These changes are a raw update to a vanilla kernel 4.1.10, with the
[kvmfornfv.git] / qemu / slirp / tcp_input.c
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_free(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_free(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_free(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((uint16_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         /*
320          * Locate pcb for segment.
321          */
322 findso:
323         so = slirp->tcp_last_so;
324         if (so->so_fport != ti->ti_dport ||
325             so->so_lport != ti->ti_sport ||
326             so->so_laddr.s_addr != ti->ti_src.s_addr ||
327             so->so_faddr.s_addr != ti->ti_dst.s_addr) {
328                 so = solookup(&slirp->tcb, ti->ti_src, ti->ti_sport,
329                                ti->ti_dst, ti->ti_dport);
330                 if (so)
331                         slirp->tcp_last_so = so;
332         }
333
334         /*
335          * If the state is CLOSED (i.e., TCB does not exist) then
336          * all data in the incoming segment is discarded.
337          * If the TCB exists but is in CLOSED state, it is embryonic,
338          * but should either do a listen or a connect soon.
339          *
340          * state == CLOSED means we've done socreate() but haven't
341          * attached it to a protocol yet...
342          *
343          * XXX If a TCB does not exist, and the TH_SYN flag is
344          * the only flag set, then create a session, mark it
345          * as if it was LISTENING, and continue...
346          */
347         if (so == NULL) {
348           if (slirp->restricted) {
349             /* Any hostfwds will have an existing socket, so we only get here
350              * for non-hostfwd connections. These should be dropped, unless it
351              * happens to be a guestfwd.
352              */
353             for (ex_ptr = slirp->exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
354                 if (ex_ptr->ex_fport == ti->ti_dport &&
355                     ti->ti_dst.s_addr == ex_ptr->ex_addr.s_addr) {
356                     break;
357                 }
358             }
359             if (!ex_ptr) {
360                 goto dropwithreset;
361             }
362           }
363
364           if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN)
365             goto dropwithreset;
366
367           if ((so = socreate(slirp)) == NULL)
368             goto dropwithreset;
369           if (tcp_attach(so) < 0) {
370             free(so); /* Not sofree (if it failed, it's not insqued) */
371             goto dropwithreset;
372           }
373
374           sbreserve(&so->so_snd, TCP_SNDSPACE);
375           sbreserve(&so->so_rcv, TCP_RCVSPACE);
376
377           so->so_laddr = ti->ti_src;
378           so->so_lport = ti->ti_sport;
379           so->so_faddr = ti->ti_dst;
380           so->so_fport = ti->ti_dport;
381
382           if ((so->so_iptos = tcp_tos(so)) == 0)
383             so->so_iptos = ((struct ip *)ti)->ip_tos;
384
385           tp = sototcpcb(so);
386           tp->t_state = TCPS_LISTEN;
387         }
388
389         /*
390          * If this is a still-connecting socket, this probably
391          * a retransmit of the SYN.  Whether it's a retransmit SYN
392          * or something else, we nuke it.
393          */
394         if (so->so_state & SS_ISFCONNECTING)
395                 goto drop;
396
397         tp = sototcpcb(so);
398
399         /* XXX Should never fail */
400         if (tp == NULL)
401                 goto dropwithreset;
402         if (tp->t_state == TCPS_CLOSED)
403                 goto drop;
404
405         tiwin = ti->ti_win;
406
407         /*
408          * Segment received on connection.
409          * Reset idle time and keep-alive timer.
410          */
411         tp->t_idle = 0;
412         if (SO_OPTIONS)
413            tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
414         else
415            tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
416
417         /*
418          * Process options if not in LISTEN state,
419          * else do it below (after getting remote address).
420          */
421         if (optp && tp->t_state != TCPS_LISTEN)
422                 tcp_dooptions(tp, (u_char *)optp, optlen, ti);
423
424         /*
425          * Header prediction: check for the two common cases
426          * of a uni-directional data xfer.  If the packet has
427          * no control flags, is in-sequence, the window didn't
428          * change and we're not retransmitting, it's a
429          * candidate.  If the length is zero and the ack moved
430          * forward, we're the sender side of the xfer.  Just
431          * free the data acked & wake any higher level process
432          * that was blocked waiting for space.  If the length
433          * is non-zero and the ack didn't move, we're the
434          * receiver side.  If we're getting packets in-order
435          * (the reassembly queue is empty), add the data to
436          * the socket buffer and note that we need a delayed ack.
437          *
438          * XXX Some of these tests are not needed
439          * eg: the tiwin == tp->snd_wnd prevents many more
440          * predictions.. with no *real* advantage..
441          */
442         if (tp->t_state == TCPS_ESTABLISHED &&
443             (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
444             ti->ti_seq == tp->rcv_nxt &&
445             tiwin && tiwin == tp->snd_wnd &&
446             tp->snd_nxt == tp->snd_max) {
447                 if (ti->ti_len == 0) {
448                         if (SEQ_GT(ti->ti_ack, tp->snd_una) &&
449                             SEQ_LEQ(ti->ti_ack, tp->snd_max) &&
450                             tp->snd_cwnd >= tp->snd_wnd) {
451                                 /*
452                                  * this is a pure ack for outstanding data.
453                                  */
454                                 if (tp->t_rtt &&
455                                     SEQ_GT(ti->ti_ack, tp->t_rtseq))
456                                         tcp_xmit_timer(tp, tp->t_rtt);
457                                 acked = ti->ti_ack - tp->snd_una;
458                                 sbdrop(&so->so_snd, acked);
459                                 tp->snd_una = ti->ti_ack;
460                                 m_free(m);
461
462                                 /*
463                                  * If all outstanding data are acked, stop
464                                  * retransmit timer, otherwise restart timer
465                                  * using current (possibly backed-off) value.
466                                  * If process is waiting for space,
467                                  * wakeup/selwakeup/signal.  If data
468                                  * are ready to send, let tcp_output
469                                  * decide between more output or persist.
470                                  */
471                                 if (tp->snd_una == tp->snd_max)
472                                         tp->t_timer[TCPT_REXMT] = 0;
473                                 else if (tp->t_timer[TCPT_PERSIST] == 0)
474                                         tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
475
476                                 /*
477                                  * This is called because sowwakeup might have
478                                  * put data into so_snd.  Since we don't so sowwakeup,
479                                  * we don't need this.. XXX???
480                                  */
481                                 if (so->so_snd.sb_cc)
482                                         (void) tcp_output(tp);
483
484                                 return;
485                         }
486                 } else if (ti->ti_ack == tp->snd_una &&
487                     tcpfrag_list_empty(tp) &&
488                     ti->ti_len <= sbspace(&so->so_rcv)) {
489                         /*
490                          * this is a pure, in-sequence data packet
491                          * with nothing on the reassembly queue and
492                          * we have enough buffer space to take it.
493                          */
494                         tp->rcv_nxt += ti->ti_len;
495                         /*
496                          * Add data to socket buffer.
497                          */
498                         if (so->so_emu) {
499                                 if (tcp_emu(so,m)) sbappend(so, m);
500                         } else
501                                 sbappend(so, m);
502
503                         /*
504                          * If this is a short packet, then ACK now - with Nagel
505                          *      congestion avoidance sender won't send more until
506                          *      he gets an ACK.
507                          *
508                          * It is better to not delay acks at all to maximize
509                          * TCP throughput.  See RFC 2581.
510                          */
511                         tp->t_flags |= TF_ACKNOW;
512                         tcp_output(tp);
513                         return;
514                 }
515         } /* header prediction */
516         /*
517          * Calculate amount of space in receive window,
518          * and then do TCP input processing.
519          * Receive window is amount of space in rcv queue,
520          * but not less than advertised window.
521          */
522         { int win;
523           win = sbspace(&so->so_rcv);
524           if (win < 0)
525             win = 0;
526           tp->rcv_wnd = max(win, (int)(tp->rcv_adv - tp->rcv_nxt));
527         }
528
529         switch (tp->t_state) {
530
531         /*
532          * If the state is LISTEN then ignore segment if it contains an RST.
533          * If the segment contains an ACK then it is bad and send a RST.
534          * If it does not contain a SYN then it is not interesting; drop it.
535          * Don't bother responding if the destination was a broadcast.
536          * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
537          * tp->iss, and send a segment:
538          *     <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
539          * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
540          * Fill in remote peer address fields if not previously specified.
541          * Enter SYN_RECEIVED state, and process any other fields of this
542          * segment in this state.
543          */
544         case TCPS_LISTEN: {
545
546           if (tiflags & TH_RST)
547             goto drop;
548           if (tiflags & TH_ACK)
549             goto dropwithreset;
550           if ((tiflags & TH_SYN) == 0)
551             goto drop;
552
553           /*
554            * This has way too many gotos...
555            * But a bit of spaghetti code never hurt anybody :)
556            */
557
558           /*
559            * If this is destined for the control address, then flag to
560            * tcp_ctl once connected, otherwise connect
561            */
562           if ((so->so_faddr.s_addr & slirp->vnetwork_mask.s_addr) ==
563               slirp->vnetwork_addr.s_addr) {
564             if (so->so_faddr.s_addr != slirp->vhost_addr.s_addr &&
565                 so->so_faddr.s_addr != slirp->vnameserver_addr.s_addr) {
566                 /* May be an add exec */
567                 for (ex_ptr = slirp->exec_list; ex_ptr;
568                      ex_ptr = ex_ptr->ex_next) {
569                   if(ex_ptr->ex_fport == so->so_fport &&
570                      so->so_faddr.s_addr == ex_ptr->ex_addr.s_addr) {
571                     so->so_state |= SS_CTL;
572                     break;
573                   }
574                 }
575                 if (so->so_state & SS_CTL) {
576                     goto cont_input;
577                 }
578             }
579             /* CTL_ALIAS: Do nothing, tcp_fconnect will be called on it */
580           }
581
582           if (so->so_emu & EMU_NOCONNECT) {
583             so->so_emu &= ~EMU_NOCONNECT;
584             goto cont_input;
585           }
586
587           if((tcp_fconnect(so) == -1) && (errno != EINPROGRESS) && (errno != EWOULDBLOCK)) {
588             u_char code=ICMP_UNREACH_NET;
589             DEBUG_MISC((dfd, " tcp fconnect errno = %d-%s\n",
590                         errno,strerror(errno)));
591             if(errno == ECONNREFUSED) {
592               /* ACK the SYN, send RST to refuse the connection */
593               tcp_respond(tp, ti, m, ti->ti_seq+1, (tcp_seq)0,
594                           TH_RST|TH_ACK);
595             } else {
596               if(errno == EHOSTUNREACH) code=ICMP_UNREACH_HOST;
597               HTONL(ti->ti_seq);             /* restore tcp header */
598               HTONL(ti->ti_ack);
599               HTONS(ti->ti_win);
600               HTONS(ti->ti_urp);
601               m->m_data -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
602               m->m_len  += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
603               *ip=save_ip;
604               icmp_error(m, ICMP_UNREACH,code, 0,strerror(errno));
605             }
606             tcp_close(tp);
607             m_free(m);
608           } else {
609             /*
610              * Haven't connected yet, save the current mbuf
611              * and ti, and return
612              * XXX Some OS's don't tell us whether the connect()
613              * succeeded or not.  So we must time it out.
614              */
615             so->so_m = m;
616             so->so_ti = ti;
617             tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
618             tp->t_state = TCPS_SYN_RECEIVED;
619             tcp_template(tp);
620           }
621           return;
622
623         cont_conn:
624           /* m==NULL
625            * Check if the connect succeeded
626            */
627           if (so->so_state & SS_NOFDREF) {
628             tp = tcp_close(tp);
629             goto dropwithreset;
630           }
631         cont_input:
632           tcp_template(tp);
633
634           if (optp)
635             tcp_dooptions(tp, (u_char *)optp, optlen, ti);
636
637           if (iss)
638             tp->iss = iss;
639           else
640             tp->iss = slirp->tcp_iss;
641           slirp->tcp_iss += TCP_ISSINCR/2;
642           tp->irs = ti->ti_seq;
643           tcp_sendseqinit(tp);
644           tcp_rcvseqinit(tp);
645           tp->t_flags |= TF_ACKNOW;
646           tp->t_state = TCPS_SYN_RECEIVED;
647           tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
648           goto trimthenstep6;
649         } /* case TCPS_LISTEN */
650
651         /*
652          * If the state is SYN_SENT:
653          *      if seg contains an ACK, but not for our SYN, drop the input.
654          *      if seg contains a RST, then drop the connection.
655          *      if seg does not contain SYN, then drop it.
656          * Otherwise this is an acceptable SYN segment
657          *      initialize tp->rcv_nxt and tp->irs
658          *      if seg contains ack then advance tp->snd_una
659          *      if SYN has been acked change to ESTABLISHED else SYN_RCVD state
660          *      arrange for segment to be acked (eventually)
661          *      continue processing rest of data/controls, beginning with URG
662          */
663         case TCPS_SYN_SENT:
664                 if ((tiflags & TH_ACK) &&
665                     (SEQ_LEQ(ti->ti_ack, tp->iss) ||
666                      SEQ_GT(ti->ti_ack, tp->snd_max)))
667                         goto dropwithreset;
668
669                 if (tiflags & TH_RST) {
670                         if (tiflags & TH_ACK) {
671                                 tcp_drop(tp, 0); /* XXX Check t_softerror! */
672                         }
673                         goto drop;
674                 }
675
676                 if ((tiflags & TH_SYN) == 0)
677                         goto drop;
678                 if (tiflags & TH_ACK) {
679                         tp->snd_una = ti->ti_ack;
680                         if (SEQ_LT(tp->snd_nxt, tp->snd_una))
681                                 tp->snd_nxt = tp->snd_una;
682                 }
683
684                 tp->t_timer[TCPT_REXMT] = 0;
685                 tp->irs = ti->ti_seq;
686                 tcp_rcvseqinit(tp);
687                 tp->t_flags |= TF_ACKNOW;
688                 if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) {
689                         soisfconnected(so);
690                         tp->t_state = TCPS_ESTABLISHED;
691
692                         (void) tcp_reass(tp, (struct tcpiphdr *)0,
693                                 (struct mbuf *)0);
694                         /*
695                          * if we didn't have to retransmit the SYN,
696                          * use its rtt as our initial srtt & rtt var.
697                          */
698                         if (tp->t_rtt)
699                                 tcp_xmit_timer(tp, tp->t_rtt);
700                 } else
701                         tp->t_state = TCPS_SYN_RECEIVED;
702
703 trimthenstep6:
704                 /*
705                  * Advance ti->ti_seq to correspond to first data byte.
706                  * If data, trim to stay within window,
707                  * dropping FIN if necessary.
708                  */
709                 ti->ti_seq++;
710                 if (ti->ti_len > tp->rcv_wnd) {
711                         todrop = ti->ti_len - tp->rcv_wnd;
712                         m_adj(m, -todrop);
713                         ti->ti_len = tp->rcv_wnd;
714                         tiflags &= ~TH_FIN;
715                 }
716                 tp->snd_wl1 = ti->ti_seq - 1;
717                 tp->rcv_up = ti->ti_seq;
718                 goto step6;
719         } /* switch tp->t_state */
720         /*
721          * States other than LISTEN or SYN_SENT.
722          * Check that at least some bytes of segment are within
723          * receive window.  If segment begins before rcv_nxt,
724          * drop leading data (and SYN); if nothing left, just ack.
725          */
726         todrop = tp->rcv_nxt - ti->ti_seq;
727         if (todrop > 0) {
728                 if (tiflags & TH_SYN) {
729                         tiflags &= ~TH_SYN;
730                         ti->ti_seq++;
731                         if (ti->ti_urp > 1)
732                                 ti->ti_urp--;
733                         else
734                                 tiflags &= ~TH_URG;
735                         todrop--;
736                 }
737                 /*
738                  * Following if statement from Stevens, vol. 2, p. 960.
739                  */
740                 if (todrop > ti->ti_len
741                     || (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) {
742                         /*
743                          * Any valid FIN must be to the left of the window.
744                          * At this point the FIN must be a duplicate or out
745                          * of sequence; drop it.
746                          */
747                         tiflags &= ~TH_FIN;
748
749                         /*
750                          * Send an ACK to resynchronize and drop any data.
751                          * But keep on processing for RST or ACK.
752                          */
753                         tp->t_flags |= TF_ACKNOW;
754                         todrop = ti->ti_len;
755                 }
756                 m_adj(m, todrop);
757                 ti->ti_seq += todrop;
758                 ti->ti_len -= todrop;
759                 if (ti->ti_urp > todrop)
760                         ti->ti_urp -= todrop;
761                 else {
762                         tiflags &= ~TH_URG;
763                         ti->ti_urp = 0;
764                 }
765         }
766         /*
767          * If new data are received on a connection after the
768          * user processes are gone, then RST the other end.
769          */
770         if ((so->so_state & SS_NOFDREF) &&
771             tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) {
772                 tp = tcp_close(tp);
773                 goto dropwithreset;
774         }
775
776         /*
777          * If segment ends after window, drop trailing data
778          * (and PUSH and FIN); if nothing left, just ACK.
779          */
780         todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd);
781         if (todrop > 0) {
782                 if (todrop >= ti->ti_len) {
783                         /*
784                          * If a new connection request is received
785                          * while in TIME_WAIT, drop the old connection
786                          * and start over if the sequence numbers
787                          * are above the previous ones.
788                          */
789                         if (tiflags & TH_SYN &&
790                             tp->t_state == TCPS_TIME_WAIT &&
791                             SEQ_GT(ti->ti_seq, tp->rcv_nxt)) {
792                                 iss = tp->rcv_nxt + TCP_ISSINCR;
793                                 tp = tcp_close(tp);
794                                 goto findso;
795                         }
796                         /*
797                          * If window is closed can only take segments at
798                          * window edge, and have to drop data and PUSH from
799                          * incoming segments.  Continue processing, but
800                          * remember to ack.  Otherwise, drop segment
801                          * and ack.
802                          */
803                         if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) {
804                                 tp->t_flags |= TF_ACKNOW;
805                         } else {
806                                 goto dropafterack;
807                         }
808                 }
809                 m_adj(m, -todrop);
810                 ti->ti_len -= todrop;
811                 tiflags &= ~(TH_PUSH|TH_FIN);
812         }
813
814         /*
815          * If the RST bit is set examine the state:
816          *    SYN_RECEIVED STATE:
817          *      If passive open, return to LISTEN state.
818          *      If active open, inform user that connection was refused.
819          *    ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
820          *      Inform user that connection was reset, and close tcb.
821          *    CLOSING, LAST_ACK, TIME_WAIT STATES
822          *      Close the tcb.
823          */
824         if (tiflags&TH_RST) switch (tp->t_state) {
825
826         case TCPS_SYN_RECEIVED:
827         case TCPS_ESTABLISHED:
828         case TCPS_FIN_WAIT_1:
829         case TCPS_FIN_WAIT_2:
830         case TCPS_CLOSE_WAIT:
831                 tp->t_state = TCPS_CLOSED;
832                 tcp_close(tp);
833                 goto drop;
834
835         case TCPS_CLOSING:
836         case TCPS_LAST_ACK:
837         case TCPS_TIME_WAIT:
838                 tcp_close(tp);
839                 goto drop;
840         }
841
842         /*
843          * If a SYN is in the window, then this is an
844          * error and we send an RST and drop the connection.
845          */
846         if (tiflags & TH_SYN) {
847                 tp = tcp_drop(tp,0);
848                 goto dropwithreset;
849         }
850
851         /*
852          * If the ACK bit is off we drop the segment and return.
853          */
854         if ((tiflags & TH_ACK) == 0) goto drop;
855
856         /*
857          * Ack processing.
858          */
859         switch (tp->t_state) {
860         /*
861          * In SYN_RECEIVED state if the ack ACKs our SYN then enter
862          * ESTABLISHED state and continue processing, otherwise
863          * send an RST.  una<=ack<=max
864          */
865         case TCPS_SYN_RECEIVED:
866
867                 if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
868                     SEQ_GT(ti->ti_ack, tp->snd_max))
869                         goto dropwithreset;
870                 tp->t_state = TCPS_ESTABLISHED;
871                 /*
872                  * The sent SYN is ack'ed with our sequence number +1
873                  * The first data byte already in the buffer will get
874                  * lost if no correction is made.  This is only needed for
875                  * SS_CTL since the buffer is empty otherwise.
876                  * tp->snd_una++; or:
877                  */
878                 tp->snd_una=ti->ti_ack;
879                 if (so->so_state & SS_CTL) {
880                   /* So tcp_ctl reports the right state */
881                   ret = tcp_ctl(so);
882                   if (ret == 1) {
883                     soisfconnected(so);
884                     so->so_state &= ~SS_CTL;   /* success XXX */
885                   } else if (ret == 2) {
886                     so->so_state &= SS_PERSISTENT_MASK;
887                     so->so_state |= SS_NOFDREF; /* CTL_CMD */
888                   } else {
889                     needoutput = 1;
890                     tp->t_state = TCPS_FIN_WAIT_1;
891                   }
892                 } else {
893                   soisfconnected(so);
894                 }
895
896                 (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0);
897                 tp->snd_wl1 = ti->ti_seq - 1;
898                 /* Avoid ack processing; snd_una==ti_ack  =>  dup ack */
899                 goto synrx_to_est;
900                 /* fall into ... */
901
902         /*
903          * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
904          * ACKs.  If the ack is in the range
905          *      tp->snd_una < ti->ti_ack <= tp->snd_max
906          * then advance tp->snd_una to ti->ti_ack and drop
907          * data from the retransmission queue.  If this ACK reflects
908          * more up to date window information we update our window information.
909          */
910         case TCPS_ESTABLISHED:
911         case TCPS_FIN_WAIT_1:
912         case TCPS_FIN_WAIT_2:
913         case TCPS_CLOSE_WAIT:
914         case TCPS_CLOSING:
915         case TCPS_LAST_ACK:
916         case TCPS_TIME_WAIT:
917
918                 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) {
919                         if (ti->ti_len == 0 && tiwin == tp->snd_wnd) {
920                           DEBUG_MISC((dfd, " dup ack  m = %lx  so = %lx\n",
921                                       (long )m, (long )so));
922                                 /*
923                                  * If we have outstanding data (other than
924                                  * a window probe), this is a completely
925                                  * duplicate ack (ie, window info didn't
926                                  * change), the ack is the biggest we've
927                                  * seen and we've seen exactly our rexmt
928                                  * threshold of them, assume a packet
929                                  * has been dropped and retransmit it.
930                                  * Kludge snd_nxt & the congestion
931                                  * window so we send only this one
932                                  * packet.
933                                  *
934                                  * We know we're losing at the current
935                                  * window size so do congestion avoidance
936                                  * (set ssthresh to half the current window
937                                  * and pull our congestion window back to
938                                  * the new ssthresh).
939                                  *
940                                  * Dup acks mean that packets have left the
941                                  * network (they're now cached at the receiver)
942                                  * so bump cwnd by the amount in the receiver
943                                  * to keep a constant cwnd packets in the
944                                  * network.
945                                  */
946                                 if (tp->t_timer[TCPT_REXMT] == 0 ||
947                                     ti->ti_ack != tp->snd_una)
948                                         tp->t_dupacks = 0;
949                                 else if (++tp->t_dupacks == TCPREXMTTHRESH) {
950                                         tcp_seq onxt = tp->snd_nxt;
951                                         u_int win =
952                                             min(tp->snd_wnd, tp->snd_cwnd) / 2 /
953                                                 tp->t_maxseg;
954
955                                         if (win < 2)
956                                                 win = 2;
957                                         tp->snd_ssthresh = win * tp->t_maxseg;
958                                         tp->t_timer[TCPT_REXMT] = 0;
959                                         tp->t_rtt = 0;
960                                         tp->snd_nxt = ti->ti_ack;
961                                         tp->snd_cwnd = tp->t_maxseg;
962                                         (void) tcp_output(tp);
963                                         tp->snd_cwnd = tp->snd_ssthresh +
964                                                tp->t_maxseg * tp->t_dupacks;
965                                         if (SEQ_GT(onxt, tp->snd_nxt))
966                                                 tp->snd_nxt = onxt;
967                                         goto drop;
968                                 } else if (tp->t_dupacks > TCPREXMTTHRESH) {
969                                         tp->snd_cwnd += tp->t_maxseg;
970                                         (void) tcp_output(tp);
971                                         goto drop;
972                                 }
973                         } else
974                                 tp->t_dupacks = 0;
975                         break;
976                 }
977         synrx_to_est:
978                 /*
979                  * If the congestion window was inflated to account
980                  * for the other side's cached packets, retract it.
981                  */
982                 if (tp->t_dupacks > TCPREXMTTHRESH &&
983                     tp->snd_cwnd > tp->snd_ssthresh)
984                         tp->snd_cwnd = tp->snd_ssthresh;
985                 tp->t_dupacks = 0;
986                 if (SEQ_GT(ti->ti_ack, tp->snd_max)) {
987                         goto dropafterack;
988                 }
989                 acked = ti->ti_ack - tp->snd_una;
990
991                 /*
992                  * If transmit timer is running and timed sequence
993                  * number was acked, update smoothed round trip time.
994                  * Since we now have an rtt measurement, cancel the
995                  * timer backoff (cf., Phil Karn's retransmit alg.).
996                  * Recompute the initial retransmit timer.
997                  */
998                 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq))
999                         tcp_xmit_timer(tp,tp->t_rtt);
1000
1001                 /*
1002                  * If all outstanding data is acked, stop retransmit
1003                  * timer and remember to restart (more output or persist).
1004                  * If there is more data to be acked, restart retransmit
1005                  * timer, using current (possibly backed-off) value.
1006                  */
1007                 if (ti->ti_ack == tp->snd_max) {
1008                         tp->t_timer[TCPT_REXMT] = 0;
1009                         needoutput = 1;
1010                 } else if (tp->t_timer[TCPT_PERSIST] == 0)
1011                         tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
1012                 /*
1013                  * When new data is acked, open the congestion window.
1014                  * If the window gives us less than ssthresh packets
1015                  * in flight, open exponentially (maxseg per packet).
1016                  * Otherwise open linearly: maxseg per window
1017                  * (maxseg^2 / cwnd per packet).
1018                  */
1019                 {
1020                   register u_int cw = tp->snd_cwnd;
1021                   register u_int incr = tp->t_maxseg;
1022
1023                   if (cw > tp->snd_ssthresh)
1024                     incr = incr * incr / cw;
1025                   tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale);
1026                 }
1027                 if (acked > so->so_snd.sb_cc) {
1028                         tp->snd_wnd -= so->so_snd.sb_cc;
1029                         sbdrop(&so->so_snd, (int )so->so_snd.sb_cc);
1030                         ourfinisacked = 1;
1031                 } else {
1032                         sbdrop(&so->so_snd, acked);
1033                         tp->snd_wnd -= acked;
1034                         ourfinisacked = 0;
1035                 }
1036                 tp->snd_una = ti->ti_ack;
1037                 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
1038                         tp->snd_nxt = tp->snd_una;
1039
1040                 switch (tp->t_state) {
1041
1042                 /*
1043                  * In FIN_WAIT_1 STATE in addition to the processing
1044                  * for the ESTABLISHED state if our FIN is now acknowledged
1045                  * then enter FIN_WAIT_2.
1046                  */
1047                 case TCPS_FIN_WAIT_1:
1048                         if (ourfinisacked) {
1049                                 /*
1050                                  * If we can't receive any more
1051                                  * data, then closing user can proceed.
1052                                  * Starting the timer is contrary to the
1053                                  * specification, but if we don't get a FIN
1054                                  * we'll hang forever.
1055                                  */
1056                                 if (so->so_state & SS_FCANTRCVMORE) {
1057                                         tp->t_timer[TCPT_2MSL] = TCP_MAXIDLE;
1058                                 }
1059                                 tp->t_state = TCPS_FIN_WAIT_2;
1060                         }
1061                         break;
1062
1063                 /*
1064                  * In CLOSING STATE in addition to the processing for
1065                  * the ESTABLISHED state if the ACK acknowledges our FIN
1066                  * then enter the TIME-WAIT state, otherwise ignore
1067                  * the segment.
1068                  */
1069                 case TCPS_CLOSING:
1070                         if (ourfinisacked) {
1071                                 tp->t_state = TCPS_TIME_WAIT;
1072                                 tcp_canceltimers(tp);
1073                                 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1074                         }
1075                         break;
1076
1077                 /*
1078                  * In LAST_ACK, we may still be waiting for data to drain
1079                  * and/or to be acked, as well as for the ack of our FIN.
1080                  * If our FIN is now acknowledged, delete the TCB,
1081                  * enter the closed state and return.
1082                  */
1083                 case TCPS_LAST_ACK:
1084                         if (ourfinisacked) {
1085                                 tcp_close(tp);
1086                                 goto drop;
1087                         }
1088                         break;
1089
1090                 /*
1091                  * In TIME_WAIT state the only thing that should arrive
1092                  * is a retransmission of the remote FIN.  Acknowledge
1093                  * it and restart the finack timer.
1094                  */
1095                 case TCPS_TIME_WAIT:
1096                         tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1097                         goto dropafterack;
1098                 }
1099         } /* switch(tp->t_state) */
1100
1101 step6:
1102         /*
1103          * Update window information.
1104          * Don't look at window if no ACK: TAC's send garbage on first SYN.
1105          */
1106         if ((tiflags & TH_ACK) &&
1107             (SEQ_LT(tp->snd_wl1, ti->ti_seq) ||
1108             (tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) ||
1109             (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))))) {
1110                 tp->snd_wnd = tiwin;
1111                 tp->snd_wl1 = ti->ti_seq;
1112                 tp->snd_wl2 = ti->ti_ack;
1113                 if (tp->snd_wnd > tp->max_sndwnd)
1114                         tp->max_sndwnd = tp->snd_wnd;
1115                 needoutput = 1;
1116         }
1117
1118         /*
1119          * Process segments with URG.
1120          */
1121         if ((tiflags & TH_URG) && ti->ti_urp &&
1122             TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1123                 /*
1124                  * This is a kludge, but if we receive and accept
1125                  * random urgent pointers, we'll crash in
1126                  * soreceive.  It's hard to imagine someone
1127                  * actually wanting to send this much urgent data.
1128                  */
1129                 if (ti->ti_urp + so->so_rcv.sb_cc > so->so_rcv.sb_datalen) {
1130                         ti->ti_urp = 0;
1131                         tiflags &= ~TH_URG;
1132                         goto dodata;
1133                 }
1134                 /*
1135                  * If this segment advances the known urgent pointer,
1136                  * then mark the data stream.  This should not happen
1137                  * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
1138                  * a FIN has been received from the remote side.
1139                  * In these states we ignore the URG.
1140                  *
1141                  * According to RFC961 (Assigned Protocols),
1142                  * the urgent pointer points to the last octet
1143                  * of urgent data.  We continue, however,
1144                  * to consider it to indicate the first octet
1145                  * of data past the urgent section as the original
1146                  * spec states (in one of two places).
1147                  */
1148                 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) {
1149                         tp->rcv_up = ti->ti_seq + ti->ti_urp;
1150                         so->so_urgc =  so->so_rcv.sb_cc +
1151                                 (tp->rcv_up - tp->rcv_nxt); /* -1; */
1152                         tp->rcv_up = ti->ti_seq + ti->ti_urp;
1153
1154                 }
1155         } else
1156                 /*
1157                  * If no out of band data is expected,
1158                  * pull receive urgent pointer along
1159                  * with the receive window.
1160                  */
1161                 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
1162                         tp->rcv_up = tp->rcv_nxt;
1163 dodata:
1164
1165         /*
1166          * If this is a small packet, then ACK now - with Nagel
1167          *      congestion avoidance sender won't send more until
1168          *      he gets an ACK.
1169          */
1170         if (ti->ti_len && (unsigned)ti->ti_len <= 5 &&
1171             ((struct tcpiphdr_2 *)ti)->first_char == (char)27) {
1172                 tp->t_flags |= TF_ACKNOW;
1173         }
1174
1175         /*
1176          * Process the segment text, merging it into the TCP sequencing queue,
1177          * and arranging for acknowledgment of receipt if necessary.
1178          * This process logically involves adjusting tp->rcv_wnd as data
1179          * is presented to the user (this happens in tcp_usrreq.c,
1180          * case PRU_RCVD).  If a FIN has already been received on this
1181          * connection then we just ignore the text.
1182          */
1183         if ((ti->ti_len || (tiflags&TH_FIN)) &&
1184             TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1185                 TCP_REASS(tp, ti, m, so, tiflags);
1186         } else {
1187                 m_free(m);
1188                 tiflags &= ~TH_FIN;
1189         }
1190
1191         /*
1192          * If FIN is received ACK the FIN and let the user know
1193          * that the connection is closing.
1194          */
1195         if (tiflags & TH_FIN) {
1196                 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1197                         /*
1198                          * If we receive a FIN we can't send more data,
1199                          * set it SS_FDRAIN
1200                          * Shutdown the socket if there is no rx data in the
1201                          * buffer.
1202                          * soread() is called on completion of shutdown() and
1203                          * will got to TCPS_LAST_ACK, and use tcp_output()
1204                          * to send the FIN.
1205                          */
1206                         sofwdrain(so);
1207
1208                         tp->t_flags |= TF_ACKNOW;
1209                         tp->rcv_nxt++;
1210                 }
1211                 switch (tp->t_state) {
1212
1213                 /*
1214                  * In SYN_RECEIVED and ESTABLISHED STATES
1215                  * enter the CLOSE_WAIT state.
1216                  */
1217                 case TCPS_SYN_RECEIVED:
1218                 case TCPS_ESTABLISHED:
1219                   if(so->so_emu == EMU_CTL)        /* no shutdown on socket */
1220                     tp->t_state = TCPS_LAST_ACK;
1221                   else
1222                     tp->t_state = TCPS_CLOSE_WAIT;
1223                   break;
1224
1225                 /*
1226                  * If still in FIN_WAIT_1 STATE FIN has not been acked so
1227                  * enter the CLOSING state.
1228                  */
1229                 case TCPS_FIN_WAIT_1:
1230                         tp->t_state = TCPS_CLOSING;
1231                         break;
1232
1233                 /*
1234                  * In FIN_WAIT_2 state enter the TIME_WAIT state,
1235                  * starting the time-wait timer, turning off the other
1236                  * standard timers.
1237                  */
1238                 case TCPS_FIN_WAIT_2:
1239                         tp->t_state = TCPS_TIME_WAIT;
1240                         tcp_canceltimers(tp);
1241                         tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1242                         break;
1243
1244                 /*
1245                  * In TIME_WAIT state restart the 2 MSL time_wait timer.
1246                  */
1247                 case TCPS_TIME_WAIT:
1248                         tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1249                         break;
1250                 }
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_free(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
1292 static void
1293 tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, struct tcpiphdr *ti)
1294 {
1295         uint16_t mss;
1296         int opt, optlen;
1297
1298         DEBUG_CALL("tcp_dooptions");
1299         DEBUG_ARGS((dfd, " tp = %lx  cnt=%i\n", (long)tp, cnt));
1300
1301         for (; cnt > 0; cnt -= optlen, cp += optlen) {
1302                 opt = cp[0];
1303                 if (opt == TCPOPT_EOL)
1304                         break;
1305                 if (opt == TCPOPT_NOP)
1306                         optlen = 1;
1307                 else {
1308                         optlen = cp[1];
1309                         if (optlen <= 0)
1310                                 break;
1311                 }
1312                 switch (opt) {
1313
1314                 default:
1315                         continue;
1316
1317                 case TCPOPT_MAXSEG:
1318                         if (optlen != TCPOLEN_MAXSEG)
1319                                 continue;
1320                         if (!(ti->ti_flags & TH_SYN))
1321                                 continue;
1322                         memcpy((char *) &mss, (char *) cp + 2, sizeof(mss));
1323                         NTOHS(mss);
1324                         (void) tcp_mss(tp, mss);        /* sets t_maxseg */
1325                         break;
1326                 }
1327         }
1328 }
1329
1330
1331 /*
1332  * Pull out of band byte out of a segment so
1333  * it doesn't appear in the user's data queue.
1334  * It is still reflected in the segment length for
1335  * sequencing purposes.
1336  */
1337
1338 #ifdef notdef
1339
1340 void
1341 tcp_pulloutofband(so, ti, m)
1342         struct socket *so;
1343         struct tcpiphdr *ti;
1344         register struct mbuf *m;
1345 {
1346         int cnt = ti->ti_urp - 1;
1347
1348         while (cnt >= 0) {
1349                 if (m->m_len > cnt) {
1350                         char *cp = mtod(m, caddr_t) + cnt;
1351                         struct tcpcb *tp = sototcpcb(so);
1352
1353                         tp->t_iobc = *cp;
1354                         tp->t_oobflags |= TCPOOB_HAVEDATA;
1355                         memcpy(sp, cp+1, (unsigned)(m->m_len - cnt - 1));
1356                         m->m_len--;
1357                         return;
1358                 }
1359                 cnt -= m->m_len;
1360                 m = m->m_next; /* XXX WRONG! Fix it! */
1361                 if (m == 0)
1362                         break;
1363         }
1364         panic("tcp_pulloutofband");
1365 }
1366
1367 #endif /* notdef */
1368
1369 /*
1370  * Collect new round-trip time estimate
1371  * and update averages and current timeout.
1372  */
1373
1374 static void
1375 tcp_xmit_timer(register struct tcpcb *tp, int rtt)
1376 {
1377         register short delta;
1378
1379         DEBUG_CALL("tcp_xmit_timer");
1380         DEBUG_ARG("tp = %lx", (long)tp);
1381         DEBUG_ARG("rtt = %d", rtt);
1382
1383         if (tp->t_srtt != 0) {
1384                 /*
1385                  * srtt is stored as fixed point with 3 bits after the
1386                  * binary point (i.e., scaled by 8).  The following magic
1387                  * is equivalent to the smoothing algorithm in rfc793 with
1388                  * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
1389                  * point).  Adjust rtt to origin 0.
1390                  */
1391                 delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT);
1392                 if ((tp->t_srtt += delta) <= 0)
1393                         tp->t_srtt = 1;
1394                 /*
1395                  * We accumulate a smoothed rtt variance (actually, a
1396                  * smoothed mean difference), then set the retransmit
1397                  * timer to smoothed rtt + 4 times the smoothed variance.
1398                  * rttvar is stored as fixed point with 2 bits after the
1399                  * binary point (scaled by 4).  The following is
1400                  * equivalent to rfc793 smoothing with an alpha of .75
1401                  * (rttvar = rttvar*3/4 + |delta| / 4).  This replaces
1402                  * rfc793's wired-in beta.
1403                  */
1404                 if (delta < 0)
1405                         delta = -delta;
1406                 delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT);
1407                 if ((tp->t_rttvar += delta) <= 0)
1408                         tp->t_rttvar = 1;
1409         } else {
1410                 /*
1411                  * No rtt measurement yet - use the unsmoothed rtt.
1412                  * Set the variance to half the rtt (so our first
1413                  * retransmit happens at 3*rtt).
1414                  */
1415                 tp->t_srtt = rtt << TCP_RTT_SHIFT;
1416                 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
1417         }
1418         tp->t_rtt = 0;
1419         tp->t_rxtshift = 0;
1420
1421         /*
1422          * the retransmit should happen at rtt + 4 * rttvar.
1423          * Because of the way we do the smoothing, srtt and rttvar
1424          * will each average +1/2 tick of bias.  When we compute
1425          * the retransmit timer, we want 1/2 tick of rounding and
1426          * 1 extra tick because of +-1/2 tick uncertainty in the
1427          * firing of the timer.  The bias will give us exactly the
1428          * 1.5 tick we need.  But, because the bias is
1429          * statistical, we have to test that we don't drop below
1430          * the minimum feasible timer (which is 2 ticks).
1431          */
1432         TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
1433             (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
1434
1435         /*
1436          * We received an ack for a packet that wasn't retransmitted;
1437          * it is probably safe to discard any error indications we've
1438          * received recently.  This isn't quite right, but close enough
1439          * for now (a route might have failed after we sent a segment,
1440          * and the return path might not be symmetrical).
1441          */
1442         tp->t_softerror = 0;
1443 }
1444
1445 /*
1446  * Determine a reasonable value for maxseg size.
1447  * If the route is known, check route for mtu.
1448  * If none, use an mss that can be handled on the outgoing
1449  * interface without forcing IP to fragment; if bigger than
1450  * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
1451  * to utilize large mbufs.  If no route is found, route has no mtu,
1452  * or the destination isn't local, use a default, hopefully conservative
1453  * size (usually 512 or the default IP max size, but no more than the mtu
1454  * of the interface), as we can't discover anything about intervening
1455  * gateways or networks.  We also initialize the congestion/slow start
1456  * window to be a single segment if the destination isn't local.
1457  * While looking at the routing entry, we also initialize other path-dependent
1458  * parameters from pre-set or cached values in the routing entry.
1459  */
1460
1461 int
1462 tcp_mss(struct tcpcb *tp, u_int offer)
1463 {
1464         struct socket *so = tp->t_socket;
1465         int mss;
1466
1467         DEBUG_CALL("tcp_mss");
1468         DEBUG_ARG("tp = %lx", (long)tp);
1469         DEBUG_ARG("offer = %d", offer);
1470
1471         mss = min(IF_MTU, IF_MRU) - sizeof(struct tcpiphdr);
1472         if (offer)
1473                 mss = min(mss, offer);
1474         mss = max(mss, 32);
1475         if (mss < tp->t_maxseg || offer != 0)
1476            tp->t_maxseg = mss;
1477
1478         tp->snd_cwnd = mss;
1479
1480         sbreserve(&so->so_snd, TCP_SNDSPACE + ((TCP_SNDSPACE % mss) ?
1481                                                (mss - (TCP_SNDSPACE % mss)) :
1482                                                0));
1483         sbreserve(&so->so_rcv, TCP_RCVSPACE + ((TCP_RCVSPACE % mss) ?
1484                                                (mss - (TCP_RCVSPACE % mss)) :
1485                                                0));
1486
1487         DEBUG_MISC((dfd, " returning mss = %d\n", mss));
1488
1489         return mss;
1490 }