1 /*-
2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
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 * 4. 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 8.12 (Berkeley) 5/24/95
30 */
31
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
34
35 #include "opt_inet.h"
36 #include "opt_inet6.h"
37 #include "opt_tcpdebug.h"
38
39 #include <sys/param.h>
40 #include <sys/kernel.h>
41 #include <sys/malloc.h>
42 #include <sys/mbuf.h>
43 #include <sys/socket.h>
44 #include <sys/socketvar.h>
45 #include <sys/sysctl.h>
46 #include <sys/syslog.h>
47 #include <sys/systm.h>
48
49 #include <vm/uma.h>
50
51 #include <net/if.h>
52 #include <net/route.h>
53 #include <net/vnet.h>
54
55 #include <netinet/in.h>
56 #include <netinet/in_pcb.h>
57 #include <netinet/in_systm.h>
58 #include <netinet/in_var.h>
59 #include <netinet/ip.h>
60 #include <netinet/ip_var.h>
61 #include <netinet/ip_options.h>
62 #include <netinet/ip6.h>
63 #include <netinet6/in6_pcb.h>
64 #include <netinet6/ip6_var.h>
65 #include <netinet6/nd6.h>
66 #include <netinet/tcp.h>
67 #include <netinet/tcp_fsm.h>
68 #include <netinet/tcp_seq.h>
69 #include <netinet/tcp_timer.h>
70 #include <netinet/tcp_var.h>
71 #include <netinet6/tcp6_var.h>
72 #include <netinet/tcpip.h>
73 #ifdef TCPDEBUG
74 #include <netinet/tcp_debug.h>
75 #endif /* TCPDEBUG */
76
77 static int tcp_reass_sysctl_qsize(SYSCTL_HANDLER_ARGS);
78
79 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
80 "TCP Segment Reassembly Queue");
81
82 static VNET_DEFINE(int, tcp_reass_maxseg) = 0;
83 #define V_tcp_reass_maxseg VNET(tcp_reass_maxseg)
84 SYSCTL_VNET_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
85 &VNET_NAME(tcp_reass_maxseg), 0,
86 "Global maximum number of TCP Segments in Reassembly Queue");
87
88 SYSCTL_VNET_PROC(_net_inet_tcp_reass, OID_AUTO, cursegments,
89 (CTLTYPE_INT | CTLFLAG_RD), NULL, 0, &tcp_reass_sysctl_qsize, "I",
90 "Global number of TCP Segments currently in Reassembly Queue");
91
92 static VNET_DEFINE(int, tcp_reass_overflows) = 0;
93 #define V_tcp_reass_overflows VNET(tcp_reass_overflows)
94 SYSCTL_VNET_INT(_net_inet_tcp_reass, OID_AUTO, overflows,
95 CTLFLAG_RD,
96 &VNET_NAME(tcp_reass_overflows), 0,
97 "Global number of TCP Segment Reassembly Queue Overflows");
98
99 static VNET_DEFINE(uma_zone_t, tcp_reass_zone);
100 #define V_tcp_reass_zone VNET(tcp_reass_zone)
101
102 /* Initialize TCP reassembly queue */
103 static void
tcp_reass_zone_change(void * tag)104 tcp_reass_zone_change(void *tag)
105 {
106
107 /* Set the zone limit and read back the effective value. */
108 V_tcp_reass_maxseg = nmbclusters / 16;
109 V_tcp_reass_maxseg = uma_zone_set_max(V_tcp_reass_zone,
110 V_tcp_reass_maxseg);
111 }
112
113 void
tcp_reass_init(void)114 tcp_reass_init(void)
115 {
116
117 V_tcp_reass_maxseg = nmbclusters / 16;
118 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
119 &V_tcp_reass_maxseg);
120 V_tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
121 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
122 /* Set the zone limit and read back the effective value. */
123 V_tcp_reass_maxseg = uma_zone_set_max(V_tcp_reass_zone,
124 V_tcp_reass_maxseg);
125 EVENTHANDLER_REGISTER(nmbclusters_change,
126 tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
127 }
128
129 #ifdef VIMAGE
130 void
tcp_reass_destroy(void)131 tcp_reass_destroy(void)
132 {
133
134 uma_zdestroy(V_tcp_reass_zone);
135 }
136 #endif
137
138 void
tcp_reass_flush(struct tcpcb * tp)139 tcp_reass_flush(struct tcpcb *tp)
140 {
141 struct tseg_qent *qe;
142
143 INP_WLOCK_ASSERT(tp->t_inpcb);
144
145 while ((qe = LIST_FIRST(&tp->t_segq)) != NULL) {
146 LIST_REMOVE(qe, tqe_q);
147 m_freem(qe->tqe_m);
148 uma_zfree(V_tcp_reass_zone, qe);
149 tp->t_segqlen--;
150 }
151
152 KASSERT((tp->t_segqlen == 0),
153 ("TCP reass queue %p segment count is %d instead of 0 after flush.",
154 tp, tp->t_segqlen));
155 }
156
157 static int
tcp_reass_sysctl_qsize(SYSCTL_HANDLER_ARGS)158 tcp_reass_sysctl_qsize(SYSCTL_HANDLER_ARGS)
159 {
160 int qsize;
161
162 qsize = uma_zone_get_cur(V_tcp_reass_zone);
163 return (sysctl_handle_int(oidp, &qsize, 0, req));
164 }
165
166 int
tcp_reass(struct tcpcb * tp,struct tcphdr * th,int * tlenp,struct mbuf * m)167 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
168 {
169 struct tseg_qent *q;
170 struct tseg_qent *p = NULL;
171 struct tseg_qent *nq;
172 struct tseg_qent *te = NULL;
173 struct socket *so = tp->t_inpcb->inp_socket;
174 char *s = NULL;
175 int flags;
176 struct tseg_qent tqs;
177
178 INP_WLOCK_ASSERT(tp->t_inpcb);
179
180 /*
181 * XXX: tcp_reass() is rather inefficient with its data structures
182 * and should be rewritten (see NetBSD for optimizations).
183 */
184
185 /*
186 * Call with th==NULL after become established to
187 * force pre-ESTABLISHED data up to user socket.
188 */
189 if (th == NULL)
190 goto present;
191
192 /*
193 * Limit the number of segments that can be queued to reduce the
194 * potential for mbuf exhaustion. For best performance, we want to be
195 * able to queue a full window's worth of segments. The size of the
196 * socket receive buffer determines our advertised window and grows
197 * automatically when socket buffer autotuning is enabled. Use it as the
198 * basis for our queue limit.
199 * Always let the missing segment through which caused this queue.
200 * NB: Access to the socket buffer is left intentionally unlocked as we
201 * can tolerate stale information here.
202 *
203 * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
204 * should work but causes packets to be dropped when they shouldn't.
205 * Investigate why and re-evaluate the below limit after the behaviour
206 * is understood.
207 */
208 if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
209 tp->t_segqlen >= (so->so_rcv.sb_hiwat / tp->t_maxseg) + 1) {
210 V_tcp_reass_overflows++;
211 TCPSTAT_INC(tcps_rcvmemdrop);
212 m_freem(m);
213 *tlenp = 0;
214 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
215 log(LOG_DEBUG, "%s; %s: queue limit reached, "
216 "segment dropped\n", s, __func__);
217 free(s, M_TCPLOG);
218 }
219 return (0);
220 }
221
222 /*
223 * Allocate a new queue entry. If we can't, or hit the zone limit
224 * just drop the pkt.
225 *
226 * Use a temporary structure on the stack for the missing segment
227 * when the zone is exhausted. Otherwise we may get stuck.
228 */
229 te = uma_zalloc(V_tcp_reass_zone, M_NOWAIT);
230 if (te == NULL) {
231 if (th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) {
232 TCPSTAT_INC(tcps_rcvmemdrop);
233 m_freem(m);
234 *tlenp = 0;
235 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
236 NULL))) {
237 log(LOG_DEBUG, "%s; %s: global zone limit "
238 "reached, segment dropped\n", s, __func__);
239 free(s, M_TCPLOG);
240 }
241 return (0);
242 } else {
243 bzero(&tqs, sizeof(struct tseg_qent));
244 te = &tqs;
245 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
246 NULL))) {
247 log(LOG_DEBUG,
248 "%s; %s: global zone limit reached, using "
249 "stack for missing segment\n", s, __func__);
250 free(s, M_TCPLOG);
251 }
252 }
253 }
254 tp->t_segqlen++;
255
256 /*
257 * Find a segment which begins after this one does.
258 */
259 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
260 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
261 break;
262 p = q;
263 }
264
265 /*
266 * If there is a preceding segment, it may provide some of
267 * our data already. If so, drop the data from the incoming
268 * segment. If it provides all of our data, drop us.
269 */
270 if (p != NULL) {
271 int i;
272 /* conversion to int (in i) handles seq wraparound */
273 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
274 if (i > 0) {
275 if (i >= *tlenp) {
276 TCPSTAT_INC(tcps_rcvduppack);
277 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
278 m_freem(m);
279 if (te != &tqs)
280 uma_zfree(V_tcp_reass_zone, te);
281 tp->t_segqlen--;
282 /*
283 * Try to present any queued data
284 * at the left window edge to the user.
285 * This is needed after the 3-WHS
286 * completes.
287 */
288 goto present; /* ??? */
289 }
290 m_adj(m, i);
291 *tlenp -= i;
292 th->th_seq += i;
293 }
294 }
295 tp->t_rcvoopack++;
296 TCPSTAT_INC(tcps_rcvoopack);
297 TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
298
299 /*
300 * While we overlap succeeding segments trim them or,
301 * if they are completely covered, dequeue them.
302 */
303 while (q) {
304 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
305 if (i <= 0)
306 break;
307 if (i < q->tqe_len) {
308 q->tqe_th->th_seq += i;
309 q->tqe_len -= i;
310 m_adj(q->tqe_m, i);
311 break;
312 }
313
314 nq = LIST_NEXT(q, tqe_q);
315 LIST_REMOVE(q, tqe_q);
316 m_freem(q->tqe_m);
317 uma_zfree(V_tcp_reass_zone, q);
318 tp->t_segqlen--;
319 q = nq;
320 }
321
322 /* Insert the new segment queue entry into place. */
323 te->tqe_m = m;
324 te->tqe_th = th;
325 te->tqe_len = *tlenp;
326
327 if (p == NULL) {
328 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
329 } else {
330 KASSERT(te != &tqs, ("%s: temporary stack based entry not "
331 "first element in queue", __func__));
332 LIST_INSERT_AFTER(p, te, tqe_q);
333 }
334
335 present:
336 /*
337 * Present data to user, advancing rcv_nxt through
338 * completed sequence space.
339 */
340 if (!TCPS_HAVEESTABLISHED(tp->t_state))
341 return (0);
342 q = LIST_FIRST(&tp->t_segq);
343 if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
344 return (0);
345 SOCKBUF_LOCK(&so->so_rcv);
346 do {
347 tp->rcv_nxt += q->tqe_len;
348 flags = q->tqe_th->th_flags & TH_FIN;
349 nq = LIST_NEXT(q, tqe_q);
350 LIST_REMOVE(q, tqe_q);
351 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
352 m_freem(q->tqe_m);
353 else
354 sbappendstream_locked(&so->so_rcv, q->tqe_m);
355 if (q != &tqs)
356 uma_zfree(V_tcp_reass_zone, q);
357 tp->t_segqlen--;
358 q = nq;
359 } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
360 ND6_HINT(tp);
361 sorwakeup_locked(so);
362 return (flags);
363 }
364