2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994
3 * The Regents of the University of California. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * @(#)tcp_input.c 8.5 (Berkeley) 4/10/94
34 * tcp_input.c,v 1.10 1994/10/13 18:36:32 wollman Exp
38 * Changes and additions relating to SLiRP
39 * Copyright (c) 1995 Danny Gasparovski.
41 * Please read the file COPYRIGHT for the
42 * terms and conditions of the copyright.
50 #define TCPREXMTTHRESH 3
51 struct socket
*tcp_last_so
= &tcb
;
53 tcp_seq tcp_iss
; /* tcp initial send seq # */
55 #define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ)
57 /* for modulo comparisons of timestamps */
58 #define TSTMP_LT(a,b) ((int)((a)-(b)) < 0)
59 #define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0)
62 * Insert segment ti into reassembly queue of tcp with
63 * control block tp. Return TH_FIN if reassembly now includes
64 * a segment with FIN. The macro form does the common case inline
65 * (segment is the next to be received on an established connection,
66 * and the queue is empty), avoiding linkage into and removal
67 * from the queue and repetition of various conversions.
68 * Set DELACK for segments received in order, but ack immediately
69 * when segments are out of order (so fast retransmit can work).
72 #define TCP_REASS(tp, ti, m, so, flags) {\
73 if ((ti)->ti_seq == (tp)->rcv_nxt && \
74 (tp)->seg_next == (tcpiphdrp_32)(tp) && \
75 (tp)->t_state == TCPS_ESTABLISHED) {\
76 if (ti->ti_flags & TH_PUSH) \
77 tp->t_flags |= TF_ACKNOW; \
79 tp->t_flags |= TF_DELACK; \
80 (tp)->rcv_nxt += (ti)->ti_len; \
81 flags = (ti)->ti_flags & TH_FIN; \
82 STAT(tcpstat.tcps_rcvpack++); \
83 STAT(tcpstat.tcps_rcvbyte += (ti)->ti_len); \
85 if (tcp_emu((so),(m))) sbappend((so), (m)); \
87 sbappend((so), (m)); \
88 /* sorwakeup(so); */ \
90 (flags) = tcp_reass((tp), (ti), (m)); \
91 tp->t_flags |= TF_ACKNOW; \
95 #define TCP_REASS(tp, ti, m, so, flags) { \
96 if ((ti)->ti_seq == (tp)->rcv_nxt && \
97 (tp)->seg_next == (tcpiphdrp_32)(tp) && \
98 (tp)->t_state == TCPS_ESTABLISHED) { \
99 tp->t_flags |= TF_DELACK; \
100 (tp)->rcv_nxt += (ti)->ti_len; \
101 flags = (ti)->ti_flags & TH_FIN; \
102 STAT(tcpstat.tcps_rcvpack++); \
103 STAT(tcpstat.tcps_rcvbyte += (ti)->ti_len); \
105 if (tcp_emu((so),(m))) sbappend(so, (m)); \
107 sbappend((so), (m)); \
108 /* sorwakeup(so); */ \
110 (flags) = tcp_reass((tp), (ti), (m)); \
111 tp->t_flags |= TF_ACKNOW; \
115 static void tcp_dooptions(struct tcpcb
*tp
, u_char
*cp
, int cnt
,
116 struct tcpiphdr
*ti
);
117 static void tcp_xmit_timer(register struct tcpcb
*tp
, int rtt
);
120 tcp_reass(register struct tcpcb
*tp
, register struct tcpiphdr
*ti
,
123 register struct tcpiphdr
*q
;
124 struct socket
*so
= tp
->t_socket
;
128 * Call with ti==0 after become established to
129 * force pre-ESTABLISHED data up to user socket.
135 * Find a segment which begins after this one does.
137 for (q
= (struct tcpiphdr
*)tp
->seg_next
; q
!= (struct tcpiphdr
*)tp
;
138 q
= (struct tcpiphdr
*)q
->ti_next
)
139 if (SEQ_GT(q
->ti_seq
, ti
->ti_seq
))
143 * If there is a preceding segment, it may provide some of
144 * our data already. If so, drop the data from the incoming
145 * segment. If it provides all of our data, drop us.
147 if ((struct tcpiphdr
*)q
->ti_prev
!= (struct tcpiphdr
*)tp
) {
149 q
= (struct tcpiphdr
*)q
->ti_prev
;
150 /* conversion to int (in i) handles seq wraparound */
151 i
= q
->ti_seq
+ q
->ti_len
- ti
->ti_seq
;
153 if (i
>= ti
->ti_len
) {
154 STAT(tcpstat
.tcps_rcvduppack
++);
155 STAT(tcpstat
.tcps_rcvdupbyte
+= ti
->ti_len
);
158 * Try to present any queued data
159 * at the left window edge to the user.
160 * This is needed after the 3-WHS
163 goto present
; /* ??? */
169 q
= (struct tcpiphdr
*)(q
->ti_next
);
171 STAT(tcpstat
.tcps_rcvoopack
++);
172 STAT(tcpstat
.tcps_rcvoobyte
+= ti
->ti_len
);
173 REASS_MBUF(ti
) = (mbufp_32
) m
; /* XXX */
176 * While we overlap succeeding segments trim them or,
177 * if they are completely covered, dequeue them.
179 while (q
!= (struct tcpiphdr
*)tp
) {
180 register int i
= (ti
->ti_seq
+ ti
->ti_len
) - q
->ti_seq
;
186 m_adj((struct mbuf
*) REASS_MBUF(q
), i
);
189 q
= (struct tcpiphdr
*)q
->ti_next
;
190 m
= (struct mbuf
*) REASS_MBUF((struct tcpiphdr
*)q
->ti_prev
);
191 remque_32((void *)(q
->ti_prev
));
196 * Stick new segment in its place.
198 insque_32(ti
, (void *)(q
->ti_prev
));
202 * Present data to user, advancing rcv_nxt through
203 * completed sequence space.
205 if (!TCPS_HAVEESTABLISHED(tp
->t_state
))
207 ti
= (struct tcpiphdr
*) tp
->seg_next
;
208 if (ti
== (struct tcpiphdr
*)tp
|| ti
->ti_seq
!= tp
->rcv_nxt
)
210 if (tp
->t_state
== TCPS_SYN_RECEIVED
&& ti
->ti_len
)
213 tp
->rcv_nxt
+= ti
->ti_len
;
214 flags
= ti
->ti_flags
& TH_FIN
;
216 m
= (struct mbuf
*) REASS_MBUF(ti
); /* XXX */
217 ti
= (struct tcpiphdr
*)ti
->ti_next
;
218 /* if (so->so_state & SS_FCANTRCVMORE) */
219 if (so
->so_state
& SS_FCANTSENDMORE
)
223 if (tcp_emu(so
,m
)) sbappend(so
, m
);
227 } while (ti
!= (struct tcpiphdr
*)tp
&& ti
->ti_seq
== tp
->rcv_nxt
);
233 * TCP input routine, follows pages 65-76 of the
234 * protocol specification dated September, 1981 very closely.
237 tcp_input(m
, iphlen
, inso
)
238 register struct mbuf
*m
;
242 struct ip save_ip
, *ip
;
243 register struct tcpiphdr
*ti
;
247 register struct tcpcb
*tp
= 0;
248 register int tiflags
;
249 struct socket
*so
= 0;
250 int todrop
, acked
, ourfinisacked
, needoutput
= 0;
251 /* int dropsocket = 0; */
255 /* int ts_present = 0; */
257 DEBUG_CALL("tcp_input");
258 DEBUG_ARGS((dfd
," m = %8lx iphlen = %2d inso = %lx\n",
259 (long )m
, iphlen
, (long )inso
));
262 * If called with m == 0, then we're continuing the connect
267 /* Re-set a few variables */
273 tiflags
= ti
->ti_flags
;
279 STAT(tcpstat
.tcps_rcvtotal
++);
281 * Get IP and TCP header together in first mbuf.
282 * Note: IP leaves IP header in first mbuf.
284 ti
= mtod(m
, struct tcpiphdr
*);
285 if (iphlen
> sizeof(struct ip
)) {
286 ip_stripoptions(m
, (struct mbuf
*)0);
287 iphlen
=sizeof(struct ip
);
289 /* XXX Check if too short */
293 * Save a copy of the IP header in case we want restore it
294 * for sending an ICMP error message in response.
296 ip
=mtod(m
, struct ip
*);
298 save_ip
.ip_len
+= iphlen
;
301 * Checksum extended TCP header and data.
303 tlen
= ((struct ip
*)ti
)->ip_len
;
304 ti
->ti_next
= ti
->ti_prev
= 0;
306 ti
->ti_len
= htons((u_int16_t
)tlen
);
307 len
= sizeof(struct ip
) + tlen
;
308 /* keep checksum for ICMP reply
309 * ti->ti_sum = cksum(m, len);
310 * if (ti->ti_sum) { */
312 STAT(tcpstat
.tcps_rcvbadsum
++);
317 * Check that TCP offset makes sense,
318 * pull out TCP options and adjust length. XXX
320 off
= ti
->ti_off
<< 2;
321 if (off
< sizeof (struct tcphdr
) || off
> tlen
) {
322 STAT(tcpstat
.tcps_rcvbadoff
++);
327 if (off
> sizeof (struct tcphdr
)) {
328 optlen
= off
- sizeof (struct tcphdr
);
329 optp
= mtod(m
, caddr_t
) + sizeof (struct tcpiphdr
);
332 * Do quick retrieval of timestamp options ("options
333 * prediction?"). If timestamp is the only option and it's
334 * formatted as recommended in RFC 1323 appendix A, we
335 * quickly get the values now and not bother calling
336 * tcp_dooptions(), etc.
338 /* if ((optlen == TCPOLEN_TSTAMP_APPA ||
339 * (optlen > TCPOLEN_TSTAMP_APPA &&
340 * optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) &&
341 * *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) &&
342 * (ti->ti_flags & TH_SYN) == 0) {
344 * ts_val = ntohl(*(u_int32_t *)(optp + 4));
345 * ts_ecr = ntohl(*(u_int32_t *)(optp + 8));
346 * optp = NULL; / * we've parsed the options * /
350 tiflags
= ti
->ti_flags
;
353 * Convert TCP protocol specific fields to host format.
361 * Drop TCP, IP headers and TCP options.
363 m
->m_data
+= sizeof(struct tcpiphdr
)+off
-sizeof(struct tcphdr
);
364 m
->m_len
-= sizeof(struct tcpiphdr
)+off
-sizeof(struct tcphdr
);
367 * Locate pcb for segment.
371 if (so
->so_fport
!= ti
->ti_dport
||
372 so
->so_lport
!= ti
->ti_sport
||
373 so
->so_laddr
.s_addr
!= ti
->ti_src
.s_addr
||
374 so
->so_faddr
.s_addr
!= ti
->ti_dst
.s_addr
) {
375 so
= solookup(&tcb
, ti
->ti_src
, ti
->ti_sport
,
376 ti
->ti_dst
, ti
->ti_dport
);
379 STAT(tcpstat
.tcps_socachemiss
++);
383 * If the state is CLOSED (i.e., TCB does not exist) then
384 * all data in the incoming segment is discarded.
385 * If the TCB exists but is in CLOSED state, it is embryonic,
386 * but should either do a listen or a connect soon.
388 * state == CLOSED means we've done socreate() but haven't
389 * attached it to a protocol yet...
391 * XXX If a TCB does not exist, and the TH_SYN flag is
392 * the only flag set, then create a session, mark it
393 * as if it was LISTENING, and continue...
396 if ((tiflags
& (TH_SYN
|TH_FIN
|TH_RST
|TH_URG
|TH_ACK
)) != TH_SYN
)
399 if ((so
= socreate()) == NULL
)
401 if (tcp_attach(so
) < 0) {
402 free(so
); /* Not sofree (if it failed, it's not insqued) */
406 sbreserve(&so
->so_snd
, TCP_SNDSPACE
);
407 sbreserve(&so
->so_rcv
, TCP_RCVSPACE
);
409 /* tcp_last_so = so; */ /* XXX ? */
410 /* tp = sototcpcb(so); */
412 so
->so_laddr
= ti
->ti_src
;
413 so
->so_lport
= ti
->ti_sport
;
414 so
->so_faddr
= ti
->ti_dst
;
415 so
->so_fport
= ti
->ti_dport
;
417 if ((so
->so_iptos
= tcp_tos(so
)) == 0)
418 so
->so_iptos
= ((struct ip
*)ti
)->ip_tos
;
421 tp
->t_state
= TCPS_LISTEN
;
425 * If this is a still-connecting socket, this probably
426 * a retransmit of the SYN. Whether it's a retransmit SYN
427 * or something else, we nuke it.
429 if (so
->so_state
& SS_ISFCONNECTING
)
434 /* XXX Should never fail */
437 if (tp
->t_state
== TCPS_CLOSED
)
440 /* Unscale the window into a 32-bit value. */
441 /* if ((tiflags & TH_SYN) == 0)
442 * tiwin = ti->ti_win << tp->snd_scale;
448 * Segment received on connection.
449 * Reset idle time and keep-alive timer.
453 tp
->t_timer
[TCPT_KEEP
] = TCPTV_KEEPINTVL
;
455 tp
->t_timer
[TCPT_KEEP
] = TCPTV_KEEP_IDLE
;
458 * Process options if not in LISTEN state,
459 * else do it below (after getting remote address).
461 if (optp
&& tp
->t_state
!= TCPS_LISTEN
)
462 tcp_dooptions(tp
, (u_char
*)optp
, optlen
, ti
);
464 /* &ts_present, &ts_val, &ts_ecr); */
467 * Header prediction: check for the two common cases
468 * of a uni-directional data xfer. If the packet has
469 * no control flags, is in-sequence, the window didn't
470 * change and we're not retransmitting, it's a
471 * candidate. If the length is zero and the ack moved
472 * forward, we're the sender side of the xfer. Just
473 * free the data acked & wake any higher level process
474 * that was blocked waiting for space. If the length
475 * is non-zero and the ack didn't move, we're the
476 * receiver side. If we're getting packets in-order
477 * (the reassembly queue is empty), add the data to
478 * the socket buffer and note that we need a delayed ack.
480 * XXX Some of these tests are not needed
481 * eg: the tiwin == tp->snd_wnd prevents many more
482 * predictions.. with no *real* advantage..
484 if (tp
->t_state
== TCPS_ESTABLISHED
&&
485 (tiflags
& (TH_SYN
|TH_FIN
|TH_RST
|TH_URG
|TH_ACK
)) == TH_ACK
&&
486 /* (!ts_present || TSTMP_GEQ(ts_val, tp->ts_recent)) && */
487 ti
->ti_seq
== tp
->rcv_nxt
&&
488 tiwin
&& tiwin
== tp
->snd_wnd
&&
489 tp
->snd_nxt
== tp
->snd_max
) {
491 * If last ACK falls within this segment's sequence numbers,
492 * record the timestamp.
494 /* if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
495 * SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) {
496 * tp->ts_recent_age = tcp_now;
497 * tp->ts_recent = ts_val;
500 if (ti
->ti_len
== 0) {
501 if (SEQ_GT(ti
->ti_ack
, tp
->snd_una
) &&
502 SEQ_LEQ(ti
->ti_ack
, tp
->snd_max
) &&
503 tp
->snd_cwnd
>= tp
->snd_wnd
) {
505 * this is a pure ack for outstanding data.
507 STAT(tcpstat
.tcps_predack
++);
509 * tcp_xmit_timer(tp, tcp_now-ts_ecr+1);
512 SEQ_GT(ti
->ti_ack
, tp
->t_rtseq
))
513 tcp_xmit_timer(tp
, tp
->t_rtt
);
514 acked
= ti
->ti_ack
- tp
->snd_una
;
515 STAT(tcpstat
.tcps_rcvackpack
++);
516 STAT(tcpstat
.tcps_rcvackbyte
+= acked
);
517 sbdrop(&so
->so_snd
, acked
);
518 tp
->snd_una
= ti
->ti_ack
;
522 * If all outstanding data are acked, stop
523 * retransmit timer, otherwise restart timer
524 * using current (possibly backed-off) value.
525 * If process is waiting for space,
526 * wakeup/selwakeup/signal. If data
527 * are ready to send, let tcp_output
528 * decide between more output or persist.
530 if (tp
->snd_una
== tp
->snd_max
)
531 tp
->t_timer
[TCPT_REXMT
] = 0;
532 else if (tp
->t_timer
[TCPT_PERSIST
] == 0)
533 tp
->t_timer
[TCPT_REXMT
] = tp
->t_rxtcur
;
536 * There's room in so_snd, sowwakup will read()
537 * from the socket if we can
539 /* if (so->so_snd.sb_flags & SB_NOTIFY)
543 * This is called because sowwakeup might have
544 * put data into so_snd. Since we don't so sowwakeup,
545 * we don't need this.. XXX???
547 if (so
->so_snd
.sb_cc
)
548 (void) tcp_output(tp
);
552 } else if (ti
->ti_ack
== tp
->snd_una
&&
553 tp
->seg_next
== (tcpiphdrp_32
)tp
&&
554 ti
->ti_len
<= sbspace(&so
->so_rcv
)) {
556 * this is a pure, in-sequence data packet
557 * with nothing on the reassembly queue and
558 * we have enough buffer space to take it.
560 STAT(tcpstat
.tcps_preddat
++);
561 tp
->rcv_nxt
+= ti
->ti_len
;
562 STAT(tcpstat
.tcps_rcvpack
++);
563 STAT(tcpstat
.tcps_rcvbyte
+= ti
->ti_len
);
565 * Add data to socket buffer.
568 if (tcp_emu(so
,m
)) sbappend(so
, m
);
573 * XXX This is called when data arrives. Later, check
574 * if we can actually write() to the socket
575 * XXX Need to check? It's be NON_BLOCKING
580 * If this is a short packet, then ACK now - with Nagel
581 * congestion avoidance sender won't send more until
584 * It is better to not delay acks at all to maximize
585 * TCP throughput. See RFC 2581.
587 tp
->t_flags
|= TF_ACKNOW
;
591 } /* header prediction */
593 * Calculate amount of space in receive window,
594 * and then do TCP input processing.
595 * Receive window is amount of space in rcv queue,
596 * but not less than advertised window.
599 win
= sbspace(&so
->so_rcv
);
602 tp
->rcv_wnd
= max(win
, (int)(tp
->rcv_adv
- tp
->rcv_nxt
));
605 switch (tp
->t_state
) {
608 * If the state is LISTEN then ignore segment if it contains an RST.
609 * If the segment contains an ACK then it is bad and send a RST.
610 * If it does not contain a SYN then it is not interesting; drop it.
611 * Don't bother responding if the destination was a broadcast.
612 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
613 * tp->iss, and send a segment:
614 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
615 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
616 * Fill in remote peer address fields if not previously specified.
617 * Enter SYN_RECEIVED state, and process any other fields of this
618 * segment in this state.
622 if (tiflags
& TH_RST
)
624 if (tiflags
& TH_ACK
)
626 if ((tiflags
& TH_SYN
) == 0)
630 * This has way too many gotos...
631 * But a bit of spaghetti code never hurt anybody :)
635 * If this is destined for the control address, then flag to
636 * tcp_ctl once connected, otherwise connect
638 if ((so
->so_faddr
.s_addr
&htonl(0xffffff00)) == special_addr
.s_addr
) {
639 int lastbyte
=ntohl(so
->so_faddr
.s_addr
) & 0xff;
640 if (lastbyte
!=CTL_ALIAS
&& lastbyte
!=CTL_DNS
) {
642 if(lastbyte
==CTL_CMD
|| lastbyte
==CTL_EXEC
) {
643 /* Command or exec adress */
644 so
->so_state
|= SS_CTL
;
648 /* May be an add exec */
649 struct ex_list
*ex_ptr
;
650 for(ex_ptr
= exec_list
; ex_ptr
; ex_ptr
= ex_ptr
->ex_next
) {
651 if(ex_ptr
->ex_fport
== so
->so_fport
&&
652 lastbyte
== ex_ptr
->ex_addr
) {
653 so
->so_state
|= SS_CTL
;
658 if(so
->so_state
& SS_CTL
) goto cont_input
;
660 /* CTL_ALIAS: Do nothing, tcp_fconnect will be called on it */
663 if (so
->so_emu
& EMU_NOCONNECT
) {
664 so
->so_emu
&= ~EMU_NOCONNECT
;
668 if((tcp_fconnect(so
) == -1) && (errno
!= EINPROGRESS
) && (errno
!= EWOULDBLOCK
)) {
669 u_char code
=ICMP_UNREACH_NET
;
670 DEBUG_MISC((dfd
," tcp fconnect errno = %d-%s\n",
671 errno
,strerror(errno
)));
672 if(errno
== ECONNREFUSED
) {
673 /* ACK the SYN, send RST to refuse the connection */
674 tcp_respond(tp
, ti
, m
, ti
->ti_seq
+1, (tcp_seq
)0,
677 if(errno
== EHOSTUNREACH
) code
=ICMP_UNREACH_HOST
;
678 HTONL(ti
->ti_seq
); /* restore tcp header */
682 m
->m_data
-= sizeof(struct tcpiphdr
)+off
-sizeof(struct tcphdr
);
683 m
->m_len
+= sizeof(struct tcpiphdr
)+off
-sizeof(struct tcphdr
);
685 icmp_error(m
, ICMP_UNREACH
,code
, 0,strerror(errno
));
691 * Haven't connected yet, save the current mbuf
693 * XXX Some OS's don't tell us whether the connect()
694 * succeeded or not. So we must time it out.
698 tp
->t_timer
[TCPT_KEEP
] = TCPTV_KEEP_INIT
;
699 tp
->t_state
= TCPS_SYN_RECEIVED
;
705 * Check if the connect succeeded
707 if (so
->so_state
& SS_NOFDREF
) {
715 tcp_dooptions(tp
, (u_char
*)optp
, optlen
, ti
);
717 /* &ts_present, &ts_val, &ts_ecr); */
723 tcp_iss
+= TCP_ISSINCR
/2;
724 tp
->irs
= ti
->ti_seq
;
727 tp
->t_flags
|= TF_ACKNOW
;
728 tp
->t_state
= TCPS_SYN_RECEIVED
;
729 tp
->t_timer
[TCPT_KEEP
] = TCPTV_KEEP_INIT
;
730 STAT(tcpstat
.tcps_accepts
++);
732 } /* case TCPS_LISTEN */
735 * If the state is SYN_SENT:
736 * if seg contains an ACK, but not for our SYN, drop the input.
737 * if seg contains a RST, then drop the connection.
738 * if seg does not contain SYN, then drop it.
739 * Otherwise this is an acceptable SYN segment
740 * initialize tp->rcv_nxt and tp->irs
741 * if seg contains ack then advance tp->snd_una
742 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
743 * arrange for segment to be acked (eventually)
744 * continue processing rest of data/controls, beginning with URG
747 if ((tiflags
& TH_ACK
) &&
748 (SEQ_LEQ(ti
->ti_ack
, tp
->iss
) ||
749 SEQ_GT(ti
->ti_ack
, tp
->snd_max
)))
752 if (tiflags
& TH_RST
) {
753 if (tiflags
& TH_ACK
)
754 tp
= tcp_drop(tp
,0); /* XXX Check t_softerror! */
758 if ((tiflags
& TH_SYN
) == 0)
760 if (tiflags
& TH_ACK
) {
761 tp
->snd_una
= ti
->ti_ack
;
762 if (SEQ_LT(tp
->snd_nxt
, tp
->snd_una
))
763 tp
->snd_nxt
= tp
->snd_una
;
766 tp
->t_timer
[TCPT_REXMT
] = 0;
767 tp
->irs
= ti
->ti_seq
;
769 tp
->t_flags
|= TF_ACKNOW
;
770 if (tiflags
& TH_ACK
&& SEQ_GT(tp
->snd_una
, tp
->iss
)) {
771 STAT(tcpstat
.tcps_connects
++);
773 tp
->t_state
= TCPS_ESTABLISHED
;
775 /* Do window scaling on this connection? */
776 /* if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
777 * (TF_RCVD_SCALE|TF_REQ_SCALE)) {
778 * tp->snd_scale = tp->requested_s_scale;
779 * tp->rcv_scale = tp->request_r_scale;
782 (void) tcp_reass(tp
, (struct tcpiphdr
*)0,
785 * if we didn't have to retransmit the SYN,
786 * use its rtt as our initial srtt & rtt var.
789 tcp_xmit_timer(tp
, tp
->t_rtt
);
791 tp
->t_state
= TCPS_SYN_RECEIVED
;
795 * Advance ti->ti_seq to correspond to first data byte.
796 * If data, trim to stay within window,
797 * dropping FIN if necessary.
800 if (ti
->ti_len
> tp
->rcv_wnd
) {
801 todrop
= ti
->ti_len
- tp
->rcv_wnd
;
803 ti
->ti_len
= tp
->rcv_wnd
;
805 STAT(tcpstat
.tcps_rcvpackafterwin
++);
806 STAT(tcpstat
.tcps_rcvbyteafterwin
+= todrop
);
808 tp
->snd_wl1
= ti
->ti_seq
- 1;
809 tp
->rcv_up
= ti
->ti_seq
;
811 } /* switch tp->t_state */
813 * States other than LISTEN or SYN_SENT.
814 * First check timestamp, if present.
815 * Then check that at least some bytes of segment are within
816 * receive window. If segment begins before rcv_nxt,
817 * drop leading data (and SYN); if nothing left, just ack.
819 * RFC 1323 PAWS: If we have a timestamp reply on this segment
820 * and it's less than ts_recent, drop it.
822 /* if (ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent &&
823 * TSTMP_LT(ts_val, tp->ts_recent)) {
825 */ /* Check to see if ts_recent is over 24 days old. */
826 /* if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) {
828 * * Invalidate ts_recent. If this segment updates
829 * * ts_recent, the age will be reset later and ts_recent
830 * * will get a valid value. If it does not, setting
831 * * ts_recent to zero will at least satisfy the
832 * * requirement that zero be placed in the timestamp
833 * * echo reply when ts_recent isn't valid. The
834 * * age isn't reset until we get a valid ts_recent
835 * * because we don't want out-of-order segments to be
836 * * dropped when ts_recent is old.
838 /* tp->ts_recent = 0;
840 * tcpstat.tcps_rcvduppack++;
841 * tcpstat.tcps_rcvdupbyte += ti->ti_len;
842 * tcpstat.tcps_pawsdrop++;
848 todrop
= tp
->rcv_nxt
- ti
->ti_seq
;
850 if (tiflags
& TH_SYN
) {
860 * Following if statement from Stevens, vol. 2, p. 960.
862 if (todrop
> ti
->ti_len
863 || (todrop
== ti
->ti_len
&& (tiflags
& TH_FIN
) == 0)) {
865 * Any valid FIN must be to the left of the window.
866 * At this point the FIN must be a duplicate or out
867 * of sequence; drop it.
872 * Send an ACK to resynchronize and drop any data.
873 * But keep on processing for RST or ACK.
875 tp
->t_flags
|= TF_ACKNOW
;
877 STAT(tcpstat
.tcps_rcvduppack
++);
878 STAT(tcpstat
.tcps_rcvdupbyte
+= todrop
);
880 STAT(tcpstat
.tcps_rcvpartduppack
++);
881 STAT(tcpstat
.tcps_rcvpartdupbyte
+= todrop
);
884 ti
->ti_seq
+= todrop
;
885 ti
->ti_len
-= todrop
;
886 if (ti
->ti_urp
> todrop
)
887 ti
->ti_urp
-= todrop
;
894 * If new data are received on a connection after the
895 * user processes are gone, then RST the other end.
897 if ((so
->so_state
& SS_NOFDREF
) &&
898 tp
->t_state
> TCPS_CLOSE_WAIT
&& ti
->ti_len
) {
900 STAT(tcpstat
.tcps_rcvafterclose
++);
905 * If segment ends after window, drop trailing data
906 * (and PUSH and FIN); if nothing left, just ACK.
908 todrop
= (ti
->ti_seq
+ti
->ti_len
) - (tp
->rcv_nxt
+tp
->rcv_wnd
);
910 STAT(tcpstat
.tcps_rcvpackafterwin
++);
911 if (todrop
>= ti
->ti_len
) {
912 STAT(tcpstat
.tcps_rcvbyteafterwin
+= ti
->ti_len
);
914 * If a new connection request is received
915 * while in TIME_WAIT, drop the old connection
916 * and start over if the sequence numbers
917 * are above the previous ones.
919 if (tiflags
& TH_SYN
&&
920 tp
->t_state
== TCPS_TIME_WAIT
&&
921 SEQ_GT(ti
->ti_seq
, tp
->rcv_nxt
)) {
922 iss
= tp
->rcv_nxt
+ TCP_ISSINCR
;
927 * If window is closed can only take segments at
928 * window edge, and have to drop data and PUSH from
929 * incoming segments. Continue processing, but
930 * remember to ack. Otherwise, drop segment
933 if (tp
->rcv_wnd
== 0 && ti
->ti_seq
== tp
->rcv_nxt
) {
934 tp
->t_flags
|= TF_ACKNOW
;
935 STAT(tcpstat
.tcps_rcvwinprobe
++);
939 STAT(tcpstat
.tcps_rcvbyteafterwin
+= todrop
);
941 ti
->ti_len
-= todrop
;
942 tiflags
&= ~(TH_PUSH
|TH_FIN
);
946 * If last ACK falls within this segment's sequence numbers,
947 * record its timestamp.
949 /* if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
950 * SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len +
951 * ((tiflags & (TH_SYN|TH_FIN)) != 0))) {
952 * tp->ts_recent_age = tcp_now;
953 * tp->ts_recent = ts_val;
958 * If the RST bit is set examine the state:
959 * SYN_RECEIVED STATE:
960 * If passive open, return to LISTEN state.
961 * If active open, inform user that connection was refused.
962 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
963 * Inform user that connection was reset, and close tcb.
964 * CLOSING, LAST_ACK, TIME_WAIT STATES
967 if (tiflags
&TH_RST
) switch (tp
->t_state
) {
969 case TCPS_SYN_RECEIVED
:
970 /* so->so_error = ECONNREFUSED; */
973 case TCPS_ESTABLISHED
:
974 case TCPS_FIN_WAIT_1
:
975 case TCPS_FIN_WAIT_2
:
976 case TCPS_CLOSE_WAIT
:
977 /* so->so_error = ECONNRESET; */
979 tp
->t_state
= TCPS_CLOSED
;
980 STAT(tcpstat
.tcps_drops
++);
992 * If a SYN is in the window, then this is an
993 * error and we send an RST and drop the connection.
995 if (tiflags
& TH_SYN
) {
1001 * If the ACK bit is off we drop the segment and return.
1003 if ((tiflags
& TH_ACK
) == 0) goto drop
;
1008 switch (tp
->t_state
) {
1010 * In SYN_RECEIVED state if the ack ACKs our SYN then enter
1011 * ESTABLISHED state and continue processing, otherwise
1012 * send an RST. una<=ack<=max
1014 case TCPS_SYN_RECEIVED
:
1016 if (SEQ_GT(tp
->snd_una
, ti
->ti_ack
) ||
1017 SEQ_GT(ti
->ti_ack
, tp
->snd_max
))
1019 STAT(tcpstat
.tcps_connects
++);
1020 tp
->t_state
= TCPS_ESTABLISHED
;
1022 * The sent SYN is ack'ed with our sequence number +1
1023 * The first data byte already in the buffer will get
1024 * lost if no correction is made. This is only needed for
1025 * SS_CTL since the buffer is empty otherwise.
1026 * tp->snd_una++; or:
1028 tp
->snd_una
=ti
->ti_ack
;
1029 if (so
->so_state
& SS_CTL
) {
1030 /* So tcp_ctl reports the right state */
1034 so
->so_state
&= ~SS_CTL
; /* success XXX */
1035 } else if (ret
== 2) {
1036 so
->so_state
= SS_NOFDREF
; /* CTL_CMD */
1039 tp
->t_state
= TCPS_FIN_WAIT_1
;
1045 /* Do window scaling? */
1046 /* if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1047 * (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1048 * tp->snd_scale = tp->requested_s_scale;
1049 * tp->rcv_scale = tp->request_r_scale;
1052 (void) tcp_reass(tp
, (struct tcpiphdr
*)0, (struct mbuf
*)0);
1053 tp
->snd_wl1
= ti
->ti_seq
- 1;
1054 /* Avoid ack processing; snd_una==ti_ack => dup ack */
1059 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1060 * ACKs. If the ack is in the range
1061 * tp->snd_una < ti->ti_ack <= tp->snd_max
1062 * then advance tp->snd_una to ti->ti_ack and drop
1063 * data from the retransmission queue. If this ACK reflects
1064 * more up to date window information we update our window information.
1066 case TCPS_ESTABLISHED
:
1067 case TCPS_FIN_WAIT_1
:
1068 case TCPS_FIN_WAIT_2
:
1069 case TCPS_CLOSE_WAIT
:
1072 case TCPS_TIME_WAIT
:
1074 if (SEQ_LEQ(ti
->ti_ack
, tp
->snd_una
)) {
1075 if (ti
->ti_len
== 0 && tiwin
== tp
->snd_wnd
) {
1076 STAT(tcpstat
.tcps_rcvdupack
++);
1077 DEBUG_MISC((dfd
," dup ack m = %lx so = %lx \n",
1078 (long )m
, (long )so
));
1080 * If we have outstanding data (other than
1081 * a window probe), this is a completely
1082 * duplicate ack (ie, window info didn't
1083 * change), the ack is the biggest we've
1084 * seen and we've seen exactly our rexmt
1085 * threshold of them, assume a packet
1086 * has been dropped and retransmit it.
1087 * Kludge snd_nxt & the congestion
1088 * window so we send only this one
1091 * We know we're losing at the current
1092 * window size so do congestion avoidance
1093 * (set ssthresh to half the current window
1094 * and pull our congestion window back to
1095 * the new ssthresh).
1097 * Dup acks mean that packets have left the
1098 * network (they're now cached at the receiver)
1099 * so bump cwnd by the amount in the receiver
1100 * to keep a constant cwnd packets in the
1103 if (tp
->t_timer
[TCPT_REXMT
] == 0 ||
1104 ti
->ti_ack
!= tp
->snd_una
)
1106 else if (++tp
->t_dupacks
== TCPREXMTTHRESH
) {
1107 tcp_seq onxt
= tp
->snd_nxt
;
1109 min(tp
->snd_wnd
, tp
->snd_cwnd
) / 2 /
1114 tp
->snd_ssthresh
= win
* tp
->t_maxseg
;
1115 tp
->t_timer
[TCPT_REXMT
] = 0;
1117 tp
->snd_nxt
= ti
->ti_ack
;
1118 tp
->snd_cwnd
= tp
->t_maxseg
;
1119 (void) tcp_output(tp
);
1120 tp
->snd_cwnd
= tp
->snd_ssthresh
+
1121 tp
->t_maxseg
* tp
->t_dupacks
;
1122 if (SEQ_GT(onxt
, tp
->snd_nxt
))
1125 } else if (tp
->t_dupacks
> TCPREXMTTHRESH
) {
1126 tp
->snd_cwnd
+= tp
->t_maxseg
;
1127 (void) tcp_output(tp
);
1136 * If the congestion window was inflated to account
1137 * for the other side's cached packets, retract it.
1139 if (tp
->t_dupacks
> TCPREXMTTHRESH
&&
1140 tp
->snd_cwnd
> tp
->snd_ssthresh
)
1141 tp
->snd_cwnd
= tp
->snd_ssthresh
;
1143 if (SEQ_GT(ti
->ti_ack
, tp
->snd_max
)) {
1144 STAT(tcpstat
.tcps_rcvacktoomuch
++);
1147 acked
= ti
->ti_ack
- tp
->snd_una
;
1148 STAT(tcpstat
.tcps_rcvackpack
++);
1149 STAT(tcpstat
.tcps_rcvackbyte
+= acked
);
1152 * If we have a timestamp reply, update smoothed
1153 * round trip time. If no timestamp is present but
1154 * transmit timer is running and timed sequence
1155 * number was acked, update smoothed round trip time.
1156 * Since we now have an rtt measurement, cancel the
1157 * timer backoff (cf., Phil Karn's retransmit alg.).
1158 * Recompute the initial retransmit timer.
1161 * tcp_xmit_timer(tp, tcp_now-ts_ecr+1);
1164 if (tp
->t_rtt
&& SEQ_GT(ti
->ti_ack
, tp
->t_rtseq
))
1165 tcp_xmit_timer(tp
,tp
->t_rtt
);
1168 * If all outstanding data is acked, stop retransmit
1169 * timer and remember to restart (more output or persist).
1170 * If there is more data to be acked, restart retransmit
1171 * timer, using current (possibly backed-off) value.
1173 if (ti
->ti_ack
== tp
->snd_max
) {
1174 tp
->t_timer
[TCPT_REXMT
] = 0;
1176 } else if (tp
->t_timer
[TCPT_PERSIST
] == 0)
1177 tp
->t_timer
[TCPT_REXMT
] = tp
->t_rxtcur
;
1179 * When new data is acked, open the congestion window.
1180 * If the window gives us less than ssthresh packets
1181 * in flight, open exponentially (maxseg per packet).
1182 * Otherwise open linearly: maxseg per window
1183 * (maxseg^2 / cwnd per packet).
1186 register u_int cw
= tp
->snd_cwnd
;
1187 register u_int incr
= tp
->t_maxseg
;
1189 if (cw
> tp
->snd_ssthresh
)
1190 incr
= incr
* incr
/ cw
;
1191 tp
->snd_cwnd
= min(cw
+ incr
, TCP_MAXWIN
<<tp
->snd_scale
);
1193 if (acked
> so
->so_snd
.sb_cc
) {
1194 tp
->snd_wnd
-= so
->so_snd
.sb_cc
;
1195 sbdrop(&so
->so_snd
, (int )so
->so_snd
.sb_cc
);
1198 sbdrop(&so
->so_snd
, acked
);
1199 tp
->snd_wnd
-= acked
;
1203 * XXX sowwakup is called when data is acked and there's room for
1204 * for more data... it should read() the socket
1206 /* if (so->so_snd.sb_flags & SB_NOTIFY)
1209 tp
->snd_una
= ti
->ti_ack
;
1210 if (SEQ_LT(tp
->snd_nxt
, tp
->snd_una
))
1211 tp
->snd_nxt
= tp
->snd_una
;
1213 switch (tp
->t_state
) {
1216 * In FIN_WAIT_1 STATE in addition to the processing
1217 * for the ESTABLISHED state if our FIN is now acknowledged
1218 * then enter FIN_WAIT_2.
1220 case TCPS_FIN_WAIT_1
:
1221 if (ourfinisacked
) {
1223 * If we can't receive any more
1224 * data, then closing user can proceed.
1225 * Starting the timer is contrary to the
1226 * specification, but if we don't get a FIN
1227 * we'll hang forever.
1229 if (so
->so_state
& SS_FCANTRCVMORE
) {
1230 soisfdisconnected(so
);
1231 tp
->t_timer
[TCPT_2MSL
] = TCP_MAXIDLE
;
1233 tp
->t_state
= TCPS_FIN_WAIT_2
;
1238 * In CLOSING STATE in addition to the processing for
1239 * the ESTABLISHED state if the ACK acknowledges our FIN
1240 * then enter the TIME-WAIT state, otherwise ignore
1244 if (ourfinisacked
) {
1245 tp
->t_state
= TCPS_TIME_WAIT
;
1246 tcp_canceltimers(tp
);
1247 tp
->t_timer
[TCPT_2MSL
] = 2 * TCPTV_MSL
;
1248 soisfdisconnected(so
);
1253 * In LAST_ACK, we may still be waiting for data to drain
1254 * and/or to be acked, as well as for the ack of our FIN.
1255 * If our FIN is now acknowledged, delete the TCB,
1256 * enter the closed state and return.
1259 if (ourfinisacked
) {
1266 * In TIME_WAIT state the only thing that should arrive
1267 * is a retransmission of the remote FIN. Acknowledge
1268 * it and restart the finack timer.
1270 case TCPS_TIME_WAIT
:
1271 tp
->t_timer
[TCPT_2MSL
] = 2 * TCPTV_MSL
;
1274 } /* switch(tp->t_state) */
1278 * Update window information.
1279 * Don't look at window if no ACK: TAC's send garbage on first SYN.
1281 if ((tiflags
& TH_ACK
) &&
1282 (SEQ_LT(tp
->snd_wl1
, ti
->ti_seq
) ||
1283 (tp
->snd_wl1
== ti
->ti_seq
&& (SEQ_LT(tp
->snd_wl2
, ti
->ti_ack
) ||
1284 (tp
->snd_wl2
== ti
->ti_ack
&& tiwin
> tp
->snd_wnd
))))) {
1285 /* keep track of pure window updates */
1286 if (ti
->ti_len
== 0 &&
1287 tp
->snd_wl2
== ti
->ti_ack
&& tiwin
> tp
->snd_wnd
)
1288 STAT(tcpstat
.tcps_rcvwinupd
++);
1289 tp
->snd_wnd
= tiwin
;
1290 tp
->snd_wl1
= ti
->ti_seq
;
1291 tp
->snd_wl2
= ti
->ti_ack
;
1292 if (tp
->snd_wnd
> tp
->max_sndwnd
)
1293 tp
->max_sndwnd
= tp
->snd_wnd
;
1298 * Process segments with URG.
1300 if ((tiflags
& TH_URG
) && ti
->ti_urp
&&
1301 TCPS_HAVERCVDFIN(tp
->t_state
) == 0) {
1303 * This is a kludge, but if we receive and accept
1304 * random urgent pointers, we'll crash in
1305 * soreceive. It's hard to imagine someone
1306 * actually wanting to send this much urgent data.
1308 if (ti
->ti_urp
+ so
->so_rcv
.sb_cc
> so
->so_rcv
.sb_datalen
) {
1314 * If this segment advances the known urgent pointer,
1315 * then mark the data stream. This should not happen
1316 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
1317 * a FIN has been received from the remote side.
1318 * In these states we ignore the URG.
1320 * According to RFC961 (Assigned Protocols),
1321 * the urgent pointer points to the last octet
1322 * of urgent data. We continue, however,
1323 * to consider it to indicate the first octet
1324 * of data past the urgent section as the original
1325 * spec states (in one of two places).
1327 if (SEQ_GT(ti
->ti_seq
+ti
->ti_urp
, tp
->rcv_up
)) {
1328 tp
->rcv_up
= ti
->ti_seq
+ ti
->ti_urp
;
1329 so
->so_urgc
= so
->so_rcv
.sb_cc
+
1330 (tp
->rcv_up
- tp
->rcv_nxt
); /* -1; */
1331 tp
->rcv_up
= ti
->ti_seq
+ ti
->ti_urp
;
1336 * If no out of band data is expected,
1337 * pull receive urgent pointer along
1338 * with the receive window.
1340 if (SEQ_GT(tp
->rcv_nxt
, tp
->rcv_up
))
1341 tp
->rcv_up
= tp
->rcv_nxt
;
1345 * Process the segment text, merging it into the TCP sequencing queue,
1346 * and arranging for acknowledgment of receipt if necessary.
1347 * This process logically involves adjusting tp->rcv_wnd as data
1348 * is presented to the user (this happens in tcp_usrreq.c,
1349 * case PRU_RCVD). If a FIN has already been received on this
1350 * connection then we just ignore the text.
1352 if ((ti
->ti_len
|| (tiflags
&TH_FIN
)) &&
1353 TCPS_HAVERCVDFIN(tp
->t_state
) == 0) {
1354 TCP_REASS(tp
, ti
, m
, so
, tiflags
);
1356 * Note the amount of data that peer has sent into
1357 * our window, in order to estimate the sender's
1360 len
= so
->so_rcv
.sb_datalen
- (tp
->rcv_adv
- tp
->rcv_nxt
);
1367 * If FIN is received ACK the FIN and let the user know
1368 * that the connection is closing.
1370 if (tiflags
& TH_FIN
) {
1371 if (TCPS_HAVERCVDFIN(tp
->t_state
) == 0) {
1373 * If we receive a FIN we can't send more data,
1375 * Shutdown the socket if there is no rx data in the
1377 * soread() is called on completion of shutdown() and
1378 * will got to TCPS_LAST_ACK, and use tcp_output()
1381 /* sofcantrcvmore(so); */
1384 tp
->t_flags
|= TF_ACKNOW
;
1387 switch (tp
->t_state
) {
1390 * In SYN_RECEIVED and ESTABLISHED STATES
1391 * enter the CLOSE_WAIT state.
1393 case TCPS_SYN_RECEIVED
:
1394 case TCPS_ESTABLISHED
:
1395 if(so
->so_emu
== EMU_CTL
) /* no shutdown on socket */
1396 tp
->t_state
= TCPS_LAST_ACK
;
1398 tp
->t_state
= TCPS_CLOSE_WAIT
;
1402 * If still in FIN_WAIT_1 STATE FIN has not been acked so
1403 * enter the CLOSING state.
1405 case TCPS_FIN_WAIT_1
:
1406 tp
->t_state
= TCPS_CLOSING
;
1410 * In FIN_WAIT_2 state enter the TIME_WAIT state,
1411 * starting the time-wait timer, turning off the other
1414 case TCPS_FIN_WAIT_2
:
1415 tp
->t_state
= TCPS_TIME_WAIT
;
1416 tcp_canceltimers(tp
);
1417 tp
->t_timer
[TCPT_2MSL
] = 2 * TCPTV_MSL
;
1418 soisfdisconnected(so
);
1422 * In TIME_WAIT state restart the 2 MSL time_wait timer.
1424 case TCPS_TIME_WAIT
:
1425 tp
->t_timer
[TCPT_2MSL
] = 2 * TCPTV_MSL
;
1431 * If this is a small packet, then ACK now - with Nagel
1432 * congestion avoidance sender won't send more until
1437 /* if (ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg) {
1439 /* if ((ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg &&
1440 * (so->so_iptos & IPTOS_LOWDELAY) == 0) ||
1441 * ((so->so_iptos & IPTOS_LOWDELAY) &&
1442 * ((struct tcpiphdr_2 *)ti)->first_char == (char)27)) {
1444 if (ti
->ti_len
&& (unsigned)ti
->ti_len
<= 5 &&
1445 ((struct tcpiphdr_2
*)ti
)->first_char
== (char)27) {
1446 tp
->t_flags
|= TF_ACKNOW
;
1450 * Return any desired output.
1452 if (needoutput
|| (tp
->t_flags
& TF_ACKNOW
)) {
1453 (void) tcp_output(tp
);
1459 * Generate an ACK dropping incoming segment if it occupies
1460 * sequence space, where the ACK reflects our state.
1462 if (tiflags
& TH_RST
)
1465 tp
->t_flags
|= TF_ACKNOW
;
1466 (void) tcp_output(tp
);
1470 /* reuses m if m!=NULL, m_free() unnecessary */
1471 if (tiflags
& TH_ACK
)
1472 tcp_respond(tp
, ti
, m
, (tcp_seq
)0, ti
->ti_ack
, TH_RST
);
1474 if (tiflags
& TH_SYN
) ti
->ti_len
++;
1475 tcp_respond(tp
, ti
, m
, ti
->ti_seq
+ti
->ti_len
, (tcp_seq
)0,
1483 * Drop space held by incoming segment and return.
1490 /* , ts_present, ts_val, ts_ecr) */
1492 * u_int32_t *ts_val, *ts_ecr;
1495 tcp_dooptions(struct tcpcb
*tp
, u_char
*cp
, int cnt
, struct tcpiphdr
*ti
)
1500 DEBUG_CALL("tcp_dooptions");
1501 DEBUG_ARGS((dfd
," tp = %lx cnt=%i \n", (long )tp
, cnt
));
1503 for (; cnt
> 0; cnt
-= optlen
, cp
+= optlen
) {
1505 if (opt
== TCPOPT_EOL
)
1507 if (opt
== TCPOPT_NOP
)
1520 if (optlen
!= TCPOLEN_MAXSEG
)
1522 if (!(ti
->ti_flags
& TH_SYN
))
1524 memcpy((char *) &mss
, (char *) cp
+ 2, sizeof(mss
));
1526 (void) tcp_mss(tp
, mss
); /* sets t_maxseg */
1529 /* case TCPOPT_WINDOW:
1530 * if (optlen != TCPOLEN_WINDOW)
1532 * if (!(ti->ti_flags & TH_SYN))
1534 * tp->t_flags |= TF_RCVD_SCALE;
1535 * tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
1538 /* case TCPOPT_TIMESTAMP:
1539 * if (optlen != TCPOLEN_TIMESTAMP)
1542 * memcpy((char *) ts_val, (char *)cp + 2, sizeof(*ts_val));
1544 * memcpy((char *) ts_ecr, (char *)cp + 6, sizeof(*ts_ecr));
1548 * * A timestamp received in a SYN makes
1549 * * it ok to send timestamp requests and replies.
1551 /* if (ti->ti_flags & TH_SYN) {
1552 * tp->t_flags |= TF_RCVD_TSTMP;
1553 * tp->ts_recent = *ts_val;
1554 * tp->ts_recent_age = tcp_now;
1563 * Pull out of band byte out of a segment so
1564 * it doesn't appear in the user's data queue.
1565 * It is still reflected in the segment length for
1566 * sequencing purposes.
1572 tcp_pulloutofband(so
, ti
, m
)
1574 struct tcpiphdr
*ti
;
1575 register struct mbuf
*m
;
1577 int cnt
= ti
->ti_urp
- 1;
1580 if (m
->m_len
> cnt
) {
1581 char *cp
= mtod(m
, caddr_t
) + cnt
;
1582 struct tcpcb
*tp
= sototcpcb(so
);
1585 tp
->t_oobflags
|= TCPOOB_HAVEDATA
;
1586 memcpy(sp
, cp
+1, (unsigned)(m
->m_len
- cnt
- 1));
1591 m
= m
->m_next
; /* XXX WRONG! Fix it! */
1595 panic("tcp_pulloutofband");
1601 * Collect new round-trip time estimate
1602 * and update averages and current timeout.
1606 tcp_xmit_timer(register struct tcpcb
*tp
, int rtt
)
1608 register short delta
;
1610 DEBUG_CALL("tcp_xmit_timer");
1611 DEBUG_ARG("tp = %lx", (long)tp
);
1612 DEBUG_ARG("rtt = %d", rtt
);
1614 STAT(tcpstat
.tcps_rttupdated
++);
1615 if (tp
->t_srtt
!= 0) {
1617 * srtt is stored as fixed point with 3 bits after the
1618 * binary point (i.e., scaled by 8). The following magic
1619 * is equivalent to the smoothing algorithm in rfc793 with
1620 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
1621 * point). Adjust rtt to origin 0.
1623 delta
= rtt
- 1 - (tp
->t_srtt
>> TCP_RTT_SHIFT
);
1624 if ((tp
->t_srtt
+= delta
) <= 0)
1627 * We accumulate a smoothed rtt variance (actually, a
1628 * smoothed mean difference), then set the retransmit
1629 * timer to smoothed rtt + 4 times the smoothed variance.
1630 * rttvar is stored as fixed point with 2 bits after the
1631 * binary point (scaled by 4). The following is
1632 * equivalent to rfc793 smoothing with an alpha of .75
1633 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
1634 * rfc793's wired-in beta.
1638 delta
-= (tp
->t_rttvar
>> TCP_RTTVAR_SHIFT
);
1639 if ((tp
->t_rttvar
+= delta
) <= 0)
1643 * No rtt measurement yet - use the unsmoothed rtt.
1644 * Set the variance to half the rtt (so our first
1645 * retransmit happens at 3*rtt).
1647 tp
->t_srtt
= rtt
<< TCP_RTT_SHIFT
;
1648 tp
->t_rttvar
= rtt
<< (TCP_RTTVAR_SHIFT
- 1);
1654 * the retransmit should happen at rtt + 4 * rttvar.
1655 * Because of the way we do the smoothing, srtt and rttvar
1656 * will each average +1/2 tick of bias. When we compute
1657 * the retransmit timer, we want 1/2 tick of rounding and
1658 * 1 extra tick because of +-1/2 tick uncertainty in the
1659 * firing of the timer. The bias will give us exactly the
1660 * 1.5 tick we need. But, because the bias is
1661 * statistical, we have to test that we don't drop below
1662 * the minimum feasible timer (which is 2 ticks).
1664 TCPT_RANGESET(tp
->t_rxtcur
, TCP_REXMTVAL(tp
),
1665 (short)tp
->t_rttmin
, TCPTV_REXMTMAX
); /* XXX */
1668 * We received an ack for a packet that wasn't retransmitted;
1669 * it is probably safe to discard any error indications we've
1670 * received recently. This isn't quite right, but close enough
1671 * for now (a route might have failed after we sent a segment,
1672 * and the return path might not be symmetrical).
1674 tp
->t_softerror
= 0;
1678 * Determine a reasonable value for maxseg size.
1679 * If the route is known, check route for mtu.
1680 * If none, use an mss that can be handled on the outgoing
1681 * interface without forcing IP to fragment; if bigger than
1682 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
1683 * to utilize large mbufs. If no route is found, route has no mtu,
1684 * or the destination isn't local, use a default, hopefully conservative
1685 * size (usually 512 or the default IP max size, but no more than the mtu
1686 * of the interface), as we can't discover anything about intervening
1687 * gateways or networks. We also initialize the congestion/slow start
1688 * window to be a single segment if the destination isn't local.
1689 * While looking at the routing entry, we also initialize other path-dependent
1690 * parameters from pre-set or cached values in the routing entry.
1695 register struct tcpcb
*tp
;
1698 struct socket
*so
= tp
->t_socket
;
1701 DEBUG_CALL("tcp_mss");
1702 DEBUG_ARG("tp = %lx", (long)tp
);
1703 DEBUG_ARG("offer = %d", offer
);
1705 mss
= min(IF_MTU
, IF_MRU
) - sizeof(struct tcpiphdr
);
1707 mss
= min(mss
, offer
);
1709 if (mss
< tp
->t_maxseg
|| offer
!= 0)
1714 sbreserve(&so
->so_snd
, TCP_SNDSPACE
+ ((TCP_SNDSPACE
% mss
) ?
1715 (mss
- (TCP_SNDSPACE
% mss
)) :
1717 sbreserve(&so
->so_rcv
, TCP_RCVSPACE
+ ((TCP_RCVSPACE
% mss
) ?
1718 (mss
- (TCP_RCVSPACE
% mss
)) :
1721 DEBUG_MISC((dfd
, " returning mss = %d\n", mss
));