File:  [DragonFly] / src / sys / netinet / tcp_input.c
Revision 1.20: download - view: text, annotated - select for diffs
Tue Mar 9 21:21:54 2004 UTC (10 years, 6 months ago) by hsu
Branches: MAIN
CVS tags: HEAD
Clarify strange ipfw byte ordering convention.

Consulted with:	Luigi Rizzo <rizzo@icir.org>

    1: /*
    2:  * Copyright (c) 2002-2004 Jeffrey Hsu.  All rights reserved.
    3:  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
    4:  *	The Regents of the University of California.  All rights reserved.
    5:  *
    6:  * Redistribution and use in source and binary forms, with or without
    7:  * modification, are permitted provided that the following conditions
    8:  * are met:
    9:  * 1. Redistributions of source code must retain the above copyright
   10:  *    notice, this list of conditions and the following disclaimer.
   11:  * 2. Redistributions in binary form must reproduce the above copyright
   12:  *    notice, this list of conditions and the following disclaimer in the
   13:  *    documentation and/or other materials provided with the distribution.
   14:  * 3. All advertising materials mentioning features or use of this software
   15:  *    must display the following acknowledgement:
   16:  *	This product includes software developed by the University of
   17:  *	California, Berkeley and its contributors.
   18:  * 4. Neither the name of the University nor the names of its contributors
   19:  *    may be used to endorse or promote products derived from this software
   20:  *    without specific prior written permission.
   21:  *
   22:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32:  * SUCH DAMAGE.
   33:  *
   34:  *	@(#)tcp_input.c	8.12 (Berkeley) 5/24/95
   35:  * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $
   36:  * $DragonFly: src/sys/netinet/tcp_input.c,v 1.20 2004/03/09 21:21:54 hsu Exp $
   37:  */
   38: 
   39: #include "opt_ipfw.h"		/* for ipfw_fwd		*/
   40: #include "opt_inet6.h"
   41: #include "opt_ipsec.h"
   42: #include "opt_tcpdebug.h"
   43: #include "opt_tcp_input.h"
   44: 
   45: #include <sys/param.h>
   46: #include <sys/systm.h>
   47: #include <sys/kernel.h>
   48: #include <sys/sysctl.h>
   49: #include <sys/malloc.h>
   50: #include <sys/mbuf.h>
   51: #include <sys/proc.h>		/* for proc0 declaration */
   52: #include <sys/protosw.h>
   53: #include <sys/socket.h>
   54: #include <sys/socketvar.h>
   55: #include <sys/syslog.h>
   56: #include <sys/in_cksum.h>
   57: 
   58: #include <machine/cpu.h>	/* before tcp_seq.h, for tcp_random18() */
   59: 
   60: #include <net/if.h>
   61: #include <net/route.h>
   62: 
   63: #include <netinet/in.h>
   64: #include <netinet/in_systm.h>
   65: #include <netinet/ip.h>
   66: #include <netinet/ip_icmp.h>	/* for ICMP_BANDLIM		*/
   67: #include <netinet/in_var.h>
   68: #include <netinet/icmp_var.h>	/* for ICMP_BANDLIM		*/
   69: #include <netinet/in_pcb.h>
   70: #include <netinet/ip_var.h>
   71: #include <netinet/ip6.h>
   72: #include <netinet/icmp6.h>
   73: #include <netinet6/nd6.h>
   74: #include <netinet6/ip6_var.h>
   75: #include <netinet6/in6_pcb.h>
   76: #include <netinet/tcp.h>
   77: #include <netinet/tcp_fsm.h>
   78: #include <netinet/tcp_seq.h>
   79: #include <netinet/tcp_timer.h>
   80: #include <netinet/tcp_var.h>
   81: #include <netinet6/tcp6_var.h>
   82: #include <netinet/tcpip.h>
   83: #ifdef TCPDEBUG
   84: #include <netinet/tcp_debug.h>
   85: 
   86: u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
   87: struct tcphdr tcp_savetcp;
   88: #endif /* TCPDEBUG */
   89: 
   90: #ifdef FAST_IPSEC
   91: #include <netipsec/ipsec.h>
   92: #include <netipsec/ipsec6.h>
   93: #endif
   94: 
   95: #ifdef IPSEC
   96: #include <netinet6/ipsec.h>
   97: #include <netinet6/ipsec6.h>
   98: #include <netproto/key/key.h>
   99: #endif /*IPSEC*/
  100: 
  101: MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
  102: 
  103: static const int tcprexmtthresh = 3;
  104: tcp_cc	tcp_ccgen;
  105: 
  106: struct	tcpstat tcpstat;
  107: SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
  108:     &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
  109: 
  110: static int log_in_vain = 0;
  111: SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 
  112:     &log_in_vain, 0, "Log all incoming TCP connections");
  113: 
  114: static int blackhole = 0;
  115: SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
  116:     &blackhole, 0, "Do not send RST when dropping refused connections");
  117: 
  118: int tcp_delack_enabled = 1;
  119: SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 
  120:     &tcp_delack_enabled, 0, 
  121:     "Delay ACK to try and piggyback it onto a data packet");
  122: 
  123: #ifdef TCP_DROP_SYNFIN
  124: static int drop_synfin = 0;
  125: SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
  126:     &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
  127: #endif
  128: 
  129: static int tcp_do_limitedtransmit = 1;
  130: SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW,
  131:     &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)");
  132: 
  133: static int tcp_do_early_retransmit = 0;
  134: SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW,
  135:     &tcp_do_early_retransmit, 0, "Early retransmit");
  136: 
  137: static int tcp_do_rfc3390 = 1;
  138: SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
  139:     &tcp_do_rfc3390, 0,
  140:     "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
  141: 
  142: static int tcp_do_eifel_detect = 1;
  143: SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
  144:     &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
  145: 
  146: SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
  147:     "TCP Segment Reassembly Queue");
  148: 
  149: int tcp_reass_maxseg = 0;
  150: SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD,
  151:     &tcp_reass_maxseg, 0,
  152:     "Global maximum number of TCP Segments in Reassembly Queue");
  153: 
  154: int tcp_reass_qsize = 0;
  155: SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
  156:     &tcp_reass_qsize, 0,
  157:     "Global number of TCP Segments currently in Reassembly Queue");
  158: 
  159: static int tcp_reass_overflows = 0;
  160: SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
  161:     &tcp_reass_overflows, 0,
  162:     "Global number of TCP Segment Reassembly Queue Overflows");
  163: 
  164: struct inpcbinfo tcbinfo[MAXCPU];
  165: 
  166: static void	 tcp_dooptions(struct tcpopt *, u_char *, int, int);
  167: static void	 tcp_pulloutofband(struct socket *,
  168: 		     struct tcphdr *, struct mbuf *, int);
  169: static int	 tcp_reass(struct tcpcb *, struct tcphdr *, int *,
  170: 		     struct mbuf *);
  171: static void	 tcp_xmit_timer(struct tcpcb *, int);
  172: static void	 tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
  173: 
  174: /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
  175: #ifdef INET6
  176: #define ND6_HINT(tp) \
  177: do { \
  178: 	if ((tp) && (tp)->t_inpcb && \
  179: 	    ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \
  180: 	    (tp)->t_inpcb->in6p_route.ro_rt) \
  181: 		nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
  182: } while (0)
  183: #else
  184: #define ND6_HINT(tp)
  185: #endif
  186: 
  187: /*
  188:  * Indicate whether this ack should be delayed.  We can delay the ack if
  189:  *	- delayed acks are enabled and
  190:  *	- there is no delayed ack timer in progress and
  191:  *	- our last ack wasn't a 0-sized window.  We never want to delay
  192:  *	  the ack that opens up a 0-sized window.
  193:  */
  194: #define DELAY_ACK(tp) \
  195: 	(tcp_delack_enabled && !callout_pending(tp->tt_delack) && \
  196: 	(tp->t_flags & TF_RXWIN0SENT) == 0)
  197: 
  198: static int
  199: tcp_reass(tp, th, tlenp, m)
  200: 	struct tcpcb *tp;
  201: 	struct tcphdr *th;
  202: 	int *tlenp;
  203: 	struct mbuf *m;
  204: {
  205: 	struct tseg_qent *q;
  206: 	struct tseg_qent *p = NULL;
  207: 	struct tseg_qent *nq;
  208: 	struct tseg_qent *te;
  209: 	struct socket *so = tp->t_inpcb->inp_socket;
  210: 	int flags;
  211: 
  212: 	/*
  213: 	 * Call with th==0 after become established to
  214: 	 * force pre-ESTABLISHED data up to user socket.
  215: 	 */
  216: 	if (th == 0)
  217: 		goto present;
  218: 
  219: 	/*
  220: 	 * Limit the number of segments in the reassembly queue to prevent
  221: 	 * holding on to too many segments (and thus running out of mbufs).
  222: 	 * Make sure to let the missing segment through which caused this
  223: 	 * queue.  Always keep one global queue entry spare to be able to
  224: 	 * process the missing segment.
  225: 	 */
  226: 	if (th->th_seq != tp->rcv_nxt &&
  227: 	    tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
  228: 		tcp_reass_overflows++;
  229: 		tcpstat.tcps_rcvmemdrop++;
  230: 		m_freem(m);
  231: 		return (0);
  232: 	}
  233: 
  234: 	/* Allocate a new queue entry. If we can't, just drop the pkt. XXX */
  235: 	MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ,
  236: 	       M_NOWAIT);
  237: 	if (te == NULL) {
  238: 		tcpstat.tcps_rcvmemdrop++;
  239: 		m_freem(m);
  240: 		return (0);
  241: 	}
  242: 	tcp_reass_qsize++;
  243: 
  244: 	/*
  245: 	 * Find a segment which begins after this one does.
  246: 	 */
  247: 	LIST_FOREACH(q, &tp->t_segq, tqe_q) {
  248: 		if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
  249: 			break;
  250: 		p = q;
  251: 	}
  252: 
  253: 	/*
  254: 	 * If there is a preceding segment, it may provide some of
  255: 	 * our data already.  If so, drop the data from the incoming
  256: 	 * segment.  If it provides all of our data, drop us.
  257: 	 */
  258: 	if (p != NULL) {
  259: 		int i;
  260: 		/* conversion to int (in i) handles seq wraparound */
  261: 		i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
  262: 		if (i > 0) {
  263: 			if (i >= *tlenp) {
  264: 				tcpstat.tcps_rcvduppack++;
  265: 				tcpstat.tcps_rcvdupbyte += *tlenp;
  266: 				m_freem(m);
  267: 				free(te, M_TSEGQ);
  268: 				tcp_reass_qsize--;
  269: 				/*
  270: 				 * Try to present any queued data
  271: 				 * at the left window edge to the user.
  272: 				 * This is needed after the 3-WHS
  273: 				 * completes.
  274: 				 */
  275: 				goto present;	/* ??? */
  276: 			}
  277: 			m_adj(m, i);
  278: 			*tlenp -= i;
  279: 			th->th_seq += i;
  280: 		}
  281: 	}
  282: 	tcpstat.tcps_rcvoopack++;
  283: 	tcpstat.tcps_rcvoobyte += *tlenp;
  284: 
  285: 	/*
  286: 	 * While we overlap succeeding segments trim them or,
  287: 	 * if they are completely covered, dequeue them.
  288: 	 */
  289: 	while (q) {
  290: 		int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
  291: 		if (i <= 0)
  292: 			break;
  293: 		if (i < q->tqe_len) {
  294: 			q->tqe_th->th_seq += i;
  295: 			q->tqe_len -= i;
  296: 			m_adj(q->tqe_m, i);
  297: 			break;
  298: 		}
  299: 
  300: 		nq = LIST_NEXT(q, tqe_q);
  301: 		LIST_REMOVE(q, tqe_q);
  302: 		m_freem(q->tqe_m);
  303: 		free(q, M_TSEGQ);
  304: 		tcp_reass_qsize--;
  305: 		q = nq;
  306: 	}
  307: 
  308: 	/* Insert the new segment queue entry into place. */
  309: 	te->tqe_m = m;
  310: 	te->tqe_th = th;
  311: 	te->tqe_len = *tlenp;
  312: 
  313: 	if (p == NULL) {
  314: 		LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
  315: 	} else {
  316: 		LIST_INSERT_AFTER(p, te, tqe_q);
  317: 	}
  318: 
  319: present:
  320: 	/*
  321: 	 * Present data to user, advancing rcv_nxt through
  322: 	 * completed sequence space.
  323: 	 */
  324: 	if (!TCPS_HAVEESTABLISHED(tp->t_state))
  325: 		return (0);
  326: 	q = LIST_FIRST(&tp->t_segq);
  327: 	if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
  328: 		return (0);
  329: 	do {
  330: 		tp->rcv_nxt += q->tqe_len;
  331: 		flags = q->tqe_th->th_flags & TH_FIN;
  332: 		nq = LIST_NEXT(q, tqe_q);
  333: 		LIST_REMOVE(q, tqe_q);
  334: 		if (so->so_state & SS_CANTRCVMORE)
  335: 			m_freem(q->tqe_m);
  336: 		else
  337: 			sbappend(&so->so_rcv, q->tqe_m);
  338: 		free(q, M_TSEGQ);
  339: 		tcp_reass_qsize--;
  340: 		q = nq;
  341: 	} while (q && q->tqe_th->th_seq == tp->rcv_nxt);
  342: 	ND6_HINT(tp);
  343: 	sorwakeup(so);
  344: 	return (flags);
  345: }
  346: 
  347: /*
  348:  * TCP input routine, follows pages 65-76 of the
  349:  * protocol specification dated September, 1981 very closely.
  350:  */
  351: #ifdef INET6
  352: int
  353: tcp6_input(mp, offp, proto)
  354: 	struct mbuf **mp;
  355: 	int *offp, proto;
  356: {
  357: 	struct mbuf *m = *mp;
  358: 	struct in6_ifaddr *ia6;
  359: 
  360: 	IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
  361: 
  362: 	/*
  363: 	 * draft-itojun-ipv6-tcp-to-anycast
  364: 	 * better place to put this in?
  365: 	 */
  366: 	ia6 = ip6_getdstifaddr(m);
  367: 	if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {		
  368: 		struct ip6_hdr *ip6;
  369: 
  370: 		ip6 = mtod(m, struct ip6_hdr *);
  371: 		icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
  372: 			    (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
  373: 		return IPPROTO_DONE;
  374: 	}
  375: 
  376: 	tcp_input(m, *offp, proto);
  377: 	return IPPROTO_DONE;
  378: }
  379: #endif
  380: 
  381: void
  382: tcp_input(m, off0, proto)
  383: 	struct mbuf *m;
  384: 	int off0, proto;
  385: {
  386: 	struct tcphdr *th;
  387: 	struct ip *ip = NULL;
  388: 	struct ipovly *ipov;
  389: 	struct inpcb *inp = NULL;
  390: 	u_char *optp = NULL;
  391: 	int optlen = 0;
  392: 	int len, tlen, off;
  393: 	int drop_hdrlen;
  394: 	struct tcpcb *tp = NULL;
  395: 	int thflags;
  396: 	struct socket *so = 0;
  397: 	int todrop, acked, ourfinisacked, needoutput = 0;
  398: 	u_long tiwin;
  399: 	struct tcpopt to;		/* options in this segment */
  400: 	struct rmxp_tao *taop;		/* pointer to our TAO cache entry */
  401: 	struct rmxp_tao	tao_noncached;	/* in case there's no cached entry */
  402: 	struct sockaddr_in *next_hop = NULL;
  403: 	int rstreason; /* For badport_bandlim accounting purposes */
  404: 	int cpu;
  405: 	struct ip6_hdr *ip6 = NULL;
  406: #ifdef INET6
  407: 	int isipv6;
  408: #else
  409: 	const int isipv6 = 0;
  410: #endif
  411: #ifdef TCPDEBUG
  412: 	short ostate = 0;
  413: #endif
  414: 
  415: 	/* Grab info from MT_TAG mbufs prepended to the chain. */
  416: 	for (;m && m->m_type == MT_TAG; m = m->m_next) {
  417: 		if (m->_m_tag_id == PACKET_TAG_IPFORWARD)
  418: 			next_hop = (struct sockaddr_in *)m->m_hdr.mh_data;
  419: 	}
  420: #ifdef INET6
  421: 	isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
  422: #endif
  423: 	bzero((char *)&to, sizeof(to));
  424: 
  425: 	tcpstat.tcps_rcvtotal++;
  426: 
  427: 	if (isipv6) {
  428: 		/* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
  429: 		ip6 = mtod(m, struct ip6_hdr *);
  430: 		tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
  431: 		if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
  432: 			tcpstat.tcps_rcvbadsum++;
  433: 			goto drop;
  434: 		}
  435: 		th = (struct tcphdr *)((caddr_t)ip6 + off0);
  436: 
  437: 		/*
  438: 		 * Be proactive about unspecified IPv6 address in source.
  439: 		 * As we use all-zero to indicate unbounded/unconnected pcb,
  440: 		 * unspecified IPv6 address can be used to confuse us.
  441: 		 *
  442: 		 * Note that packets with unspecified IPv6 destination is
  443: 		 * already dropped in ip6_input.
  444: 		 */
  445: 		if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
  446: 			/* XXX stat */
  447: 			goto drop;
  448: 		}
  449: 	} else {
  450: 		/*
  451: 		 * Get IP and TCP header together in first mbuf.
  452: 		 * Note: IP leaves IP header in first mbuf.
  453: 		 */
  454: 		if (off0 > sizeof(struct ip)) {
  455: 			ip_stripoptions(m);
  456: 			off0 = sizeof(struct ip);
  457: 		}
  458: 		if (m->m_len < sizeof(struct tcpiphdr)) {
  459: 			if ((m = m_pullup(m, sizeof(struct tcpiphdr))) == 0) {
  460: 				tcpstat.tcps_rcvshort++;
  461: 				return;
  462: 			}
  463: 		}
  464: 		ip = mtod(m, struct ip *);
  465: 		ipov = (struct ipovly *)ip;
  466: 		th = (struct tcphdr *)((caddr_t)ip + off0);
  467: 		tlen = ip->ip_len;
  468: 
  469: 		if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
  470: 			if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
  471: 				th->th_sum = m->m_pkthdr.csum_data;
  472: 			else
  473: 				th->th_sum = in_pseudo(ip->ip_src.s_addr,
  474: 						ip->ip_dst.s_addr,
  475: 						htonl(m->m_pkthdr.csum_data +
  476: 							ip->ip_len +
  477: 							IPPROTO_TCP));
  478: 			th->th_sum ^= 0xffff;
  479: 		} else {
  480: 			/*
  481: 			 * Checksum extended TCP header and data.
  482: 			 */
  483: 			len = sizeof(struct ip) + tlen;
  484: 			bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
  485: 			ipov->ih_len = (u_short)tlen;
  486: 			ipov->ih_len = htons(ipov->ih_len);
  487: 			th->th_sum = in_cksum(m, len);
  488: 		}
  489: 		if (th->th_sum) {
  490: 			tcpstat.tcps_rcvbadsum++;
  491: 			goto drop;
  492: 		}
  493: #ifdef INET6
  494: 		/* Re-initialization for later version check */
  495: 		ip->ip_v = IPVERSION;
  496: #endif
  497: 	}
  498: 
  499: 	/*
  500: 	 * Check that TCP offset makes sense,
  501: 	 * pull out TCP options and adjust length.		XXX
  502: 	 */
  503: 	off = th->th_off << 2;
  504: 	if (off < sizeof(struct tcphdr) || off > tlen) {
  505: 		tcpstat.tcps_rcvbadoff++;
  506: 		goto drop;
  507: 	}
  508: 	tlen -= off;	/* tlen is used instead of ti->ti_len */
  509: 	if (off > sizeof(struct tcphdr)) {
  510: 		if (isipv6) {
  511: 			IP6_EXTHDR_CHECK(m, off0, off, );
  512: 			ip6 = mtod(m, struct ip6_hdr *);
  513: 			th = (struct tcphdr *)((caddr_t)ip6 + off0);
  514: 		} else {
  515: 			if (m->m_len < sizeof(struct ip) + off) {
  516: 				if ((m = m_pullup(m, sizeof(struct ip) + off))
  517: 						== 0) {
  518: 					tcpstat.tcps_rcvshort++;
  519: 					return;
  520: 				}
  521: 				ip = mtod(m, struct ip *);
  522: 				ipov = (struct ipovly *)ip;
  523: 				th = (struct tcphdr *)((caddr_t)ip + off0);
  524: 			}
  525: 		}
  526: 		optlen = off - sizeof(struct tcphdr);
  527: 		optp = (u_char *)(th + 1);
  528: 	}
  529: 	thflags = th->th_flags;
  530: 
  531: #ifdef TCP_DROP_SYNFIN
  532: 	/*
  533: 	 * If the drop_synfin option is enabled, drop all packets with
  534: 	 * both the SYN and FIN bits set. This prevents e.g. nmap from
  535: 	 * identifying the TCP/IP stack.
  536: 	 *
  537: 	 * This is a violation of the TCP specification.
  538: 	 */
  539: 	if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
  540: 		goto drop;
  541: #endif
  542: 
  543: 	/*
  544: 	 * Convert TCP protocol specific fields to host format.
  545: 	 */
  546: 	th->th_seq = ntohl(th->th_seq);
  547: 	th->th_ack = ntohl(th->th_ack);
  548: 	th->th_win = ntohs(th->th_win);
  549: 	th->th_urp = ntohs(th->th_urp);
  550: 
  551: 	/*
  552: 	 * Delay droping TCP, IP headers, IPv6 ext headers, and TCP options,
  553: 	 * until after ip6_savecontrol() is called and before other functions
  554: 	 * which don't want those proto headers.
  555: 	 * Because ip6_savecontrol() is going to parse the mbuf to
  556: 	 * search for data to be passed up to user-land, it wants mbuf
  557: 	 * parameters to be unchanged.
  558: 	 * XXX: the call of ip6_savecontrol() has been obsoleted based on
  559: 	 * latest version of the advanced API (20020110).
  560: 	 */
  561: 	drop_hdrlen = off0 + off;
  562: 
  563: 	/*
  564: 	 * Locate pcb for segment.
  565: 	 */
  566: findpcb:
  567: 	/* IPFIREWALL_FORWARD section */
  568: 	if (next_hop != NULL && isipv6 == 0) {  /* IPv6 support is not yet */
  569: 		/*
  570: 		 * Transparently forwarded. Pretend to be the destination.
  571: 		 * already got one like this? 
  572: 		 */
  573: 		inp = in_pcblookup_hash(&tcbinfo[mycpu->gd_cpuid],
  574: 					ip->ip_src, th->th_sport,
  575: 					ip->ip_dst, th->th_dport,
  576: 					0, m->m_pkthdr.rcvif);
  577: 		if (!inp) {
  578: 			/*
  579: 			 * It's new.  Try to find the ambushing socket.
  580: 			 */
  581: 
  582: 			/*
  583: 			 * The rest of the ipfw code stores the port in
  584: 			 * host order.  XXX
  585: 			 * (The IP address is still in network order.)
  586: 			 */
  587: 			in_port_t dport = next_hop->sin_port ?
  588: 						htons(next_hop->sin_port) :
  589: 						th->th_dport;
  590: 
  591: 			cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
  592: 					  next_hop->sin_addr.s_addr, dport);
  593: 			inp = in_pcblookup_hash(&tcbinfo[cpu],
  594: 						ip->ip_src, th->th_sport,
  595: 						next_hop->sin_addr, dport,
  596: 						1, m->m_pkthdr.rcvif);
  597: 		}
  598: 	} else {
  599: 		if (isipv6)
  600: 			inp = in6_pcblookup_hash(&tcbinfo[0],
  601: 						 &ip6->ip6_src, th->th_sport,
  602: 						 &ip6->ip6_dst, th->th_dport,
  603: 						 1, m->m_pkthdr.rcvif);
  604: 		else
  605: 			inp = in_pcblookup_hash(&tcbinfo[mycpu->gd_cpuid],
  606: 						ip->ip_src, th->th_sport,
  607: 						ip->ip_dst, th->th_dport,
  608: 						1, m->m_pkthdr.rcvif);
  609:       }
  610: 
  611: #ifdef IPSEC
  612: 	if (isipv6) {
  613: 		if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) {
  614: 			ipsec6stat.in_polvio++;
  615: 			goto drop;
  616: 		}
  617: 	} else {
  618: 		if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) {
  619: 			ipsecstat.in_polvio++;
  620: 			goto drop;
  621: 		}
  622: 	}
  623: #endif
  624: #ifdef FAST_IPSEC
  625: 	if (isipv6) {
  626: 		if (inp != NULL && ipsec6_in_reject(m, inp)) {
  627: 			goto drop;
  628: 		}
  629: 	} else {
  630: 		if (inp != NULL && ipsec4_in_reject(m, inp)) {
  631: 			goto drop;
  632: 		}
  633: 	}
  634: #endif
  635: 
  636: 	/*
  637: 	 * If the state is CLOSED (i.e., TCB does not exist) then
  638: 	 * all data in the incoming segment is discarded.
  639: 	 * If the TCB exists but is in CLOSED state, it is embryonic,
  640: 	 * but should either do a listen or a connect soon.
  641: 	 */
  642: 	if (inp == NULL) {
  643: 		if (log_in_vain) {
  644: #ifdef INET6
  645: 			char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
  646: #else
  647: 			char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"];
  648: #endif
  649: 			if (isipv6) {
  650: 				strcpy(dbuf, "[");
  651: 				strcpy(sbuf, "[");
  652: 				strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
  653: 				strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
  654: 				strcat(dbuf, "]");
  655: 				strcat(sbuf, "]");
  656: 			} else {
  657: 				strcpy(dbuf, inet_ntoa(ip->ip_dst));
  658: 				strcpy(sbuf, inet_ntoa(ip->ip_src));
  659: 			}
  660: 			switch (log_in_vain) {
  661: 			case 1:
  662: 				if ((thflags & TH_SYN) == 0)
  663: 					break;
  664: 			case 2:
  665: 				log(LOG_INFO,
  666: 				    "Connection attempt to TCP %s:%d "
  667: 				    "from %s:%d flags:0x%02x\n",
  668: 				    dbuf, ntohs(th->th_dport), sbuf,
  669: 				    ntohs(th->th_sport), thflags);
  670: 				break;
  671: 			default:
  672: 				break;
  673: 			}
  674: 		}
  675: 		if (blackhole) { 
  676: 			switch (blackhole) {
  677: 			case 1:
  678: 				if (thflags & TH_SYN)
  679: 					goto drop;
  680: 				break;
  681: 			case 2:
  682: 				goto drop;
  683: 			default:
  684: 				goto drop;
  685: 			}
  686: 		}
  687: 		rstreason = BANDLIM_RST_CLOSEDPORT;
  688: 		goto dropwithreset;
  689: 	}
  690: 	tp = intotcpcb(inp);
  691: 	if (tp == NULL) {
  692: 		rstreason = BANDLIM_RST_CLOSEDPORT;
  693: 		goto dropwithreset;
  694: 	}
  695: 	if (tp->t_state == TCPS_CLOSED)
  696: 		goto drop;
  697: 
  698: 	/* Unscale the window into a 32-bit value. */
  699: 	if ((thflags & TH_SYN) == 0)
  700: 		tiwin = th->th_win << tp->snd_scale;
  701: 	else
  702: 		tiwin = th->th_win;
  703: 
  704: 	so = inp->inp_socket;
  705: 
  706: #ifdef TCPDEBUG
  707: 	if (so->so_options & SO_DEBUG) {
  708: 		ostate = tp->t_state;
  709: 		if (isipv6)
  710: 			bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
  711: 		else
  712: 			bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
  713: 		tcp_savetcp = *th;
  714: 	}
  715: #endif
  716: 
  717: 	if (so->so_options & SO_ACCEPTCONN) {
  718: 		struct in_conninfo inc;
  719: 
  720: #ifdef INET6
  721: 		inc.inc_isipv6 = isipv6;
  722: #endif
  723: 		if (isipv6) {
  724: 			inc.inc6_faddr = ip6->ip6_src;
  725: 			inc.inc6_laddr = ip6->ip6_dst;
  726: 			inc.inc6_route.ro_rt = NULL;		/* XXX */
  727: 		} else {
  728: 			inc.inc_faddr = ip->ip_src;
  729: 			inc.inc_laddr = ip->ip_dst;
  730: 			inc.inc_route.ro_rt = NULL;		/* XXX */
  731: 		}
  732: 		inc.inc_fport = th->th_sport;
  733: 		inc.inc_lport = th->th_dport;
  734: 
  735: 	        /*
  736: 	         * If the state is LISTEN then ignore segment if it contains
  737: 		 * a RST.  If the segment contains an ACK then it is bad and
  738: 		 * send a RST.  If it does not contain a SYN then it is not
  739: 		 * interesting; drop it.
  740: 		 *
  741: 		 * If the state is SYN_RECEIVED (syncache) and seg contains
  742: 		 * an ACK, but not for our SYN/ACK, send a RST.  If the seg
  743: 		 * contains a RST, check the sequence number to see if it
  744: 		 * is a valid reset segment.
  745: 		 */
  746: 		if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
  747: 			if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
  748: 				if (!syncache_expand(&inc, th, &so, m)) {
  749: 					/*
  750: 					 * No syncache entry, or ACK was not
  751: 					 * for our SYN/ACK.  Send a RST.
  752: 					 */
  753: 					tcpstat.tcps_badsyn++;
  754: 					rstreason = BANDLIM_RST_OPENPORT;
  755: 					goto dropwithreset;
  756: 				}
  757: 				if (so == NULL)
  758: 					/*
  759: 					 * Could not complete 3-way handshake,
  760: 					 * connection is being closed down, and
  761: 					 * syncache will free mbuf.
  762: 					 */
  763: 					return;
  764: 				/*
  765: 				 * Socket is created in state SYN_RECEIVED.
  766: 				 * Continue processing segment.
  767: 				 */
  768: 				inp = sotoinpcb(so);
  769: 				tp = intotcpcb(inp);
  770: 				/*
  771: 				 * This is what would have happened in
  772: 				 * tcp_output() when the SYN,ACK was sent.
  773: 				 */
  774: 				tp->snd_up = tp->snd_una;
  775: 				tp->snd_max = tp->snd_nxt = tp->iss + 1;
  776: 				tp->last_ack_sent = tp->rcv_nxt;
  777: /*
  778:  * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled
  779:  * until the _second_ ACK is received:
  780:  *    rcv SYN (set wscale opts)	 --> send SYN/ACK, set snd_wnd = window.
  781:  *    rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale,
  782:  *        move to ESTAB, set snd_wnd to tiwin.
  783:  */        
  784: 				tp->snd_wnd = tiwin;	/* unscaled */
  785: 				goto after_listen;
  786: 			}
  787: 			if (thflags & TH_RST) {
  788: 				syncache_chkrst(&inc, th);
  789: 				goto drop;
  790: 			}
  791: 			if (thflags & TH_ACK) {
  792: 				syncache_badack(&inc);
  793: 				tcpstat.tcps_badsyn++;
  794: 				rstreason = BANDLIM_RST_OPENPORT;
  795: 				goto dropwithreset;
  796: 			}
  797: 			goto drop;
  798: 		}
  799: 
  800: 		/*
  801: 		 * Segment's flags are (SYN) or (SYN|FIN).
  802: 		 */
  803: #ifdef INET6
  804: 		/*
  805: 		 * If deprecated address is forbidden,
  806: 		 * we do not accept SYN to deprecated interface
  807: 		 * address to prevent any new inbound connection from
  808: 		 * getting established.
  809: 		 * When we do not accept SYN, we send a TCP RST,
  810: 		 * with deprecated source address (instead of dropping
  811: 		 * it).  We compromise it as it is much better for peer
  812: 		 * to send a RST, and RST will be the final packet
  813: 		 * for the exchange.
  814: 		 *
  815: 		 * If we do not forbid deprecated addresses, we accept
  816: 		 * the SYN packet.  RFC2462 does not suggest dropping
  817: 		 * SYN in this case.
  818: 		 * If we decipher RFC2462 5.5.4, it says like this:
  819: 		 * 1. use of deprecated addr with existing
  820: 		 *    communication is okay - "SHOULD continue to be
  821: 		 *    used"
  822: 		 * 2. use of it with new communication:
  823: 		 *   (2a) "SHOULD NOT be used if alternate address
  824: 		 *        with sufficient scope is available"
  825: 		 *   (2b) nothing mentioned otherwise.
  826: 		 * Here we fall into (2b) case as we have no choice in
  827: 		 * our source address selection - we must obey the peer.
  828: 		 *
  829: 		 * The wording in RFC2462 is confusing, and there are
  830: 		 * multiple description text for deprecated address
  831: 		 * handling - worse, they are not exactly the same.
  832: 		 * I believe 5.5.4 is the best one, so we follow 5.5.4.
  833: 		 */
  834: 		if (isipv6 && !ip6_use_deprecated) {
  835: 			struct in6_ifaddr *ia6;
  836: 
  837: 			if ((ia6 = ip6_getdstifaddr(m)) &&
  838: 			    (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
  839: 				tp = NULL;
  840: 				rstreason = BANDLIM_RST_OPENPORT;
  841: 				goto dropwithreset;
  842: 			}
  843: 		}
  844: #endif
  845: 		/*
  846: 		 * If it is from this socket, drop it, it must be forged.
  847: 		 * Don't bother responding if the destination was a broadcast.
  848: 		 */
  849: 		if (th->th_dport == th->th_sport) {
  850: 			if (isipv6) {
  851: 				if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
  852: 						       &ip6->ip6_src))
  853: 					goto drop;
  854: 			} else {
  855: 				if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
  856: 					goto drop;
  857: 			}
  858: 		}
  859: 		/*
  860: 		 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
  861: 		 *
  862: 		 * Note that it is quite possible to receive unicast
  863: 		 * link-layer packets with a broadcast IP address. Use
  864: 		 * in_broadcast() to find them.
  865: 		 */
  866: 		if (m->m_flags & (M_BCAST|M_MCAST))
  867: 			goto drop;
  868: 		if (isipv6) {
  869: 			if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
  870: 			    IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
  871: 				goto drop;
  872: 		} else {
  873: 			if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
  874: 			    IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
  875: 			    ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
  876: 			    in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
  877: 				goto drop;
  878: 		}
  879: 		/*
  880: 		 * SYN appears to be valid; create compressed TCP state
  881: 		 * for syncache, or perform t/tcp connection.
  882: 		 */
  883: 		if (so->so_qlen <= so->so_qlimit) {
  884: 			tcp_dooptions(&to, optp, optlen, 1);
  885: 			if (!syncache_add(&inc, &to, th, &so, m))
  886: 				goto drop;
  887: 			if (so == NULL)
  888: 				/*
  889: 				 * Entry added to syncache, mbuf used to
  890: 				 * send SYN,ACK packet.
  891: 				 */
  892: 				return;
  893: 			/*
  894: 			 * Segment passed TAO tests.
  895: 			 */
  896: 			inp = sotoinpcb(so);
  897: 			tp = intotcpcb(inp);
  898: 			tp->snd_wnd = tiwin;
  899: 			tp->t_starttime = ticks;
  900: 			tp->t_state = TCPS_ESTABLISHED;
  901: 
  902: 			/*
  903: 			 * If there is a FIN, or if there is data and the
  904: 			 * connection is local, then delay SYN,ACK(SYN) in
  905: 			 * the hope of piggy-backing it on a response
  906: 			 * segment.  Otherwise must send ACK now in case
  907: 			 * the other side is slow starting.
  908: 			 */
  909: 			if (DELAY_ACK(tp) &&
  910: 			    ((thflags & TH_FIN) ||
  911: 			     (tlen != 0 &&
  912: 			      ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
  913: 			       (!isipv6 && in_localaddr(inp->inp_faddr)))))) {
  914: 				callout_reset(tp->tt_delack, tcp_delacktime,  
  915: 						tcp_timer_delack, tp);  
  916: 				tp->t_flags |= TF_NEEDSYN;
  917: 			} else 
  918: 				tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
  919: 
  920: 			tcpstat.tcps_connects++;
  921: 			soisconnected(so);
  922: 			goto trimthenstep6;
  923: 		}
  924: 		goto drop;
  925: 	}
  926: after_listen:
  927: 
  928: /* XXX temp debugging */
  929: 	/* should not happen - syncache should pick up these connections */
  930: 	if (tp->t_state == TCPS_LISTEN)
  931: 		panic("tcp_input: TCPS_LISTEN");
  932: 
  933: 	/*
  934: 	 * Segment received on connection.
  935: 	 * Reset idle time and keep-alive timer.
  936: 	 */
  937: 	tp->t_rcvtime = ticks;
  938: 	if (TCPS_HAVEESTABLISHED(tp->t_state))
  939: 		callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
  940: 
  941: 	/*
  942: 	 * Process options.
  943: 	 * XXX this is tradtitional behavior, may need to be cleaned up.
  944: 	 */
  945: 	tcp_dooptions(&to, optp, optlen, thflags & TH_SYN);
  946: 	if (thflags & TH_SYN) {
  947: 		if (to.to_flags & TOF_SCALE) {
  948: 			tp->t_flags |= TF_RCVD_SCALE;
  949: 			tp->requested_s_scale = to.to_requested_s_scale;
  950: 		}
  951: 		if (to.to_flags & TOF_TS) {
  952: 			tp->t_flags |= TF_RCVD_TSTMP;
  953: 			tp->ts_recent = to.to_tsval;
  954: 			tp->ts_recent_age = ticks;
  955: 		}
  956: 		if (to.to_flags & (TOF_CC|TOF_CCNEW))
  957: 			tp->t_flags |= TF_RCVD_CC;
  958: 		if (to.to_flags & TOF_MSS)
  959: 			tcp_mss(tp, to.to_mss);
  960: 	}
  961: 
  962: 	/*
  963: 	 * Header prediction: check for the two common cases
  964: 	 * of a uni-directional data xfer.  If the packet has
  965: 	 * no control flags, is in-sequence, the window didn't
  966: 	 * change and we're not retransmitting, it's a
  967: 	 * candidate.  If the length is zero and the ack moved
  968: 	 * forward, we're the sender side of the xfer.  Just
  969: 	 * free the data acked & wake any higher level process
  970: 	 * that was blocked waiting for space.  If the length
  971: 	 * is non-zero and the ack didn't move, we're the
  972: 	 * receiver side.  If we're getting packets in-order
  973: 	 * (the reassembly queue is empty), add the data to
  974: 	 * the socket buffer and note that we need a delayed ack.
  975: 	 * Make sure that the hidden state-flags are also off.
  976: 	 * Since we check for TCPS_ESTABLISHED above, it can only
  977: 	 * be TH_NEEDSYN.
  978: 	 */
  979: 	if (tp->t_state == TCPS_ESTABLISHED &&
  980: 	    (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
  981: 	    ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
  982: 	    ((to.to_flags & TOF_TS) == 0 ||
  983: 	     TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
  984: 	    /*
  985: 	     * Using the CC option is compulsory if once started:
  986: 	     *   the segment is OK if no T/TCP was negotiated or
  987: 	     *   if the segment has a CC option equal to CCrecv
  988: 	     */
  989: 	    ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
  990: 	     ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) &&
  991: 	    th->th_seq == tp->rcv_nxt &&
  992: 	    tiwin && tiwin == tp->snd_wnd &&
  993: 	    tp->snd_nxt == tp->snd_max) {
  994: 
  995: 		/*
  996: 		 * If last ACK falls within this segment's sequence numbers,
  997: 		 * record the timestamp.
  998: 		 * NOTE that the test is modified according to the latest
  999: 		 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
 1000: 		 */
 1001: 		if ((to.to_flags & TOF_TS) != 0 &&
 1002: 		    SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
 1003: 			tp->ts_recent_age = ticks;
 1004: 			tp->ts_recent = to.to_tsval;
 1005: 		}
 1006: 
 1007: 		if (tlen == 0) {
 1008: 			if (SEQ_GT(th->th_ack, tp->snd_una) &&
 1009: 			    SEQ_LEQ(th->th_ack, tp->snd_max) &&
 1010: 			    tp->snd_cwnd >= tp->snd_wnd &&
 1011: 			    ((!tcp_do_newreno &&
 1012: 			      tp->t_dupacks < tcprexmtthresh) ||
 1013: 			     (tcp_do_newreno && !IN_FASTRECOVERY(tp)))) {
 1014: 				/*
 1015: 				 * this is a pure ack for outstanding data.
 1016: 				 */
 1017: 				++tcpstat.tcps_predack;
 1018: 				/*
 1019: 				 * "bad retransmit" recovery
 1020: 				 *
 1021: 				 * If Eifel detection applies, then
 1022: 				 * it is deterministic, so use it
 1023: 				 * unconditionally over the old heuristic.
 1024: 				 * Otherwise, fall back to the old heuristic.
 1025: 				 */
 1026: 				if (tcp_do_eifel_detect &&
 1027: 				    (to.to_flags & TOF_TS) && to.to_tsecr &&
 1028: 				    (tp->t_flags & TF_FIRSTACCACK)) {
 1029: 					/* Eifel detection applicable. */
 1030: 					if (to.to_tsecr < tp->t_rexmtTS) {
 1031: 						tcp_revert_congestion_state(tp);
 1032: 						++tcpstat.tcps_eifeldetected;
 1033: 					}
 1034: 				} else if (tp->t_rxtshift == 1 &&
 1035: 					   ticks < tp->t_badrxtwin) {
 1036: 					tcp_revert_congestion_state(tp);
 1037: 					++tcpstat.tcps_rttdetected;
 1038: 				}
 1039: 				tp->t_flags &= ~(TF_FIRSTACCACK |
 1040: 						 TF_FASTREXMT | TF_EARLYREXMT);
 1041: 				/*
 1042: 				 * Recalculate the retransmit timer / rtt.
 1043: 				 *
 1044: 				 * Some machines (certain windows boxes) 
 1045: 				 * send broken timestamp replies during the
 1046: 				 * SYN+ACK phase, ignore timestamps of 0.
 1047: 				 */
 1048: 				if ((to.to_flags & TOF_TS) != 0 &&
 1049: 				    to.to_tsecr) {
 1050: 					tcp_xmit_timer(tp,
 1051: 					    ticks - to.to_tsecr + 1);
 1052: 				} else if (tp->t_rtttime &&
 1053: 					    SEQ_GT(th->th_ack, tp->t_rtseq)) {
 1054: 					tcp_xmit_timer(tp,
 1055: 						       ticks - tp->t_rtttime);
 1056: 				}
 1057: 				tcp_xmit_bandwidth_limit(tp, th->th_ack);
 1058: 				acked = th->th_ack - tp->snd_una;
 1059: 				tcpstat.tcps_rcvackpack++;
 1060: 				tcpstat.tcps_rcvackbyte += acked;
 1061: 				sbdrop(&so->so_snd, acked);
 1062: 				if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
 1063: 				    SEQ_LEQ(th->th_ack, tp->snd_recover))
 1064: 					tp->snd_recover = th->th_ack - 1;
 1065: 				tp->snd_una = th->th_ack;
 1066: 				tp->t_dupacks = 0;
 1067: 				m_freem(m);
 1068: 				ND6_HINT(tp); /* some progress has been done */
 1069: 
 1070: 				/*
 1071: 				 * If all outstanding data are acked, stop
 1072: 				 * retransmit timer, otherwise restart timer
 1073: 				 * using current (possibly backed-off) value.
 1074: 				 * If process is waiting for space,
 1075: 				 * wakeup/selwakeup/signal.  If data
 1076: 				 * are ready to send, let tcp_output
 1077: 				 * decide between more output or persist.
 1078: 				 */
 1079: 				if (tp->snd_una == tp->snd_max)
 1080: 					callout_stop(tp->tt_rexmt);
 1081: 				else if (!callout_active(tp->tt_persist))
 1082: 					callout_reset(tp->tt_rexmt, 
 1083: 						      tp->t_rxtcur,
 1084: 						      tcp_timer_rexmt, tp);
 1085: 
 1086: 				sowwakeup(so);
 1087: 				if (so->so_snd.sb_cc)
 1088: 					(void) tcp_output(tp);
 1089: 				return;
 1090: 			}
 1091: 		} else if (th->th_ack == tp->snd_una &&
 1092: 		    LIST_EMPTY(&tp->t_segq) &&
 1093: 		    tlen <= sbspace(&so->so_rcv)) {
 1094: 			/*
 1095: 			 * this is a pure, in-sequence data packet
 1096: 			 * with nothing on the reassembly queue and
 1097: 			 * we have enough buffer space to take it.
 1098: 			 */
 1099: 			++tcpstat.tcps_preddat;
 1100: 			tp->rcv_nxt += tlen;
 1101: 			tcpstat.tcps_rcvpack++;
 1102: 			tcpstat.tcps_rcvbyte += tlen;
 1103: 			ND6_HINT(tp);	/* some progress has been done */
 1104: 			/*
 1105: 			 * Add data to socket buffer.
 1106: 			 */
 1107: 			if (so->so_state & SS_CANTRCVMORE) {
 1108: 				m_freem(m);
 1109: 			} else {
 1110: 				m_adj(m, drop_hdrlen);	/* delayed header drop */
 1111: 				sbappend(&so->so_rcv, m);
 1112: 			}
 1113: 			sorwakeup(so);
 1114: 			if (DELAY_ACK(tp)) {
 1115: 	                        callout_reset(tp->tt_delack, tcp_delacktime,
 1116: 	                            tcp_timer_delack, tp);
 1117: 			} else {
 1118: 				tp->t_flags |= TF_ACKNOW;
 1119: 				tcp_output(tp);
 1120: 			}
 1121: 			return;
 1122: 		}
 1123: 	}
 1124: 
 1125: 	/*
 1126: 	 * Calculate amount of space in receive window,
 1127: 	 * and then do TCP input processing.
 1128: 	 * Receive window is amount of space in rcv queue,
 1129: 	 * but not less than advertised window.
 1130: 	 */
 1131: 	{ int win;
 1132: 
 1133: 	win = sbspace(&so->so_rcv);
 1134: 	if (win < 0)
 1135: 		win = 0;
 1136: 	tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
 1137: 	}
 1138: 
 1139: 	switch (tp->t_state) {
 1140: 
 1141: 	/*
 1142: 	 * If the state is SYN_RECEIVED:
 1143: 	 *	if seg contains an ACK, but not for our SYN/ACK, send a RST.
 1144: 	 */
 1145: 	case TCPS_SYN_RECEIVED:
 1146: 		if ((thflags & TH_ACK) &&
 1147: 		    (SEQ_LEQ(th->th_ack, tp->snd_una) ||
 1148: 		     SEQ_GT(th->th_ack, tp->snd_max))) {
 1149: 				rstreason = BANDLIM_RST_OPENPORT;
 1150: 				goto dropwithreset;
 1151: 		}
 1152: 		break;
 1153: 
 1154: 	/*
 1155: 	 * If the state is SYN_SENT:
 1156: 	 *	if seg contains an ACK, but not for our SYN, drop the input.
 1157: 	 *	if seg contains a RST, then drop the connection.
 1158: 	 *	if seg does not contain SYN, then drop it.
 1159: 	 * Otherwise this is an acceptable SYN segment
 1160: 	 *	initialize tp->rcv_nxt and tp->irs
 1161: 	 *	if seg contains ack then advance tp->snd_una
 1162: 	 *	if SYN has been acked change to ESTABLISHED else SYN_RCVD state
 1163: 	 *	arrange for segment to be acked (eventually)
 1164: 	 *	continue processing rest of data/controls, beginning with URG
 1165: 	 */
 1166: 	case TCPS_SYN_SENT:
 1167: 		if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) {
 1168: 			taop = &tao_noncached;
 1169: 			bzero(taop, sizeof(*taop));
 1170: 		}
 1171: 
 1172: 		if ((thflags & TH_ACK) &&
 1173: 		    (SEQ_LEQ(th->th_ack, tp->iss) ||
 1174: 		     SEQ_GT(th->th_ack, tp->snd_max))) {
 1175: 			/*
 1176: 			 * If we have a cached CCsent for the remote host,
 1177: 			 * hence we haven't just crashed and restarted,
 1178: 			 * do not send a RST.  This may be a retransmission
 1179: 			 * from the other side after our earlier ACK was lost.
 1180: 			 * Our new SYN, when it arrives, will serve as the
 1181: 			 * needed ACK.
 1182: 			 */
 1183: 			if (taop->tao_ccsent != 0)
 1184: 				goto drop;
 1185: 			else {
 1186: 				rstreason = BANDLIM_UNLIMITED;
 1187: 				goto dropwithreset;
 1188: 			}
 1189: 		}
 1190: 		if (thflags & TH_RST) {
 1191: 			if (thflags & TH_ACK)
 1192: 				tp = tcp_drop(tp, ECONNREFUSED);
 1193: 			goto drop;
 1194: 		}
 1195: 		if ((thflags & TH_SYN) == 0)
 1196: 			goto drop;
 1197: 		tp->snd_wnd = th->th_win;	/* initial send window */
 1198: 		tp->cc_recv = to.to_cc;		/* foreign CC */
 1199: 
 1200: 		tp->irs = th->th_seq;
 1201: 		tcp_rcvseqinit(tp);
 1202: 		if (thflags & TH_ACK) {
 1203: 			/*
 1204: 			 * Our SYN was acked.  If segment contains CC.ECHO
 1205: 			 * option, check it to make sure this segment really
 1206: 			 * matches our SYN.  If not, just drop it as old
 1207: 			 * duplicate, but send an RST if we're still playing
 1208: 			 * by the old rules.  If no CC.ECHO option, make sure
 1209: 			 * we don't get fooled into using T/TCP.
 1210: 			 */
 1211: 			if (to.to_flags & TOF_CCECHO) {
 1212: 				if (tp->cc_send != to.to_ccecho) {
 1213: 					if (taop->tao_ccsent != 0)
 1214: 						goto drop;
 1215: 					else {
 1216: 						rstreason = BANDLIM_UNLIMITED;
 1217: 						goto dropwithreset;
 1218: 					}
 1219: 				}
 1220: 			} else
 1221: 				tp->t_flags &= ~TF_RCVD_CC;
 1222: 			tcpstat.tcps_connects++;
 1223: 			soisconnected(so);
 1224: 			/* Do window scaling on this connection? */
 1225: 			if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
 1226: 				(TF_RCVD_SCALE|TF_REQ_SCALE)) {
 1227: 				tp->snd_scale = tp->requested_s_scale;
 1228: 				tp->rcv_scale = tp->request_r_scale;
 1229: 			}
 1230: 			/* Segment is acceptable, update cache if undefined. */
 1231: 			if (taop->tao_ccsent == 0)
 1232: 				taop->tao_ccsent = to.to_ccecho;
 1233: 
 1234: 			tp->rcv_adv += tp->rcv_wnd;
 1235: 			tp->snd_una++;		/* SYN is acked */
 1236: 			/*
 1237: 			 * If there's data, delay ACK; if there's also a FIN
 1238: 			 * ACKNOW will be turned on later.
 1239: 			 */
 1240: 			if (DELAY_ACK(tp) && tlen != 0)
 1241:                                 callout_reset(tp->tt_delack, tcp_delacktime,  
 1242:                                     tcp_timer_delack, tp);  
 1243: 			else
 1244: 				tp->t_flags |= TF_ACKNOW;
 1245: 			/*
 1246: 			 * Received <SYN,ACK> in SYN_SENT[*] state.
 1247: 			 * Transitions:
 1248: 			 *	SYN_SENT  --> ESTABLISHED
 1249: 			 *	SYN_SENT* --> FIN_WAIT_1
 1250: 			 */
 1251: 			tp->t_starttime = ticks;
 1252: 			if (tp->t_flags & TF_NEEDFIN) {
 1253: 				tp->t_state = TCPS_FIN_WAIT_1;
 1254: 				tp->t_flags &= ~TF_NEEDFIN;
 1255: 				thflags &= ~TH_SYN;
 1256: 			} else {
 1257: 				tp->t_state = TCPS_ESTABLISHED;
 1258: 				callout_reset(tp->tt_keep, tcp_keepidle,
 1259: 					      tcp_timer_keep, tp);
 1260: 			}
 1261: 		} else {
 1262: 			/*
 1263: 		 	 * Received initial SYN in SYN-SENT[*] state =>
 1264: 		 	 * simultaneous open.  If segment contains CC option
 1265: 		 	 * and there is a cached CC, apply TAO test.
 1266: 		 	 * If it succeeds, connection is * half-synchronized.
 1267: 		 	 * Otherwise, do 3-way handshake:
 1268: 		 	 *        SYN-SENT -> SYN-RECEIVED
 1269: 		 	 *        SYN-SENT* -> SYN-RECEIVED*
 1270: 		 	 * If there was no CC option, clear cached CC value.
 1271: 		 	 */
 1272: 			tp->t_flags |= TF_ACKNOW;
 1273: 			callout_stop(tp->tt_rexmt);
 1274: 			if (to.to_flags & TOF_CC) {
 1275: 				if (taop->tao_cc != 0 &&
 1276: 				    CC_GT(to.to_cc, taop->tao_cc)) {
 1277: 					/*
 1278: 					 * update cache and make transition:
 1279: 					 *        SYN-SENT -> ESTABLISHED*
 1280: 					 *        SYN-SENT* -> FIN-WAIT-1*
 1281: 					 */
 1282: 					taop->tao_cc = to.to_cc;
 1283: 					tp->t_starttime = ticks;
 1284: 					if (tp->t_flags & TF_NEEDFIN) {
 1285: 						tp->t_state = TCPS_FIN_WAIT_1;
 1286: 						tp->t_flags &= ~TF_NEEDFIN;
 1287: 					} else {
 1288: 						tp->t_state = TCPS_ESTABLISHED;
 1289: 						callout_reset(tp->tt_keep,
 1290: 							      tcp_keepidle,
 1291: 							      tcp_timer_keep,
 1292: 							      tp);
 1293: 					}
 1294: 					tp->t_flags |= TF_NEEDSYN;
 1295: 				} else
 1296: 					tp->t_state = TCPS_SYN_RECEIVED;
 1297: 			} else {
 1298: 				/* CC.NEW or no option => invalidate cache */
 1299: 				taop->tao_cc = 0;
 1300: 				tp->t_state = TCPS_SYN_RECEIVED;
 1301: 			}
 1302: 		}
 1303: 
 1304: trimthenstep6:
 1305: 		/*
 1306: 		 * Advance th->th_seq to correspond to first data byte.
 1307: 		 * If data, trim to stay within window,
 1308: 		 * dropping FIN if necessary.
 1309: 		 */
 1310: 		th->th_seq++;
 1311: 		if (tlen > tp->rcv_wnd) {
 1312: 			todrop = tlen - tp->rcv_wnd;
 1313: 			m_adj(m, -todrop);
 1314: 			tlen = tp->rcv_wnd;
 1315: 			thflags &= ~TH_FIN;
 1316: 			tcpstat.tcps_rcvpackafterwin++;
 1317: 			tcpstat.tcps_rcvbyteafterwin += todrop;
 1318: 		}
 1319: 		tp->snd_wl1 = th->th_seq - 1;
 1320: 		tp->rcv_up = th->th_seq;
 1321: 		/*
 1322: 		 * Client side of transaction: already sent SYN and data.
 1323: 		 * If the remote host used T/TCP to validate the SYN,
 1324: 		 * our data will be ACK'd; if so, enter normal data segment
 1325: 		 * processing in the middle of step 5, ack processing.
 1326: 		 * Otherwise, goto step 6.
 1327: 		 */
 1328:  		if (thflags & TH_ACK)
 1329: 			goto process_ACK;
 1330: 
 1331: 		goto step6;
 1332: 
 1333: 	/*
 1334: 	 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
 1335: 	 *	if segment contains a SYN and CC [not CC.NEW] option:
 1336: 	 *              if state == TIME_WAIT and connection duration > MSL,
 1337: 	 *                  drop packet and send RST;
 1338: 	 *
 1339: 	 *		if SEG.CC > CCrecv then is new SYN, and can implicitly
 1340: 	 *		    ack the FIN (and data) in retransmission queue.
 1341: 	 *                  Complete close and delete TCPCB.  Then reprocess
 1342: 	 *                  segment, hoping to find new TCPCB in LISTEN state;
 1343: 	 *
 1344: 	 *		else must be old SYN; drop it.
 1345: 	 *      else do normal processing.
 1346: 	 */
 1347: 	case TCPS_LAST_ACK:
 1348: 	case TCPS_CLOSING:
 1349: 	case TCPS_TIME_WAIT:
 1350: 		if ((thflags & TH_SYN) &&
 1351: 		    (to.to_flags & TOF_CC) && tp->cc_recv != 0) {
 1352: 			if (tp->t_state == TCPS_TIME_WAIT &&
 1353: 					(ticks - tp->t_starttime) > tcp_msl) {
 1354: 				rstreason = BANDLIM_UNLIMITED;
 1355: 				goto dropwithreset;
 1356: 			}
 1357: 			if (CC_GT(to.to_cc, tp->cc_recv)) {
 1358: 				tp = tcp_close(tp);
 1359: 				goto findpcb;
 1360: 			}
 1361: 			else
 1362: 				goto drop;
 1363: 		}
 1364:  		break;  /* continue normal processing */
 1365: 	}
 1366: 
 1367: 	/*
 1368: 	 * States other than LISTEN or SYN_SENT.
 1369: 	 * First check the RST flag and sequence number since reset segments
 1370: 	 * are exempt from the timestamp and connection count tests.  This
 1371: 	 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
 1372: 	 * below which allowed reset segments in half the sequence space
 1373: 	 * to fall though and be processed (which gives forged reset
 1374: 	 * segments with a random sequence number a 50 percent chance of
 1375: 	 * killing a connection).
 1376: 	 * Then check timestamp, if present.
 1377: 	 * Then check the connection count, if present.
 1378: 	 * Then check that at least some bytes of segment are within
 1379: 	 * receive window.  If segment begins before rcv_nxt,
 1380: 	 * drop leading data (and SYN); if nothing left, just ack.
 1381: 	 *
 1382: 	 *
 1383: 	 * If the RST bit is set, check the sequence number to see
 1384: 	 * if this is a valid reset segment.
 1385: 	 * RFC 793 page 37:
 1386: 	 *   In all states except SYN-SENT, all reset (RST) segments
 1387: 	 *   are validated by checking their SEQ-fields.  A reset is
 1388: 	 *   valid if its sequence number is in the window.
 1389: 	 * Note: this does not take into account delayed ACKs, so
 1390: 	 *   we should test against last_ack_sent instead of rcv_nxt.
 1391: 	 *   The sequence number in the reset segment is normally an
 1392: 	 *   echo of our outgoing acknowlegement numbers, but some hosts
 1393: 	 *   send a reset with the sequence number at the rightmost edge
 1394: 	 *   of our receive window, and we have to handle this case.
 1395: 	 * If we have multiple segments in flight, the intial reset
 1396: 	 * segment sequence numbers will be to the left of last_ack_sent,
 1397: 	 * but they will eventually catch up.
 1398: 	 * In any case, it never made sense to trim reset segments to
 1399: 	 * fit the receive window since RFC 1122 says:
 1400: 	 *   4.2.2.12  RST Segment: RFC-793 Section 3.4
 1401: 	 *
 1402: 	 *    A TCP SHOULD allow a received RST segment to include data.
 1403: 	 *
 1404: 	 *    DISCUSSION
 1405: 	 *         It has been suggested that a RST segment could contain
 1406: 	 *         ASCII text that encoded and explained the cause of the
 1407: 	 *         RST.  No standard has yet been established for such
 1408: 	 *         data.
 1409: 	 *
 1410: 	 * If the reset segment passes the sequence number test examine
 1411: 	 * the state:
 1412: 	 *    SYN_RECEIVED STATE:
 1413: 	 *	If passive open, return to LISTEN state.
 1414: 	 *	If active open, inform user that connection was refused.
 1415: 	 *    ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
 1416: 	 *	Inform user that connection was reset, and close tcb.
 1417: 	 *    CLOSING, LAST_ACK STATES:
 1418: 	 *	Close the tcb.
 1419: 	 *    TIME_WAIT STATE:
 1420: 	 *	Drop the segment - see Stevens, vol. 2, p. 964 and
 1421: 	 *      RFC 1337.
 1422: 	 */
 1423: 	if (thflags & TH_RST) {
 1424: 		if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
 1425: 		    SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
 1426: 			switch (tp->t_state) {
 1427: 
 1428: 			case TCPS_SYN_RECEIVED:
 1429: 				so->so_error = ECONNREFUSED;
 1430: 				goto close;
 1431: 
 1432: 			case TCPS_ESTABLISHED:
 1433: 			case TCPS_FIN_WAIT_1:
 1434: 			case TCPS_FIN_WAIT_2:
 1435: 			case TCPS_CLOSE_WAIT:
 1436: 				so->so_error = ECONNRESET;
 1437: 			close:
 1438: 				tp->t_state = TCPS_CLOSED;
 1439: 				tcpstat.tcps_drops++;
 1440: 				tp = tcp_close(tp);
 1441: 				break;
 1442: 
 1443: 			case TCPS_CLOSING:
 1444: 			case TCPS_LAST_ACK:
 1445: 				tp = tcp_close(tp);
 1446: 				break;
 1447: 
 1448: 			case TCPS_TIME_WAIT:
 1449: 				break;
 1450: 			}
 1451: 		}
 1452: 		goto drop;
 1453: 	}
 1454: 
 1455: 	/*
 1456: 	 * RFC 1323 PAWS: If we have a timestamp reply on this segment
 1457: 	 * and it's less than ts_recent, drop it.
 1458: 	 */
 1459: 	if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
 1460: 	    TSTMP_LT(to.to_tsval, tp->ts_recent)) {
 1461: 
 1462: 		/* Check to see if ts_recent is over 24 days old.  */
 1463: 		if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
 1464: 			/*
 1465: 			 * Invalidate ts_recent.  If this segment updates
 1466: 			 * ts_recent, the age will be reset later and ts_recent
 1467: 			 * will get a valid value.  If it does not, setting
 1468: 			 * ts_recent to zero will at least satisfy the
 1469: 			 * requirement that zero be placed in the timestamp
 1470: 			 * echo reply when ts_recent isn't valid.  The
 1471: 			 * age isn't reset until we get a valid ts_recent
 1472: 			 * because we don't want out-of-order segments to be
 1473: 			 * dropped when ts_recent is old.
 1474: 			 */
 1475: 			tp->ts_recent = 0;
 1476: 		} else {
 1477: 			tcpstat.tcps_rcvduppack++;
 1478: 			tcpstat.tcps_rcvdupbyte += tlen;
 1479: 			tcpstat.tcps_pawsdrop++;
 1480: 			if (tlen)
 1481: 				goto dropafterack;
 1482: 			goto drop;
 1483: 		}
 1484: 	}
 1485: 
 1486: 	/*
 1487: 	 * T/TCP mechanism
 1488: 	 *   If T/TCP was negotiated and the segment doesn't have CC,
 1489: 	 *   or if its CC is wrong then drop the segment.
 1490: 	 *   RST segments do not have to comply with this.
 1491: 	 */
 1492: 	if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
 1493: 	    ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc))
 1494:  		goto dropafterack;
 1495: 
 1496: 	/*
 1497: 	 * In the SYN-RECEIVED state, validate that the packet belongs to
 1498: 	 * this connection before trimming the data to fit the receive
 1499: 	 * window.  Check the sequence number versus IRS since we know
 1500: 	 * the sequence numbers haven't wrapped.  This is a partial fix
 1501: 	 * for the "LAND" DoS attack.
 1502: 	 */
 1503: 	if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
 1504: 		rstreason = BANDLIM_RST_OPENPORT;
 1505: 		goto dropwithreset;
 1506: 	}
 1507: 
 1508: 	todrop = tp->rcv_nxt - th->th_seq;
 1509: 	if (todrop > 0) {
 1510: 		if (thflags & TH_SYN) {
 1511: 			thflags &= ~TH_SYN;
 1512: 			th->th_seq++;
 1513: 			if (th->th_urp > 1)
 1514: 				th->th_urp--;
 1515: 			else
 1516: 				thflags &= ~TH_URG;
 1517: 			todrop--;
 1518: 		}
 1519: 		/*
 1520: 		 * Following if statement from Stevens, vol. 2, p. 960.
 1521: 		 */
 1522: 		if (todrop > tlen
 1523: 		    || (todrop == tlen && (thflags & TH_FIN) == 0)) {
 1524: 			/*
 1525: 			 * Any valid FIN must be to the left of the window.
 1526: 			 * At this point the FIN must be a duplicate or out
 1527: 			 * of sequence; drop it.
 1528: 			 */
 1529: 			thflags &= ~TH_FIN;
 1530: 
 1531: 			/*
 1532: 			 * Send an ACK to resynchronize and drop any data.
 1533: 			 * But keep on processing for RST or ACK.
 1534: 			 */
 1535: 			tp->t_flags |= TF_ACKNOW;
 1536: 			todrop = tlen;
 1537: 			tcpstat.tcps_rcvduppack++;
 1538: 			tcpstat.tcps_rcvdupbyte += todrop;
 1539: 		} else {
 1540: 			tcpstat.tcps_rcvpartduppack++;
 1541: 			tcpstat.tcps_rcvpartdupbyte += todrop;
 1542: 		}
 1543: 		drop_hdrlen += todrop;	/* drop from the top afterwards */
 1544: 		th->th_seq += todrop;
 1545: 		tlen -= todrop;
 1546: 		if (th->th_urp > todrop)
 1547: 			th->th_urp -= todrop;
 1548: 		else {
 1549: 			thflags &= ~TH_URG;
 1550: 			th->th_urp = 0;
 1551: 		}
 1552: 	}
 1553: 
 1554: 	/*
 1555: 	 * If new data are received on a connection after the
 1556: 	 * user processes are gone, then RST the other end.
 1557: 	 */
 1558: 	if ((so->so_state & SS_NOFDREF) &&
 1559: 	    tp->t_state > TCPS_CLOSE_WAIT && tlen) {
 1560: 		tp = tcp_close(tp);
 1561: 		tcpstat.tcps_rcvafterclose++;
 1562: 		rstreason = BANDLIM_UNLIMITED;
 1563: 		goto dropwithreset;
 1564: 	}
 1565: 
 1566: 	/*
 1567: 	 * If segment ends after window, drop trailing data
 1568: 	 * (and PUSH and FIN); if nothing left, just ACK.
 1569: 	 */
 1570: 	todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd);
 1571: 	if (todrop > 0) {
 1572: 		tcpstat.tcps_rcvpackafterwin++;
 1573: 		if (todrop >= tlen) {
 1574: 			tcpstat.tcps_rcvbyteafterwin += tlen;
 1575: 			/*
 1576: 			 * If a new connection request is received
 1577: 			 * while in TIME_WAIT, drop the old connection
 1578: 			 * and start over if the sequence numbers
 1579: 			 * are above the previous ones.
 1580: 			 */
 1581: 			if (thflags & TH_SYN &&
 1582: 			    tp->t_state == TCPS_TIME_WAIT &&
 1583: 			    SEQ_GT(th->th_seq, tp->rcv_nxt)) {
 1584: 				tp = tcp_close(tp);
 1585: 				goto findpcb;
 1586: 			}
 1587: 			/*
 1588: 			 * If window is closed can only take segments at
 1589: 			 * window edge, and have to drop data and PUSH from
 1590: 			 * incoming segments.  Continue processing, but
 1591: 			 * remember to ack.  Otherwise, drop segment
 1592: 			 * and ack.
 1593: 			 */
 1594: 			if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
 1595: 				tp->t_flags |= TF_ACKNOW;
 1596: 				tcpstat.tcps_rcvwinprobe++;
 1597: 			} else
 1598: 				goto dropafterack;
 1599: 		} else
 1600: 			tcpstat.tcps_rcvbyteafterwin += todrop;
 1601: 		m_adj(m, -todrop);
 1602: 		tlen -= todrop;
 1603: 		thflags &= ~(TH_PUSH|TH_FIN);
 1604: 	}
 1605: 
 1606: 	/*
 1607: 	 * If last ACK falls within this segment's sequence numbers,
 1608: 	 * record its timestamp.
 1609: 	 * NOTE that the test is modified according to the latest
 1610: 	 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
 1611: 	 */
 1612: 	if ((to.to_flags & TOF_TS) != 0 &&
 1613: 	    SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
 1614: 		tp->ts_recent_age = ticks;
 1615: 		tp->ts_recent = to.to_tsval;
 1616: 	}
 1617: 
 1618: 	/*
 1619: 	 * If a SYN is in the window, then this is an
 1620: 	 * error and we send an RST and drop the connection.
 1621: 	 */
 1622: 	if (thflags & TH_SYN) {
 1623: 		tp = tcp_drop(tp, ECONNRESET);
 1624: 		rstreason = BANDLIM_UNLIMITED;
 1625: 		goto dropwithreset;
 1626: 	}
 1627: 
 1628: 	/*
 1629: 	 * If the ACK bit is off:  if in SYN-RECEIVED state or SENDSYN
 1630: 	 * flag is on (half-synchronized state), then queue data for
 1631: 	 * later processing; else drop segment and return.
 1632: 	 */
 1633: 	if ((thflags & TH_ACK) == 0) {
 1634: 		if (tp->t_state == TCPS_SYN_RECEIVED ||
 1635: 		    (tp->t_flags & TF_NEEDSYN))
 1636: 			goto step6;
 1637: 		else
 1638: 			goto drop;
 1639: 	}
 1640: 
 1641: 	/*
 1642: 	 * Ack processing.
 1643: 	 */
 1644: 	switch (tp->t_state) {
 1645: 
 1646: 	/*
 1647: 	 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
 1648: 	 * ESTABLISHED state and continue processing.
 1649: 	 * The ACK was checked above.
 1650: 	 */
 1651: 	case TCPS_SYN_RECEIVED:
 1652: 
 1653: 		tcpstat.tcps_connects++;
 1654: 		soisconnected(so);
 1655: 		/* Do window scaling? */
 1656: 		if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
 1657: 			(TF_RCVD_SCALE|TF_REQ_SCALE)) {
 1658: 			tp->snd_scale = tp->requested_s_scale;
 1659: 			tp->rcv_scale = tp->request_r_scale;
 1660: 		}
 1661: 		/*
 1662: 		 * Upon successful completion of 3-way handshake,
 1663: 		 * update cache.CC if it was undefined, pass any queued
 1664: 		 * data to the user, and advance state appropriately.
 1665: 		 */
 1666: 		if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL &&
 1667: 		    taop->tao_cc == 0)
 1668: 			taop->tao_cc = tp->cc_recv;
 1669: 
 1670: 		/*
 1671: 		 * Make transitions:
 1672: 		 *      SYN-RECEIVED  -> ESTABLISHED
 1673: 		 *      SYN-RECEIVED* -> FIN-WAIT-1
 1674: 		 */
 1675: 		tp->t_starttime = ticks;
 1676: 		if (tp->t_flags & TF_NEEDFIN) {
 1677: 			tp->t_state = TCPS_FIN_WAIT_1;
 1678: 			tp->t_flags &= ~TF_NEEDFIN;
 1679: 		} else {
 1680: 			tp->t_state = TCPS_ESTABLISHED;
 1681: 			callout_reset(tp->tt_keep, tcp_keepidle, 
 1682: 				      tcp_timer_keep, tp);
 1683: 		}
 1684: 		/*
 1685: 		 * If segment contains data or ACK, will call tcp_reass()
 1686: 		 * later; if not, do so now to pass queued data to user.
 1687: 		 */
 1688: 		if (tlen == 0 && (thflags & TH_FIN) == 0)
 1689: 			(void) tcp_reass(tp, (struct tcphdr *)0, 0,
 1690: 			    (struct mbuf *)0);
 1691: 		tp->snd_wl1 = th->th_seq - 1;
 1692: 		/* fall into ... */
 1693: 
 1694: 	/*
 1695: 	 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
 1696: 	 * ACKs.  If the ack is in the range
 1697: 	 *	tp->snd_una < th->th_ack <= tp->snd_max
 1698: 	 * then advance tp->snd_una to th->th_ack and drop
 1699: 	 * data from the retransmission queue.  If this ACK reflects
 1700: 	 * more up to date window information we update our window information.
 1701: 	 */
 1702: 	case TCPS_ESTABLISHED:
 1703: 	case TCPS_FIN_WAIT_1:
 1704: 	case TCPS_FIN_WAIT_2:
 1705: 	case TCPS_CLOSE_WAIT:
 1706: 	case TCPS_CLOSING:
 1707: 	case TCPS_LAST_ACK:
 1708: 	case TCPS_TIME_WAIT:
 1709: 
 1710: 		if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
 1711: 			if (tlen == 0 && tiwin == tp->snd_wnd) {
 1712: 				tcpstat.tcps_rcvdupack++;
 1713: 				/*
 1714: 				 * If we have outstanding data (other than
 1715: 				 * a window probe), this is a completely
 1716: 				 * duplicate ack (ie, window info didn't
 1717: 				 * change), the ack is the biggest we've
 1718: 				 * seen and we've seen exactly our rexmt
 1719: 				 * threshhold of them, assume a packet
 1720: 				 * has been dropped and retransmit it.
 1721: 				 * Kludge snd_nxt & the congestion
 1722: 				 * window so we send only this one
 1723: 				 * packet.
 1724: 				 *
 1725: 				 * We know we're losing at the current
 1726: 				 * window size so do congestion avoidance
 1727: 				 * (set ssthresh to half the current window
 1728: 				 * and pull our congestion window back to
 1729: 				 * the new ssthresh).
 1730: 				 *
 1731: 				 * Dup acks mean that packets have left the
 1732: 				 * network (they're now cached at the receiver)
 1733: 				 * so bump cwnd by the amount in the receiver
 1734: 				 * to keep a constant cwnd packets in the
 1735: 				 * network.
 1736: 				 */
 1737: 				if (!callout_active(tp->tt_rexmt) ||
 1738: 				    th->th_ack != tp->snd_una)
 1739: 					tp->t_dupacks = 0;
 1740: 				else if (++tp->t_dupacks > tcprexmtthresh ||
 1741: 					 (tcp_do_newreno &&
 1742: 					  IN_FASTRECOVERY(tp))) {
 1743: 					tp->snd_cwnd += tp->t_maxseg;
 1744: 					(void) tcp_output(tp);
 1745: 					goto drop;
 1746: 				} else if (tp->t_dupacks == tcprexmtthresh) {
 1747: 					tcp_seq onxt;
 1748: 					u_int win;
 1749: 
 1750: 					if (tcp_do_newreno &&
 1751: 					    SEQ_LEQ(th->th_ack,
 1752: 					            tp->snd_recover)) {
 1753: 						tp->t_dupacks = 0;
 1754: 						break;
 1755: 					}
 1756: fastretransmit:
 1757: 					if (tcp_do_eifel_detect &&
 1758: 					    (tp->t_flags & TF_RCVD_TSTMP)) {
 1759: 						tcp_save_congestion_state(tp);
 1760: 						tp->t_flags |= TF_FASTREXMT;
 1761: 					}
 1762: 					win = min(tp->snd_wnd, tp->snd_cwnd) /
 1763: 					    2 / tp->t_maxseg;
 1764: 					if (win < 2)
 1765: 						win = 2;
 1766: 					tp->snd_ssthresh = win * tp->t_maxseg;
 1767: 					ENTER_FASTRECOVERY(tp);
 1768: 					tp->snd_recover = tp->snd_max;
 1769: 					callout_stop(tp->tt_rexmt);
 1770: 					tp->t_rtttime = 0;
 1771: 					onxt = tp->snd_nxt;
 1772: 					tp->snd_nxt = th->th_ack;
 1773: 					tp->snd_cwnd = tp->t_maxseg;
 1774: 					(void) tcp_output(tp);
 1775: 					++tcpstat.tcps_sndfastrexmit;
 1776: 					KASSERT(tp->snd_limited <= 2,
 1777: 					    ("tp->snd_limited too big"));
 1778: 					tp->snd_cwnd = tp->snd_ssthresh +
 1779: 					    (tp->t_maxseg *
 1780: 					     (tp->t_dupacks - tp->snd_limited));
 1781: 					if (SEQ_GT(onxt, tp->snd_nxt))
 1782: 						tp->snd_nxt = onxt;
 1783: 					goto drop;
 1784: 				} else if (tcp_do_limitedtransmit) {
 1785: 					u_long oldcwnd = tp->snd_cwnd;
 1786: 					tcp_seq oldsndmax = tp->snd_max;
 1787: 					/* outstanding data */
 1788: 					uint32_t ownd =
 1789: 					    tp->snd_max - tp->snd_una;
 1790: 					u_int sent;
 1791: 
 1792: #define	iceildiv(n, d)		(((n)+(d)-1) / (d))
 1793: 
 1794: 					KASSERT(tp->t_dupacks == 1 ||
 1795: 					    tp->t_dupacks == 2,
 1796: 					    ("dupacks not 1 or 2"));
 1797: 					if (tp->t_dupacks == 1)
 1798: 						tp->snd_limited = 0;
 1799: 					tp->snd_cwnd = ownd +
 1800: 					    (tp->t_dupacks - tp->snd_limited) *
 1801: 					    tp->t_maxseg;
 1802: 					(void) tcp_output(tp);
 1803: 					tp->snd_cwnd = oldcwnd;
 1804: 					sent = tp->snd_max - oldsndmax;
 1805: 					if (sent > tp->t_maxseg) {
 1806: 						KASSERT((tp->t_dupacks == 2 &&
 1807: 						    tp->snd_limited == 0) ||
 1808: 						   (sent == tp->t_maxseg + 1 &&
 1809: 						    tp->t_flags & TF_SENTFIN),
 1810: 						    ("sent too much"));
 1811: 						KASSERT(sent <=
 1812: 							tp->t_maxseg * 2,
 1813: 						    ("sent too many segments"));
 1814: 						tp->snd_limited = 2;
 1815: 						tcpstat.tcps_sndlimited += 2;
 1816: 					} else if (sent > 0) {
 1817: 						++tp->snd_limited;
 1818: 						++tcpstat.tcps_sndlimited;
 1819: 					} else if (tcp_do_early_retransmit &&
 1820: 					    (tcp_do_eifel_detect &&
 1821: 					     (tp->t_flags & TF_RCVD_TSTMP)) &&
 1822: 					    tcp_do_newreno &&
 1823: 					    tp->t_dupacks + 1 >=
 1824: 					      iceildiv(ownd, tp->t_maxseg)) {
 1825: 						++tcpstat.tcps_sndearlyrexmit;
 1826: 						tp->t_flags |= TF_EARLYREXMT;
 1827: 						goto fastretransmit;
 1828: 					}
 1829: 					goto drop;
 1830: 				}
 1831: 			} else
 1832: 				tp->t_dupacks = 0;
 1833: 			break;
 1834: 		}
 1835: 
 1836: 		KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
 1837: 
 1838: 		/*
 1839: 		 * If the congestion window was inflated to account
 1840: 		 * for the other side's cached packets, retract it.
 1841: 		 */
 1842: 		if (tcp_do_newreno) {
 1843: 			if (IN_FASTRECOVERY(tp)) {
 1844: 				if (SEQ_LT(th->th_ack, tp->snd_recover)) {
 1845: 					tcp_newreno_partial_ack(tp, th);
 1846: 				} else {
 1847: 					/*
 1848: 					 * Window inflation should have left us
 1849: 					 * with approximately snd_ssthresh
 1850: 					 * outstanding data.
 1851: 					 * But in case we would be inclined to
 1852: 					 * send a burst, better to do it via
 1853: 					 * the slow start mechanism.
 1854: 					 */
 1855: 					if (SEQ_GT(th->th_ack +
 1856: 							tp->snd_ssthresh,
 1857: 						   tp->snd_max))
 1858: 						tp->snd_cwnd = tp->snd_max -
 1859: 								th->th_ack +
 1860: 								tp->t_maxseg;
 1861: 					else
 1862: 						tp->snd_cwnd = tp->snd_ssthresh;
 1863: 				}
 1864: 			}
 1865:                 } else {
 1866:                         if (tp->t_dupacks >= tcprexmtthresh &&
 1867:                             tp->snd_cwnd > tp->snd_ssthresh)
 1868: 				tp->snd_cwnd = tp->snd_ssthresh;
 1869:                 }
 1870: 		tp->t_dupacks = 0;
 1871: 		if (SEQ_GT(th->th_ack, tp->snd_max)) {
 1872: 			tcpstat.tcps_rcvacktoomuch++;
 1873: 			goto dropafterack;
 1874: 		}
 1875: 		/*
 1876: 		 * If we reach this point, ACK is not a duplicate,
 1877: 		 *     i.e., it ACKs something we sent.
 1878: 		 */
 1879: 		if (tp->t_flags & TF_NEEDSYN) {
 1880: 			/*
 1881: 			 * T/TCP: Connection was half-synchronized, and our
 1882: 			 * SYN has been ACK'd (so connection is now fully
 1883: 			 * synchronized).  Go to non-starred state,
 1884: 			 * increment snd_una for ACK of SYN, and check if
 1885: 			 * we can do window scaling.
 1886: 			 */
 1887: 			tp->t_flags &= ~TF_NEEDSYN;
 1888: 			tp->snd_una++;
 1889: 			/* Do window scaling? */
 1890: 			if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
 1891: 				(TF_RCVD_SCALE|TF_REQ_SCALE)) {
 1892: 				tp->snd_scale = tp->requested_s_scale;
 1893: 				tp->rcv_scale = tp->request_r_scale;
 1894: 			}
 1895: 		}
 1896: 
 1897: process_ACK:
 1898: 		acked = th->th_ack - tp->snd_una;
 1899: 		tcpstat.tcps_rcvackpack++;
 1900: 		tcpstat.tcps_rcvackbyte += acked;
 1901: 
 1902: 		/*
 1903: 		 * If we just performed our first retransmit, and the ACK
 1904: 		 * arrives within our recovery window, then it was a mistake
 1905: 		 * to do the retransmit in the first place.  Recover our
 1906: 		 * original cwnd and ssthresh, and proceed to transmit where
 1907: 		 * we left off.
 1908: 		 */
 1909: 		if (tcp_do_eifel_detect && acked &&
 1910: 		    (to.to_flags & TOF_TS) && to.to_tsecr &&
 1911: 		    (tp->t_flags & TF_FIRSTACCACK)) {
 1912: 			/* Eifel detection applicable. */
 1913: 			if (to.to_tsecr < tp->t_rexmtTS) {
 1914: 				++tcpstat.tcps_eifeldetected;
 1915: 				tcp_revert_congestion_state(tp);
 1916: 				if (tp->t_rxtshift == 1 &&
 1917: 				    ticks >= tp->t_badrxtwin)
 1918: 					++tcpstat.tcps_rttcantdetect;
 1919: 			}
 1920: 		} else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
 1921: 			tcp_revert_congestion_state(tp);
 1922: 			++tcpstat.tcps_rttdetected;
 1923: 		}
 1924: 
 1925: 		/*
 1926: 		 * If we have a timestamp reply, update smoothed
 1927: 		 * round trip time.  If no timestamp is present but
 1928: 		 * transmit timer is running and timed sequence
 1929: 		 * number was acked, update smoothed round trip time.
 1930: 		 * Since we now have an rtt measurement, cancel the
 1931: 		 * timer backoff (cf., Phil Karn's retransmit alg.).
 1932: 		 * Recompute the initial retransmit timer.
 1933: 		 *
 1934: 		 * Some machines (certain windows boxes) send broken
 1935: 		 * timestamp replies during the SYN+ACK phase, ignore 
 1936: 		 * timestamps of 0.
 1937: 		 */
 1938: 		if ((to.to_flags & TOF_TS) != 0 &&
 1939: 		    to.to_tsecr) {
 1940: 			tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
 1941: 		} else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
 1942: 			tcp_xmit_timer(tp, ticks - tp->t_rtttime);
 1943: 		}
 1944: 		tcp_xmit_bandwidth_limit(tp, th->th_ack);
 1945: 
 1946: 		/*
 1947: 		 * If all outstanding data is acked, stop retransmit
 1948: 		 * timer and remember to restart (more output or persist).
 1949: 		 * If there is more data to be acked, restart retransmit
 1950: 		 * timer, using current (possibly backed-off) value.
 1951: 		 */
 1952: 		if (th->th_ack == tp->snd_max) {
 1953: 			callout_stop(tp->tt_rexmt);
 1954: 			needoutput = 1;
 1955: 		} else if (!callout_active(tp->tt_persist))
 1956: 			callout_reset(tp->tt_rexmt, tp->t_rxtcur,
 1957: 				      tcp_timer_rexmt, tp);
 1958: 
 1959: 		/*
 1960: 		 * If no data (only SYN) was ACK'd,
 1961: 		 *    skip rest of ACK processing.
 1962: 		 */
 1963: 		if (acked == 0)
 1964: 			goto step6;
 1965: 
 1966: 		/* Stop looking for an acceptable ACK since one was received. */
 1967: 		tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT);
 1968: 
 1969: 		/*
 1970: 		 * When new data is acked, open the congestion window.
 1971: 		 * If the window gives us less than ssthresh packets
 1972: 		 * in flight, open exponentially (maxseg per packet).
 1973: 		 * Otherwise open linearly: maxseg per window
 1974: 		 * (maxseg^2 / cwnd per packet).
 1975: 		 */
 1976: 		if (!tcp_do_newreno || !IN_FASTRECOVERY(tp)) {
 1977: 			u_int cw = tp->snd_cwnd;
 1978: 			u_int incr = tp->t_maxseg;
 1979: 			if (cw > tp->snd_ssthresh)
 1980: 				incr = incr * incr / cw;
 1981: 			tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
 1982: 		}
 1983: 		if (acked > so->so_snd.sb_cc) {
 1984: 			tp->snd_wnd -= so->so_snd.sb_cc;
 1985: 			sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
 1986: 			ourfinisacked = 1;
 1987: 		} else {
 1988: 			sbdrop(&so->so_snd, acked);
 1989: 			tp->snd_wnd -= acked;
 1990: 			ourfinisacked = 0;
 1991: 		}
 1992: 		sowwakeup(so);
 1993: 		/* detect una wraparound */
 1994: 		if (tcp_do_newreno && !IN_FASTRECOVERY(tp) &&
 1995: 		    SEQ_GT(tp->snd_una, tp->snd_recover) &&
 1996: 		    SEQ_LEQ(th->th_ack, tp->snd_recover))
 1997: 			tp->snd_recover = th->th_ack - 1;
 1998: 		if (tcp_do_newreno && IN_FASTRECOVERY(tp) &&
 1999: 		    SEQ_GEQ(th->th_ack, tp->snd_recover))
 2000: 			EXIT_FASTRECOVERY(tp);
 2001: 		tp->snd_una = th->th_ack;
 2002: 		if (SEQ_LT(tp->snd_nxt, tp->snd_una))
 2003: 			tp->snd_nxt = tp->snd_una;
 2004: 
 2005: 		switch (tp->t_state) {
 2006: 
 2007: 		/*
 2008: 		 * In FIN_WAIT_1 STATE in addition to the processing
 2009: 		 * for the ESTABLISHED state if our FIN is now acknowledged
 2010: 		 * then enter FIN_WAIT_2.
 2011: 		 */
 2012: 		case TCPS_FIN_WAIT_1:
 2013: 			if (ourfinisacked) {
 2014: 				/*
 2015: 				 * If we can't receive any more
 2016: 				 * data, then closing user can proceed.
 2017: 				 * Starting the timer is contrary to the
 2018: 				 * specification, but if we don't get a FIN
 2019: 				 * we'll hang forever.
 2020: 				 */
 2021: 				if (so->so_state & SS_CANTRCVMORE) {
 2022: 					soisdisconnected(so);
 2023: 					callout_reset(tp->tt_2msl, tcp_maxidle,
 2024: 						      tcp_timer_2msl, tp);
 2025: 				}
 2026: 				tp->t_state = TCPS_FIN_WAIT_2;
 2027: 			}
 2028: 			break;
 2029: 
 2030: 	 	/*
 2031: 		 * In CLOSING STATE in addition to the processing for
 2032: 		 * the ESTABLISHED state if the ACK acknowledges our FIN
 2033: 		 * then enter the TIME-WAIT state, otherwise ignore
 2034: 		 * the segment.
 2035: 		 */
 2036: 		case TCPS_CLOSING:
 2037: 			if (ourfinisacked) {
 2038: 				tp->t_state = TCPS_TIME_WAIT;
 2039: 				tcp_canceltimers(tp);
 2040: 				/* Shorten TIME_WAIT [RFC-1644, p.28] */
 2041: 				if (tp->cc_recv != 0 &&
 2042: 				    (ticks - tp->t_starttime) < tcp_msl)
 2043: 					callout_reset(tp->tt_2msl,
 2044: 						      tp->t_rxtcur *
 2045: 						      TCPTV_TWTRUNC,
 2046: 						      tcp_timer_2msl, tp);
 2047: 				else
 2048: 					callout_reset(tp->tt_2msl, 2 * tcp_msl,
 2049: 						      tcp_timer_2msl, tp);
 2050: 				soisdisconnected(so);
 2051: 			}
 2052: 			break;
 2053: 
 2054: 		/*
 2055: 		 * In LAST_ACK, we may still be waiting for data to drain
 2056: 		 * and/or to be acked, as well as for the ack of our FIN.
 2057: 		 * If our FIN is now acknowledged, delete the TCB,
 2058: 		 * enter the closed state and return.
 2059: 		 */
 2060: 		case TCPS_LAST_ACK:
 2061: 			if (ourfinisacked) {
 2062: 				tp = tcp_close(tp);
 2063: 				goto drop;
 2064: 			}
 2065: 			break;
 2066: 
 2067: 		/*
 2068: 		 * In TIME_WAIT state the only thing that should arrive
 2069: 		 * is a retransmission of the remote FIN.  Acknowledge
 2070: 		 * it and restart the finack timer.
 2071: 		 */
 2072: 		case TCPS_TIME_WAIT:
 2073: 			callout_reset(tp->tt_2msl, 2 * tcp_msl,
 2074: 				      tcp_timer_2msl, tp);
 2075: 			goto dropafterack;
 2076: 		}
 2077: 	}
 2078: 
 2079: step6:
 2080: 	/*
 2081: 	 * Update window information.
 2082: 	 * Don't look at window if no ACK: TAC's send garbage on first SYN.
 2083: 	 */
 2084: 	if ((thflags & TH_ACK) &&
 2085: 	    (SEQ_LT(tp->snd_wl1, th->th_seq) ||
 2086: 	    (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
 2087: 	     (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
 2088: 		/* keep track of pure window updates */
 2089: 		if (tlen == 0 &&
 2090: 		    tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
 2091: 			tcpstat.tcps_rcvwinupd++;
 2092: 		tp->snd_wnd = tiwin;
 2093: 		tp->snd_wl1 = th->th_seq;
 2094: 		tp->snd_wl2 = th->th_ack;
 2095: 		if (tp->snd_wnd > tp->max_sndwnd)
 2096: 			tp->max_sndwnd = tp->snd_wnd;
 2097: 		needoutput = 1;
 2098: 	}
 2099: 
 2100: 	/*
 2101: 	 * Process segments with URG.
 2102: 	 */
 2103: 	if ((thflags & TH_URG) && th->th_urp &&
 2104: 	    TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 2105: 		/*
 2106: 		 * This is a kludge, but if we receive and accept
 2107: 		 * random urgent pointers, we'll crash in
 2108: 		 * soreceive.  It's hard to imagine someone
 2109: 		 * actually wanting to send this much urgent data.
 2110: 		 */
 2111: 		if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
 2112: 			th->th_urp = 0;			/* XXX */
 2113: 			thflags &= ~TH_URG;		/* XXX */
 2114: 			goto dodata;			/* XXX */
 2115: 		}
 2116: 		/*
 2117: 		 * If this segment advances the known urgent pointer,
 2118: 		 * then mark the data stream.  This should not happen
 2119: 		 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
 2120: 		 * a FIN has been received from the remote side.
 2121: 		 * In these states we ignore the URG.
 2122: 		 *
 2123: 		 * According to RFC961 (Assigned Protocols),
 2124: 		 * the urgent pointer points to the last octet
 2125: 		 * of urgent data.  We continue, however,
 2126: 		 * to consider it to indicate the first octet
 2127: 		 * of data past the urgent section as the original
 2128: 		 * spec states (in one of two places).
 2129: 		 */
 2130: 		if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
 2131: 			tp->rcv_up = th->th_seq + th->th_urp;
 2132: 			so->so_oobmark = so->so_rcv.sb_cc +
 2133: 			    (tp->rcv_up - tp->rcv_nxt) - 1;
 2134: 			if (so->so_oobmark == 0)
 2135: 				so->so_state |= SS_RCVATMARK;
 2136: 			sohasoutofband(so);
 2137: 			tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
 2138: 		}
 2139: 		/*
 2140: 		 * Remove out of band data so doesn't get presented to user.
 2141: 		 * This can happen independent of advancing the URG pointer,
 2142: 		 * but if two URG's are pending at once, some out-of-band
 2143: 		 * data may creep in... ick.
 2144: 		 */
 2145: 		if (th->th_urp <= (u_long)tlen
 2146: #ifdef SO_OOBINLINE
 2147: 		     && (so->so_options & SO_OOBINLINE) == 0
 2148: #endif
 2149: 		     )
 2150: 			tcp_pulloutofband(so, th, m,
 2151: 				drop_hdrlen);	/* hdr drop is delayed */
 2152: 	} else {
 2153: 		/*
 2154: 		 * If no out of band data is expected,
 2155: 		 * pull receive urgent pointer along
 2156: 		 * with the receive window.
 2157: 		 */
 2158: 		if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
 2159: 			tp->rcv_up = tp->rcv_nxt;
 2160: 	}
 2161: dodata:							/* XXX */
 2162: 
 2163: 	/*
 2164: 	 * Process the segment text, merging it into the TCP sequencing queue,
 2165: 	 * and arranging for acknowledgment of receipt if necessary.
 2166: 	 * This process logically involves adjusting tp->rcv_wnd as data
 2167: 	 * is presented to the user (this happens in tcp_usrreq.c,
 2168: 	 * case PRU_RCVD).  If a FIN has already been received on this
 2169: 	 * connection then we just ignore the text.
 2170: 	 */
 2171: 	if ((tlen || (thflags & TH_FIN)) &&
 2172: 	    TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 2173: 		m_adj(m, drop_hdrlen);	/* delayed header drop */
 2174: 		/*
 2175: 		 * Insert segment which includes th into TCP reassembly queue
 2176: 		 * with control block tp.  Set thflags to whether reassembly now
 2177: 		 * includes a segment with FIN.  This handles the common case
 2178: 		 * inline (segment is the next to be received on an established
 2179: 		 * connection, and the queue is empty), avoiding linkage into
 2180: 		 * and removal from the queue and repetition of various
 2181: 		 * conversions.
 2182: 		 * Set DELACK for segments received in order, but ack
 2183: 		 * immediately when segments are out of order (so
 2184: 		 * fast retransmit can work).
 2185: 		 */
 2186: 		if (th->th_seq == tp->rcv_nxt &&
 2187: 		    LIST_EMPTY(&tp->t_segq) &&
 2188: 		    TCPS_HAVEESTABLISHED(tp->t_state)) {
 2189: 			if (DELAY_ACK(tp))
 2190: 				callout_reset(tp->tt_delack, tcp_delacktime,
 2191: 					      tcp_timer_delack, tp);
 2192: 			else
 2193: 				tp->t_flags |= TF_ACKNOW;
 2194: 			tp->rcv_nxt += tlen;
 2195: 			thflags = th->th_flags & TH_FIN;
 2196: 			tcpstat.tcps_rcvpack++;
 2197: 			tcpstat.tcps_rcvbyte += tlen;
 2198: 			ND6_HINT(tp);
 2199: 			if (so->so_state & SS_CANTRCVMORE)
 2200: 				m_freem(m);
 2201: 			else
 2202: 				sbappend(&so->so_rcv, m);
 2203: 			sorwakeup(so);
 2204: 		} else {
 2205: 			thflags = tcp_reass(tp, th, &tlen, m);
 2206: 			tp->t_flags |= TF_ACKNOW;
 2207: 		}
 2208: 
 2209: 		/*
 2210: 		 * Note the amount of data that peer has sent into
 2211: 		 * our window, in order to estimate the sender's
 2212: 		 * buffer size.
 2213: 		 */
 2214: 		len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
 2215: 	} else {
 2216: 		m_freem(m);
 2217: 		thflags &= ~TH_FIN;
 2218: 	}
 2219: 
 2220: 	/*
 2221: 	 * If FIN is received ACK the FIN and let the user know
 2222: 	 * that the connection is closing.
 2223: 	 */
 2224: 	if (thflags & TH_FIN) {
 2225: 		if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 2226: 			socantrcvmore(so);
 2227: 			/*
 2228: 			 * If connection is half-synchronized
 2229: 			 * (ie NEEDSYN flag on) then delay ACK,
 2230: 			 * so it may be piggybacked when SYN is sent.
 2231: 			 * Otherwise, since we received a FIN then no
 2232: 			 * more input can be expected, send ACK now.
 2233: 			 */
 2234: 			if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN))
 2235:                                 callout_reset(tp->tt_delack, tcp_delacktime,  
 2236:                                     tcp_timer_delack, tp);  
 2237: 			else
 2238: 				tp->t_flags |= TF_ACKNOW;
 2239: 			tp->rcv_nxt++;
 2240: 		}
 2241: 		switch (tp->t_state) {
 2242: 
 2243: 	 	/*
 2244: 		 * In SYN_RECEIVED and ESTABLISHED STATES
 2245: 		 * enter the CLOSE_WAIT state.
 2246: 		 */
 2247: 		case TCPS_SYN_RECEIVED:
 2248: 			tp->t_starttime = ticks;
 2249: 			/*FALLTHROUGH*/
 2250: 		case TCPS_ESTABLISHED:
 2251: 			tp->t_state = TCPS_CLOSE_WAIT;
 2252: 			break;
 2253: 
 2254: 	 	/*
 2255: 		 * If still in FIN_WAIT_1 STATE FIN has not been acked so
 2256: 		 * enter the CLOSING state.
 2257: 		 */
 2258: 		case TCPS_FIN_WAIT_1:
 2259: 			tp->t_state = TCPS_CLOSING;
 2260: 			break;
 2261: 
 2262: 	 	/*
 2263: 		 * In FIN_WAIT_2 state enter the TIME_WAIT state,
 2264: 		 * starting the time-wait timer, turning off the other
 2265: 		 * standard timers.
 2266: 		 */
 2267: 		case TCPS_FIN_WAIT_2:
 2268: 			tp->t_state = TCPS_TIME_WAIT;
 2269: 			tcp_canceltimers(tp);
 2270: 			/* Shorten TIME_WAIT [RFC-1644, p.28] */
 2271: 			if (tp->cc_recv != 0 &&
 2272: 			    (ticks - tp->t_starttime) < tcp_msl) {
 2273: 				callout_reset(tp->tt_2msl,
 2274: 					      tp->t_rxtcur * TCPTV_TWTRUNC,
 2275: 					      tcp_timer_2msl, tp);
 2276: 				/* For transaction client, force ACK now. */
 2277: 				tp->t_flags |= TF_ACKNOW;
 2278: 			}
 2279: 			else
 2280: 				callout_reset(tp->tt_2msl, 2 * tcp_msl,
 2281: 					      tcp_timer_2msl, tp);
 2282: 			soisdisconnected(so);
 2283: 			break;
 2284: 
 2285: 		/*
 2286: 		 * In TIME_WAIT state restart the 2 MSL time_wait timer.
 2287: 		 */
 2288: 		case TCPS_TIME_WAIT:
 2289: 			callout_reset(tp->tt_2msl, 2 * tcp_msl,
 2290: 				      tcp_timer_2msl, tp);
 2291: 			break;
 2292: 		}
 2293: 	}
 2294: #ifdef TCPDEBUG
 2295: 	if (so->so_options & SO_DEBUG)
 2296: 		tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
 2297: 			  &tcp_savetcp, 0);
 2298: #endif
 2299: 
 2300: 	/*
 2301: 	 * Return any desired output.
 2302: 	 */
 2303: 	if (needoutput || (tp->t_flags & TF_ACKNOW))
 2304: 		(void) tcp_output(tp);
 2305: 	return;
 2306: 
 2307: dropafterack:
 2308: 	/*
 2309: 	 * Generate an ACK dropping incoming segment if it occupies
 2310: 	 * sequence space, where the ACK reflects our state.
 2311: 	 *
 2312: 	 * We can now skip the test for the RST flag since all
 2313: 	 * paths to this code happen after packets containing
 2314: 	 * RST have been dropped.
 2315: 	 *
 2316: 	 * In the SYN-RECEIVED state, don't send an ACK unless the
 2317: 	 * segment we received passes the SYN-RECEIVED ACK test.
 2318: 	 * If it fails send a RST.  This breaks the loop in the
 2319: 	 * "LAND" DoS attack, and also prevents an ACK storm
 2320: 	 * between two listening ports that have been sent forged
 2321: 	 * SYN segments, each with the source address of the other.
 2322: 	 */
 2323: 	if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
 2324: 	    (SEQ_GT(tp->snd_una, th->th_ack) ||
 2325: 	     SEQ_GT(th->th_ack, tp->snd_max)) ) {
 2326: 		rstreason = BANDLIM_RST_OPENPORT;
 2327: 		goto dropwithreset;
 2328: 	}
 2329: #ifdef TCPDEBUG
 2330: 	if (so->so_options & SO_DEBUG)
 2331: 		tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
 2332: 			  &tcp_savetcp, 0);
 2333: #endif
 2334: 	m_freem(m);
 2335: 	tp->t_flags |= TF_ACKNOW;
 2336: 	(void) tcp_output(tp);
 2337: 	return;
 2338: 
 2339: dropwithreset:
 2340: 	/*
 2341: 	 * Generate a RST, dropping incoming segment.
 2342: 	 * Make ACK acceptable to originator of segment.
 2343: 	 * Don't bother to respond if destination was broadcast/multicast.
 2344: 	 */
 2345: 	if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
 2346: 		goto drop;
 2347: 	if (isipv6) {
 2348: 		if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 2349: 		    IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
 2350: 			goto drop;
 2351: 	} else {
 2352: 		if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
 2353: 		    IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
 2354: 	    	    ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
 2355: 	    	    in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
 2356: 			goto drop;
 2357: 	}
 2358: 	/* IPv6 anycast check is done at tcp6_input() */
 2359: 
 2360: 	/*
 2361: 	 * Perform bandwidth limiting.
 2362: 	 */
 2363: #ifdef ICMP_BANDLIM
 2364: 	if (badport_bandlim(rstreason) < 0)
 2365: 		goto drop;
 2366: #endif
 2367: 
 2368: #ifdef TCPDEBUG
 2369: 	if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 2370: 		tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
 2371: 			  &tcp_savetcp, 0);
 2372: #endif
 2373: 	if (thflags & TH_ACK)
 2374: 		/* mtod() below is safe as long as hdr dropping is delayed */
 2375: 		tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
 2376: 			    TH_RST);
 2377: 	else {
 2378: 		if (thflags & TH_SYN)
 2379: 			tlen++;
 2380: 		/* mtod() below is safe as long as hdr dropping is delayed */
 2381: 		tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
 2382: 			    (tcp_seq)0, TH_RST|TH_ACK);
 2383: 	}
 2384: 	return;
 2385: 
 2386: drop:
 2387: 	/*
 2388: 	 * Drop space held by incoming segment and return.
 2389: 	 */
 2390: #ifdef TCPDEBUG
 2391: 	if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 2392: 		tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
 2393: 			  &tcp_savetcp, 0);
 2394: #endif
 2395: 	m_freem(m);
 2396: 	return;
 2397: }
 2398: 
 2399: /*
 2400:  * Parse TCP options and place in tcpopt.
 2401:  */
 2402: static void
 2403: tcp_dooptions(to, cp, cnt, is_syn)
 2404: 	struct tcpopt *to;
 2405: 	u_char *cp;
 2406: 	int cnt;
 2407: {
 2408: 	int opt, optlen;
 2409: 
 2410: 	to->to_flags = 0;
 2411: 	for (; cnt > 0; cnt -= optlen, cp += optlen) {
 2412: 		opt = cp[0];
 2413: 		if (opt == TCPOPT_EOL)
 2414: 			break;
 2415: 		if (opt == TCPOPT_NOP)
 2416: 			optlen = 1;
 2417: 		else {
 2418: 			if (cnt < 2)
 2419: 				break;
 2420: 			optlen = cp[1];
 2421: 			if (optlen < 2 || optlen > cnt)
 2422: 				break;
 2423: 		}
 2424: 		switch (opt) {
 2425: 		case TCPOPT_MAXSEG:
 2426: 			if (optlen != TCPOLEN_MAXSEG)
 2427: 				continue;
 2428: 			if (!is_syn)
 2429: 				continue;
 2430: 			to->to_flags |= TOF_MSS;
 2431: 			bcopy((char *)cp + 2,
 2432: 			    (char *)&to->to_mss, sizeof(to->to_mss));
 2433: 			to->to_mss = ntohs(to->to_mss);
 2434: 			break;
 2435: 		case TCPOPT_WINDOW:
 2436: 			if (optlen != TCPOLEN_WINDOW)
 2437: 				continue;
 2438: 			if (! is_syn)
 2439: 				continue;
 2440: 			to->to_flags |= TOF_SCALE;
 2441: 			to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
 2442: 			break;
 2443: 		case TCPOPT_TIMESTAMP:
 2444: 			if (optlen != TCPOLEN_TIMESTAMP)
 2445: 				continue;
 2446: 			to->to_flags |= TOF_TS;
 2447: 			bcopy((char *)cp + 2,
 2448: 			    (char *)&to->to_tsval, sizeof(to->to_tsval));
 2449: 			to->to_tsval = ntohl(to->to_tsval);
 2450: 			bcopy((char *)cp + 6,
 2451: 			    (char *)&to->to_tsecr, sizeof(to->to_tsecr));
 2452: 			to->to_tsecr = ntohl(to->to_tsecr);
 2453: 			break;
 2454: 		case TCPOPT_CC:
 2455: 			if (optlen != TCPOLEN_CC)
 2456: 				continue;
 2457: 			to->to_flags |= TOF_CC;
 2458: 			bcopy((char *)cp + 2,
 2459: 			    (char *)&to->to_cc, sizeof(to->to_cc));
 2460: 			to->to_cc = ntohl(to->to_cc);
 2461: 			break;
 2462: 		case TCPOPT_CCNEW:
 2463: 			if (optlen != TCPOLEN_CC)
 2464: 				continue;
 2465: 			if (!is_syn)
 2466: 				continue;
 2467: 			to->to_flags |= TOF_CCNEW;
 2468: 			bcopy((char *)cp + 2,
 2469: 			    (char *)&to->to_cc, sizeof(to->to_cc));
 2470: 			to->to_cc = ntohl(to->to_cc);
 2471: 			break;
 2472: 		case TCPOPT_CCECHO:
 2473: 			if (optlen != TCPOLEN_CC)
 2474: 				continue;
 2475: 			if (!is_syn)
 2476: 				continue;
 2477: 			to->to_flags |= TOF_CCECHO;
 2478: 			bcopy((char *)cp + 2,
 2479: 			    (char *)&to->to_ccecho, sizeof(to->to_ccecho));
 2480: 			to->to_ccecho = ntohl(to->to_ccecho);
 2481: 			break;
 2482: 		default:
 2483: 			continue;
 2484: 		}
 2485: 	}
 2486: }
 2487: 
 2488: /*
 2489:  * Pull out of band byte out of a segment so
 2490:  * it doesn't appear in the user's data queue.
 2491:  * It is still reflected in the segment length for
 2492:  * sequencing purposes.
 2493:  */
 2494: static void
 2495: tcp_pulloutofband(so, th, m, off)
 2496: 	struct socket *so;
 2497: 	struct tcphdr *th;
 2498: 	struct mbuf *m;
 2499: 	int off;		/* delayed to be droped hdrlen */
 2500: {
 2501: 	int cnt = off + th->th_urp - 1;
 2502: 
 2503: 	while (cnt >= 0) {
 2504: 		if (m->m_len > cnt) {
 2505: 			char *cp = mtod(m, caddr_t) + cnt;
 2506: 			struct tcpcb *tp = sototcpcb(so);
 2507: 
 2508: 			tp->t_iobc = *cp;
 2509: 			tp->t_oobflags |= TCPOOB_HAVEDATA;
 2510: 			bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
 2511: 			m->m_len--;
 2512: 			if (m->m_flags & M_PKTHDR)
 2513: 				m->m_pkthdr.len--;
 2514: 			return;
 2515: 		}
 2516: 		cnt -= m->m_len;
 2517: 		m = m->m_next;
 2518: 		if (m == 0)
 2519: 			break;
 2520: 	}
 2521: 	panic("tcp_pulloutofband");
 2522: }
 2523: 
 2524: /*
 2525:  * Collect new round-trip time estimate
 2526:  * and update averages and current timeout.
 2527:  */
 2528: static void
 2529: tcp_xmit_timer(tp, rtt)
 2530: 	struct tcpcb *tp;
 2531: 	int rtt;
 2532: {
 2533: 	int delta;
 2534: 
 2535: 	tcpstat.tcps_rttupdated++;
 2536: 	tp->t_rttupdated++;
 2537: 	if (tp->t_srtt != 0) {
 2538: 		/*
 2539: 		 * srtt is stored as fixed point with 5 bits after the
 2540: 		 * binary point (i.e., scaled by 8).  The following magic
 2541: 		 * is equivalent to the smoothing algorithm in rfc793 with
 2542: 		 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
 2543: 		 * point).  Adjust rtt to origin 0.
 2544: 		 */
 2545: 		delta = ((rtt - 1) << TCP_DELTA_SHIFT)
 2546: 			- (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
 2547: 
 2548: 		if ((tp->t_srtt += delta) <= 0)
 2549: 			tp->t_srtt = 1;
 2550: 
 2551: 		/*
 2552: 		 * We accumulate a smoothed rtt variance (actually, a
 2553: 		 * smoothed mean difference), then set the retransmit
 2554: 		 * timer to smoothed rtt + 4 times the smoothed variance.
 2555: 		 * rttvar is stored as fixed point with 4 bits after the
 2556: 		 * binary point (scaled by 16).  The following is
 2557: 		 * equivalent to rfc793 smoothing with an alpha of .75
 2558: 		 * (rttvar = rttvar*3/4 + |delta| / 4).  This replaces
 2559: 		 * rfc793's wired-in beta.
 2560: 		 */
 2561: 		if (delta < 0)
 2562: 			delta = -delta;
 2563: 		delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
 2564: 		if ((tp->t_rttvar += delta) <= 0)
 2565: 			tp->t_rttvar = 1;
 2566: 		if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
 2567: 			tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
 2568: 	} else {
 2569: 		/*
 2570: 		 * No rtt measurement yet - use the unsmoothed rtt.
 2571: 		 * Set the variance to half the rtt (so our first
 2572: 		 * retransmit happens at 3*rtt).
 2573: 		 */
 2574: 		tp->t_srtt = rtt << TCP_RTT_SHIFT;
 2575: 		tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
 2576: 		tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
 2577: 	}
 2578: 	tp->t_rtttime = 0;
 2579: 	tp->t_rxtshift = 0;
 2580: 
 2581: 	/*
 2582: 	 * the retransmit should happen at rtt + 4 * rttvar.
 2583: 	 * Because of the way we do the smoothing, srtt and rttvar
 2584: 	 * will each average +1/2 tick of bias.  When we compute
 2585: 	 * the retransmit timer, we want 1/2 tick of rounding and
 2586: 	 * 1 extra tick because of +-1/2 tick uncertainty in the
 2587: 	 * firing of the timer.  The bias will give us exactly the
 2588: 	 * 1.5 tick we need.  But, because the bias is
 2589: 	 * statistical, we have to test that we don't drop below
 2590: 	 * the minimum feasible timer (which is 2 ticks).
 2591: 	 */
 2592: 	TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
 2593: 		      max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
 2594: 
 2595: 	/*
 2596: 	 * We received an ack for a packet that wasn't retransmitted;
 2597: 	 * it is probably safe to discard any error indications we've
 2598: 	 * received recently.  This isn't quite right, but close enough
 2599: 	 * for now (a route might have failed after we sent a segment,
 2600: 	 * and the return path might not be symmetrical).
 2601: 	 */
 2602: 	tp->t_softerror = 0;
 2603: }
 2604: 
 2605: /*
 2606:  * Determine a reasonable value for maxseg size.
 2607:  * If the route is known, check route for mtu.
 2608:  * If none, use an mss that can be handled on the outgoing
 2609:  * interface without forcing IP to fragment; if bigger than
 2610:  * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
 2611:  * to utilize large mbufs.  If no route is found, route has no mtu,
 2612:  * or the destination isn't local, use a default, hopefully conservative
 2613:  * size (usually 512 or the default IP max size, but no more than the mtu
 2614:  * of the interface), as we can't discover anything about intervening
 2615:  * gateways or networks.  We also initialize the congestion/slow start
 2616:  * window to be a single segment if the destination isn't local.
 2617:  * While looking at the routing entry, we also initialize other path-dependent
 2618:  * parameters from pre-set or cached values in the routing entry.
 2619:  *
 2620:  * Also take into account the space needed for options that we
 2621:  * send regularly.  Make maxseg shorter by that amount to assure
 2622:  * that we can send maxseg amount of data even when the options
 2623:  * are present.  Store the upper limit of the length of options plus
 2624:  * data in maxopd.
 2625:  *
 2626:  * NOTE that this routine is only called when we process an incoming
 2627:  * segment, for outgoing segments only tcp_mssopt is called.
 2628:  *
 2629:  * In case of T/TCP, we call this routine during implicit connection
 2630:  * setup as well (offer = -1), to initialize maxseg from the cached
 2631:  * MSS of our peer.
 2632:  */
 2633: void
 2634: tcp_mss(tp, offer)
 2635: 	struct tcpcb *tp;
 2636: 	int offer;
 2637: {
 2638: 	struct rtentry *rt;
 2639: 	struct ifnet *ifp;
 2640: 	int rtt, mss;
 2641: 	u_long bufsize;
 2642: 	struct inpcb *inp = tp->t_inpcb;
 2643: 	struct socket *so;
 2644: 	struct rmxp_tao *taop;
 2645: 	int origoffer = offer;
 2646: #ifdef INET6
 2647: 	int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
 2648: 	size_t min_protoh = isipv6 ?
 2649: 			    sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
 2650: 			    sizeof(struct tcpiphdr);
 2651: #else
 2652: 	const int isipv6 = 0;
 2653: 	const size_t min_protoh = sizeof(struct tcpiphdr);
 2654: #endif
 2655: 
 2656: 	if (isipv6)
 2657: 		rt = tcp_rtlookup6(&inp->inp_inc);
 2658: 	else
 2659: 		rt = tcp_rtlookup(&inp->inp_inc);
 2660: 	if (rt == NULL) {
 2661: 		tp->t_maxopd = tp->t_maxseg =
 2662: 				isipv6 ? tcp_v6mssdflt : tcp_mssdflt;
 2663: 		return;
 2664: 	}
 2665: 	ifp = rt->rt_ifp;
 2666: 	so = inp->inp_socket;
 2667: 
 2668: 	taop = rmx_taop(rt->rt_rmx);
 2669: 	/*
 2670: 	 * Offer == -1 means that we didn't receive SYN yet,
 2671: 	 * use cached value in that case;
 2672: 	 */
 2673: 	if (offer == -1)
 2674: 		offer = taop->tao_mssopt;
 2675: 	/*
 2676: 	 * Offer == 0 means that there was no MSS on the SYN segment,
 2677: 	 * in this case we use tcp_mssdflt.
 2678: 	 */
 2679: 	if (offer == 0)
 2680: 		offer = isipv6 ? tcp_v6mssdflt : tcp_mssdflt;
 2681: 	else
 2682: 		/*
 2683: 		 * Sanity check: make sure that maxopd will be large
 2684: 		 * enough to allow some data on segments even is the
 2685: 		 * all the option space is used (40bytes).  Otherwise
 2686: 		 * funny things may happen in tcp_output.
 2687: 		 */
 2688: 		offer = max(offer, 64);
 2689: 	taop->tao_mssopt = offer;
 2690: 
 2691: 	/*
 2692: 	 * While we're here, check if there's an initial rtt
 2693: 	 * or rttvar.  Convert from the route-table units
 2694: 	 * to scaled multiples of the slow timeout timer.
 2695: 	 */
 2696: 	if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
 2697: 		/*
 2698: 		 * XXX the lock bit for RTT indicates that the value
 2699: 		 * is also a minimum value; this is subject to time.
 2700: 		 */
 2701: 		if (rt->rt_rmx.rmx_locks & RTV_RTT)
 2702: 			tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
 2703: 		tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
 2704: 		tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
 2705: 		tcpstat.tcps_usedrtt++;
 2706: 		if (rt->rt_rmx.rmx_rttvar) {
 2707: 			tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
 2708: 			    (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
 2709: 			tcpstat.tcps_usedrttvar++;
 2710: 		} else {
 2711: 			/* default variation is +- 1 rtt */
 2712: 			tp->t_rttvar =
 2713: 			    tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
 2714: 		}
 2715: 		TCPT_RANGESET(tp->t_rxtcur,
 2716: 			      ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
 2717: 			      tp->t_rttmin, TCPTV_REXMTMAX);
 2718: 	}
 2719: 	/*
 2720: 	 * if there's an mtu associated with the route, use it
 2721: 	 * else, use the link mtu.
 2722: 	 */
 2723: 	if (rt->rt_rmx.rmx_mtu)
 2724: 		mss = rt->rt_rmx.rmx_mtu - min_protoh;
 2725: 	else {
 2726: 		if (isipv6) {
 2727: 			mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu -
 2728: 				min_protoh;
 2729: 			if (!in6_localaddr(&inp->in6p_faddr))
 2730: 				mss = min(mss, tcp_v6mssdflt);
 2731: 		} else {
 2732: 			mss = ifp->if_mtu - min_protoh;
 2733: 			if (!in_localaddr(inp->inp_faddr))
 2734: 				mss = min(mss, tcp_mssdflt);
 2735: 		}
 2736: 	}
 2737: 	mss = min(mss, offer);
 2738: 	/*
 2739: 	 * maxopd stores the maximum length of data AND options
 2740: 	 * in a segment; maxseg is the amount of data in a normal
 2741: 	 * segment.  We need to store this value (maxopd) apart
 2742: 	 * from maxseg, because now every segment carries options
 2743: 	 * and thus we normally have somewhat less data in segments.
 2744: 	 */
 2745: 	tp->t_maxopd = mss;
 2746: 
 2747: 	/*
 2748: 	 * In case of T/TCP, origoffer==-1 indicates, that no segments
 2749: 	 * were received yet.  In this case we just guess, otherwise
 2750: 	 * we do the same as before T/TCP.
 2751: 	 */
 2752:  	if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
 2753: 	    (origoffer == -1 ||
 2754: 	     (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
 2755: 		mss -= TCPOLEN_TSTAMP_APPA;
 2756:  	if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
 2757: 	    (origoffer == -1 ||
 2758: 	     (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
 2759: 		mss -= TCPOLEN_CC_APPA;
 2760: 
 2761: #if	(MCLBYTES & (MCLBYTES - 1)) == 0
 2762: 		if (mss > MCLBYTES)
 2763: 			mss &= ~(MCLBYTES-1);
 2764: #else
 2765: 		if (mss > MCLBYTES)
 2766: 			mss = mss / MCLBYTES * MCLBYTES;
 2767: #endif
 2768: 	/*
 2769: 	 * If there's a pipesize, change the socket buffer
 2770: 	 * to that size.  Make the socket buffers an integral
 2771: 	 * number of mss units; if the mss is larger than
 2772: 	 * the socket buffer, decrease the mss.
 2773: 	 */
 2774: #ifdef RTV_SPIPE
 2775: 	if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
 2776: #endif
 2777: 		bufsize = so->so_snd.sb_hiwat;
 2778: 	if (bufsize < mss)
 2779: 		mss = bufsize;
 2780: 	else {
 2781: 		bufsize = roundup(bufsize, mss);
 2782: 		if (bufsize > sb_max)
 2783: 			bufsize = sb_max;
 2784: 		if (bufsize > so->so_snd.sb_hiwat)
 2785: 			(void)sbreserve(&so->so_snd, bufsize, so, NULL);
 2786: 	}
 2787: 	tp->t_maxseg = mss;
 2788: 
 2789: #ifdef RTV_RPIPE
 2790: 	if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
 2791: #endif
 2792: 		bufsize = so->so_rcv.sb_hiwat;
 2793: 	if (bufsize > mss) {
 2794: 		bufsize = roundup(bufsize, mss);
 2795: 		if (bufsize > sb_max)
 2796: 			bufsize = sb_max;
 2797: 		if (bufsize > so->so_rcv.sb_hiwat)
 2798: 			(void)sbreserve(&so->so_rcv, bufsize, so, NULL);
 2799: 	}
 2800: 
 2801: 	/*
 2802: 	 * Set the slow-start flight size depending on whether this
 2803: 	 * is a local network or not.
 2804: 	 */
 2805: 	if (tcp_do_rfc3390)
 2806: 		tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
 2807: 	else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
 2808: 		 (!isipv6 && in_localaddr(inp->inp_faddr)))
 2809: 		tp->snd_cwnd = mss * ss_fltsz_local;
 2810: 	else
 2811: 		tp->snd_cwnd = mss * ss_fltsz;
 2812: 
 2813: 	if (rt->rt_rmx.rmx_ssthresh) {
 2814: 		/*
 2815: 		 * There's some sort of gateway or interface
 2816: 		 * buffer limit on the path.  Use this to set
 2817: 		 * the slow start threshhold, but set the
 2818: 		 * threshold to no less than 2*mss.
 2819: 		 */
 2820: 		tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
 2821: 		tcpstat.tcps_usedssthresh++;
 2822: 	}
 2823: }
 2824: 
 2825: /*
 2826:  * Determine the MSS option to send on an outgoing SYN.
 2827:  */
 2828: int
 2829: tcp_mssopt(tp)
 2830: 	struct tcpcb *tp;
 2831: {
 2832: 	struct rtentry *rt;
 2833: #ifdef INET6
 2834: 	int isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
 2835: 	int min_protoh = isipv6 ?
 2836: 			     sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
 2837: 			     sizeof(struct tcpiphdr);
 2838: #else
 2839: 	const int isipv6 = 0;
 2840: 	const size_t min_protoh = sizeof(struct tcpiphdr);
 2841: #endif
 2842: 
 2843: 	if (isipv6)
 2844: 		rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
 2845: 	else
 2846: 		rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
 2847: 	if (rt == NULL)
 2848: 		return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
 2849: 
 2850: 	return (rt->rt_ifp->if_mtu - min_protoh);
 2851: }
 2852: 
 2853: 
 2854: /*
 2855:  * When a partial ack arrives, force the retransmission of the
 2856:  * next unacknowledged segment.  Do not clear tp->t_dupacks.
 2857:  * By setting snd_nxt to ti_ack, this forces retransmission timer to
 2858:  * be started again.
 2859:  */
 2860: static void
 2861: tcp_newreno_partial_ack(tp, th)
 2862: 	struct tcpcb *tp;
 2863: 	struct tcphdr *th;
 2864: {
 2865: 	tcp_seq onxt = tp->snd_nxt;
 2866: 	u_long  ocwnd = tp->snd_cwnd;
 2867: 
 2868: 	callout_stop(tp->tt_rexmt);
 2869: 	tp->t_rtttime = 0;
 2870: 	tp->snd_nxt = th->th_ack;
 2871: 	/*
 2872: 	 * Set snd_cwnd to one segment beyond acknowledged offset
 2873: 	 * (tp->snd_una has not yet been updated when this function is called.)
 2874: 	 */
 2875: 	tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una);
 2876: 	tp->t_flags |= TF_ACKNOW;
 2877: 	(void) tcp_output(tp);
 2878: 	tp->snd_cwnd = ocwnd;
 2879: 	if (SEQ_GT(onxt, tp->snd_nxt))
 2880: 		tp->snd_nxt = onxt;
 2881: 	/*
 2882: 	 * Partial window deflation.  Relies on fact that tp->snd_una
 2883: 	 * not updated yet.
 2884: 	 */
 2885: 	tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
 2886: }