 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
526 * until after ip6_savecontrol() is called and before other functions
527 * which don't want those proto headers.
528 * Because ip6_savecontrol() is going to parse the mbuf to
529 * search for data to be passed up to user-land, it wants mbuf
530 * parameters to be unchanged.
531 * XXX: the call of ip6_savecontrol() has been obsoleted based on
532 * latest version of the advanced API (20020110).
533 */
534 drop_hdrlen = off0 + off;
535
536 /*
537 * Locate pcb for segment.
538 */
539 INP_INFO_WLOCK(&tcbinfo);
540 headlocked = 1;
541findpcb:
542 /* IPFIREWALL_FORWARD section */
543 if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */
544 /*
545 * Transparently forwarded. Pretend to be the destination.
546 * already got one like this?
547 */
548 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport,
549 ip->ip_dst, th->th_dport,
550 0, m->m_pkthdr.rcvif);
551 if (!inp) {
552 /* It's new. Try find the ambushing socket. */
553 inp = in_pcblookup_hash(&tcbinfo,
554 ip->ip_src, th->th_sport,
555 next_hop->sin_addr,
556 next_hop->sin_port ?
557 ntohs(next_hop->sin_port) :
558 th->th_dport,
559 1, m->m_pkthdr.rcvif);
560 }
561 } else {
562 if (isipv6)
563 inp = in6_pcblookup_hash(&tcbinfo,
564 &ip6->ip6_src, th->th_sport,
565 &ip6->ip6_dst, th->th_dport,
566 1, m->m_pkthdr.rcvif);
567 else
568 inp = in_pcblookup_hash(&tcbinfo,
569 ip->ip_src, th->th_sport,
570 ip->ip_dst, th->th_dport,
571 1, m->m_pkthdr.rcvif);
572 }
573
574#ifdef IPSEC
575 if (isipv6) {
576 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) {
577 ipsec6stat.in_polvio++;
578 goto drop;
579 }
580 } else {
581 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) {
582 ipsecstat.in_polvio++;
583 goto drop;
584 }
585 }
586#endif
587#ifdef FAST_IPSEC
588 if (isipv6) {
589 if (inp != NULL && ipsec6_in_reject(m, inp)) {
590 goto drop;
591 }
592 } else
593 if (inp != NULL && ipsec4_in_reject(m, inp)) {
594 goto drop;
595 }
596#endif /*FAST_IPSEC*/
597
598 /*
599 * If the state is CLOSED (i.e., TCB does not exist) then
600 * all data in the incoming segment is discarded.
601 * If the TCB exists but is in CLOSED state, it is embryonic,
602 * but should either do a listen or a connect soon.
603 */
604 if (inp == NULL) {
605 if (log_in_vain) {
606#ifdef INET6
607 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
608#else
609 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"];
610#endif
611
612 if (isipv6) {
613 strcpy(dbuf, "[");
614 strcpy(sbuf, "[");
615 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
616 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
617 strcat(dbuf, "]");
618 strcat(sbuf, "]");
619 } else {
620 strcpy(dbuf, inet_ntoa(ip->ip_dst));
621 strcpy(sbuf, inet_ntoa(ip->ip_src));
622 }
623 switch (log_in_vain) {
624 case 1:
625 if ((thflags & TH_SYN) == 0)
626 break;
627 /* FALLTHROUGH */
628 case 2:
629 log(LOG_INFO,
630 "Connection attempt to TCP %s:%d "
631 "from %s:%d flags:0x%02x\n",
632 dbuf, ntohs(th->th_dport), sbuf,
633 ntohs(th->th_sport), thflags);
634 break;
635 default:
636 break;
637 }
638 }
639 if (blackhole) {
640 switch (blackhole) {
641 case 1:
642 if (thflags & TH_SYN)
643 goto drop;
644 break;
645 case 2:
646 goto drop;
647 default:
648 goto drop;
649 }
650 }
651 rstreason = BANDLIM_RST_CLOSEDPORT;
652 goto dropwithreset;
653 }
654 INP_LOCK(inp);
655 if (inp->inp_vflag & INP_TIMEWAIT) {
656 /*
657 * The only option of relevance is TOF_CC, and only if
658 * present in a SYN segment. See tcp_timewait().
659 */
660 if (thflags & TH_SYN)
661 tcp_dooptions(&to, optp, optlen, 1);
662 if (tcp_timewait((struct tcptw *)inp->inp_ppcb,
663 &to, th, m, tlen))
664 goto findpcb;
665 /*
666 * tcp_timewait unlocks inp.
667 */
668 INP_INFO_WUNLOCK(&tcbinfo);
669 return;
670 }
671 tp = intotcpcb(inp);
672 if (tp == 0) {
673 INP_UNLOCK(inp);
674 rstreason = BANDLIM_RST_CLOSEDPORT;
675 goto dropwithreset;
676 }
677 if (tp->t_state == TCPS_CLOSED)
678 goto drop;
679
680 /* Unscale the window into a 32-bit value. */
681 if ((thflags & TH_SYN) == 0)
682 tiwin = th->th_win << tp->snd_scale;
683 else
684 tiwin = th->th_win;
685
686 so = inp->inp_socket;
687#ifdef MAC
688 if (mac_check_socket_deliver(so, m))
689 goto drop;
690#endif
691#ifdef TCPDEBUG
692 if (so->so_options & SO_DEBUG) {
693 ostate = tp->t_state;
694 if (isipv6)
695 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
696 else
697 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
698 tcp_savetcp = *th;
699 }
700#endif
701 if (so->so_options & SO_ACCEPTCONN) {
702 struct in_conninfo inc;
703
704#ifdef INET6
705 inc.inc_isipv6 = isipv6;
706#endif
707 if (isipv6) {
708 inc.inc6_faddr = ip6->ip6_src;
709 inc.inc6_laddr = ip6->ip6_dst;
710 inc.inc6_route.ro_rt = NULL; /* XXX */
711 } else {
712 inc.inc_faddr = ip->ip_src;
713 inc.inc_laddr = ip->ip_dst;
714 inc.inc_route.ro_rt = NULL; /* XXX */
715 }
716 inc.inc_fport = th->th_sport;
717 inc.inc_lport = th->th_dport;
718
719 /*
720 * If the state is LISTEN then ignore segment if it contains
721 * a RST. If the segment contains an ACK then it is bad and
722 * send a RST. If it does not contain a SYN then it is not
723 * interesting; drop it.
724 *
725 * If the state is SYN_RECEIVED (syncache) and seg contains
726 * an ACK, but not for our SYN/ACK, send a RST. If the seg
727 * contains a RST, check the sequence number to see if it
728 * is a valid reset segment.
729 */
730 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
731 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
732 if (!syncache_expand(&inc, th, &so, m)) {
733 /*
734 * No syncache entry, or ACK was not
735 * for our SYN/ACK. Send a RST.
736 */
737 tcpstat.tcps_badsyn++;
738 rstreason = BANDLIM_RST_OPENPORT;
739 goto dropwithreset;
740 }
741 if (so == NULL) {
742 /*
743 * Could not complete 3-way handshake,
744 * connection is being closed down, and
745 * syncache will free mbuf.
746 */
747 INP_UNLOCK(inp);
748 INP_INFO_WUNLOCK(&tcbinfo);
749 return;
750 }
751 /*
752 * Socket is created in state SYN_RECEIVED.
753 * Continue processing segment.
754 */
755 INP_UNLOCK(inp);
756 inp = sotoinpcb(so);
757 INP_LOCK(inp);
758 tp = intotcpcb(inp);
759 /*
760 * This is what would have happened in
761 * tcp_output() when the SYN,ACK was sent.
762 */
763 tp->snd_up = tp->snd_una;
764 tp->snd_max = tp->snd_nxt = tp->iss + 1;
765 tp->last_ack_sent = tp->rcv_nxt;
766 /*
767 * RFC1323: The window in SYN & SYN/ACK
768 * segments is never scaled.
769 */
770 tp->snd_wnd = tiwin; /* unscaled */
771 goto after_listen;
772 }
773 if (thflags & TH_RST) {
774 syncache_chkrst(&inc, th);
775 goto drop;
776 }
777 if (thflags & TH_ACK) {
778 syncache_badack(&inc);
779 tcpstat.tcps_badsyn++;
780 rstreason = BANDLIM_RST_OPENPORT;
781 goto dropwithreset;
782 }
783 goto drop;
784 }
785
786 /*
787 * Segment's flags are (SYN) or (SYN|FIN).
788 */
789#ifdef INET6
790 /*
791 * If deprecated address is forbidden,
792 * we do not accept SYN to deprecated interface
793 * address to prevent any new inbound connection from
794 * getting established.
795 * When we do not accept SYN, we send a TCP RST,
796 * with deprecated source address (instead of dropping
797 * it). We compromise it as it is much better for peer
798 * to send a RST, and RST will be the final packet
799 * for the exchange.
800 *
801 * If we do not forbid deprecated addresses, we accept
802 * the SYN packet. RFC2462 does not suggest dropping
803 * SYN in this case.
804 * If we decipher RFC2462 5.5.4, it says like this:
805 * 1. use of deprecated addr with existing
806 * communication is okay - "SHOULD continue to be
807 * used"
808 * 2. use of it with new communication:
809 * (2a) "SHOULD NOT be used if alternate address
810 * with sufficient scope is available"
811 * (2b) nothing mentioned otherwise.
812 * Here we fall into (2b) case as we have no choice in
813 * our source address selection - we must obey the peer.
814 *
815 * The wording in RFC2462 is confusing, and there are
816 * multiple description text for deprecated address
817 * handling - worse, they are not exactly the same.
818 * I believe 5.5.4 is the best one, so we follow 5.5.4.
819 */
820 if (isipv6 && !ip6_use_deprecated) {
821 struct in6_ifaddr *ia6;
822
823 if ((ia6 = ip6_getdstifaddr(m)) &&
824 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
825 INP_UNLOCK(inp);
826 tp = NULL;
827 rstreason = BANDLIM_RST_OPENPORT;
828 goto dropwithreset;
829 }
830 }
831#endif
832 /*
833 * If it is from this socket, drop it, it must be forged.
834 * Don't bother responding if the destination was a broadcast.
835 */
836 if (th->th_dport == th->th_sport) {
837 if (isipv6) {
838 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
839 &ip6->ip6_src))
840 goto drop;
841 } else {
842 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
843 goto drop;
844 }
845 }
846 /*
847 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
848 *
849 * Note that it is quite possible to receive unicast
850 * link-layer packets with a broadcast IP address. Use
851 * in_broadcast() to find them.
852 */
853 if (m->m_flags & (M_BCAST|M_MCAST))
854 goto drop;
855 if (isipv6) {
856 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
857 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
858 goto drop;
859 } else {
860 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
861 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
862 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
863 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
864 goto drop;
865 }
866 /*
867 * SYN appears to be valid; create compressed TCP state
868 * for syncache, or perform t/tcp connection.
869 */
870 if (so->so_qlen <= so->so_qlimit) {
871#ifdef TCPDEBUG
872 if (so->so_options & SO_DEBUG)
873 tcp_trace(TA_INPUT, ostate, tp,
874 (void *)tcp_saveipgen, &tcp_savetcp, 0);
875#endif
876 tcp_dooptions(&to, optp, optlen, 1);
877 if (!syncache_add(&inc, &to, th, &so, m))
878 goto drop;
879 if (so == NULL) {
880 /*
881 * Entry added to syncache, mbuf used to
882 * send SYN,ACK packet.
883 */
884 KASSERT(headlocked, ("headlocked"));
885 INP_UNLOCK(inp);
886 INP_INFO_WUNLOCK(&tcbinfo);
887 return;
888 }
889 /*
890 * Segment passed TAO tests.
891 */
892 INP_UNLOCK(inp);
893 inp = sotoinpcb(so);
894 INP_LOCK(inp);
895 tp = intotcpcb(inp);
896 tp->snd_wnd = tiwin;
897 tp->t_starttime = ticks;
898 tp->t_state = TCPS_ESTABLISHED;
899
900 /*
901 * T/TCP logic:
902 * If there is a FIN or if there is data, then
903 * delay SYN,ACK(SYN) in the hope of piggy-backing
904 * it on a response segment. Otherwise must send
905 * ACK now in case the other side is slow starting.
906 */
907 if (thflags & TH_FIN || tlen != 0)
908 tp->t_flags |= (TF_DELACK | TF_NEEDSYN);
909 else
910 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
911 tcpstat.tcps_connects++;
912 soisconnected(so);
913 goto trimthenstep6;
914 }
915 goto drop;
916 }
917after_listen:
918
919/* XXX temp debugging */
920 /* should not happen - syncache should pick up these connections */
921 if (tp->t_state == TCPS_LISTEN)
922 panic("tcp_input: TCPS_LISTEN");
923
924 /*
925 * Segment received on connection.
926 * Reset idle time and keep-alive timer.
927 */
928 tp->t_rcvtime = ticks;
929 if (TCPS_HAVEESTABLISHED(tp->t_state))
930 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
931
932 /*
933 * Process options.
934 * XXX this is tradtitional behavior, may need to be cleaned up.
935 */
936 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN);
937 if (thflags & TH_SYN) {
938 if (to.to_flags & TOF_SCALE) {
939 tp->t_flags |= TF_RCVD_SCALE;
940 tp->requested_s_scale = to.to_requested_s_scale;
941 }
942 if (to.to_flags & TOF_TS) {
943 tp->t_flags |= TF_RCVD_TSTMP;
944 tp->ts_recent = to.to_tsval;
945 tp->ts_recent_age = ticks;
946 }
947 if (to.to_flags & (TOF_CC|TOF_CCNEW))
948 tp->t_flags |= TF_RCVD_CC;
949 if (to.to_flags & TOF_MSS)
950 tcp_mss(tp, to.to_mss);
951 }
952
953 /*
954 * Header prediction: check for the two common cases
955 * of a uni-directional data xfer. If the packet has
956 * no control flags, is in-sequence, the window didn't
957 * change and we're not retransmitting, it's a
958 * candidate. If the length is zero and the ack moved
959 * forward, we're the sender side of the xfer. Just
960 * free the data acked & wake any higher level process
961 * that was blocked waiting for space. If the length
962 * is non-zero and the ack didn't move, we're the
963 * receiver side. If we're getting packets in-order
964 * (the reassembly queue is empty), add the data to
965 * the socket buffer and note that we need a delayed ack.
966 * Make sure that the hidden state-flags are also off.
967 * Since we check for TCPS_ESTABLISHED above, it can only
968 * be TH_NEEDSYN.
969 */
970 if (tp->t_state == TCPS_ESTABLISHED &&
971 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
972 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
973 ((to.to_flags & TOF_TS) == 0 ||
974 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
975 /*
976 * Using the CC option is compulsory if once started:
977 * the segment is OK if no T/TCP was negotiated or
978 * if the segment has a CC option equal to CCrecv
979 */
980 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
981 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) &&
982 th->th_seq == tp->rcv_nxt &&
983 tiwin && tiwin == tp->snd_wnd &&
984 tp->snd_nxt == tp->snd_max) {
985
986 /*
987 * If last ACK falls within this segment's sequence numbers,
988 * record the timestamp.
989 * NOTE that the test is modified according to the latest
990 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
991 */
992 if ((to.to_flags & TOF_TS) != 0 &&
993 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
994 tp->ts_recent_age = ticks;
995 tp->ts_recent = to.to_tsval;
996 }
997
998 if (tlen == 0) {
999 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1000 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1001 tp->snd_cwnd >= tp->snd_wnd &&
1002 ((!tcp_do_newreno &&
1003 tp->t_dupacks < tcprexmtthresh) ||
1004 (tcp_do_newreno && !IN_FASTRECOVERY(tp)))) {
1005 KASSERT(headlocked, ("headlocked"));
1006 INP_INFO_WUNLOCK(&tcbinfo);
1007 /*
1008 * this is a pure ack for outstanding data.
1009 */
1010 ++tcpstat.tcps_predack;
1011 /*
1012 * "bad retransmit" recovery
1013 */
1014 if (tp->t_rxtshift == 1 &&
1015 ticks < tp->t_badrxtwin) {
1016 ++tcpstat.tcps_sndrexmitbad;
1017 tp->snd_cwnd = tp->snd_cwnd_prev;
1018 tp->snd_ssthresh =
1019 tp->snd_ssthresh_prev;
1020 tp->snd_recover = tp->snd_recover_prev;
1021 if (tp->t_flags & TF_WASFRECOVERY)
1022 ENTER_FASTRECOVERY(tp);
1023 tp->snd_nxt = tp->snd_max;
1024 tp->t_badrxtwin = 0;
1025 }
1026
1027 /*
1028 * Recalculate the transmit timer / rtt.
1029 *
1030 * Some boxes send broken timestamp replies
1031 * during the SYN+ACK phase, ignore
1032 * timestamps of 0 or we could calculate a
1033 * huge RTT and blow up the retransmit timer.
1034 */
1035 if ((to.to_flags & TOF_TS) != 0 &&
1036 to.to_tsecr) {
1037 tcp_xmit_timer(tp,
1038 ticks - to.to_tsecr + 1);
1039 } else if (tp->t_rtttime &&
1040 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1041 tcp_xmit_timer(tp,
1042 ticks - tp->t_rtttime);
1043 }
1044 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1045 acked = th->th_ack - tp->snd_una;
1046 tcpstat.tcps_rcvackpack++;
1047 tcpstat.tcps_rcvackbyte += acked;
1048 sbdrop(&so->so_snd, acked);
1049 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1050 SEQ_LEQ(th->th_ack, tp->snd_recover))
1051 tp->snd_recover = th->th_ack - 1;
1052 tp->snd_una = th->th_ack;
1053 /*
1054 * pull snd_wl2 up to prevent seq wrap relative
1055 * to th_ack.
1056 */
1057 tp->snd_wl2 = th->th_ack;
1058 tp->t_dupacks = 0;
1059 m_freem(m);
1060 ND6_HINT(tp); /* some progress has been done */
1061
1062 /*
1063 * If all outstanding data are acked, stop
1064 * retransmit timer, otherwise restart timer
1065 * using current (possibly backed-off) value.
1066 * If process is waiting for space,
1067 * wakeup/selwakeup/signal. If data
1068 * are ready to send, let tcp_output
1069 * decide between more output or persist.
1070
1071#ifdef TCPDEBUG
1072 if (so->so_options & SO_DEBUG)
1073 tcp_trace(TA_INPUT, ostate, tp,
1074 (void *)tcp_saveipgen,
1075 &tcp_savetcp, 0);
1076#endif
1077 */
1078 if (tp->snd_una == tp->snd_max)
1079 callout_stop(tp->tt_rexmt);
1080 else if (!callout_active(tp->tt_persist))
1081 callout_reset(tp->tt_rexmt,
1082 tp->t_rxtcur,
1083 tcp_timer_rexmt, tp);
1084
1085 sowwakeup(so);
1086 if (so->so_snd.sb_cc)
1087 (void) tcp_output(tp);
1088 goto check_delack;
1089 }
1090 } else if (th->th_ack == tp->snd_una &&
1091 LIST_EMPTY(&tp->t_segq) &&
1092 tlen <= sbspace(&so->so_rcv)) {
1093 KASSERT(headlocked, ("headlocked"));
1094 INP_INFO_WUNLOCK(&tcbinfo);
1095 /*
1096 * this is a pure, in-sequence data packet
1097 * with nothing on the reassembly queue and
1098 * we have enough buffer space to take it.
1099 */
1100 ++tcpstat.tcps_preddat;
1101 tp->rcv_nxt += tlen;
1102 /*
1103 * Pull snd_wl1 up to prevent seq wrap relative to
1104 * th_seq.
1105 */
1106 tp->snd_wl1 = th->th_seq;
1107 /*
1108 * Pull rcv_up up to prevent seq wrap relative to
1109 * rcv_nxt.
1110 */
1111 tp->rcv_up = tp->rcv_nxt;
1112 tcpstat.tcps_rcvpack++;
1113 tcpstat.tcps_rcvbyte += tlen;
1114 ND6_HINT(tp); /* some progress has been done */
1115 /*
1116#ifdef TCPDEBUG
1117 if (so->so_options & SO_DEBUG)
1118 tcp_trace(TA_INPUT, ostate, tp,
1119 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1120#endif
1121 * Add data to socket buffer.
1122 */
1123 if (so->so_state & SS_CANTRCVMORE) {
1124 m_freem(m);
1125 } else {
1126 m_adj(m, drop_hdrlen); /* delayed header drop */
| 300 FREE(q, M_TSEGQ);
301 q = nq;
302 } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
303 ND6_HINT(tp);
304 sorwakeup(so);
305 return (flags);
306}
307
308/*
309 * TCP input routine, follows pages 65-76 of the
310 * protocol specification dated September, 1981 very closely.
311 */
312#ifdef INET6
313int
314tcp6_input(mp, offp, proto)
315 struct mbuf **mp;
316 int *offp, proto;
317{
318 register struct mbuf *m = *mp;
319 struct in6_ifaddr *ia6;
320
321 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
322
323 /*
324 * draft-itojun-ipv6-tcp-to-anycast
325 * better place to put this in?
326 */
327 ia6 = ip6_getdstifaddr(m);
328 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
329 struct ip6_hdr *ip6;
330
331 ip6 = mtod(m, struct ip6_hdr *);
332 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
333 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
334 return IPPROTO_DONE;
335 }
336
337 tcp_input(m, *offp);
338 return IPPROTO_DONE;
339}
340#endif
341
342void
343tcp_input(m, off0)
344 register struct mbuf *m;
345 int off0;
346{
347 register struct tcphdr *th;
348 register struct ip *ip = NULL;
349 register struct ipovly *ipov;
350 register struct inpcb *inp = NULL;
351 u_char *optp = NULL;
352 int optlen = 0;
353 int len, tlen, off;
354 int drop_hdrlen;
355 register struct tcpcb *tp = 0;
356 register int thflags;
357 struct socket *so = 0;
358 int todrop, acked, ourfinisacked, needoutput = 0;
359 u_long tiwin;
360 struct tcpopt to; /* options in this segment */
361 struct rmxp_tao *taop; /* pointer to our TAO cache entry */
362 struct rmxp_tao tao_noncached; /* in case there's no cached entry */
363 int headlocked = 0;
364 struct sockaddr_in *next_hop = NULL;
365 int rstreason; /* For badport_bandlim accounting purposes */
366
367 struct ip6_hdr *ip6 = NULL;
368#ifdef INET6
369 int isipv6;
370#else
371 const int isipv6 = 0;
372#endif
373
374#ifdef TCPDEBUG
375 /*
376 * The size of tcp_saveipgen must be the size of the max ip header,
377 * now IPv6.
378 */
379 u_char tcp_saveipgen[40];
380 struct tcphdr tcp_savetcp;
381 short ostate = 0;
382#endif
383
384 /* Grab info from MT_TAG mbufs prepended to the chain. */
385 for (;m && m->m_type == MT_TAG; m = m->m_next) {
386 if (m->_m_tag_id == PACKET_TAG_IPFORWARD)
387 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data;
388 }
389#ifdef INET6
390 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
391#endif
392 bzero((char *)&to, sizeof(to));
393
394 tcpstat.tcps_rcvtotal++;
395
396 if (isipv6) {
397 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
398 ip6 = mtod(m, struct ip6_hdr *);
399 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
400 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
401 tcpstat.tcps_rcvbadsum++;
402 goto drop;
403 }
404 th = (struct tcphdr *)((caddr_t)ip6 + off0);
405
406 /*
407 * Be proactive about unspecified IPv6 address in source.
408 * As we use all-zero to indicate unbounded/unconnected pcb,
409 * unspecified IPv6 address can be used to confuse us.
410 *
411 * Note that packets with unspecified IPv6 destination is
412 * already dropped in ip6_input.
413 */
414 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
415 /* XXX stat */
416 goto drop;
417 }
418 } else {
419 /*
420 * Get IP and TCP header together in first mbuf.
421 * Note: IP leaves IP header in first mbuf.
422 */
423 if (off0 > sizeof (struct ip)) {
424 ip_stripoptions(m, (struct mbuf *)0);
425 off0 = sizeof(struct ip);
426 }
427 if (m->m_len < sizeof (struct tcpiphdr)) {
428 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) {
429 tcpstat.tcps_rcvshort++;
430 return;
431 }
432 }
433 ip = mtod(m, struct ip *);
434 ipov = (struct ipovly *)ip;
435 th = (struct tcphdr *)((caddr_t)ip + off0);
436 tlen = ip->ip_len;
437
438 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
439 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
440 th->th_sum = m->m_pkthdr.csum_data;
441 else
442 th->th_sum = in_pseudo(ip->ip_src.s_addr,
443 ip->ip_dst.s_addr,
444 htonl(m->m_pkthdr.csum_data +
445 ip->ip_len +
446 IPPROTO_TCP));
447 th->th_sum ^= 0xffff;
448#ifdef TCPDEBUG
449 ipov->ih_len = (u_short)tlen;
450 ipov->ih_len = htons(ipov->ih_len);
451#endif
452 } else {
453 /*
454 * Checksum extended TCP header and data.
455 */
456 len = sizeof (struct ip) + tlen;
457 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
458 ipov->ih_len = (u_short)tlen;
459 ipov->ih_len = htons(ipov->ih_len);
460 th->th_sum = in_cksum(m, len);
461 }
462 if (th->th_sum) {
463 tcpstat.tcps_rcvbadsum++;
464 goto drop;
465 }
466#ifdef INET6
467 /* Re-initialization for later version check */
468 ip->ip_v = IPVERSION;
469#endif
470 }
471
472 /*
473 * Check that TCP offset makes sense,
474 * pull out TCP options and adjust length. XXX
475 */
476 off = th->th_off << 2;
477 if (off < sizeof (struct tcphdr) || off > tlen) {
478 tcpstat.tcps_rcvbadoff++;
479 goto drop;
480 }
481 tlen -= off; /* tlen is used instead of ti->ti_len */
482 if (off > sizeof (struct tcphdr)) {
483 if (isipv6) {
484 IP6_EXTHDR_CHECK(m, off0, off, );
485 ip6 = mtod(m, struct ip6_hdr *);
486 th = (struct tcphdr *)((caddr_t)ip6 + off0);
487 } else {
488 if (m->m_len < sizeof(struct ip) + off) {
489 if ((m = m_pullup(m, sizeof (struct ip) + off))
490 == 0) {
491 tcpstat.tcps_rcvshort++;
492 return;
493 }
494 ip = mtod(m, struct ip *);
495 ipov = (struct ipovly *)ip;
496 th = (struct tcphdr *)((caddr_t)ip + off0);
497 }
498 }
499 optlen = off - sizeof (struct tcphdr);
500 optp = (u_char *)(th + 1);
501 }
502 thflags = th->th_flags;
503
504#ifdef TCP_DROP_SYNFIN
505 /*
506 * If the drop_synfin option is enabled, drop all packets with
507 * both the SYN and FIN bits set. This prevents e.g. nmap from
508 * identifying the TCP/IP stack.
509 *
510 * This is a violation of the TCP specification.
511 */
512 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
513 goto drop;
514#endif
515
516 /*
517 * Convert TCP protocol specific fields to host format.
518 */
519 th->th_seq = ntohl(th->th_seq);
520 th->th_ack = ntohl(th->th_ack);
521 th->th_win = ntohs(th->th_win);
522 th->th_urp = ntohs(th->th_urp);
523
524 /*
525 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
526 * until after ip6_savecontrol() is called and before other functions
527 * which don't want those proto headers.
528 * Because ip6_savecontrol() is going to parse the mbuf to
529 * search for data to be passed up to user-land, it wants mbuf
530 * parameters to be unchanged.
531 * XXX: the call of ip6_savecontrol() has been obsoleted based on
532 * latest version of the advanced API (20020110).
533 */
534 drop_hdrlen = off0 + off;
535
536 /*
537 * Locate pcb for segment.
538 */
539 INP_INFO_WLOCK(&tcbinfo);
540 headlocked = 1;
541findpcb:
542 /* IPFIREWALL_FORWARD section */
543 if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */
544 /*
545 * Transparently forwarded. Pretend to be the destination.
546 * already got one like this?
547 */
548 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport,
549 ip->ip_dst, th->th_dport,
550 0, m->m_pkthdr.rcvif);
551 if (!inp) {
552 /* It's new. Try find the ambushing socket. */
553 inp = in_pcblookup_hash(&tcbinfo,
554 ip->ip_src, th->th_sport,
555 next_hop->sin_addr,
556 next_hop->sin_port ?
557 ntohs(next_hop->sin_port) :
558 th->th_dport,
559 1, m->m_pkthdr.rcvif);
560 }
561 } else {
562 if (isipv6)
563 inp = in6_pcblookup_hash(&tcbinfo,
564 &ip6->ip6_src, th->th_sport,
565 &ip6->ip6_dst, th->th_dport,
566 1, m->m_pkthdr.rcvif);
567 else
568 inp = in_pcblookup_hash(&tcbinfo,
569 ip->ip_src, th->th_sport,
570 ip->ip_dst, th->th_dport,
571 1, m->m_pkthdr.rcvif);
572 }
573
574#ifdef IPSEC
575 if (isipv6) {
576 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) {
577 ipsec6stat.in_polvio++;
578 goto drop;
579 }
580 } else {
581 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) {
582 ipsecstat.in_polvio++;
583 goto drop;
584 }
585 }
586#endif
587#ifdef FAST_IPSEC
588 if (isipv6) {
589 if (inp != NULL && ipsec6_in_reject(m, inp)) {
590 goto drop;
591 }
592 } else
593 if (inp != NULL && ipsec4_in_reject(m, inp)) {
594 goto drop;
595 }
596#endif /*FAST_IPSEC*/
597
598 /*
599 * If the state is CLOSED (i.e., TCB does not exist) then
600 * all data in the incoming segment is discarded.
601 * If the TCB exists but is in CLOSED state, it is embryonic,
602 * but should either do a listen or a connect soon.
603 */
604 if (inp == NULL) {
605 if (log_in_vain) {
606#ifdef INET6
607 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
608#else
609 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"];
610#endif
611
612 if (isipv6) {
613 strcpy(dbuf, "[");
614 strcpy(sbuf, "[");
615 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
616 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
617 strcat(dbuf, "]");
618 strcat(sbuf, "]");
619 } else {
620 strcpy(dbuf, inet_ntoa(ip->ip_dst));
621 strcpy(sbuf, inet_ntoa(ip->ip_src));
622 }
623 switch (log_in_vain) {
624 case 1:
625 if ((thflags & TH_SYN) == 0)
626 break;
627 /* FALLTHROUGH */
628 case 2:
629 log(LOG_INFO,
630 "Connection attempt to TCP %s:%d "
631 "from %s:%d flags:0x%02x\n",
632 dbuf, ntohs(th->th_dport), sbuf,
633 ntohs(th->th_sport), thflags);
634 break;
635 default:
636 break;
637 }
638 }
639 if (blackhole) {
640 switch (blackhole) {
641 case 1:
642 if (thflags & TH_SYN)
643 goto drop;
644 break;
645 case 2:
646 goto drop;
647 default:
648 goto drop;
649 }
650 }
651 rstreason = BANDLIM_RST_CLOSEDPORT;
652 goto dropwithreset;
653 }
654 INP_LOCK(inp);
655 if (inp->inp_vflag & INP_TIMEWAIT) {
656 /*
657 * The only option of relevance is TOF_CC, and only if
658 * present in a SYN segment. See tcp_timewait().
659 */
660 if (thflags & TH_SYN)
661 tcp_dooptions(&to, optp, optlen, 1);
662 if (tcp_timewait((struct tcptw *)inp->inp_ppcb,
663 &to, th, m, tlen))
664 goto findpcb;
665 /*
666 * tcp_timewait unlocks inp.
667 */
668 INP_INFO_WUNLOCK(&tcbinfo);
669 return;
670 }
671 tp = intotcpcb(inp);
672 if (tp == 0) {
673 INP_UNLOCK(inp);
674 rstreason = BANDLIM_RST_CLOSEDPORT;
675 goto dropwithreset;
676 }
677 if (tp->t_state == TCPS_CLOSED)
678 goto drop;
679
680 /* Unscale the window into a 32-bit value. */
681 if ((thflags & TH_SYN) == 0)
682 tiwin = th->th_win << tp->snd_scale;
683 else
684 tiwin = th->th_win;
685
686 so = inp->inp_socket;
687#ifdef MAC
688 if (mac_check_socket_deliver(so, m))
689 goto drop;
690#endif
691#ifdef TCPDEBUG
692 if (so->so_options & SO_DEBUG) {
693 ostate = tp->t_state;
694 if (isipv6)
695 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
696 else
697 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
698 tcp_savetcp = *th;
699 }
700#endif
701 if (so->so_options & SO_ACCEPTCONN) {
702 struct in_conninfo inc;
703
704#ifdef INET6
705 inc.inc_isipv6 = isipv6;
706#endif
707 if (isipv6) {
708 inc.inc6_faddr = ip6->ip6_src;
709 inc.inc6_laddr = ip6->ip6_dst;
710 inc.inc6_route.ro_rt = NULL; /* XXX */
711 } else {
712 inc.inc_faddr = ip->ip_src;
713 inc.inc_laddr = ip->ip_dst;
714 inc.inc_route.ro_rt = NULL; /* XXX */
715 }
716 inc.inc_fport = th->th_sport;
717 inc.inc_lport = th->th_dport;
718
719 /*
720 * If the state is LISTEN then ignore segment if it contains
721 * a RST. If the segment contains an ACK then it is bad and
722 * send a RST. If it does not contain a SYN then it is not
723 * interesting; drop it.
724 *
725 * If the state is SYN_RECEIVED (syncache) and seg contains
726 * an ACK, but not for our SYN/ACK, send a RST. If the seg
727 * contains a RST, check the sequence number to see if it
728 * is a valid reset segment.
729 */
730 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
731 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
732 if (!syncache_expand(&inc, th, &so, m)) {
733 /*
734 * No syncache entry, or ACK was not
735 * for our SYN/ACK. Send a RST.
736 */
737 tcpstat.tcps_badsyn++;
738 rstreason = BANDLIM_RST_OPENPORT;
739 goto dropwithreset;
740 }
741 if (so == NULL) {
742 /*
743 * Could not complete 3-way handshake,
744 * connection is being closed down, and
745 * syncache will free mbuf.
746 */
747 INP_UNLOCK(inp);
748 INP_INFO_WUNLOCK(&tcbinfo);
749 return;
750 }
751 /*
752 * Socket is created in state SYN_RECEIVED.
753 * Continue processing segment.
754 */
755 INP_UNLOCK(inp);
756 inp = sotoinpcb(so);
757 INP_LOCK(inp);
758 tp = intotcpcb(inp);
759 /*
760 * This is what would have happened in
761 * tcp_output() when the SYN,ACK was sent.
762 */
763 tp->snd_up = tp->snd_una;
764 tp->snd_max = tp->snd_nxt = tp->iss + 1;
765 tp->last_ack_sent = tp->rcv_nxt;
766 /*
767 * RFC1323: The window in SYN & SYN/ACK
768 * segments is never scaled.
769 */
770 tp->snd_wnd = tiwin; /* unscaled */
771 goto after_listen;
772 }
773 if (thflags & TH_RST) {
774 syncache_chkrst(&inc, th);
775 goto drop;
776 }
777 if (thflags & TH_ACK) {
778 syncache_badack(&inc);
779 tcpstat.tcps_badsyn++;
780 rstreason = BANDLIM_RST_OPENPORT;
781 goto dropwithreset;
782 }
783 goto drop;
784 }
785
786 /*
787 * Segment's flags are (SYN) or (SYN|FIN).
788 */
789#ifdef INET6
790 /*
791 * If deprecated address is forbidden,
792 * we do not accept SYN to deprecated interface
793 * address to prevent any new inbound connection from
794 * getting established.
795 * When we do not accept SYN, we send a TCP RST,
796 * with deprecated source address (instead of dropping
797 * it). We compromise it as it is much better for peer
798 * to send a RST, and RST will be the final packet
799 * for the exchange.
800 *
801 * If we do not forbid deprecated addresses, we accept
802 * the SYN packet. RFC2462 does not suggest dropping
803 * SYN in this case.
804 * If we decipher RFC2462 5.5.4, it says like this:
805 * 1. use of deprecated addr with existing
806 * communication is okay - "SHOULD continue to be
807 * used"
808 * 2. use of it with new communication:
809 * (2a) "SHOULD NOT be used if alternate address
810 * with sufficient scope is available"
811 * (2b) nothing mentioned otherwise.
812 * Here we fall into (2b) case as we have no choice in
813 * our source address selection - we must obey the peer.
814 *
815 * The wording in RFC2462 is confusing, and there are
816 * multiple description text for deprecated address
817 * handling - worse, they are not exactly the same.
818 * I believe 5.5.4 is the best one, so we follow 5.5.4.
819 */
820 if (isipv6 && !ip6_use_deprecated) {
821 struct in6_ifaddr *ia6;
822
823 if ((ia6 = ip6_getdstifaddr(m)) &&
824 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
825 INP_UNLOCK(inp);
826 tp = NULL;
827 rstreason = BANDLIM_RST_OPENPORT;
828 goto dropwithreset;
829 }
830 }
831#endif
832 /*
833 * If it is from this socket, drop it, it must be forged.
834 * Don't bother responding if the destination was a broadcast.
835 */
836 if (th->th_dport == th->th_sport) {
837 if (isipv6) {
838 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
839 &ip6->ip6_src))
840 goto drop;
841 } else {
842 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
843 goto drop;
844 }
845 }
846 /*
847 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
848 *
849 * Note that it is quite possible to receive unicast
850 * link-layer packets with a broadcast IP address. Use
851 * in_broadcast() to find them.
852 */
853 if (m->m_flags & (M_BCAST|M_MCAST))
854 goto drop;
855 if (isipv6) {
856 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
857 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
858 goto drop;
859 } else {
860 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
861 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
862 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
863 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
864 goto drop;
865 }
866 /*
867 * SYN appears to be valid; create compressed TCP state
868 * for syncache, or perform t/tcp connection.
869 */
870 if (so->so_qlen <= so->so_qlimit) {
871#ifdef TCPDEBUG
872 if (so->so_options & SO_DEBUG)
873 tcp_trace(TA_INPUT, ostate, tp,
874 (void *)tcp_saveipgen, &tcp_savetcp, 0);
875#endif
876 tcp_dooptions(&to, optp, optlen, 1);
877 if (!syncache_add(&inc, &to, th, &so, m))
878 goto drop;
879 if (so == NULL) {
880 /*
881 * Entry added to syncache, mbuf used to
882 * send SYN,ACK packet.
883 */
884 KASSERT(headlocked, ("headlocked"));
885 INP_UNLOCK(inp);
886 INP_INFO_WUNLOCK(&tcbinfo);
887 return;
888 }
889 /*
890 * Segment passed TAO tests.
891 */
892 INP_UNLOCK(inp);
893 inp = sotoinpcb(so);
894 INP_LOCK(inp);
895 tp = intotcpcb(inp);
896 tp->snd_wnd = tiwin;
897 tp->t_starttime = ticks;
898 tp->t_state = TCPS_ESTABLISHED;
899
900 /*
901 * T/TCP logic:
902 * If there is a FIN or if there is data, then
903 * delay SYN,ACK(SYN) in the hope of piggy-backing
904 * it on a response segment. Otherwise must send
905 * ACK now in case the other side is slow starting.
906 */
907 if (thflags & TH_FIN || tlen != 0)
908 tp->t_flags |= (TF_DELACK | TF_NEEDSYN);
909 else
910 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
911 tcpstat.tcps_connects++;
912 soisconnected(so);
913 goto trimthenstep6;
914 }
915 goto drop;
916 }
917after_listen:
918
919/* XXX temp debugging */
920 /* should not happen - syncache should pick up these connections */
921 if (tp->t_state == TCPS_LISTEN)
922 panic("tcp_input: TCPS_LISTEN");
923
924 /*
925 * Segment received on connection.
926 * Reset idle time and keep-alive timer.
927 */
928 tp->t_rcvtime = ticks;
929 if (TCPS_HAVEESTABLISHED(tp->t_state))
930 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
931
932 /*
933 * Process options.
934 * XXX this is tradtitional behavior, may need to be cleaned up.
935 */
936 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN);
937 if (thflags & TH_SYN) {
938 if (to.to_flags & TOF_SCALE) {
939 tp->t_flags |= TF_RCVD_SCALE;
940 tp->requested_s_scale = to.to_requested_s_scale;
941 }
942 if (to.to_flags & TOF_TS) {
943 tp->t_flags |= TF_RCVD_TSTMP;
944 tp->ts_recent = to.to_tsval;
945 tp->ts_recent_age = ticks;
946 }
947 if (to.to_flags & (TOF_CC|TOF_CCNEW))
948 tp->t_flags |= TF_RCVD_CC;
949 if (to.to_flags & TOF_MSS)
950 tcp_mss(tp, to.to_mss);
951 }
952
953 /*
954 * Header prediction: check for the two common cases
955 * of a uni-directional data xfer. If the packet has
956 * no control flags, is in-sequence, the window didn't
957 * change and we're not retransmitting, it's a
958 * candidate. If the length is zero and the ack moved
959 * forward, we're the sender side of the xfer. Just
960 * free the data acked & wake any higher level process
961 * that was blocked waiting for space. If the length
962 * is non-zero and the ack didn't move, we're the
963 * receiver side. If we're getting packets in-order
964 * (the reassembly queue is empty), add the data to
965 * the socket buffer and note that we need a delayed ack.
966 * Make sure that the hidden state-flags are also off.
967 * Since we check for TCPS_ESTABLISHED above, it can only
968 * be TH_NEEDSYN.
969 */
970 if (tp->t_state == TCPS_ESTABLISHED &&
971 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
972 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
973 ((to.to_flags & TOF_TS) == 0 ||
974 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
975 /*
976 * Using the CC option is compulsory if once started:
977 * the segment is OK if no T/TCP was negotiated or
978 * if the segment has a CC option equal to CCrecv
979 */
980 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
981 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) &&
982 th->th_seq == tp->rcv_nxt &&
983 tiwin && tiwin == tp->snd_wnd &&
984 tp->snd_nxt == tp->snd_max) {
985
986 /*
987 * If last ACK falls within this segment's sequence numbers,
988 * record the timestamp.
989 * NOTE that the test is modified according to the latest
990 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
991 */
992 if ((to.to_flags & TOF_TS) != 0 &&
993 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
994 tp->ts_recent_age = ticks;
995 tp->ts_recent = to.to_tsval;
996 }
997
998 if (tlen == 0) {
999 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1000 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1001 tp->snd_cwnd >= tp->snd_wnd &&
1002 ((!tcp_do_newreno &&
1003 tp->t_dupacks < tcprexmtthresh) ||
1004 (tcp_do_newreno && !IN_FASTRECOVERY(tp)))) {
1005 KASSERT(headlocked, ("headlocked"));
1006 INP_INFO_WUNLOCK(&tcbinfo);
1007 /*
1008 * this is a pure ack for outstanding data.
1009 */
1010 ++tcpstat.tcps_predack;
1011 /*
1012 * "bad retransmit" recovery
1013 */
1014 if (tp->t_rxtshift == 1 &&
1015 ticks < tp->t_badrxtwin) {
1016 ++tcpstat.tcps_sndrexmitbad;
1017 tp->snd_cwnd = tp->snd_cwnd_prev;
1018 tp->snd_ssthresh =
1019 tp->snd_ssthresh_prev;
1020 tp->snd_recover = tp->snd_recover_prev;
1021 if (tp->t_flags & TF_WASFRECOVERY)
1022 ENTER_FASTRECOVERY(tp);
1023 tp->snd_nxt = tp->snd_max;
1024 tp->t_badrxtwin = 0;
1025 }
1026
1027 /*
1028 * Recalculate the transmit timer / rtt.
1029 *
1030 * Some boxes send broken timestamp replies
1031 * during the SYN+ACK phase, ignore
1032 * timestamps of 0 or we could calculate a
1033 * huge RTT and blow up the retransmit timer.
1034 */
1035 if ((to.to_flags & TOF_TS) != 0 &&
1036 to.to_tsecr) {
1037 tcp_xmit_timer(tp,
1038 ticks - to.to_tsecr + 1);
1039 } else if (tp->t_rtttime &&
1040 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1041 tcp_xmit_timer(tp,
1042 ticks - tp->t_rtttime);
1043 }
1044 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1045 acked = th->th_ack - tp->snd_una;
1046 tcpstat.tcps_rcvackpack++;
1047 tcpstat.tcps_rcvackbyte += acked;
1048 sbdrop(&so->so_snd, acked);
1049 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1050 SEQ_LEQ(th->th_ack, tp->snd_recover))
1051 tp->snd_recover = th->th_ack - 1;
1052 tp->snd_una = th->th_ack;
1053 /*
1054 * pull snd_wl2 up to prevent seq wrap relative
1055 * to th_ack.
1056 */
1057 tp->snd_wl2 = th->th_ack;
1058 tp->t_dupacks = 0;
1059 m_freem(m);
1060 ND6_HINT(tp); /* some progress has been done */
1061
1062 /*
1063 * If all outstanding data are acked, stop
1064 * retransmit timer, otherwise restart timer
1065 * using current (possibly backed-off) value.
1066 * If process is waiting for space,
1067 * wakeup/selwakeup/signal. If data
1068 * are ready to send, let tcp_output
1069 * decide between more output or persist.
1070
1071#ifdef TCPDEBUG
1072 if (so->so_options & SO_DEBUG)
1073 tcp_trace(TA_INPUT, ostate, tp,
1074 (void *)tcp_saveipgen,
1075 &tcp_savetcp, 0);
1076#endif
1077 */
1078 if (tp->snd_una == tp->snd_max)
1079 callout_stop(tp->tt_rexmt);
1080 else if (!callout_active(tp->tt_persist))
1081 callout_reset(tp->tt_rexmt,
1082 tp->t_rxtcur,
1083 tcp_timer_rexmt, tp);
1084
1085 sowwakeup(so);
1086 if (so->so_snd.sb_cc)
1087 (void) tcp_output(tp);
1088 goto check_delack;
1089 }
1090 } else if (th->th_ack == tp->snd_una &&
1091 LIST_EMPTY(&tp->t_segq) &&
1092 tlen <= sbspace(&so->so_rcv)) {
1093 KASSERT(headlocked, ("headlocked"));
1094 INP_INFO_WUNLOCK(&tcbinfo);
1095 /*
1096 * this is a pure, in-sequence data packet
1097 * with nothing on the reassembly queue and
1098 * we have enough buffer space to take it.
1099 */
1100 ++tcpstat.tcps_preddat;
1101 tp->rcv_nxt += tlen;
1102 /*
1103 * Pull snd_wl1 up to prevent seq wrap relative to
1104 * th_seq.
1105 */
1106 tp->snd_wl1 = th->th_seq;
1107 /*
1108 * Pull rcv_up up to prevent seq wrap relative to
1109 * rcv_nxt.
1110 */
1111 tp->rcv_up = tp->rcv_nxt;
1112 tcpstat.tcps_rcvpack++;
1113 tcpstat.tcps_rcvbyte += tlen;
1114 ND6_HINT(tp); /* some progress has been done */
1115 /*
1116#ifdef TCPDEBUG
1117 if (so->so_options & SO_DEBUG)
1118 tcp_trace(TA_INPUT, ostate, tp,
1119 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1120#endif
1121 * Add data to socket buffer.
1122 */
1123 if (so->so_state & SS_CANTRCVMORE) {
1124 m_freem(m);
1125 } else {
1126 m_adj(m, drop_hdrlen); /* delayed header drop */
|
1127 sbappend(&so->so_rcv, m);
| 1127 sbappendstream(&so->so_rcv, m);
|
1128 }
1129 sorwakeup(so);
1130 if (DELAY_ACK(tp)) {
1131 tp->t_flags |= TF_DELACK;
1132 } else {
1133 tp->t_flags |= TF_ACKNOW;
1134 tcp_output(tp);
1135 }
1136 goto check_delack;
1137 }
1138 }
1139
1140 /*
1141 * Calculate amount of space in receive window,
1142 * and then do TCP input processing.
1143 * Receive window is amount of space in rcv queue,
1144 * but not less than advertised window.
1145 */
1146 { int win;
1147
1148 win = sbspace(&so->so_rcv);
1149 if (win < 0)
1150 win = 0;
1151 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1152 }
1153
1154 switch (tp->t_state) {
1155
1156 /*
1157 * If the state is SYN_RECEIVED:
1158 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1159 */
1160 case TCPS_SYN_RECEIVED:
1161 if ((thflags & TH_ACK) &&
1162 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1163 SEQ_GT(th->th_ack, tp->snd_max))) {
1164 rstreason = BANDLIM_RST_OPENPORT;
1165 goto dropwithreset;
1166 }
1167 break;
1168
1169 /*
1170 * If the state is SYN_SENT:
1171 * if seg contains an ACK, but not for our SYN, drop the input.
1172 * if seg contains a RST, then drop the connection.
1173 * if seg does not contain SYN, then drop it.
1174 * Otherwise this is an acceptable SYN segment
1175 * initialize tp->rcv_nxt and tp->irs
1176 * if seg contains ack then advance tp->snd_una
1177 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1178 * arrange for segment to be acked (eventually)
1179 * continue processing rest of data/controls, beginning with URG
1180 */
1181 case TCPS_SYN_SENT:
1182 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) {
1183 taop = &tao_noncached;
1184 bzero(taop, sizeof(*taop));
1185 }
1186
1187 if ((thflags & TH_ACK) &&
1188 (SEQ_LEQ(th->th_ack, tp->iss) ||
1189 SEQ_GT(th->th_ack, tp->snd_max))) {
1190 /*
1191 * If we have a cached CCsent for the remote host,
1192 * hence we haven't just crashed and restarted,
1193 * do not send a RST. This may be a retransmission
1194 * from the other side after our earlier ACK was lost.
1195 * Our new SYN, when it arrives, will serve as the
1196 * needed ACK.
1197 */
1198 if (taop->tao_ccsent != 0)
1199 goto drop;
1200 else {
1201 rstreason = BANDLIM_UNLIMITED;
1202 goto dropwithreset;
1203 }
1204 }
1205 if (thflags & TH_RST) {
1206 if (thflags & TH_ACK)
1207 tp = tcp_drop(tp, ECONNREFUSED);
1208 goto drop;
1209 }
1210 if ((thflags & TH_SYN) == 0)
1211 goto drop;
1212 tp->snd_wnd = th->th_win; /* initial send window */
1213 tp->cc_recv = to.to_cc; /* foreign CC */
1214
1215 tp->irs = th->th_seq;
1216 tcp_rcvseqinit(tp);
1217 if (thflags & TH_ACK) {
1218 /*
1219 * Our SYN was acked. If segment contains CC.ECHO
1220 * option, check it to make sure this segment really
1221 * matches our SYN. If not, just drop it as old
1222 * duplicate, but send an RST if we're still playing
1223 * by the old rules. If no CC.ECHO option, make sure
1224 * we don't get fooled into using T/TCP.
1225 */
1226 if (to.to_flags & TOF_CCECHO) {
1227 if (tp->cc_send != to.to_ccecho) {
1228 if (taop->tao_ccsent != 0)
1229 goto drop;
1230 else {
1231 rstreason = BANDLIM_UNLIMITED;
1232 goto dropwithreset;
1233 }
1234 }
1235 } else
1236 tp->t_flags &= ~TF_RCVD_CC;
1237 tcpstat.tcps_connects++;
1238 soisconnected(so);
1239#ifdef MAC
1240 mac_set_socket_peer_from_mbuf(m, so);
1241#endif
1242 /* Do window scaling on this connection? */
1243 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1244 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1245 tp->snd_scale = tp->requested_s_scale;
1246 tp->rcv_scale = tp->request_r_scale;
1247 }
1248 /* Segment is acceptable, update cache if undefined. */
1249 if (taop->tao_ccsent == 0)
1250 taop->tao_ccsent = to.to_ccecho;
1251
1252 tp->rcv_adv += tp->rcv_wnd;
1253 tp->snd_una++; /* SYN is acked */
1254 /*
1255 * If there's data, delay ACK; if there's also a FIN
1256 * ACKNOW will be turned on later.
1257 */
1258 if (DELAY_ACK(tp) && tlen != 0)
1259 callout_reset(tp->tt_delack, tcp_delacktime,
1260 tcp_timer_delack, tp);
1261 else
1262 tp->t_flags |= TF_ACKNOW;
1263 /*
1264 * Received <SYN,ACK> in SYN_SENT[*] state.
1265 * Transitions:
1266 * SYN_SENT --> ESTABLISHED
1267 * SYN_SENT* --> FIN_WAIT_1
1268 */
1269 tp->t_starttime = ticks;
1270 if (tp->t_flags & TF_NEEDFIN) {
1271 tp->t_state = TCPS_FIN_WAIT_1;
1272 tp->t_flags &= ~TF_NEEDFIN;
1273 thflags &= ~TH_SYN;
1274 } else {
1275 tp->t_state = TCPS_ESTABLISHED;
1276 callout_reset(tp->tt_keep, tcp_keepidle,
1277 tcp_timer_keep, tp);
1278 }
1279 } else {
1280 /*
1281 * Received initial SYN in SYN-SENT[*] state =>
1282 * simultaneous open. If segment contains CC option
1283 * and there is a cached CC, apply TAO test.
1284 * If it succeeds, connection is * half-synchronized.
1285 * Otherwise, do 3-way handshake:
1286 * SYN-SENT -> SYN-RECEIVED
1287 * SYN-SENT* -> SYN-RECEIVED*
1288 * If there was no CC option, clear cached CC value.
1289 */
1290 tp->t_flags |= TF_ACKNOW;
1291 callout_stop(tp->tt_rexmt);
1292 if (to.to_flags & TOF_CC) {
1293 if (taop->tao_cc != 0 &&
1294 CC_GT(to.to_cc, taop->tao_cc)) {
1295 /*
1296 * update cache and make transition:
1297 * SYN-SENT -> ESTABLISHED*
1298 * SYN-SENT* -> FIN-WAIT-1*
1299 */
1300 taop->tao_cc = to.to_cc;
1301 tp->t_starttime = ticks;
1302 if (tp->t_flags & TF_NEEDFIN) {
1303 tp->t_state = TCPS_FIN_WAIT_1;
1304 tp->t_flags &= ~TF_NEEDFIN;
1305 } else {
1306 tp->t_state = TCPS_ESTABLISHED;
1307 callout_reset(tp->tt_keep,
1308 tcp_keepidle,
1309 tcp_timer_keep,
1310 tp);
1311 }
1312 tp->t_flags |= TF_NEEDSYN;
1313 } else
1314 tp->t_state = TCPS_SYN_RECEIVED;
1315 } else {
1316 /* CC.NEW or no option => invalidate cache */
1317 taop->tao_cc = 0;
1318 tp->t_state = TCPS_SYN_RECEIVED;
1319 }
1320 }
1321
1322trimthenstep6:
1323 /*
1324 * Advance th->th_seq to correspond to first data byte.
1325 * If data, trim to stay within window,
1326 * dropping FIN if necessary.
1327 */
1328 th->th_seq++;
1329 if (tlen > tp->rcv_wnd) {
1330 todrop = tlen - tp->rcv_wnd;
1331 m_adj(m, -todrop);
1332 tlen = tp->rcv_wnd;
1333 thflags &= ~TH_FIN;
1334 tcpstat.tcps_rcvpackafterwin++;
1335 tcpstat.tcps_rcvbyteafterwin += todrop;
1336 }
1337 tp->snd_wl1 = th->th_seq - 1;
1338 tp->rcv_up = th->th_seq;
1339 /*
1340 * Client side of transaction: already sent SYN and data.
1341 * If the remote host used T/TCP to validate the SYN,
1342 * our data will be ACK'd; if so, enter normal data segment
1343 * processing in the middle of step 5, ack processing.
1344 * Otherwise, goto step 6.
1345 */
1346 if (thflags & TH_ACK)
1347 goto process_ACK;
1348
1349 goto step6;
1350
1351 /*
1352 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1353 * if segment contains a SYN and CC [not CC.NEW] option:
1354 * if state == TIME_WAIT and connection duration > MSL,
1355 * drop packet and send RST;
1356 *
1357 * if SEG.CC > CCrecv then is new SYN, and can implicitly
1358 * ack the FIN (and data) in retransmission queue.
1359 * Complete close and delete TCPCB. Then reprocess
1360 * segment, hoping to find new TCPCB in LISTEN state;
1361 *
1362 * else must be old SYN; drop it.
1363 * else do normal processing.
1364 */
1365 case TCPS_LAST_ACK:
1366 case TCPS_CLOSING:
1367 case TCPS_TIME_WAIT:
1368 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1369 if ((thflags & TH_SYN) &&
1370 (to.to_flags & TOF_CC) && tp->cc_recv != 0) {
1371 if (tp->t_state == TCPS_TIME_WAIT &&
1372 (ticks - tp->t_starttime) > tcp_msl) {
1373 rstreason = BANDLIM_UNLIMITED;
1374 goto dropwithreset;
1375 }
1376 if (CC_GT(to.to_cc, tp->cc_recv)) {
1377 tp = tcp_close(tp);
1378 goto findpcb;
1379 }
1380 else
1381 goto drop;
1382 }
1383 break; /* continue normal processing */
1384 }
1385
1386 /*
1387 * States other than LISTEN or SYN_SENT.
1388 * First check the RST flag and sequence number since reset segments
1389 * are exempt from the timestamp and connection count tests. This
1390 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1391 * below which allowed reset segments in half the sequence space
1392 * to fall though and be processed (which gives forged reset
1393 * segments with a random sequence number a 50 percent chance of
1394 * killing a connection).
1395 * Then check timestamp, if present.
1396 * Then check the connection count, if present.
1397 * Then check that at least some bytes of segment are within
1398 * receive window. If segment begins before rcv_nxt,
1399 * drop leading data (and SYN); if nothing left, just ack.
1400 *
1401 *
1402 * If the RST bit is set, check the sequence number to see
1403 * if this is a valid reset segment.
1404 * RFC 793 page 37:
1405 * In all states except SYN-SENT, all reset (RST) segments
1406 * are validated by checking their SEQ-fields. A reset is
1407 * valid if its sequence number is in the window.
1408 * Note: this does not take into account delayed ACKs, so
1409 * we should test against last_ack_sent instead of rcv_nxt.
1410 * The sequence number in the reset segment is normally an
1411 * echo of our outgoing acknowlegement numbers, but some hosts
1412 * send a reset with the sequence number at the rightmost edge
1413 * of our receive window, and we have to handle this case.
1414 * If we have multiple segments in flight, the intial reset
1415 * segment sequence numbers will be to the left of last_ack_sent,
1416 * but they will eventually catch up.
1417 * In any case, it never made sense to trim reset segments to
1418 * fit the receive window since RFC 1122 says:
1419 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1420 *
1421 * A TCP SHOULD allow a received RST segment to include data.
1422 *
1423 * DISCUSSION
1424 * It has been suggested that a RST segment could contain
1425 * ASCII text that encoded and explained the cause of the
1426 * RST. No standard has yet been established for such
1427 * data.
1428 *
1429 * If the reset segment passes the sequence number test examine
1430 * the state:
1431 * SYN_RECEIVED STATE:
1432 * If passive open, return to LISTEN state.
1433 * If active open, inform user that connection was refused.
1434 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1435 * Inform user that connection was reset, and close tcb.
1436 * CLOSING, LAST_ACK STATES:
1437 * Close the tcb.
1438 * TIME_WAIT STATE:
1439 * Drop the segment - see Stevens, vol. 2, p. 964 and
1440 * RFC 1337.
1441 */
1442 if (thflags & TH_RST) {
1443 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1444 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1445 switch (tp->t_state) {
1446
1447 case TCPS_SYN_RECEIVED:
1448 so->so_error = ECONNREFUSED;
1449 goto close;
1450
1451 case TCPS_ESTABLISHED:
1452 case TCPS_FIN_WAIT_1:
1453 case TCPS_FIN_WAIT_2:
1454 case TCPS_CLOSE_WAIT:
1455 so->so_error = ECONNRESET;
1456 close:
1457 tp->t_state = TCPS_CLOSED;
1458 tcpstat.tcps_drops++;
1459 tp = tcp_close(tp);
1460 break;
1461
1462 case TCPS_CLOSING:
1463 case TCPS_LAST_ACK:
1464 tp = tcp_close(tp);
1465 break;
1466
1467 case TCPS_TIME_WAIT:
1468 KASSERT(tp->t_state != TCPS_TIME_WAIT,
1469 ("timewait"));
1470 break;
1471 }
1472 }
1473 goto drop;
1474 }
1475
1476 /*
1477 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1478 * and it's less than ts_recent, drop it.
1479 */
1480 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
1481 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1482
1483 /* Check to see if ts_recent is over 24 days old. */
1484 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1485 /*
1486 * Invalidate ts_recent. If this segment updates
1487 * ts_recent, the age will be reset later and ts_recent
1488 * will get a valid value. If it does not, setting
1489 * ts_recent to zero will at least satisfy the
1490 * requirement that zero be placed in the timestamp
1491 * echo reply when ts_recent isn't valid. The
1492 * age isn't reset until we get a valid ts_recent
1493 * because we don't want out-of-order segments to be
1494 * dropped when ts_recent is old.
1495 */
1496 tp->ts_recent = 0;
1497 } else {
1498 tcpstat.tcps_rcvduppack++;
1499 tcpstat.tcps_rcvdupbyte += tlen;
1500 tcpstat.tcps_pawsdrop++;
1501 if (tlen)
1502 goto dropafterack;
1503 goto drop;
1504 }
1505 }
1506
1507 /*
1508 * T/TCP mechanism
1509 * If T/TCP was negotiated and the segment doesn't have CC,
1510 * or if its CC is wrong then drop the segment.
1511 * RST segments do not have to comply with this.
1512 */
1513 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
1514 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc))
1515 goto dropafterack;
1516
1517 /*
1518 * In the SYN-RECEIVED state, validate that the packet belongs to
1519 * this connection before trimming the data to fit the receive
1520 * window. Check the sequence number versus IRS since we know
1521 * the sequence numbers haven't wrapped. This is a partial fix
1522 * for the "LAND" DoS attack.
1523 */
1524 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1525 rstreason = BANDLIM_RST_OPENPORT;
1526 goto dropwithreset;
1527 }
1528
1529 todrop = tp->rcv_nxt - th->th_seq;
1530 if (todrop > 0) {
1531 if (thflags & TH_SYN) {
1532 thflags &= ~TH_SYN;
1533 th->th_seq++;
1534 if (th->th_urp > 1)
1535 th->th_urp--;
1536 else
1537 thflags &= ~TH_URG;
1538 todrop--;
1539 }
1540 /*
1541 * Following if statement from Stevens, vol. 2, p. 960.
1542 */
1543 if (todrop > tlen
1544 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
1545 /*
1546 * Any valid FIN must be to the left of the window.
1547 * At this point the FIN must be a duplicate or out
1548 * of sequence; drop it.
1549 */
1550 thflags &= ~TH_FIN;
1551
1552 /*
1553 * Send an ACK to resynchronize and drop any data.
1554 * But keep on processing for RST or ACK.
1555 */
1556 tp->t_flags |= TF_ACKNOW;
1557 todrop = tlen;
1558 tcpstat.tcps_rcvduppack++;
1559 tcpstat.tcps_rcvdupbyte += todrop;
1560 } else {
1561 tcpstat.tcps_rcvpartduppack++;
1562 tcpstat.tcps_rcvpartdupbyte += todrop;
1563 }
1564 drop_hdrlen += todrop; /* drop from the top afterwards */
1565 th->th_seq += todrop;
1566 tlen -= todrop;
1567 if (th->th_urp > todrop)
1568 th->th_urp -= todrop;
1569 else {
1570 thflags &= ~TH_URG;
1571 th->th_urp = 0;
1572 }
1573 }
1574
1575 /*
1576 * If new data are received on a connection after the
1577 * user processes are gone, then RST the other end.
1578 */
1579 if ((so->so_state & SS_NOFDREF) &&
1580 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1581 tp = tcp_close(tp);
1582 tcpstat.tcps_rcvafterclose++;
1583 rstreason = BANDLIM_UNLIMITED;
1584 goto dropwithreset;
1585 }
1586
1587 /*
1588 * If segment ends after window, drop trailing data
1589 * (and PUSH and FIN); if nothing left, just ACK.
1590 */
1591 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd);
1592 if (todrop > 0) {
1593 tcpstat.tcps_rcvpackafterwin++;
1594 if (todrop >= tlen) {
1595 tcpstat.tcps_rcvbyteafterwin += tlen;
1596 /*
1597 * If a new connection request is received
1598 * while in TIME_WAIT, drop the old connection
1599 * and start over if the sequence numbers
1600 * are above the previous ones.
1601 */
1602 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1603 if (thflags & TH_SYN &&
1604 tp->t_state == TCPS_TIME_WAIT &&
1605 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1606 tp = tcp_close(tp);
1607 goto findpcb;
1608 }
1609 /*
1610 * If window is closed can only take segments at
1611 * window edge, and have to drop data and PUSH from
1612 * incoming segments. Continue processing, but
1613 * remember to ack. Otherwise, drop segment
1614 * and ack.
1615 */
1616 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1617 tp->t_flags |= TF_ACKNOW;
1618 tcpstat.tcps_rcvwinprobe++;
1619 } else
1620 goto dropafterack;
1621 } else
1622 tcpstat.tcps_rcvbyteafterwin += todrop;
1623 m_adj(m, -todrop);
1624 tlen -= todrop;
1625 thflags &= ~(TH_PUSH|TH_FIN);
1626 }
1627
1628 /*
1629 * If last ACK falls within this segment's sequence numbers,
1630 * record its timestamp.
1631 * NOTE that the test is modified according to the latest
1632 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1633 */
1634 if ((to.to_flags & TOF_TS) != 0 &&
1635 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1636 tp->ts_recent_age = ticks;
1637 tp->ts_recent = to.to_tsval;
1638 }
1639
1640 /*
1641 * If a SYN is in the window, then this is an
1642 * error and we send an RST and drop the connection.
1643 */
1644 if (thflags & TH_SYN) {
1645 tp = tcp_drop(tp, ECONNRESET);
1646 rstreason = BANDLIM_UNLIMITED;
1647 goto dropwithreset;
1648 }
1649
1650 /*
1651 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1652 * flag is on (half-synchronized state), then queue data for
1653 * later processing; else drop segment and return.
1654 */
1655 if ((thflags & TH_ACK) == 0) {
1656 if (tp->t_state == TCPS_SYN_RECEIVED ||
1657 (tp->t_flags & TF_NEEDSYN))
1658 goto step6;
1659 else
1660 goto drop;
1661 }
1662
1663 /*
1664 * Ack processing.
1665 */
1666 switch (tp->t_state) {
1667
1668 /*
1669 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
1670 * ESTABLISHED state and continue processing.
1671 * The ACK was checked above.
1672 */
1673 case TCPS_SYN_RECEIVED:
1674
1675 tcpstat.tcps_connects++;
1676 soisconnected(so);
1677 /* Do window scaling? */
1678 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1679 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1680 tp->snd_scale = tp->requested_s_scale;
1681 tp->rcv_scale = tp->request_r_scale;
1682 }
1683 /*
1684 * Upon successful completion of 3-way handshake,
1685 * update cache.CC if it was undefined, pass any queued
1686 * data to the user, and advance state appropriately.
1687 */
1688 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL &&
1689 taop->tao_cc == 0)
1690 taop->tao_cc = tp->cc_recv;
1691
1692 /*
1693 * Make transitions:
1694 * SYN-RECEIVED -> ESTABLISHED
1695 * SYN-RECEIVED* -> FIN-WAIT-1
1696 */
1697 tp->t_starttime = ticks;
1698 if (tp->t_flags & TF_NEEDFIN) {
1699 tp->t_state = TCPS_FIN_WAIT_1;
1700 tp->t_flags &= ~TF_NEEDFIN;
1701 } else {
1702 tp->t_state = TCPS_ESTABLISHED;
1703 callout_reset(tp->tt_keep, tcp_keepidle,
1704 tcp_timer_keep, tp);
1705 }
1706 /*
1707 * If segment contains data or ACK, will call tcp_reass()
1708 * later; if not, do so now to pass queued data to user.
1709 */
1710 if (tlen == 0 && (thflags & TH_FIN) == 0)
1711 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
1712 (struct mbuf *)0);
1713 tp->snd_wl1 = th->th_seq - 1;
1714 /* FALLTHROUGH */
1715
1716 /*
1717 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1718 * ACKs. If the ack is in the range
1719 * tp->snd_una < th->th_ack <= tp->snd_max
1720 * then advance tp->snd_una to th->th_ack and drop
1721 * data from the retransmission queue. If this ACK reflects
1722 * more up to date window information we update our window information.
1723 */
1724 case TCPS_ESTABLISHED:
1725 case TCPS_FIN_WAIT_1:
1726 case TCPS_FIN_WAIT_2:
1727 case TCPS_CLOSE_WAIT:
1728 case TCPS_CLOSING:
1729 case TCPS_LAST_ACK:
1730 case TCPS_TIME_WAIT:
1731 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1732 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
1733 if (tlen == 0 && tiwin == tp->snd_wnd) {
1734 tcpstat.tcps_rcvdupack++;
1735 /*
1736 * If we have outstanding data (other than
1737 * a window probe), this is a completely
1738 * duplicate ack (ie, window info didn't
1739 * change), the ack is the biggest we've
1740 * seen and we've seen exactly our rexmt
1741 * threshhold of them, assume a packet
1742 * has been dropped and retransmit it.
1743 * Kludge snd_nxt & the congestion
1744 * window so we send only this one
1745 * packet.
1746 *
1747 * We know we're losing at the current
1748 * window size so do congestion avoidance
1749 * (set ssthresh to half the current window
1750 * and pull our congestion window back to
1751 * the new ssthresh).
1752 *
1753 * Dup acks mean that packets have left the
1754 * network (they're now cached at the receiver)
1755 * so bump cwnd by the amount in the receiver
1756 * to keep a constant cwnd packets in the
1757 * network.
1758 */
1759 if (!callout_active(tp->tt_rexmt) ||
1760 th->th_ack != tp->snd_una)
1761 tp->t_dupacks = 0;
1762 else if (++tp->t_dupacks > tcprexmtthresh ||
1763 (tcp_do_newreno &&
1764 IN_FASTRECOVERY(tp))) {
1765 tp->snd_cwnd += tp->t_maxseg;
1766 (void) tcp_output(tp);
1767 goto drop;
1768 } else if (tp->t_dupacks == tcprexmtthresh) {
1769 tcp_seq onxt = tp->snd_nxt;
1770 u_int win;
1771 if (tcp_do_newreno &&
1772 SEQ_LEQ(th->th_ack,
1773 tp->snd_recover)) {
1774 tp->t_dupacks = 0;
1775 break;
1776 }
1777 win = min(tp->snd_wnd, tp->snd_cwnd) /
1778 2 / tp->t_maxseg;
1779 if (win < 2)
1780 win = 2;
1781 tp->snd_ssthresh = win * tp->t_maxseg;
1782 ENTER_FASTRECOVERY(tp);
1783 tp->snd_recover = tp->snd_max;
1784 callout_stop(tp->tt_rexmt);
1785 tp->t_rtttime = 0;
1786 tp->snd_nxt = th->th_ack;
1787 tp->snd_cwnd = tp->t_maxseg;
1788 (void) tcp_output(tp);
1789 KASSERT(tp->snd_limited <= 2,
1790 ("tp->snd_limited too big"));
1791 tp->snd_cwnd = tp->snd_ssthresh +
1792 tp->t_maxseg *
1793 (tp->t_dupacks - tp->snd_limited);
1794 if (SEQ_GT(onxt, tp->snd_nxt))
1795 tp->snd_nxt = onxt;
1796 goto drop;
1797 } else if (tcp_do_rfc3042) {
1798 u_long oldcwnd = tp->snd_cwnd;
1799 tcp_seq oldsndmax = tp->snd_max;
1800 u_int sent;
1801 KASSERT(tp->t_dupacks == 1 ||
1802 tp->t_dupacks == 2,
1803 ("dupacks not 1 or 2"));
1804 if (tp->t_dupacks == 1) {
1805 tp->snd_limited = 0;
1806 tp->snd_cwnd += tp->t_maxseg;
1807 } else {
1808 tp->snd_cwnd +=
1809 tp->t_maxseg * 2;
1810 }
1811 (void) tcp_output(tp);
1812 sent = tp->snd_max - oldsndmax;
1813 if (sent > tp->t_maxseg) {
1814 KASSERT(tp->snd_limited == 0 &&
1815 tp->t_dupacks == 2,
1816 ("sent too much"));
1817 tp->snd_limited = 2;
1818 } else if (sent > 0)
1819 ++tp->snd_limited;
1820 tp->snd_cwnd = oldcwnd;
1821 goto drop;
1822 }
1823 } else
1824 tp->t_dupacks = 0;
1825 break;
1826 }
1827
1828 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
1829
1830 /*
1831 * If the congestion window was inflated to account
1832 * for the other side's cached packets, retract it.
1833 */
1834 if (tcp_do_newreno) {
1835 if (IN_FASTRECOVERY(tp)) {
1836 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
1837 tcp_newreno_partial_ack(tp, th);
1838 } else {
1839 /*
1840 * Window inflation should have left us
1841 * with approximately snd_ssthresh
1842 * outstanding data.
1843 * But in case we would be inclined to
1844 * send a burst, better to do it via
1845 * the slow start mechanism.
1846 */
1847 if (SEQ_GT(th->th_ack +
1848 tp->snd_ssthresh,
1849 tp->snd_max))
1850 tp->snd_cwnd = tp->snd_max -
1851 th->th_ack +
1852 tp->t_maxseg;
1853 else
1854 tp->snd_cwnd = tp->snd_ssthresh;
1855 }
1856 }
1857 } else {
1858 if (tp->t_dupacks >= tcprexmtthresh &&
1859 tp->snd_cwnd > tp->snd_ssthresh)
1860 tp->snd_cwnd = tp->snd_ssthresh;
1861 }
1862 tp->t_dupacks = 0;
1863 if (SEQ_GT(th->th_ack, tp->snd_max)) {
1864 tcpstat.tcps_rcvacktoomuch++;
1865 goto dropafterack;
1866 }
1867 /*
1868 * If we reach this point, ACK is not a duplicate,
1869 * i.e., it ACKs something we sent.
1870 */
1871 if (tp->t_flags & TF_NEEDSYN) {
1872 /*
1873 * T/TCP: Connection was half-synchronized, and our
1874 * SYN has been ACK'd (so connection is now fully
1875 * synchronized). Go to non-starred state,
1876 * increment snd_una for ACK of SYN, and check if
1877 * we can do window scaling.
1878 */
1879 tp->t_flags &= ~TF_NEEDSYN;
1880 tp->snd_una++;
1881 /* Do window scaling? */
1882 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1883 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1884 tp->snd_scale = tp->requested_s_scale;
1885 tp->rcv_scale = tp->request_r_scale;
1886 }
1887 }
1888
1889process_ACK:
1890 acked = th->th_ack - tp->snd_una;
1891 tcpstat.tcps_rcvackpack++;
1892 tcpstat.tcps_rcvackbyte += acked;
1893
1894 /*
1895 * If we just performed our first retransmit, and the ACK
1896 * arrives within our recovery window, then it was a mistake
1897 * to do the retransmit in the first place. Recover our
1898 * original cwnd and ssthresh, and proceed to transmit where
1899 * we left off.
1900 */
1901 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
1902 ++tcpstat.tcps_sndrexmitbad;
1903 tp->snd_cwnd = tp->snd_cwnd_prev;
1904 tp->snd_ssthresh = tp->snd_ssthresh_prev;
1905 tp->snd_recover = tp->snd_recover_prev;
1906 if (tp->t_flags & TF_WASFRECOVERY)
1907 ENTER_FASTRECOVERY(tp);
1908 tp->snd_nxt = tp->snd_max;
1909 tp->t_badrxtwin = 0; /* XXX probably not required */
1910 }
1911
1912 /*
1913 * If we have a timestamp reply, update smoothed
1914 * round trip time. If no timestamp is present but
1915 * transmit timer is running and timed sequence
1916 * number was acked, update smoothed round trip time.
1917 * Since we now have an rtt measurement, cancel the
1918 * timer backoff (cf., Phil Karn's retransmit alg.).
1919 * Recompute the initial retransmit timer.
1920 *
1921 * Some boxes send broken timestamp replies
1922 * during the SYN+ACK phase, ignore
1923 * timestamps of 0 or we could calculate a
1924 * huge RTT and blow up the retransmit timer.
1925 */
1926 if ((to.to_flags & TOF_TS) != 0 &&
1927 to.to_tsecr) {
1928 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
1929 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
1930 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
1931 }
1932 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1933
1934 /*
1935 * If all outstanding data is acked, stop retransmit
1936 * timer and remember to restart (more output or persist).
1937 * If there is more data to be acked, restart retransmit
1938 * timer, using current (possibly backed-off) value.
1939 */
1940 if (th->th_ack == tp->snd_max) {
1941 callout_stop(tp->tt_rexmt);
1942 needoutput = 1;
1943 } else if (!callout_active(tp->tt_persist))
1944 callout_reset(tp->tt_rexmt, tp->t_rxtcur,
1945 tcp_timer_rexmt, tp);
1946
1947 /*
1948 * If no data (only SYN) was ACK'd,
1949 * skip rest of ACK processing.
1950 */
1951 if (acked == 0)
1952 goto step6;
1953
1954 /*
1955 * When new data is acked, open the congestion window.
1956 * If the window gives us less than ssthresh packets
1957 * in flight, open exponentially (maxseg per packet).
1958 * Otherwise open linearly: maxseg per window
1959 * (maxseg^2 / cwnd per packet).
1960 */
1961 if (!tcp_do_newreno || !IN_FASTRECOVERY(tp)) {
1962 register u_int cw = tp->snd_cwnd;
1963 register u_int incr = tp->t_maxseg;
1964 if (cw > tp->snd_ssthresh)
1965 incr = incr * incr / cw;
1966 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
1967 }
1968 if (acked > so->so_snd.sb_cc) {
1969 tp->snd_wnd -= so->so_snd.sb_cc;
1970 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
1971 ourfinisacked = 1;
1972 } else {
1973 sbdrop(&so->so_snd, acked);
1974 tp->snd_wnd -= acked;
1975 ourfinisacked = 0;
1976 }
1977 sowwakeup(so);
1978 /* detect una wraparound */
1979 if (tcp_do_newreno && !IN_FASTRECOVERY(tp) &&
1980 SEQ_GT(tp->snd_una, tp->snd_recover) &&
1981 SEQ_LEQ(th->th_ack, tp->snd_recover))
1982 tp->snd_recover = th->th_ack - 1;
1983 if (tcp_do_newreno && IN_FASTRECOVERY(tp) &&
1984 SEQ_GEQ(th->th_ack, tp->snd_recover))
1985 EXIT_FASTRECOVERY(tp);
1986 tp->snd_una = th->th_ack;
1987 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
1988 tp->snd_nxt = tp->snd_una;
1989
1990 switch (tp->t_state) {
1991
1992 /*
1993 * In FIN_WAIT_1 STATE in addition to the processing
1994 * for the ESTABLISHED state if our FIN is now acknowledged
1995 * then enter FIN_WAIT_2.
1996 */
1997 case TCPS_FIN_WAIT_1:
1998 if (ourfinisacked) {
1999 /*
2000 * If we can't receive any more
2001 * data, then closing user can proceed.
2002 * Starting the timer is contrary to the
2003 * specification, but if we don't get a FIN
2004 * we'll hang forever.
2005 */
2006 /* XXXjl
2007 * we should release the tp also, and use a
2008 * compressed state.
2009 */
2010 if (so->so_state & SS_CANTRCVMORE) {
2011 soisdisconnected(so);
2012 callout_reset(tp->tt_2msl, tcp_maxidle,
2013 tcp_timer_2msl, tp);
2014 }
2015 tp->t_state = TCPS_FIN_WAIT_2;
2016 }
2017 break;
2018
2019 /*
2020 * In CLOSING STATE in addition to the processing for
2021 * the ESTABLISHED state if the ACK acknowledges our FIN
2022 * then enter the TIME-WAIT state, otherwise ignore
2023 * the segment.
2024 */
2025 case TCPS_CLOSING:
2026 if (ourfinisacked) {
2027 KASSERT(headlocked, ("headlocked"));
2028 tcp_twstart(tp);
2029 INP_INFO_WUNLOCK(&tcbinfo);
2030 m_freem(m);
2031 return;
2032 }
2033 break;
2034
2035 /*
2036 * In LAST_ACK, we may still be waiting for data to drain
2037 * and/or to be acked, as well as for the ack of our FIN.
2038 * If our FIN is now acknowledged, delete the TCB,
2039 * enter the closed state and return.
2040 */
2041 case TCPS_LAST_ACK:
2042 if (ourfinisacked) {
2043 tp = tcp_close(tp);
2044 goto drop;
2045 }
2046 break;
2047
2048 /*
2049 * In TIME_WAIT state the only thing that should arrive
2050 * is a retransmission of the remote FIN. Acknowledge
2051 * it and restart the finack timer.
2052 */
2053 case TCPS_TIME_WAIT:
2054 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
2055 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2056 tcp_timer_2msl, tp);
2057 goto dropafterack;
2058 }
2059 }
2060
2061step6:
2062 /*
2063 * Update window information.
2064 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2065 */
2066 if ((thflags & TH_ACK) &&
2067 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2068 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2069 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2070 /* keep track of pure window updates */
2071 if (tlen == 0 &&
2072 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2073 tcpstat.tcps_rcvwinupd++;
2074 tp->snd_wnd = tiwin;
2075 tp->snd_wl1 = th->th_seq;
2076 tp->snd_wl2 = th->th_ack;
2077 if (tp->snd_wnd > tp->max_sndwnd)
2078 tp->max_sndwnd = tp->snd_wnd;
2079 needoutput = 1;
2080 }
2081
2082 /*
2083 * Process segments with URG.
2084 */
2085 if ((thflags & TH_URG) && th->th_urp &&
2086 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2087 /*
2088 * This is a kludge, but if we receive and accept
2089 * random urgent pointers, we'll crash in
2090 * soreceive. It's hard to imagine someone
2091 * actually wanting to send this much urgent data.
2092 */
2093 if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2094 th->th_urp = 0; /* XXX */
2095 thflags &= ~TH_URG; /* XXX */
2096 goto dodata; /* XXX */
2097 }
2098 /*
2099 * If this segment advances the known urgent pointer,
2100 * then mark the data stream. This should not happen
2101 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2102 * a FIN has been received from the remote side.
2103 * In these states we ignore the URG.
2104 *
2105 * According to RFC961 (Assigned Protocols),
2106 * the urgent pointer points to the last octet
2107 * of urgent data. We continue, however,
2108 * to consider it to indicate the first octet
2109 * of data past the urgent section as the original
2110 * spec states (in one of two places).
2111 */
2112 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2113 tp->rcv_up = th->th_seq + th->th_urp;
2114 so->so_oobmark = so->so_rcv.sb_cc +
2115 (tp->rcv_up - tp->rcv_nxt) - 1;
2116 if (so->so_oobmark == 0)
2117 so->so_state |= SS_RCVATMARK;
2118 sohasoutofband(so);
2119 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2120 }
2121 /*
2122 * Remove out of band data so doesn't get presented to user.
2123 * This can happen independent of advancing the URG pointer,
2124 * but if two URG's are pending at once, some out-of-band
2125 * data may creep in... ick.
2126 */
2127 if (th->th_urp <= (u_long)tlen &&
2128 !(so->so_options & SO_OOBINLINE)) {
2129 /* hdr drop is delayed */
2130 tcp_pulloutofband(so, th, m, drop_hdrlen);
2131 }
2132 } else {
2133 /*
2134 * If no out of band data is expected,
2135 * pull receive urgent pointer along
2136 * with the receive window.
2137 */
2138 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2139 tp->rcv_up = tp->rcv_nxt;
2140 }
2141dodata: /* XXX */
2142 KASSERT(headlocked, ("headlocked"));
2143 /*
2144 * Process the segment text, merging it into the TCP sequencing queue,
2145 * and arranging for acknowledgment of receipt if necessary.
2146 * This process logically involves adjusting tp->rcv_wnd as data
2147 * is presented to the user (this happens in tcp_usrreq.c,
2148 * case PRU_RCVD). If a FIN has already been received on this
2149 * connection then we just ignore the text.
2150 */
2151 if ((tlen || (thflags & TH_FIN)) &&
2152 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2153 m_adj(m, drop_hdrlen); /* delayed header drop */
2154 /*
2155 * Insert segment which includes th into TCP reassembly queue
2156 * with control block tp. Set thflags to whether reassembly now
2157 * includes a segment with FIN. This handles the common case
2158 * inline (segment is the next to be received on an established
2159 * connection, and the queue is empty), avoiding linkage into
2160 * and removal from the queue and repetition of various
2161 * conversions.
2162 * Set DELACK for segments received in order, but ack
2163 * immediately when segments are out of order (so
2164 * fast retransmit can work).
2165 */
2166 if (th->th_seq == tp->rcv_nxt &&
2167 LIST_EMPTY(&tp->t_segq) &&
2168 TCPS_HAVEESTABLISHED(tp->t_state)) {
2169 if (DELAY_ACK(tp))
2170 tp->t_flags |= TF_DELACK;
2171 else
2172 tp->t_flags |= TF_ACKNOW;
2173 tp->rcv_nxt += tlen;
2174 thflags = th->th_flags & TH_FIN;
2175 tcpstat.tcps_rcvpack++;
2176 tcpstat.tcps_rcvbyte += tlen;
2177 ND6_HINT(tp);
2178 if (so->so_state & SS_CANTRCVMORE)
2179 m_freem(m);
2180 else
| 1128 }
1129 sorwakeup(so);
1130 if (DELAY_ACK(tp)) {
1131 tp->t_flags |= TF_DELACK;
1132 } else {
1133 tp->t_flags |= TF_ACKNOW;
1134 tcp_output(tp);
1135 }
1136 goto check_delack;
1137 }
1138 }
1139
1140 /*
1141 * Calculate amount of space in receive window,
1142 * and then do TCP input processing.
1143 * Receive window is amount of space in rcv queue,
1144 * but not less than advertised window.
1145 */
1146 { int win;
1147
1148 win = sbspace(&so->so_rcv);
1149 if (win < 0)
1150 win = 0;
1151 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1152 }
1153
1154 switch (tp->t_state) {
1155
1156 /*
1157 * If the state is SYN_RECEIVED:
1158 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1159 */
1160 case TCPS_SYN_RECEIVED:
1161 if ((thflags & TH_ACK) &&
1162 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1163 SEQ_GT(th->th_ack, tp->snd_max))) {
1164 rstreason = BANDLIM_RST_OPENPORT;
1165 goto dropwithreset;
1166 }
1167 break;
1168
1169 /*
1170 * If the state is SYN_SENT:
1171 * if seg contains an ACK, but not for our SYN, drop the input.
1172 * if seg contains a RST, then drop the connection.
1173 * if seg does not contain SYN, then drop it.
1174 * Otherwise this is an acceptable SYN segment
1175 * initialize tp->rcv_nxt and tp->irs
1176 * if seg contains ack then advance tp->snd_una
1177 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1178 * arrange for segment to be acked (eventually)
1179 * continue processing rest of data/controls, beginning with URG
1180 */
1181 case TCPS_SYN_SENT:
1182 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) {
1183 taop = &tao_noncached;
1184 bzero(taop, sizeof(*taop));
1185 }
1186
1187 if ((thflags & TH_ACK) &&
1188 (SEQ_LEQ(th->th_ack, tp->iss) ||
1189 SEQ_GT(th->th_ack, tp->snd_max))) {
1190 /*
1191 * If we have a cached CCsent for the remote host,
1192 * hence we haven't just crashed and restarted,
1193 * do not send a RST. This may be a retransmission
1194 * from the other side after our earlier ACK was lost.
1195 * Our new SYN, when it arrives, will serve as the
1196 * needed ACK.
1197 */
1198 if (taop->tao_ccsent != 0)
1199 goto drop;
1200 else {
1201 rstreason = BANDLIM_UNLIMITED;
1202 goto dropwithreset;
1203 }
1204 }
1205 if (thflags & TH_RST) {
1206 if (thflags & TH_ACK)
1207 tp = tcp_drop(tp, ECONNREFUSED);
1208 goto drop;
1209 }
1210 if ((thflags & TH_SYN) == 0)
1211 goto drop;
1212 tp->snd_wnd = th->th_win; /* initial send window */
1213 tp->cc_recv = to.to_cc; /* foreign CC */
1214
1215 tp->irs = th->th_seq;
1216 tcp_rcvseqinit(tp);
1217 if (thflags & TH_ACK) {
1218 /*
1219 * Our SYN was acked. If segment contains CC.ECHO
1220 * option, check it to make sure this segment really
1221 * matches our SYN. If not, just drop it as old
1222 * duplicate, but send an RST if we're still playing
1223 * by the old rules. If no CC.ECHO option, make sure
1224 * we don't get fooled into using T/TCP.
1225 */
1226 if (to.to_flags & TOF_CCECHO) {
1227 if (tp->cc_send != to.to_ccecho) {
1228 if (taop->tao_ccsent != 0)
1229 goto drop;
1230 else {
1231 rstreason = BANDLIM_UNLIMITED;
1232 goto dropwithreset;
1233 }
1234 }
1235 } else
1236 tp->t_flags &= ~TF_RCVD_CC;
1237 tcpstat.tcps_connects++;
1238 soisconnected(so);
1239#ifdef MAC
1240 mac_set_socket_peer_from_mbuf(m, so);
1241#endif
1242 /* Do window scaling on this connection? */
1243 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1244 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1245 tp->snd_scale = tp->requested_s_scale;
1246 tp->rcv_scale = tp->request_r_scale;
1247 }
1248 /* Segment is acceptable, update cache if undefined. */
1249 if (taop->tao_ccsent == 0)
1250 taop->tao_ccsent = to.to_ccecho;
1251
1252 tp->rcv_adv += tp->rcv_wnd;
1253 tp->snd_una++; /* SYN is acked */
1254 /*
1255 * If there's data, delay ACK; if there's also a FIN
1256 * ACKNOW will be turned on later.
1257 */
1258 if (DELAY_ACK(tp) && tlen != 0)
1259 callout_reset(tp->tt_delack, tcp_delacktime,
1260 tcp_timer_delack, tp);
1261 else
1262 tp->t_flags |= TF_ACKNOW;
1263 /*
1264 * Received <SYN,ACK> in SYN_SENT[*] state.
1265 * Transitions:
1266 * SYN_SENT --> ESTABLISHED
1267 * SYN_SENT* --> FIN_WAIT_1
1268 */
1269 tp->t_starttime = ticks;
1270 if (tp->t_flags & TF_NEEDFIN) {
1271 tp->t_state = TCPS_FIN_WAIT_1;
1272 tp->t_flags &= ~TF_NEEDFIN;
1273 thflags &= ~TH_SYN;
1274 } else {
1275 tp->t_state = TCPS_ESTABLISHED;
1276 callout_reset(tp->tt_keep, tcp_keepidle,
1277 tcp_timer_keep, tp);
1278 }
1279 } else {
1280 /*
1281 * Received initial SYN in SYN-SENT[*] state =>
1282 * simultaneous open. If segment contains CC option
1283 * and there is a cached CC, apply TAO test.
1284 * If it succeeds, connection is * half-synchronized.
1285 * Otherwise, do 3-way handshake:
1286 * SYN-SENT -> SYN-RECEIVED
1287 * SYN-SENT* -> SYN-RECEIVED*
1288 * If there was no CC option, clear cached CC value.
1289 */
1290 tp->t_flags |= TF_ACKNOW;
1291 callout_stop(tp->tt_rexmt);
1292 if (to.to_flags & TOF_CC) {
1293 if (taop->tao_cc != 0 &&
1294 CC_GT(to.to_cc, taop->tao_cc)) {
1295 /*
1296 * update cache and make transition:
1297 * SYN-SENT -> ESTABLISHED*
1298 * SYN-SENT* -> FIN-WAIT-1*
1299 */
1300 taop->tao_cc = to.to_cc;
1301 tp->t_starttime = ticks;
1302 if (tp->t_flags & TF_NEEDFIN) {
1303 tp->t_state = TCPS_FIN_WAIT_1;
1304 tp->t_flags &= ~TF_NEEDFIN;
1305 } else {
1306 tp->t_state = TCPS_ESTABLISHED;
1307 callout_reset(tp->tt_keep,
1308 tcp_keepidle,
1309 tcp_timer_keep,
1310 tp);
1311 }
1312 tp->t_flags |= TF_NEEDSYN;
1313 } else
1314 tp->t_state = TCPS_SYN_RECEIVED;
1315 } else {
1316 /* CC.NEW or no option => invalidate cache */
1317 taop->tao_cc = 0;
1318 tp->t_state = TCPS_SYN_RECEIVED;
1319 }
1320 }
1321
1322trimthenstep6:
1323 /*
1324 * Advance th->th_seq to correspond to first data byte.
1325 * If data, trim to stay within window,
1326 * dropping FIN if necessary.
1327 */
1328 th->th_seq++;
1329 if (tlen > tp->rcv_wnd) {
1330 todrop = tlen - tp->rcv_wnd;
1331 m_adj(m, -todrop);
1332 tlen = tp->rcv_wnd;
1333 thflags &= ~TH_FIN;
1334 tcpstat.tcps_rcvpackafterwin++;
1335 tcpstat.tcps_rcvbyteafterwin += todrop;
1336 }
1337 tp->snd_wl1 = th->th_seq - 1;
1338 tp->rcv_up = th->th_seq;
1339 /*
1340 * Client side of transaction: already sent SYN and data.
1341 * If the remote host used T/TCP to validate the SYN,
1342 * our data will be ACK'd; if so, enter normal data segment
1343 * processing in the middle of step 5, ack processing.
1344 * Otherwise, goto step 6.
1345 */
1346 if (thflags & TH_ACK)
1347 goto process_ACK;
1348
1349 goto step6;
1350
1351 /*
1352 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1353 * if segment contains a SYN and CC [not CC.NEW] option:
1354 * if state == TIME_WAIT and connection duration > MSL,
1355 * drop packet and send RST;
1356 *
1357 * if SEG.CC > CCrecv then is new SYN, and can implicitly
1358 * ack the FIN (and data) in retransmission queue.
1359 * Complete close and delete TCPCB. Then reprocess
1360 * segment, hoping to find new TCPCB in LISTEN state;
1361 *
1362 * else must be old SYN; drop it.
1363 * else do normal processing.
1364 */
1365 case TCPS_LAST_ACK:
1366 case TCPS_CLOSING:
1367 case TCPS_TIME_WAIT:
1368 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1369 if ((thflags & TH_SYN) &&
1370 (to.to_flags & TOF_CC) && tp->cc_recv != 0) {
1371 if (tp->t_state == TCPS_TIME_WAIT &&
1372 (ticks - tp->t_starttime) > tcp_msl) {
1373 rstreason = BANDLIM_UNLIMITED;
1374 goto dropwithreset;
1375 }
1376 if (CC_GT(to.to_cc, tp->cc_recv)) {
1377 tp = tcp_close(tp);
1378 goto findpcb;
1379 }
1380 else
1381 goto drop;
1382 }
1383 break; /* continue normal processing */
1384 }
1385
1386 /*
1387 * States other than LISTEN or SYN_SENT.
1388 * First check the RST flag and sequence number since reset segments
1389 * are exempt from the timestamp and connection count tests. This
1390 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1391 * below which allowed reset segments in half the sequence space
1392 * to fall though and be processed (which gives forged reset
1393 * segments with a random sequence number a 50 percent chance of
1394 * killing a connection).
1395 * Then check timestamp, if present.
1396 * Then check the connection count, if present.
1397 * Then check that at least some bytes of segment are within
1398 * receive window. If segment begins before rcv_nxt,
1399 * drop leading data (and SYN); if nothing left, just ack.
1400 *
1401 *
1402 * If the RST bit is set, check the sequence number to see
1403 * if this is a valid reset segment.
1404 * RFC 793 page 37:
1405 * In all states except SYN-SENT, all reset (RST) segments
1406 * are validated by checking their SEQ-fields. A reset is
1407 * valid if its sequence number is in the window.
1408 * Note: this does not take into account delayed ACKs, so
1409 * we should test against last_ack_sent instead of rcv_nxt.
1410 * The sequence number in the reset segment is normally an
1411 * echo of our outgoing acknowlegement numbers, but some hosts
1412 * send a reset with the sequence number at the rightmost edge
1413 * of our receive window, and we have to handle this case.
1414 * If we have multiple segments in flight, the intial reset
1415 * segment sequence numbers will be to the left of last_ack_sent,
1416 * but they will eventually catch up.
1417 * In any case, it never made sense to trim reset segments to
1418 * fit the receive window since RFC 1122 says:
1419 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1420 *
1421 * A TCP SHOULD allow a received RST segment to include data.
1422 *
1423 * DISCUSSION
1424 * It has been suggested that a RST segment could contain
1425 * ASCII text that encoded and explained the cause of the
1426 * RST. No standard has yet been established for such
1427 * data.
1428 *
1429 * If the reset segment passes the sequence number test examine
1430 * the state:
1431 * SYN_RECEIVED STATE:
1432 * If passive open, return to LISTEN state.
1433 * If active open, inform user that connection was refused.
1434 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1435 * Inform user that connection was reset, and close tcb.
1436 * CLOSING, LAST_ACK STATES:
1437 * Close the tcb.
1438 * TIME_WAIT STATE:
1439 * Drop the segment - see Stevens, vol. 2, p. 964 and
1440 * RFC 1337.
1441 */
1442 if (thflags & TH_RST) {
1443 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1444 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1445 switch (tp->t_state) {
1446
1447 case TCPS_SYN_RECEIVED:
1448 so->so_error = ECONNREFUSED;
1449 goto close;
1450
1451 case TCPS_ESTABLISHED:
1452 case TCPS_FIN_WAIT_1:
1453 case TCPS_FIN_WAIT_2:
1454 case TCPS_CLOSE_WAIT:
1455 so->so_error = ECONNRESET;
1456 close:
1457 tp->t_state = TCPS_CLOSED;
1458 tcpstat.tcps_drops++;
1459 tp = tcp_close(tp);
1460 break;
1461
1462 case TCPS_CLOSING:
1463 case TCPS_LAST_ACK:
1464 tp = tcp_close(tp);
1465 break;
1466
1467 case TCPS_TIME_WAIT:
1468 KASSERT(tp->t_state != TCPS_TIME_WAIT,
1469 ("timewait"));
1470 break;
1471 }
1472 }
1473 goto drop;
1474 }
1475
1476 /*
1477 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1478 * and it's less than ts_recent, drop it.
1479 */
1480 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
1481 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1482
1483 /* Check to see if ts_recent is over 24 days old. */
1484 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1485 /*
1486 * Invalidate ts_recent. If this segment updates
1487 * ts_recent, the age will be reset later and ts_recent
1488 * will get a valid value. If it does not, setting
1489 * ts_recent to zero will at least satisfy the
1490 * requirement that zero be placed in the timestamp
1491 * echo reply when ts_recent isn't valid. The
1492 * age isn't reset until we get a valid ts_recent
1493 * because we don't want out-of-order segments to be
1494 * dropped when ts_recent is old.
1495 */
1496 tp->ts_recent = 0;
1497 } else {
1498 tcpstat.tcps_rcvduppack++;
1499 tcpstat.tcps_rcvdupbyte += tlen;
1500 tcpstat.tcps_pawsdrop++;
1501 if (tlen)
1502 goto dropafterack;
1503 goto drop;
1504 }
1505 }
1506
1507 /*
1508 * T/TCP mechanism
1509 * If T/TCP was negotiated and the segment doesn't have CC,
1510 * or if its CC is wrong then drop the segment.
1511 * RST segments do not have to comply with this.
1512 */
1513 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
1514 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc))
1515 goto dropafterack;
1516
1517 /*
1518 * In the SYN-RECEIVED state, validate that the packet belongs to
1519 * this connection before trimming the data to fit the receive
1520 * window. Check the sequence number versus IRS since we know
1521 * the sequence numbers haven't wrapped. This is a partial fix
1522 * for the "LAND" DoS attack.
1523 */
1524 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1525 rstreason = BANDLIM_RST_OPENPORT;
1526 goto dropwithreset;
1527 }
1528
1529 todrop = tp->rcv_nxt - th->th_seq;
1530 if (todrop > 0) {
1531 if (thflags & TH_SYN) {
1532 thflags &= ~TH_SYN;
1533 th->th_seq++;
1534 if (th->th_urp > 1)
1535 th->th_urp--;
1536 else
1537 thflags &= ~TH_URG;
1538 todrop--;
1539 }
1540 /*
1541 * Following if statement from Stevens, vol. 2, p. 960.
1542 */
1543 if (todrop > tlen
1544 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
1545 /*
1546 * Any valid FIN must be to the left of the window.
1547 * At this point the FIN must be a duplicate or out
1548 * of sequence; drop it.
1549 */
1550 thflags &= ~TH_FIN;
1551
1552 /*
1553 * Send an ACK to resynchronize and drop any data.
1554 * But keep on processing for RST or ACK.
1555 */
1556 tp->t_flags |= TF_ACKNOW;
1557 todrop = tlen;
1558 tcpstat.tcps_rcvduppack++;
1559 tcpstat.tcps_rcvdupbyte += todrop;
1560 } else {
1561 tcpstat.tcps_rcvpartduppack++;
1562 tcpstat.tcps_rcvpartdupbyte += todrop;
1563 }
1564 drop_hdrlen += todrop; /* drop from the top afterwards */
1565 th->th_seq += todrop;
1566 tlen -= todrop;
1567 if (th->th_urp > todrop)
1568 th->th_urp -= todrop;
1569 else {
1570 thflags &= ~TH_URG;
1571 th->th_urp = 0;
1572 }
1573 }
1574
1575 /*
1576 * If new data are received on a connection after the
1577 * user processes are gone, then RST the other end.
1578 */
1579 if ((so->so_state & SS_NOFDREF) &&
1580 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1581 tp = tcp_close(tp);
1582 tcpstat.tcps_rcvafterclose++;
1583 rstreason = BANDLIM_UNLIMITED;
1584 goto dropwithreset;
1585 }
1586
1587 /*
1588 * If segment ends after window, drop trailing data
1589 * (and PUSH and FIN); if nothing left, just ACK.
1590 */
1591 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd);
1592 if (todrop > 0) {
1593 tcpstat.tcps_rcvpackafterwin++;
1594 if (todrop >= tlen) {
1595 tcpstat.tcps_rcvbyteafterwin += tlen;
1596 /*
1597 * If a new connection request is received
1598 * while in TIME_WAIT, drop the old connection
1599 * and start over if the sequence numbers
1600 * are above the previous ones.
1601 */
1602 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1603 if (thflags & TH_SYN &&
1604 tp->t_state == TCPS_TIME_WAIT &&
1605 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1606 tp = tcp_close(tp);
1607 goto findpcb;
1608 }
1609 /*
1610 * If window is closed can only take segments at
1611 * window edge, and have to drop data and PUSH from
1612 * incoming segments. Continue processing, but
1613 * remember to ack. Otherwise, drop segment
1614 * and ack.
1615 */
1616 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1617 tp->t_flags |= TF_ACKNOW;
1618 tcpstat.tcps_rcvwinprobe++;
1619 } else
1620 goto dropafterack;
1621 } else
1622 tcpstat.tcps_rcvbyteafterwin += todrop;
1623 m_adj(m, -todrop);
1624 tlen -= todrop;
1625 thflags &= ~(TH_PUSH|TH_FIN);
1626 }
1627
1628 /*
1629 * If last ACK falls within this segment's sequence numbers,
1630 * record its timestamp.
1631 * NOTE that the test is modified according to the latest
1632 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1633 */
1634 if ((to.to_flags & TOF_TS) != 0 &&
1635 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1636 tp->ts_recent_age = ticks;
1637 tp->ts_recent = to.to_tsval;
1638 }
1639
1640 /*
1641 * If a SYN is in the window, then this is an
1642 * error and we send an RST and drop the connection.
1643 */
1644 if (thflags & TH_SYN) {
1645 tp = tcp_drop(tp, ECONNRESET);
1646 rstreason = BANDLIM_UNLIMITED;
1647 goto dropwithreset;
1648 }
1649
1650 /*
1651 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1652 * flag is on (half-synchronized state), then queue data for
1653 * later processing; else drop segment and return.
1654 */
1655 if ((thflags & TH_ACK) == 0) {
1656 if (tp->t_state == TCPS_SYN_RECEIVED ||
1657 (tp->t_flags & TF_NEEDSYN))
1658 goto step6;
1659 else
1660 goto drop;
1661 }
1662
1663 /*
1664 * Ack processing.
1665 */
1666 switch (tp->t_state) {
1667
1668 /*
1669 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
1670 * ESTABLISHED state and continue processing.
1671 * The ACK was checked above.
1672 */
1673 case TCPS_SYN_RECEIVED:
1674
1675 tcpstat.tcps_connects++;
1676 soisconnected(so);
1677 /* Do window scaling? */
1678 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1679 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1680 tp->snd_scale = tp->requested_s_scale;
1681 tp->rcv_scale = tp->request_r_scale;
1682 }
1683 /*
1684 * Upon successful completion of 3-way handshake,
1685 * update cache.CC if it was undefined, pass any queued
1686 * data to the user, and advance state appropriately.
1687 */
1688 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL &&
1689 taop->tao_cc == 0)
1690 taop->tao_cc = tp->cc_recv;
1691
1692 /*
1693 * Make transitions:
1694 * SYN-RECEIVED -> ESTABLISHED
1695 * SYN-RECEIVED* -> FIN-WAIT-1
1696 */
1697 tp->t_starttime = ticks;
1698 if (tp->t_flags & TF_NEEDFIN) {
1699 tp->t_state = TCPS_FIN_WAIT_1;
1700 tp->t_flags &= ~TF_NEEDFIN;
1701 } else {
1702 tp->t_state = TCPS_ESTABLISHED;
1703 callout_reset(tp->tt_keep, tcp_keepidle,
1704 tcp_timer_keep, tp);
1705 }
1706 /*
1707 * If segment contains data or ACK, will call tcp_reass()
1708 * later; if not, do so now to pass queued data to user.
1709 */
1710 if (tlen == 0 && (thflags & TH_FIN) == 0)
1711 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
1712 (struct mbuf *)0);
1713 tp->snd_wl1 = th->th_seq - 1;
1714 /* FALLTHROUGH */
1715
1716 /*
1717 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1718 * ACKs. If the ack is in the range
1719 * tp->snd_una < th->th_ack <= tp->snd_max
1720 * then advance tp->snd_una to th->th_ack and drop
1721 * data from the retransmission queue. If this ACK reflects
1722 * more up to date window information we update our window information.
1723 */
1724 case TCPS_ESTABLISHED:
1725 case TCPS_FIN_WAIT_1:
1726 case TCPS_FIN_WAIT_2:
1727 case TCPS_CLOSE_WAIT:
1728 case TCPS_CLOSING:
1729 case TCPS_LAST_ACK:
1730 case TCPS_TIME_WAIT:
1731 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1732 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
1733 if (tlen == 0 && tiwin == tp->snd_wnd) {
1734 tcpstat.tcps_rcvdupack++;
1735 /*
1736 * If we have outstanding data (other than
1737 * a window probe), this is a completely
1738 * duplicate ack (ie, window info didn't
1739 * change), the ack is the biggest we've
1740 * seen and we've seen exactly our rexmt
1741 * threshhold of them, assume a packet
1742 * has been dropped and retransmit it.
1743 * Kludge snd_nxt & the congestion
1744 * window so we send only this one
1745 * packet.
1746 *
1747 * We know we're losing at the current
1748 * window size so do congestion avoidance
1749 * (set ssthresh to half the current window
1750 * and pull our congestion window back to
1751 * the new ssthresh).
1752 *
1753 * Dup acks mean that packets have left the
1754 * network (they're now cached at the receiver)
1755 * so bump cwnd by the amount in the receiver
1756 * to keep a constant cwnd packets in the
1757 * network.
1758 */
1759 if (!callout_active(tp->tt_rexmt) ||
1760 th->th_ack != tp->snd_una)
1761 tp->t_dupacks = 0;
1762 else if (++tp->t_dupacks > tcprexmtthresh ||
1763 (tcp_do_newreno &&
1764 IN_FASTRECOVERY(tp))) {
1765 tp->snd_cwnd += tp->t_maxseg;
1766 (void) tcp_output(tp);
1767 goto drop;
1768 } else if (tp->t_dupacks == tcprexmtthresh) {
1769 tcp_seq onxt = tp->snd_nxt;
1770 u_int win;
1771 if (tcp_do_newreno &&
1772 SEQ_LEQ(th->th_ack,
1773 tp->snd_recover)) {
1774 tp->t_dupacks = 0;
1775 break;
1776 }
1777 win = min(tp->snd_wnd, tp->snd_cwnd) /
1778 2 / tp->t_maxseg;
1779 if (win < 2)
1780 win = 2;
1781 tp->snd_ssthresh = win * tp->t_maxseg;
1782 ENTER_FASTRECOVERY(tp);
1783 tp->snd_recover = tp->snd_max;
1784 callout_stop(tp->tt_rexmt);
1785 tp->t_rtttime = 0;
1786 tp->snd_nxt = th->th_ack;
1787 tp->snd_cwnd = tp->t_maxseg;
1788 (void) tcp_output(tp);
1789 KASSERT(tp->snd_limited <= 2,
1790 ("tp->snd_limited too big"));
1791 tp->snd_cwnd = tp->snd_ssthresh +
1792 tp->t_maxseg *
1793 (tp->t_dupacks - tp->snd_limited);
1794 if (SEQ_GT(onxt, tp->snd_nxt))
1795 tp->snd_nxt = onxt;
1796 goto drop;
1797 } else if (tcp_do_rfc3042) {
1798 u_long oldcwnd = tp->snd_cwnd;
1799 tcp_seq oldsndmax = tp->snd_max;
1800 u_int sent;
1801 KASSERT(tp->t_dupacks == 1 ||
1802 tp->t_dupacks == 2,
1803 ("dupacks not 1 or 2"));
1804 if (tp->t_dupacks == 1) {
1805 tp->snd_limited = 0;
1806 tp->snd_cwnd += tp->t_maxseg;
1807 } else {
1808 tp->snd_cwnd +=
1809 tp->t_maxseg * 2;
1810 }
1811 (void) tcp_output(tp);
1812 sent = tp->snd_max - oldsndmax;
1813 if (sent > tp->t_maxseg) {
1814 KASSERT(tp->snd_limited == 0 &&
1815 tp->t_dupacks == 2,
1816 ("sent too much"));
1817 tp->snd_limited = 2;
1818 } else if (sent > 0)
1819 ++tp->snd_limited;
1820 tp->snd_cwnd = oldcwnd;
1821 goto drop;
1822 }
1823 } else
1824 tp->t_dupacks = 0;
1825 break;
1826 }
1827
1828 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
1829
1830 /*
1831 * If the congestion window was inflated to account
1832 * for the other side's cached packets, retract it.
1833 */
1834 if (tcp_do_newreno) {
1835 if (IN_FASTRECOVERY(tp)) {
1836 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
1837 tcp_newreno_partial_ack(tp, th);
1838 } else {
1839 /*
1840 * Window inflation should have left us
1841 * with approximately snd_ssthresh
1842 * outstanding data.
1843 * But in case we would be inclined to
1844 * send a burst, better to do it via
1845 * the slow start mechanism.
1846 */
1847 if (SEQ_GT(th->th_ack +
1848 tp->snd_ssthresh,
1849 tp->snd_max))
1850 tp->snd_cwnd = tp->snd_max -
1851 th->th_ack +
1852 tp->t_maxseg;
1853 else
1854 tp->snd_cwnd = tp->snd_ssthresh;
1855 }
1856 }
1857 } else {
1858 if (tp->t_dupacks >= tcprexmtthresh &&
1859 tp->snd_cwnd > tp->snd_ssthresh)
1860 tp->snd_cwnd = tp->snd_ssthresh;
1861 }
1862 tp->t_dupacks = 0;
1863 if (SEQ_GT(th->th_ack, tp->snd_max)) {
1864 tcpstat.tcps_rcvacktoomuch++;
1865 goto dropafterack;
1866 }
1867 /*
1868 * If we reach this point, ACK is not a duplicate,
1869 * i.e., it ACKs something we sent.
1870 */
1871 if (tp->t_flags & TF_NEEDSYN) {
1872 /*
1873 * T/TCP: Connection was half-synchronized, and our
1874 * SYN has been ACK'd (so connection is now fully
1875 * synchronized). Go to non-starred state,
1876 * increment snd_una for ACK of SYN, and check if
1877 * we can do window scaling.
1878 */
1879 tp->t_flags &= ~TF_NEEDSYN;
1880 tp->snd_una++;
1881 /* Do window scaling? */
1882 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1883 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1884 tp->snd_scale = tp->requested_s_scale;
1885 tp->rcv_scale = tp->request_r_scale;
1886 }
1887 }
1888
1889process_ACK:
1890 acked = th->th_ack - tp->snd_una;
1891 tcpstat.tcps_rcvackpack++;
1892 tcpstat.tcps_rcvackbyte += acked;
1893
1894 /*
1895 * If we just performed our first retransmit, and the ACK
1896 * arrives within our recovery window, then it was a mistake
1897 * to do the retransmit in the first place. Recover our
1898 * original cwnd and ssthresh, and proceed to transmit where
1899 * we left off.
1900 */
1901 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
1902 ++tcpstat.tcps_sndrexmitbad;
1903 tp->snd_cwnd = tp->snd_cwnd_prev;
1904 tp->snd_ssthresh = tp->snd_ssthresh_prev;
1905 tp->snd_recover = tp->snd_recover_prev;
1906 if (tp->t_flags & TF_WASFRECOVERY)
1907 ENTER_FASTRECOVERY(tp);
1908 tp->snd_nxt = tp->snd_max;
1909 tp->t_badrxtwin = 0; /* XXX probably not required */
1910 }
1911
1912 /*
1913 * If we have a timestamp reply, update smoothed
1914 * round trip time. If no timestamp is present but
1915 * transmit timer is running and timed sequence
1916 * number was acked, update smoothed round trip time.
1917 * Since we now have an rtt measurement, cancel the
1918 * timer backoff (cf., Phil Karn's retransmit alg.).
1919 * Recompute the initial retransmit timer.
1920 *
1921 * Some boxes send broken timestamp replies
1922 * during the SYN+ACK phase, ignore
1923 * timestamps of 0 or we could calculate a
1924 * huge RTT and blow up the retransmit timer.
1925 */
1926 if ((to.to_flags & TOF_TS) != 0 &&
1927 to.to_tsecr) {
1928 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
1929 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
1930 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
1931 }
1932 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1933
1934 /*
1935 * If all outstanding data is acked, stop retransmit
1936 * timer and remember to restart (more output or persist).
1937 * If there is more data to be acked, restart retransmit
1938 * timer, using current (possibly backed-off) value.
1939 */
1940 if (th->th_ack == tp->snd_max) {
1941 callout_stop(tp->tt_rexmt);
1942 needoutput = 1;
1943 } else if (!callout_active(tp->tt_persist))
1944 callout_reset(tp->tt_rexmt, tp->t_rxtcur,
1945 tcp_timer_rexmt, tp);
1946
1947 /*
1948 * If no data (only SYN) was ACK'd,
1949 * skip rest of ACK processing.
1950 */
1951 if (acked == 0)
1952 goto step6;
1953
1954 /*
1955 * When new data is acked, open the congestion window.
1956 * If the window gives us less than ssthresh packets
1957 * in flight, open exponentially (maxseg per packet).
1958 * Otherwise open linearly: maxseg per window
1959 * (maxseg^2 / cwnd per packet).
1960 */
1961 if (!tcp_do_newreno || !IN_FASTRECOVERY(tp)) {
1962 register u_int cw = tp->snd_cwnd;
1963 register u_int incr = tp->t_maxseg;
1964 if (cw > tp->snd_ssthresh)
1965 incr = incr * incr / cw;
1966 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
1967 }
1968 if (acked > so->so_snd.sb_cc) {
1969 tp->snd_wnd -= so->so_snd.sb_cc;
1970 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
1971 ourfinisacked = 1;
1972 } else {
1973 sbdrop(&so->so_snd, acked);
1974 tp->snd_wnd -= acked;
1975 ourfinisacked = 0;
1976 }
1977 sowwakeup(so);
1978 /* detect una wraparound */
1979 if (tcp_do_newreno && !IN_FASTRECOVERY(tp) &&
1980 SEQ_GT(tp->snd_una, tp->snd_recover) &&
1981 SEQ_LEQ(th->th_ack, tp->snd_recover))
1982 tp->snd_recover = th->th_ack - 1;
1983 if (tcp_do_newreno && IN_FASTRECOVERY(tp) &&
1984 SEQ_GEQ(th->th_ack, tp->snd_recover))
1985 EXIT_FASTRECOVERY(tp);
1986 tp->snd_una = th->th_ack;
1987 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
1988 tp->snd_nxt = tp->snd_una;
1989
1990 switch (tp->t_state) {
1991
1992 /*
1993 * In FIN_WAIT_1 STATE in addition to the processing
1994 * for the ESTABLISHED state if our FIN is now acknowledged
1995 * then enter FIN_WAIT_2.
1996 */
1997 case TCPS_FIN_WAIT_1:
1998 if (ourfinisacked) {
1999 /*
2000 * If we can't receive any more
2001 * data, then closing user can proceed.
2002 * Starting the timer is contrary to the
2003 * specification, but if we don't get a FIN
2004 * we'll hang forever.
2005 */
2006 /* XXXjl
2007 * we should release the tp also, and use a
2008 * compressed state.
2009 */
2010 if (so->so_state & SS_CANTRCVMORE) {
2011 soisdisconnected(so);
2012 callout_reset(tp->tt_2msl, tcp_maxidle,
2013 tcp_timer_2msl, tp);
2014 }
2015 tp->t_state = TCPS_FIN_WAIT_2;
2016 }
2017 break;
2018
2019 /*
2020 * In CLOSING STATE in addition to the processing for
2021 * the ESTABLISHED state if the ACK acknowledges our FIN
2022 * then enter the TIME-WAIT state, otherwise ignore
2023 * the segment.
2024 */
2025 case TCPS_CLOSING:
2026 if (ourfinisacked) {
2027 KASSERT(headlocked, ("headlocked"));
2028 tcp_twstart(tp);
2029 INP_INFO_WUNLOCK(&tcbinfo);
2030 m_freem(m);
2031 return;
2032 }
2033 break;
2034
2035 /*
2036 * In LAST_ACK, we may still be waiting for data to drain
2037 * and/or to be acked, as well as for the ack of our FIN.
2038 * If our FIN is now acknowledged, delete the TCB,
2039 * enter the closed state and return.
2040 */
2041 case TCPS_LAST_ACK:
2042 if (ourfinisacked) {
2043 tp = tcp_close(tp);
2044 goto drop;
2045 }
2046 break;
2047
2048 /*
2049 * In TIME_WAIT state the only thing that should arrive
2050 * is a retransmission of the remote FIN. Acknowledge
2051 * it and restart the finack timer.
2052 */
2053 case TCPS_TIME_WAIT:
2054 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
2055 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2056 tcp_timer_2msl, tp);
2057 goto dropafterack;
2058 }
2059 }
2060
2061step6:
2062 /*
2063 * Update window information.
2064 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2065 */
2066 if ((thflags & TH_ACK) &&
2067 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2068 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2069 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2070 /* keep track of pure window updates */
2071 if (tlen == 0 &&
2072 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2073 tcpstat.tcps_rcvwinupd++;
2074 tp->snd_wnd = tiwin;
2075 tp->snd_wl1 = th->th_seq;
2076 tp->snd_wl2 = th->th_ack;
2077 if (tp->snd_wnd > tp->max_sndwnd)
2078 tp->max_sndwnd = tp->snd_wnd;
2079 needoutput = 1;
2080 }
2081
2082 /*
2083 * Process segments with URG.
2084 */
2085 if ((thflags & TH_URG) && th->th_urp &&
2086 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2087 /*
2088 * This is a kludge, but if we receive and accept
2089 * random urgent pointers, we'll crash in
2090 * soreceive. It's hard to imagine someone
2091 * actually wanting to send this much urgent data.
2092 */
2093 if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2094 th->th_urp = 0; /* XXX */
2095 thflags &= ~TH_URG; /* XXX */
2096 goto dodata; /* XXX */
2097 }
2098 /*
2099 * If this segment advances the known urgent pointer,
2100 * then mark the data stream. This should not happen
2101 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2102 * a FIN has been received from the remote side.
2103 * In these states we ignore the URG.
2104 *
2105 * According to RFC961 (Assigned Protocols),
2106 * the urgent pointer points to the last octet
2107 * of urgent data. We continue, however,
2108 * to consider it to indicate the first octet
2109 * of data past the urgent section as the original
2110 * spec states (in one of two places).
2111 */
2112 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2113 tp->rcv_up = th->th_seq + th->th_urp;
2114 so->so_oobmark = so->so_rcv.sb_cc +
2115 (tp->rcv_up - tp->rcv_nxt) - 1;
2116 if (so->so_oobmark == 0)
2117 so->so_state |= SS_RCVATMARK;
2118 sohasoutofband(so);
2119 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2120 }
2121 /*
2122 * Remove out of band data so doesn't get presented to user.
2123 * This can happen independent of advancing the URG pointer,
2124 * but if two URG's are pending at once, some out-of-band
2125 * data may creep in... ick.
2126 */
2127 if (th->th_urp <= (u_long)tlen &&
2128 !(so->so_options & SO_OOBINLINE)) {
2129 /* hdr drop is delayed */
2130 tcp_pulloutofband(so, th, m, drop_hdrlen);
2131 }
2132 } else {
2133 /*
2134 * If no out of band data is expected,
2135 * pull receive urgent pointer along
2136 * with the receive window.
2137 */
2138 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2139 tp->rcv_up = tp->rcv_nxt;
2140 }
2141dodata: /* XXX */
2142 KASSERT(headlocked, ("headlocked"));
2143 /*
2144 * Process the segment text, merging it into the TCP sequencing queue,
2145 * and arranging for acknowledgment of receipt if necessary.
2146 * This process logically involves adjusting tp->rcv_wnd as data
2147 * is presented to the user (this happens in tcp_usrreq.c,
2148 * case PRU_RCVD). If a FIN has already been received on this
2149 * connection then we just ignore the text.
2150 */
2151 if ((tlen || (thflags & TH_FIN)) &&
2152 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2153 m_adj(m, drop_hdrlen); /* delayed header drop */
2154 /*
2155 * Insert segment which includes th into TCP reassembly queue
2156 * with control block tp. Set thflags to whether reassembly now
2157 * includes a segment with FIN. This handles the common case
2158 * inline (segment is the next to be received on an established
2159 * connection, and the queue is empty), avoiding linkage into
2160 * and removal from the queue and repetition of various
2161 * conversions.
2162 * Set DELACK for segments received in order, but ack
2163 * immediately when segments are out of order (so
2164 * fast retransmit can work).
2165 */
2166 if (th->th_seq == tp->rcv_nxt &&
2167 LIST_EMPTY(&tp->t_segq) &&
2168 TCPS_HAVEESTABLISHED(tp->t_state)) {
2169 if (DELAY_ACK(tp))
2170 tp->t_flags |= TF_DELACK;
2171 else
2172 tp->t_flags |= TF_ACKNOW;
2173 tp->rcv_nxt += tlen;
2174 thflags = th->th_flags & TH_FIN;
2175 tcpstat.tcps_rcvpack++;
2176 tcpstat.tcps_rcvbyte += tlen;
2177 ND6_HINT(tp);
2178 if (so->so_state & SS_CANTRCVMORE)
2179 m_freem(m);
2180 else
|
2181 sbappend(&so->so_rcv, m);
| 2181 sbappendstream(&so->so_rcv, m);
|
2182 sorwakeup(so);
2183 } else {
2184 thflags = tcp_reass(tp, th, &tlen, m);
2185 tp->t_flags |= TF_ACKNOW;
2186 }
2187
2188 /*
2189 * Note the amount of data that peer has sent into
2190 * our window, in order to estimate the sender's
2191 * buffer size.
2192 */
2193 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2194 } else {
2195 m_freem(m);
2196 thflags &= ~TH_FIN;
2197 }
2198
2199 /*
2200 * If FIN is received ACK the FIN and let the user know
2201 * that the connection is closing.
2202 */
2203 if (thflags & TH_FIN) {
2204 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2205 socantrcvmore(so);
2206 /*
2207 * If connection is half-synchronized
2208 * (ie NEEDSYN flag on) then delay ACK,
2209 * so it may be piggybacked when SYN is sent.
2210 * Otherwise, since we received a FIN then no
2211 * more input can be expected, send ACK now.
2212 */
2213 if (tp->t_flags & TF_NEEDSYN)
2214 tp->t_flags |= TF_DELACK;
2215 else
2216 tp->t_flags |= TF_ACKNOW;
2217 tp->rcv_nxt++;
2218 }
2219 switch (tp->t_state) {
2220
2221 /*
2222 * In SYN_RECEIVED and ESTABLISHED STATES
2223 * enter the CLOSE_WAIT state.
2224 */
2225 case TCPS_SYN_RECEIVED:
2226 tp->t_starttime = ticks;
2227 /*FALLTHROUGH*/
2228 case TCPS_ESTABLISHED:
2229 tp->t_state = TCPS_CLOSE_WAIT;
2230 break;
2231
2232 /*
2233 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2234 * enter the CLOSING state.
2235 */
2236 case TCPS_FIN_WAIT_1:
2237 tp->t_state = TCPS_CLOSING;
2238 break;
2239
2240 /*
2241 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2242 * starting the time-wait timer, turning off the other
2243 * standard timers.
2244 */
2245 case TCPS_FIN_WAIT_2:
2246 KASSERT(headlocked == 1, ("headlocked should be 1"));
2247 tcp_twstart(tp);
2248 INP_INFO_WUNLOCK(&tcbinfo);
2249 return;
2250
2251 /*
2252 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2253 */
2254 case TCPS_TIME_WAIT:
2255 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
2256 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2257 tcp_timer_2msl, tp);
2258 break;
2259 }
2260 }
2261 INP_INFO_WUNLOCK(&tcbinfo);
2262#ifdef TCPDEBUG
2263 if (so->so_options & SO_DEBUG)
2264 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
2265 &tcp_savetcp, 0);
2266#endif
2267
2268 /*
2269 * Return any desired output.
2270 */
2271 if (needoutput || (tp->t_flags & TF_ACKNOW))
2272 (void) tcp_output(tp);
2273
2274check_delack:
2275 if (tp->t_flags & TF_DELACK) {
2276 tp->t_flags &= ~TF_DELACK;
2277 callout_reset(tp->tt_delack, tcp_delacktime,
2278 tcp_timer_delack, tp);
2279 }
2280 INP_UNLOCK(inp);
2281 return;
2282
2283dropafterack:
2284 /*
2285 * Generate an ACK dropping incoming segment if it occupies
2286 * sequence space, where the ACK reflects our state.
2287 *
2288 * We can now skip the test for the RST flag since all
2289 * paths to this code happen after packets containing
2290 * RST have been dropped.
2291 *
2292 * In the SYN-RECEIVED state, don't send an ACK unless the
2293 * segment we received passes the SYN-RECEIVED ACK test.
2294 * If it fails send a RST. This breaks the loop in the
2295 * "LAND" DoS attack, and also prevents an ACK storm
2296 * between two listening ports that have been sent forged
2297 * SYN segments, each with the source address of the other.
2298 */
2299 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2300 (SEQ_GT(tp->snd_una, th->th_ack) ||
2301 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2302 rstreason = BANDLIM_RST_OPENPORT;
2303 goto dropwithreset;
2304 }
2305#ifdef TCPDEBUG
2306 if (so->so_options & SO_DEBUG)
2307 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2308 &tcp_savetcp, 0);
2309#endif
2310 KASSERT(headlocked, ("headlocked should be 1"));
2311 INP_INFO_WUNLOCK(&tcbinfo);
2312 m_freem(m);
2313 tp->t_flags |= TF_ACKNOW;
2314 (void) tcp_output(tp);
2315 INP_UNLOCK(inp);
2316 return;
2317
2318dropwithreset:
2319 /*
2320 * Generate a RST, dropping incoming segment.
2321 * Make ACK acceptable to originator of segment.
2322 * Don't bother to respond if destination was broadcast/multicast.
2323 */
2324 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
2325 goto drop;
2326 if (isipv6) {
2327 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2328 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2329 goto drop;
2330 } else {
2331 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2332 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2333 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2334 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2335 goto drop;
2336 }
2337 /* IPv6 anycast check is done at tcp6_input() */
2338
2339 /*
2340 * Perform bandwidth limiting.
2341 */
2342 if (badport_bandlim(rstreason) < 0)
2343 goto drop;
2344
2345#ifdef TCPDEBUG
2346 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2347 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2348 &tcp_savetcp, 0);
2349#endif
2350
2351 if (tp)
2352 INP_UNLOCK(inp);
2353
2354 if (thflags & TH_ACK)
2355 /* mtod() below is safe as long as hdr dropping is delayed */
2356 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2357 TH_RST);
2358 else {
2359 if (thflags & TH_SYN)
2360 tlen++;
2361 /* mtod() below is safe as long as hdr dropping is delayed */
2362 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
2363 (tcp_seq)0, TH_RST|TH_ACK);
2364 }
2365 if (headlocked)
2366 INP_INFO_WUNLOCK(&tcbinfo);
2367 return;
2368
2369drop:
2370 /*
2371 * Drop space held by incoming segment and return.
2372 */
2373#ifdef TCPDEBUG
2374 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2375 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2376 &tcp_savetcp, 0);
2377#endif
2378 if (tp)
2379 INP_UNLOCK(inp);
2380 m_freem(m);
2381 if (headlocked)
2382 INP_INFO_WUNLOCK(&tcbinfo);
2383 return;
2384}
2385
2386/*
2387 * Parse TCP options and place in tcpopt.
2388 */
2389static void
2390tcp_dooptions(to, cp, cnt, is_syn)
2391 struct tcpopt *to;
2392 u_char *cp;
2393 int cnt;
2394 int is_syn;
2395{
2396 int opt, optlen;
2397
2398 to->to_flags = 0;
2399 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2400 opt = cp[0];
2401 if (opt == TCPOPT_EOL)
2402 break;
2403 if (opt == TCPOPT_NOP)
2404 optlen = 1;
2405 else {
2406 if (cnt < 2)
2407 break;
2408 optlen = cp[1];
2409 if (optlen < 2 || optlen > cnt)
2410 break;
2411 }
2412 switch (opt) {
2413 case TCPOPT_MAXSEG:
2414 if (optlen != TCPOLEN_MAXSEG)
2415 continue;
2416 if (!is_syn)
2417 continue;
2418 to->to_flags |= TOF_MSS;
2419 bcopy((char *)cp + 2,
2420 (char *)&to->to_mss, sizeof(to->to_mss));
2421 to->to_mss = ntohs(to->to_mss);
2422 break;
2423 case TCPOPT_WINDOW:
2424 if (optlen != TCPOLEN_WINDOW)
2425 continue;
2426 if (! is_syn)
2427 continue;
2428 to->to_flags |= TOF_SCALE;
2429 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2430 break;
2431 case TCPOPT_TIMESTAMP:
2432 if (optlen != TCPOLEN_TIMESTAMP)
2433 continue;
2434 to->to_flags |= TOF_TS;
2435 bcopy((char *)cp + 2,
2436 (char *)&to->to_tsval, sizeof(to->to_tsval));
2437 to->to_tsval = ntohl(to->to_tsval);
2438 bcopy((char *)cp + 6,
2439 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
2440 to->to_tsecr = ntohl(to->to_tsecr);
2441 break;
2442 case TCPOPT_CC:
2443 if (optlen != TCPOLEN_CC)
2444 continue;
2445 to->to_flags |= TOF_CC;
2446 bcopy((char *)cp + 2,
2447 (char *)&to->to_cc, sizeof(to->to_cc));
2448 to->to_cc = ntohl(to->to_cc);
2449 break;
2450 case TCPOPT_CCNEW:
2451 if (optlen != TCPOLEN_CC)
2452 continue;
2453 if (!is_syn)
2454 continue;
2455 to->to_flags |= TOF_CCNEW;
2456 bcopy((char *)cp + 2,
2457 (char *)&to->to_cc, sizeof(to->to_cc));
2458 to->to_cc = ntohl(to->to_cc);
2459 break;
2460 case TCPOPT_CCECHO:
2461 if (optlen != TCPOLEN_CC)
2462 continue;
2463 if (!is_syn)
2464 continue;
2465 to->to_flags |= TOF_CCECHO;
2466 bcopy((char *)cp + 2,
2467 (char *)&to->to_ccecho, sizeof(to->to_ccecho));
2468 to->to_ccecho = ntohl(to->to_ccecho);
2469 break;
2470 default:
2471 continue;
2472 }
2473 }
2474}
2475
2476/*
2477 * Pull out of band byte out of a segment so
2478 * it doesn't appear in the user's data queue.
2479 * It is still reflected in the segment length for
2480 * sequencing purposes.
2481 */
2482static void
2483tcp_pulloutofband(so, th, m, off)
2484 struct socket *so;
2485 struct tcphdr *th;
2486 register struct mbuf *m;
2487 int off; /* delayed to be droped hdrlen */
2488{
2489 int cnt = off + th->th_urp - 1;
2490
2491 while (cnt >= 0) {
2492 if (m->m_len > cnt) {
2493 char *cp = mtod(m, caddr_t) + cnt;
2494 struct tcpcb *tp = sototcpcb(so);
2495
2496 tp->t_iobc = *cp;
2497 tp->t_oobflags |= TCPOOB_HAVEDATA;
2498 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
2499 m->m_len--;
2500 if (m->m_flags & M_PKTHDR)
2501 m->m_pkthdr.len--;
2502 return;
2503 }
2504 cnt -= m->m_len;
2505 m = m->m_next;
2506 if (m == 0)
2507 break;
2508 }
2509 panic("tcp_pulloutofband");
2510}
2511
2512/*
2513 * Collect new round-trip time estimate
2514 * and update averages and current timeout.
2515 */
2516static void
2517tcp_xmit_timer(tp, rtt)
2518 register struct tcpcb *tp;
2519 int rtt;
2520{
2521 register int delta;
2522
2523 tcpstat.tcps_rttupdated++;
2524 tp->t_rttupdated++;
2525 if (tp->t_srtt != 0) {
2526 /*
2527 * srtt is stored as fixed point with 5 bits after the
2528 * binary point (i.e., scaled by 8). The following magic
2529 * is equivalent to the smoothing algorithm in rfc793 with
2530 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2531 * point). Adjust rtt to origin 0.
2532 */
2533 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2534 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2535
2536 if ((tp->t_srtt += delta) <= 0)
2537 tp->t_srtt = 1;
2538
2539 /*
2540 * We accumulate a smoothed rtt variance (actually, a
2541 * smoothed mean difference), then set the retransmit
2542 * timer to smoothed rtt + 4 times the smoothed variance.
2543 * rttvar is stored as fixed point with 4 bits after the
2544 * binary point (scaled by 16). The following is
2545 * equivalent to rfc793 smoothing with an alpha of .75
2546 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2547 * rfc793's wired-in beta.
2548 */
2549 if (delta < 0)
2550 delta = -delta;
2551 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2552 if ((tp->t_rttvar += delta) <= 0)
2553 tp->t_rttvar = 1;
2554 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2555 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2556 } else {
2557 /*
2558 * No rtt measurement yet - use the unsmoothed rtt.
2559 * Set the variance to half the rtt (so our first
2560 * retransmit happens at 3*rtt).
2561 */
2562 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2563 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2564 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2565 }
2566 tp->t_rtttime = 0;
2567 tp->t_rxtshift = 0;
2568
2569 /*
2570 * the retransmit should happen at rtt + 4 * rttvar.
2571 * Because of the way we do the smoothing, srtt and rttvar
2572 * will each average +1/2 tick of bias. When we compute
2573 * the retransmit timer, we want 1/2 tick of rounding and
2574 * 1 extra tick because of +-1/2 tick uncertainty in the
2575 * firing of the timer. The bias will give us exactly the
2576 * 1.5 tick we need. But, because the bias is
2577 * statistical, we have to test that we don't drop below
2578 * the minimum feasible timer (which is 2 ticks).
2579 */
2580 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2581 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2582
2583 /*
2584 * We received an ack for a packet that wasn't retransmitted;
2585 * it is probably safe to discard any error indications we've
2586 * received recently. This isn't quite right, but close enough
2587 * for now (a route might have failed after we sent a segment,
2588 * and the return path might not be symmetrical).
2589 */
2590 tp->t_softerror = 0;
2591}
2592
2593/*
2594 * Determine a reasonable value for maxseg size.
2595 * If the route is known, check route for mtu.
2596 * If none, use an mss that can be handled on the outgoing
2597 * interface without forcing IP to fragment; if bigger than
2598 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2599 * to utilize large mbufs. If no route is found, route has no mtu,
2600 * or the destination isn't local, use a default, hopefully conservative
2601 * size (usually 512 or the default IP max size, but no more than the mtu
2602 * of the interface), as we can't discover anything about intervening
2603 * gateways or networks. We also initialize the congestion/slow start
2604 * window to be a single segment if the destination isn't local.
2605 * While looking at the routing entry, we also initialize other path-dependent
2606 * parameters from pre-set or cached values in the routing entry.
2607 *
2608 * Also take into account the space needed for options that we
2609 * send regularly. Make maxseg shorter by that amount to assure
2610 * that we can send maxseg amount of data even when the options
2611 * are present. Store the upper limit of the length of options plus
2612 * data in maxopd.
2613 *
2614 * NOTE that this routine is only called when we process an incoming
2615 * segment, for outgoing segments only tcp_mssopt is called.
2616 *
2617 * In case of T/TCP, we call this routine during implicit connection
2618 * setup as well (offer = -1), to initialize maxseg from the cached
2619 * MSS of our peer.
2620 */
2621void
2622tcp_mss(tp, offer)
2623 struct tcpcb *tp;
2624 int offer;
2625{
2626 register struct rtentry *rt;
2627 struct ifnet *ifp;
2628 register int rtt, mss;
2629 u_long bufsize;
2630 struct inpcb *inp = tp->t_inpcb;
2631 struct socket *so;
2632 struct rmxp_tao *taop;
2633 int origoffer = offer;
2634#ifdef INET6
2635 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
2636 size_t min_protoh = isipv6 ?
2637 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
2638 sizeof (struct tcpiphdr);
2639#else
2640 const int isipv6 = 0;
2641 const size_t min_protoh = sizeof (struct tcpiphdr);
2642#endif
2643
2644 if (isipv6)
2645 rt = tcp_rtlookup6(&inp->inp_inc);
2646 else
2647 rt = tcp_rtlookup(&inp->inp_inc);
2648 if (rt == NULL) {
2649 tp->t_maxopd = tp->t_maxseg =
2650 isipv6 ? tcp_v6mssdflt : tcp_mssdflt;
2651 return;
2652 }
2653 ifp = rt->rt_ifp;
2654 so = inp->inp_socket;
2655
2656 taop = rmx_taop(rt->rt_rmx);
2657 /*
2658 * Offer == -1 means that we didn't receive SYN yet,
2659 * use cached value in that case;
2660 */
2661 if (offer == -1)
2662 offer = taop->tao_mssopt;
2663 /*
2664 * Offer == 0 means that there was no MSS on the SYN segment,
2665 * in this case we use tcp_mssdflt.
2666 */
2667 if (offer == 0)
2668 offer = isipv6 ? tcp_v6mssdflt : tcp_mssdflt;
2669 else
2670 /*
2671 * Sanity check: make sure that maxopd will be large
2672 * enough to allow some data on segments even is the
2673 * all the option space is used (40bytes). Otherwise
2674 * funny things may happen in tcp_output.
2675 */
2676 offer = max(offer, 64);
2677 taop->tao_mssopt = offer;
2678
2679 /*
2680 * While we're here, check if there's an initial rtt
2681 * or rttvar. Convert from the route-table units
2682 * to scaled multiples of the slow timeout timer.
2683 */
2684 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
2685 /*
2686 * XXX the lock bit for RTT indicates that the value
2687 * is also a minimum value; this is subject to time.
2688 */
2689 if (rt->rt_rmx.rmx_locks & RTV_RTT)
2690 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
2691 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
2692 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
2693 tcpstat.tcps_usedrtt++;
2694 if (rt->rt_rmx.rmx_rttvar) {
2695 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
2696 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
2697 tcpstat.tcps_usedrttvar++;
2698 } else {
2699 /* default variation is +- 1 rtt */
2700 tp->t_rttvar =
2701 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2702 }
2703 TCPT_RANGESET(tp->t_rxtcur,
2704 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2705 tp->t_rttmin, TCPTV_REXMTMAX);
2706 }
2707 /*
2708 * if there's an mtu associated with the route, use it
2709 * else, use the link mtu.
2710 */
2711 if (rt->rt_rmx.rmx_mtu)
2712 mss = rt->rt_rmx.rmx_mtu - min_protoh;
2713 else {
2714#ifdef INET6
2715 mss = (isipv6 ? IN6_LINKMTU(rt->rt_ifp) : ifp->if_mtu)
2716 - min_protoh;
2717#else
2718 mss = ifp->if_mtu - min_protoh;
2719#endif
2720#ifdef INET6
2721 if (isipv6) {
2722 if (!in6_localaddr(&inp->in6p_faddr))
2723 mss = min(mss, tcp_v6mssdflt);
2724 } else
2725#endif
2726 if (!in_localaddr(inp->inp_faddr))
2727 mss = min(mss, tcp_mssdflt);
2728 }
2729 mss = min(mss, offer);
2730 /*
2731 * maxopd stores the maximum length of data AND options
2732 * in a segment; maxseg is the amount of data in a normal
2733 * segment. We need to store this value (maxopd) apart
2734 * from maxseg, because now every segment carries options
2735 * and thus we normally have somewhat less data in segments.
2736 */
2737 tp->t_maxopd = mss;
2738
2739 /*
2740 * In case of T/TCP, origoffer==-1 indicates, that no segments
2741 * were received yet. In this case we just guess, otherwise
2742 * we do the same as before T/TCP.
2743 */
2744 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
2745 (origoffer == -1 ||
2746 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
2747 mss -= TCPOLEN_TSTAMP_APPA;
2748 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
2749 (origoffer == -1 ||
2750 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
2751 mss -= TCPOLEN_CC_APPA;
2752
2753#if (MCLBYTES & (MCLBYTES - 1)) == 0
2754 if (mss > MCLBYTES)
2755 mss &= ~(MCLBYTES-1);
2756#else
2757 if (mss > MCLBYTES)
2758 mss = mss / MCLBYTES * MCLBYTES;
2759#endif
2760 /*
2761 * If there's a pipesize, change the socket buffer
2762 * to that size. Make the socket buffers an integral
2763 * number of mss units; if the mss is larger than
2764 * the socket buffer, decrease the mss.
2765 */
2766#ifdef RTV_SPIPE
2767 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
2768#endif
2769 bufsize = so->so_snd.sb_hiwat;
2770 if (bufsize < mss)
2771 mss = bufsize;
2772 else {
2773 bufsize = roundup(bufsize, mss);
2774 if (bufsize > sb_max)
2775 bufsize = sb_max;
2776 if (bufsize > so->so_snd.sb_hiwat)
2777 (void)sbreserve(&so->so_snd, bufsize, so, NULL);
2778 }
2779 tp->t_maxseg = mss;
2780
2781#ifdef RTV_RPIPE
2782 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
2783#endif
2784 bufsize = so->so_rcv.sb_hiwat;
2785 if (bufsize > mss) {
2786 bufsize = roundup(bufsize, mss);
2787 if (bufsize > sb_max)
2788 bufsize = sb_max;
2789 if (bufsize > so->so_rcv.sb_hiwat)
2790 (void)sbreserve(&so->so_rcv, bufsize, so, NULL);
2791 }
2792
2793 /*
2794 * Set the slow-start flight size depending on whether this
2795 * is a local network or not.
2796 */
2797 if (tcp_do_rfc3390)
2798 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
2799 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
2800 (!isipv6 && in_localaddr(inp->inp_faddr)))
2801 tp->snd_cwnd = mss * ss_fltsz_local;
2802 else
2803 tp->snd_cwnd = mss * ss_fltsz;
2804
2805 if (rt->rt_rmx.rmx_ssthresh) {
2806 /*
2807 * There's some sort of gateway or interface
2808 * buffer limit on the path. Use this to set
2809 * the slow start threshhold, but set the
2810 * threshold to no less than 2*mss.
2811 */
2812 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
2813 tcpstat.tcps_usedssthresh++;
2814 }
2815}
2816
2817/*
2818 * Determine the MSS option to send on an outgoing SYN.
2819 */
2820int
2821tcp_mssopt(tp)
2822 struct tcpcb *tp;
2823{
2824 struct rtentry *rt;
2825#ifdef INET6
2826 int isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
2827 size_t min_protoh = isipv6 ?
2828 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
2829 sizeof (struct tcpiphdr);
2830#else
2831 const int isipv6 = 0;
2832 const size_t min_protoh = sizeof (struct tcpiphdr);
2833#endif
2834
2835 if (isipv6)
2836 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
2837 else
2838 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
2839 if (rt == NULL)
2840 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
2841
2842#ifdef INET6
2843 return (isipv6 ? IN6_LINKMTU(rt->rt_ifp) :
2844 rt->rt_ifp->if_mtu - min_protoh);
2845#else
2846 return (rt->rt_ifp->if_mtu - min_protoh);
2847#endif
2848}
2849
2850
2851/*
2852 * On a partial ack arrives, force the retransmission of the
2853 * next unacknowledged segment. Do not clear tp->t_dupacks.
2854 * By setting snd_nxt to ti_ack, this forces retransmission timer to
2855 * be started again.
2856 */
2857static void
2858tcp_newreno_partial_ack(tp, th)
2859 struct tcpcb *tp;
2860 struct tcphdr *th;
2861{
2862 tcp_seq onxt = tp->snd_nxt;
2863 u_long ocwnd = tp->snd_cwnd;
2864
2865 callout_stop(tp->tt_rexmt);
2866 tp->t_rtttime = 0;
2867 tp->snd_nxt = th->th_ack;
2868 /*
2869 * Set snd_cwnd to one segment beyond acknowledged offset.
2870 * (tp->snd_una has not yet been updated when this function is called.)
2871 */
2872 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una);
2873 tp->t_flags |= TF_ACKNOW;
2874 (void) tcp_output(tp);
2875 tp->snd_cwnd = ocwnd;
2876 if (SEQ_GT(onxt, tp->snd_nxt))
2877 tp->snd_nxt = onxt;
2878 /*
2879 * Partial window deflation. Relies on fact that tp->snd_una
2880 * not updated yet.
2881 */
2882 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
2883}
2884
2885/*
2886 * Returns 1 if the TIME_WAIT state was killed and we should start over,
2887 * looking for a pcb in the listen state. Returns 0 otherwise.
2888 */
2889static int
2890tcp_timewait(tw, to, th, m, tlen)
2891 struct tcptw *tw;
2892 struct tcpopt *to;
2893 struct tcphdr *th;
2894 struct mbuf *m;
2895 int tlen;
2896{
2897 int thflags;
2898 tcp_seq seq;
2899#ifdef INET6
2900 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
2901#else
2902 const int isipv6 = 0;
2903#endif
2904
2905 thflags = th->th_flags;
2906
2907 /*
2908 * NOTE: for FIN_WAIT_2 (to be added later),
2909 * must validate sequence number before accepting RST
2910 */
2911
2912 /*
2913 * If the segment contains RST:
2914 * Drop the segment - see Stevens, vol. 2, p. 964 and
2915 * RFC 1337.
2916 */
2917 if (thflags & TH_RST)
2918 goto drop;
2919
2920 /*
2921 * If segment contains a SYN and CC [not CC.NEW] option:
2922 * if connection duration > MSL, drop packet and send RST;
2923 *
2924 * if SEG.CC > CCrecv then is new SYN.
2925 * Complete close and delete TCPCB. Then reprocess
2926 * segment, hoping to find new TCPCB in LISTEN state;
2927 *
2928 * else must be old SYN; drop it.
2929 * else do normal processing.
2930 */
2931 if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) {
2932 if ((ticks - tw->t_starttime) > tcp_msl)
2933 goto reset;
2934 if (CC_GT(to->to_cc, tw->cc_recv)) {
2935 (void) tcp_twclose(tw, 0);
2936 return (1);
2937 }
2938 goto drop;
2939 }
2940
2941#if 0
2942/* PAWS not needed at the moment */
2943 /*
2944 * RFC 1323 PAWS: If we have a timestamp reply on this segment
2945 * and it's less than ts_recent, drop it.
2946 */
2947 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
2948 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
2949 if ((thflags & TH_ACK) == 0)
2950 goto drop;
2951 goto ack;
2952 }
2953 /*
2954 * ts_recent is never updated because we never accept new segments.
2955 */
2956#endif
2957
2958 /*
2959 * If a new connection request is received
2960 * while in TIME_WAIT, drop the old connection
2961 * and start over if the sequence numbers
2962 * are above the previous ones.
2963 */
2964 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
2965 (void) tcp_twclose(tw, 0);
2966 return (1);
2967 }
2968
2969 /*
2970 * Drop the the segment if it does not contain an ACK.
2971 */
2972 if ((thflags & TH_ACK) == 0)
2973 goto drop;
2974
2975 /*
2976 * Reset the 2MSL timer if this is a duplicate FIN.
2977 */
2978 if (thflags & TH_FIN) {
2979 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
2980 if (seq + 1 == tw->rcv_nxt)
2981 tcp_timer_2msl_reset(tw, 2 * tcp_msl);
2982 }
2983
2984 /*
2985 * Acknowledge the segment if it has data or is not a duplicate ACK.
2986 */
2987 if (thflags != TH_ACK || tlen != 0 ||
2988 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
2989 tcp_twrespond(tw, NULL, m, TH_ACK);
2990 goto drop;
2991
2992reset:
2993 /*
2994 * Generate a RST, dropping incoming segment.
2995 * Make ACK acceptable to originator of segment.
2996 * Don't bother to respond if destination was broadcast/multicast.
2997 */
2998 if (m->m_flags & (M_BCAST|M_MCAST))
2999 goto drop;
3000 if (isipv6) {
3001 struct ip6_hdr *ip6;
3002
3003 /* IPv6 anycast check is done at tcp6_input() */
3004 ip6 = mtod(m, struct ip6_hdr *);
3005 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3006 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3007 goto drop;
3008 } else {
3009 struct ip *ip;
3010
3011 ip = mtod(m, struct ip *);
3012 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3013 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3014 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3015 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3016 goto drop;
3017 }
3018 if (thflags & TH_ACK) {
3019 tcp_respond(NULL,
3020 mtod(m, void *), th, m, 0, th->th_ack, TH_RST);
3021 } else {
3022 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0);
3023 tcp_respond(NULL,
3024 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK);
3025 }
3026 INP_UNLOCK(tw->tw_inpcb);
3027 return (0);
3028
3029drop:
3030 INP_UNLOCK(tw->tw_inpcb);
3031 m_freem(m);
3032 return (0);
3033}
| 2182 sorwakeup(so);
2183 } else {
2184 thflags = tcp_reass(tp, th, &tlen, m);
2185 tp->t_flags |= TF_ACKNOW;
2186 }
2187
2188 /*
2189 * Note the amount of data that peer has sent into
2190 * our window, in order to estimate the sender's
2191 * buffer size.
2192 */
2193 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2194 } else {
2195 m_freem(m);
2196 thflags &= ~TH_FIN;
2197 }
2198
2199 /*
2200 * If FIN is received ACK the FIN and let the user know
2201 * that the connection is closing.
2202 */
2203 if (thflags & TH_FIN) {
2204 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2205 socantrcvmore(so);
2206 /*
2207 * If connection is half-synchronized
2208 * (ie NEEDSYN flag on) then delay ACK,
2209 * so it may be piggybacked when SYN is sent.
2210 * Otherwise, since we received a FIN then no
2211 * more input can be expected, send ACK now.
2212 */
2213 if (tp->t_flags & TF_NEEDSYN)
2214 tp->t_flags |= TF_DELACK;
2215 else
2216 tp->t_flags |= TF_ACKNOW;
2217 tp->rcv_nxt++;
2218 }
2219 switch (tp->t_state) {
2220
2221 /*
2222 * In SYN_RECEIVED and ESTABLISHED STATES
2223 * enter the CLOSE_WAIT state.
2224 */
2225 case TCPS_SYN_RECEIVED:
2226 tp->t_starttime = ticks;
2227 /*FALLTHROUGH*/
2228 case TCPS_ESTABLISHED:
2229 tp->t_state = TCPS_CLOSE_WAIT;
2230 break;
2231
2232 /*
2233 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2234 * enter the CLOSING state.
2235 */
2236 case TCPS_FIN_WAIT_1:
2237 tp->t_state = TCPS_CLOSING;
2238 break;
2239
2240 /*
2241 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2242 * starting the time-wait timer, turning off the other
2243 * standard timers.
2244 */
2245 case TCPS_FIN_WAIT_2:
2246 KASSERT(headlocked == 1, ("headlocked should be 1"));
2247 tcp_twstart(tp);
2248 INP_INFO_WUNLOCK(&tcbinfo);
2249 return;
2250
2251 /*
2252 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2253 */
2254 case TCPS_TIME_WAIT:
2255 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
2256 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2257 tcp_timer_2msl, tp);
2258 break;
2259 }
2260 }
2261 INP_INFO_WUNLOCK(&tcbinfo);
2262#ifdef TCPDEBUG
2263 if (so->so_options & SO_DEBUG)
2264 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
2265 &tcp_savetcp, 0);
2266#endif
2267
2268 /*
2269 * Return any desired output.
2270 */
2271 if (needoutput || (tp->t_flags & TF_ACKNOW))
2272 (void) tcp_output(tp);
2273
2274check_delack:
2275 if (tp->t_flags & TF_DELACK) {
2276 tp->t_flags &= ~TF_DELACK;
2277 callout_reset(tp->tt_delack, tcp_delacktime,
2278 tcp_timer_delack, tp);
2279 }
2280 INP_UNLOCK(inp);
2281 return;
2282
2283dropafterack:
2284 /*
2285 * Generate an ACK dropping incoming segment if it occupies
2286 * sequence space, where the ACK reflects our state.
2287 *
2288 * We can now skip the test for the RST flag since all
2289 * paths to this code happen after packets containing
2290 * RST have been dropped.
2291 *
2292 * In the SYN-RECEIVED state, don't send an ACK unless the
2293 * segment we received passes the SYN-RECEIVED ACK test.
2294 * If it fails send a RST. This breaks the loop in the
2295 * "LAND" DoS attack, and also prevents an ACK storm
2296 * between two listening ports that have been sent forged
2297 * SYN segments, each with the source address of the other.
2298 */
2299 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2300 (SEQ_GT(tp->snd_una, th->th_ack) ||
2301 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2302 rstreason = BANDLIM_RST_OPENPORT;
2303 goto dropwithreset;
2304 }
2305#ifdef TCPDEBUG
2306 if (so->so_options & SO_DEBUG)
2307 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2308 &tcp_savetcp, 0);
2309#endif
2310 KASSERT(headlocked, ("headlocked should be 1"));
2311 INP_INFO_WUNLOCK(&tcbinfo);
2312 m_freem(m);
2313 tp->t_flags |= TF_ACKNOW;
2314 (void) tcp_output(tp);
2315 INP_UNLOCK(inp);
2316 return;
2317
2318dropwithreset:
2319 /*
2320 * Generate a RST, dropping incoming segment.
2321 * Make ACK acceptable to originator of segment.
2322 * Don't bother to respond if destination was broadcast/multicast.
2323 */
2324 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
2325 goto drop;
2326 if (isipv6) {
2327 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2328 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2329 goto drop;
2330 } else {
2331 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2332 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2333 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2334 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2335 goto drop;
2336 }
2337 /* IPv6 anycast check is done at tcp6_input() */
2338
2339 /*
2340 * Perform bandwidth limiting.
2341 */
2342 if (badport_bandlim(rstreason) < 0)
2343 goto drop;
2344
2345#ifdef TCPDEBUG
2346 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2347 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2348 &tcp_savetcp, 0);
2349#endif
2350
2351 if (tp)
2352 INP_UNLOCK(inp);
2353
2354 if (thflags & TH_ACK)
2355 /* mtod() below is safe as long as hdr dropping is delayed */
2356 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2357 TH_RST);
2358 else {
2359 if (thflags & TH_SYN)
2360 tlen++;
2361 /* mtod() below is safe as long as hdr dropping is delayed */
2362 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
2363 (tcp_seq)0, TH_RST|TH_ACK);
2364 }
2365 if (headlocked)
2366 INP_INFO_WUNLOCK(&tcbinfo);
2367 return;
2368
2369drop:
2370 /*
2371 * Drop space held by incoming segment and return.
2372 */
2373#ifdef TCPDEBUG
2374 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2375 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2376 &tcp_savetcp, 0);
2377#endif
2378 if (tp)
2379 INP_UNLOCK(inp);
2380 m_freem(m);
2381 if (headlocked)
2382 INP_INFO_WUNLOCK(&tcbinfo);
2383 return;
2384}
2385
2386/*
2387 * Parse TCP options and place in tcpopt.
2388 */
2389static void
2390tcp_dooptions(to, cp, cnt, is_syn)
2391 struct tcpopt *to;
2392 u_char *cp;
2393 int cnt;
2394 int is_syn;
2395{
2396 int opt, optlen;
2397
2398 to->to_flags = 0;
2399 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2400 opt = cp[0];
2401 if (opt == TCPOPT_EOL)
2402 break;
2403 if (opt == TCPOPT_NOP)
2404 optlen = 1;
2405 else {
2406 if (cnt < 2)
2407 break;
2408 optlen = cp[1];
2409 if (optlen < 2 || optlen > cnt)
2410 break;
2411 }
2412 switch (opt) {
2413 case TCPOPT_MAXSEG:
2414 if (optlen != TCPOLEN_MAXSEG)
2415 continue;
2416 if (!is_syn)
2417 continue;
2418 to->to_flags |= TOF_MSS;
2419 bcopy((char *)cp + 2,
2420 (char *)&to->to_mss, sizeof(to->to_mss));
2421 to->to_mss = ntohs(to->to_mss);
2422 break;
2423 case TCPOPT_WINDOW:
2424 if (optlen != TCPOLEN_WINDOW)
2425 continue;
2426 if (! is_syn)
2427 continue;
2428 to->to_flags |= TOF_SCALE;
2429 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2430 break;
2431 case TCPOPT_TIMESTAMP:
2432 if (optlen != TCPOLEN_TIMESTAMP)
2433 continue;
2434 to->to_flags |= TOF_TS;
2435 bcopy((char *)cp + 2,
2436 (char *)&to->to_tsval, sizeof(to->to_tsval));
2437 to->to_tsval = ntohl(to->to_tsval);
2438 bcopy((char *)cp + 6,
2439 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
2440 to->to_tsecr = ntohl(to->to_tsecr);
2441 break;
2442 case TCPOPT_CC:
2443 if (optlen != TCPOLEN_CC)
2444 continue;
2445 to->to_flags |= TOF_CC;
2446 bcopy((char *)cp + 2,
2447 (char *)&to->to_cc, sizeof(to->to_cc));
2448 to->to_cc = ntohl(to->to_cc);
2449 break;
2450 case TCPOPT_CCNEW:
2451 if (optlen != TCPOLEN_CC)
2452 continue;
2453 if (!is_syn)
2454 continue;
2455 to->to_flags |= TOF_CCNEW;
2456 bcopy((char *)cp + 2,
2457 (char *)&to->to_cc, sizeof(to->to_cc));
2458 to->to_cc = ntohl(to->to_cc);
2459 break;
2460 case TCPOPT_CCECHO:
2461 if (optlen != TCPOLEN_CC)
2462 continue;
2463 if (!is_syn)
2464 continue;
2465 to->to_flags |= TOF_CCECHO;
2466 bcopy((char *)cp + 2,
2467 (char *)&to->to_ccecho, sizeof(to->to_ccecho));
2468 to->to_ccecho = ntohl(to->to_ccecho);
2469 break;
2470 default:
2471 continue;
2472 }
2473 }
2474}
2475
2476/*
2477 * Pull out of band byte out of a segment so
2478 * it doesn't appear in the user's data queue.
2479 * It is still reflected in the segment length for
2480 * sequencing purposes.
2481 */
2482static void
2483tcp_pulloutofband(so, th, m, off)
2484 struct socket *so;
2485 struct tcphdr *th;
2486 register struct mbuf *m;
2487 int off; /* delayed to be droped hdrlen */
2488{
2489 int cnt = off + th->th_urp - 1;
2490
2491 while (cnt >= 0) {
2492 if (m->m_len > cnt) {
2493 char *cp = mtod(m, caddr_t) + cnt;
2494 struct tcpcb *tp = sototcpcb(so);
2495
2496 tp->t_iobc = *cp;
2497 tp->t_oobflags |= TCPOOB_HAVEDATA;
2498 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
2499 m->m_len--;
2500 if (m->m_flags & M_PKTHDR)
2501 m->m_pkthdr.len--;
2502 return;
2503 }
2504 cnt -= m->m_len;
2505 m = m->m_next;
2506 if (m == 0)
2507 break;
2508 }
2509 panic("tcp_pulloutofband");
2510}
2511
2512/*
2513 * Collect new round-trip time estimate
2514 * and update averages and current timeout.
2515 */
2516static void
2517tcp_xmit_timer(tp, rtt)
2518 register struct tcpcb *tp;
2519 int rtt;
2520{
2521 register int delta;
2522
2523 tcpstat.tcps_rttupdated++;
2524 tp->t_rttupdated++;
2525 if (tp->t_srtt != 0) {
2526 /*
2527 * srtt is stored as fixed point with 5 bits after the
2528 * binary point (i.e., scaled by 8). The following magic
2529 * is equivalent to the smoothing algorithm in rfc793 with
2530 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2531 * point). Adjust rtt to origin 0.
2532 */
2533 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2534 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2535
2536 if ((tp->t_srtt += delta) <= 0)
2537 tp->t_srtt = 1;
2538
2539 /*
2540 * We accumulate a smoothed rtt variance (actually, a
2541 * smoothed mean difference), then set the retransmit
2542 * timer to smoothed rtt + 4 times the smoothed variance.
2543 * rttvar is stored as fixed point with 4 bits after the
2544 * binary point (scaled by 16). The following is
2545 * equivalent to rfc793 smoothing with an alpha of .75
2546 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2547 * rfc793's wired-in beta.
2548 */
2549 if (delta < 0)
2550 delta = -delta;
2551 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2552 if ((tp->t_rttvar += delta) <= 0)
2553 tp->t_rttvar = 1;
2554 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2555 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2556 } else {
2557 /*
2558 * No rtt measurement yet - use the unsmoothed rtt.
2559 * Set the variance to half the rtt (so our first
2560 * retransmit happens at 3*rtt).
2561 */
2562 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2563 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2564 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2565 }
2566 tp->t_rtttime = 0;
2567 tp->t_rxtshift = 0;
2568
2569 /*
2570 * the retransmit should happen at rtt + 4 * rttvar.
2571 * Because of the way we do the smoothing, srtt and rttvar
2572 * will each average +1/2 tick of bias. When we compute
2573 * the retransmit timer, we want 1/2 tick of rounding and
2574 * 1 extra tick because of +-1/2 tick uncertainty in the
2575 * firing of the timer. The bias will give us exactly the
2576 * 1.5 tick we need. But, because the bias is
2577 * statistical, we have to test that we don't drop below
2578 * the minimum feasible timer (which is 2 ticks).
2579 */
2580 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2581 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2582
2583 /*
2584 * We received an ack for a packet that wasn't retransmitted;
2585 * it is probably safe to discard any error indications we've
2586 * received recently. This isn't quite right, but close enough
2587 * for now (a route might have failed after we sent a segment,
2588 * and the return path might not be symmetrical).
2589 */
2590 tp->t_softerror = 0;
2591}
2592
2593/*
2594 * Determine a reasonable value for maxseg size.
2595 * If the route is known, check route for mtu.
2596 * If none, use an mss that can be handled on the outgoing
2597 * interface without forcing IP to fragment; if bigger than
2598 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2599 * to utilize large mbufs. If no route is found, route has no mtu,
2600 * or the destination isn't local, use a default, hopefully conservative
2601 * size (usually 512 or the default IP max size, but no more than the mtu
2602 * of the interface), as we can't discover anything about intervening
2603 * gateways or networks. We also initialize the congestion/slow start
2604 * window to be a single segment if the destination isn't local.
2605 * While looking at the routing entry, we also initialize other path-dependent
2606 * parameters from pre-set or cached values in the routing entry.
2607 *
2608 * Also take into account the space needed for options that we
2609 * send regularly. Make maxseg shorter by that amount to assure
2610 * that we can send maxseg amount of data even when the options
2611 * are present. Store the upper limit of the length of options plus
2612 * data in maxopd.
2613 *
2614 * NOTE that this routine is only called when we process an incoming
2615 * segment, for outgoing segments only tcp_mssopt is called.
2616 *
2617 * In case of T/TCP, we call this routine during implicit connection
2618 * setup as well (offer = -1), to initialize maxseg from the cached
2619 * MSS of our peer.
2620 */
2621void
2622tcp_mss(tp, offer)
2623 struct tcpcb *tp;
2624 int offer;
2625{
2626 register struct rtentry *rt;
2627 struct ifnet *ifp;
2628 register int rtt, mss;
2629 u_long bufsize;
2630 struct inpcb *inp = tp->t_inpcb;
2631 struct socket *so;
2632 struct rmxp_tao *taop;
2633 int origoffer = offer;
2634#ifdef INET6
2635 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
2636 size_t min_protoh = isipv6 ?
2637 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
2638 sizeof (struct tcpiphdr);
2639#else
2640 const int isipv6 = 0;
2641 const size_t min_protoh = sizeof (struct tcpiphdr);
2642#endif
2643
2644 if (isipv6)
2645 rt = tcp_rtlookup6(&inp->inp_inc);
2646 else
2647 rt = tcp_rtlookup(&inp->inp_inc);
2648 if (rt == NULL) {
2649 tp->t_maxopd = tp->t_maxseg =
2650 isipv6 ? tcp_v6mssdflt : tcp_mssdflt;
2651 return;
2652 }
2653 ifp = rt->rt_ifp;
2654 so = inp->inp_socket;
2655
2656 taop = rmx_taop(rt->rt_rmx);
2657 /*
2658 * Offer == -1 means that we didn't receive SYN yet,
2659 * use cached value in that case;
2660 */
2661 if (offer == -1)
2662 offer = taop->tao_mssopt;
2663 /*
2664 * Offer == 0 means that there was no MSS on the SYN segment,
2665 * in this case we use tcp_mssdflt.
2666 */
2667 if (offer == 0)
2668 offer = isipv6 ? tcp_v6mssdflt : tcp_mssdflt;
2669 else
2670 /*
2671 * Sanity check: make sure that maxopd will be large
2672 * enough to allow some data on segments even is the
2673 * all the option space is used (40bytes). Otherwise
2674 * funny things may happen in tcp_output.
2675 */
2676 offer = max(offer, 64);
2677 taop->tao_mssopt = offer;
2678
2679 /*
2680 * While we're here, check if there's an initial rtt
2681 * or rttvar. Convert from the route-table units
2682 * to scaled multiples of the slow timeout timer.
2683 */
2684 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
2685 /*
2686 * XXX the lock bit for RTT indicates that the value
2687 * is also a minimum value; this is subject to time.
2688 */
2689 if (rt->rt_rmx.rmx_locks & RTV_RTT)
2690 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
2691 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
2692 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
2693 tcpstat.tcps_usedrtt++;
2694 if (rt->rt_rmx.rmx_rttvar) {
2695 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
2696 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
2697 tcpstat.tcps_usedrttvar++;
2698 } else {
2699 /* default variation is +- 1 rtt */
2700 tp->t_rttvar =
2701 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2702 }
2703 TCPT_RANGESET(tp->t_rxtcur,
2704 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2705 tp->t_rttmin, TCPTV_REXMTMAX);
2706 }
2707 /*
2708 * if there's an mtu associated with the route, use it
2709 * else, use the link mtu.
2710 */
2711 if (rt->rt_rmx.rmx_mtu)
2712 mss = rt->rt_rmx.rmx_mtu - min_protoh;
2713 else {
2714#ifdef INET6
2715 mss = (isipv6 ? IN6_LINKMTU(rt->rt_ifp) : ifp->if_mtu)
2716 - min_protoh;
2717#else
2718 mss = ifp->if_mtu - min_protoh;
2719#endif
2720#ifdef INET6
2721 if (isipv6) {
2722 if (!in6_localaddr(&inp->in6p_faddr))
2723 mss = min(mss, tcp_v6mssdflt);
2724 } else
2725#endif
2726 if (!in_localaddr(inp->inp_faddr))
2727 mss = min(mss, tcp_mssdflt);
2728 }
2729 mss = min(mss, offer);
2730 /*
2731 * maxopd stores the maximum length of data AND options
2732 * in a segment; maxseg is the amount of data in a normal
2733 * segment. We need to store this value (maxopd) apart
2734 * from maxseg, because now every segment carries options
2735 * and thus we normally have somewhat less data in segments.
2736 */
2737 tp->t_maxopd = mss;
2738
2739 /*
2740 * In case of T/TCP, origoffer==-1 indicates, that no segments
2741 * were received yet. In this case we just guess, otherwise
2742 * we do the same as before T/TCP.
2743 */
2744 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
2745 (origoffer == -1 ||
2746 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
2747 mss -= TCPOLEN_TSTAMP_APPA;
2748 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
2749 (origoffer == -1 ||
2750 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
2751 mss -= TCPOLEN_CC_APPA;
2752
2753#if (MCLBYTES & (MCLBYTES - 1)) == 0
2754 if (mss > MCLBYTES)
2755 mss &= ~(MCLBYTES-1);
2756#else
2757 if (mss > MCLBYTES)
2758 mss = mss / MCLBYTES * MCLBYTES;
2759#endif
2760 /*
2761 * If there's a pipesize, change the socket buffer
2762 * to that size. Make the socket buffers an integral
2763 * number of mss units; if the mss is larger than
2764 * the socket buffer, decrease the mss.
2765 */
2766#ifdef RTV_SPIPE
2767 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
2768#endif
2769 bufsize = so->so_snd.sb_hiwat;
2770 if (bufsize < mss)
2771 mss = bufsize;
2772 else {
2773 bufsize = roundup(bufsize, mss);
2774 if (bufsize > sb_max)
2775 bufsize = sb_max;
2776 if (bufsize > so->so_snd.sb_hiwat)
2777 (void)sbreserve(&so->so_snd, bufsize, so, NULL);
2778 }
2779 tp->t_maxseg = mss;
2780
2781#ifdef RTV_RPIPE
2782 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
2783#endif
2784 bufsize = so->so_rcv.sb_hiwat;
2785 if (bufsize > mss) {
2786 bufsize = roundup(bufsize, mss);
2787 if (bufsize > sb_max)
2788 bufsize = sb_max;
2789 if (bufsize > so->so_rcv.sb_hiwat)
2790 (void)sbreserve(&so->so_rcv, bufsize, so, NULL);
2791 }
2792
2793 /*
2794 * Set the slow-start flight size depending on whether this
2795 * is a local network or not.
2796 */
2797 if (tcp_do_rfc3390)
2798 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
2799 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
2800 (!isipv6 && in_localaddr(inp->inp_faddr)))
2801 tp->snd_cwnd = mss * ss_fltsz_local;
2802 else
2803 tp->snd_cwnd = mss * ss_fltsz;
2804
2805 if (rt->rt_rmx.rmx_ssthresh) {
2806 /*
2807 * There's some sort of gateway or interface
2808 * buffer limit on the path. Use this to set
2809 * the slow start threshhold, but set the
2810 * threshold to no less than 2*mss.
2811 */
2812 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
2813 tcpstat.tcps_usedssthresh++;
2814 }
2815}
2816
2817/*
2818 * Determine the MSS option to send on an outgoing SYN.
2819 */
2820int
2821tcp_mssopt(tp)
2822 struct tcpcb *tp;
2823{
2824 struct rtentry *rt;
2825#ifdef INET6
2826 int isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
2827 size_t min_protoh = isipv6 ?
2828 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
2829 sizeof (struct tcpiphdr);
2830#else
2831 const int isipv6 = 0;
2832 const size_t min_protoh = sizeof (struct tcpiphdr);
2833#endif
2834
2835 if (isipv6)
2836 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
2837 else
2838 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
2839 if (rt == NULL)
2840 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
2841
2842#ifdef INET6
2843 return (isipv6 ? IN6_LINKMTU(rt->rt_ifp) :
2844 rt->rt_ifp->if_mtu - min_protoh);
2845#else
2846 return (rt->rt_ifp->if_mtu - min_protoh);
2847#endif
2848}
2849
2850
2851/*
2852 * On a partial ack arrives, force the retransmission of the
2853 * next unacknowledged segment. Do not clear tp->t_dupacks.
2854 * By setting snd_nxt to ti_ack, this forces retransmission timer to
2855 * be started again.
2856 */
2857static void
2858tcp_newreno_partial_ack(tp, th)
2859 struct tcpcb *tp;
2860 struct tcphdr *th;
2861{
2862 tcp_seq onxt = tp->snd_nxt;
2863 u_long ocwnd = tp->snd_cwnd;
2864
2865 callout_stop(tp->tt_rexmt);
2866 tp->t_rtttime = 0;
2867 tp->snd_nxt = th->th_ack;
2868 /*
2869 * Set snd_cwnd to one segment beyond acknowledged offset.
2870 * (tp->snd_una has not yet been updated when this function is called.)
2871 */
2872 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una);
2873 tp->t_flags |= TF_ACKNOW;
2874 (void) tcp_output(tp);
2875 tp->snd_cwnd = ocwnd;
2876 if (SEQ_GT(onxt, tp->snd_nxt))
2877 tp->snd_nxt = onxt;
2878 /*
2879 * Partial window deflation. Relies on fact that tp->snd_una
2880 * not updated yet.
2881 */
2882 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
2883}
2884
2885/*
2886 * Returns 1 if the TIME_WAIT state was killed and we should start over,
2887 * looking for a pcb in the listen state. Returns 0 otherwise.
2888 */
2889static int
2890tcp_timewait(tw, to, th, m, tlen)
2891 struct tcptw *tw;
2892 struct tcpopt *to;
2893 struct tcphdr *th;
2894 struct mbuf *m;
2895 int tlen;
2896{
2897 int thflags;
2898 tcp_seq seq;
2899#ifdef INET6
2900 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
2901#else
2902 const int isipv6 = 0;
2903#endif
2904
2905 thflags = th->th_flags;
2906
2907 /*
2908 * NOTE: for FIN_WAIT_2 (to be added later),
2909 * must validate sequence number before accepting RST
2910 */
2911
2912 /*
2913 * If the segment contains RST:
2914 * Drop the segment - see Stevens, vol. 2, p. 964 and
2915 * RFC 1337.
2916 */
2917 if (thflags & TH_RST)
2918 goto drop;
2919
2920 /*
2921 * If segment contains a SYN and CC [not CC.NEW] option:
2922 * if connection duration > MSL, drop packet and send RST;
2923 *
2924 * if SEG.CC > CCrecv then is new SYN.
2925 * Complete close and delete TCPCB. Then reprocess
2926 * segment, hoping to find new TCPCB in LISTEN state;
2927 *
2928 * else must be old SYN; drop it.
2929 * else do normal processing.
2930 */
2931 if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) {
2932 if ((ticks - tw->t_starttime) > tcp_msl)
2933 goto reset;
2934 if (CC_GT(to->to_cc, tw->cc_recv)) {
2935 (void) tcp_twclose(tw, 0);
2936 return (1);
2937 }
2938 goto drop;
2939 }
2940
2941#if 0
2942/* PAWS not needed at the moment */
2943 /*
2944 * RFC 1323 PAWS: If we have a timestamp reply on this segment
2945 * and it's less than ts_recent, drop it.
2946 */
2947 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
2948 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
2949 if ((thflags & TH_ACK) == 0)
2950 goto drop;
2951 goto ack;
2952 }
2953 /*
2954 * ts_recent is never updated because we never accept new segments.
2955 */
2956#endif
2957
2958 /*
2959 * If a new connection request is received
2960 * while in TIME_WAIT, drop the old connection
2961 * and start over if the sequence numbers
2962 * are above the previous ones.
2963 */
2964 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
2965 (void) tcp_twclose(tw, 0);
2966 return (1);
2967 }
2968
2969 /*
2970 * Drop the the segment if it does not contain an ACK.
2971 */
2972 if ((thflags & TH_ACK) == 0)
2973 goto drop;
2974
2975 /*
2976 * Reset the 2MSL timer if this is a duplicate FIN.
2977 */
2978 if (thflags & TH_FIN) {
2979 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
2980 if (seq + 1 == tw->rcv_nxt)
2981 tcp_timer_2msl_reset(tw, 2 * tcp_msl);
2982 }
2983
2984 /*
2985 * Acknowledge the segment if it has data or is not a duplicate ACK.
2986 */
2987 if (thflags != TH_ACK || tlen != 0 ||
2988 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
2989 tcp_twrespond(tw, NULL, m, TH_ACK);
2990 goto drop;
2991
2992reset:
2993 /*
2994 * Generate a RST, dropping incoming segment.
2995 * Make ACK acceptable to originator of segment.
2996 * Don't bother to respond if destination was broadcast/multicast.
2997 */
2998 if (m->m_flags & (M_BCAST|M_MCAST))
2999 goto drop;
3000 if (isipv6) {
3001 struct ip6_hdr *ip6;
3002
3003 /* IPv6 anycast check is done at tcp6_input() */
3004 ip6 = mtod(m, struct ip6_hdr *);
3005 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3006 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3007 goto drop;
3008 } else {
3009 struct ip *ip;
3010
3011 ip = mtod(m, struct ip *);
3012 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3013 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3014 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3015 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3016 goto drop;
3017 }
3018 if (thflags & TH_ACK) {
3019 tcp_respond(NULL,
3020 mtod(m, void *), th, m, 0, th->th_ack, TH_RST);
3021 } else {
3022 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0);
3023 tcp_respond(NULL,
3024 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK);
3025 }
3026 INP_UNLOCK(tw->tw_inpcb);
3027 return (0);
3028
3029drop:
3030 INP_UNLOCK(tw->tw_inpcb);
3031 m_freem(m);
3032 return (0);
3033}
|