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/10.4/sys/netinet/tcp_reass.c 337389 2018-08-06 17:50:40Z jtl $");
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 static u_int tcp_reass_maxqueuelen = 100;
100 SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, maxqueuelen, CTLFLAG_RWTUN,
101 &tcp_reass_maxqueuelen, 0,
102 "Maximum number of TCP Segments per Reassembly Queue");
103
104 /* Initialize TCP reassembly queue */
105 static void
106 tcp_reass_zone_change(void *tag)
107 {
108
109 /* Set the zone limit and read back the effective value. */
110 tcp_reass_maxseg = nmbclusters / 16;
111 tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
112 tcp_reass_maxseg);
113 }
114
115 void
116 tcp_reass_global_init(void)
117 {
118
119 tcp_reass_maxseg = nmbclusters / 16;
120 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
121 &tcp_reass_maxseg);
122 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
123 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
124 /* Set the zone limit and read back the effective value. */
125 tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
126 tcp_reass_maxseg);
127 EVENTHANDLER_REGISTER(nmbclusters_change,
128 tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
129 }
130
131 void
132 tcp_reass_flush(struct tcpcb *tp)
133 {
134 struct tseg_qent *qe;
135
136 INP_WLOCK_ASSERT(tp->t_inpcb);
137
138 while ((qe = LIST_FIRST(&tp->t_segq)) != NULL) {
139 LIST_REMOVE(qe, tqe_q);
140 m_freem(qe->tqe_m);
141 uma_zfree(tcp_reass_zone, qe);
142 tp->t_segqlen--;
143 }
144
145 KASSERT((tp->t_segqlen == 0),
146 ("TCP reass queue %p segment count is %d instead of 0 after flush.",
147 tp, tp->t_segqlen));
148 }
149
150 static int
151 tcp_reass_sysctl_qsize(SYSCTL_HANDLER_ARGS)
152 {
153 int qsize;
154
155 qsize = uma_zone_get_cur(tcp_reass_zone);
156 return (sysctl_handle_int(oidp, &qsize, 0, 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 *
193 * However, allow the user to specify a ceiling for the number of
194 * segments in each queue.
195 *
196 * Always let the missing segment through which caused this queue.
197 * NB: Access to the socket buffer is left intentionally unlocked as we
198 * can tolerate stale information here.
199 *
200 * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
201 * should work but causes packets to be dropped when they shouldn't.
202 * Investigate why and re-evaluate the below limit after the behaviour
203 * is understood.
204 */
205 if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
206 tp->t_segqlen >= min((so->so_rcv.sb_hiwat / tp->t_maxseg) + 1,
207 tcp_reass_maxqueuelen)) {
208 tcp_reass_overflows++;
209 TCPSTAT_INC(tcps_rcvmemdrop);
210 m_freem(m);
211 *tlenp = 0;
212 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
213 log(LOG_DEBUG, "%s; %s: queue limit reached, "
214 "segment dropped\n", s, __func__);
215 free(s, M_TCPLOG);
216 }
217 return (0);
218 }
219
220 /*
221 * Allocate a new queue entry. If we can't, or hit the zone limit
222 * just drop the pkt.
223 *
224 * Use a temporary structure on the stack for the missing segment
225 * when the zone is exhausted. Otherwise we may get stuck.
226 */
227 te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
228 if (te == NULL) {
229 if (th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) {
230 TCPSTAT_INC(tcps_rcvmemdrop);
231 m_freem(m);
232 *tlenp = 0;
233 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
234 NULL))) {
235 log(LOG_DEBUG, "%s; %s: global zone limit "
236 "reached, segment dropped\n", s, __func__);
237 free(s, M_TCPLOG);
238 }
239 return (0);
240 } else {
241 bzero(&tqs, sizeof(struct tseg_qent));
242 te = &tqs;
243 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
244 NULL))) {
245 log(LOG_DEBUG,
246 "%s; %s: global zone limit reached, using "
247 "stack for missing segment\n", s, __func__);
248 free(s, M_TCPLOG);
249 }
250 }
251 }
252 tp->t_segqlen++;
253
254 /*
255 * Find a segment which begins after this one does.
256 */
257 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
258 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
259 break;
260 p = q;
261 }
262
263 /*
264 * If there is a preceding segment, it may provide some of
265 * our data already. If so, drop the data from the incoming
266 * segment. If it provides all of our data, drop us.
267 */
268 if (p != NULL) {
269 int i;
270 /* conversion to int (in i) handles seq wraparound */
271 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
272 if (i > 0) {
273 if (i >= *tlenp) {
274 TCPSTAT_INC(tcps_rcvduppack);
275 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
276 m_freem(m);
277 if (te != &tqs)
278 uma_zfree(tcp_reass_zone, te);
279 tp->t_segqlen--;
280 /*
281 * Try to present any queued data
282 * at the left window edge to the user.
283 * This is needed after the 3-WHS
284 * completes.
285 */
286 goto present; /* ??? */
287 }
288 m_adj(m, i);
289 *tlenp -= i;
290 th->th_seq += i;
291 }
292 }
293 tp->t_rcvoopack++;
294 TCPSTAT_INC(tcps_rcvoopack);
295 TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
296
297 /*
298 * While we overlap succeeding segments trim them or,
299 * if they are completely covered, dequeue them.
300 */
301 while (q) {
302 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
303 if (i <= 0)
304 break;
305 if (i < q->tqe_len) {
306 q->tqe_th->th_seq += i;
307 q->tqe_len -= i;
308 m_adj(q->tqe_m, i);
309 break;
310 }
311
312 nq = LIST_NEXT(q, tqe_q);
313 LIST_REMOVE(q, tqe_q);
314 m_freem(q->tqe_m);
315 uma_zfree(tcp_reass_zone, q);
316 tp->t_segqlen--;
317 q = nq;
318 }
319
320 /* Insert the new segment queue entry into place. */
321 te->tqe_m = m;
322 te->tqe_th = th;
323 te->tqe_len = *tlenp;
324
325 if (p == NULL) {
326 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
327 } else {
328 KASSERT(te != &tqs, ("%s: temporary stack based entry not "
329 "first element in queue", __func__));
330 LIST_INSERT_AFTER(p, te, tqe_q);
331 }
332
333 present:
334 /*
335 * Present data to user, advancing rcv_nxt through
336 * completed sequence space.
337 */
338 if (!TCPS_HAVEESTABLISHED(tp->t_state))
339 return (0);
340 q = LIST_FIRST(&tp->t_segq);
341 if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
342 return (0);
343 SOCKBUF_LOCK(&so->so_rcv);
344 do {
345 tp->rcv_nxt += q->tqe_len;
346 flags = q->tqe_th->th_flags & TH_FIN;
347 nq = LIST_NEXT(q, tqe_q);
348 LIST_REMOVE(q, tqe_q);
349 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
350 m_freem(q->tqe_m);
351 else
352 sbappendstream_locked(&so->so_rcv, q->tqe_m);
353 if (q != &tqs)
354 uma_zfree(tcp_reass_zone, q);
355 tp->t_segqlen--;
356 q = nq;
357 } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
358 ND6_HINT(tp);
359 sorwakeup_locked(so);
360 return (flags);
361 }
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