2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
5 * The Regents of the University of California. All rights reserved.
6 * Copyright (c) 2007-2008,2010
7 * Swinburne University of Technology, Melbourne, Australia.
8 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
9 * Copyright (c) 2010 The FreeBSD Foundation
10 * Copyright (c) 2010-2011 Juniper Networks, Inc.
11 * Copyright (c) 2019 Richard Scheffenegger <srichard@netapp.com>
12 * All rights reserved.
14 * Portions of this software were developed at the Centre for Advanced Internet
15 * Architectures, Swinburne University of Technology, by Lawrence Stewart,
16 * James Healy and David Hayes, made possible in part by a grant from the Cisco
17 * University Research Program Fund at Community Foundation Silicon Valley.
19 * Portions of this software were developed at the Centre for Advanced
20 * Internet Architectures, Swinburne University of Technology, Melbourne,
21 * Australia by David Hayes under sponsorship from the FreeBSD Foundation.
23 * Portions of this software were developed by Robert N. M. Watson under
24 * contract to Juniper Networks, Inc.
26 * Redistribution and use in source and binary forms, with or without
27 * modification, are permitted provided that the following conditions
29 * 1. Redistributions of source code must retain the above copyright
30 * notice, this list of conditions and the following disclaimer.
31 * 2. Redistributions in binary form must reproduce the above copyright
32 * notice, this list of conditions and the following disclaimer in the
33 * documentation and/or other materials provided with the distribution.
34 * 3. Neither the name of the University nor the names of its contributors
35 * may be used to endorse or promote products derived from this software
36 * without specific prior written permission.
38 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
39 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
40 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
41 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
42 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
43 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
44 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
45 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
46 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
47 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50 * @(#)tcp_ecn.c 8.12 (Berkeley) 5/24/95
54 * Utility functions to deal with Explicit Congestion Notification in TCP
55 * implementing the essential parts of the Accurate ECN extension
56 * https://tools.ietf.org/html/draft-ietf-tcpm-accurate-ecn-09
59 #include <sys/cdefs.h>
60 __FBSDID("$FreeBSD$");
63 #include "opt_inet6.h"
64 #include "opt_tcpdebug.h"
66 #include <sys/param.h>
67 #include <sys/systm.h>
68 #include <sys/kernel.h>
69 #include <sys/sysctl.h>
70 #include <sys/malloc.h>
72 #include <sys/socket.h>
73 #include <sys/socketvar.h>
75 #include <machine/cpu.h>
80 #include <net/if_var.h>
81 #include <net/route.h>
84 #include <netinet/in.h>
85 #include <netinet/in_systm.h>
86 #include <netinet/ip.h>
87 #include <netinet/in_var.h>
88 #include <netinet/in_pcb.h>
89 #include <netinet/ip_var.h>
90 #include <netinet/ip6.h>
91 #include <netinet/icmp6.h>
92 #include <netinet6/nd6.h>
93 #include <netinet6/ip6_var.h>
94 #include <netinet6/in6_pcb.h>
95 #include <netinet/tcp.h>
96 #include <netinet/tcp_fsm.h>
97 #include <netinet/tcp_seq.h>
98 #include <netinet/tcp_var.h>
99 #include <netinet/tcp_syncache.h>
100 #include <netinet/tcp_timer.h>
101 #include <netinet6/tcp6_var.h>
102 #include <netinet/tcpip.h>
103 #include <netinet/tcp_ecn.h>
107 * Process incoming SYN,ACK packet
110 tcp_ecn_input_syn_sent(struct tcpcb *tp, uint16_t thflags, int iptos)
113 if (V_tcp_do_ecn == 0)
115 if ((V_tcp_do_ecn == 1) ||
116 (V_tcp_do_ecn == 2)) {
117 /* RFC3168 ECN handling */
118 if ((thflags & (TH_CWR | TH_ECE)) == (0 | TH_ECE)) {
119 tp->t_flags2 |= TF2_ECN_PERMIT;
120 TCPSTAT_INC(tcps_ecn_shs);
123 /* decoding Accurate ECN according to table in section 3.1.1 */
124 if ((V_tcp_do_ecn == 3) ||
125 (V_tcp_do_ecn == 4)) {
127 * on the SYN,ACK, process the AccECN
128 * flags indicating the state the SYN
130 * Reactions to Path ECN mangling can
133 switch (thflags & (TH_AE | TH_CWR | TH_ECE)) {
136 tp->t_flags2 |= TF2_ECN_PERMIT;
137 TCPSTAT_INC(tcps_ecn_shs);
141 tp->t_flags2 |= TF2_ACE_PERMIT;
143 TCPSTAT_INC(tcps_ecn_shs);
144 TCPSTAT_INC(tcps_ace_nect);
148 tp->t_flags2 |= TF2_ACE_PERMIT;
150 TCPSTAT_INC(tcps_ecn_shs);
151 TCPSTAT_INC(tcps_ace_ect0);
154 case (0|TH_CWR|TH_ECE):
155 tp->t_flags2 |= TF2_ACE_PERMIT;
157 TCPSTAT_INC(tcps_ecn_shs);
158 TCPSTAT_INC(tcps_ace_ect1);
161 case (TH_AE|TH_CWR|0):
162 tp->t_flags2 |= TF2_ACE_PERMIT;
165 * reduce the IW to 2 MSS (to
166 * account for delayed acks) if
167 * the SYN,ACK was CE marked
169 tp->snd_cwnd = 2 * tcp_maxseg(tp);
170 TCPSTAT_INC(tcps_ecn_shs);
171 TCPSTAT_INC(tcps_ace_nect);
177 * Set the AccECN Codepoints on
178 * the outgoing <ACK> to the ECN
179 * state of the <SYN,ACK>
180 * according to table 3 in the
183 switch (iptos & IPTOS_ECN_MASK) {
184 case (IPTOS_ECN_NOTECT):
187 case (IPTOS_ECN_ECT0):
190 case (IPTOS_ECN_ECT1):
201 * Handle parallel SYN for ECN
204 tcp_ecn_input_parallel_syn(struct tcpcb *tp, uint16_t thflags, int iptos)
206 if (thflags & TH_ACK)
208 if (V_tcp_do_ecn == 0)
210 if ((V_tcp_do_ecn == 1) ||
211 (V_tcp_do_ecn == 2)) {
212 /* RFC3168 ECN handling */
213 if ((thflags & (TH_CWR | TH_ECE)) == (TH_CWR | TH_ECE)) {
214 tp->t_flags2 |= TF2_ECN_PERMIT;
215 tp->t_flags2 |= TF2_ECN_SND_ECE;
216 TCPSTAT_INC(tcps_ecn_shs);
219 if ((V_tcp_do_ecn == 3) ||
220 (V_tcp_do_ecn == 4)) {
221 /* AccECN handling */
222 switch (thflags & (TH_AE | TH_CWR | TH_ECE)) {
226 case (0|TH_CWR|TH_ECE):
227 tp->t_flags2 |= TF2_ECN_PERMIT;
228 tp->t_flags2 |= TF2_ECN_SND_ECE;
229 TCPSTAT_INC(tcps_ecn_shs);
231 case (TH_AE|TH_CWR|TH_ECE):
232 tp->t_flags2 |= TF2_ACE_PERMIT;
233 TCPSTAT_INC(tcps_ecn_shs);
235 * Set the AccECN Codepoints on
236 * the outgoing <ACK> to the ECN
237 * state of the <SYN,ACK>
238 * according to table 3 in the
241 switch (iptos & IPTOS_ECN_MASK) {
242 case (IPTOS_ECN_NOTECT):
245 case (IPTOS_ECN_ECT0):
248 case (IPTOS_ECN_ECT1):
261 * TCP ECN processing.
264 tcp_ecn_input_segment(struct tcpcb *tp, uint16_t thflags, int iptos)
268 if (tp->t_flags2 & (TF2_ECN_PERMIT | TF2_ACE_PERMIT)) {
269 switch (iptos & IPTOS_ECN_MASK) {
271 TCPSTAT_INC(tcps_ecn_ce);
274 TCPSTAT_INC(tcps_ecn_ect0);
277 TCPSTAT_INC(tcps_ecn_ect1);
281 if (tp->t_flags2 & TF2_ACE_PERMIT) {
282 if ((iptos & IPTOS_ECN_MASK) == IPTOS_ECN_CE)
284 if (tp->t_flags2 & TF2_ECN_PERMIT) {
285 delta_ace = (tcp_ecn_get_ace(thflags) + 8 -
286 (tp->t_scep & 0x07)) & 0x07;
287 tp->t_scep += delta_ace;
290 * process the final ACK of the 3WHS
291 * see table 3 in draft-ietf-tcpm-accurate-ecn
293 switch (tcp_ecn_get_ace(thflags)) {
295 /* nonECT SYN or SYN,ACK */
298 /* ECT1 SYN or SYN,ACK */
301 /* ECT0 SYN or SYN,ACK */
305 /* CE SYN or SYN,ACK */
307 tp->snd_cwnd = 2 * tcp_maxseg(tp);
310 /* mangled AccECN handshake */
314 tp->t_flags2 |= TF2_ECN_PERMIT;
317 /* RFC3168 ECN handling */
318 if (thflags & TH_ECE)
320 if (thflags & TH_CWR) {
321 tp->t_flags2 &= ~TF2_ECN_SND_ECE;
322 tp->t_flags |= TF_ACKNOW;
324 if ((iptos & IPTOS_ECN_MASK) == IPTOS_ECN_CE)
325 tp->t_flags2 |= TF2_ECN_SND_ECE;
328 /* Process a packet differently from RFC3168. */
329 cc_ecnpkt_handler_flags(tp, thflags, iptos);
336 * Send ECN setup <SYN> packet header flags
339 tcp_ecn_output_syn_sent(struct tcpcb *tp)
341 uint16_t thflags = 0;
343 if (V_tcp_do_ecn == 0)
345 if (V_tcp_do_ecn == 1) {
346 /* Send a RFC3168 ECN setup <SYN> packet */
347 if (tp->t_rxtshift >= 1) {
348 if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
349 thflags = TH_ECE|TH_CWR;
351 thflags = TH_ECE|TH_CWR;
353 if (V_tcp_do_ecn == 3) {
354 /* Send an Accurate ECN setup <SYN> packet */
355 if (tp->t_rxtshift >= 1) {
356 if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
357 thflags = TH_ECE|TH_CWR|TH_AE;
359 thflags = TH_ECE|TH_CWR|TH_AE;
366 * output processing of ECN feature
367 * returning IP ECN header codepoint
370 tcp_ecn_output_established(struct tcpcb *tp, uint16_t *thflags, int len, bool rxmit)
372 int ipecn = IPTOS_ECN_NOTECT;
376 * If the peer has ECN, mark data packets with
377 * ECN capable transmission (ECT).
378 * Ignore pure control packets, retransmissions
381 newdata = (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) &&
383 !((tp->t_flags & TF_FORCEDATA) && len == 1));
384 /* RFC3168 ECN marking, only new data segments */
386 ipecn = IPTOS_ECN_ECT0;
387 TCPSTAT_INC(tcps_ecn_ect0);
390 * Reply with proper ECN notifications.
392 if (tp->t_flags2 & TF2_ACE_PERMIT) {
393 *thflags &= ~(TH_AE|TH_CWR|TH_ECE);
394 if (tp->t_rcep & 0x01)
396 if (tp->t_rcep & 0x02)
398 if (tp->t_rcep & 0x04)
400 if (!(tp->t_flags2 & TF2_ECN_PERMIT)) {
402 * here we process the final
405 if (tp->t_rcep == 0b110) {
410 tp->t_flags2 |= TF2_ECN_PERMIT;
414 (tp->t_flags2 & TF2_ECN_SND_CWR)) {
416 tp->t_flags2 &= ~TF2_ECN_SND_CWR;
418 if (tp->t_flags2 & TF2_ECN_SND_ECE)
426 * Set up the ECN related tcpcb fields from
430 tcp_ecn_syncache_socket(struct tcpcb *tp, struct syncache *sc)
432 if (sc->sc_flags & SCF_ECN_MASK) {
433 switch (sc->sc_flags & SCF_ECN_MASK) {
435 tp->t_flags2 |= TF2_ECN_PERMIT;
442 tp->t_flags2 |= TF2_ACE_PERMIT;
447 tp->t_flags2 |= TF2_ACE_PERMIT;
451 /* undefined SCF codepoint */
459 * Process a <SYN> packets ECN information, and provide the
460 * syncache with the relevant information.
463 tcp_ecn_syncache_add(uint16_t thflags, int iptos)
467 switch (thflags & (TH_AE|TH_CWR|TH_ECE)) {
472 case (0|TH_CWR|TH_ECE):
476 case (TH_AE|TH_CWR|TH_ECE):
477 if ((V_tcp_do_ecn == 3) ||
478 (V_tcp_do_ecn == 4)) {
479 switch (iptos & IPTOS_ECN_MASK) {
481 scflags = SCF_ACE_CE;
489 case IPTOS_ECN_NOTECT:
496 /* Default Case (section 3.1.2) */
498 if ((V_tcp_do_ecn == 3) ||
499 (V_tcp_do_ecn == 4)) {
500 switch (iptos & IPTOS_ECN_MASK) {
502 scflags = SCF_ACE_CE;
510 case IPTOS_ECN_NOTECT:
521 * Set up the ECN information for the <SYN,ACK> from
522 * syncache information.
525 tcp_ecn_syncache_respond(uint16_t thflags, struct syncache *sc)
527 if ((thflags & TH_SYN) &&
528 (sc->sc_flags & SCF_ECN_MASK)) {
529 switch (sc->sc_flags & SCF_ECN_MASK) {
531 thflags |= (0 | 0 | TH_ECE);
532 TCPSTAT_INC(tcps_ecn_shs);
535 thflags |= (0 | TH_CWR | 0);
536 TCPSTAT_INC(tcps_ecn_shs);
537 TCPSTAT_INC(tcps_ace_nect);
540 thflags |= (TH_AE | 0 | 0);
541 TCPSTAT_INC(tcps_ecn_shs);
542 TCPSTAT_INC(tcps_ace_ect0);
545 thflags |= (0 | TH_ECE | TH_CWR);
546 TCPSTAT_INC(tcps_ecn_shs);
547 TCPSTAT_INC(tcps_ace_ect1);
550 thflags |= (TH_AE | TH_CWR | 0);
551 TCPSTAT_INC(tcps_ecn_shs);
552 TCPSTAT_INC(tcps_ace_ce);
554 /* undefined SCF codepoint */
563 tcp_ecn_get_ace(uint16_t thflags)
567 if (thflags & TH_ECE)
569 if (thflags & TH_CWR)