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: releng/10.2/sys/netinet/tcp_reass.c 285978 2015-07-28 19:59:04Z delphij $");
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 int tcp_reass_maxseg = 0;
83 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
84 &tcp_reass_maxseg, 0,
85 "Global maximum number of TCP Segments in Reassembly Queue");
86
87 SYSCTL_PROC(_net_inet_tcp_reass, OID_AUTO, cursegments,
88 (CTLTYPE_INT | CTLFLAG_RD), NULL, 0, &tcp_reass_sysctl_qsize, "I",
89 "Global number of TCP Segments currently in Reassembly Queue");
90
91 static int tcp_reass_overflows = 0;
92 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows,
93 CTLFLAG_RD,
94 &tcp_reass_overflows, 0,
95 "Global number of TCP Segment Reassembly Queue Overflows");
96
97 static uma_zone_t tcp_reass_zone;
98
99 /* Initialize TCP reassembly queue */
100 static void
101 tcp_reass_zone_change(void *tag)
102 {
103
104 /* Set the zone limit and read back the effective value. */
105 tcp_reass_maxseg = nmbclusters / 16;
106 tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
107 tcp_reass_maxseg);
108 }
109
110 void
111 tcp_reass_global_init(void)
112 {
113
114 tcp_reass_maxseg = nmbclusters / 16;
115 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
116 &tcp_reass_maxseg);
117 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
118 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
119 /* Set the zone limit and read back the effective value. */
120 tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
121 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_qsize(SYSCTL_HANDLER_ARGS)
147 {
148 int qsize;
149
150 qsize = uma_zone_get_cur(tcp_reass_zone);
151 return (sysctl_handle_int(oidp, &qsize, 0, req));
152 }
153
154 int
155 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
156 {
157 struct tseg_qent *q;
158 struct tseg_qent *p = NULL;
159 struct tseg_qent *nq;
160 struct tseg_qent *te = NULL;
161 struct socket *so = tp->t_inpcb->inp_socket;
162 char *s = NULL;
163 int flags;
164 struct tseg_qent tqs;
165
166 INP_WLOCK_ASSERT(tp->t_inpcb);
167
168 /*
169 * XXX: tcp_reass() is rather inefficient with its data structures
170 * and should be rewritten (see NetBSD for optimizations).
171 */
172
173 /*
174 * Call with th==NULL after become established to
175 * force pre-ESTABLISHED data up to user socket.
176 */
177 if (th == NULL)
178 goto present;
179
180 /*
181 * Limit the number of segments that can be queued to reduce the
182 * potential for mbuf exhaustion. For best performance, we want to be
183 * able to queue a full window's worth of segments. The size of the
184 * socket receive buffer determines our advertised window and grows
185 * automatically when socket buffer autotuning is enabled. Use it as the
186 * basis for our queue limit.
187 * Always let the missing segment through which caused this queue.
188 * NB: Access to the socket buffer is left intentionally unlocked as we
189 * can tolerate stale information here.
190 *
191 * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
192 * should work but causes packets to be dropped when they shouldn't.
193 * Investigate why and re-evaluate the below limit after the behaviour
194 * is understood.
195 */
196 if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
197 tp->t_segqlen >= (so->so_rcv.sb_hiwat / tp->t_maxseg) + 1) {
198 tcp_reass_overflows++;
199 TCPSTAT_INC(tcps_rcvmemdrop);
200 m_freem(m);
201 *tlenp = 0;
202 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
203 log(LOG_DEBUG, "%s; %s: queue limit reached, "
204 "segment dropped\n", s, __func__);
205 free(s, M_TCPLOG);
206 }
207 return (0);
208 }
209
210 /*
211 * Allocate a new queue entry. If we can't, or hit the zone limit
212 * just drop the pkt.
213 *
214 * Use a temporary structure on the stack for the missing segment
215 * when the zone is exhausted. Otherwise we may get stuck.
216 */
217 te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
218 if (te == NULL) {
219 if (th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) {
220 TCPSTAT_INC(tcps_rcvmemdrop);
221 m_freem(m);
222 *tlenp = 0;
223 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
224 NULL))) {
225 log(LOG_DEBUG, "%s; %s: global zone limit "
226 "reached, segment dropped\n", s, __func__);
227 free(s, M_TCPLOG);
228 }
229 return (0);
230 } else {
231 bzero(&tqs, sizeof(struct tseg_qent));
232 te = &tqs;
233 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
234 NULL))) {
235 log(LOG_DEBUG,
236 "%s; %s: global zone limit reached, using "
237 "stack for missing segment\n", s, __func__);
238 free(s, M_TCPLOG);
239 }
240 }
241 }
242 tp->t_segqlen++;
243
244 /*
245 * Find a segment which begins after this one does.
246 */
247 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
248 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
249 break;
250 p = q;
251 }
252
253 /*
254 * If there is a preceding segment, it may provide some of
255 * our data already. If so, drop the data from the incoming
256 * segment. If it provides all of our data, drop us.
257 */
258 if (p != NULL) {
259 int i;
260 /* conversion to int (in i) handles seq wraparound */
261 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
262 if (i > 0) {
263 if (i >= *tlenp) {
264 TCPSTAT_INC(tcps_rcvduppack);
265 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
266 m_freem(m);
267 if (te != &tqs)
268 uma_zfree(tcp_reass_zone, te);
269 tp->t_segqlen--;
270 /*
271 * Try to present any queued data
272 * at the left window edge to the user.
273 * This is needed after the 3-WHS
274 * completes.
275 */
276 goto present; /* ??? */
277 }
278 m_adj(m, i);
279 *tlenp -= i;
280 th->th_seq += i;
281 }
282 }
283 tp->t_rcvoopack++;
284 TCPSTAT_INC(tcps_rcvoopack);
285 TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
286
287 /*
288 * While we overlap succeeding segments trim them or,
289 * if they are completely covered, dequeue them.
290 */
291 while (q) {
292 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
293 if (i <= 0)
294 break;
295 if (i < q->tqe_len) {
296 q->tqe_th->th_seq += i;
297 q->tqe_len -= i;
298 m_adj(q->tqe_m, i);
299 break;
300 }
301
302 nq = LIST_NEXT(q, tqe_q);
303 LIST_REMOVE(q, tqe_q);
304 m_freem(q->tqe_m);
305 uma_zfree(tcp_reass_zone, q);
306 tp->t_segqlen--;
307 q = nq;
308 }
309
310 /* Insert the new segment queue entry into place. */
311 te->tqe_m = m;
312 te->tqe_th = th;
313 te->tqe_len = *tlenp;
314
315 if (p == NULL) {
316 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
317 } else {
318 KASSERT(te != &tqs, ("%s: temporary stack based entry not "
319 "first element in queue", __func__));
320 LIST_INSERT_AFTER(p, te, tqe_q);
321 }
322
323 present:
324 /*
325 * Present data to user, advancing rcv_nxt through
326 * completed sequence space.
327 */
328 if (!TCPS_HAVEESTABLISHED(tp->t_state))
329 return (0);
330 q = LIST_FIRST(&tp->t_segq);
331 if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
332 return (0);
333 SOCKBUF_LOCK(&so->so_rcv);
334 do {
335 tp->rcv_nxt += q->tqe_len;
336 flags = q->tqe_th->th_flags & TH_FIN;
337 nq = LIST_NEXT(q, tqe_q);
338 LIST_REMOVE(q, tqe_q);
339 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
340 m_freem(q->tqe_m);
341 else
342 sbappendstream_locked(&so->so_rcv, q->tqe_m);
343 if (q != &tqs)
344 uma_zfree(tcp_reass_zone, q);
345 tp->t_segqlen--;
346 q = nq;
347 } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
348 ND6_HINT(tp);
349 sorwakeup_locked(so);
350 return (flags);
351 }
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