File:  [Qemu by Fabrice Bellard] / qemu / slirp / tcp_input.c
Revision 1.1.1.5 (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 17:25:56 2018 UTC (2 years, 10 months ago) by root
Branches: qemu, MAIN
CVS tags: qemu0125, qemu0124, qemu0123, qemu0122, qemu0121, qemu0120, qemu0111, qemu0110, HEAD
qemu 0.11.0

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

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