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.
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27 * modification, are permitted provided that the following conditions
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35 * may be used to endorse or promote products derived from this software
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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)
112 thflags &= (TH_CWR|TH_ECE);
114 if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) &&
116 tp->t_flags2 |= TF2_ECN_PERMIT;
117 TCPSTAT_INC(tcps_ecn_shs);
122 * Handle parallel SYN for ECN
125 tcp_ecn_input_parallel_syn(struct tcpcb *tp, uint16_t thflags, int iptos)
127 if (thflags & TH_ACK)
129 if (V_tcp_do_ecn == 0)
131 if ((V_tcp_do_ecn == 1) || (V_tcp_do_ecn == 2)) {
132 /* RFC3168 ECN handling */
133 if ((thflags & (TH_CWR | TH_ECE)) == (TH_CWR | TH_ECE)) {
134 tp->t_flags2 |= TF2_ECN_PERMIT;
135 tp->t_flags2 |= TF2_ECN_SND_ECE;
136 TCPSTAT_INC(tcps_ecn_shs);
142 * TCP ECN processing.
145 tcp_ecn_input_segment(struct tcpcb *tp, uint16_t thflags, int iptos)
149 if (tp->t_flags2 & TF2_ECN_PERMIT) {
150 switch (iptos & IPTOS_ECN_MASK) {
152 TCPSTAT_INC(tcps_ecn_ce);
155 TCPSTAT_INC(tcps_ecn_ect0);
158 TCPSTAT_INC(tcps_ecn_ect1);
162 /* RFC3168 ECN handling */
163 if (thflags & TH_ECE)
165 if (thflags & TH_CWR) {
166 tp->t_flags2 &= ~TF2_ECN_SND_ECE;
167 tp->t_flags |= TF_ACKNOW;
169 if ((iptos & IPTOS_ECN_MASK) == IPTOS_ECN_CE)
170 tp->t_flags2 |= TF2_ECN_SND_ECE;
172 /* Process a packet differently from RFC3168. */
173 cc_ecnpkt_handler_flags(tp, thflags, iptos);
180 * Send ECN setup <SYN> packet header flags
183 tcp_ecn_output_syn_sent(struct tcpcb *tp)
185 uint16_t thflags = 0;
187 if (V_tcp_do_ecn == 1) {
188 /* Send a RFC3168 ECN setup <SYN> packet */
189 if (tp->t_rxtshift >= 1) {
190 if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
191 thflags = TH_ECE|TH_CWR;
193 thflags = TH_ECE|TH_CWR;
200 * output processing of ECN feature
201 * returning IP ECN header codepoint
204 tcp_ecn_output_established(struct tcpcb *tp, uint16_t *thflags, int len, bool rxmit)
206 int ipecn = IPTOS_ECN_NOTECT;
210 * If the peer has ECN, mark data packets with
211 * ECN capable transmission (ECT).
212 * Ignore pure control packets, retransmissions
215 newdata = (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) &&
217 !((tp->t_flags & TF_FORCEDATA) && len == 1));
219 ipecn = IPTOS_ECN_ECT0;
220 TCPSTAT_INC(tcps_ecn_ect0);
223 * Reply with proper ECN notifications.
226 (tp->t_flags2 & TF2_ECN_SND_CWR)) {
228 tp->t_flags2 &= ~TF2_ECN_SND_CWR;
230 if (tp->t_flags2 & TF2_ECN_SND_ECE)
237 * Set up the ECN related tcpcb fields from
241 tcp_ecn_syncache_socket(struct tcpcb *tp, struct syncache *sc)
243 if (sc->sc_flags & SCF_ECN_MASK) {
244 switch (sc->sc_flags & SCF_ECN_MASK) {
246 tp->t_flags2 |= TF2_ECN_PERMIT;
248 /* undefined SCF codepoint */
256 * Process a <SYN> packets ECN information, and provide the
257 * syncache with the relevant information.
260 tcp_ecn_syncache_add(uint16_t thflags, int iptos)
264 switch (thflags & (TH_CWR|TH_ECE)) {
269 case (TH_CWR|TH_ECE):
279 * Set up the ECN information for the <SYN,ACK> from
280 * syncache information.
283 tcp_ecn_syncache_respond(uint16_t thflags, struct syncache *sc)
285 if ((thflags & TH_SYN) &&
286 (sc->sc_flags & SCF_ECN_MASK)) {
287 switch (sc->sc_flags & SCF_ECN_MASK) {
289 thflags |= (0 | TH_ECE);
290 TCPSTAT_INC(tcps_ecn_shs);
292 /* undefined SCF codepoint */