/* * Copyright (c) 2000-2012 Apple Inc. All rights reserved. * * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. The rights granted to you under the License * may not be used to create, or enable the creation or redistribution of, * unlawful or unlicensed copies of an Apple operating system, or to * circumvent, violate, or enable the circumvention or violation of, any * terms of an Apple operating system software license agreement. * * Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ */ /* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.16 2001/08/22 00:59:12 silby Exp $ */ /* * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce * support for mandatory and extensible security protections. This notice * is included in support of clause 2.2 (b) of the Apple Public License, * Version 2.0. */ #include #include #include #include #include #include #include /* for proc0 declaration */ #include #include #include #include #include #include /* before tcp_seq.h, for tcp_random18() */ #include #include #include #include #include #include #include #include #include /* for ICMP_BANDLIM */ #include #include /* for ICMP_BANDLIM */ #include #include #include #if INET6 #include #include #include #include #include #endif #include #include #include #include #include #include #include #if INET6 #include #endif #include #if TCPDEBUG #include u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ struct tcphdr tcp_savetcp; #endif /* TCPDEBUG */ #if IPSEC #include #if INET6 #include #endif #include #endif /*IPSEC*/ #if CONFIG_MACF_NET || CONFIG_MACF_SOCKET #include #endif /* CONFIG_MACF_NET || CONFIG_MACF_SOCKET */ #include #include #define DBG_LAYER_BEG NETDBG_CODE(DBG_NETTCP, 0) #define DBG_LAYER_END NETDBG_CODE(DBG_NETTCP, 2) #define DBG_FNC_TCP_INPUT NETDBG_CODE(DBG_NETTCP, (3 << 8)) #define DBG_FNC_TCP_NEWCONN NETDBG_CODE(DBG_NETTCP, (7 << 8)) static int tcprexmtthresh = 2; tcp_cc tcp_ccgen; #if IPSEC extern int ipsec_bypass; #endif extern int32_t total_sbmb_cnt; struct tcpstat tcpstat; static int log_in_vain = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW | CTLFLAG_LOCKED, &log_in_vain, 0, "Log all incoming TCP connections"); static int blackhole = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW | CTLFLAG_LOCKED, &blackhole, 0, "Do not send RST when dropping refused connections"); int tcp_delack_enabled = 3; SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_delack_enabled, 0, "Delay ACK to try and piggyback it onto a data packet"); int tcp_lq_overflow = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcp_lq_overflow, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_lq_overflow, 0, "Listen Queue Overflow"); int tcp_recv_bg = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbg, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_recv_bg, 0, "Receive background"); #if TCP_DROP_SYNFIN static int drop_synfin = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW | CTLFLAG_LOCKED, &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); #endif SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW|CTLFLAG_LOCKED, 0, "TCP Segment Reassembly Queue"); __private_extern__ int tcp_reass_maxseg = 0; SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_reass_maxseg, 0, "Global maximum number of TCP Segments in Reassembly Queue"); __private_extern__ int tcp_reass_qsize = 0; SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD | CTLFLAG_LOCKED, &tcp_reass_qsize, 0, "Global number of TCP Segments currently in Reassembly Queue"); static int tcp_reass_overflows = 0; SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD | CTLFLAG_LOCKED, &tcp_reass_overflows, 0, "Global number of TCP Segment Reassembly Queue Overflows"); __private_extern__ int slowlink_wsize = 8192; SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowlink_wsize, CTLFLAG_RW | CTLFLAG_LOCKED, &slowlink_wsize, 0, "Maximum advertised window size for slowlink"); int maxseg_unacked = 8; SYSCTL_INT(_net_inet_tcp, OID_AUTO, maxseg_unacked, CTLFLAG_RW | CTLFLAG_LOCKED, &maxseg_unacked, 0, "Maximum number of outstanding segments left unacked"); int tcp_do_rfc3465 = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_do_rfc3465, 0, ""); int tcp_do_rfc3465_lim2 = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465_lim2, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_do_rfc3465_lim2, 0, "Appropriate bytes counting w/ L=2*SMSS"); int rtt_samples_per_slot = 20; SYSCTL_INT(_net_inet_tcp, OID_AUTO, rtt_samples_per_slot, CTLFLAG_RW | CTLFLAG_LOCKED, &rtt_samples_per_slot, 0, "Number of RTT samples stored for rtt history"); int tcp_allowed_iaj = ALLOWED_IAJ; SYSCTL_INT(_net_inet_tcp, OID_AUTO, recv_allowed_iaj, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_allowed_iaj, 0, "Allowed inter-packet arrival jiter"); int tcp_acc_iaj_high_thresh = ACC_IAJ_HIGH_THRESH; SYSCTL_INT(_net_inet_tcp, OID_AUTO, acc_iaj_high_thresh, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_acc_iaj_high_thresh, 0, "Used in calculating maximum accumulated IAJ"); u_int32_t tcp_do_autorcvbuf = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, doautorcvbuf, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_do_autorcvbuf, 0, "Enable automatic socket buffer tuning"); u_int32_t tcp_autorcvbuf_inc_shift = 3; SYSCTL_INT(_net_inet_tcp, OID_AUTO, autorcvbufincshift, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_autorcvbuf_inc_shift, 0, "Shift for increment in receive socket buffer size"); u_int32_t tcp_autorcvbuf_max = 512 * 1024; SYSCTL_INT(_net_inet_tcp, OID_AUTO, autorcvbufmax, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_autorcvbuf_max, 0, "Maximum receive socket buffer size"); int sw_lro = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, lro, CTLFLAG_RW | CTLFLAG_LOCKED, &sw_lro, 0, "Used to coalesce TCP packets"); int lrodebug = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, lrodbg, CTLFLAG_RW | CTLFLAG_LOCKED, &lrodebug, 0, "Used to debug SW LRO"); int lro_start = 3; SYSCTL_INT(_net_inet_tcp, OID_AUTO, lro_startcnt, CTLFLAG_RW | CTLFLAG_LOCKED, &lro_start, 0, "Segments for starting LRO computed as power of 2"); extern int tcp_do_autosendbuf; #if CONFIG_IFEF_NOWINDOWSCALE int tcp_obey_ifef_nowindowscale = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, obey_ifef_nowindowscale, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_obey_ifef_nowindowscale, 0, ""); #endif /* This limit will determine when the receive socket buffer tuning will * kick in. Currently it will start when the bw*delay measured in * last RTT is more than half of the current hiwat on the buffer. */ uint32_t tcp_rbuf_hiwat_shift = 1; /* This limit will determine when the socket buffer will be increased * to accommodate an application reading slowly. When the amount of * space left in the buffer is less than one forth of the bw*delay * measured in last RTT. */ uint32_t tcp_rbuf_win_shift = 2; extern int tcp_TCPTV_MIN; extern int tcp_acc_iaj_high; extern int tcp_acc_iaj_react_limit; extern struct zone *tcp_reass_zone; u_int32_t tcp_now; struct timeval tcp_uptime; /* uptime when tcp_now was last updated */ lck_spin_t *tcp_uptime_lock; /* Used to sychronize updates to tcp_now */ struct inpcbhead tcb; #define tcb6 tcb /* for KAME src sync over BSD*'s */ struct inpcbinfo tcbinfo; static void tcp_dooptions(struct tcpcb *, u_char *, int, struct tcphdr *, struct tcpopt *, unsigned int); static void tcp_pulloutofband(struct socket *, struct tcphdr *, struct mbuf *, int); static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, struct mbuf *); static void tcp_xmit_timer(struct tcpcb *, int); static inline unsigned int tcp_maxmtu(struct rtentry *); static inline int tcp_stretch_ack_enable(struct tcpcb *tp); #if TRAFFIC_MGT static inline void update_iaj_state(struct tcpcb *tp, uint32_t tlen, int reset_size); void compute_iaj(struct tcpcb *tp); #endif /* TRAFFIC_MGT */ #if INET6 static inline unsigned int tcp_maxmtu6(struct rtentry *); #endif static void tcp_sbrcv_grow(struct tcpcb *tp, struct sockbuf *sb, struct tcpopt *to, u_int32_t tlen); void tcp_sbrcv_trim(struct tcpcb *tp, struct sockbuf *sb); static void tcp_sbsnd_trim(struct sockbuf *sbsnd); static inline void tcp_sbrcv_tstmp_check(struct tcpcb *tp); static inline void tcp_sbrcv_reserve(struct tcpcb *tp, struct sockbuf *sb, u_int32_t newsize, u_int32_t idealsize); #define TCPTV_RCVNOTS_QUANTUM 100 #define TCP_RCVNOTS_BYTELEVEL 204800 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ #if INET6 #define ND6_HINT(tp) \ do { \ if ((tp) && (tp)->t_inpcb && \ ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \ (tp)->t_inpcb->in6p_route.ro_rt) \ nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ } while (0) #else #define ND6_HINT(tp) #endif extern void add_to_time_wait(struct tcpcb *, uint32_t delay); extern void postevent(struct socket *, struct sockbuf *, int); extern void ipfwsyslog( int level, const char *format,...); extern int ChkAddressOK( __uint32_t dstaddr, __uint32_t srcaddr ); extern int fw_verbose; #if IPFIREWALL #define log_in_vain_log( a ) { \ if ( (log_in_vain == 3 ) && (fw_verbose == 2)) { /* Apple logging, log to ipfw.log */ \ ipfwsyslog a ; \ } \ else log a ; \ } #else #define log_in_vain_log( a ) { log a; } #endif int tcp_rcvunackwin = TCPTV_UNACKWIN; int tcp_maxrcvidle = TCPTV_MAXRCVIDLE; int tcp_rcvsspktcnt = TCP_RCV_SS_PKTCOUNT; SYSCTL_INT(_net_inet_tcp, OID_AUTO, rcvsspktcnt, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_rcvsspktcnt, 0, "packets to be seen before receiver stretches acks"); #define DELAY_ACK(tp, th) (CC_ALGO(tp)->delay_ack != NULL && CC_ALGO(tp)->delay_ack(tp, th)) static int tcp_dropdropablreq(struct socket *head); static void tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th); static void update_base_rtt(struct tcpcb *tp, uint32_t rtt); uint32_t get_base_rtt(struct tcpcb *tp); void tcp_set_background_cc(struct socket *so); void tcp_set_foreground_cc(struct socket *so); static void tcp_set_new_cc(struct socket *so, uint16_t cc_index); static void tcp_bwmeas_check(struct tcpcb *tp); #if TRAFFIC_MGT void reset_acc_iaj(struct tcpcb *tp) { tp->acc_iaj = 0; tp->iaj_rwintop = 0; CLEAR_IAJ_STATE(tp); } static inline void update_iaj_state(struct tcpcb *tp, uint32_t size, int rst_size) { if (rst_size > 0) tp->iaj_size = 0; if (tp->iaj_size == 0 || size >= tp->iaj_size) { tp->iaj_size = size; tp->iaj_rcv_ts = tcp_now; tp->iaj_small_pkt = 0; } } /* For every 32 bit unsigned integer(v), this function will find the * largest integer n such that (n*n <= v). This takes at most 16 iterations * irrespective of the value of v and does not involve multiplications. */ static inline int isqrt(unsigned int val) { unsigned int sqrt_cache[11] = {0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100}; unsigned int temp, g=0, b=0x8000, bshft=15; if ( val <= 100) { for (g = 0; g <= 10; ++g) { if (sqrt_cache[g] > val) { g--; break; } else if (sqrt_cache[g] == val) { break; } } } else { do { temp = (((g << 1) + b) << (bshft--)); if (val >= temp) { g += b; val -= temp; } b >>= 1; } while ( b > 0 && val > 0); } return(g); } void compute_iaj(struct tcpcb *tp) { /* When accumulated IAJ reaches MAX_ACC_IAJ in milliseconds, throttle the * receive window to a minimum of MIN_IAJ_WIN packets */ #define MAX_ACC_IAJ (tcp_acc_iaj_high_thresh + tcp_acc_iaj_react_limit) uint32_t allowed_iaj, acc_iaj = 0; uint32_t cur_iaj = tcp_now - tp->iaj_rcv_ts; uint32_t mean, temp; int32_t cur_iaj_dev; cur_iaj_dev = (cur_iaj - tp->avg_iaj); /* Allow a jitter of "allowed_iaj" milliseconds. Some connections may have a * constant jitter more than that. We detect this by using * standard deviation. */ allowed_iaj = tp->avg_iaj + tp->std_dev_iaj; if (allowed_iaj < tcp_allowed_iaj) allowed_iaj = tcp_allowed_iaj; /* Initially when the connection starts, the senders congestion window * is small. During this period we avoid throttling a connection because * we do not have a good starting point for allowed_iaj. IAJ_IGNORE_PKTCNT * is used to quietly gloss over the first few packets. */ if (tp->iaj_pktcnt > IAJ_IGNORE_PKTCNT) { if ( cur_iaj <= allowed_iaj ) { if (tp->acc_iaj >= 2) acc_iaj = tp->acc_iaj - 2; else acc_iaj = 0; } else { acc_iaj = tp->acc_iaj + (cur_iaj - allowed_iaj); } if (acc_iaj > MAX_ACC_IAJ) acc_iaj = MAX_ACC_IAJ; tp->acc_iaj = acc_iaj; } /* Compute weighted average where the history has a weight of * 15 out of 16 and the current value has a weight of 1 out of 16. * This will make the short-term measurements have more weight. */ tp->avg_iaj = (((tp->avg_iaj << 4) - tp->avg_iaj) + cur_iaj) >> 4; /* Compute Root-mean-square of deviation where mean is a weighted * average as described above */ temp = tp->std_dev_iaj * tp->std_dev_iaj; mean = (((temp << 4) - temp) + (cur_iaj_dev * cur_iaj_dev)) >> 4; tp->std_dev_iaj = isqrt(mean); DTRACE_TCP3(iaj, struct tcpcb *, tp, uint32_t, cur_iaj, uint32_t, allowed_iaj); return; } #endif /* TRAFFIC_MGT */ /* Check if enough amount of data has been acknowledged since * bw measurement was started */ static void tcp_bwmeas_check(struct tcpcb *tp) { int32_t bw_meas_bytes; uint32_t bw, bytes, elapsed_time; bw_meas_bytes = tp->snd_una - tp->t_bwmeas->bw_start; if ((tp->t_flagsext & TF_BWMEAS_INPROGRESS) != 0 && bw_meas_bytes >= (int32_t)(tp->t_bwmeas->bw_size)) { bytes = bw_meas_bytes; elapsed_time = tcp_now - tp->t_bwmeas->bw_ts; if (elapsed_time > 0) { bw = bytes / elapsed_time; if ( bw > 0) { if (tp->t_bwmeas->bw_sndbw > 0) { tp->t_bwmeas->bw_sndbw = (((tp->t_bwmeas->bw_sndbw << 3) - tp->t_bwmeas->bw_sndbw) + bw) >> 3; } else { tp->t_bwmeas->bw_sndbw = bw; } } } tp->t_flagsext &= ~(TF_BWMEAS_INPROGRESS); } } static int tcp_reass(tp, th, tlenp, m) register struct tcpcb *tp; register struct tcphdr *th; int *tlenp; struct mbuf *m; { struct tseg_qent *q; struct tseg_qent *p = NULL; struct tseg_qent *nq; struct tseg_qent *te = NULL; struct socket *so = tp->t_inpcb->inp_socket; int flags; int dowakeup = 0; /* * Call with th==0 after become established to * force pre-ESTABLISHED data up to user socket. */ if (th == NULL) goto present; /* If the reassembly queue already has entries or if we are going to add * a new one, then the connection has reached a loss state. * Reset the stretch-ack algorithm at this point. */ if ((tp->t_flags & TF_STRETCHACK) != 0) tcp_reset_stretch_ack(tp); /* When the connection reaches a loss state, we need to send more acks * for a period of time so that the sender's congestion window will * open. Wait until we see some packets on the connection before * stretching acks again. */ tp->t_flagsext |= TF_RCVUNACK_WAITSS; tp->rcv_waitforss = 0; #if TRAFFIC_MGT if (tp->acc_iaj > 0) reset_acc_iaj(tp); #endif /* TRAFFIC_MGT */ /* * Limit the number of segments in the reassembly queue to prevent * holding on to too many segments (and thus running out of mbufs). * Make sure to let the missing segment through which caused this * queue. Always keep one global queue entry spare to be able to * process the missing segment. */ if (th->th_seq != tp->rcv_nxt && tcp_reass_qsize + 1 >= tcp_reass_maxseg) { tcp_reass_overflows++; tcpstat.tcps_rcvmemdrop++; m_freem(m); *tlenp = 0; return (0); } /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */ te = (struct tseg_qent *) zalloc_noblock(tcp_reass_zone); if (te == NULL) { tcpstat.tcps_rcvmemdrop++; m_freem(m); return (0); } tcp_reass_qsize++; /* * Find a segment which begins after this one does. */ LIST_FOREACH(q, &tp->t_segq, tqe_q) { if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) break; p = q; } /* * If there is a preceding segment, it may provide some of * our data already. If so, drop the data from the incoming * segment. If it provides all of our data, drop us. */ if (p != NULL) { register int i; /* conversion to int (in i) handles seq wraparound */ i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; if (i > 0) { if (i >= *tlenp) { tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += *tlenp; if (nstat_collect) { nstat_route_rx(tp->t_inpcb->inp_route.ro_rt, 1, *tlenp, NSTAT_RX_FLAG_DUPLICATE); locked_add_64(&tp->t_inpcb->inp_stat->rxpackets, 1); locked_add_64(&tp->t_inpcb->inp_stat->rxbytes, *tlenp); tp->t_stat.rxduplicatebytes += *tlenp; } m_freem(m); zfree(tcp_reass_zone, te); tcp_reass_qsize--; /* * Try to present any queued data * at the left window edge to the user. * This is needed after the 3-WHS * completes. */ goto present; /* ??? */ } m_adj(m, i); *tlenp -= i; th->th_seq += i; } } tcpstat.tcps_rcvoopack++; tcpstat.tcps_rcvoobyte += *tlenp; if (nstat_collect) { nstat_route_rx(tp->t_inpcb->inp_route.ro_rt, 1, *tlenp, NSTAT_RX_FLAG_OUT_OF_ORDER); locked_add_64(&tp->t_inpcb->inp_stat->rxpackets, 1); locked_add_64(&tp->t_inpcb->inp_stat->rxbytes, *tlenp); tp->t_stat.rxoutoforderbytes += *tlenp; } /* * While we overlap succeeding segments trim them or, * if they are completely covered, dequeue them. */ while (q) { register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; if (i <= 0) break; if (i < q->tqe_len) { q->tqe_th->th_seq += i; q->tqe_len -= i; m_adj(q->tqe_m, i); break; } nq = LIST_NEXT(q, tqe_q); LIST_REMOVE(q, tqe_q); m_freem(q->tqe_m); zfree(tcp_reass_zone, q); tcp_reass_qsize--; q = nq; } /* Insert the new segment queue entry into place. */ te->tqe_m = m; te->tqe_th = th; te->tqe_len = *tlenp; if (p == NULL) { LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); } else { LIST_INSERT_AFTER(p, te, tqe_q); } present: /* * Present data to user, advancing rcv_nxt through * completed sequence space. */ if (!TCPS_HAVEESTABLISHED(tp->t_state)) return (0); q = LIST_FIRST(&tp->t_segq); if (!q || q->tqe_th->th_seq != tp->rcv_nxt) { /* Stop using LRO once out of order packets arrive */ if (tp->t_flagsext & TF_LRO_OFFLOADED) { tcp_lro_remove_state(tp->t_inpcb->inp_laddr, tp->t_inpcb->inp_faddr, th->th_dport, th->th_sport); tp->t_flagsext &= ~TF_LRO_OFFLOADED; } return (0); } do { tp->rcv_nxt += q->tqe_len; flags = q->tqe_th->th_flags & TH_FIN; nq = LIST_NEXT(q, tqe_q); LIST_REMOVE(q, tqe_q); if (so->so_state & SS_CANTRCVMORE) m_freem(q->tqe_m); else { so_recv_data_stat(so, q->tqe_m, 0); /* XXXX */ if (sbappendstream(&so->so_rcv, q->tqe_m)) dowakeup = 1; if (tp->t_flagsext & TF_LRO_OFFLOADED) { tcp_update_lro_seq(tp->rcv_nxt, tp->t_inpcb->inp_laddr, tp->t_inpcb->inp_faddr, th->th_dport, th->th_sport); } } zfree(tcp_reass_zone, q); tcp_reass_qsize--; q = nq; } while (q && q->tqe_th->th_seq == tp->rcv_nxt); ND6_HINT(tp); #if INET6 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) { KERNEL_DEBUG(DBG_LAYER_BEG, ((tp->t_inpcb->inp_fport << 16) | tp->t_inpcb->inp_lport), (((tp->t_inpcb->in6p_laddr.s6_addr16[0] & 0xffff) << 16) | (tp->t_inpcb->in6p_faddr.s6_addr16[0] & 0xffff)), 0,0,0); } else #endif { KERNEL_DEBUG(DBG_LAYER_BEG, ((tp->t_inpcb->inp_fport << 16) | tp->t_inpcb->inp_lport), (((tp->t_inpcb->inp_laddr.s_addr & 0xffff) << 16) | (tp->t_inpcb->inp_faddr.s_addr & 0xffff)), 0,0,0); } if (dowakeup) sorwakeup(so); /* done with socket lock held */ return (flags); } /* * Reduce congestion window. */ static void tcp_reduce_congestion_window( struct tcpcb *tp) { /* * If the current tcp cc module has * defined a hook for tasks to run * before entering FR, call it */ if (CC_ALGO(tp)->pre_fr != NULL) CC_ALGO(tp)->pre_fr(tp); ENTER_FASTRECOVERY(tp); tp->snd_recover = tp->snd_max; tp->t_timer[TCPT_REXMT] = 0; tp->t_rtttime = 0; tp->ecn_flags |= TE_SENDCWR; tp->snd_cwnd = tp->snd_ssthresh + tp->t_maxseg * tcprexmtthresh; } /* * TCP input routine, follows pages 65-76 of the * protocol specification dated September, 1981 very closely. */ #if INET6 int tcp6_input(struct mbuf **mp, int *offp, int proto) { #pragma unused(proto) register struct mbuf *m = *mp; struct in6_ifaddr *ia6; struct ifnet *ifp = ((m->m_flags & M_PKTHDR) && m->m_pkthdr.rcvif != NULL) ? m->m_pkthdr.rcvif: NULL; IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), return IPPROTO_DONE); /* Expect 32-bit aligned data pointer on strict-align platforms */ MBUF_STRICT_DATA_ALIGNMENT_CHECK_32(m); /* * draft-itojun-ipv6-tcp-to-anycast * better place to put this in? */ ia6 = ip6_getdstifaddr(m); if (ia6 != NULL) { IFA_LOCK_SPIN(&ia6->ia_ifa); if (ia6->ia6_flags & IN6_IFF_ANYCAST) { struct ip6_hdr *ip6; IFA_UNLOCK(&ia6->ia_ifa); IFA_REMREF(&ia6->ia_ifa); ip6 = mtod(m, struct ip6_hdr *); icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->icmp6unreach, 1); return (IPPROTO_DONE); } IFA_UNLOCK(&ia6->ia_ifa); IFA_REMREF(&ia6->ia_ifa); } tcp_input(m, *offp); return (IPPROTO_DONE); } #endif /* Depending on the usage of mbuf space in the system, this function * will return true or false. This is used to determine if a socket * buffer can take more memory from the system for auto-tuning or not. */ u_int8_t tcp_cansbgrow(struct sockbuf *sb) { /* Calculate the host level space limit in terms of MSIZE buffers. * We can use a maximum of half of the available mbuf space for * socket buffers. */ u_int32_t mblim = ((nmbclusters >> 1) << (MCLSHIFT - MSIZESHIFT)); /* Calculate per sb limit in terms of bytes. We optimize this limit * for upto 16 socket buffers. */ u_int32_t sbspacelim = ((nmbclusters >> 4) << MCLSHIFT); if ((total_sbmb_cnt < mblim) && (sb->sb_hiwat < sbspacelim)) { return(1); } return(0); } void tcp_sbrcv_reserve(struct tcpcb *tp, struct sockbuf *sbrcv, u_int32_t newsize, u_int32_t idealsize) { /* newsize should not exceed max */ newsize = min(newsize, tcp_autorcvbuf_max); /* The receive window scale negotiated at the * beginning of the connection will also set a * limit on the socket buffer size */ newsize = min(newsize, TCP_MAXWIN << tp->rcv_scale); /* Set new socket buffer size */ if (newsize > sbrcv->sb_hiwat && (sbreserve(sbrcv, newsize) == 1)) { sbrcv->sb_idealsize = min(max(sbrcv->sb_idealsize, (idealsize != 0) ? idealsize : newsize), tcp_autorcvbuf_max); /* Again check the limit set by the advertised * window scale */ sbrcv->sb_idealsize = min(sbrcv->sb_idealsize, TCP_MAXWIN << tp->rcv_scale); } } /* * This function is used to grow a receive socket buffer. It * will take into account system-level memory usage and the * bandwidth available on the link to make a decision. */ static void tcp_sbrcv_grow(struct tcpcb *tp, struct sockbuf *sbrcv, struct tcpopt *to, u_int32_t pktlen) { if (tcp_do_autorcvbuf == 0 || (sbrcv->sb_flags & SB_AUTOSIZE) == 0 || tcp_cansbgrow(sbrcv) == 0 || sbrcv->sb_hiwat >= tcp_autorcvbuf_max) { /* Can not resize the socket buffer, just return */ goto out; } if (TSTMP_GT(tcp_now, tp->rfbuf_ts + TCPTV_RCVBUFIDLE)) { /* If there has been an idle period in the * connection, just restart the measurement */ goto out; } if ((tp->t_flags & (TF_REQ_TSTMP | TF_RCVD_TSTMP)) != (TF_REQ_TSTMP | TF_RCVD_TSTMP)) { /* * Timestamp option is not supported on this connection. * If the connection reached a state to indicate that * the receive socket buffer needs to grow, increase * the high water mark. */ if (TSTMP_GEQ(tcp_now, tp->rfbuf_ts + TCPTV_RCVNOTS_QUANTUM)) { if (tp->rfbuf_cnt >= TCP_RCVNOTS_BYTELEVEL) { tcp_sbrcv_reserve(tp, sbrcv, tcp_autorcvbuf_max, 0); } goto out; } else { tp->rfbuf_cnt += pktlen; return; } } else if (to->to_tsecr != 0) { /* If the timestamp shows that one RTT has * completed, we can stop counting the * bytes. Here we consider increasing * the socket buffer if it fits the following * criteria: * 1. the bandwidth measured in last rtt, is more * than half of sb_hiwat, this will help to scale the * buffer according to the bandwidth on the link. * 2. the space left in sbrcv is less than * one forth of the bandwidth measured in last rtt, this * will help to accommodate an application reading slowly. */ if (TSTMP_GEQ(to->to_tsecr, tp->rfbuf_ts)) { if ((tp->rfbuf_cnt > (sbrcv->sb_hiwat - (sbrcv->sb_hiwat >> tcp_rbuf_hiwat_shift)) || (sbrcv->sb_hiwat - sbrcv->sb_cc) < (tp->rfbuf_cnt >> tcp_rbuf_win_shift))) { u_int32_t rcvbuf_inc; /* * Increment the receive window by a multiple of * maximum sized segments. This will prevent a * connection from sending smaller segments on * wire if it is limited by the receive window. * * Set the ideal size based on current bandwidth * measurements. We set the ideal size on receive * socket buffer to be twice the bandwidth delay * product. */ rcvbuf_inc = tp->t_maxseg << tcp_autorcvbuf_inc_shift; tcp_sbrcv_reserve(tp, sbrcv, sbrcv->sb_hiwat + rcvbuf_inc, (tp->rfbuf_cnt * 2)); } goto out; } else { tp->rfbuf_cnt += pktlen; return; } } out: /* Restart the measurement */ tp->rfbuf_ts = 0; tp->rfbuf_cnt = 0; return; } /* This function will trim the excess space added to the socket buffer * to help a slow-reading app. The ideal-size of a socket buffer depends * on the link bandwidth or it is set by an application and we aim to * reach that size. */ void tcp_sbrcv_trim(struct tcpcb *tp, struct sockbuf *sbrcv) { if (tcp_do_autorcvbuf == 1 && sbrcv->sb_idealsize > 0 && sbrcv->sb_hiwat > sbrcv->sb_idealsize) { int32_t trim; /* compute the difference between ideal and current sizes */ u_int32_t diff = sbrcv->sb_hiwat - sbrcv->sb_idealsize; /* Compute the maximum advertised window for * this connection. */ u_int32_t advwin = tp->rcv_adv - tp->rcv_nxt; /* How much can we trim the receive socket buffer? * 1. it can not be trimmed beyond the max rcv win advertised * 2. if possible, leave 1/16 of bandwidth*delay to * avoid closing the win completely */ u_int32_t leave = max(advwin, (sbrcv->sb_idealsize >> 4)); /* Sometimes leave can be zero, in that case leave at least * a few segments worth of space. */ if (leave == 0) leave = tp->t_maxseg << tcp_autorcvbuf_inc_shift; trim = sbrcv->sb_hiwat - (sbrcv->sb_cc + leave); trim = imin(trim, (int32_t)diff); if (trim > 0) sbreserve(sbrcv, (sbrcv->sb_hiwat - trim)); } } /* We may need to trim the send socket buffer size for two reasons: * 1. if the rtt seen on the connection is climbing up, we do not * want to fill the buffers any more. * 2. if the congestion win on the socket backed off, there is no need * to hold more mbufs for that connection than what the cwnd will allow. */ void tcp_sbsnd_trim(struct sockbuf *sbsnd) { if (tcp_do_autosendbuf == 1 && ((sbsnd->sb_flags & (SB_AUTOSIZE | SB_TRIM)) == (SB_AUTOSIZE | SB_TRIM)) && (sbsnd->sb_idealsize > 0) && (sbsnd->sb_hiwat > sbsnd->sb_idealsize)) { u_int32_t trim = 0; if (sbsnd->sb_cc <= sbsnd->sb_idealsize) { trim = sbsnd->sb_hiwat - sbsnd->sb_idealsize; } else { trim = sbsnd->sb_hiwat - sbsnd->sb_cc; } sbreserve(sbsnd, (sbsnd->sb_hiwat - trim)); } if (sbsnd->sb_hiwat <= sbsnd->sb_idealsize) sbsnd->sb_flags &= ~(SB_TRIM); } /* * If timestamp option was not negotiated on this connection * and this connection is on the receiving side of a stream * then we can not measure the delay on the link accurately. * Instead of enabling automatic receive socket buffer * resizing, just give more space to the receive socket buffer. */ static inline void tcp_sbrcv_tstmp_check(struct tcpcb *tp) { struct socket *so = tp->t_inpcb->inp_socket; u_int32_t newsize = 2 * tcp_recvspace; struct sockbuf *sbrcv = &so->so_rcv; if ((tp->t_flags & (TF_REQ_TSTMP | TF_RCVD_TSTMP)) != (TF_REQ_TSTMP | TF_RCVD_TSTMP) && (sbrcv->sb_flags & SB_AUTOSIZE) != 0) { tcp_sbrcv_reserve(tp, sbrcv, newsize, 0); } } /* A receiver will evaluate the flow of packets on a connection * to see if it can reduce ack traffic. The receiver will start * stretching acks if all of the following conditions are met: * 1. tcp_delack_enabled is set to 3 * 2. If the bytes received in the last 100ms is greater than a threshold * defined by maxseg_unacked * 3. If the connection has not been idle for tcp_maxrcvidle period. * 4. If the connection has seen enough packets to let the slow-start * finish after connection establishment or after some packet loss. * * The receiver will stop stretching acks if there is congestion/reordering * as indicated by packets on reassembly queue or an ECN. If the delayed-ack * timer fires while stretching acks, it means that the packet flow has gone * below the threshold defined by maxseg_unacked and the receiver will stop * stretching acks. The receiver gets no indication when slow-start is completed * or when the connection reaches an idle state. That is why we use * tcp_rcvsspktcnt to cover slow-start and tcp_maxrcvidle to identify idle * state. */ static inline int tcp_stretch_ack_enable(struct tcpcb *tp) { if (tp->rcv_by_unackwin >= (maxseg_unacked * tp->t_maxseg) && TSTMP_GT(tp->rcv_unackwin + tcp_maxrcvidle, tcp_now) && (((tp->t_flagsext & TF_RCVUNACK_WAITSS) == 0) || (tp->rcv_waitforss >= tcp_rcvsspktcnt))) { return(1); } return(0); } /* Reset the state related to stretch-ack algorithm. This will make * the receiver generate an ack every other packet. The receiver * will start re-evaluating the rate at which packets come to decide * if it can benefit by lowering the ack traffic. */ void tcp_reset_stretch_ack(struct tcpcb *tp) { tp->t_flags &= ~(TF_STRETCHACK); tp->rcv_by_unackwin = 0; tp->rcv_unackwin = tcp_now + tcp_rcvunackwin; } void tcp_input(m, off0) struct mbuf *m; int off0; { register struct tcphdr *th; register struct ip *ip = NULL; register struct ipovly *ipov; register struct inpcb *inp; u_char *optp = NULL; int optlen = 0; int len, tlen, off; int drop_hdrlen; register struct tcpcb *tp = 0; register int thflags; struct socket *so = 0; int todrop, acked, ourfinisacked, needoutput = 0; struct in_addr laddr; #if INET6 struct in6_addr laddr6; #endif int dropsocket = 0; int iss = 0, nosock = 0; u_int32_t tiwin; struct tcpopt to; /* options in this segment */ struct sockaddr_in *next_hop = NULL; #if TCPDEBUG short ostate = 0; #endif struct m_tag *fwd_tag; u_char ip_ecn = IPTOS_ECN_NOTECT; unsigned int ifscope, nocell = 0; uint8_t isconnected, isdisconnected; struct ifnet *ifp = ((m->m_flags & M_PKTHDR) && m->m_pkthdr.rcvif != NULL) ? m->m_pkthdr.rcvif: NULL; int nlropkts = m->m_pkthdr.lro_npkts; int mauxf_sw_lro_pkt = (m->m_pkthdr.aux_flags & MAUXF_SW_LRO_PKT) ? 1 : 0; int turnoff_lro = 0; #define TCP_INC_VAR(stat, npkts) do { \ if (mauxf_sw_lro_pkt) { \ stat += npkts; \ } else { \ stat++; \ } \ } while (0) TCP_INC_VAR(tcpstat.tcps_rcvtotal, nlropkts); /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ if (!SLIST_EMPTY(&m->m_pkthdr.tags)) { fwd_tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_IPFORWARD, NULL); } else { fwd_tag = NULL; } if (fwd_tag != NULL) { struct ip_fwd_tag *ipfwd_tag = (struct ip_fwd_tag *)(fwd_tag+1); next_hop = ipfwd_tag->next_hop; m_tag_delete(m, fwd_tag); } #if INET6 struct ip6_hdr *ip6 = NULL; int isipv6; #endif /* INET6 */ int rstreason; /* For badport_bandlim accounting purposes */ struct proc *proc0=current_proc(); KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_START,0,0,0,0,0); #if INET6 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; #endif bzero((char *)&to, sizeof(to)); #if INET6 if (isipv6) { /* Expect 32-bit aligned data pointer on strict-align platforms */ MBUF_STRICT_DATA_ALIGNMENT_CHECK_32(m); /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ ip6 = mtod(m, struct ip6_hdr *); tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; th = (struct tcphdr *)(void *)((caddr_t)ip6 + off0); if ((apple_hwcksum_rx != 0) && (m->m_pkthdr.csum_flags & CSUM_DATA_VALID)) { if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) th->th_sum = m->m_pkthdr.csum_data; else { /* * There is no established protocol for the case * where IPv6 psuedoheader checksum is not computed * with our current drivers. Current drivers set * CSUM_PSEUDO_HDR. So if we do get here, we should * recalculate checksum. */ if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { th->th_sum = 0; } else { th->th_sum = 0xffff; } } th->th_sum ^= 0xffff; if (th->th_sum) { tcpstat.tcps_rcvbadsum++; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->badformat, 1); goto dropnosock; } } else { if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { tcpstat.tcps_rcvbadsum++; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->badformat, 1); goto dropnosock; } } KERNEL_DEBUG(DBG_LAYER_BEG, ((th->th_dport << 16) | th->th_sport), (((ip6->ip6_src.s6_addr16[0]) << 16) | (ip6->ip6_dst.s6_addr16[0])), th->th_seq, th->th_ack, th->th_win); /* * Be proactive about unspecified IPv6 address in source. * As we use all-zero to indicate unbounded/unconnected pcb, * unspecified IPv6 address can be used to confuse us. * * Note that packets with unspecified IPv6 destination is * already dropped in ip6_input. */ if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { /* XXX stat */ if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->unspecv6, 1); goto dropnosock; } DTRACE_TCP5(receive, sruct mbuf *, m, struct inpcb *, NULL, struct ip6_hdr *, ip6, struct tcpcb *, NULL, struct tcphdr *, th); ip_ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK; } else #endif /* INET6 */ { /* * Get IP and TCP header together in first mbuf. * Note: IP leaves IP header in first mbuf. */ if (off0 > sizeof (struct ip)) { ip_stripoptions(m, (struct mbuf *)0); off0 = sizeof(struct ip); if (m->m_pkthdr.csum_flags & CSUM_TCP_SUM16) m->m_pkthdr.csum_flags = 0; /* invalidate hwcksuming */ } if (m->m_len < sizeof (struct tcpiphdr)) { if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { tcpstat.tcps_rcvshort++; return; } } /* Expect 32-bit aligned data pointer on strict-align platforms */ MBUF_STRICT_DATA_ALIGNMENT_CHECK_32(m); ip = mtod(m, struct ip *); ipov = (struct ipovly *)ip; th = (struct tcphdr *)(void *)((caddr_t)ip + off0); tlen = ip->ip_len; if (m->m_pkthdr.aux_flags & MAUXF_SW_LRO_DID_CSUM) { goto skip_checksum; } if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { if (m->m_pkthdr.csum_flags & CSUM_TCP_SUM16) { u_short pseudo; char b[9]; bcopy(ipov->ih_x1, b, sizeof (ipov->ih_x1)); bzero(ipov->ih_x1, sizeof (ipov->ih_x1)); ipov->ih_len = (u_short)tlen; #if BYTE_ORDER != BIG_ENDIAN HTONS(ipov->ih_len); #endif pseudo = in_cksum(m, sizeof (struct ip)); bcopy(b, ipov->ih_x1, sizeof (ipov->ih_x1)); th->th_sum = in_addword(pseudo, (m->m_pkthdr.csum_data & 0xFFFF)); } else { if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) th->th_sum = m->m_pkthdr.csum_data; else th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, htonl(m->m_pkthdr.csum_data + ip->ip_len + IPPROTO_TCP)); } th->th_sum ^= 0xffff; } else { char b[9]; /* * Checksum extended TCP header and data. */ bcopy(ipov->ih_x1, b, sizeof (ipov->ih_x1)); bzero(ipov->ih_x1, sizeof (ipov->ih_x1)); ipov->ih_len = (u_short)tlen; #if BYTE_ORDER != BIG_ENDIAN HTONS(ipov->ih_len); #endif len = sizeof (struct ip) + tlen; th->th_sum = in_cksum(m, len); bcopy(b, ipov->ih_x1, sizeof (ipov->ih_x1)); tcp_in_cksum_stats(len); } if (th->th_sum) { tcpstat.tcps_rcvbadsum++; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->badformat, 1); if (lrodebug) printf("tcp_input: bad xsum len = %d, tlen = %d, flags = %x, csum_flags = %x.\n",len, tlen, m->m_flags, m->m_pkthdr.csum_flags); goto dropnosock; } skip_checksum: #if INET6 /* Re-initialization for later version check */ ip->ip_v = IPVERSION; #endif ip_ecn = (ip->ip_tos & IPTOS_ECN_MASK); DTRACE_TCP5(receive, struct mbuf *, m, struct inpcb *, NULL, struct ip *, ip, struct tcpcb *, NULL, struct tcphdr *, th); KERNEL_DEBUG(DBG_LAYER_BEG, ((th->th_dport << 16) | th->th_sport), (((ip->ip_src.s_addr & 0xffff) << 16) | (ip->ip_dst.s_addr & 0xffff)), th->th_seq, th->th_ack, th->th_win); } /* * Check that TCP offset makes sense, * pull out TCP options and adjust length. XXX */ off = th->th_off << 2; if (off < sizeof (struct tcphdr) || off > tlen) { tcpstat.tcps_rcvbadoff++; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->badformat, 1); goto dropnosock; } tlen -= off; /* tlen is used instead of ti->ti_len */ if (off > sizeof (struct tcphdr)) { #if INET6 if (isipv6) { IP6_EXTHDR_CHECK(m, off0, off, return); ip6 = mtod(m, struct ip6_hdr *); th = (struct tcphdr *)(void *)((caddr_t)ip6 + off0); } else #endif /* INET6 */ { if (m->m_len < sizeof(struct ip) + off) { if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { tcpstat.tcps_rcvshort++; return; } ip = mtod(m, struct ip *); ipov = (struct ipovly *)ip; th = (struct tcphdr *)(void *)((caddr_t)ip + off0); } } optlen = off - sizeof (struct tcphdr); optp = (u_char *)(th + 1); /* * Do quick retrieval of timestamp options ("options * prediction?"). If timestamp is the only option and it's * formatted as recommended in RFC 1323 appendix A, we * quickly get the values now and not bother calling * tcp_dooptions(), etc. */ if ((optlen == TCPOLEN_TSTAMP_APPA || (optlen > TCPOLEN_TSTAMP_APPA && optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) && *(u_int32_t *)(void *)optp == htonl(TCPOPT_TSTAMP_HDR) && (th->th_flags & TH_SYN) == 0) { to.to_flags |= TOF_TS; to.to_tsval = ntohl(*(u_int32_t *)(void *)(optp + 4)); to.to_tsecr = ntohl(*(u_int32_t *)(void *)(optp + 8)); optp = NULL; /* we've parsed the options */ } } thflags = th->th_flags; #if TCP_DROP_SYNFIN /* * If the drop_synfin option is enabled, drop all packets with * both the SYN and FIN bits set. This prevents e.g. nmap from * identifying the TCP/IP stack. * * This is a violation of the TCP specification. */ if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) { if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->synfin, 1); goto dropnosock; } #endif /* * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, * until after ip6_savecontrol() is called and before other functions * which don't want those proto headers. * Because ip6_savecontrol() is going to parse the mbuf to * search for data to be passed up to user-land, it wants mbuf * parameters to be unchanged. */ drop_hdrlen = off0 + off; /* Since this is an entry point for input processing of tcp packets, we * can update the tcp clock here. */ calculate_tcp_clock(); /* * Record the interface where this segment arrived on; this does not * affect normal data output (for non-detached TCP) as it provides a * hint about which route and interface to use for sending in the * absence of a PCB, when scoped routing (and thus source interface * selection) are enabled. */ if ((m->m_flags & M_PKTHDR) && m->m_pkthdr.rcvif != NULL) ifscope = m->m_pkthdr.rcvif->if_index; else ifscope = IFSCOPE_NONE; /* * Convert TCP protocol specific fields to host format. */ #if BYTE_ORDER != BIG_ENDIAN NTOHL(th->th_seq); NTOHL(th->th_ack); NTOHS(th->th_win); NTOHS(th->th_urp); #endif /* * Locate pcb for segment. */ findpcb: isconnected = FALSE; isdisconnected = FALSE; #if IPFIREWALL_FORWARD if (next_hop != NULL #if INET6 && isipv6 == 0 /* IPv6 support is not yet */ #endif /* INET6 */ ) { /* * Diverted. Pretend to be the destination. * already got one like this? */ inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, ip->ip_dst, th->th_dport, 0, m->m_pkthdr.rcvif); if (!inp) { /* * No, then it's new. Try find the ambushing socket */ if (!next_hop->sin_port) { inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, next_hop->sin_addr, th->th_dport, 1, m->m_pkthdr.rcvif); } else { inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, next_hop->sin_addr, ntohs(next_hop->sin_port), 1, m->m_pkthdr.rcvif); } } } else #endif /* IPFIREWALL_FORWARD */ { #if INET6 if (isipv6) inp = in6_pcblookup_hash(&tcbinfo, &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 1, m->m_pkthdr.rcvif); else #endif /* INET6 */ inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, ip->ip_dst, th->th_dport, 1, m->m_pkthdr.rcvif); } /* * Use the interface scope information from the PCB for outbound * segments. If the PCB isn't present and if scoped routing is * enabled, tcp_respond will use the scope of the interface where * the segment arrived on. */ if (inp != NULL && (inp->inp_flags & INP_BOUND_IF)) ifscope = inp->inp_boundifp->if_index; /* * If the PCB is present and the socket isn't allowed to use * the cellular interface, indicate it as such for tcp_respond. */ if (inp != NULL && (inp->inp_flags & INP_NO_IFT_CELLULAR)) nocell = 1; #if IPSEC if (ipsec_bypass == 0) { #if INET6 if (isipv6) { if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) { IPSEC_STAT_INCREMENT(ipsec6stat.in_polvio); if (in_pcb_checkstate(inp, WNT_RELEASE, 0) == WNT_STOPUSING) inp = NULL; // pretend we didn't find it if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->badformatipsec, 1); goto dropnosock; } } else #endif /* INET6 */ if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { IPSEC_STAT_INCREMENT(ipsecstat.in_polvio); if (in_pcb_checkstate(inp, WNT_RELEASE, 0) == WNT_STOPUSING) inp = NULL; // pretend we didn't find it if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->badformatipsec, 1); goto dropnosock; } } #endif /*IPSEC*/ /* * If the state is CLOSED (i.e., TCB does not exist) then * all data in the incoming segment is discarded. * If the TCB exists but is in CLOSED state, it is embryonic, * but should either do a listen or a connect soon. */ if (inp == NULL) { if (log_in_vain) { #if INET6 char dbuf[MAX_IPv6_STR_LEN], sbuf[MAX_IPv6_STR_LEN]; #else /* INET6 */ char dbuf[MAX_IPv4_STR_LEN], sbuf[MAX_IPv4_STR_LEN]; #endif /* INET6 */ #if INET6 if (isipv6) { inet_ntop(AF_INET6, &ip6->ip6_dst, dbuf, sizeof(dbuf)); inet_ntop(AF_INET6, &ip6->ip6_src, sbuf, sizeof(sbuf)); } else #endif { inet_ntop(AF_INET, &ip->ip_dst, dbuf, sizeof(dbuf)); inet_ntop(AF_INET, &ip->ip_src, sbuf, sizeof(sbuf)); } switch (log_in_vain) { case 1: if(thflags & TH_SYN) log(LOG_INFO, "Connection attempt to TCP %s:%d from %s:%d\n", dbuf, ntohs(th->th_dport), sbuf, ntohs(th->th_sport)); break; case 2: log(LOG_INFO, "Connection attempt to TCP %s:%d from %s:%d flags:0x%x\n", dbuf, ntohs(th->th_dport), sbuf, ntohs(th->th_sport), thflags); break; case 3: if ((thflags & TH_SYN) && !(thflags & TH_ACK) && !(m->m_flags & (M_BCAST | M_MCAST)) && #if INET6 ((isipv6 && !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) || (!isipv6 && ip->ip_dst.s_addr != ip->ip_src.s_addr)) #else ip->ip_dst.s_addr != ip->ip_src.s_addr #endif ) log_in_vain_log((LOG_INFO, "Stealth Mode connection attempt to TCP %s:%d from %s:%d\n", dbuf, ntohs(th->th_dport), sbuf, ntohs(th->th_sport))); break; default: break; } } if (blackhole) { if (m->m_pkthdr.rcvif && m->m_pkthdr.rcvif->if_type != IFT_LOOP) switch (blackhole) { case 1: if (thflags & TH_SYN) goto dropnosock; break; case 2: goto dropnosock; default: goto dropnosock; } } rstreason = BANDLIM_RST_CLOSEDPORT; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->noconnnolist, 1); goto dropwithresetnosock; } so = inp->inp_socket; if (so == NULL) { /* This case shouldn't happen as the socket shouldn't be null * if inp_state isn't set to INPCB_STATE_DEAD * But just in case, we pretend we didn't find the socket if we hit this case * as this isn't cause for a panic (the socket might be leaked however)... */ inp = NULL; #if TEMPDEBUG printf("tcp_input: no more socket for inp=%x. This shouldn't happen\n", inp); #endif goto dropnosock; } tcp_lock(so, 1, 0); if (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING) { tcp_unlock(so, 1, (void *)2); inp = NULL; // pretend we didn't find it goto dropnosock; } tp = intotcpcb(inp); if (tp == 0) { rstreason = BANDLIM_RST_CLOSEDPORT; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->noconnlist, 1); goto dropwithreset; } if (tp->t_state == TCPS_CLOSED) goto drop; /* Unscale the window into a 32-bit value. */ if ((thflags & TH_SYN) == 0) tiwin = th->th_win << tp->snd_scale; else tiwin = th->th_win; #if CONFIG_MACF_NET if (mac_inpcb_check_deliver(inp, m, AF_INET, SOCK_STREAM)) goto drop; #endif /* Radar 7377561: Avoid processing packets while closing a listen socket */ if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN) == 0) goto drop; if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { #if TCPDEBUG if (so->so_options & SO_DEBUG) { ostate = tp->t_state; #if INET6 if (isipv6) bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); else #endif /* INET6 */ bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); tcp_savetcp = *th; } #endif if (so->so_options & SO_ACCEPTCONN) { register struct tcpcb *tp0 = tp; struct socket *so2; struct socket *oso; struct sockaddr_storage from; #if INET6 struct inpcb *oinp = sotoinpcb(so); #endif /* INET6 */ struct ifnet *head_ifscope; unsigned int head_nocell, head_recvanyif; /* Get listener's bound-to-interface, if any */ head_ifscope = (inp->inp_flags & INP_BOUND_IF) ? inp->inp_boundifp : NULL; /* Get listener's no-cellular information, if any */ head_nocell = (inp->inp_flags & INP_NO_IFT_CELLULAR) ? 1 : 0; /* Get listener's recv-any-interface, if any */ head_recvanyif = (inp->inp_flags & INP_RECV_ANYIF); /* * If the state is LISTEN then ignore segment if it contains an RST. * If the segment contains an ACK then it is bad and send a RST. * If it does not contain a SYN then it is not interesting; drop it. * If it is from this socket, drop it, it must be forged. */ if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->listbadsyn, 1); if (thflags & TH_RST) { goto drop; } if (thflags & TH_ACK) { tp = NULL; tcpstat.tcps_badsyn++; rstreason = BANDLIM_RST_OPENPORT; goto dropwithreset; } /* We come here if there is no SYN set */ tcpstat.tcps_badsyn++; goto drop; } KERNEL_DEBUG(DBG_FNC_TCP_NEWCONN | DBG_FUNC_START,0,0,0,0,0); if (th->th_dport == th->th_sport) { #if INET6 if (isipv6) { if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) goto drop; } else #endif /* INET6 */ if (ip->ip_dst.s_addr == ip->ip_src.s_addr) goto drop; } /* * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN * in_broadcast() should never return true on a received * packet with M_BCAST not set. * * Packets with a multicast source address should also * be discarded. */ if (m->m_flags & (M_BCAST|M_MCAST)) goto drop; #if INET6 if (isipv6) { if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) goto drop; } else #endif if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) goto drop; #if INET6 /* * If deprecated address is forbidden, * we do not accept SYN to deprecated interface * address to prevent any new inbound connection from * getting established. * When we do not accept SYN, we send a TCP RST, * with deprecated source address (instead of dropping * it). We compromise it as it is much better for peer * to send a RST, and RST will be the final packet * for the exchange. * * If we do not forbid deprecated addresses, we accept * the SYN packet. RFC2462 does not suggest dropping * SYN in this case. * If we decipher RFC2462 5.5.4, it says like this: * 1. use of deprecated addr with existing * communication is okay - "SHOULD continue to be * used" * 2. use of it with new communication: * (2a) "SHOULD NOT be used if alternate address * with sufficient scope is available" * (2b) nothing mentioned otherwise. * Here we fall into (2b) case as we have no choice in * our source address selection - we must obey the peer. * * The wording in RFC2462 is confusing, and there are * multiple description text for deprecated address * handling - worse, they are not exactly the same. * I believe 5.5.4 is the best one, so we follow 5.5.4. */ if (isipv6 && !ip6_use_deprecated) { struct in6_ifaddr *ia6; ia6 = ip6_getdstifaddr(m); if (ia6 != NULL) { IFA_LOCK_SPIN(&ia6->ia_ifa); if (ia6->ia6_flags & IN6_IFF_DEPRECATED) { IFA_UNLOCK(&ia6->ia_ifa); IFA_REMREF(&ia6->ia_ifa); tp = NULL; rstreason = BANDLIM_RST_OPENPORT; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->deprecate6, 1); goto dropwithreset; } IFA_UNLOCK(&ia6->ia_ifa); IFA_REMREF(&ia6->ia_ifa); } } #endif if (so->so_filt) { #if INET6 if (isipv6) { struct sockaddr_in6 *sin6 = (struct sockaddr_in6*)&from; sin6->sin6_len = sizeof(*sin6); sin6->sin6_family = AF_INET6; sin6->sin6_port = th->th_sport; sin6->sin6_flowinfo = 0; sin6->sin6_addr = ip6->ip6_src; sin6->sin6_scope_id = 0; } else #endif { struct sockaddr_in *sin = (struct sockaddr_in*)&from; sin->sin_len = sizeof(*sin); sin->sin_family = AF_INET; sin->sin_port = th->th_sport; sin->sin_addr = ip->ip_src; } so2 = sonewconn(so, 0, (struct sockaddr*)&from); } else { so2 = sonewconn(so, 0, NULL); } if (so2 == 0) { tcpstat.tcps_listendrop++; if (tcp_dropdropablreq(so)) { if (so->so_filt) so2 = sonewconn(so, 0, (struct sockaddr*)&from); else so2 = sonewconn(so, 0, NULL); } if (!so2) goto drop; } /* Point "inp" and "tp" in tandem to new socket */ inp = (struct inpcb *)so2->so_pcb; tp = intotcpcb(inp); oso = so; tcp_unlock(so, 0, 0); /* Unlock but keep a reference on listener for now */ so = so2; tcp_lock(so, 1, 0); /* * Mark socket as temporary until we're * committed to keeping it. The code at * ``drop'' and ``dropwithreset'' check the * flag dropsocket to see if the temporary * socket created here should be discarded. * We mark the socket as discardable until * we're committed to it below in TCPS_LISTEN. * There are some error conditions in which we * have to drop the temporary socket. */ dropsocket++; /* * Inherit INP_BOUND_IF from listener; testing if * head_ifscope is non-NULL is sufficient, since it * can only be set to a non-zero value earlier if * the listener has such a flag set. */ if (head_ifscope != NULL) { inp->inp_flags |= INP_BOUND_IF; inp->inp_boundifp = head_ifscope; } else { inp->inp_flags &= ~INP_BOUND_IF; } /* * Inherit INP_NO_IFT_CELLULAR from listener. */ if (head_nocell) { inp->inp_flags |= INP_NO_IFT_CELLULAR; } /* * Inherit {IN,IN6}_RECV_ANYIF from listener. */ if (head_recvanyif) inp->inp_flags |= INP_RECV_ANYIF; else inp->inp_flags &= ~INP_RECV_ANYIF; #if INET6 if (isipv6) inp->in6p_laddr = ip6->ip6_dst; else { inp->inp_vflag &= ~INP_IPV6; inp->inp_vflag |= INP_IPV4; #endif /* INET6 */ inp->inp_laddr = ip->ip_dst; #if INET6 } #endif /* INET6 */ inp->inp_lport = th->th_dport; if (in_pcbinshash(inp, 0) != 0) { /* * Undo the assignments above if we failed to * put the PCB on the hash lists. */ #if INET6 if (isipv6) inp->in6p_laddr = in6addr_any; else #endif /* INET6 */ inp->inp_laddr.s_addr = INADDR_ANY; inp->inp_lport = 0; tcp_lock(oso, 0, 0); /* release ref on parent */ tcp_unlock(oso, 1, 0); goto drop; } #if INET6 if (isipv6) { /* * Inherit socket options from the listening * socket. * Note that in6p_inputopts are not (even * should not be) copied, since it stores * previously received options and is used to * detect if each new option is different than * the previous one and hence should be passed * to a user. * If we copied in6p_inputopts, a user would * not be able to receive options just after * calling the accept system call. */ inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; if (oinp->in6p_outputopts) inp->in6p_outputopts = ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); } else #endif /* INET6 */ inp->inp_options = ip_srcroute(); tcp_lock(oso, 0, 0); #if IPSEC /* copy old policy into new socket's */ if (sotoinpcb(oso)->inp_sp) { int error = 0; /* Is it a security hole here to silently fail to copy the policy? */ if (inp->inp_sp != NULL) error = ipsec_init_policy(so, &inp->inp_sp); if (error != 0 || ipsec_copy_policy(sotoinpcb(oso)->inp_sp, inp->inp_sp)) printf("tcp_input: could not copy policy\n"); } #endif /* inherit states from the listener */ DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_LISTEN); tp->t_state = TCPS_LISTEN; tp->t_flags |= tp0->t_flags & (TF_NOPUSH|TF_NOOPT|TF_NODELAY); tp->t_flagsext |= (tp0->t_flagsext & TF_RXTFINDROP); tp->t_keepinit = tp0->t_keepinit; tp->t_inpcb->inp_ip_ttl = tp0->t_inpcb->inp_ip_ttl; if ((so->so_flags & SOF_NOTSENT_LOWAT) != 0) tp->t_notsent_lowat = tp0->t_notsent_lowat; /* now drop the reference on the listener */ tcp_unlock(oso, 1, 0); tcp_set_max_rwinscale(tp, so); KERNEL_DEBUG(DBG_FNC_TCP_NEWCONN | DBG_FUNC_END,0,0,0,0,0); } } lck_mtx_assert(&((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED); /* * Radar 3529618 * This is the second part of the MSS DoS prevention code (after * minmss on the sending side) and it deals with too many too small * tcp packets in a too short timeframe (1 second). * * For every full second we count the number of received packets * and bytes. If we get a lot of packets per second for this connection * (tcp_minmssoverload) we take a closer look at it and compute the * average packet size for the past second. If that is less than * tcp_minmss we get too many packets with very small payload which * is not good and burdens our system (and every packet generates * a wakeup to the process connected to our socket). We can reasonable * expect this to be small packet DoS attack to exhaust our CPU * cycles. * * Care has to be taken for the minimum packet overload value. This * value defines the minimum number of packets per second before we * start to worry. This must not be too low to avoid killing for * example interactive connections with many small packets like * telnet or SSH. * * Setting either tcp_minmssoverload or tcp_minmss to "0" disables * this check. * * Account for packet if payload packet, skip over ACK, etc. */ if (tp->t_state == TCPS_ESTABLISHED && tlen > 0) { if (TSTMP_GT(tp->rcv_reset, tcp_now)) { tp->rcv_pps++; tp->rcv_byps += tlen + off; if (tp->rcv_byps > tp->rcv_maxbyps) tp->rcv_maxbyps = tp->rcv_byps; /* * Setting either tcp_minmssoverload or tcp_minmss to "0" disables * the check. */ if (tcp_minmss && tcp_minmssoverload && tp->rcv_pps > tcp_minmssoverload) { if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { char ipstrbuf[MAX_IPv6_STR_LEN]; printf("too many small tcp packets from " "%s:%u, av. %ubyte/packet, " "dropping connection\n", #if INET6 isipv6 ? inet_ntop(AF_INET6, &inp->in6p_faddr, ipstrbuf, sizeof(ipstrbuf)) : #endif inet_ntop(AF_INET, &inp->inp_faddr, ipstrbuf, sizeof(ipstrbuf)), inp->inp_fport, tp->rcv_byps / tp->rcv_pps); tp = tcp_drop(tp, ECONNRESET); /* tcpstat.tcps_minmssdrops++; */ goto drop; } } } else { tp->rcv_reset = tcp_now + TCP_RETRANSHZ; tp->rcv_pps = 1; tp->rcv_byps = tlen + off; } /* Evaluate the rate of arrival of packets to see if the * receiver can reduce the ack traffic. The algorithm to * stretch acks will be enabled if the connection meets * certain criteria defined in tcp_stretch_ack_enable function. */ if ((tp->t_flagsext & TF_RCVUNACK_WAITSS) != 0) { TCP_INC_VAR(tp->rcv_waitforss, nlropkts); } if (tcp_stretch_ack_enable(tp)) { tp->t_flags |= TF_STRETCHACK; tp->t_flagsext &= ~(TF_RCVUNACK_WAITSS); tp->rcv_waitforss = 0; } else { tp->t_flags &= ~(TF_STRETCHACK); } if (TSTMP_GT(tp->rcv_unackwin, tcp_now)) { tp->rcv_by_unackwin += (tlen + off); } else { tp->rcv_unackwin = tcp_now + tcp_rcvunackwin; tp->rcv_by_unackwin = tlen + off; } } /* * Keep track of how many bytes were received in the LRO packet */ if ((mauxf_sw_lro_pkt) && (nlropkts > 2)) { tp->t_lropktlen += tlen; } /* Explicit Congestion Notification - Flag that we need to send ECT if + The IP Congestion experienced flag was set. + Socket is in established state + We negotiated ECN in the TCP setup + This isn't a pure ack (tlen > 0) + The data is in the valid window TE_SENDECE will be cleared when we receive a packet with TH_CWR set. */ if (ip_ecn == IPTOS_ECN_CE && tp->t_state == TCPS_ESTABLISHED && ((tp->ecn_flags & (TE_ECN_ON)) == (TE_ECN_ON)) && tlen > 0 && SEQ_GEQ(th->th_seq, tp->last_ack_sent) && SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { tp->ecn_flags |= TE_SENDECE; } /* Clear TE_SENDECE if TH_CWR is set. This is harmless, so we don't bother doing extensive checks for state and whatnot. */ if ((thflags & TH_CWR) == TH_CWR) { tp->ecn_flags &= ~TE_SENDECE; } /* If we received an explicit notification of congestion in * ip tos ecn bits or by the CWR bit in TCP header flags, reset * the ack-strteching state. */ if (tp->t_state == TCPS_ESTABLISHED && (tp->t_flags & TF_STRETCHACK) != 0 && ((ip_ecn == IPTOS_ECN_CE) || ((thflags & TH_CWR) == TH_CWR))) tcp_reset_stretch_ack(tp); /* * Try to determine if we are receiving a packet after a long time. * Use our own approximation of idletime to roughly measure remote * end's idle time. Since slowstart is used after an idle period * we want to avoid doing LRO if the remote end is not up to date * on initial window support and starts with 1 or 2 packets as its IW. */ if (sw_lro && (tp->t_flagsext & TF_LRO_OFFLOADED) && ((tcp_now - tp->t_rcvtime) >= (TCP_IDLETIMEOUT(tp)))) { turnoff_lro = 1; } /* * Segment received on connection. * Reset idle time and keep-alive timer. */ tp->t_rcvtime = tcp_now; if (TCPS_HAVEESTABLISHED(tp->t_state)) tp->t_timer[TCPT_KEEP] = OFFSET_FROM_START(tp, TCP_KEEPIDLE(tp)); /* * Process options if not in LISTEN state, * else do it below (after getting remote address). */ if (tp->t_state != TCPS_LISTEN && optp) tcp_dooptions(tp, optp, optlen, th, &to, ifscope); if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { if (to.to_flags & TOF_SCALE) { tp->t_flags |= TF_RCVD_SCALE; tp->requested_s_scale = to.to_requested_s_scale; tp->snd_wnd = th->th_win << tp->snd_scale; tiwin = tp->snd_wnd; } if (to.to_flags & TOF_TS) { tp->t_flags |= TF_RCVD_TSTMP; tp->ts_recent = to.to_tsval; tp->ts_recent_age = tcp_now; } if (to.to_flags & TOF_MSS) tcp_mss(tp, to.to_mss, ifscope); if (tp->sack_enable) { if (!(to.to_flags & TOF_SACK)) tp->sack_enable = 0; else tp->t_flags |= TF_SACK_PERMIT; } } #if TRAFFIC_MGT /* Compute inter-packet arrival jitter. According to RFC 3550, inter-packet * arrival jitter is defined as the difference in packet spacing at the * receiver compared to the sender for a pair of packets. When two packets * of maximum segment size come one after the other with consecutive * sequence numbers, we consider them as packets sent together at the * sender and use them as a pair to compute inter-packet arrival jitter. * This metric indicates the delay induced by the network components due * to queuing in edge/access routers. */ if (tp->t_state == TCPS_ESTABLISHED && (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK|TH_ECE|TH_PUSH)) == TH_ACK && ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && ((to.to_flags & TOF_TS) == 0 || TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && th->th_seq == tp->rcv_nxt && LIST_EMPTY(&tp->t_segq)) { int seg_size = tlen; if (tp->iaj_pktcnt <= IAJ_IGNORE_PKTCNT) { TCP_INC_VAR(tp->iaj_pktcnt, nlropkts); } if (m->m_pkthdr.aux_flags & MAUXF_SW_LRO_PKT) { seg_size = m->m_pkthdr.lro_pktlen; } if ( tp->iaj_size == 0 || seg_size > tp->iaj_size || (seg_size == tp->iaj_size && tp->iaj_rcv_ts == 0)) { /* State related to inter-arrival jitter is uninitialized * or we are trying to find a good first packet to start * computing the metric */ update_iaj_state(tp, seg_size, 0); } else { if (seg_size == tp->iaj_size) { /* Compute inter-arrival jitter taking this packet * as the second packet */ compute_iaj(tp); } if (seg_size < tp->iaj_size) { /* There is a smaller packet in the stream. * Some times the maximum size supported on a path can * change if there is a new link with smaller MTU. * The receiver will not know about this change. * If there are too many packets smaller than iaj_size, * we try to learn the iaj_size again. */ tp->iaj_small_pkt++; if (tp->iaj_small_pkt > RESET_IAJ_SIZE_THRESH) { update_iaj_state(tp, seg_size, 1); } else { CLEAR_IAJ_STATE(tp); } } else { update_iaj_state(tp, seg_size, 0); } } } else { CLEAR_IAJ_STATE(tp); } #endif /* TRAFFIC_MGT */ /* * Header prediction: check for the two common cases * of a uni-directional data xfer. If the packet has * no control flags, is in-sequence, the window didn't * change and we're not retransmitting, it's a * candidate. If the length is zero and the ack moved * forward, we're the sender side of the xfer. Just * free the data acked & wake any higher level process * that was blocked waiting for space. If the length * is non-zero and the ack didn't move, we're the * receiver side. If we're getting packets in-order * (the reassembly queue is empty), add the data to * the socket buffer and note that we need a delayed ack. * Make sure that the hidden state-flags are also off. * Since we check for TCPS_ESTABLISHED above, it can only * be TH_NEEDSYN. */ if (tp->t_state == TCPS_ESTABLISHED && (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK|TH_ECE)) == TH_ACK && ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && ((to.to_flags & TOF_TS) == 0 || TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && tp->snd_nxt == tp->snd_max) { /* * If last ACK falls within this segment's sequence numbers, * record the timestamp. * NOTE that the test is modified according to the latest * proposal of the tcplw@cray.com list (Braden 1993/04/26). */ if ((to.to_flags & TOF_TS) != 0 && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { tp->ts_recent_age = tcp_now; tp->ts_recent = to.to_tsval; } /* Force acknowledgment if we received a FIN */ if (thflags & TH_FIN) tp->t_flags |= TF_ACKNOW; if (tlen == 0) { if (SEQ_GT(th->th_ack, tp->snd_una) && SEQ_LEQ(th->th_ack, tp->snd_max) && tp->snd_cwnd >= tp->snd_ssthresh && (!IN_FASTRECOVERY(tp) && ((!tp->sack_enable && tp->t_dupacks < tcprexmtthresh) || (tp->sack_enable && to.to_nsacks == 0 && TAILQ_EMPTY(&tp->snd_holes))))) { /* * this is a pure ack for outstanding data. */ ++tcpstat.tcps_predack; /* * "bad retransmit" recovery */ if (tp->t_rxtshift == 1 && TSTMP_LT(tcp_now, tp->t_badrxtwin)) { ++tcpstat.tcps_sndrexmitbad; tp->snd_cwnd = tp->snd_cwnd_prev; tp->snd_ssthresh = tp->snd_ssthresh_prev; tp->snd_recover = tp->snd_recover_prev; if (tp->t_flags & TF_WASFRECOVERY) ENTER_FASTRECOVERY(tp); tp->snd_nxt = tp->snd_max; tp->t_badrxtwin = 0; tp->t_rxtshift = 0; tp->rxt_start = 0; tcp_bad_rexmt_fix_sndbuf(tp); DTRACE_TCP5(cc, void, NULL, struct inpcb *, tp->t_inpcb, struct tcpcb *, tp, struct tcphdr *, th, int32_t, TCP_CC_BAD_REXMT_RECOVERY); } /* * Recalculate the transmit timer / rtt. * * Some boxes send broken timestamp replies * during the SYN+ACK phase, ignore * timestamps of 0 or we could calculate a * huge RTT and blow up the retransmit timer. */ if (((to.to_flags & TOF_TS) != 0) && (to.to_tsecr != 0) && TSTMP_GEQ(tcp_now, to.to_tsecr)) { tcp_xmit_timer(tp, tcp_now - to.to_tsecr); } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { tcp_xmit_timer(tp, tcp_now - tp->t_rtttime); } acked = th->th_ack - tp->snd_una; tcpstat.tcps_rcvackpack++; tcpstat.tcps_rcvackbyte += acked; /* Handle an ack that is in sequence during congestion * avoidance phase. The calculations in this function * assume that snd_una is not updated yet. */ if (CC_ALGO(tp)->inseq_ack_rcvd != NULL) CC_ALGO(tp)->inseq_ack_rcvd(tp, th); DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, struct tcphdr *, th, int32_t, TCP_CC_INSEQ_ACK_RCVD); sbdrop(&so->so_snd, acked); tcp_sbsnd_trim(&so->so_snd); if (SEQ_GT(tp->snd_una, tp->snd_recover) && SEQ_LEQ(th->th_ack, tp->snd_recover)) tp->snd_recover = th->th_ack - 1; tp->snd_una = th->th_ack; /* * pull snd_wl2 up to prevent seq wrap relative * to th_ack. */ tp->snd_wl2 = th->th_ack; tp->t_dupacks = 0; m_freem(m); ND6_HINT(tp); /* some progress has been done */ /* * If all outstanding data are acked, stop * retransmit timer, otherwise restart timer * using current (possibly backed-off) value. * If process is waiting for space, * wakeup/selwakeup/signal. If data * are ready to send, let tcp_output * decide between more output or persist. */ if (tp->snd_una == tp->snd_max) tp->t_timer[TCPT_REXMT] = 0; else if (tp->t_timer[TCPT_PERSIST] == 0) tp->t_timer[TCPT_REXMT] = OFFSET_FROM_START(tp, tp->t_rxtcur); if ((tp->t_flagsext & TF_MEASURESNDBW) != 0 && tp->t_bwmeas != NULL) tcp_bwmeas_check(tp); sowwakeup(so); /* has to be done with socket lock held */ if ((so->so_snd.sb_cc) || (tp->t_flags & TF_ACKNOW)) { (void) tcp_output(tp); } tcp_check_timer_state(tp); tcp_unlock(so, 1, 0); KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0); return; } } else if (th->th_ack == tp->snd_una && LIST_EMPTY(&tp->t_segq) && tlen <= tcp_sbspace(tp)) { /* * this is a pure, in-sequence data packet * with nothing on the reassembly queue and * we have enough buffer space to take it. */ /* * If this is a connection in steady state, start * coalescing packets belonging to this flow. */ if (turnoff_lro) { tcp_lro_remove_state(tp->t_inpcb->inp_laddr, tp->t_inpcb->inp_faddr, tp->t_inpcb->inp_lport, tp->t_inpcb->inp_fport); tp->t_flagsext &= ~TF_LRO_OFFLOADED; tp->t_idleat = tp->rcv_nxt; } else if (sw_lro && !mauxf_sw_lro_pkt && !isipv6 && (so->so_flags & SOF_USELRO) && (m->m_pkthdr.rcvif->if_type != IFT_CELLULAR) && (m->m_pkthdr.rcvif->if_type != IFT_LOOP) && ((th->th_seq - tp->irs) > (tp->t_maxseg << lro_start)) && ((tp->t_idleat == 0) || ((th->th_seq - tp->t_idleat) > (tp->t_maxseg << lro_start)))) { tp->t_flagsext |= TF_LRO_OFFLOADED; tcp_start_coalescing(ip, th, tlen); tp->t_idleat = 0; } /* Clean receiver SACK report if present */ if (tp->sack_enable && tp->rcv_numsacks) tcp_clean_sackreport(tp); ++tcpstat.tcps_preddat; tp->rcv_nxt += tlen; /* * Pull snd_wl1 up to prevent seq wrap relative to * th_seq. */ tp->snd_wl1 = th->th_seq; /* * Pull rcv_up up to prevent seq wrap relative to * rcv_nxt. */ tp->rcv_up = tp->rcv_nxt; TCP_INC_VAR(tcpstat.tcps_rcvpack, nlropkts); tcpstat.tcps_rcvbyte += tlen; if (nstat_collect) { if (m->m_pkthdr.aux_flags & MAUXF_SW_LRO_PKT) { locked_add_64(&inp->inp_stat->rxpackets, m->m_pkthdr.lro_npkts); } else { locked_add_64(&inp->inp_stat->rxpackets, 1); } locked_add_64(&inp->inp_stat->rxbytes, tlen); } ND6_HINT(tp); /* some progress has been done */ tcp_sbrcv_grow(tp, &so->so_rcv, &to, tlen); /* * Add data to socket buffer. */ so_recv_data_stat(so, m, 0); m_adj(m, drop_hdrlen); /* delayed header drop */ if (sbappendstream(&so->so_rcv, m)) sorwakeup(so); #if INET6 if (isipv6) { KERNEL_DEBUG(DBG_LAYER_END, ((th->th_dport << 16) | th->th_sport), (((ip6->ip6_src.s6_addr16[0]) << 16) | (ip6->ip6_dst.s6_addr16[0])), th->th_seq, th->th_ack, th->th_win); } else #endif { KERNEL_DEBUG(DBG_LAYER_END, ((th->th_dport << 16) | th->th_sport), (((ip->ip_src.s_addr & 0xffff) << 16) | (ip->ip_dst.s_addr & 0xffff)), th->th_seq, th->th_ack, th->th_win); } TCP_INC_VAR(tp->t_unacksegs, nlropkts); if (DELAY_ACK(tp, th)) { if ((tp->t_flags & TF_DELACK) == 0) { tp->t_flags |= TF_DELACK; tp->t_timer[TCPT_DELACK] = OFFSET_FROM_START(tp, tcp_delack); } } else { tp->t_flags |= TF_ACKNOW; tcp_output(tp); } tcp_check_timer_state(tp); tcp_unlock(so, 1, 0); KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0); return; } } /* * Calculate amount of space in receive window, * and then do TCP input processing. * Receive window is amount of space in rcv queue, * but not less than advertised window. */ lck_mtx_assert(&((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED); { int win; win = tcp_sbspace(tp); if (win < 0) win = 0; else { /* clip rcv window to 4K for modems */ if (tp->t_flags & TF_SLOWLINK && slowlink_wsize > 0) win = min(win, slowlink_wsize); } tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); } switch (tp->t_state) { /* * Initialize tp->rcv_nxt, and tp->irs, select an initial * tp->iss, and send a segment: * * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. * Fill in remote peer address fields if not previously specified. * Enter SYN_RECEIVED state, and process any other fields of this * segment in this state. */ case TCPS_LISTEN: { register struct sockaddr_in *sin; #if INET6 register struct sockaddr_in6 *sin6; #endif lck_mtx_assert(&((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED); #if INET6 if (isipv6) { MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6, M_SONAME, M_NOWAIT); if (sin6 == NULL) goto drop; bzero(sin6, sizeof(*sin6)); sin6->sin6_family = AF_INET6; sin6->sin6_len = sizeof(*sin6); sin6->sin6_addr = ip6->ip6_src; sin6->sin6_port = th->th_sport; laddr6 = inp->in6p_laddr; if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) inp->in6p_laddr = ip6->ip6_dst; if (in6_pcbconnect(inp, (struct sockaddr *)sin6, proc0)) { inp->in6p_laddr = laddr6; FREE(sin6, M_SONAME); goto drop; } FREE(sin6, M_SONAME); } else #endif { lck_mtx_assert(&((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED); MALLOC(sin, struct sockaddr_in *, sizeof *sin, M_SONAME, M_NOWAIT); if (sin == NULL) goto drop; sin->sin_family = AF_INET; sin->sin_len = sizeof(*sin); sin->sin_addr = ip->ip_src; sin->sin_port = th->th_sport; bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); laddr = inp->inp_laddr; if (inp->inp_laddr.s_addr == INADDR_ANY) inp->inp_laddr = ip->ip_dst; if (in_pcbconnect(inp, (struct sockaddr *)sin, proc0, NULL)) { inp->inp_laddr = laddr; FREE(sin, M_SONAME); goto drop; } FREE(sin, M_SONAME); } tcp_dooptions(tp, optp, optlen, th, &to, ifscope); if (tp->sack_enable) { if (!(to.to_flags & TOF_SACK)) tp->sack_enable = 0; else tp->t_flags |= TF_SACK_PERMIT; } if (iss) tp->iss = iss; else { tp->iss = tcp_new_isn(tp); } tp->irs = th->th_seq; tcp_sendseqinit(tp); tcp_rcvseqinit(tp); tp->snd_recover = tp->snd_una; /* * Initialization of the tcpcb for transaction; * set SND.WND = SEG.WND, * initialize CCsend and CCrecv. */ tp->snd_wnd = tiwin; /* initial send-window */ tp->t_flags |= TF_ACKNOW; tp->t_unacksegs = 0; DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_SYN_RECEIVED); tp->t_state = TCPS_SYN_RECEIVED; tp->t_timer[TCPT_KEEP] = OFFSET_FROM_START(tp, tp->t_keepinit ? tp->t_keepinit : tcp_keepinit); dropsocket = 0; /* committed to socket */ if (inp->inp_flowhash == 0) inp->inp_flowhash = inp_calc_flowhash(inp); /* reset the incomp processing flag */ so->so_flags &= ~(SOF_INCOMP_INPROGRESS); tcpstat.tcps_accepts++; if ((thflags & (TH_ECE | TH_CWR)) == (TH_ECE | TH_CWR)) { /* ECN-setup SYN */ tp->ecn_flags |= (TE_SETUPRECEIVED | TE_SENDIPECT); } #if CONFIG_IFEF_NOWINDOWSCALE if (tcp_obey_ifef_nowindowscale && m->m_pkthdr.rcvif != NULL && (m->m_pkthdr.rcvif->if_eflags & IFEF_NOWINDOWSCALE)) { /* Window scaling is not enabled on this interface */ tp->t_flags &= ~TF_REQ_SCALE; } #endif goto trimthenstep6; } /* * If the state is SYN_RECEIVED: * if seg contains an ACK, but not for our SYN/ACK, send a RST. */ case TCPS_SYN_RECEIVED: if ((thflags & TH_ACK) && (SEQ_LEQ(th->th_ack, tp->snd_una) || SEQ_GT(th->th_ack, tp->snd_max))) { rstreason = BANDLIM_RST_OPENPORT; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->ooopacket, 1); goto dropwithreset; } break; /* * If the state is SYN_SENT: * if seg contains an ACK, but not for our SYN, drop the input. * if seg contains a RST, then drop the connection. * if seg does not contain SYN, then drop it. * Otherwise this is an acceptable SYN segment * initialize tp->rcv_nxt and tp->irs * if seg contains ack then advance tp->snd_una * if SYN has been acked change to ESTABLISHED else SYN_RCVD state * arrange for segment to be acked (eventually) * continue processing rest of data/controls, beginning with URG */ case TCPS_SYN_SENT: if ((thflags & TH_ACK) && (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) { rstreason = BANDLIM_UNLIMITED; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->ooopacket, 1); goto dropwithreset; } if (thflags & TH_RST) { if ((thflags & TH_ACK) != 0) { soevent(so, (SO_FILT_HINT_LOCKED | SO_FILT_HINT_CONNRESET)); tp = tcp_drop(tp, ECONNREFUSED); postevent(so, 0, EV_RESET); } goto drop; } if ((thflags & TH_SYN) == 0) goto drop; tp->snd_wnd = th->th_win; /* initial send window */ tp->irs = th->th_seq; tcp_rcvseqinit(tp); if (thflags & TH_ACK) { tcpstat.tcps_connects++; if ((thflags & (TH_ECE | TH_CWR)) == (TH_ECE)) { /* ECN-setup SYN-ACK */ tp->ecn_flags |= TE_SETUPRECEIVED; } else { /* non-ECN-setup SYN-ACK */ tp->ecn_flags &= ~TE_SENDIPECT; } #if CONFIG_MACF_NET && CONFIG_MACF_SOCKET /* XXXMAC: recursive lock: SOCK_LOCK(so); */ mac_socketpeer_label_associate_mbuf(m, so); /* XXXMAC: SOCK_UNLOCK(so); */ #endif /* Do window scaling on this connection? */ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { tp->snd_scale = tp->requested_s_scale; tp->rcv_scale = tp->request_r_scale; } tp->rcv_adv += min(tp->rcv_wnd, TCP_MAXWIN << tp->rcv_scale); tp->snd_una++; /* SYN is acked */ /* * If there's data, delay ACK; if there's also a FIN * ACKNOW will be turned on later. */ TCP_INC_VAR(tp->t_unacksegs, nlropkts); if (DELAY_ACK(tp, th) && tlen != 0 ) { if ((tp->t_flags & TF_DELACK) == 0) { tp->t_flags |= TF_DELACK; tp->t_timer[TCPT_DELACK] = OFFSET_FROM_START(tp, tcp_delack); } } else { tp->t_flags |= TF_ACKNOW; } /* * Received in SYN_SENT[*] state. * Transitions: * SYN_SENT --> ESTABLISHED * SYN_SENT* --> FIN_WAIT_1 */ tp->t_starttime = tcp_now; tcp_sbrcv_tstmp_check(tp); if (tp->t_flags & TF_NEEDFIN) { DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_FIN_WAIT_1); tp->t_state = TCPS_FIN_WAIT_1; tp->t_flags &= ~TF_NEEDFIN; thflags &= ~TH_SYN; } else { DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_ESTABLISHED); tp->t_state = TCPS_ESTABLISHED; tp->t_timer[TCPT_KEEP] = OFFSET_FROM_START(tp, TCP_KEEPIDLE(tp)); if (nstat_collect) nstat_route_connect_success(tp->t_inpcb->inp_route.ro_rt); } isconnected = TRUE; } else { /* * Received initial SYN in SYN-SENT[*] state => simul- * taneous open. If segment contains CC option and there is * a cached CC, apply TAO test; if it succeeds, connection is * half-synchronized. Otherwise, do 3-way handshake: * SYN-SENT -> SYN-RECEIVED * SYN-SENT* -> SYN-RECEIVED* */ tp->t_flags |= TF_ACKNOW; tp->t_timer[TCPT_REXMT] = 0; DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_SYN_RECEIVED); tp->t_state = TCPS_SYN_RECEIVED; } trimthenstep6: /* * Advance th->th_seq to correspond to first data byte. * If data, trim to stay within window, * dropping FIN if necessary. */ th->th_seq++; if (tlen > tp->rcv_wnd) { todrop = tlen - tp->rcv_wnd; m_adj(m, -todrop); tlen = tp->rcv_wnd; thflags &= ~TH_FIN; tcpstat.tcps_rcvpackafterwin++; tcpstat.tcps_rcvbyteafterwin += todrop; } tp->snd_wl1 = th->th_seq - 1; tp->rcv_up = th->th_seq; /* * Client side of transaction: already sent SYN and data. * If the remote host used T/TCP to validate the SYN, * our data will be ACK'd; if so, enter normal data segment * processing in the middle of step 5, ack processing. * Otherwise, goto step 6. */ if (thflags & TH_ACK) goto process_ACK; goto step6; /* * If the state is LAST_ACK or CLOSING or TIME_WAIT: * do normal processing. * * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. */ case TCPS_LAST_ACK: case TCPS_CLOSING: case TCPS_TIME_WAIT: break; /* continue normal processing */ /* Received a SYN while connection is already established. * This is a "half open connection and other anomalies" described * in RFC793 page 34, send an ACK so the remote reset the connection * or recovers by adjusting its sequence numberering */ case TCPS_ESTABLISHED: if (thflags & TH_SYN) goto dropafterack; break; } /* * States other than LISTEN or SYN_SENT. * First check the RST flag and sequence number since reset segments * are exempt from the timestamp and connection count tests. This * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix * below which allowed reset segments in half the sequence space * to fall though and be processed (which gives forged reset * segments with a random sequence number a 50 percent chance of * killing a connection). * Then check timestamp, if present. * Then check the connection count, if present. * Then check that at least some bytes of segment are within * receive window. If segment begins before rcv_nxt, * drop leading data (and SYN); if nothing left, just ack. * * * If the RST bit is set, check the sequence number to see * if this is a valid reset segment. * RFC 793 page 37: * In all states except SYN-SENT, all reset (RST) segments * are validated by checking their SEQ-fields. A reset is * valid if its sequence number is in the window. * Note: this does not take into account delayed ACKs, so * we should test against last_ack_sent instead of rcv_nxt. * The sequence number in the reset segment is normally an * echo of our outgoing acknowlegement numbers, but some hosts * send a reset with the sequence number at the rightmost edge * of our receive window, and we have to handle this case. * Note 2: Paul Watson's paper "Slipping in the Window" has shown * that brute force RST attacks are possible. To combat this, * we use a much stricter check while in the ESTABLISHED state, * only accepting RSTs where the sequence number is equal to * last_ack_sent. In all other states (the states in which a * RST is more likely), the more permissive check is used. * If we have multiple segments in flight, the intial reset * segment sequence numbers will be to the left of last_ack_sent, * but they will eventually catch up. * In any case, it never made sense to trim reset segments to * fit the receive window since RFC 1122 says: * 4.2.2.12 RST Segment: RFC-793 Section 3.4 * * A TCP SHOULD allow a received RST segment to include data. * * DISCUSSION * It has been suggested that a RST segment could contain * ASCII text that encoded and explained the cause of the * RST. No standard has yet been established for such * data. * * If the reset segment passes the sequence number test examine * the state: * SYN_RECEIVED STATE: * If passive open, return to LISTEN state. * If active open, inform user that connection was refused. * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: * Inform user that connection was reset, and close tcb. * CLOSING, LAST_ACK STATES: * Close the tcb. * TIME_WAIT STATE: * Drop the segment - see Stevens, vol. 2, p. 964 and * RFC 1337. * * Radar 4803931: Allows for the case where we ACKed the FIN but * there is already a RST in flight from the peer. * In that case, accept the RST for non-established * state if it's one off from last_ack_sent. */ if (thflags & TH_RST) { if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || (tp->rcv_wnd == 0 && ((tp->last_ack_sent == th->th_seq) || ((tp->last_ack_sent -1) == th->th_seq)))) { switch (tp->t_state) { case TCPS_SYN_RECEIVED: if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->rstinsynrcv, 1); so->so_error = ECONNREFUSED; goto close; case TCPS_ESTABLISHED: if (tp->last_ack_sent != th->th_seq) { tcpstat.tcps_badrst++; goto drop; } case TCPS_FIN_WAIT_1: case TCPS_CLOSE_WAIT: /* Drop through ... */ case TCPS_FIN_WAIT_2: so->so_error = ECONNRESET; close: postevent(so, 0, EV_RESET); DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_CLOSED); soevent(so, (SO_FILT_HINT_LOCKED | SO_FILT_HINT_CONNRESET)); tp->t_state = TCPS_CLOSED; tcpstat.tcps_drops++; tp = tcp_close(tp); break; case TCPS_CLOSING: case TCPS_LAST_ACK: tp = tcp_close(tp); break; case TCPS_TIME_WAIT: break; } } goto drop; } /* * RFC 1323 PAWS: If we have a timestamp reply on this segment * and it's less than ts_recent, drop it. */ if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && TSTMP_LT(to.to_tsval, tp->ts_recent)) { /* Check to see if ts_recent is over 24 days old. */ if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) { /* * Invalidate ts_recent. If this segment updates * ts_recent, the age will be reset later and ts_recent * will get a valid value. If it does not, setting * ts_recent to zero will at least satisfy the * requirement that zero be placed in the timestamp * echo reply when ts_recent isn't valid. The * age isn't reset until we get a valid ts_recent * because we don't want out-of-order segments to be * dropped when ts_recent is old. */ tp->ts_recent = 0; } else { tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += tlen; tcpstat.tcps_pawsdrop++; if (nstat_collect) { nstat_route_rx(tp->t_inpcb->inp_route.ro_rt, 1, tlen, NSTAT_RX_FLAG_DUPLICATE); locked_add_64(&inp->inp_stat->rxpackets, 1); locked_add_64(&inp->inp_stat->rxbytes, tlen); tp->t_stat.rxduplicatebytes += tlen; } if (tlen) goto dropafterack; goto drop; } } /* * In the SYN-RECEIVED state, validate that the packet belongs to * this connection before trimming the data to fit the receive * window. Check the sequence number versus IRS since we know * the sequence numbers haven't wrapped. This is a partial fix * for the "LAND" DoS attack. */ if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { rstreason = BANDLIM_RST_OPENPORT; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->dospacket, 1); goto dropwithreset; } todrop = tp->rcv_nxt - th->th_seq; if (todrop > 0) { if (thflags & TH_SYN) { thflags &= ~TH_SYN; th->th_seq++; if (th->th_urp > 1) th->th_urp--; else thflags &= ~TH_URG; todrop--; } /* * Following if statement from Stevens, vol. 2, p. 960. */ if (todrop > tlen || (todrop == tlen && (thflags & TH_FIN) == 0)) { /* * Any valid FIN must be to the left of the window. * At this point the FIN must be a duplicate or out * of sequence; drop it. */ thflags &= ~TH_FIN; /* * Send an ACK to resynchronize and drop any data. * But keep on processing for RST or ACK. */ tp->t_flags |= TF_ACKNOW; if (todrop == 1) { /* This could be a keepalive */ soevent(so, SO_FILT_HINT_LOCKED | SO_FILT_HINT_KEEPALIVE); } todrop = tlen; tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += todrop; } else { tcpstat.tcps_rcvpartduppack++; tcpstat.tcps_rcvpartdupbyte += todrop; } if (nstat_collect) { nstat_route_rx(tp->t_inpcb->inp_route.ro_rt, 1, todrop, NSTAT_RX_FLAG_DUPLICATE); locked_add_64(&inp->inp_stat->rxpackets, 1); locked_add_64(&inp->inp_stat->rxbytes, todrop); tp->t_stat.rxduplicatebytes += todrop; } drop_hdrlen += todrop; /* drop from the top afterwards */ th->th_seq += todrop; tlen -= todrop; if (th->th_urp > todrop) th->th_urp -= todrop; else { thflags &= ~TH_URG; th->th_urp = 0; } } /* * If new data are received on a connection after the * user processes are gone, then RST the other end. */ if ((so->so_state & SS_NOFDREF) && tp->t_state > TCPS_CLOSE_WAIT && tlen) { tp = tcp_close(tp); tcpstat.tcps_rcvafterclose++; rstreason = BANDLIM_UNLIMITED; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->cleanup, 1); goto dropwithreset; } /* * If segment ends after window, drop trailing data * (and PUSH and FIN); if nothing left, just ACK. */ todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); if (todrop > 0) { tcpstat.tcps_rcvpackafterwin++; if (todrop >= tlen) { tcpstat.tcps_rcvbyteafterwin += tlen; /* * If a new connection request is received * while in TIME_WAIT, drop the old connection * and start over if the sequence numbers * are above the previous ones. */ if (thflags & TH_SYN && tp->t_state == TCPS_TIME_WAIT && SEQ_GT(th->th_seq, tp->rcv_nxt)) { iss = tcp_new_isn(tp); tp = tcp_close(tp); tcp_unlock(so, 1, 0); goto findpcb; } /* * If window is closed can only take segments at * window edge, and have to drop data and PUSH from * incoming segments. Continue processing, but * remember to ack. Otherwise, drop segment * and ack. */ if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { tp->t_flags |= TF_ACKNOW; tcpstat.tcps_rcvwinprobe++; } else goto dropafterack; } else tcpstat.tcps_rcvbyteafterwin += todrop; m_adj(m, -todrop); tlen -= todrop; thflags &= ~(TH_PUSH|TH_FIN); } /* * If last ACK falls within this segment's sequence numbers, * record its timestamp. * NOTE: * 1) That the test incorporates suggestions from the latest * proposal of the tcplw@cray.com list (Braden 1993/04/26). * 2) That updating only on newer timestamps interferes with * our earlier PAWS tests, so this check should be solely * predicated on the sequence space of this segment. * 3) That we modify the segment boundary check to be * Last.ACK.Sent <= SEG.SEQ + SEG.Len * instead of RFC1323's * Last.ACK.Sent < SEG.SEQ + SEG.Len, * This modified check allows us to overcome RFC1323's * limitations as described in Stevens TCP/IP Illustrated * Vol. 2 p.869. In such cases, we can still calculate the * RTT correctly when RCV.NXT == Last.ACK.Sent. */ if ((to.to_flags & TOF_TS) != 0 && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + ((thflags & (TH_SYN|TH_FIN)) != 0))) { tp->ts_recent_age = tcp_now; tp->ts_recent = to.to_tsval; } /* * If a SYN is in the window, then this is an * error and we send an RST and drop the connection. */ if (thflags & TH_SYN) { tp = tcp_drop(tp, ECONNRESET); rstreason = BANDLIM_UNLIMITED; postevent(so, 0, EV_RESET); if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->synwindow, 1); goto dropwithreset; } /* * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN * flag is on (half-synchronized state), then queue data for * later processing; else drop segment and return. */ if ((thflags & TH_ACK) == 0) { if (tp->t_state == TCPS_SYN_RECEIVED || (tp->t_flags & TF_NEEDSYN)) goto step6; else if (tp->t_flags & TF_ACKNOW) goto dropafterack; else goto drop; } /* * Ack processing. */ switch (tp->t_state) { /* * In SYN_RECEIVED state, the ack ACKs our SYN, so enter * ESTABLISHED state and continue processing. * The ACK was checked above. */ case TCPS_SYN_RECEIVED: tcpstat.tcps_connects++; /* Do window scaling? */ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { tp->snd_scale = tp->requested_s_scale; tp->rcv_scale = tp->request_r_scale; tp->snd_wnd = th->th_win << tp->snd_scale; tiwin = tp->snd_wnd; } /* * Make transitions: * SYN-RECEIVED -> ESTABLISHED * SYN-RECEIVED* -> FIN-WAIT-1 */ tp->t_starttime = tcp_now; tcp_sbrcv_tstmp_check(tp); if (tp->t_flags & TF_NEEDFIN) { DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_FIN_WAIT_1); tp->t_state = TCPS_FIN_WAIT_1; tp->t_flags &= ~TF_NEEDFIN; } else { DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_ESTABLISHED); tp->t_state = TCPS_ESTABLISHED; tp->t_timer[TCPT_KEEP] = OFFSET_FROM_START(tp, TCP_KEEPIDLE(tp)); if (nstat_collect) nstat_route_connect_success(tp->t_inpcb->inp_route.ro_rt); } /* * If segment contains data or ACK, will call tcp_reass() * later; if not, do so now to pass queued data to user. */ if (tlen == 0 && (thflags & TH_FIN) == 0) (void) tcp_reass(tp, (struct tcphdr *)0, &tlen, (struct mbuf *)0); tp->snd_wl1 = th->th_seq - 1; /* FALLTHROUGH */ isconnected = TRUE; /* * In ESTABLISHED state: drop duplicate ACKs; ACK out of range * ACKs. If the ack is in the range * tp->snd_una < th->th_ack <= tp->snd_max * then advance tp->snd_una to th->th_ack and drop * data from the retransmission queue. If this ACK reflects * more up to date window information we update our window information. */ case TCPS_ESTABLISHED: case TCPS_FIN_WAIT_1: case TCPS_FIN_WAIT_2: case TCPS_CLOSE_WAIT: case TCPS_CLOSING: case TCPS_LAST_ACK: case TCPS_TIME_WAIT: if (SEQ_GT(th->th_ack, tp->snd_max)) { tcpstat.tcps_rcvacktoomuch++; goto dropafterack; } if (tp->sack_enable && (to.to_nsacks > 0 || !TAILQ_EMPTY(&tp->snd_holes))) tcp_sack_doack(tp, &to, th->th_ack); if (SEQ_LEQ(th->th_ack, tp->snd_una)) { if (tlen == 0 && tiwin == tp->snd_wnd) { tcpstat.tcps_rcvdupack++; /* * If we have outstanding data (other than * a window probe), this is a completely * duplicate ack (ie, window info didn't * change), the ack is the biggest we've * seen and we've seen exactly our rexmt * threshhold of them, assume a packet * has been dropped and retransmit it. * Kludge snd_nxt & the congestion * window so we send only this one * packet. * * We know we're losing at the current * window size so do congestion avoidance * (set ssthresh to half the current window * and pull our congestion window back to * the new ssthresh). * * Dup acks mean that packets have left the * network (they're now cached at the receiver) * so bump cwnd by the amount in the receiver * to keep a constant cwnd packets in the * network. */ if (tp->t_timer[TCPT_REXMT] == 0 || th->th_ack != tp->snd_una) tp->t_dupacks = 0; else if (++tp->t_dupacks > tcprexmtthresh || IN_FASTRECOVERY(tp)) { if (tp->sack_enable && IN_FASTRECOVERY(tp)) { int awnd; /* * Compute the amount of data in flight first. * We can inject new data into the pipe iff * we have less than 1/2 the original window's * worth of data in flight. */ awnd = (tp->snd_nxt - tp->snd_fack) + tp->sackhint.sack_bytes_rexmit; if (awnd < tp->snd_ssthresh) { tp->snd_cwnd += tp->t_maxseg; if (tp->snd_cwnd > tp->snd_ssthresh) tp->snd_cwnd = tp->snd_ssthresh; } } else tp->snd_cwnd += tp->t_maxseg; DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, struct tcphdr *, th, int32_t, TCP_CC_IN_FASTRECOVERY); (void) tcp_output(tp); goto drop; } else if (tp->t_dupacks == tcprexmtthresh) { tcp_seq onxt = tp->snd_nxt; /* * If we're doing sack, check to * see if we're already in sack * recovery. If we're not doing sack, * check to see if we're in newreno * recovery. */ if (tp->sack_enable) { if (IN_FASTRECOVERY(tp)) { tp->t_dupacks = 0; break; } } else { if (SEQ_LEQ(th->th_ack, tp->snd_recover)) { tp->t_dupacks = 0; break; } } /* * If the current tcp cc module has * defined a hook for tasks to run * before entering FR, call it */ if (CC_ALGO(tp)->pre_fr != NULL) CC_ALGO(tp)->pre_fr(tp); ENTER_FASTRECOVERY(tp); tp->snd_recover = tp->snd_max; tp->t_timer[TCPT_REXMT] = 0; tp->t_rtttime = 0; if ((tp->ecn_flags & TE_ECN_ON) == TE_ECN_ON) { tp->ecn_flags |= TE_SENDCWR; } if (tp->sack_enable) { tcpstat.tcps_sack_recovery_episode++; tp->sack_newdata = tp->snd_nxt; tp->snd_cwnd = tp->t_maxseg; DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, struct tcphdr *, th, int32_t, TCP_CC_ENTER_FASTRECOVERY); (void) tcp_output(tp); goto drop; } tp->snd_nxt = th->th_ack; tp->snd_cwnd = tp->t_maxseg; (void) tcp_output(tp); tp->snd_cwnd = tp->snd_ssthresh + tp->t_maxseg * tp->t_dupacks; if (SEQ_GT(onxt, tp->snd_nxt)) tp->snd_nxt = onxt; DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, struct tcphdr *, th, int32_t, TCP_CC_ENTER_FASTRECOVERY); goto drop; } } else tp->t_dupacks = 0; break; } /* * If the congestion window was inflated to account * for the other side's cached packets, retract it. */ if (IN_FASTRECOVERY(tp)) { if (SEQ_LT(th->th_ack, tp->snd_recover)) { if (tp->sack_enable) tcp_sack_partialack(tp, th); else tcp_newreno_partial_ack(tp, th); DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, struct tcphdr *, th, int32_t, TCP_CC_PARTIAL_ACK); } else { EXIT_FASTRECOVERY(tp); if (CC_ALGO(tp)->post_fr != NULL) CC_ALGO(tp)->post_fr(tp, th); tp->t_dupacks = 0; DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, struct tcphdr *, th, int32_t, TCP_CC_EXIT_FASTRECOVERY); } } else { /* * We were not in fast recovery. Reset the duplicate ack * counter. */ tp->t_dupacks = 0; } /* * If we reach this point, ACK is not a duplicate, * i.e., it ACKs something we sent. */ if (tp->t_flags & TF_NEEDSYN) { /* * T/TCP: Connection was half-synchronized, and our * SYN has been ACK'd (so connection is now fully * synchronized). Go to non-starred state, * increment snd_una for ACK of SYN, and check if * we can do window scaling. */ tp->t_flags &= ~TF_NEEDSYN; tp->snd_una++; /* Do window scaling? */ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { tp->snd_scale = tp->requested_s_scale; tp->rcv_scale = tp->request_r_scale; } } process_ACK: acked = th->th_ack - tp->snd_una; tcpstat.tcps_rcvackpack++; tcpstat.tcps_rcvackbyte += acked; /* * If we just performed our first retransmit, and the ACK * arrives within our recovery window, then it was a mistake * to do the retransmit in the first place. Recover our * original cwnd and ssthresh, and proceed to transmit where * we left off. */ if (tp->t_rxtshift == 1 && TSTMP_LT(tcp_now, tp->t_badrxtwin)) { ++tcpstat.tcps_sndrexmitbad; tp->snd_cwnd = tp->snd_cwnd_prev; tp->snd_ssthresh = tp->snd_ssthresh_prev; tp->snd_recover = tp->snd_recover_prev; if (tp->t_flags & TF_WASFRECOVERY) ENTER_FASTRECOVERY(tp); tp->snd_nxt = tp->snd_max; tp->t_badrxtwin = 0; /* XXX probably not required */ tp->t_rxtshift = 0; tp->rxt_start = 0; tcp_bad_rexmt_fix_sndbuf(tp); DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, struct tcphdr *, th, int32_t, TCP_CC_BAD_REXMT_RECOVERY); } /* * If we have a timestamp reply, update smoothed * round trip time. If no timestamp is present but * transmit timer is running and timed sequence * number was acked, update smoothed round trip time. * Since we now have an rtt measurement, cancel the * timer backoff (cf., Phil Karn's retransmit alg.). * Recompute the initial retransmit timer. * Also makes sure we have a valid time stamp in hand * * Some boxes send broken timestamp replies * during the SYN+ACK phase, ignore * timestamps of 0 or we could calculate a * huge RTT and blow up the retransmit timer. */ if (((to.to_flags & TOF_TS) != 0) && (to.to_tsecr != 0) && TSTMP_GEQ(tcp_now, to.to_tsecr)) { tcp_xmit_timer(tp, tcp_now - to.to_tsecr); } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { tcp_xmit_timer(tp, tcp_now - tp->t_rtttime); } /* * If all outstanding data is acked, stop retransmit * timer and remember to restart (more output or persist). * If there is more data to be acked, restart retransmit * timer, using current (possibly backed-off) value. */ if (th->th_ack == tp->snd_max) { tp->t_timer[TCPT_REXMT] = 0; needoutput = 1; } else if (tp->t_timer[TCPT_PERSIST] == 0) tp->t_timer[TCPT_REXMT] = OFFSET_FROM_START(tp, tp->t_rxtcur); /* * If no data (only SYN) was ACK'd, * skip rest of ACK processing. */ if (acked == 0) goto step6; if ((thflags & TH_ECE) != 0 && ((tp->ecn_flags & TE_ECN_ON) == TE_ECN_ON)) { /* * Reduce the congestion window if we haven't done so. */ if (!tp->sack_enable && !IN_FASTRECOVERY(tp) && SEQ_GEQ(th->th_ack, tp->snd_recover)) { tcp_reduce_congestion_window(tp); DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, struct tcphdr *, th, int32_t, TCP_CC_ECN_RCVD); } } /* * When new data is acked, open the congestion window. * The specifics of how this is achieved are up to the * congestion control algorithm in use for this connection. * * The calculations in this function assume that snd_una is * not updated yet. */ if (!IN_FASTRECOVERY(tp)) { if (CC_ALGO(tp)->ack_rcvd != NULL) CC_ALGO(tp)->ack_rcvd(tp, th); DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, struct tcphdr *, th, int32_t, TCP_CC_ACK_RCVD); } if (acked > so->so_snd.sb_cc) { tp->snd_wnd -= so->so_snd.sb_cc; sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); ourfinisacked = 1; } else { sbdrop(&so->so_snd, acked); tcp_sbsnd_trim(&so->so_snd); tp->snd_wnd -= acked; ourfinisacked = 0; } /* detect una wraparound */ if ( !IN_FASTRECOVERY(tp) && SEQ_GT(tp->snd_una, tp->snd_recover) && SEQ_LEQ(th->th_ack, tp->snd_recover)) tp->snd_recover = th->th_ack - 1; if (IN_FASTRECOVERY(tp) && SEQ_GEQ(th->th_ack, tp->snd_recover)) EXIT_FASTRECOVERY(tp); tp->snd_una = th->th_ack; if (tp->sack_enable) { if (SEQ_GT(tp->snd_una, tp->snd_recover)) tp->snd_recover = tp->snd_una; } if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; if ((tp->t_flagsext & TF_MEASURESNDBW) != 0 && tp->t_bwmeas != NULL) tcp_bwmeas_check(tp); /* * sowwakeup must happen after snd_una, et al. are updated so that * the sequence numbers are in sync with so_snd */ sowwakeup(so); switch (tp->t_state) { /* * In FIN_WAIT_1 STATE in addition to the processing * for the ESTABLISHED state if our FIN is now acknowledged * then enter FIN_WAIT_2. */ case TCPS_FIN_WAIT_1: if (ourfinisacked) { /* * If we can't receive any more * data, then closing user can proceed. * Starting the timer is contrary to the * specification, but if we don't get a FIN * we'll hang forever. */ if (so->so_state & SS_CANTRCVMORE) { add_to_time_wait(tp, tcp_maxidle); isconnected = FALSE; isdisconnected = TRUE; } DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_FIN_WAIT_2); tp->t_state = TCPS_FIN_WAIT_2; /* fall through and make sure we also recognize data ACKed with the FIN */ } tp->t_flags |= TF_ACKNOW; break; /* * In CLOSING STATE in addition to the processing for * the ESTABLISHED state if the ACK acknowledges our FIN * then enter the TIME-WAIT state, otherwise ignore * the segment. */ case TCPS_CLOSING: if (ourfinisacked) { DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_TIME_WAIT); tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); /* Shorten TIME_WAIT [RFC-1644, p.28] */ if (tp->cc_recv != 0 && ((int)(tcp_now - tp->t_starttime)) < tcp_msl) add_to_time_wait(tp, tp->t_rxtcur * TCPTV_TWTRUNC); else add_to_time_wait(tp, 2 * tcp_msl); isconnected = FALSE; isdisconnected = TRUE; } tp->t_flags |= TF_ACKNOW; break; /* * In LAST_ACK, we may still be waiting for data to drain * and/or to be acked, as well as for the ack of our FIN. * If our FIN is now acknowledged, delete the TCB, * enter the closed state and return. */ case TCPS_LAST_ACK: if (ourfinisacked) { tp = tcp_close(tp); goto drop; } break; /* * In TIME_WAIT state the only thing that should arrive * is a retransmission of the remote FIN. Acknowledge * it and restart the finack timer. */ case TCPS_TIME_WAIT: add_to_time_wait(tp, 2 * tcp_msl); goto dropafterack; } } step6: /* * Update window information. * Don't look at window if no ACK: TAC's send garbage on first SYN. */ if ((thflags & TH_ACK) && (SEQ_LT(tp->snd_wl1, th->th_seq) || (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { /* keep track of pure window updates */ if (tlen == 0 && tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) tcpstat.tcps_rcvwinupd++; tp->snd_wnd = tiwin; tp->snd_wl1 = th->th_seq; tp->snd_wl2 = th->th_ack; if (tp->snd_wnd > tp->max_sndwnd) tp->max_sndwnd = tp->snd_wnd; needoutput = 1; } /* * Process segments with URG. */ if ((thflags & TH_URG) && th->th_urp && TCPS_HAVERCVDFIN(tp->t_state) == 0) { /* * This is a kludge, but if we receive and accept * random urgent pointers, we'll crash in * soreceive. It's hard to imagine someone * actually wanting to send this much urgent data. */ if (th->th_urp + so->so_rcv.sb_cc > sb_max) { th->th_urp = 0; /* XXX */ thflags &= ~TH_URG; /* XXX */ goto dodata; /* XXX */ } /* * If this segment advances the known urgent pointer, * then mark the data stream. This should not happen * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since * a FIN has been received from the remote side. * In these states we ignore the URG. * * According to RFC961 (Assigned Protocols), * the urgent pointer points to the last octet * of urgent data. We continue, however, * to consider it to indicate the first octet * of data past the urgent section as the original * spec states (in one of two places). */ if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { tp->rcv_up = th->th_seq + th->th_urp; so->so_oobmark = so->so_rcv.sb_cc + (tp->rcv_up - tp->rcv_nxt) - 1; if (so->so_oobmark == 0) { so->so_state |= SS_RCVATMARK; postevent(so, 0, EV_OOB); } sohasoutofband(so); tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); } /* * Remove out of band data so doesn't get presented to user. * This can happen independent of advancing the URG pointer, * but if two URG's are pending at once, some out-of-band * data may creep in... ick. */ if (th->th_urp <= (u_int32_t)tlen #if SO_OOBINLINE && (so->so_options & SO_OOBINLINE) == 0 #endif ) tcp_pulloutofband(so, th, m, drop_hdrlen); /* hdr drop is delayed */ } else { /* * If no out of band data is expected, * pull receive urgent pointer along * with the receive window. */ if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) tp->rcv_up = tp->rcv_nxt; } dodata: /* Set socket's connect or disconnect state correcly before doing data. * The following might unlock the socket if there is an upcall or a socket * filter. */ if (isconnected) { soisconnected(so); } else if (isdisconnected) { soisdisconnected(so); } /* Let's check the state of pcb just to make sure that it did not get closed * when we unlocked above */ if (inp->inp_state == INPCB_STATE_DEAD) { /* Just drop the packet that we are processing and return */ goto drop; } /* * Process the segment text, merging it into the TCP sequencing queue, * and arranging for acknowledgment of receipt if necessary. * This process logically involves adjusting tp->rcv_wnd as data * is presented to the user (this happens in tcp_usrreq.c, * case PRU_RCVD). If a FIN has already been received on this * connection then we just ignore the text. */ if ((tlen || (thflags & TH_FIN)) && TCPS_HAVERCVDFIN(tp->t_state) == 0) { tcp_seq save_start = th->th_seq; tcp_seq save_end = th->th_seq + tlen; m_adj(m, drop_hdrlen); /* delayed header drop */ /* * Insert segment which includes th into TCP reassembly queue * with control block tp. Set thflags to whether reassembly now * includes a segment with FIN. This handles the common case * inline (segment is the next to be received on an established * connection, and the queue is empty), avoiding linkage into * and removal from the queue and repetition of various * conversions. * Set DELACK for segments received in order, but ack * immediately when segments are out of order (so * fast retransmit can work). */ if (th->th_seq == tp->rcv_nxt && LIST_EMPTY(&tp->t_segq) && TCPS_HAVEESTABLISHED(tp->t_state)) { TCP_INC_VAR(tp->t_unacksegs, nlropkts); if (DELAY_ACK(tp, th) && ((tp->t_flags & TF_ACKNOW) == 0) ) { if ((tp->t_flags & TF_DELACK) == 0) { tp->t_flags |= TF_DELACK; tp->t_timer[TCPT_DELACK] = OFFSET_FROM_START(tp, tcp_delack); } } else { tp->t_flags |= TF_ACKNOW; } tp->rcv_nxt += tlen; thflags = th->th_flags & TH_FIN; TCP_INC_VAR(tcpstat.tcps_rcvpack, nlropkts); tcpstat.tcps_rcvbyte += tlen; if (nstat_collect) { if (m->m_pkthdr.aux_flags & MAUXF_SW_LRO_PKT) { locked_add_64(&inp->inp_stat->rxpackets, m->m_pkthdr.lro_npkts); } else { locked_add_64(&inp->inp_stat->rxpackets, 1); } locked_add_64(&inp->inp_stat->rxbytes, tlen); } ND6_HINT(tp); tcp_sbrcv_grow(tp, &so->so_rcv, &to, tlen); so_recv_data_stat(so, m, drop_hdrlen); if (sbappendstream(&so->so_rcv, m)) sorwakeup(so); } else { thflags = tcp_reass(tp, th, &tlen, m); tp->t_flags |= TF_ACKNOW; } if (tlen > 0 && tp->sack_enable) tcp_update_sack_list(tp, save_start, save_end); if (tp->t_flags & TF_DELACK) { #if INET6 if (isipv6) { KERNEL_DEBUG(DBG_LAYER_END, ((th->th_dport << 16) | th->th_sport), (((ip6->ip6_src.s6_addr16[0]) << 16) | (ip6->ip6_dst.s6_addr16[0])), th->th_seq, th->th_ack, th->th_win); } else #endif { KERNEL_DEBUG(DBG_LAYER_END, ((th->th_dport << 16) | th->th_sport), (((ip->ip_src.s_addr & 0xffff) << 16) | (ip->ip_dst.s_addr & 0xffff)), th->th_seq, th->th_ack, th->th_win); } } } else { m_freem(m); thflags &= ~TH_FIN; } /* * If FIN is received ACK the FIN and let the user know * that the connection is closing. */ if (thflags & TH_FIN) { if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { socantrcvmore(so); postevent(so, 0, EV_FIN); /* * If connection is half-synchronized * (ie NEEDSYN flag on) then delay ACK, * so it may be piggybacked when SYN is sent. * Otherwise, since we received a FIN then no * more input can be expected, send ACK now. */ TCP_INC_VAR(tp->t_unacksegs, nlropkts); if (DELAY_ACK(tp, th) && (tp->t_flags & TF_NEEDSYN)) { if ((tp->t_flags & TF_DELACK) == 0) { tp->t_flags |= TF_DELACK; tp->t_timer[TCPT_DELACK] = OFFSET_FROM_START(tp, tcp_delack); } } else { tp->t_flags |= TF_ACKNOW; } tp->rcv_nxt++; } switch (tp->t_state) { /* * In SYN_RECEIVED and ESTABLISHED STATES * enter the CLOSE_WAIT state. */ case TCPS_SYN_RECEIVED: tp->t_starttime = tcp_now; case TCPS_ESTABLISHED: DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_CLOSE_WAIT); tp->t_state = TCPS_CLOSE_WAIT; break; /* * If still in FIN_WAIT_1 STATE FIN has not been acked so * enter the CLOSING state. */ case TCPS_FIN_WAIT_1: DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_CLOSING); tp->t_state = TCPS_CLOSING; break; /* * In FIN_WAIT_2 state enter the TIME_WAIT state, * starting the time-wait timer, turning off the other * standard timers. */ case TCPS_FIN_WAIT_2: DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_TIME_WAIT); tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); /* Shorten TIME_WAIT [RFC-1644, p.28] */ if (tp->cc_recv != 0 && ((int)(tcp_now - tp->t_starttime)) < tcp_msl) { add_to_time_wait(tp, tp->t_rxtcur * TCPTV_TWTRUNC); /* For transaction client, force ACK now. */ tp->t_flags |= TF_ACKNOW; tp->t_unacksegs = 0; } else add_to_time_wait(tp, 2 * tcp_msl); soisdisconnected(so); break; /* * In TIME_WAIT state restart the 2 MSL time_wait timer. */ case TCPS_TIME_WAIT: add_to_time_wait(tp, 2 * tcp_msl); break; } } #if TCPDEBUG if (so->so_options & SO_DEBUG) tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, &tcp_savetcp, 0); #endif /* * Return any desired output. */ if (needoutput || (tp->t_flags & TF_ACKNOW)) { (void) tcp_output(tp); } tcp_check_timer_state(tp); tcp_unlock(so, 1, 0); KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0); return; dropafterack: /* * Generate an ACK dropping incoming segment if it occupies * sequence space, where the ACK reflects our state. * * We can now skip the test for the RST flag since all * paths to this code happen after packets containing * RST have been dropped. * * In the SYN-RECEIVED state, don't send an ACK unless the * segment we received passes the SYN-RECEIVED ACK test. * If it fails send a RST. This breaks the loop in the * "LAND" DoS attack, and also prevents an ACK storm * between two listening ports that have been sent forged * SYN segments, each with the source address of the other. */ if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && (SEQ_GT(tp->snd_una, th->th_ack) || SEQ_GT(th->th_ack, tp->snd_max)) ) { rstreason = BANDLIM_RST_OPENPORT; if (ifp != NULL && ifp->if_tcp_stat != NULL) atomic_add_64(&ifp->if_tcp_stat->dospacket, 1); goto dropwithreset; } #if TCPDEBUG if (so->so_options & SO_DEBUG) tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, &tcp_savetcp, 0); #endif m_freem(m); tp->t_flags |= TF_ACKNOW; (void) tcp_output(tp); /* Don't need to check timer state as we should have done it during tcp_output */ tcp_unlock(so, 1, 0); KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0); return; dropwithresetnosock: nosock = 1; dropwithreset: /* * Generate a RST, dropping incoming segment. * Make ACK acceptable to originator of segment. * Don't bother to respond if destination was broadcast/multicast. */ if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) goto drop; #if INET6 if (isipv6) { if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) goto drop; } else #endif /* INET6 */ if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) goto drop; /* IPv6 anycast check is done at tcp6_input() */ /* * Perform bandwidth limiting. */ #if ICMP_BANDLIM if (badport_bandlim(rstreason) < 0) goto drop; #endif #if TCPDEBUG if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, &tcp_savetcp, 0); #endif if (thflags & TH_ACK) /* mtod() below is safe as long as hdr dropping is delayed */ tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, TH_RST, ifscope, nocell); else { if (thflags & TH_SYN) tlen++; /* mtod() below is safe as long as hdr dropping is delayed */ tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, (tcp_seq)0, TH_RST|TH_ACK, ifscope, nocell); } /* destroy temporarily created socket */ if (dropsocket) { (void) soabort(so); tcp_unlock(so, 1, 0); } else if ((inp != NULL) && (nosock == 0)) { tcp_unlock(so, 1, 0); } KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0); return; dropnosock: nosock = 1; drop: /* * Drop space held by incoming segment and return. */ #if TCPDEBUG if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, &tcp_savetcp, 0); #endif m_freem(m); /* destroy temporarily created socket */ if (dropsocket) { (void) soabort(so); tcp_unlock(so, 1, 0); } else if (nosock == 0) { tcp_unlock(so, 1, 0); } KERNEL_DEBUG(DBG_FNC_TCP_INPUT | DBG_FUNC_END,0,0,0,0,0); return; } static void tcp_dooptions(tp, cp, cnt, th, to, input_ifscope) /* * Parse TCP options and place in tcpopt. */ struct tcpcb *tp; u_char *cp; int cnt; struct tcphdr *th; struct tcpopt *to; unsigned int input_ifscope; { u_short mss = 0; int opt, optlen; for (; cnt > 0; cnt -= optlen, cp += optlen) { opt = cp[0]; if (opt == TCPOPT_EOL) break; if (opt == TCPOPT_NOP) optlen = 1; else { if (cnt < 2) break; optlen = cp[1]; if (optlen < 2 || optlen > cnt) break; } switch (opt) { default: continue; case TCPOPT_MAXSEG: if (optlen != TCPOLEN_MAXSEG) continue; if (!(th->th_flags & TH_SYN)) continue; bcopy((char *) cp + 2, (char *) &mss, sizeof(mss)); #if BYTE_ORDER != BIG_ENDIAN NTOHS(mss); #endif break; case TCPOPT_WINDOW: if (optlen != TCPOLEN_WINDOW) continue; if (!(th->th_flags & TH_SYN)) continue; tp->t_flags |= TF_RCVD_SCALE; tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); break; case TCPOPT_TIMESTAMP: if (optlen != TCPOLEN_TIMESTAMP) continue; to->to_flags |= TOF_TS; bcopy((char *)cp + 2, (char *)&to->to_tsval, sizeof(to->to_tsval)); #if BYTE_ORDER != BIG_ENDIAN NTOHL(to->to_tsval); #endif bcopy((char *)cp + 6, (char *)&to->to_tsecr, sizeof(to->to_tsecr)); #if BYTE_ORDER != BIG_ENDIAN NTOHL(to->to_tsecr); #endif /* * A timestamp received in a SYN makes * it ok to send timestamp requests and replies. */ if (th->th_flags & TH_SYN) { tp->t_flags |= TF_RCVD_TSTMP; tp->ts_recent = to->to_tsval; tp->ts_recent_age = tcp_now; } break; case TCPOPT_SACK_PERMITTED: if (!tcp_do_sack || optlen != TCPOLEN_SACK_PERMITTED) continue; if (th->th_flags & TH_SYN) to->to_flags |= TOF_SACK; break; case TCPOPT_SACK: if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) continue; to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; to->to_sacks = cp + 2; tcpstat.tcps_sack_rcv_blocks++; break; } } if (th->th_flags & TH_SYN) tcp_mss(tp, mss, input_ifscope); /* sets t_maxseg */ } /* * Pull out of band byte out of a segment so * it doesn't appear in the user's data queue. * It is still reflected in the segment length for * sequencing purposes. */ static void tcp_pulloutofband(so, th, m, off) struct socket *so; struct tcphdr *th; register struct mbuf *m; int off; /* delayed to be droped hdrlen */ { int cnt = off + th->th_urp - 1; while (cnt >= 0) { if (m->m_len > cnt) { char *cp = mtod(m, caddr_t) + cnt; struct tcpcb *tp = sototcpcb(so); tp->t_iobc = *cp; tp->t_oobflags |= TCPOOB_HAVEDATA; bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); m->m_len--; if (m->m_flags & M_PKTHDR) m->m_pkthdr.len--; return; } cnt -= m->m_len; m = m->m_next; if (m == 0) break; } panic("tcp_pulloutofband"); } uint32_t get_base_rtt(struct tcpcb *tp) { uint32_t base_rtt = 0, i; for (i = 0; i < N_RTT_BASE; ++i) { if (tp->rtt_hist[i] != 0 && (base_rtt == 0 || tp->rtt_hist[i] < base_rtt)) base_rtt = tp->rtt_hist[i]; } return base_rtt; } /* Each value of RTT base represents the minimum RTT seen in a minute. * We keep upto N_RTT_BASE minutes worth of history. */ void update_base_rtt(struct tcpcb *tp, uint32_t rtt) { if (++tp->rtt_count >= rtt_samples_per_slot) { int i=0; for (i = (N_RTT_BASE-1); i > 0; --i) { tp->rtt_hist[i] = tp->rtt_hist[i-1]; } tp->rtt_hist[0] = rtt; tp->rtt_count = 0; } else { tp->rtt_hist[0] = min(tp->rtt_hist[0], rtt); } } /* * Collect new round-trip time estimate * and update averages and current timeout. */ static void tcp_xmit_timer(tp, rtt) register struct tcpcb *tp; int rtt; { register int delta; tcpstat.tcps_rttupdated++; tp->t_rttupdated++; if (rtt > 0) { tp->t_rttcur = rtt; update_base_rtt(tp, rtt); } if (tp->t_srtt != 0) { /* * srtt is stored as fixed point with 5 bits after the * binary point (i.e., scaled by 32). The following magic * is equivalent to the smoothing algorithm in rfc793 with * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed * point). * * Freebsd adjusts rtt to origin 0 by subtracting 1 from the provided * rtt value. This was required because of the way t_rtttime was * initiailised to 1 before. Since we changed t_rtttime to be based on * tcp_now, this extra adjustment is not needed. */ delta = (rtt << TCP_DELTA_SHIFT) - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); if ((tp->t_srtt += delta) <= 0) tp->t_srtt = 1; /* * We accumulate a smoothed rtt variance (actually, a * smoothed mean difference), then set the retransmit * timer to smoothed rtt + 4 times the smoothed variance. * rttvar is stored as fixed point with 4 bits after the * binary point (scaled by 16). The following is * equivalent to rfc793 smoothing with an alpha of .75 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces * rfc793's wired-in beta. */ if (delta < 0) delta = -delta; delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); if ((tp->t_rttvar += delta) <= 0) tp->t_rttvar = 1; if (tp->t_rttbest == 0 || tp->t_rttbest > (tp->t_srtt + tp->t_rttvar)) tp->t_rttbest = tp->t_srtt + tp->t_rttvar; } else { /* * No rtt measurement yet - use the unsmoothed rtt. * Set the variance to half the rtt (so our first * retransmit happens at 3*rtt). */ tp->t_srtt = rtt << TCP_RTT_SHIFT; tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); } nstat_route_rtt(tp->t_inpcb->inp_route.ro_rt, tp->t_srtt, tp->t_rttvar); tp->t_rtttime = 0; tp->t_rxtshift = 0; tp->rxt_start = 0; /* * the retransmit should happen at rtt + 4 * rttvar. * Because of the way we do the smoothing, srtt and rttvar * will each average +1/2 tick of bias. When we compute * the retransmit timer, we want 1/2 tick of rounding and * 1 extra tick because of +-1/2 tick uncertainty in the * firing of the timer. The bias will give us exactly the * 1.5 tick we need. But, because the bias is * statistical, we have to test that we don't drop below * the minimum feasible timer (which is 2 ticks). */ TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX, TCP_ADD_REXMTSLOP(tp)); /* * We received an ack for a packet that wasn't retransmitted; * it is probably safe to discard any error indications we've * received recently. This isn't quite right, but close enough * for now (a route might have failed after we sent a segment, * and the return path might not be symmetrical). */ tp->t_softerror = 0; } static inline unsigned int tcp_maxmtu(struct rtentry *rt) { unsigned int maxmtu; RT_LOCK_ASSERT_HELD(rt); if (rt->rt_rmx.rmx_mtu == 0) maxmtu = rt->rt_ifp->if_mtu; else maxmtu = MIN(rt->rt_rmx.rmx_mtu, rt->rt_ifp->if_mtu); return (maxmtu); } #if INET6 static inline unsigned int tcp_maxmtu6(struct rtentry *rt) { unsigned int maxmtu; struct nd_ifinfo *ndi; RT_LOCK_ASSERT_HELD(rt); lck_rw_lock_shared(nd_if_rwlock); if ((ndi = ND_IFINFO(rt->rt_ifp)) != NULL && !ndi->initialized) ndi = NULL; if (ndi != NULL) lck_mtx_lock(&ndi->lock); if (rt->rt_rmx.rmx_mtu == 0) maxmtu = IN6_LINKMTU(rt->rt_ifp); else maxmtu = MIN(rt->rt_rmx.rmx_mtu, IN6_LINKMTU(rt->rt_ifp)); if (ndi != NULL) lck_mtx_unlock(&ndi->lock); lck_rw_done(nd_if_rwlock); return (maxmtu); } #endif /* * Determine a reasonable value for maxseg size. * If the route is known, check route for mtu. * If none, use an mss that can be handled on the outgoing * interface without forcing IP to fragment; if bigger than * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES * to utilize large mbufs. If no route is found, route has no mtu, * or the destination isn't local, use a default, hopefully conservative * size (usually 512 or the default IP max size, but no more than the mtu * of the interface), as we can't discover anything about intervening * gateways or networks. We also initialize the congestion/slow start * window to be a single segment if the destination isn't local. * While looking at the routing entry, we also initialize other path-dependent * parameters from pre-set or cached values in the routing entry. * * Also take into account the space needed for options that we * send regularly. Make maxseg shorter by that amount to assure * that we can send maxseg amount of data even when the options * are present. Store the upper limit of the length of options plus * data in maxopd. * * NOTE that this routine is only called when we process an incoming * segment, for outgoing segments only tcp_mssopt is called. * */ void tcp_mss(tp, offer, input_ifscope) struct tcpcb *tp; int offer; unsigned int input_ifscope; { register struct rtentry *rt; struct ifnet *ifp; register int rtt, mss; u_int32_t bufsize; struct inpcb *inp; struct socket *so; struct rmxp_tao *taop; int origoffer = offer; u_int32_t sb_max_corrected; int isnetlocal = 0; #if INET6 int isipv6; int min_protoh; #endif inp = tp->t_inpcb; #if INET6 isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; min_protoh = isipv6 ? sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : sizeof (struct tcpiphdr); #else #define min_protoh (sizeof (struct tcpiphdr)) #endif #if INET6 if (isipv6) { rt = tcp_rtlookup6(inp, input_ifscope); if (rt != NULL && (IN6_IS_ADDR_LOOPBACK(&inp->in6p_faddr) || IN6_IS_ADDR_LINKLOCAL(&inp->in6p_faddr) || rt->rt_gateway->sa_family == AF_LINK || in6_localaddr(&inp->in6p_faddr))) { tp->t_flags |= TF_LOCAL; } } else #endif /* INET6 */ { rt = tcp_rtlookup(inp, input_ifscope); if (rt != NULL && (rt->rt_gateway->sa_family == AF_LINK || rt->rt_ifp->if_flags & IFF_LOOPBACK || in_localaddr(inp->inp_faddr))) { tp->t_flags |= TF_LOCAL; } } isnetlocal = (tp->t_flags & TF_LOCAL); if (rt == NULL) { tp->t_maxopd = tp->t_maxseg = #if INET6 isipv6 ? tcp_v6mssdflt : #endif /* INET6 */ tcp_mssdflt; return; } ifp = rt->rt_ifp; /* * Slower link window correction: * If a value is specificied for slowlink_wsize use it for PPP links * believed to be on a serial modem (speed <128Kbps). Excludes 9600bps as * it is the default value adversized by pseudo-devices over ppp. */ if (ifp->if_type == IFT_PPP && slowlink_wsize > 0 && ifp->if_baudrate > 9600 && ifp->if_baudrate <= 128000) { tp->t_flags |= TF_SLOWLINK; } so = inp->inp_socket; taop = rmx_taop(rt->rt_rmx); /* * Offer == -1 means that we didn't receive SYN yet, * use cached value in that case; */ if (offer == -1) offer = taop->tao_mssopt; /* * Offer == 0 means that there was no MSS on the SYN segment, * in this case we use tcp_mssdflt. */ if (offer == 0) offer = #if INET6 isipv6 ? tcp_v6mssdflt : #endif /* INET6 */ tcp_mssdflt; else { /* * Prevent DoS attack with too small MSS. Round up * to at least minmss. */ offer = max(offer, tcp_minmss); /* * Sanity check: make sure that maxopd will be large * enough to allow some data on segments even is the * all the option space is used (40bytes). Otherwise * funny things may happen in tcp_output. */ offer = max(offer, 64); } taop->tao_mssopt = offer; /* * While we're here, check if there's an initial rtt * or rttvar. Convert from the route-table units * to scaled multiples of the slow timeout timer. */ if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt) != 0) { tcp_getrt_rtt(tp, rt); } else { tp->t_rttmin = isnetlocal ? tcp_TCPTV_MIN : TCPTV_REXMTMIN; } #if INET6 mss = (isipv6 ? tcp_maxmtu6(rt) : tcp_maxmtu(rt)); #else mss = tcp_maxmtu(rt); #endif mss -= min_protoh; if (rt->rt_rmx.rmx_mtu == 0) { #if INET6 if (isipv6) { if (!isnetlocal) mss = min(mss, tcp_v6mssdflt); } else #endif /* INET6 */ if (!isnetlocal) mss = min(mss, tcp_mssdflt); } mss = min(mss, offer); /* * maxopd stores the maximum length of data AND options * in a segment; maxseg is the amount of data in a normal * segment. We need to store this value (maxopd) apart * from maxseg, because now every segment carries options * and thus we normally have somewhat less data in segments. */ tp->t_maxopd = mss; /* * origoffer==-1 indicates, that no segments were received yet. * In this case we just guess. */ if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && (origoffer == -1 || (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) mss -= TCPOLEN_TSTAMP_APPA; tp->t_maxseg = mss; /* * Calculate corrected value for sb_max; ensure to upgrade the * numerator for large sb_max values else it will overflow. */ sb_max_corrected = (sb_max * (u_int64_t)MCLBYTES) / (MSIZE + MCLBYTES); /* * If there's a pipesize (ie loopback), change the socket * buffer to that size only if it's bigger than the current * sockbuf size. Make the socket buffers an integral * number of mss units; if the mss is larger than * the socket buffer, decrease the mss. */ #if RTV_SPIPE bufsize = rt->rt_rmx.rmx_sendpipe; if (bufsize < so->so_snd.sb_hiwat) #endif bufsize = so->so_snd.sb_hiwat; if (bufsize < mss) mss = bufsize; else { bufsize = (((bufsize + (u_int64_t)mss - 1) / (u_int64_t)mss) * (u_int64_t)mss); if (bufsize > sb_max_corrected) bufsize = sb_max_corrected; (void)sbreserve(&so->so_snd, bufsize); } tp->t_maxseg = mss; #if RTV_RPIPE bufsize = rt->rt_rmx.rmx_recvpipe; if (bufsize < so->so_rcv.sb_hiwat) #endif bufsize = so->so_rcv.sb_hiwat; if (bufsize > mss) { bufsize = (((bufsize + (u_int64_t)mss - 1) / (u_int64_t)mss) * (u_int64_t)mss); if (bufsize > sb_max_corrected) bufsize = sb_max_corrected; (void)sbreserve(&so->so_rcv, bufsize); } set_tcp_stream_priority(so); if (rt->rt_rmx.rmx_ssthresh) { /* * There's some sort of gateway or interface * buffer limit on the path. Use this to set * the slow start threshhold, but set the * threshold to no less than 2*mss. */ tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); tcpstat.tcps_usedssthresh++; } else { tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT; } /* * Set the slow-start flight size depending on whether this * is a local network or not. */ if (CC_ALGO(tp)->cwnd_init != NULL) CC_ALGO(tp)->cwnd_init(tp); DTRACE_TCP5(cc, void, NULL, struct inpcb *, tp->t_inpcb, struct tcpcb *, tp, struct tcphdr *, NULL, int32_t, TCP_CC_CWND_INIT); /* Route locked during lookup above */ RT_UNLOCK(rt); } /* * Determine the MSS option to send on an outgoing SYN. */ int tcp_mssopt(tp) struct tcpcb *tp; { struct rtentry *rt; int mss; #if INET6 int isipv6; int min_protoh; #endif #if INET6 isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0; min_protoh = isipv6 ? sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : sizeof (struct tcpiphdr); #else #define min_protoh (sizeof (struct tcpiphdr)) #endif #if INET6 if (isipv6) rt = tcp_rtlookup6(tp->t_inpcb, IFSCOPE_NONE); else #endif /* INET6 */ rt = tcp_rtlookup(tp->t_inpcb, IFSCOPE_NONE); if (rt == NULL) { return ( #if INET6 isipv6 ? tcp_v6mssdflt : #endif /* INET6 */ tcp_mssdflt); } /* * Slower link window correction: * If a value is specificied for slowlink_wsize use it for PPP links * believed to be on a serial modem (speed <128Kbps). Excludes 9600bps as * it is the default value adversized by pseudo-devices over ppp. */ if (rt->rt_ifp->if_type == IFT_PPP && slowlink_wsize > 0 && rt->rt_ifp->if_baudrate > 9600 && rt->rt_ifp->if_baudrate <= 128000) { tp->t_flags |= TF_SLOWLINK; } #if INET6 mss = (isipv6 ? tcp_maxmtu6(rt) : tcp_maxmtu(rt)); #else mss = tcp_maxmtu(rt); #endif /* Route locked during lookup above */ RT_UNLOCK(rt); return (mss - min_protoh); } /* * On a partial ack arrives, force the retransmission of the * next unacknowledged segment. Do not clear tp->t_dupacks. * By setting snd_nxt to th_ack, this forces retransmission timer to * be started again. */ static void tcp_newreno_partial_ack(tp, th) struct tcpcb *tp; struct tcphdr *th; { tcp_seq onxt = tp->snd_nxt; u_int32_t ocwnd = tp->snd_cwnd; tp->t_timer[TCPT_REXMT] = 0; tp->t_rtttime = 0; tp->snd_nxt = th->th_ack; /* * Set snd_cwnd to one segment beyond acknowledged offset * (tp->snd_una has not yet been updated when this function * is called) */ tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); tp->t_flags |= TF_ACKNOW; (void) tcp_output(tp); tp->snd_cwnd = ocwnd; if (SEQ_GT(onxt, tp->snd_nxt)) tp->snd_nxt = onxt; /* * Partial window deflation. Relies on fact that tp->snd_una * not updated yet. */ if (tp->snd_cwnd > th->th_ack - tp->snd_una) tp->snd_cwnd -= th->th_ack - tp->snd_una; else tp->snd_cwnd = 0; tp->snd_cwnd += tp->t_maxseg; } /* * Drop a random TCP connection that hasn't been serviced yet and * is eligible for discard. There is a one in qlen chance that * we will return a null, saying that there are no dropable * requests. In this case, the protocol specific code should drop * the new request. This insures fairness. * * The listening TCP socket "head" must be locked */ static int tcp_dropdropablreq(struct socket *head) { struct socket *so, *sonext; unsigned int i, j, qlen; static int rnd; static struct timeval old_runtime; static unsigned int cur_cnt, old_cnt; struct timeval tv; struct inpcb *inp = NULL; struct tcpcb *tp; if ((head->so_options & SO_ACCEPTCONN) == 0) return 0; so = TAILQ_FIRST(&head->so_incomp); if (!so) return 0; microtime(&tv); if ((i = (tv.tv_sec - old_runtime.tv_sec)) != 0) { old_runtime = tv; old_cnt = cur_cnt / i; cur_cnt = 0; } qlen = head->so_incqlen; if (++cur_cnt > qlen || old_cnt > qlen) { rnd = (314159 * rnd + 66329) & 0xffff; j = ((qlen + 1) * rnd) >> 16; while (j-- && so) so = TAILQ_NEXT(so, so_list); } /* Find a connection that is not already closing (or being served) */ while (so) { inp = (struct inpcb *)so->so_pcb; sonext = TAILQ_NEXT(so, so_list); if (in_pcb_checkstate(inp, WNT_ACQUIRE, 0) != WNT_STOPUSING) { /* Avoid the issue of a socket being accepted by one input thread * and being dropped by another input thread. * If we can't get a hold on this mutex, then grab the next socket in line. */ if (lck_mtx_try_lock(&inp->inpcb_mtx)) { so->so_usecount++; if ((so->so_usecount == 2) && (so->so_state & SS_INCOMP) != 0 && (so->so_flags & SOF_INCOMP_INPROGRESS) == 0) break; else {/* don't use if being accepted or used in any other way */ in_pcb_checkstate(inp, WNT_RELEASE, 1); tcp_unlock(so, 1, 0); } } else { /* do not try to lock the inp in in_pcb_checkstate * because the lock is already held in some other thread. * Only drop the inp_wntcnt reference. */ in_pcb_checkstate(inp, WNT_RELEASE, 1); } } so = sonext; } if (!so) return 0; /* Makes sure socket is still in the right state to be discarded */ if (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING) { tcp_unlock(so, 1, 0); return 0; } if (so->so_usecount != 2 || !(so->so_state & SS_INCOMP)) { /* do not discard: that socket is being accepted */ tcp_unlock(so, 1, 0); return 0; } TAILQ_REMOVE(&head->so_incomp, so, so_list); tcp_unlock(head, 0, 0); lck_mtx_assert(&inp->inpcb_mtx, LCK_MTX_ASSERT_OWNED); tp = sototcpcb(so); so->so_flags |= SOF_OVERFLOW; so->so_head = NULL; tcp_close(tp); tp->t_unacksegs = 0; if (inp->inp_wantcnt > 0 && inp->inp_wantcnt != WNT_STOPUSING) { /* Some one has a wantcnt on this pcb. Since WNT_ACQUIRE * doesn't require a lock, it could have happened while * we are holding the lock. This pcb will have to * be garbage collected later. * Release the reference held for so_incomp queue */ so->so_usecount--; tcp_unlock(so, 1, 0); } else { /* Unlock this socket and leave the reference on. We need to * acquire the pcbinfo lock in order to fully dispose it off */ tcp_unlock(so, 0, 0); lck_rw_lock_exclusive(tcbinfo.mtx); tcp_lock(so, 0, 0); /* Release the reference held for so_incomp queue */ so->so_usecount--; if (so->so_usecount != 1 || (inp->inp_wantcnt > 0 && inp->inp_wantcnt != WNT_STOPUSING)) { /* There is an extra wantcount or usecount that must * have been added when the socket was unlocked. This * socket will have to be garbage collected later */ tcp_unlock(so, 1, 0); } else { /* Drop the reference held for this function */ so->so_usecount--; in_pcbdispose(inp); } lck_rw_done(tcbinfo.mtx); } tcpstat.tcps_drops++; tcp_lock(head, 0, 0); head->so_incqlen--; head->so_qlen--; return(1); } /* Set background congestion control on a socket */ void tcp_set_background_cc(struct socket *so) { tcp_set_new_cc(so, TCP_CC_ALGO_BACKGROUND_INDEX); } /* Set foreground congestion control on a socket */ void tcp_set_foreground_cc(struct socket *so) { tcp_set_new_cc(so, TCP_CC_ALGO_NEWRENO_INDEX); } static void tcp_set_new_cc(struct socket *so, uint16_t cc_index) { struct inpcb *inp = sotoinpcb(so); struct tcpcb *tp = intotcpcb(inp); uint16_t old_cc_index = 0; if (tp->tcp_cc_index != cc_index) { old_cc_index = tp->tcp_cc_index; if (CC_ALGO(tp)->cleanup != NULL) CC_ALGO(tp)->cleanup(tp); tp->tcp_cc_index = cc_index; /* Decide if the connection is just starting or if * we have sent some packets on it. */ if (tp->snd_nxt > tp->iss) { /* Already sent some packets */ if (CC_ALGO(tp)->switch_to != NULL) CC_ALGO(tp)->switch_to(tp, old_cc_index); } else { if (CC_ALGO(tp)->init != NULL) CC_ALGO(tp)->init(tp); } DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, struct tcphdr *, NULL, int32_t, TCP_CC_CHANGE_ALGO); } } void tcp_set_recv_bg(struct socket *so) { if (!IS_TCP_RECV_BG(so)) so->so_traffic_mgt_flags |= TRAFFIC_MGT_TCP_RECVBG; } void tcp_clear_recv_bg(struct socket *so) { if (IS_TCP_RECV_BG(so)) so->so_traffic_mgt_flags &= ~(TRAFFIC_MGT_TCP_RECVBG); } void inp_fc_unthrottle_tcp(struct inpcb *inp) { struct tcpcb *tp = inp->inp_ppcb; /* * Back off the slow-start threshold and enter * congestion avoidance phase */ if (CC_ALGO(tp)->pre_fr != NULL) CC_ALGO(tp)->pre_fr(tp); tp->snd_cwnd = tp->snd_ssthresh; /* * Restart counting for ABC as we changed the * congestion window just now. */ tp->t_bytes_acked = 0; /* Reset retransmit shift as we know that the reason * for delay in sending a packet is due to flow * control on the outgoing interface. There is no need * to backoff retransmit timer. */ tp->t_rxtshift = 0; /* * Start the output stream again. Since we are * not retransmitting data, do not reset the * retransmit timer or rtt calculation. */ tcp_output(tp); } static int tcp_getstat SYSCTL_HANDLER_ARGS { #pragma unused(oidp, arg1, arg2) int error; if (req->oldptr == 0) { req->oldlen= (size_t)sizeof(struct tcpstat); } error = SYSCTL_OUT(req, &tcpstat, MIN(sizeof (tcpstat), req->oldlen)); return (error); } SYSCTL_PROC(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RD | CTLFLAG_LOCKED, 0, 0, tcp_getstat, "S,tcpstat", "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); static int sysctl_rexmtthresh SYSCTL_HANDLER_ARGS { #pragma unused(arg1, arg2) int error, val = tcprexmtthresh; error = sysctl_handle_int(oidp, &val, 0, req); if (error || !req->newptr) return (error); /* * Constrain the number of duplicate ACKs * to consider for TCP fast retransmit * to either 2 or 3 */ if (val < 2 || val > 3) return (EINVAL); tcprexmtthresh = val; return (0); } SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmt_thresh, CTLTYPE_INT|CTLFLAG_RW | CTLFLAG_LOCKED, &tcprexmtthresh, 0, &sysctl_rexmtthresh, "I", "Duplicate ACK Threshold for Fast Retransmit");