File:  [Qemu by Fabrice Bellard] / qemu / slirp / tcp_input.c
Revision 1.1.1.4 (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 16:54:51 2018 UTC (3 years ago) by root
Branches: qemu, MAIN
CVS tags: qemu0105, qemu0104, qemu0103, qemu0102, qemu0101, qemu0100, HEAD
qemu 0.10.0

    1: /*
    2:  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994
    3:  *	The Regents of the University of California.  All rights reserved.
    4:  *
    5:  * Redistribution and use in source and binary forms, with or without
    6:  * modification, are permitted provided that the following conditions
    7:  * are met:
    8:  * 1. Redistributions of source code must retain the above copyright
    9:  *    notice, this list of conditions and the following disclaimer.
   10:  * 2. Redistributions in binary form must reproduce the above copyright
   11:  *    notice, this list of conditions and the following disclaimer in the
   12:  *    documentation and/or other materials provided with the distribution.
   13:  * 3. Neither the name of the University nor the names of its contributors
   14:  *    may be used to endorse or promote products derived from this software
   15:  *    without specific prior written permission.
   16:  *
   17:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27:  * SUCH DAMAGE.
   28:  *
   29:  *	@(#)tcp_input.c	8.5 (Berkeley) 4/10/94
   30:  * tcp_input.c,v 1.10 1994/10/13 18:36:32 wollman Exp
   31:  */
   32: 
   33: /*
   34:  * Changes and additions relating to SLiRP
   35:  * Copyright (c) 1995 Danny Gasparovski.
   36:  *
   37:  * Please read the file COPYRIGHT for the
   38:  * terms and conditions of the copyright.
   39:  */
   40: 
   41: #include <slirp.h>
   42: #include "ip_icmp.h"
   43: 
   44: struct socket tcb;
   45: 
   46: #define	TCPREXMTTHRESH 3
   47: struct	socket *tcp_last_so = &tcb;
   48: 
   49: tcp_seq tcp_iss;                /* tcp initial send seq # */
   50: 
   51: #define TCP_PAWS_IDLE	(24 * 24 * 60 * 60 * PR_SLOWHZ)
   52: 
   53: /* for modulo comparisons of timestamps */
   54: #define TSTMP_LT(a,b)	((int)((a)-(b)) < 0)
   55: #define TSTMP_GEQ(a,b)	((int)((a)-(b)) >= 0)
   56: 
   57: /*
   58:  * Insert segment ti into reassembly queue of tcp with
   59:  * control block tp.  Return TH_FIN if reassembly now includes
   60:  * a segment with FIN.  The macro form does the common case inline
   61:  * (segment is the next to be received on an established connection,
   62:  * and the queue is empty), avoiding linkage into and removal
   63:  * from the queue and repetition of various conversions.
   64:  * Set DELACK for segments received in order, but ack immediately
   65:  * when segments are out of order (so fast retransmit can work).
   66:  */
   67: #ifdef TCP_ACK_HACK
   68: #define TCP_REASS(tp, ti, m, so, flags) {\
   69:        if ((ti)->ti_seq == (tp)->rcv_nxt && \
   70:            tcpfrag_list_empty(tp) && \
   71:            (tp)->t_state == TCPS_ESTABLISHED) {\
   72:                if (ti->ti_flags & TH_PUSH) \
   73:                        tp->t_flags |= TF_ACKNOW; \
   74:                else \
   75:                        tp->t_flags |= TF_DELACK; \
   76:                (tp)->rcv_nxt += (ti)->ti_len; \
   77:                flags = (ti)->ti_flags & TH_FIN; \
   78:                STAT(tcpstat.tcps_rcvpack++);         \
   79:                STAT(tcpstat.tcps_rcvbyte += (ti)->ti_len);   \
   80:                if (so->so_emu) { \
   81: 		       if (tcp_emu((so),(m))) sbappend((so), (m)); \
   82: 	       } else \
   83: 	       	       sbappend((so), (m)); \
   84: /*               sorwakeup(so); */ \
   85: 	} else {\
   86:                (flags) = tcp_reass((tp), (ti), (m)); \
   87:                tp->t_flags |= TF_ACKNOW; \
   88:        } \
   89: }
   90: #else
   91: #define	TCP_REASS(tp, ti, m, so, flags) { \
   92: 	if ((ti)->ti_seq == (tp)->rcv_nxt && \
   93:         tcpfrag_list_empty(tp) && \
   94: 	    (tp)->t_state == TCPS_ESTABLISHED) { \
   95: 		tp->t_flags |= TF_DELACK; \
   96: 		(tp)->rcv_nxt += (ti)->ti_len; \
   97: 		flags = (ti)->ti_flags & TH_FIN; \
   98: 		STAT(tcpstat.tcps_rcvpack++);        \
   99: 		STAT(tcpstat.tcps_rcvbyte += (ti)->ti_len);  \
  100: 		if (so->so_emu) { \
  101: 			if (tcp_emu((so),(m))) sbappend(so, (m)); \
  102: 		} else \
  103: 			sbappend((so), (m)); \
  104: /*		sorwakeup(so); */ \
  105: 	} else { \
  106: 		(flags) = tcp_reass((tp), (ti), (m)); \
  107: 		tp->t_flags |= TF_ACKNOW; \
  108: 	} \
  109: }
  110: #endif
  111: static void tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt,
  112:                           struct tcpiphdr *ti);
  113: static void tcp_xmit_timer(register struct tcpcb *tp, int rtt);
  114: 
  115: static int
  116: tcp_reass(register struct tcpcb *tp, register struct tcpiphdr *ti,
  117:           struct mbuf *m)
  118: {
  119: 	register struct tcpiphdr *q;
  120: 	struct socket *so = tp->t_socket;
  121: 	int flags;
  122: 
  123: 	/*
  124: 	 * Call with ti==0 after become established to
  125: 	 * force pre-ESTABLISHED data up to user socket.
  126: 	 */
  127: 	if (ti == 0)
  128: 		goto present;
  129: 
  130: 	/*
  131: 	 * Find a segment which begins after this one does.
  132: 	 */
  133: 	for (q = tcpfrag_list_first(tp); !tcpfrag_list_end(q, tp);
  134:             q = tcpiphdr_next(q))
  135: 		if (SEQ_GT(q->ti_seq, ti->ti_seq))
  136: 			break;
  137: 
  138: 	/*
  139: 	 * If there is a preceding segment, it may provide some of
  140: 	 * our data already.  If so, drop the data from the incoming
  141: 	 * segment.  If it provides all of our data, drop us.
  142: 	 */
  143: 	if (!tcpfrag_list_end(tcpiphdr_prev(q), tp)) {
  144: 		register int i;
  145: 		q = tcpiphdr_prev(q);
  146: 		/* conversion to int (in i) handles seq wraparound */
  147: 		i = q->ti_seq + q->ti_len - ti->ti_seq;
  148: 		if (i > 0) {
  149: 			if (i >= ti->ti_len) {
  150: 				STAT(tcpstat.tcps_rcvduppack++);
  151: 				STAT(tcpstat.tcps_rcvdupbyte += ti->ti_len);
  152: 				m_freem(m);
  153: 				/*
  154: 				 * Try to present any queued data
  155: 				 * at the left window edge to the user.
  156: 				 * This is needed after the 3-WHS
  157: 				 * completes.
  158: 				 */
  159: 				goto present;   /* ??? */
  160: 			}
  161: 			m_adj(m, i);
  162: 			ti->ti_len -= i;
  163: 			ti->ti_seq += i;
  164: 		}
  165: 		q = tcpiphdr_next(q);
  166: 	}
  167: 	STAT(tcpstat.tcps_rcvoopack++);
  168: 	STAT(tcpstat.tcps_rcvoobyte += ti->ti_len);
  169: 	ti->ti_mbuf = m;
  170: 
  171: 	/*
  172: 	 * While we overlap succeeding segments trim them or,
  173: 	 * if they are completely covered, dequeue them.
  174: 	 */
  175: 	while (!tcpfrag_list_end(q, tp)) {
  176: 		register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq;
  177: 		if (i <= 0)
  178: 			break;
  179: 		if (i < q->ti_len) {
  180: 			q->ti_seq += i;
  181: 			q->ti_len -= i;
  182: 			m_adj(q->ti_mbuf, i);
  183: 			break;
  184: 		}
  185: 		q = tcpiphdr_next(q);
  186: 		m = tcpiphdr_prev(q)->ti_mbuf;
  187: 		remque(tcpiphdr2qlink(tcpiphdr_prev(q)));
  188: 		m_freem(m);
  189: 	}
  190: 
  191: 	/*
  192: 	 * Stick new segment in its place.
  193: 	 */
  194: 	insque(tcpiphdr2qlink(ti), tcpiphdr2qlink(tcpiphdr_prev(q)));
  195: 
  196: present:
  197: 	/*
  198: 	 * Present data to user, advancing rcv_nxt through
  199: 	 * completed sequence space.
  200: 	 */
  201: 	if (!TCPS_HAVEESTABLISHED(tp->t_state))
  202: 		return (0);
  203: 	ti = tcpfrag_list_first(tp);
  204: 	if (tcpfrag_list_end(ti, tp) || ti->ti_seq != tp->rcv_nxt)
  205: 		return (0);
  206: 	if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len)
  207: 		return (0);
  208: 	do {
  209: 		tp->rcv_nxt += ti->ti_len;
  210: 		flags = ti->ti_flags & TH_FIN;
  211: 		remque(tcpiphdr2qlink(ti));
  212: 		m = ti->ti_mbuf;
  213: 		ti = tcpiphdr_next(ti);
  214: /*		if (so->so_state & SS_FCANTRCVMORE) */
  215: 		if (so->so_state & SS_FCANTSENDMORE)
  216: 			m_freem(m);
  217: 		else {
  218: 			if (so->so_emu) {
  219: 				if (tcp_emu(so,m)) sbappend(so, m);
  220: 			} else
  221: 				sbappend(so, m);
  222: 		}
  223: 	} while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt);
  224: /*	sorwakeup(so); */
  225: 	return (flags);
  226: }
  227: 
  228: /*
  229:  * TCP input routine, follows pages 65-76 of the
  230:  * protocol specification dated September, 1981 very closely.
  231:  */
  232: void
  233: tcp_input(m, iphlen, inso)
  234: 	register struct mbuf *m;
  235: 	int iphlen;
  236: 	struct socket *inso;
  237: {
  238:   	struct ip save_ip, *ip;
  239: 	register struct tcpiphdr *ti;
  240: 	caddr_t optp = NULL;
  241: 	int optlen = 0;
  242: 	int len, tlen, off;
  243: 	register struct tcpcb *tp = 0;
  244: 	register int tiflags;
  245: 	struct socket *so = 0;
  246: 	int todrop, acked, ourfinisacked, needoutput = 0;
  247: /*	int dropsocket = 0; */
  248: 	int iss = 0;
  249: 	u_long tiwin;
  250: 	int ret;
  251: /*	int ts_present = 0; */
  252:     struct ex_list *ex_ptr;
  253: 
  254: 	DEBUG_CALL("tcp_input");
  255: 	DEBUG_ARGS((dfd," m = %8lx  iphlen = %2d  inso = %lx\n",
  256: 		    (long )m, iphlen, (long )inso ));
  257: 
  258: 	/*
  259: 	 * If called with m == 0, then we're continuing the connect
  260: 	 */
  261: 	if (m == NULL) {
  262: 		so = inso;
  263: 
  264: 		/* Re-set a few variables */
  265: 		tp = sototcpcb(so);
  266: 		m = so->so_m;
  267: 		so->so_m = 0;
  268: 		ti = so->so_ti;
  269: 		tiwin = ti->ti_win;
  270: 		tiflags = ti->ti_flags;
  271: 
  272: 		goto cont_conn;
  273: 	}
  274: 
  275: 
  276: 	STAT(tcpstat.tcps_rcvtotal++);
  277: 	/*
  278: 	 * Get IP and TCP header together in first mbuf.
  279: 	 * Note: IP leaves IP header in first mbuf.
  280: 	 */
  281: 	ti = mtod(m, struct tcpiphdr *);
  282: 	if (iphlen > sizeof(struct ip )) {
  283: 	  ip_stripoptions(m, (struct mbuf *)0);
  284: 	  iphlen=sizeof(struct ip );
  285: 	}
  286: 	/* XXX Check if too short */
  287: 
  288: 
  289: 	/*
  290: 	 * Save a copy of the IP header in case we want restore it
  291: 	 * for sending an ICMP error message in response.
  292: 	 */
  293: 	ip=mtod(m, struct ip *);
  294: 	save_ip = *ip;
  295: 	save_ip.ip_len+= iphlen;
  296: 
  297: 	/*
  298: 	 * Checksum extended TCP header and data.
  299: 	 */
  300: 	tlen = ((struct ip *)ti)->ip_len;
  301: 	tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = 0;
  302:     memset(&ti->ti_i.ih_mbuf, 0 , sizeof(struct mbuf_ptr));
  303: 	ti->ti_x1 = 0;
  304: 	ti->ti_len = htons((u_int16_t)tlen);
  305: 	len = sizeof(struct ip ) + tlen;
  306: 	/* keep checksum for ICMP reply
  307: 	 * ti->ti_sum = cksum(m, len);
  308: 	 * if (ti->ti_sum) { */
  309: 	if(cksum(m, len)) {
  310: 	  STAT(tcpstat.tcps_rcvbadsum++);
  311: 	  goto drop;
  312: 	}
  313: 
  314: 	/*
  315: 	 * Check that TCP offset makes sense,
  316: 	 * pull out TCP options and adjust length.		XXX
  317: 	 */
  318: 	off = ti->ti_off << 2;
  319: 	if (off < sizeof (struct tcphdr) || off > tlen) {
  320: 	  STAT(tcpstat.tcps_rcvbadoff++);
  321: 	  goto drop;
  322: 	}
  323: 	tlen -= off;
  324: 	ti->ti_len = tlen;
  325: 	if (off > sizeof (struct tcphdr)) {
  326: 	  optlen = off - sizeof (struct tcphdr);
  327: 	  optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr);
  328: 
  329: 		/*
  330: 		 * Do quick retrieval of timestamp options ("options
  331: 		 * prediction?").  If timestamp is the only option and it's
  332: 		 * formatted as recommended in RFC 1323 appendix A, we
  333: 		 * quickly get the values now and not bother calling
  334: 		 * tcp_dooptions(), etc.
  335: 		 */
  336: /*		if ((optlen == TCPOLEN_TSTAMP_APPA ||
  337:  *		     (optlen > TCPOLEN_TSTAMP_APPA &&
  338:  *			optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) &&
  339:  *		     *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) &&
  340:  *		     (ti->ti_flags & TH_SYN) == 0) {
  341:  *			ts_present = 1;
  342:  *			ts_val = ntohl(*(u_int32_t *)(optp + 4));
  343:  *			ts_ecr = ntohl(*(u_int32_t *)(optp + 8));
  344:  *			optp = NULL;   / * we've parsed the options * /
  345:  *		}
  346:  */
  347: 	}
  348: 	tiflags = ti->ti_flags;
  349: 
  350: 	/*
  351: 	 * Convert TCP protocol specific fields to host format.
  352: 	 */
  353: 	NTOHL(ti->ti_seq);
  354: 	NTOHL(ti->ti_ack);
  355: 	NTOHS(ti->ti_win);
  356: 	NTOHS(ti->ti_urp);
  357: 
  358: 	/*
  359: 	 * Drop TCP, IP headers and TCP options.
  360: 	 */
  361: 	m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
  362: 	m->m_len  -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
  363: 
  364:     if (slirp_restrict) {
  365:         for (ex_ptr = exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next)
  366:             if (ex_ptr->ex_fport == ti->ti_dport &&
  367:                     (ntohl(ti->ti_dst.s_addr) & 0xff) == ex_ptr->ex_addr)
  368:                 break;
  369: 
  370:         if (!ex_ptr)
  371:             goto drop;
  372:     }
  373: 	/*
  374: 	 * Locate pcb for segment.
  375: 	 */
  376: findso:
  377: 	so = tcp_last_so;
  378: 	if (so->so_fport != ti->ti_dport ||
  379: 	    so->so_lport != ti->ti_sport ||
  380: 	    so->so_laddr.s_addr != ti->ti_src.s_addr ||
  381: 	    so->so_faddr.s_addr != ti->ti_dst.s_addr) {
  382: 		so = solookup(&tcb, ti->ti_src, ti->ti_sport,
  383: 			       ti->ti_dst, ti->ti_dport);
  384: 		if (so)
  385: 			tcp_last_so = so;
  386: 		STAT(tcpstat.tcps_socachemiss++);
  387: 	}
  388: 
  389: 	/*
  390: 	 * If the state is CLOSED (i.e., TCB does not exist) then
  391: 	 * all data in the incoming segment is discarded.
  392: 	 * If the TCB exists but is in CLOSED state, it is embryonic,
  393: 	 * but should either do a listen or a connect soon.
  394: 	 *
  395: 	 * state == CLOSED means we've done socreate() but haven't
  396: 	 * attached it to a protocol yet...
  397: 	 *
  398: 	 * XXX If a TCB does not exist, and the TH_SYN flag is
  399: 	 * the only flag set, then create a session, mark it
  400: 	 * as if it was LISTENING, and continue...
  401: 	 */
  402: 	if (so == 0) {
  403: 	  if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN)
  404: 	    goto dropwithreset;
  405: 
  406: 	  if ((so = socreate()) == NULL)
  407: 	    goto dropwithreset;
  408: 	  if (tcp_attach(so) < 0) {
  409: 	    free(so); /* Not sofree (if it failed, it's not insqued) */
  410: 	    goto dropwithreset;
  411: 	  }
  412: 
  413: 	  sbreserve(&so->so_snd, TCP_SNDSPACE);
  414: 	  sbreserve(&so->so_rcv, TCP_RCVSPACE);
  415: 
  416: 	  /*		tcp_last_so = so; */  /* XXX ? */
  417: 	  /*		tp = sototcpcb(so);    */
  418: 
  419: 	  so->so_laddr = ti->ti_src;
  420: 	  so->so_lport = ti->ti_sport;
  421: 	  so->so_faddr = ti->ti_dst;
  422: 	  so->so_fport = ti->ti_dport;
  423: 
  424: 	  if ((so->so_iptos = tcp_tos(so)) == 0)
  425: 	    so->so_iptos = ((struct ip *)ti)->ip_tos;
  426: 
  427: 	  tp = sototcpcb(so);
  428: 	  tp->t_state = TCPS_LISTEN;
  429: 	}
  430: 
  431:         /*
  432:          * If this is a still-connecting socket, this probably
  433:          * a retransmit of the SYN.  Whether it's a retransmit SYN
  434: 	 * or something else, we nuke it.
  435:          */
  436:         if (so->so_state & SS_ISFCONNECTING)
  437:                 goto drop;
  438: 
  439: 	tp = sototcpcb(so);
  440: 
  441: 	/* XXX Should never fail */
  442: 	if (tp == 0)
  443: 		goto dropwithreset;
  444: 	if (tp->t_state == TCPS_CLOSED)
  445: 		goto drop;
  446: 
  447: 	/* Unscale the window into a 32-bit value. */
  448: /*	if ((tiflags & TH_SYN) == 0)
  449:  *		tiwin = ti->ti_win << tp->snd_scale;
  450:  *	else
  451:  */
  452: 		tiwin = ti->ti_win;
  453: 
  454: 	/*
  455: 	 * Segment received on connection.
  456: 	 * Reset idle time and keep-alive timer.
  457: 	 */
  458: 	tp->t_idle = 0;
  459: 	if (SO_OPTIONS)
  460: 	   tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
  461: 	else
  462: 	   tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
  463: 
  464: 	/*
  465: 	 * Process options if not in LISTEN state,
  466: 	 * else do it below (after getting remote address).
  467: 	 */
  468: 	if (optp && tp->t_state != TCPS_LISTEN)
  469: 		tcp_dooptions(tp, (u_char *)optp, optlen, ti);
  470: /* , */
  471: /*			&ts_present, &ts_val, &ts_ecr); */
  472: 
  473: 	/*
  474: 	 * Header prediction: check for the two common cases
  475: 	 * of a uni-directional data xfer.  If the packet has
  476: 	 * no control flags, is in-sequence, the window didn't
  477: 	 * change and we're not retransmitting, it's a
  478: 	 * candidate.  If the length is zero and the ack moved
  479: 	 * forward, we're the sender side of the xfer.  Just
  480: 	 * free the data acked & wake any higher level process
  481: 	 * that was blocked waiting for space.  If the length
  482: 	 * is non-zero and the ack didn't move, we're the
  483: 	 * receiver side.  If we're getting packets in-order
  484: 	 * (the reassembly queue is empty), add the data to
  485: 	 * the socket buffer and note that we need a delayed ack.
  486: 	 *
  487: 	 * XXX Some of these tests are not needed
  488: 	 * eg: the tiwin == tp->snd_wnd prevents many more
  489: 	 * predictions.. with no *real* advantage..
  490: 	 */
  491: 	if (tp->t_state == TCPS_ESTABLISHED &&
  492: 	    (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
  493: /*	    (!ts_present || TSTMP_GEQ(ts_val, tp->ts_recent)) && */
  494: 	    ti->ti_seq == tp->rcv_nxt &&
  495: 	    tiwin && tiwin == tp->snd_wnd &&
  496: 	    tp->snd_nxt == tp->snd_max) {
  497: 		/*
  498: 		 * If last ACK falls within this segment's sequence numbers,
  499: 		 *  record the timestamp.
  500: 		 */
  501: /*		if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
  502:  *		   SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) {
  503:  *			tp->ts_recent_age = tcp_now;
  504:  *			tp->ts_recent = ts_val;
  505:  *		}
  506:  */
  507: 		if (ti->ti_len == 0) {
  508: 			if (SEQ_GT(ti->ti_ack, tp->snd_una) &&
  509: 			    SEQ_LEQ(ti->ti_ack, tp->snd_max) &&
  510: 			    tp->snd_cwnd >= tp->snd_wnd) {
  511: 				/*
  512: 				 * this is a pure ack for outstanding data.
  513: 				 */
  514: 				STAT(tcpstat.tcps_predack++);
  515: /*				if (ts_present)
  516:  *					tcp_xmit_timer(tp, tcp_now-ts_ecr+1);
  517:  *				else
  518:  */				     if (tp->t_rtt &&
  519: 					    SEQ_GT(ti->ti_ack, tp->t_rtseq))
  520: 					tcp_xmit_timer(tp, tp->t_rtt);
  521: 				acked = ti->ti_ack - tp->snd_una;
  522: 				STAT(tcpstat.tcps_rcvackpack++);
  523: 				STAT(tcpstat.tcps_rcvackbyte += acked);
  524: 				sbdrop(&so->so_snd, acked);
  525: 				tp->snd_una = ti->ti_ack;
  526: 				m_freem(m);
  527: 
  528: 				/*
  529: 				 * If all outstanding data are acked, stop
  530: 				 * retransmit timer, otherwise restart timer
  531: 				 * using current (possibly backed-off) value.
  532: 				 * If process is waiting for space,
  533: 				 * wakeup/selwakeup/signal.  If data
  534: 				 * are ready to send, let tcp_output
  535: 				 * decide between more output or persist.
  536: 				 */
  537: 				if (tp->snd_una == tp->snd_max)
  538: 					tp->t_timer[TCPT_REXMT] = 0;
  539: 				else if (tp->t_timer[TCPT_PERSIST] == 0)
  540: 					tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
  541: 
  542: 				/*
  543: 				 * There's room in so_snd, sowwakup will read()
  544: 				 * from the socket if we can
  545: 				 */
  546: /*				if (so->so_snd.sb_flags & SB_NOTIFY)
  547:  *					sowwakeup(so);
  548:  */
  549: 				/*
  550: 				 * This is called because sowwakeup might have
  551: 				 * put data into so_snd.  Since we don't so sowwakeup,
  552: 				 * we don't need this.. XXX???
  553: 				 */
  554: 				if (so->so_snd.sb_cc)
  555: 					(void) tcp_output(tp);
  556: 
  557: 				return;
  558: 			}
  559: 		} else if (ti->ti_ack == tp->snd_una &&
  560: 		    tcpfrag_list_empty(tp) &&
  561: 		    ti->ti_len <= sbspace(&so->so_rcv)) {
  562: 			/*
  563: 			 * this is a pure, in-sequence data packet
  564: 			 * with nothing on the reassembly queue and
  565: 			 * we have enough buffer space to take it.
  566: 			 */
  567: 			STAT(tcpstat.tcps_preddat++);
  568: 			tp->rcv_nxt += ti->ti_len;
  569: 			STAT(tcpstat.tcps_rcvpack++);
  570: 			STAT(tcpstat.tcps_rcvbyte += ti->ti_len);
  571: 			/*
  572: 			 * Add data to socket buffer.
  573: 			 */
  574: 			if (so->so_emu) {
  575: 				if (tcp_emu(so,m)) sbappend(so, m);
  576: 			} else
  577: 				sbappend(so, m);
  578: 
  579: 			/*
  580: 			 * XXX This is called when data arrives.  Later, check
  581: 			 * if we can actually write() to the socket
  582: 			 * XXX Need to check? It's be NON_BLOCKING
  583: 			 */
  584: /*			sorwakeup(so); */
  585: 
  586: 			/*
  587: 			 * If this is a short packet, then ACK now - with Nagel
  588: 			 *	congestion avoidance sender won't send more until
  589: 			 *	he gets an ACK.
  590: 			 *
  591: 			 * It is better to not delay acks at all to maximize
  592: 			 * TCP throughput.  See RFC 2581.
  593: 			 */
  594: 			tp->t_flags |= TF_ACKNOW;
  595: 			tcp_output(tp);
  596: 			return;
  597: 		}
  598: 	} /* header prediction */
  599: 	/*
  600: 	 * Calculate amount of space in receive window,
  601: 	 * and then do TCP input processing.
  602: 	 * Receive window is amount of space in rcv queue,
  603: 	 * but not less than advertised window.
  604: 	 */
  605: 	{ int win;
  606:           win = sbspace(&so->so_rcv);
  607: 	  if (win < 0)
  608: 	    win = 0;
  609: 	  tp->rcv_wnd = max(win, (int)(tp->rcv_adv - tp->rcv_nxt));
  610: 	}
  611: 
  612: 	switch (tp->t_state) {
  613: 
  614: 	/*
  615: 	 * If the state is LISTEN then ignore segment if it contains an RST.
  616: 	 * If the segment contains an ACK then it is bad and send a RST.
  617: 	 * If it does not contain a SYN then it is not interesting; drop it.
  618: 	 * Don't bother responding if the destination was a broadcast.
  619: 	 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
  620: 	 * tp->iss, and send a segment:
  621: 	 *     <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
  622: 	 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
  623: 	 * Fill in remote peer address fields if not previously specified.
  624: 	 * Enter SYN_RECEIVED state, and process any other fields of this
  625: 	 * segment in this state.
  626: 	 */
  627: 	case TCPS_LISTEN: {
  628: 
  629: 	  if (tiflags & TH_RST)
  630: 	    goto drop;
  631: 	  if (tiflags & TH_ACK)
  632: 	    goto dropwithreset;
  633: 	  if ((tiflags & TH_SYN) == 0)
  634: 	    goto drop;
  635: 
  636: 	  /*
  637: 	   * This has way too many gotos...
  638: 	   * But a bit of spaghetti code never hurt anybody :)
  639: 	   */
  640: 
  641: 	  /*
  642: 	   * If this is destined for the control address, then flag to
  643: 	   * tcp_ctl once connected, otherwise connect
  644: 	   */
  645: 	  if ((so->so_faddr.s_addr&htonl(0xffffff00)) == special_addr.s_addr) {
  646: 	    int lastbyte=ntohl(so->so_faddr.s_addr) & 0xff;
  647: 	    if (lastbyte!=CTL_ALIAS && lastbyte!=CTL_DNS) {
  648: #if 0
  649: 	      if(lastbyte==CTL_CMD || lastbyte==CTL_EXEC) {
  650: 		/* Command or exec adress */
  651: 		so->so_state |= SS_CTL;
  652: 	      } else
  653: #endif
  654:               {
  655: 		/* May be an add exec */
  656: 		for(ex_ptr = exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
  657: 		  if(ex_ptr->ex_fport == so->so_fport &&
  658: 		     lastbyte == ex_ptr->ex_addr) {
  659: 		    so->so_state |= SS_CTL;
  660: 		    break;
  661: 		  }
  662: 		}
  663: 	      }
  664: 	      if(so->so_state & SS_CTL) goto cont_input;
  665: 	    }
  666: 	    /* CTL_ALIAS: Do nothing, tcp_fconnect will be called on it */
  667: 	  }
  668: 
  669: 	  if (so->so_emu & EMU_NOCONNECT) {
  670: 	    so->so_emu &= ~EMU_NOCONNECT;
  671: 	    goto cont_input;
  672: 	  }
  673: 
  674: 	  if((tcp_fconnect(so) == -1) && (errno != EINPROGRESS) && (errno != EWOULDBLOCK)) {
  675: 	    u_char code=ICMP_UNREACH_NET;
  676: 	    DEBUG_MISC((dfd," tcp fconnect errno = %d-%s\n",
  677: 			errno,strerror(errno)));
  678: 	    if(errno == ECONNREFUSED) {
  679: 	      /* ACK the SYN, send RST to refuse the connection */
  680: 	      tcp_respond(tp, ti, m, ti->ti_seq+1, (tcp_seq)0,
  681: 			  TH_RST|TH_ACK);
  682: 	    } else {
  683: 	      if(errno == EHOSTUNREACH) code=ICMP_UNREACH_HOST;
  684: 	      HTONL(ti->ti_seq);             /* restore tcp header */
  685: 	      HTONL(ti->ti_ack);
  686: 	      HTONS(ti->ti_win);
  687: 	      HTONS(ti->ti_urp);
  688: 	      m->m_data -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
  689: 	      m->m_len  += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
  690: 	      *ip=save_ip;
  691: 	      icmp_error(m, ICMP_UNREACH,code, 0,strerror(errno));
  692: 	    }
  693: 	    tp = tcp_close(tp);
  694: 	    m_free(m);
  695: 	  } else {
  696: 	    /*
  697: 	     * Haven't connected yet, save the current mbuf
  698: 	     * and ti, and return
  699: 	     * XXX Some OS's don't tell us whether the connect()
  700: 	     * succeeded or not.  So we must time it out.
  701: 	     */
  702: 	    so->so_m = m;
  703: 	    so->so_ti = ti;
  704: 	    tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
  705: 	    tp->t_state = TCPS_SYN_RECEIVED;
  706: 	  }
  707: 	  return;
  708: 
  709: 	cont_conn:
  710: 	  /* m==NULL
  711: 	   * Check if the connect succeeded
  712: 	   */
  713: 	  if (so->so_state & SS_NOFDREF) {
  714: 	    tp = tcp_close(tp);
  715: 	    goto dropwithreset;
  716: 	  }
  717: 	cont_input:
  718: 	  tcp_template(tp);
  719: 
  720: 	  if (optp)
  721: 	    tcp_dooptions(tp, (u_char *)optp, optlen, ti);
  722: 	  /* , */
  723: 	  /*				&ts_present, &ts_val, &ts_ecr); */
  724: 
  725: 	  if (iss)
  726: 	    tp->iss = iss;
  727: 	  else
  728: 	    tp->iss = tcp_iss;
  729: 	  tcp_iss += TCP_ISSINCR/2;
  730: 	  tp->irs = ti->ti_seq;
  731: 	  tcp_sendseqinit(tp);
  732: 	  tcp_rcvseqinit(tp);
  733: 	  tp->t_flags |= TF_ACKNOW;
  734: 	  tp->t_state = TCPS_SYN_RECEIVED;
  735: 	  tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
  736: 	  STAT(tcpstat.tcps_accepts++);
  737: 	  goto trimthenstep6;
  738: 	} /* case TCPS_LISTEN */
  739: 
  740: 	/*
  741: 	 * If the state is SYN_SENT:
  742: 	 *	if seg contains an ACK, but not for our SYN, drop the input.
  743: 	 *	if seg contains a RST, then drop the connection.
  744: 	 *	if seg does not contain SYN, then drop it.
  745: 	 * Otherwise this is an acceptable SYN segment
  746: 	 *	initialize tp->rcv_nxt and tp->irs
  747: 	 *	if seg contains ack then advance tp->snd_una
  748: 	 *	if SYN has been acked change to ESTABLISHED else SYN_RCVD state
  749: 	 *	arrange for segment to be acked (eventually)
  750: 	 *	continue processing rest of data/controls, beginning with URG
  751: 	 */
  752: 	case TCPS_SYN_SENT:
  753: 		if ((tiflags & TH_ACK) &&
  754: 		    (SEQ_LEQ(ti->ti_ack, tp->iss) ||
  755: 		     SEQ_GT(ti->ti_ack, tp->snd_max)))
  756: 			goto dropwithreset;
  757: 
  758: 		if (tiflags & TH_RST) {
  759: 			if (tiflags & TH_ACK)
  760: 				tp = tcp_drop(tp,0); /* XXX Check t_softerror! */
  761: 			goto drop;
  762: 		}
  763: 
  764: 		if ((tiflags & TH_SYN) == 0)
  765: 			goto drop;
  766: 		if (tiflags & TH_ACK) {
  767: 			tp->snd_una = ti->ti_ack;
  768: 			if (SEQ_LT(tp->snd_nxt, tp->snd_una))
  769: 				tp->snd_nxt = tp->snd_una;
  770: 		}
  771: 
  772: 		tp->t_timer[TCPT_REXMT] = 0;
  773: 		tp->irs = ti->ti_seq;
  774: 		tcp_rcvseqinit(tp);
  775: 		tp->t_flags |= TF_ACKNOW;
  776: 		if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) {
  777: 			STAT(tcpstat.tcps_connects++);
  778: 			soisfconnected(so);
  779: 			tp->t_state = TCPS_ESTABLISHED;
  780: 
  781: 			/* Do window scaling on this connection? */
  782: /*			if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
  783:  *				(TF_RCVD_SCALE|TF_REQ_SCALE)) {
  784:  * 				tp->snd_scale = tp->requested_s_scale;
  785:  *				tp->rcv_scale = tp->request_r_scale;
  786:  *			}
  787:  */
  788: 			(void) tcp_reass(tp, (struct tcpiphdr *)0,
  789: 				(struct mbuf *)0);
  790: 			/*
  791: 			 * if we didn't have to retransmit the SYN,
  792: 			 * use its rtt as our initial srtt & rtt var.
  793: 			 */
  794: 			if (tp->t_rtt)
  795: 				tcp_xmit_timer(tp, tp->t_rtt);
  796: 		} else
  797: 			tp->t_state = TCPS_SYN_RECEIVED;
  798: 
  799: trimthenstep6:
  800: 		/*
  801: 		 * Advance ti->ti_seq to correspond to first data byte.
  802: 		 * If data, trim to stay within window,
  803: 		 * dropping FIN if necessary.
  804: 		 */
  805: 		ti->ti_seq++;
  806: 		if (ti->ti_len > tp->rcv_wnd) {
  807: 			todrop = ti->ti_len - tp->rcv_wnd;
  808: 			m_adj(m, -todrop);
  809: 			ti->ti_len = tp->rcv_wnd;
  810: 			tiflags &= ~TH_FIN;
  811: 			STAT(tcpstat.tcps_rcvpackafterwin++);
  812: 			STAT(tcpstat.tcps_rcvbyteafterwin += todrop);
  813: 		}
  814: 		tp->snd_wl1 = ti->ti_seq - 1;
  815: 		tp->rcv_up = ti->ti_seq;
  816: 		goto step6;
  817: 	} /* switch tp->t_state */
  818: 	/*
  819: 	 * States other than LISTEN or SYN_SENT.
  820: 	 * First check timestamp, if present.
  821: 	 * Then check that at least some bytes of segment are within
  822: 	 * receive window.  If segment begins before rcv_nxt,
  823: 	 * drop leading data (and SYN); if nothing left, just ack.
  824: 	 *
  825: 	 * RFC 1323 PAWS: If we have a timestamp reply on this segment
  826: 	 * and it's less than ts_recent, drop it.
  827: 	 */
  828: /*	if (ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent &&
  829:  *	    TSTMP_LT(ts_val, tp->ts_recent)) {
  830:  *
  831:  */		/* Check to see if ts_recent is over 24 days old.  */
  832: /*		if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) {
  833:  */			/*
  834:  *			 * Invalidate ts_recent.  If this segment updates
  835:  *			 * ts_recent, the age will be reset later and ts_recent
  836:  *			 * will get a valid value.  If it does not, setting
  837:  *			 * ts_recent to zero will at least satisfy the
  838:  *			 * requirement that zero be placed in the timestamp
  839:  *			 * echo reply when ts_recent isn't valid.  The
  840:  *			 * age isn't reset until we get a valid ts_recent
  841:  *			 * because we don't want out-of-order segments to be
  842:  *			 * dropped when ts_recent is old.
  843:  *			 */
  844: /*			tp->ts_recent = 0;
  845:  *		} else {
  846:  *			tcpstat.tcps_rcvduppack++;
  847:  *			tcpstat.tcps_rcvdupbyte += ti->ti_len;
  848:  *			tcpstat.tcps_pawsdrop++;
  849:  *			goto dropafterack;
  850:  *		}
  851:  *	}
  852:  */
  853: 
  854: 	todrop = tp->rcv_nxt - ti->ti_seq;
  855: 	if (todrop > 0) {
  856: 		if (tiflags & TH_SYN) {
  857: 			tiflags &= ~TH_SYN;
  858: 			ti->ti_seq++;
  859: 			if (ti->ti_urp > 1)
  860: 				ti->ti_urp--;
  861: 			else
  862: 				tiflags &= ~TH_URG;
  863: 			todrop--;
  864: 		}
  865: 		/*
  866: 		 * Following if statement from Stevens, vol. 2, p. 960.
  867: 		 */
  868: 		if (todrop > ti->ti_len
  869: 		    || (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) {
  870: 			/*
  871: 			 * Any valid FIN must be to the left of the window.
  872: 			 * At this point the FIN must be a duplicate or out
  873: 			 * of sequence; drop it.
  874: 			 */
  875: 			tiflags &= ~TH_FIN;
  876: 
  877: 			/*
  878: 			 * Send an ACK to resynchronize and drop any data.
  879: 			 * But keep on processing for RST or ACK.
  880: 			 */
  881: 			tp->t_flags |= TF_ACKNOW;
  882: 			todrop = ti->ti_len;
  883: 			STAT(tcpstat.tcps_rcvduppack++);
  884: 			STAT(tcpstat.tcps_rcvdupbyte += todrop);
  885: 		} else {
  886: 			STAT(tcpstat.tcps_rcvpartduppack++);
  887: 			STAT(tcpstat.tcps_rcvpartdupbyte += todrop);
  888: 		}
  889: 		m_adj(m, todrop);
  890: 		ti->ti_seq += todrop;
  891: 		ti->ti_len -= todrop;
  892: 		if (ti->ti_urp > todrop)
  893: 			ti->ti_urp -= todrop;
  894: 		else {
  895: 			tiflags &= ~TH_URG;
  896: 			ti->ti_urp = 0;
  897: 		}
  898: 	}
  899: 	/*
  900: 	 * If new data are received on a connection after the
  901: 	 * user processes are gone, then RST the other end.
  902: 	 */
  903: 	if ((so->so_state & SS_NOFDREF) &&
  904: 	    tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) {
  905: 		tp = tcp_close(tp);
  906: 		STAT(tcpstat.tcps_rcvafterclose++);
  907: 		goto dropwithreset;
  908: 	}
  909: 
  910: 	/*
  911: 	 * If segment ends after window, drop trailing data
  912: 	 * (and PUSH and FIN); if nothing left, just ACK.
  913: 	 */
  914: 	todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd);
  915: 	if (todrop > 0) {
  916: 		STAT(tcpstat.tcps_rcvpackafterwin++);
  917: 		if (todrop >= ti->ti_len) {
  918: 			STAT(tcpstat.tcps_rcvbyteafterwin += ti->ti_len);
  919: 			/*
  920: 			 * If a new connection request is received
  921: 			 * while in TIME_WAIT, drop the old connection
  922: 			 * and start over if the sequence numbers
  923: 			 * are above the previous ones.
  924: 			 */
  925: 			if (tiflags & TH_SYN &&
  926: 			    tp->t_state == TCPS_TIME_WAIT &&
  927: 			    SEQ_GT(ti->ti_seq, tp->rcv_nxt)) {
  928: 				iss = tp->rcv_nxt + TCP_ISSINCR;
  929: 				tp = tcp_close(tp);
  930: 				goto findso;
  931: 			}
  932: 			/*
  933: 			 * If window is closed can only take segments at
  934: 			 * window edge, and have to drop data and PUSH from
  935: 			 * incoming segments.  Continue processing, but
  936: 			 * remember to ack.  Otherwise, drop segment
  937: 			 * and ack.
  938: 			 */
  939: 			if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) {
  940: 				tp->t_flags |= TF_ACKNOW;
  941: 				STAT(tcpstat.tcps_rcvwinprobe++);
  942: 			} else
  943: 				goto dropafterack;
  944: 		} else
  945: 			STAT(tcpstat.tcps_rcvbyteafterwin += todrop);
  946: 		m_adj(m, -todrop);
  947: 		ti->ti_len -= todrop;
  948: 		tiflags &= ~(TH_PUSH|TH_FIN);
  949: 	}
  950: 
  951: 	/*
  952: 	 * If last ACK falls within this segment's sequence numbers,
  953: 	 * record its timestamp.
  954: 	 */
  955: /*	if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
  956:  *	    SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len +
  957:  *		   ((tiflags & (TH_SYN|TH_FIN)) != 0))) {
  958:  *		tp->ts_recent_age = tcp_now;
  959:  *		tp->ts_recent = ts_val;
  960:  *	}
  961:  */
  962: 
  963: 	/*
  964: 	 * If the RST bit is set examine the state:
  965: 	 *    SYN_RECEIVED STATE:
  966: 	 *	If passive open, return to LISTEN state.
  967: 	 *	If active open, inform user that connection was refused.
  968: 	 *    ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
  969: 	 *	Inform user that connection was reset, and close tcb.
  970: 	 *    CLOSING, LAST_ACK, TIME_WAIT STATES
  971: 	 *	Close the tcb.
  972: 	 */
  973: 	if (tiflags&TH_RST) switch (tp->t_state) {
  974: 
  975: 	case TCPS_SYN_RECEIVED:
  976: /*		so->so_error = ECONNREFUSED; */
  977: 		goto close;
  978: 
  979: 	case TCPS_ESTABLISHED:
  980: 	case TCPS_FIN_WAIT_1:
  981: 	case TCPS_FIN_WAIT_2:
  982: 	case TCPS_CLOSE_WAIT:
  983: /*		so->so_error = ECONNRESET; */
  984: 	close:
  985: 		tp->t_state = TCPS_CLOSED;
  986: 		STAT(tcpstat.tcps_drops++);
  987: 		tp = tcp_close(tp);
  988: 		goto drop;
  989: 
  990: 	case TCPS_CLOSING:
  991: 	case TCPS_LAST_ACK:
  992: 	case TCPS_TIME_WAIT:
  993: 		tp = tcp_close(tp);
  994: 		goto drop;
  995: 	}
  996: 
  997: 	/*
  998: 	 * If a SYN is in the window, then this is an
  999: 	 * error and we send an RST and drop the connection.
 1000: 	 */
 1001: 	if (tiflags & TH_SYN) {
 1002: 		tp = tcp_drop(tp,0);
 1003: 		goto dropwithreset;
 1004: 	}
 1005: 
 1006: 	/*
 1007: 	 * If the ACK bit is off we drop the segment and return.
 1008: 	 */
 1009: 	if ((tiflags & TH_ACK) == 0) goto drop;
 1010: 
 1011: 	/*
 1012: 	 * Ack processing.
 1013: 	 */
 1014: 	switch (tp->t_state) {
 1015: 	/*
 1016: 	 * In SYN_RECEIVED state if the ack ACKs our SYN then enter
 1017: 	 * ESTABLISHED state and continue processing, otherwise
 1018: 	 * send an RST.  una<=ack<=max
 1019: 	 */
 1020: 	case TCPS_SYN_RECEIVED:
 1021: 
 1022: 		if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
 1023: 		    SEQ_GT(ti->ti_ack, tp->snd_max))
 1024: 			goto dropwithreset;
 1025: 		STAT(tcpstat.tcps_connects++);
 1026: 		tp->t_state = TCPS_ESTABLISHED;
 1027: 		/*
 1028: 		 * The sent SYN is ack'ed with our sequence number +1
 1029: 		 * The first data byte already in the buffer will get
 1030: 		 * lost if no correction is made.  This is only needed for
 1031: 		 * SS_CTL since the buffer is empty otherwise.
 1032: 		 * tp->snd_una++; or:
 1033: 		 */
 1034: 		tp->snd_una=ti->ti_ack;
 1035: 		if (so->so_state & SS_CTL) {
 1036: 		  /* So tcp_ctl reports the right state */
 1037: 		  ret = tcp_ctl(so);
 1038: 		  if (ret == 1) {
 1039: 		    soisfconnected(so);
 1040: 		    so->so_state &= ~SS_CTL;   /* success XXX */
 1041: 		  } else if (ret == 2) {
 1042: 		    so->so_state = SS_NOFDREF; /* CTL_CMD */
 1043: 		  } else {
 1044: 		    needoutput = 1;
 1045: 		    tp->t_state = TCPS_FIN_WAIT_1;
 1046: 		  }
 1047: 		} else {
 1048: 		  soisfconnected(so);
 1049: 		}
 1050: 
 1051: 		/* Do window scaling? */
 1052: /*		if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
 1053:  *			(TF_RCVD_SCALE|TF_REQ_SCALE)) {
 1054:  *			tp->snd_scale = tp->requested_s_scale;
 1055:  *			tp->rcv_scale = tp->request_r_scale;
 1056:  *		}
 1057:  */
 1058: 		(void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0);
 1059: 		tp->snd_wl1 = ti->ti_seq - 1;
 1060: 		/* Avoid ack processing; snd_una==ti_ack  =>  dup ack */
 1061: 		goto synrx_to_est;
 1062: 		/* fall into ... */
 1063: 
 1064: 	/*
 1065: 	 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
 1066: 	 * ACKs.  If the ack is in the range
 1067: 	 *	tp->snd_una < ti->ti_ack <= tp->snd_max
 1068: 	 * then advance tp->snd_una to ti->ti_ack and drop
 1069: 	 * data from the retransmission queue.  If this ACK reflects
 1070: 	 * more up to date window information we update our window information.
 1071: 	 */
 1072: 	case TCPS_ESTABLISHED:
 1073: 	case TCPS_FIN_WAIT_1:
 1074: 	case TCPS_FIN_WAIT_2:
 1075: 	case TCPS_CLOSE_WAIT:
 1076: 	case TCPS_CLOSING:
 1077: 	case TCPS_LAST_ACK:
 1078: 	case TCPS_TIME_WAIT:
 1079: 
 1080: 		if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) {
 1081: 			if (ti->ti_len == 0 && tiwin == tp->snd_wnd) {
 1082: 			  STAT(tcpstat.tcps_rcvdupack++);
 1083: 			  DEBUG_MISC((dfd," dup ack  m = %lx  so = %lx \n",
 1084: 				      (long )m, (long )so));
 1085: 				/*
 1086: 				 * If we have outstanding data (other than
 1087: 				 * a window probe), this is a completely
 1088: 				 * duplicate ack (ie, window info didn't
 1089: 				 * change), the ack is the biggest we've
 1090: 				 * seen and we've seen exactly our rexmt
 1091: 				 * threshold of them, assume a packet
 1092: 				 * has been dropped and retransmit it.
 1093: 				 * Kludge snd_nxt & the congestion
 1094: 				 * window so we send only this one
 1095: 				 * packet.
 1096: 				 *
 1097: 				 * We know we're losing at the current
 1098: 				 * window size so do congestion avoidance
 1099: 				 * (set ssthresh to half the current window
 1100: 				 * and pull our congestion window back to
 1101: 				 * the new ssthresh).
 1102: 				 *
 1103: 				 * Dup acks mean that packets have left the
 1104: 				 * network (they're now cached at the receiver)
 1105: 				 * so bump cwnd by the amount in the receiver
 1106: 				 * to keep a constant cwnd packets in the
 1107: 				 * network.
 1108: 				 */
 1109: 				if (tp->t_timer[TCPT_REXMT] == 0 ||
 1110: 				    ti->ti_ack != tp->snd_una)
 1111: 					tp->t_dupacks = 0;
 1112: 				else if (++tp->t_dupacks == TCPREXMTTHRESH) {
 1113: 					tcp_seq onxt = tp->snd_nxt;
 1114: 					u_int win =
 1115: 					    min(tp->snd_wnd, tp->snd_cwnd) / 2 /
 1116: 						tp->t_maxseg;
 1117: 
 1118: 					if (win < 2)
 1119: 						win = 2;
 1120: 					tp->snd_ssthresh = win * tp->t_maxseg;
 1121: 					tp->t_timer[TCPT_REXMT] = 0;
 1122: 					tp->t_rtt = 0;
 1123: 					tp->snd_nxt = ti->ti_ack;
 1124: 					tp->snd_cwnd = tp->t_maxseg;
 1125: 					(void) tcp_output(tp);
 1126: 					tp->snd_cwnd = tp->snd_ssthresh +
 1127: 					       tp->t_maxseg * tp->t_dupacks;
 1128: 					if (SEQ_GT(onxt, tp->snd_nxt))
 1129: 						tp->snd_nxt = onxt;
 1130: 					goto drop;
 1131: 				} else if (tp->t_dupacks > TCPREXMTTHRESH) {
 1132: 					tp->snd_cwnd += tp->t_maxseg;
 1133: 					(void) tcp_output(tp);
 1134: 					goto drop;
 1135: 				}
 1136: 			} else
 1137: 				tp->t_dupacks = 0;
 1138: 			break;
 1139: 		}
 1140: 	synrx_to_est:
 1141: 		/*
 1142: 		 * If the congestion window was inflated to account
 1143: 		 * for the other side's cached packets, retract it.
 1144: 		 */
 1145: 		if (tp->t_dupacks > TCPREXMTTHRESH &&
 1146: 		    tp->snd_cwnd > tp->snd_ssthresh)
 1147: 			tp->snd_cwnd = tp->snd_ssthresh;
 1148: 		tp->t_dupacks = 0;
 1149: 		if (SEQ_GT(ti->ti_ack, tp->snd_max)) {
 1150: 			STAT(tcpstat.tcps_rcvacktoomuch++);
 1151: 			goto dropafterack;
 1152: 		}
 1153: 		acked = ti->ti_ack - tp->snd_una;
 1154: 		STAT(tcpstat.tcps_rcvackpack++);
 1155: 		STAT(tcpstat.tcps_rcvackbyte += acked);
 1156: 
 1157: 		/*
 1158: 		 * If we have a timestamp reply, update smoothed
 1159: 		 * round trip time.  If no timestamp is present but
 1160: 		 * transmit timer is running and timed sequence
 1161: 		 * number was acked, update smoothed round trip time.
 1162: 		 * Since we now have an rtt measurement, cancel the
 1163: 		 * timer backoff (cf., Phil Karn's retransmit alg.).
 1164: 		 * Recompute the initial retransmit timer.
 1165: 		 */
 1166: /*		if (ts_present)
 1167:  *			tcp_xmit_timer(tp, tcp_now-ts_ecr+1);
 1168:  *		else
 1169:  */
 1170: 		     if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq))
 1171: 			tcp_xmit_timer(tp,tp->t_rtt);
 1172: 
 1173: 		/*
 1174: 		 * If all outstanding data is acked, stop retransmit
 1175: 		 * timer and remember to restart (more output or persist).
 1176: 		 * If there is more data to be acked, restart retransmit
 1177: 		 * timer, using current (possibly backed-off) value.
 1178: 		 */
 1179: 		if (ti->ti_ack == tp->snd_max) {
 1180: 			tp->t_timer[TCPT_REXMT] = 0;
 1181: 			needoutput = 1;
 1182: 		} else if (tp->t_timer[TCPT_PERSIST] == 0)
 1183: 			tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
 1184: 		/*
 1185: 		 * When new data is acked, open the congestion window.
 1186: 		 * If the window gives us less than ssthresh packets
 1187: 		 * in flight, open exponentially (maxseg per packet).
 1188: 		 * Otherwise open linearly: maxseg per window
 1189: 		 * (maxseg^2 / cwnd per packet).
 1190: 		 */
 1191: 		{
 1192: 		  register u_int cw = tp->snd_cwnd;
 1193: 		  register u_int incr = tp->t_maxseg;
 1194: 
 1195: 		  if (cw > tp->snd_ssthresh)
 1196: 		    incr = incr * incr / cw;
 1197: 		  tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale);
 1198: 		}
 1199: 		if (acked > so->so_snd.sb_cc) {
 1200: 			tp->snd_wnd -= so->so_snd.sb_cc;
 1201: 			sbdrop(&so->so_snd, (int )so->so_snd.sb_cc);
 1202: 			ourfinisacked = 1;
 1203: 		} else {
 1204: 			sbdrop(&so->so_snd, acked);
 1205: 			tp->snd_wnd -= acked;
 1206: 			ourfinisacked = 0;
 1207: 		}
 1208: 		/*
 1209: 		 * XXX sowwakup is called when data is acked and there's room for
 1210: 		 * for more data... it should read() the socket
 1211: 		 */
 1212: /*		if (so->so_snd.sb_flags & SB_NOTIFY)
 1213:  *			sowwakeup(so);
 1214:  */
 1215: 		tp->snd_una = ti->ti_ack;
 1216: 		if (SEQ_LT(tp->snd_nxt, tp->snd_una))
 1217: 			tp->snd_nxt = tp->snd_una;
 1218: 
 1219: 		switch (tp->t_state) {
 1220: 
 1221: 		/*
 1222: 		 * In FIN_WAIT_1 STATE in addition to the processing
 1223: 		 * for the ESTABLISHED state if our FIN is now acknowledged
 1224: 		 * then enter FIN_WAIT_2.
 1225: 		 */
 1226: 		case TCPS_FIN_WAIT_1:
 1227: 			if (ourfinisacked) {
 1228: 				/*
 1229: 				 * If we can't receive any more
 1230: 				 * data, then closing user can proceed.
 1231: 				 * Starting the timer is contrary to the
 1232: 				 * specification, but if we don't get a FIN
 1233: 				 * we'll hang forever.
 1234: 				 */
 1235: 				if (so->so_state & SS_FCANTRCVMORE) {
 1236: 					soisfdisconnected(so);
 1237: 					tp->t_timer[TCPT_2MSL] = TCP_MAXIDLE;
 1238: 				}
 1239: 				tp->t_state = TCPS_FIN_WAIT_2;
 1240: 			}
 1241: 			break;
 1242: 
 1243: 	 	/*
 1244: 		 * In CLOSING STATE in addition to the processing for
 1245: 		 * the ESTABLISHED state if the ACK acknowledges our FIN
 1246: 		 * then enter the TIME-WAIT state, otherwise ignore
 1247: 		 * the segment.
 1248: 		 */
 1249: 		case TCPS_CLOSING:
 1250: 			if (ourfinisacked) {
 1251: 				tp->t_state = TCPS_TIME_WAIT;
 1252: 				tcp_canceltimers(tp);
 1253: 				tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
 1254: 				soisfdisconnected(so);
 1255: 			}
 1256: 			break;
 1257: 
 1258: 		/*
 1259: 		 * In LAST_ACK, we may still be waiting for data to drain
 1260: 		 * and/or to be acked, as well as for the ack of our FIN.
 1261: 		 * If our FIN is now acknowledged, delete the TCB,
 1262: 		 * enter the closed state and return.
 1263: 		 */
 1264: 		case TCPS_LAST_ACK:
 1265: 			if (ourfinisacked) {
 1266: 				tp = tcp_close(tp);
 1267: 				goto drop;
 1268: 			}
 1269: 			break;
 1270: 
 1271: 		/*
 1272: 		 * In TIME_WAIT state the only thing that should arrive
 1273: 		 * is a retransmission of the remote FIN.  Acknowledge
 1274: 		 * it and restart the finack timer.
 1275: 		 */
 1276: 		case TCPS_TIME_WAIT:
 1277: 			tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
 1278: 			goto dropafterack;
 1279: 		}
 1280: 	} /* switch(tp->t_state) */
 1281: 
 1282: step6:
 1283: 	/*
 1284: 	 * Update window information.
 1285: 	 * Don't look at window if no ACK: TAC's send garbage on first SYN.
 1286: 	 */
 1287: 	if ((tiflags & TH_ACK) &&
 1288: 	    (SEQ_LT(tp->snd_wl1, ti->ti_seq) ||
 1289: 	    (tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) ||
 1290: 	    (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))))) {
 1291: 		/* keep track of pure window updates */
 1292: 		if (ti->ti_len == 0 &&
 1293: 		    tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd)
 1294: 			STAT(tcpstat.tcps_rcvwinupd++);
 1295: 		tp->snd_wnd = tiwin;
 1296: 		tp->snd_wl1 = ti->ti_seq;
 1297: 		tp->snd_wl2 = ti->ti_ack;
 1298: 		if (tp->snd_wnd > tp->max_sndwnd)
 1299: 			tp->max_sndwnd = tp->snd_wnd;
 1300: 		needoutput = 1;
 1301: 	}
 1302: 
 1303: 	/*
 1304: 	 * Process segments with URG.
 1305: 	 */
 1306: 	if ((tiflags & TH_URG) && ti->ti_urp &&
 1307: 	    TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 1308: 		/*
 1309: 		 * This is a kludge, but if we receive and accept
 1310: 		 * random urgent pointers, we'll crash in
 1311: 		 * soreceive.  It's hard to imagine someone
 1312: 		 * actually wanting to send this much urgent data.
 1313: 		 */
 1314: 		if (ti->ti_urp + so->so_rcv.sb_cc > so->so_rcv.sb_datalen) {
 1315: 			ti->ti_urp = 0;
 1316: 			tiflags &= ~TH_URG;
 1317: 			goto dodata;
 1318: 		}
 1319: 		/*
 1320: 		 * If this segment advances the known urgent pointer,
 1321: 		 * then mark the data stream.  This should not happen
 1322: 		 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
 1323: 		 * a FIN has been received from the remote side.
 1324: 		 * In these states we ignore the URG.
 1325: 		 *
 1326: 		 * According to RFC961 (Assigned Protocols),
 1327: 		 * the urgent pointer points to the last octet
 1328: 		 * of urgent data.  We continue, however,
 1329: 		 * to consider it to indicate the first octet
 1330: 		 * of data past the urgent section as the original
 1331: 		 * spec states (in one of two places).
 1332: 		 */
 1333: 		if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) {
 1334: 			tp->rcv_up = ti->ti_seq + ti->ti_urp;
 1335: 			so->so_urgc =  so->so_rcv.sb_cc +
 1336: 				(tp->rcv_up - tp->rcv_nxt); /* -1; */
 1337: 			tp->rcv_up = ti->ti_seq + ti->ti_urp;
 1338: 
 1339: 		}
 1340: 	} else
 1341: 		/*
 1342: 		 * If no out of band data is expected,
 1343: 		 * pull receive urgent pointer along
 1344: 		 * with the receive window.
 1345: 		 */
 1346: 		if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
 1347: 			tp->rcv_up = tp->rcv_nxt;
 1348: dodata:
 1349: 
 1350: 	/*
 1351: 	 * Process the segment text, merging it into the TCP sequencing queue,
 1352: 	 * and arranging for acknowledgment of receipt if necessary.
 1353: 	 * This process logically involves adjusting tp->rcv_wnd as data
 1354: 	 * is presented to the user (this happens in tcp_usrreq.c,
 1355: 	 * case PRU_RCVD).  If a FIN has already been received on this
 1356: 	 * connection then we just ignore the text.
 1357: 	 */
 1358: 	if ((ti->ti_len || (tiflags&TH_FIN)) &&
 1359: 	    TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 1360: 		TCP_REASS(tp, ti, m, so, tiflags);
 1361: 		/*
 1362: 		 * Note the amount of data that peer has sent into
 1363: 		 * our window, in order to estimate the sender's
 1364: 		 * buffer size.
 1365: 		 */
 1366: 		len = so->so_rcv.sb_datalen - (tp->rcv_adv - tp->rcv_nxt);
 1367: 	} else {
 1368: 		m_free(m);
 1369: 		tiflags &= ~TH_FIN;
 1370: 	}
 1371: 
 1372: 	/*
 1373: 	 * If FIN is received ACK the FIN and let the user know
 1374: 	 * that the connection is closing.
 1375: 	 */
 1376: 	if (tiflags & TH_FIN) {
 1377: 		if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 1378: 			/*
 1379: 			 * If we receive a FIN we can't send more data,
 1380: 			 * set it SS_FDRAIN
 1381:                          * Shutdown the socket if there is no rx data in the
 1382: 			 * buffer.
 1383: 			 * soread() is called on completion of shutdown() and
 1384: 			 * will got to TCPS_LAST_ACK, and use tcp_output()
 1385: 			 * to send the FIN.
 1386: 			 */
 1387: /*			sofcantrcvmore(so); */
 1388: 			sofwdrain(so);
 1389: 
 1390: 			tp->t_flags |= TF_ACKNOW;
 1391: 			tp->rcv_nxt++;
 1392: 		}
 1393: 		switch (tp->t_state) {
 1394: 
 1395: 	 	/*
 1396: 		 * In SYN_RECEIVED and ESTABLISHED STATES
 1397: 		 * enter the CLOSE_WAIT state.
 1398: 		 */
 1399: 		case TCPS_SYN_RECEIVED:
 1400: 		case TCPS_ESTABLISHED:
 1401: 		  if(so->so_emu == EMU_CTL)        /* no shutdown on socket */
 1402: 		    tp->t_state = TCPS_LAST_ACK;
 1403: 		  else
 1404: 		    tp->t_state = TCPS_CLOSE_WAIT;
 1405: 		  break;
 1406: 
 1407: 	 	/*
 1408: 		 * If still in FIN_WAIT_1 STATE FIN has not been acked so
 1409: 		 * enter the CLOSING state.
 1410: 		 */
 1411: 		case TCPS_FIN_WAIT_1:
 1412: 			tp->t_state = TCPS_CLOSING;
 1413: 			break;
 1414: 
 1415: 	 	/*
 1416: 		 * In FIN_WAIT_2 state enter the TIME_WAIT state,
 1417: 		 * starting the time-wait timer, turning off the other
 1418: 		 * standard timers.
 1419: 		 */
 1420: 		case TCPS_FIN_WAIT_2:
 1421: 			tp->t_state = TCPS_TIME_WAIT;
 1422: 			tcp_canceltimers(tp);
 1423: 			tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
 1424: 			soisfdisconnected(so);
 1425: 			break;
 1426: 
 1427: 		/*
 1428: 		 * In TIME_WAIT state restart the 2 MSL time_wait timer.
 1429: 		 */
 1430: 		case TCPS_TIME_WAIT:
 1431: 			tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
 1432: 			break;
 1433: 		}
 1434: 	}
 1435: 
 1436: 	/*
 1437: 	 * If this is a small packet, then ACK now - with Nagel
 1438: 	 *      congestion avoidance sender won't send more until
 1439: 	 *      he gets an ACK.
 1440: 	 *
 1441: 	 * See above.
 1442: 	 */
 1443: /*	if (ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg) {
 1444:  */
 1445: /*	if ((ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg &&
 1446:  *		(so->so_iptos & IPTOS_LOWDELAY) == 0) ||
 1447:  *	       ((so->so_iptos & IPTOS_LOWDELAY) &&
 1448:  *	       ((struct tcpiphdr_2 *)ti)->first_char == (char)27)) {
 1449:  */
 1450: 	if (ti->ti_len && (unsigned)ti->ti_len <= 5 &&
 1451: 	    ((struct tcpiphdr_2 *)ti)->first_char == (char)27) {
 1452: 		tp->t_flags |= TF_ACKNOW;
 1453: 	}
 1454: 
 1455: 	/*
 1456: 	 * Return any desired output.
 1457: 	 */
 1458: 	if (needoutput || (tp->t_flags & TF_ACKNOW)) {
 1459: 		(void) tcp_output(tp);
 1460: 	}
 1461: 	return;
 1462: 
 1463: dropafterack:
 1464: 	/*
 1465: 	 * Generate an ACK dropping incoming segment if it occupies
 1466: 	 * sequence space, where the ACK reflects our state.
 1467: 	 */
 1468: 	if (tiflags & TH_RST)
 1469: 		goto drop;
 1470: 	m_freem(m);
 1471: 	tp->t_flags |= TF_ACKNOW;
 1472: 	(void) tcp_output(tp);
 1473: 	return;
 1474: 
 1475: dropwithreset:
 1476: 	/* reuses m if m!=NULL, m_free() unnecessary */
 1477: 	if (tiflags & TH_ACK)
 1478: 		tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST);
 1479: 	else {
 1480: 		if (tiflags & TH_SYN) ti->ti_len++;
 1481: 		tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0,
 1482: 		    TH_RST|TH_ACK);
 1483: 	}
 1484: 
 1485: 	return;
 1486: 
 1487: drop:
 1488: 	/*
 1489: 	 * Drop space held by incoming segment and return.
 1490: 	 */
 1491: 	m_free(m);
 1492: 
 1493: 	return;
 1494: }
 1495: 
 1496:  /* , ts_present, ts_val, ts_ecr) */
 1497: /*	int *ts_present;
 1498:  *	u_int32_t *ts_val, *ts_ecr;
 1499:  */
 1500: static void
 1501: tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, struct tcpiphdr *ti)
 1502: {
 1503: 	u_int16_t mss;
 1504: 	int opt, optlen;
 1505: 
 1506: 	DEBUG_CALL("tcp_dooptions");
 1507: 	DEBUG_ARGS((dfd," tp = %lx  cnt=%i \n", (long )tp, cnt));
 1508: 
 1509: 	for (; cnt > 0; cnt -= optlen, cp += optlen) {
 1510: 		opt = cp[0];
 1511: 		if (opt == TCPOPT_EOL)
 1512: 			break;
 1513: 		if (opt == TCPOPT_NOP)
 1514: 			optlen = 1;
 1515: 		else {
 1516: 			optlen = cp[1];
 1517: 			if (optlen <= 0)
 1518: 				break;
 1519: 		}
 1520: 		switch (opt) {
 1521: 
 1522: 		default:
 1523: 			continue;
 1524: 
 1525: 		case TCPOPT_MAXSEG:
 1526: 			if (optlen != TCPOLEN_MAXSEG)
 1527: 				continue;
 1528: 			if (!(ti->ti_flags & TH_SYN))
 1529: 				continue;
 1530: 			memcpy((char *) &mss, (char *) cp + 2, sizeof(mss));
 1531: 			NTOHS(mss);
 1532: 			(void) tcp_mss(tp, mss);	/* sets t_maxseg */
 1533: 			break;
 1534: 
 1535: /*		case TCPOPT_WINDOW:
 1536:  *			if (optlen != TCPOLEN_WINDOW)
 1537:  *				continue;
 1538:  *			if (!(ti->ti_flags & TH_SYN))
 1539:  *				continue;
 1540:  *			tp->t_flags |= TF_RCVD_SCALE;
 1541:  *			tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
 1542:  *			break;
 1543:  */
 1544: /*		case TCPOPT_TIMESTAMP:
 1545:  *			if (optlen != TCPOLEN_TIMESTAMP)
 1546:  *				continue;
 1547:  *			*ts_present = 1;
 1548:  *			memcpy((char *) ts_val, (char *)cp + 2, sizeof(*ts_val));
 1549:  *			NTOHL(*ts_val);
 1550:  *			memcpy((char *) ts_ecr, (char *)cp + 6, sizeof(*ts_ecr));
 1551:  *			NTOHL(*ts_ecr);
 1552:  *
 1553:  */			/*
 1554:  *			 * A timestamp received in a SYN makes
 1555:  *			 * it ok to send timestamp requests and replies.
 1556:  *			 */
 1557: /*			if (ti->ti_flags & TH_SYN) {
 1558:  *				tp->t_flags |= TF_RCVD_TSTMP;
 1559:  *				tp->ts_recent = *ts_val;
 1560:  *				tp->ts_recent_age = tcp_now;
 1561:  *			}
 1562:  */			break;
 1563: 		}
 1564: 	}
 1565: }
 1566: 
 1567: 
 1568: /*
 1569:  * Pull out of band byte out of a segment so
 1570:  * it doesn't appear in the user's data queue.
 1571:  * It is still reflected in the segment length for
 1572:  * sequencing purposes.
 1573:  */
 1574: 
 1575: #ifdef notdef
 1576: 
 1577: void
 1578: tcp_pulloutofband(so, ti, m)
 1579: 	struct socket *so;
 1580: 	struct tcpiphdr *ti;
 1581: 	register struct mbuf *m;
 1582: {
 1583: 	int cnt = ti->ti_urp - 1;
 1584: 
 1585: 	while (cnt >= 0) {
 1586: 		if (m->m_len > cnt) {
 1587: 			char *cp = mtod(m, caddr_t) + cnt;
 1588: 			struct tcpcb *tp = sototcpcb(so);
 1589: 
 1590: 			tp->t_iobc = *cp;
 1591: 			tp->t_oobflags |= TCPOOB_HAVEDATA;
 1592: 			memcpy(sp, cp+1, (unsigned)(m->m_len - cnt - 1));
 1593: 			m->m_len--;
 1594: 			return;
 1595: 		}
 1596: 		cnt -= m->m_len;
 1597: 		m = m->m_next; /* XXX WRONG! Fix it! */
 1598: 		if (m == 0)
 1599: 			break;
 1600: 	}
 1601: 	panic("tcp_pulloutofband");
 1602: }
 1603: 
 1604: #endif /* notdef */
 1605: 
 1606: /*
 1607:  * Collect new round-trip time estimate
 1608:  * and update averages and current timeout.
 1609:  */
 1610: 
 1611: static void
 1612: tcp_xmit_timer(register struct tcpcb *tp, int rtt)
 1613: {
 1614: 	register short delta;
 1615: 
 1616: 	DEBUG_CALL("tcp_xmit_timer");
 1617: 	DEBUG_ARG("tp = %lx", (long)tp);
 1618: 	DEBUG_ARG("rtt = %d", rtt);
 1619: 
 1620: 	STAT(tcpstat.tcps_rttupdated++);
 1621: 	if (tp->t_srtt != 0) {
 1622: 		/*
 1623: 		 * srtt is stored as fixed point with 3 bits after the
 1624: 		 * binary point (i.e., scaled by 8).  The following magic
 1625: 		 * is equivalent to the smoothing algorithm in rfc793 with
 1626: 		 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
 1627: 		 * point).  Adjust rtt to origin 0.
 1628: 		 */
 1629: 		delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT);
 1630: 		if ((tp->t_srtt += delta) <= 0)
 1631: 			tp->t_srtt = 1;
 1632: 		/*
 1633: 		 * We accumulate a smoothed rtt variance (actually, a
 1634: 		 * smoothed mean difference), then set the retransmit
 1635: 		 * timer to smoothed rtt + 4 times the smoothed variance.
 1636: 		 * rttvar is stored as fixed point with 2 bits after the
 1637: 		 * binary point (scaled by 4).  The following is
 1638: 		 * equivalent to rfc793 smoothing with an alpha of .75
 1639: 		 * (rttvar = rttvar*3/4 + |delta| / 4).  This replaces
 1640: 		 * rfc793's wired-in beta.
 1641: 		 */
 1642: 		if (delta < 0)
 1643: 			delta = -delta;
 1644: 		delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT);
 1645: 		if ((tp->t_rttvar += delta) <= 0)
 1646: 			tp->t_rttvar = 1;
 1647: 	} else {
 1648: 		/*
 1649: 		 * No rtt measurement yet - use the unsmoothed rtt.
 1650: 		 * Set the variance to half the rtt (so our first
 1651: 		 * retransmit happens at 3*rtt).
 1652: 		 */
 1653: 		tp->t_srtt = rtt << TCP_RTT_SHIFT;
 1654: 		tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
 1655: 	}
 1656: 	tp->t_rtt = 0;
 1657: 	tp->t_rxtshift = 0;
 1658: 
 1659: 	/*
 1660: 	 * the retransmit should happen at rtt + 4 * rttvar.
 1661: 	 * Because of the way we do the smoothing, srtt and rttvar
 1662: 	 * will each average +1/2 tick of bias.  When we compute
 1663: 	 * the retransmit timer, we want 1/2 tick of rounding and
 1664: 	 * 1 extra tick because of +-1/2 tick uncertainty in the
 1665: 	 * firing of the timer.  The bias will give us exactly the
 1666: 	 * 1.5 tick we need.  But, because the bias is
 1667: 	 * statistical, we have to test that we don't drop below
 1668: 	 * the minimum feasible timer (which is 2 ticks).
 1669: 	 */
 1670: 	TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
 1671: 	    (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
 1672: 
 1673: 	/*
 1674: 	 * We received an ack for a packet that wasn't retransmitted;
 1675: 	 * it is probably safe to discard any error indications we've
 1676: 	 * received recently.  This isn't quite right, but close enough
 1677: 	 * for now (a route might have failed after we sent a segment,
 1678: 	 * and the return path might not be symmetrical).
 1679: 	 */
 1680: 	tp->t_softerror = 0;
 1681: }
 1682: 
 1683: /*
 1684:  * Determine a reasonable value for maxseg size.
 1685:  * If the route is known, check route for mtu.
 1686:  * If none, use an mss that can be handled on the outgoing
 1687:  * interface without forcing IP to fragment; if bigger than
 1688:  * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
 1689:  * to utilize large mbufs.  If no route is found, route has no mtu,
 1690:  * or the destination isn't local, use a default, hopefully conservative
 1691:  * size (usually 512 or the default IP max size, but no more than the mtu
 1692:  * of the interface), as we can't discover anything about intervening
 1693:  * gateways or networks.  We also initialize the congestion/slow start
 1694:  * window to be a single segment if the destination isn't local.
 1695:  * While looking at the routing entry, we also initialize other path-dependent
 1696:  * parameters from pre-set or cached values in the routing entry.
 1697:  */
 1698: 
 1699: int
 1700: tcp_mss(tp, offer)
 1701:         register struct tcpcb *tp;
 1702:         u_int offer;
 1703: {
 1704: 	struct socket *so = tp->t_socket;
 1705: 	int mss;
 1706: 
 1707: 	DEBUG_CALL("tcp_mss");
 1708: 	DEBUG_ARG("tp = %lx", (long)tp);
 1709: 	DEBUG_ARG("offer = %d", offer);
 1710: 
 1711: 	mss = min(IF_MTU, IF_MRU) - sizeof(struct tcpiphdr);
 1712: 	if (offer)
 1713: 		mss = min(mss, offer);
 1714: 	mss = max(mss, 32);
 1715: 	if (mss < tp->t_maxseg || offer != 0)
 1716: 	   tp->t_maxseg = mss;
 1717: 
 1718: 	tp->snd_cwnd = mss;
 1719: 
 1720: 	sbreserve(&so->so_snd, TCP_SNDSPACE + ((TCP_SNDSPACE % mss) ?
 1721:                                                (mss - (TCP_SNDSPACE % mss)) :
 1722:                                                0));
 1723: 	sbreserve(&so->so_rcv, TCP_RCVSPACE + ((TCP_RCVSPACE % mss) ?
 1724:                                                (mss - (TCP_RCVSPACE % mss)) :
 1725:                                                0));
 1726: 
 1727: 	DEBUG_MISC((dfd, " returning mss = %d\n", mss));
 1728: 
 1729: 	return mss;
 1730: }

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