/* * Copyright (c) 2000-2008 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 /* before tcp_seq.h, for tcp_random18() */ #include #include #include #include #include #include #include /* for ICMP_BANDLIM */ #include #include /* for ICMP_BANDLIM */ #include #include #if INET6 #include #include #include #include #include #endif #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 #ifndef __APPLE__ MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); #endif #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 struct tcpstat tcpstat; static int log_in_vain = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, &log_in_vain, 0, "Log all incoming TCP connections"); static int blackhole = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, &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, &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, &tcp_lq_overflow, 0, "Listen Queue Overflow"); #if TCP_DROP_SYNFIN static int drop_synfin = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, &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, &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, &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, &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, &slowlink_wsize, 0, "Maximum advertised window size for slowlink"); static int maxseg_unacked = 8; SYSCTL_INT(_net_inet_tcp, OID_AUTO, maxseg_unacked, CTLFLAG_RW, &maxseg_unacked, 0, "Maximum number of outstanding segments left unacked"); static int tcp_do_rfc3465 = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW, &tcp_do_rfc3465, 0, ""); extern int tcp_TCPTV_MIN; u_long 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 *); #if INET6 static inline unsigned int tcp_maxmtu6(struct rtentry *); #endif /* 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 u_long *delack_bitmask; extern void add_to_time_wait(struct tcpcb *); 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; __private_extern__ int tcp_sockthreshold; __private_extern__ int tcp_win_scale; #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 /* * Indicate whether this ack should be delayed. * We can delay the ack if: * - delayed acks are enabled (set to 1) and * - our last ack wasn't a 0-sized window. We never want to delay * the ack that opens up a 0-sized window. * - delayed acks are enabled (set to 2, "more compatible") and * - our last ack wasn't a 0-sized window. * - if the peer hasn't sent us a TH_PUSH data packet (this solves 3649245) * - the peer hasn't sent us a TH_PUSH data packet, if he did, take this as a clue that we * need to ACK with no delay. This helps higher level protocols who won't send * us more data even if the window is open because their last "segment" hasn't been ACKed * - delayed acks are enabled (set to 3, "streaming detection") and * - if we receive more than "maxseg_unacked" full packets per second on this socket * - if we don't have more than "maxseg_unacked" delayed so far * - if those criteria aren't met, acts like "2". Allowing faster acking while browsing for example. * */ #define DELAY_ACK(tp) \ (((tcp_delack_enabled == 1) && ((tp->t_flags & TF_RXWIN0SENT) == 0)) || \ (((tcp_delack_enabled == 2) && (tp->t_flags & TF_RXWIN0SENT) == 0) && \ ((thflags & TH_PUSH) == 0) && ((tp->t_flags & TF_DELACK) == 0)) || \ (((tcp_delack_enabled == 3) && (tp->t_flags & TF_RXWIN0SENT) == 0) && \ (tp->t_rcvtime == 0) && ((thflags & TH_PUSH) == 0) && \ (((tp->t_unacksegs == 0)) || \ ((tp->rcv_byps > (maxseg_unacked * tp->t_maxseg)) && (tp->t_unacksegs < maxseg_unacked))))) static int tcp_dropdropablreq(struct socket *head); static void tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th); 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; /* * 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 */ MALLOC(te, struct tseg_qent *, sizeof (struct tseg_qent), M_TSEGQ, M_NOWAIT); 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; m_freem(m); FREE(te, M_TSEGQ); 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; /* * 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); FREE(q, M_TSEGQ); 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) 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 { if (sbappendstream(&so->so_rcv, q->tqe_m)) dowakeup = 1; } FREE(q, M_TSEGQ); 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) { u_int win; win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; if (win < 2) win = 2; tp->snd_ssthresh = win * tp->t_maxseg; 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(mp, offp) struct mbuf **mp; int *offp; { register struct mbuf *m = *mp; struct in6_ifaddr *ia6; IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), return IPPROTO_DONE); /* * draft-itojun-ipv6-tcp-to-anycast * better place to put this in? */ ia6 = ip6_getdstifaddr(m); if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { struct ip6_hdr *ip6; ip6 = mtod(m, struct ip6_hdr *); icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); return IPPROTO_DONE; } tcp_input(m, *offp); return IPPROTO_DONE; } #endif 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; int nosock = 0; u_long 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; /* * 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; /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ fwd_tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_IPFORWARD, 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)); tcpstat.tcps_rcvtotal++; #if INET6 if (isipv6) { /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ ip6 = mtod(m, struct ip6_hdr *); tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { tcpstat.tcps_rcvbadsum++; goto dropnosock; } th = (struct tcphdr *)((caddr_t)ip6 + off0); 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 */ goto dropnosock; } } 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; } } ip = mtod(m, struct ip *); ipov = (struct ipovly *)ip; th = (struct tcphdr *)((caddr_t)ip + off0); tlen = ip->ip_len; 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); if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { if (m->m_pkthdr.csum_flags & CSUM_TCP_SUM16) { u_short pseudo; char b[9]; *(uint32_t*)&b[0] = *(uint32_t*)&ipov->ih_x1[0]; *(uint32_t*)&b[4] = *(uint32_t*)&ipov->ih_x1[4]; *(uint8_t*)&b[8] = *(uint8_t*)&ipov->ih_x1[8]; bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); ipov->ih_len = (u_short)tlen; HTONS(ipov->ih_len); pseudo = in_cksum(m, sizeof (struct ip)); *(uint32_t*)&ipov->ih_x1[0] = *(uint32_t*)&b[0]; *(uint32_t*)&ipov->ih_x1[4] = *(uint32_t*)&b[4]; *(uint8_t*)&ipov->ih_x1[8] = *(uint8_t*)&b[8]; 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. */ *(uint32_t*)&b[0] = *(uint32_t*)&ipov->ih_x1[0]; *(uint32_t*)&b[4] = *(uint32_t*)&ipov->ih_x1[4]; *(uint8_t*)&b[8] = *(uint8_t*)&ipov->ih_x1[8]; len = sizeof (struct ip) + tlen; bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); ipov->ih_len = (u_short)tlen; HTONS(ipov->ih_len); th->th_sum = in_cksum(m, len); *(uint32_t*)&ipov->ih_x1[0] = *(uint32_t*)&b[0]; *(uint32_t*)&ipov->ih_x1[4] = *(uint32_t*)&b[4]; *(uint8_t*)&ipov->ih_x1[8] = *(uint8_t*)&b[8]; tcp_in_cksum_stats(len); } if (th->th_sum) { tcpstat.tcps_rcvbadsum++; goto dropnosock; } #if INET6 /* Re-initialization for later version check */ ip->ip_v = IPVERSION; #endif ip_ecn = (ip->ip_tos & IPTOS_ECN_MASK); } /* * 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++; 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 *)((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 *)((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 *)optp == htonl(TCPOPT_TSTAMP_HDR) && (th->th_flags & TH_SYN) == 0) { to.to_flags |= TOF_TS; to.to_tsval = ntohl(*(u_int32_t *)(optp + 4)); to.to_tsecr = ntohl(*(u_int32_t *)(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)) goto dropnosock; #endif /* * Convert TCP protocol specific fields to host format. */ NTOHL(th->th_seq); NTOHL(th->th_ack); NTOHS(th->th_win); NTOHS(th->th_urp); /* * 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; /* * Locate pcb for segment. */ findpcb: #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_boundif; #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); goto dropnosock; } } else #endif /* INET6 */ if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { IPSEC_STAT_INCREMENT(ipsecstat.in_polvio); 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) && !(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; goto dropwithresetnosock; } so = inp->inp_socket; if (so == NULL) { if (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING) inp = NULL; // pretend we didn't find it #if TEMPDEBUG printf("tcp_input: no more socket for inp=%x\n", inp); #endif goto dropnosock; } #ifdef __APPLE__ /* * Bogus state when listening port owned by SharedIP with loopback as the * only configured interface: BlueBox does not filters loopback */ if (so == &tcbinfo.nat_dummy_socket) goto drop; #endif tcp_lock(so, 1, 2); if (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING) { tcp_unlock(so, 1, 2); inp = NULL; // pretend we didn't find it goto dropnosock; } tp = intotcpcb(inp); if (tp == 0) { rstreason = BANDLIM_RST_CLOSEDPORT; 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 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 */ int ogencnt = so->so_gencnt; unsigned int head_ifscope; /* Get listener's bound-to-interface, if any */ head_ifscope = (inp->inp_flags & INP_BOUND_IF) ? inp->inp_boundif : IFSCOPE_NONE; #if !IPSEC /* * Current IPsec implementation makes incorrect IPsec * cache if this check is done here. * So delay this until duplicated socket is created. */ if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { /* * Note: dropwithreset makes sure we don't * send a RST in response to a RST. */ if (thflags & TH_ACK) { tcpstat.tcps_badsyn++; rstreason = BANDLIM_RST_OPENPORT; goto dropwithreset; } goto drop; } #endif KERNEL_DEBUG(DBG_FNC_TCP_NEWCONN | DBG_FUNC_START,0,0,0,0,0); #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; if ((ia6 = ip6_getdstifaddr(m)) && (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { tp = NULL; rstreason = BANDLIM_RST_OPENPORT; goto dropwithreset; } } #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; } /* * Make sure listening socket did not get closed during socket allocation, * not only this is incorrect but it is know to cause panic */ if (so->so_gencnt != ogencnt) goto drop; oso = so; tcp_unlock(so, 0, 0); /* Unlock but keep a reference on listener for now */ so = so2; tcp_lock(so, 1, 0); /* * This is ugly, but .... * * 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. */ dropsocket++; inp = (struct inpcb *)so->so_pcb; /* * Inherit INP_BOUND_IF from listener; testing if * head_ifscope is non-zero is sufficient, since it * can only be set to a non-zero value earlier if * the listener has such a flag set. */ #if INET6 if (head_ifscope != IFSCOPE_NONE && !isipv6) { #else if (head_ifscope != IFSCOPE_NONE) { #endif /* INET6 */ inp->inp_flags |= INP_BOUND_IF; inp->inp_boundif = head_ifscope; } #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 IPSEC /* * To avoid creating incorrectly cached IPsec * association, this is need to be done here. * * Subject: (KAME-snap 748) * From: Wayne Knowles * ftp://ftp.kame.net/pub/mail-list/snap-users/748 */ if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { /* * Note: dropwithreset makes sure we don't * send a RST in response to a RST. */ tcp_lock(oso, 0, 0); /* release ref on parent */ tcp_unlock(oso, 1, 0); if (thflags & TH_ACK) { tcpstat.tcps_badsyn++; rstreason = BANDLIM_RST_OPENPORT; goto dropwithreset; } goto drop; } #endif #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 tcp_unlock(oso, 1, 0); /* now drop the reference on the listener */ tp = intotcpcb(inp); tp->t_state = TCPS_LISTEN; tp->t_flags |= tp0->t_flags & (TF_NOPUSH|TF_NOOPT|TF_NODELAY); tp->t_inpcb->inp_ip_ttl = tp0->t_inpcb->inp_ip_ttl; /* Compute proper scaling value from buffer space */ if (inp->inp_pcbinfo->ipi_count < tcp_sockthreshold) { tp->request_r_scale = max(tcp_win_scale, tp->request_r_scale); so->so_rcv.sb_hiwat = lmin(TCP_MAXWIN << tp->request_r_scale, (sb_max / (MSIZE+MCLBYTES)) * MCLBYTES); } else { while (tp->request_r_scale < TCP_MAX_WINSHIFT && TCP_MAXWIN << tp->request_r_scale < so->so_rcv.sb_hiwat) tp->request_r_scale++; } KERNEL_DEBUG(DBG_FNC_TCP_NEWCONN | DBG_FUNC_END,0,0,0,0,0); } } #if 1 lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED); #endif /* * 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. * * The packet per second count is done all the time and is also used * by "DELAY_ACK" to detect streaming situations. * */ if (tp->t_state == TCPS_ESTABLISHED && tlen > 0) { if (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. %lubyte/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; } } #if TRAFFIC_MGT if (so->so_traffic_mgt_flags & TRAFFIC_MGT_SO_BACKGROUND) { tcpstat.tcps_bg_rcvtotal++; /* Take snapshots of pkts recv; * tcpcb should have been initialized to 0 when allocated, * so if 0 then this is the first time we're doing this */ if (!tp->tot_recv_snapshot) { tp->tot_recv_snapshot = tcpstat.tcps_rcvtotal; } if (!tp->bg_recv_snapshot) { tp->bg_recv_snapshot = tcpstat.tcps_bg_rcvtotal; } } #endif /* TRAFFIC_MGT */ /* 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_SETUPSENT | TE_SETUPRECEIVED)) == (TE_SETUPSENT | TE_SETUPRECEIVED) && 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; } /* * Segment received on connection. * Reset idle time and keep-alive timer. */ tp->t_rcvtime = 0; if (TCPS_HAVEESTABLISHED(tp->t_state)) tp->t_timer[TCPT_KEEP] = 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; } } /* * 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 && ((!tcp_do_newreno && !tp->sack_enable && tp->t_dupacks < tcprexmtthresh) || ((tcp_do_newreno || tp->sack_enable) && !IN_FASTRECOVERY(tp) && 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 && 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; } /* * 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)) { /* Makes sure we already have a TS */ if (!tp->t_rttlow || tp->t_rttlow > tcp_now - to.to_tsecr) tp->t_rttlow = 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)) { if (!tp->t_rttlow || tp->t_rttlow > tcp_now - tp->t_rtttime) tp->t_rttlow = tcp_now - tp->t_rtttime; tcp_xmit_timer(tp, tp->t_rtttime); } acked = th->th_ack - tp->snd_una; tcpstat.tcps_rcvackpack++; tcpstat.tcps_rcvackbyte += acked; /* * Grow the congestion window, if the * connection is cwnd bound. */ if (tp->snd_cwnd < tp->snd_wnd) { tp->t_bytes_acked += acked; if (tp->t_bytes_acked > tp->snd_cwnd) { tp->t_bytes_acked -= tp->snd_cwnd; tp->snd_cwnd += tp->t_maxseg; } } sbdrop(&so->so_snd, acked); 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] = tp->t_rxtcur; sowwakeup(so); /* has to be done with socket lock held */ if ((so->so_snd.sb_cc) || (tp->t_flags & TF_ACKNOW)) { tp->t_unacksegs = 0; (void) tcp_output(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. */ /* 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; tcpstat.tcps_rcvpack++; tcpstat.tcps_rcvbyte += tlen; ND6_HINT(tp); /* some progress has been done */ /* * Add data to socket buffer. */ 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); } if (DELAY_ACK(tp)) { tp->t_flags |= TF_DELACK; tp->t_unacksegs++; } else { tp->t_unacksegs = 0; tp->t_flags |= TF_ACKNOW; tcp_output(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. */ #if 1 lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED); #endif { 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) { /* * 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. * Don't bother responding if the destination was a broadcast. * Otherwise 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 #if 1 lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED); #endif if (thflags & TH_RST) goto drop; if (thflags & TH_ACK) { rstreason = BANDLIM_RST_OPENPORT; goto dropwithreset; } if ((thflags & TH_SYN) == 0) goto drop; 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 (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 { #if 0 lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED); #endif 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)) { 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; tp->t_state = TCPS_SYN_RECEIVED; tp->t_timer[TCPT_KEEP] = tcp_keepinit; dropsocket = 0; /* committed to socket */ tcpstat.tcps_accepts++; if ((thflags & (TH_ECE | TH_CWR)) == (TH_ECE | TH_CWR)) { /* ECN-setup SYN */ tp->ecn_flags |= (TE_SETUPRECEIVED | TE_SENDIPECT); } #ifdef IFEF_NOWINDOWSCALE if (m->m_pkthdr.rcvif != NULL && (m->m_pkthdr.rcvif->if_eflags & IFEF_NOWINDOWSCALE) != 0) { // Timestamps are 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; 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; goto dropwithreset; } if (thflags & TH_RST) { if ((thflags & TH_ACK) != 0) { 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 += tp->rcv_wnd; tp->snd_una++; /* SYN is acked */ /* * If there's data, delay ACK; if there's also a FIN * ACKNOW will be turned on later. */ if (DELAY_ACK(tp) && tlen != 0) { tp->t_flags |= TF_DELACK; tp->t_unacksegs++; } else { tp->t_flags |= TF_ACKNOW; tp->t_unacksegs = 0; } /* * Received in SYN_SENT[*] state. * Transitions: * SYN_SENT --> ESTABLISHED * SYN_SENT* --> FIN_WAIT_1 */ tp->t_starttime = 0; if (tp->t_flags & TF_NEEDFIN) { tp->t_state = TCPS_FIN_WAIT_1; tp->t_flags &= ~TF_NEEDFIN; thflags &= ~TH_SYN; } else { tp->t_state = TCPS_ESTABLISHED; tp->t_timer[TCPT_KEEP] = TCP_KEEPIDLE(tp); } /* soisconnected may lead to socket_unlock in case of upcalls, * make sure this is done when everything is setup. */ soisconnected(so); } 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; 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: 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); 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; } #if 0 lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED); #endif /* * 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 (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; 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; tp->t_unacksegs = 0; todrop = tlen; tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += todrop; } else { tcpstat.tcps_rcvpartduppack++; tcpstat.tcps_rcvpartdupbyte += 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; 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; tp->t_unacksegs = 0; 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); 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; } /* * Make transitions: * SYN-RECEIVED -> ESTABLISHED * SYN-RECEIVED* -> FIN-WAIT-1 */ tp->t_starttime = 0; if (tp->t_flags & TF_NEEDFIN) { tp->t_state = TCPS_FIN_WAIT_1; tp->t_flags &= ~TF_NEEDFIN; } else { tp->t_state = TCPS_ESTABLISHED; tp->t_timer[TCPT_KEEP] = TCP_KEEPIDLE(tp); } /* * 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 */ /* soisconnected may lead to socket_unlock in case of upcalls, * make sure this is done when everything is setup. */ soisconnected(so); /* * 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 || ((tcp_do_newreno || tp->sack_enable) && 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; tp->t_unacksegs = 0; (void) tcp_output(tp); goto drop; } else if (tp->t_dupacks == tcprexmtthresh) { tcp_seq onxt = tp->snd_nxt; u_int win; /* * 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 (tcp_do_newreno) { if (SEQ_LEQ(th->th_ack, tp->snd_recover)) { tp->t_dupacks = 0; break; } } win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; if (win < 2) win = 2; tp->snd_ssthresh = win * tp->t_maxseg; ENTER_FASTRECOVERY(tp); tp->snd_recover = tp->snd_max; tp->t_timer[TCPT_REXMT] = 0; tp->t_rtttime = 0; 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; tp->t_unacksegs = 0; (void) tcp_output(tp); goto drop; } tp->snd_nxt = th->th_ack; tp->snd_cwnd = tp->t_maxseg; tp->t_unacksegs = 0; (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; goto drop; } } else tp->t_dupacks = 0; break; } if (!IN_FASTRECOVERY(tp)) { /* * We were not in fast recovery. Reset the duplicate ack * counter. */ tp->t_dupacks = 0; } /* * If the congestion window was inflated to account * for the other side's cached packets, retract it. */ else { if (tcp_do_newreno || tp->sack_enable) { 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); } else { if (tcp_do_newreno) { long ss = tp->snd_max - th->th_ack; /* * Complete ack. Inflate the congestion window to * ssthresh and exit fast recovery. * * Window inflation should have left us with approx. * snd_ssthresh outstanding data. But in case we * would be inclined to send a burst, better to do * it via the slow start mechanism. */ if (ss < tp->snd_ssthresh) tp->snd_cwnd = ss + tp->t_maxseg; else tp->snd_cwnd = tp->snd_ssthresh; } else { /* * Clamp the congestion window to the crossover point * and exit fast recovery. */ if (tp->snd_cwnd > tp->snd_ssthresh) tp->snd_cwnd = tp->snd_ssthresh; } EXIT_FASTRECOVERY(tp); tp->t_dupacks = 0; tp->t_bytes_acked = 0; } } else { /* * Clamp the congestion window to the crossover point * and exit fast recovery in non-newreno and non-SACK case. */ if (tp->snd_cwnd > tp->snd_ssthresh) tp->snd_cwnd = tp->snd_ssthresh; EXIT_FASTRECOVERY(tp); tp->t_dupacks = 0; tp->t_bytes_acked = 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 && 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 */ } /* * 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)) { if (!tp->t_rttlow || tp->t_rttlow > tcp_now - to.to_tsecr) tp->t_rttlow = 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)) { if (!tp->t_rttlow || tp->t_rttlow > tcp_now - tp->t_rtttime) tp->t_rttlow = tcp_now - tp->t_rtttime; tcp_xmit_timer(tp, 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] = tp->t_rxtcur; /* * If no data (only SYN) was ACK'd, * skip rest of ACK processing. */ if (acked == 0) goto step6; /* * When new data is acked, open the congestion window. */ if ((thflags & TH_ECE) != 0 && (tp->ecn_flags & TE_SETUPSENT) != 0) { /* * Reduce the congestion window if we haven't done so. */ if (!(tp->sack_enable && IN_FASTRECOVERY(tp)) && !(tcp_do_newreno && SEQ_LEQ(th->th_ack, tp->snd_recover))) { tcp_reduce_congestion_window(tp); } } else if ((!tcp_do_newreno && !tp->sack_enable) || !IN_FASTRECOVERY(tp)) { /* * RFC 3465 - Appropriate Byte Counting. * * If the window is currently less than ssthresh, * open the window by the number of bytes ACKed by * the last ACK, however clamp the window increase * to an upper limit "L". * * In congestion avoidance phase, open the window by * one segment each time "bytes_acked" grows to be * greater than or equal to the congestion window. */ register u_int cw = tp->snd_cwnd; register u_int incr = tp->t_maxseg; if (cw >= tp->snd_ssthresh) { tp->t_bytes_acked += acked; if (tp->t_bytes_acked >= cw) { /* Time to increase the window. */ tp->t_bytes_acked -= cw; } else { /* No need to increase yet. */ incr = 0; } } else { /* * If the user explicitly enables RFC3465 * use 2*SMSS for the "L" param. Otherwise * use the more conservative 1*SMSS. * * (See RFC 3465 2.3 Choosing the Limit) */ u_int abc_lim; abc_lim = (tcp_do_rfc3465 == 0) ? incr : incr * 2; incr = min(acked, abc_lim); } tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<snd_scale); } 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); tp->snd_wnd -= acked; ourfinisacked = 0; } /* detect una wraparound */ if ((tcp_do_newreno || tp->sack_enable) && !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 ((tcp_do_newreno || tp->sack_enable) && 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; /* * 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) { tp->t_timer[TCPT_2MSL] = tcp_maxidle; add_to_time_wait(tp); soisdisconnected(so); } 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) { tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); /* Shorten TIME_WAIT [RFC-1644, p.28] */ if (tp->cc_recv != 0 && tp->t_starttime < (u_long)tcp_msl) tp->t_timer[TCPT_2MSL] = tp->t_rxtcur * TCPTV_TWTRUNC; else tp->t_timer[TCPT_2MSL] = 2 * tcp_msl; add_to_time_wait(tp); soisdisconnected(so); } 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: tp->t_timer[TCPT_2MSL] = 2 * tcp_msl; add_to_time_wait(tp); 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_long)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: /* XXX */ /* * 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)) { if (DELAY_ACK(tp) && ((tp->t_flags & TF_ACKNOW) == 0)) { tp->t_flags |= TF_DELACK; tp->t_unacksegs++; } else { tp->t_unacksegs = 0; tp->t_flags |= TF_ACKNOW; } tp->rcv_nxt += tlen; thflags = th->th_flags & TH_FIN; tcpstat.tcps_rcvpack++; tcpstat.tcps_rcvbyte += tlen; ND6_HINT(tp); if (sbappendstream(&so->so_rcv, m)) sorwakeup(so); } else { thflags = tcp_reass(tp, th, &tlen, m); tp->t_flags |= TF_ACKNOW; tp->t_unacksegs = 0; } 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); } } /* * Note the amount of data that peer has sent into * our window, in order to estimate the sender's * buffer size. */ len = (u_int)(so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt)); if (len > so->so_rcv.sb_maxused) so->so_rcv.sb_maxused = len; } 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, * 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. */ if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { tp->t_flags |= TF_DELACK; tp->t_unacksegs++; } else { tp->t_flags |= TF_ACKNOW; tp->t_unacksegs = 0; } 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 = 0; case TCPS_ESTABLISHED: 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: 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: tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); /* Shorten TIME_WAIT [RFC-1644, p.28] */ if (tp->cc_recv != 0 && tp->t_starttime < (u_long)tcp_msl) { tp->t_timer[TCPT_2MSL] = tp->t_rxtcur * TCPTV_TWTRUNC; /* For transaction client, force ACK now. */ tp->t_flags |= TF_ACKNOW; tp->t_unacksegs = 0; } else tp->t_timer[TCPT_2MSL] = 2 * tcp_msl; add_to_time_wait(tp); soisdisconnected(so); break; /* * In TIME_WAIT state restart the 2 MSL time_wait timer. */ case TCPS_TIME_WAIT: tp->t_timer[TCPT_2MSL] = 2 * tcp_msl; add_to_time_wait(tp); 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)) { tp->t_unacksegs = 0; (void) tcp_output(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; 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; tp->t_unacksegs = 0; (void) tcp_output(tp); 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); 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); } /* 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)); NTOHS(mss); 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)); NTOHL(to->to_tsval); bcopy((char *)cp + 6, (char *)&to->to_tsecr, sizeof(to->to_tsecr)); NTOHL(to->to_tsecr); /* * 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"); } /* * 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 (tp->t_srtt != 0) { /* * srtt is stored as fixed point with 5 bits after the * binary point (i.e., scaled by 8). 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). Adjust rtt to origin 0. */ delta = ((rtt - 1) << 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 > 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); tp->t_rttbest = tp->t_srtt + tp->t_rttvar; } tp->t_rtttime = 0; tp->t_rxtshift = 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); /* * 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; 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; 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)); 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_long bufsize; struct inpcb *inp; struct socket *so; struct rmxp_tao *taop; int origoffer = offer; u_long 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 lck_mtx_lock(rt_mtx); #if INET6 if (isipv6) { rt = tcp_rtlookup6(inp); if (rt && (IN6_IS_ADDR_LOOPBACK(&inp->in6p_faddr) || IN6_IS_ADDR_LINKLOCAL(&inp->in6p_faddr) || rt->rt_gateway->sa_family == AF_LINK)) isnetlocal = TRUE; } else #endif /* INET6 */ { rt = tcp_rtlookup(inp, input_ifscope); if (rt && (rt->rt_gateway->sa_family == AF_LINK || rt->rt_ifp->if_flags & IFF_LOOPBACK)) isnetlocal = TRUE; } if (rt == NULL) { tp->t_maxopd = tp->t_maxseg = #if INET6 isipv6 ? tcp_v6mssdflt : #endif /* INET6 */ tcp_mssdflt; lck_mtx_unlock(rt_mtx); 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)) { /* * XXX the lock bit for RTT indicates that the value * is also a minimum value; this is subject to time. */ if (rt->rt_rmx.rmx_locks & RTV_RTT) tp->t_rttmin = rtt / (RTM_RTTUNIT / TCP_RETRANSHZ); else tp->t_rttmin = isnetlocal ? tcp_TCPTV_MIN : TCP_RETRANSHZ; tp->t_srtt = rtt / (RTM_RTTUNIT / (TCP_RETRANSHZ * TCP_RTT_SCALE)); tcpstat.tcps_usedrtt++; if (rt->rt_rmx.rmx_rttvar) { tp->t_rttvar = rt->rt_rmx.rmx_rttvar / (RTM_RTTUNIT / (TCP_RETRANSHZ * TCP_RTTVAR_SCALE)); tcpstat.tcps_usedrttvar++; } else { /* default variation is +- 1 rtt */ tp->t_rttvar = tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; } TCPT_RANGESET(tp->t_rxtcur, ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, tp->t_rttmin, TCPTV_REXMTMAX); } else tp->t_rttmin = isnetlocal ? tcp_TCPTV_MIN : TCP_RETRANSHZ; #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 the slow-start flight size depending on whether this * is a local network or not. */ if (isnetlocal) tp->snd_cwnd = mss * ss_fltsz_local; else tp->snd_cwnd = mss * ss_fltsz; 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; lck_mtx_unlock(rt_mtx); } /* * 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 lck_mtx_lock(rt_mtx); #if INET6 if (isipv6) rt = tcp_rtlookup6(tp->t_inpcb); else #endif /* INET6 */ rt = tcp_rtlookup(tp->t_inpcb, IFSCOPE_NONE); if (rt == NULL) { lck_mtx_unlock(rt_mtx); 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 lck_mtx_unlock(rt_mtx); 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 ti_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_long 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; tp->t_unacksegs = 0; (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) break; else {/* don't use if beeing accepted or used in any other way */ in_pcb_checkstate(inp, WNT_RELEASE, 1); tcp_unlock(so, 1, 0); } } } so = sonext; } if (!so) return 0; TAILQ_REMOVE(&head->so_incomp, so, so_list); tcp_unlock(head, 0, 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); tcp_lock(head, 0, 0); return 0; } if (so->so_usecount != 2 || !(so->so_state & SS_INCOMP)) { /* do not discard: that socket is beeing accepted */ tcp_unlock(so, 1, 0); tcp_lock(head, 0, 0); return 0; } so->so_head = NULL; /* * We do not want to lose track of the PCB right away in case we receive * more segments from the peer */ tp = sototcpcb(so); so->so_flags |= SOF_OVERFLOW; tp->t_state = TCPS_TIME_WAIT; (void) tcp_close(tp); tp->t_unacksegs = 0; tcpstat.tcps_drops++; tcp_canceltimers(tp); add_to_time_wait(tp); tcp_unlock(so, 1, 0); tcp_lock(head, 0, 0); head->so_incqlen--; head->so_qlen--; return 1; } 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, 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, &tcprexmtthresh, 0, &sysctl_rexmtthresh, "I", "Duplicate ACK Threshold for Fast Retransmit");