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_maxseg(SYSCTL_HANDLER_ARGS);
78 static int tcp_reass_sysctl_qsize(SYSCTL_HANDLER_ARGS);
79
80 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
81 "TCP Segment Reassembly Queue");
82
83 static int tcp_reass_maxseg = 0;
84 SYSCTL_VNET_PROC(_net_inet_tcp_reass, OID_AUTO, maxsegments,
85 CTLTYPE_INT | CTLFLAG_RDTUN,
86 &tcp_reass_maxseg, 0, &tcp_reass_sysctl_maxseg, "I",
87 "Global maximum number of TCP Segments in Reassembly Queue");
88
89 static int tcp_reass_qsize = 0;
90 SYSCTL_PROC(_net_inet_tcp_reass, OID_AUTO, cursegments,
91 CTLTYPE_INT | CTLFLAG_RD,
92 &tcp_reass_qsize, 0, &tcp_reass_sysctl_qsize, "I",
93 "Global number of TCP Segments currently in Reassembly Queue");
94
95 static int tcp_reass_overflows = 0;
96 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows,
97 CTLTYPE_INT | CTLFLAG_RD,
98 &tcp_reass_overflows, 0,
99 "Global number of TCP Segment Reassembly Queue Overflows");
100
101 static uma_zone_t tcp_reass_zone;
102
103 /* Initialize TCP reassembly queue */
104 static void
105 tcp_reass_zone_change(void *tag)
106 {
107
108 tcp_reass_maxseg = nmbclusters / 16;
109 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg);
110 }
111
112 void
113 tcp_reass_global_init(void)
114 {
115
116 tcp_reass_maxseg = nmbclusters / 16;
117 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
118 &tcp_reass_maxseg);
119 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
120 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
121 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg);
122 EVENTHANDLER_REGISTER(nmbclusters_change,
123 tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
124 }
125
126 void
127 tcp_reass_flush(struct tcpcb *tp)
128 {
129 struct tseg_qent *qe;
130
131 INP_WLOCK_ASSERT(tp->t_inpcb);
132
133 while ((qe = LIST_FIRST(&tp->t_segq)) != NULL) {
134 LIST_REMOVE(qe, tqe_q);
135 m_freem(qe->tqe_m);
136 uma_zfree(tcp_reass_zone, qe);
137 tp->t_segqlen--;
138 }
139
140 KASSERT((tp->t_segqlen == 0),
141 ("TCP reass queue %p segment count is %d instead of 0 after flush.",
142 tp, tp->t_segqlen));
143 }
144
145 static int
146 tcp_reass_sysctl_maxseg(SYSCTL_HANDLER_ARGS)
147 {
148 tcp_reass_maxseg = uma_zone_get_max(tcp_reass_zone);
149 return (sysctl_handle_int(oidp, arg1, arg2, req));
150 }
151
152 static int
153 tcp_reass_sysctl_qsize(SYSCTL_HANDLER_ARGS)
154 {
155 tcp_reass_qsize = uma_zone_get_cur(tcp_reass_zone);
156 return (sysctl_handle_int(oidp, arg1, arg2, req));
157 }
158
159 int
160 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
161 {
162 struct tseg_qent *q;
163 struct tseg_qent *p = NULL;
164 struct tseg_qent *nq;
165 struct tseg_qent *te = NULL;
166 struct socket *so = tp->t_inpcb->inp_socket;
167 char *s = NULL;
168 int flags;
169 struct tseg_qent tqs;
170
171 INP_WLOCK_ASSERT(tp->t_inpcb);
172
173 /*
174 * XXX: tcp_reass() is rather inefficient with its data structures
175 * and should be rewritten (see NetBSD for optimizations).
176 */
177
178 /*
179 * Call with th==NULL after become established to
180 * force pre-ESTABLISHED data up to user socket.
181 */
182 if (th == NULL)
183 goto present;
184
185 /*
186 * Limit the number of segments that can be queued to reduce the
187 * potential for mbuf exhaustion. For best performance, we want to be
188 * able to queue a full window's worth of segments. The size of the
189 * socket receive buffer determines our advertised window and grows
190 * automatically when socket buffer autotuning is enabled. Use it as the
191 * basis for our queue limit.
192 * Always let the missing segment through which caused this queue.
193 * NB: Access to the socket buffer is left intentionally unlocked as we
194 * can tolerate stale information here.
195 *
196 * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
197 * should work but causes packets to be dropped when they shouldn't.
198 * Investigate why and re-evaluate the below limit after the behaviour
199 * is understood.
200 */
201 if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
202 tp->t_segqlen >= (so->so_rcv.sb_hiwat / tp->t_maxseg) + 1) {
203 tcp_reass_overflows++;
204 TCPSTAT_INC(tcps_rcvmemdrop);
205 m_freem(m);
206 *tlenp = 0;
207 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
208 log(LOG_DEBUG, "%s; %s: queue limit reached, "
209 "segment dropped\n", s, __func__);
210 free(s, M_TCPLOG);
211 }
212 return (0);
213 }
214
215 /*
216 * Allocate a new queue entry. If we can't, or hit the zone limit
217 * just drop the pkt.
218 *
219 * Use a temporary structure on the stack for the missing segment
220 * when the zone is exhausted. Otherwise we may get stuck.
221 */
222 te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
223 if (te == NULL) {
224 if (th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) {
225 TCPSTAT_INC(tcps_rcvmemdrop);
226 m_freem(m);
227 *tlenp = 0;
228 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
229 NULL))) {
230 log(LOG_DEBUG, "%s; %s: global zone limit "
231 "reached, segment dropped\n", s, __func__);
232 free(s, M_TCPLOG);
233 }
234 return (0);
235 } else {
236 bzero(&tqs, sizeof(struct tseg_qent));
237 te = &tqs;
238 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
239 NULL))) {
240 log(LOG_DEBUG,
241 "%s; %s: global zone limit reached, using "
242 "stack for missing segment\n", s, __func__);
243 free(s, M_TCPLOG);
244 }
245 }
246 }
247 tp->t_segqlen++;
248
249 /*
250 * Find a segment which begins after this one does.
251 */
252 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
253 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
254 break;
255 p = q;
256 }
257
258 /*
259 * If there is a preceding segment, it may provide some of
260 * our data already. If so, drop the data from the incoming
261 * segment. If it provides all of our data, drop us.
262 */
263 if (p != NULL) {
264 int i;
265 /* conversion to int (in i) handles seq wraparound */
266 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
267 if (i > 0) {
268 if (i >= *tlenp) {
269 TCPSTAT_INC(tcps_rcvduppack);
270 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
271 m_freem(m);
272 if (te != &tqs)
273 uma_zfree(tcp_reass_zone, te);
274 tp->t_segqlen--;
275 /*
276 * Try to present any queued data
277 * at the left window edge to the user.
278 * This is needed after the 3-WHS
279 * completes.
280 */
281 goto present; /* ??? */
282 }
283 m_adj(m, i);
284 *tlenp -= i;
285 th->th_seq += i;
286 }
287 }
288 tp->t_rcvoopack++;
289 TCPSTAT_INC(tcps_rcvoopack);
290 TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
291
292 /*
293 * While we overlap succeeding segments trim them or,
294 * if they are completely covered, dequeue them.
295 */
296 while (q) {
297 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
298 if (i <= 0)
299 break;
300 if (i < q->tqe_len) {
301 q->tqe_th->th_seq += i;
302 q->tqe_len -= i;
303 m_adj(q->tqe_m, i);
304 break;
305 }
306
307 nq = LIST_NEXT(q, tqe_q);
308 LIST_REMOVE(q, tqe_q);
309 m_freem(q->tqe_m);
310 uma_zfree(tcp_reass_zone, q);
311 tp->t_segqlen--;
312 q = nq;
313 }
314
315 /* Insert the new segment queue entry into place. */
316 te->tqe_m = m;
317 te->tqe_th = th;
318 te->tqe_len = *tlenp;
319
320 if (p == NULL) {
321 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
322 } else {
323 KASSERT(te != &tqs, ("%s: temporary stack based entry not "
324 "first element in queue", __func__));
325 LIST_INSERT_AFTER(p, te, tqe_q);
326 }
327
328 present:
329 /*
330 * Present data to user, advancing rcv_nxt through
331 * completed sequence space.
332 */
333 if (!TCPS_HAVEESTABLISHED(tp->t_state))
334 return (0);
335 q = LIST_FIRST(&tp->t_segq);
336 if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
337 return (0);
338 SOCKBUF_LOCK(&so->so_rcv);
339 do {
340 tp->rcv_nxt += q->tqe_len;
341 flags = q->tqe_th->th_flags & TH_FIN;
342 nq = LIST_NEXT(q, tqe_q);
343 LIST_REMOVE(q, tqe_q);
344 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
345 m_freem(q->tqe_m);
346 else
347 sbappendstream_locked(&so->so_rcv, q->tqe_m);
348 if (q != &tqs)
349 uma_zfree(tcp_reass_zone, q);
350 tp->t_segqlen--;
351 q = nq;
352 } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
353 ND6_HINT(tp);
354 sorwakeup_locked(so);
355 return (flags);
356 }
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