tcp_subr.c revision 1.26 1 /* $NetBSD: tcp_subr.c,v 1.26 1997/06/24 02:26:06 thorpej Exp $ */
2
3 /*
4 * Copyright (c) 1982, 1986, 1988, 1990, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. All advertising materials mentioning features or use of this software
16 * must display the following acknowledgement:
17 * This product includes software developed by the University of
18 * California, Berkeley and its contributors.
19 * 4. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 *
35 * @(#)tcp_subr.c 8.1 (Berkeley) 6/10/93
36 */
37
38 #include <sys/param.h>
39 #include <sys/proc.h>
40 #include <sys/systm.h>
41 #include <sys/malloc.h>
42 #include <sys/mbuf.h>
43 #include <sys/socket.h>
44 #include <sys/socketvar.h>
45 #include <sys/protosw.h>
46 #include <sys/errno.h>
47
48 #include <net/route.h>
49 #include <net/if.h>
50
51 #include <netinet/in.h>
52 #include <netinet/in_systm.h>
53 #include <netinet/ip.h>
54 #include <netinet/in_pcb.h>
55 #include <netinet/ip_var.h>
56 #include <netinet/ip_icmp.h>
57 #include <netinet/tcp.h>
58 #include <netinet/tcp_fsm.h>
59 #include <netinet/tcp_seq.h>
60 #include <netinet/tcp_timer.h>
61 #include <netinet/tcp_var.h>
62 #include <netinet/tcpip.h>
63
64 /* patchable/settable parameters for tcp */
65 int tcp_mssdflt = TCP_MSS;
66 int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ;
67 int tcp_do_rfc1323 = 1;
68
69 #ifndef TCBHASHSIZE
70 #define TCBHASHSIZE 128
71 #endif
72 int tcbhashsize = TCBHASHSIZE;
73
74 /*
75 * Tcp initialization
76 */
77 void
78 tcp_init()
79 {
80
81 tcp_iss = 1; /* XXX wrong */
82 in_pcbinit(&tcbtable, tcbhashsize, tcbhashsize);
83 if (max_protohdr < sizeof(struct tcpiphdr))
84 max_protohdr = sizeof(struct tcpiphdr);
85 if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN)
86 panic("tcp_init");
87 }
88
89 /*
90 * Create template to be used to send tcp packets on a connection.
91 * Call after host entry created, allocates an mbuf and fills
92 * in a skeletal tcp/ip header, minimizing the amount of work
93 * necessary when the connection is used.
94 */
95 struct tcpiphdr *
96 tcp_template(tp)
97 struct tcpcb *tp;
98 {
99 register struct inpcb *inp = tp->t_inpcb;
100 register struct tcpiphdr *n;
101
102 if ((n = tp->t_template) == 0) {
103 MALLOC(n, struct tcpiphdr *, sizeof (struct tcpiphdr),
104 M_MBUF, M_NOWAIT);
105 if (n == NULL)
106 return (0);
107 }
108 bzero(n->ti_x1, sizeof n->ti_x1);
109 n->ti_pr = IPPROTO_TCP;
110 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip));
111 n->ti_src = inp->inp_laddr;
112 n->ti_dst = inp->inp_faddr;
113 n->ti_sport = inp->inp_lport;
114 n->ti_dport = inp->inp_fport;
115 n->ti_seq = 0;
116 n->ti_ack = 0;
117 n->ti_x2 = 0;
118 n->ti_off = 5;
119 n->ti_flags = 0;
120 n->ti_win = 0;
121 n->ti_sum = 0;
122 n->ti_urp = 0;
123 return (n);
124 }
125
126 /*
127 * Send a single message to the TCP at address specified by
128 * the given TCP/IP header. If m == 0, then we make a copy
129 * of the tcpiphdr at ti and send directly to the addressed host.
130 * This is used to force keep alive messages out using the TCP
131 * template for a connection tp->t_template. If flags are given
132 * then we send a message back to the TCP which originated the
133 * segment ti, and discard the mbuf containing it and any other
134 * attached mbufs.
135 *
136 * In any case the ack and sequence number of the transmitted
137 * segment are as specified by the parameters.
138 */
139 void
140 tcp_respond(tp, ti, m, ack, seq, flags)
141 struct tcpcb *tp;
142 register struct tcpiphdr *ti;
143 register struct mbuf *m;
144 tcp_seq ack, seq;
145 int flags;
146 {
147 register int tlen;
148 int win = 0;
149 struct route *ro = 0;
150
151 if (tp) {
152 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv);
153 ro = &tp->t_inpcb->inp_route;
154 }
155 if (m == 0) {
156 m = m_gethdr(M_DONTWAIT, MT_HEADER);
157 if (m == NULL)
158 return;
159 #ifdef TCP_COMPAT_42
160 tlen = 1;
161 #else
162 tlen = 0;
163 #endif
164 m->m_data += max_linkhdr;
165 *mtod(m, struct tcpiphdr *) = *ti;
166 ti = mtod(m, struct tcpiphdr *);
167 flags = TH_ACK;
168 } else {
169 m_freem(m->m_next);
170 m->m_next = 0;
171 m->m_data = (caddr_t)ti;
172 m->m_len = sizeof (struct tcpiphdr);
173 tlen = 0;
174 #define xchg(a,b,type) { type t; t=a; a=b; b=t; }
175 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_int32_t);
176 xchg(ti->ti_dport, ti->ti_sport, u_int16_t);
177 #undef xchg
178 }
179 ti->ti_len = htons((u_int16_t)(sizeof (struct tcphdr) + tlen));
180 tlen += sizeof (struct tcpiphdr);
181 m->m_len = tlen;
182 m->m_pkthdr.len = tlen;
183 m->m_pkthdr.rcvif = (struct ifnet *) 0;
184 bzero(ti->ti_x1, sizeof ti->ti_x1);
185 ti->ti_seq = htonl(seq);
186 ti->ti_ack = htonl(ack);
187 ti->ti_x2 = 0;
188 ti->ti_off = sizeof (struct tcphdr) >> 2;
189 ti->ti_flags = flags;
190 if (tp)
191 ti->ti_win = htons((u_int16_t) (win >> tp->rcv_scale));
192 else
193 ti->ti_win = htons((u_int16_t)win);
194 ti->ti_urp = 0;
195 ti->ti_sum = 0;
196 ti->ti_sum = in_cksum(m, tlen);
197 ((struct ip *)ti)->ip_len = tlen;
198 ((struct ip *)ti)->ip_ttl = ip_defttl;
199 (void) ip_output(m, NULL, ro, 0, NULL);
200 }
201
202 /*
203 * Create a new TCP control block, making an
204 * empty reassembly queue and hooking it to the argument
205 * protocol control block.
206 */
207 struct tcpcb *
208 tcp_newtcpcb(inp)
209 struct inpcb *inp;
210 {
211 register struct tcpcb *tp;
212
213 tp = malloc(sizeof(*tp), M_PCB, M_NOWAIT);
214 if (tp == NULL)
215 return ((struct tcpcb *)0);
216 bzero((caddr_t)tp, sizeof(struct tcpcb));
217 LIST_INIT(&tp->segq);
218 tp->t_maxseg = tcp_mssdflt;
219
220 tp->t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0;
221 tp->t_inpcb = inp;
222 /*
223 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
224 * rtt estimate. Set rttvar so that srtt + 2 * rttvar gives
225 * reasonable initial retransmit time.
226 */
227 tp->t_srtt = TCPTV_SRTTBASE;
228 tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << (TCP_RTTVAR_SHIFT + 2 - 1);
229 tp->t_rttmin = TCPTV_MIN;
230 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
231 TCPTV_MIN, TCPTV_REXMTMAX);
232 tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
233 tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
234 inp->inp_ip.ip_ttl = ip_defttl;
235 inp->inp_ppcb = (caddr_t)tp;
236 return (tp);
237 }
238
239 /*
240 * Drop a TCP connection, reporting
241 * the specified error. If connection is synchronized,
242 * then send a RST to peer.
243 */
244 struct tcpcb *
245 tcp_drop(tp, errno)
246 register struct tcpcb *tp;
247 int errno;
248 {
249 struct socket *so = tp->t_inpcb->inp_socket;
250
251 if (TCPS_HAVERCVDSYN(tp->t_state)) {
252 tp->t_state = TCPS_CLOSED;
253 (void) tcp_output(tp);
254 tcpstat.tcps_drops++;
255 } else
256 tcpstat.tcps_conndrops++;
257 if (errno == ETIMEDOUT && tp->t_softerror)
258 errno = tp->t_softerror;
259 so->so_error = errno;
260 return (tcp_close(tp));
261 }
262
263 /*
264 * Close a TCP control block:
265 * discard all space held by the tcp
266 * discard internet protocol block
267 * wake up any sleepers
268 */
269 struct tcpcb *
270 tcp_close(tp)
271 register struct tcpcb *tp;
272 {
273 register struct ipqent *qe;
274 struct inpcb *inp = tp->t_inpcb;
275 struct socket *so = inp->inp_socket;
276 #ifdef RTV_RTT
277 register struct rtentry *rt;
278
279 /*
280 * If we sent enough data to get some meaningful characteristics,
281 * save them in the routing entry. 'Enough' is arbitrarily
282 * defined as the sendpipesize (default 4K) * 16. This would
283 * give us 16 rtt samples assuming we only get one sample per
284 * window (the usual case on a long haul net). 16 samples is
285 * enough for the srtt filter to converge to within 5% of the correct
286 * value; fewer samples and we could save a very bogus rtt.
287 *
288 * Don't update the default route's characteristics and don't
289 * update anything that the user "locked".
290 */
291 if (SEQ_LT(tp->iss + so->so_snd.sb_hiwat * 16, tp->snd_max) &&
292 (rt = inp->inp_route.ro_rt) &&
293 !in_nullhost(satosin(rt_key(rt))->sin_addr)) {
294 register u_long i = 0;
295
296 if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) {
297 i = tp->t_srtt *
298 ((RTM_RTTUNIT / PR_SLOWHZ) >> (TCP_RTT_SHIFT + 2));
299 if (rt->rt_rmx.rmx_rtt && i)
300 /*
301 * filter this update to half the old & half
302 * the new values, converting scale.
303 * See route.h and tcp_var.h for a
304 * description of the scaling constants.
305 */
306 rt->rt_rmx.rmx_rtt =
307 (rt->rt_rmx.rmx_rtt + i) / 2;
308 else
309 rt->rt_rmx.rmx_rtt = i;
310 }
311 if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) {
312 i = tp->t_rttvar *
313 ((RTM_RTTUNIT / PR_SLOWHZ) >> (TCP_RTTVAR_SHIFT + 2));
314 if (rt->rt_rmx.rmx_rttvar && i)
315 rt->rt_rmx.rmx_rttvar =
316 (rt->rt_rmx.rmx_rttvar + i) / 2;
317 else
318 rt->rt_rmx.rmx_rttvar = i;
319 }
320 /*
321 * update the pipelimit (ssthresh) if it has been updated
322 * already or if a pipesize was specified & the threshhold
323 * got below half the pipesize. I.e., wait for bad news
324 * before we start updating, then update on both good
325 * and bad news.
326 */
327 if (((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 &&
328 (i = tp->snd_ssthresh) && rt->rt_rmx.rmx_ssthresh) ||
329 i < (rt->rt_rmx.rmx_sendpipe / 2)) {
330 /*
331 * convert the limit from user data bytes to
332 * packets then to packet data bytes.
333 */
334 i = (i + tp->t_maxseg / 2) / tp->t_maxseg;
335 if (i < 2)
336 i = 2;
337 i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr));
338 if (rt->rt_rmx.rmx_ssthresh)
339 rt->rt_rmx.rmx_ssthresh =
340 (rt->rt_rmx.rmx_ssthresh + i) / 2;
341 else
342 rt->rt_rmx.rmx_ssthresh = i;
343 }
344 }
345 #endif /* RTV_RTT */
346 /* free the reassembly queue, if any */
347 while ((qe = tp->segq.lh_first) != NULL) {
348 LIST_REMOVE(qe, ipqe_q);
349 m_freem(qe->ipqe_m);
350 FREE(qe, M_IPQ);
351 }
352 if (tp->t_template)
353 FREE(tp->t_template, M_MBUF);
354 free(tp, M_PCB);
355 inp->inp_ppcb = 0;
356 soisdisconnected(so);
357 in_pcbdetach(inp);
358 tcpstat.tcps_closed++;
359 return ((struct tcpcb *)0);
360 }
361
362 void
363 tcp_drain()
364 {
365
366 }
367
368 /*
369 * Notify a tcp user of an asynchronous error;
370 * store error as soft error, but wake up user
371 * (for now, won't do anything until can select for soft error).
372 */
373 void
374 tcp_notify(inp, error)
375 struct inpcb *inp;
376 int error;
377 {
378 register struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb;
379 register struct socket *so = inp->inp_socket;
380
381 /*
382 * Ignore some errors if we are hooked up.
383 * If connection hasn't completed, has retransmitted several times,
384 * and receives a second error, give up now. This is better
385 * than waiting a long time to establish a connection that
386 * can never complete.
387 */
388 if (tp->t_state == TCPS_ESTABLISHED &&
389 (error == EHOSTUNREACH || error == ENETUNREACH ||
390 error == EHOSTDOWN)) {
391 return;
392 } else if (TCPS_HAVEESTABLISHED(tp->t_state) == 0 &&
393 tp->t_rxtshift > 3 && tp->t_softerror)
394 so->so_error = error;
395 else
396 tp->t_softerror = error;
397 wakeup((caddr_t) &so->so_timeo);
398 sorwakeup(so);
399 sowwakeup(so);
400 }
401
402 void *
403 tcp_ctlinput(cmd, sa, v)
404 int cmd;
405 struct sockaddr *sa;
406 register void *v;
407 {
408 register struct ip *ip = v;
409 register struct tcphdr *th;
410 extern int inetctlerrmap[];
411 void (*notify) __P((struct inpcb *, int)) = tcp_notify;
412 int errno;
413
414 if ((unsigned)cmd >= PRC_NCMDS)
415 return NULL;
416 errno = inetctlerrmap[cmd];
417 if (cmd == PRC_QUENCH)
418 notify = tcp_quench;
419 else if (PRC_IS_REDIRECT(cmd))
420 notify = in_rtchange, ip = 0;
421 else if (cmd == PRC_HOSTDEAD)
422 ip = 0;
423 else if (errno == 0)
424 return NULL;
425 if (ip) {
426 th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2));
427 in_pcbnotify(&tcbtable, satosin(sa)->sin_addr, th->th_dport,
428 ip->ip_src, th->th_sport, errno, notify);
429 } else
430 in_pcbnotifyall(&tcbtable, satosin(sa)->sin_addr, errno,
431 notify);
432 return NULL;
433 }
434
435 /*
436 * When a source quench is received, close congestion window
437 * to one segment. We will gradually open it again as we proceed.
438 */
439 void
440 tcp_quench(inp, errno)
441 struct inpcb *inp;
442 int errno;
443 {
444 struct tcpcb *tp = intotcpcb(inp);
445
446 if (tp)
447 tp->snd_cwnd = tp->t_maxseg;
448 }
449