xref: /freebsd/sys/netinet/tcp_ecn.c (revision 2d05a1c81b2cbb5468a242d0add44f850aa31811)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
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.
13  *
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.
18  *
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.
22  *
23  * Portions of this software were developed by Robert N. M. Watson under
24  * contract to Juniper Networks, Inc.
25  *
26  * Redistribution and use in source and binary forms, with or without
27  * modification, are permitted provided that the following conditions
28  * are met:
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.
37  *
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
48  * SUCH DAMAGE.
49  */
50 
51 /*
52  * Utility functions to deal with Explicit Congestion Notification in TCP
53  * implementing the essential parts of the Accurate ECN extension
54  * https://tools.ietf.org/html/draft-ietf-tcpm-accurate-ecn-09
55  */
56 
57 #include <sys/cdefs.h>
58 #include "opt_inet.h"
59 #include "opt_inet6.h"
60 
61 #include <sys/param.h>
62 #include <sys/systm.h>
63 #include <sys/kernel.h>
64 #include <sys/sysctl.h>
65 #include <sys/malloc.h>
66 #include <sys/mbuf.h>
67 #include <sys/socket.h>
68 #include <sys/socketvar.h>
69 
70 #include <machine/cpu.h>
71 
72 #include <vm/uma.h>
73 
74 #include <net/if.h>
75 #include <net/if_var.h>
76 #include <net/route.h>
77 #include <net/vnet.h>
78 
79 #include <netinet/in.h>
80 #include <netinet/in_systm.h>
81 #include <netinet/ip.h>
82 #include <netinet/in_var.h>
83 #include <netinet/in_pcb.h>
84 #include <netinet/ip_var.h>
85 #include <netinet/ip6.h>
86 #include <netinet/icmp6.h>
87 #include <netinet6/nd6.h>
88 #include <netinet6/ip6_var.h>
89 #include <netinet6/in6_pcb.h>
90 #include <netinet/tcp.h>
91 #include <netinet/tcp_fsm.h>
92 #include <netinet/tcp_seq.h>
93 #include <netinet/tcp_var.h>
94 #include <netinet/tcp_syncache.h>
95 #include <netinet/tcp_timer.h>
96 #include <netinet/tcpip.h>
97 #include <netinet/tcp_ecn.h>
98 
99 static inline int  tcp_ecn_get_ace(uint16_t);
100 static inline void tcp_ecn_set_ace(uint16_t *, uint32_t);
101 
102 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn,
103     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
104     "TCP ECN");
105 
106 VNET_DEFINE(int, tcp_do_ecn) = 2;
107 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable,
108     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_do_ecn), 0,
109     "TCP ECN support");
110 
111 VNET_DEFINE(int, tcp_ecn_maxretries) = 1;
112 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries,
113     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_ecn_maxretries), 0,
114     "Max retries before giving up on ECN");
115 
116 /*
117  * Process incoming SYN,ACK packet
118  */
119 void
tcp_ecn_input_syn_sent(struct tcpcb * tp,uint16_t thflags,int iptos)120 tcp_ecn_input_syn_sent(struct tcpcb *tp, uint16_t thflags, int iptos)
121 {
122 	switch (V_tcp_do_ecn) {
123 	case 0:
124 		return;
125 	case 1:
126 		/* FALLTHROUGH */
127 	case 2:
128 		/* RFC3168 ECN handling */
129 		if ((thflags & (TH_CWR | TH_ECE)) == (0 | TH_ECE)) {
130 			tp->t_flags2 |= TF2_ECN_PERMIT;
131 			tp->t_flags2 &= ~TF2_ACE_PERMIT;
132 			TCPSTAT_INC(tcps_ecn_shs);
133 		}
134 		break;
135 	case 3:
136 		/* FALLTHROUGH */
137 	case 4:
138 		/*
139 		 * Decoding Accurate ECN according to
140 		 * table in section 3.1.1
141 		 *
142 		 * On the SYN,ACK, process the AccECN
143 		 * flags indicating the state the SYN
144 		 * was delivered.
145 		 * Reactions to Path ECN mangling can
146 		 * come here.
147 		 */
148 		switch (thflags & (TH_AE | TH_CWR | TH_ECE)) {
149 		/* RFC3168 SYN */
150 		case (0|0|TH_ECE):
151 			tp->t_flags2 |= TF2_ECN_PERMIT;
152 			tp->t_flags2 &= ~TF2_ACE_PERMIT;
153 			TCPSTAT_INC(tcps_ecn_shs);
154 			break;
155 		/* non-ECT SYN */
156 		case (0|TH_CWR|0):
157 			tp->t_flags2 |= TF2_ACE_PERMIT;
158 			tp->t_flags2 &= ~TF2_ECN_PERMIT;
159 			tp->t_scep = 5;
160 			TCPSTAT_INC(tcps_ecn_shs);
161 			TCPSTAT_INC(tcps_ace_nect);
162 			break;
163 		/* ECT0 SYN */
164 		case (TH_AE|0|0):
165 			tp->t_flags2 |= TF2_ACE_PERMIT;
166 			tp->t_flags2 &= ~TF2_ECN_PERMIT;
167 			tp->t_scep = 5;
168 			TCPSTAT_INC(tcps_ecn_shs);
169 			TCPSTAT_INC(tcps_ace_ect0);
170 			break;
171 		/* ECT1 SYN */
172 		case (0|TH_CWR|TH_ECE):
173 			tp->t_flags2 |= TF2_ACE_PERMIT;
174 			tp->t_flags2 &= ~TF2_ECN_PERMIT;
175 			tp->t_scep = 5;
176 			TCPSTAT_INC(tcps_ecn_shs);
177 			TCPSTAT_INC(tcps_ace_ect1);
178 			break;
179 		/* CE SYN */
180 		case (TH_AE|TH_CWR|0):
181 			tp->t_flags2 |= TF2_ACE_PERMIT;
182 			tp->t_flags2 &= ~TF2_ECN_PERMIT;
183 			tp->t_scep = 6;
184 			/*
185 			 * reduce the IW to 2 MSS (to
186 			 * account for delayed acks) if
187 			 * the SYN,ACK was CE marked
188 			 */
189 			tp->snd_cwnd = 2 * tcp_maxseg(tp);
190 			TCPSTAT_INC(tcps_ecn_shs);
191 			TCPSTAT_INC(tcps_ace_nect);
192 			break;
193 		default:
194 			tp->t_flags2 &= ~(TF2_ECN_PERMIT | TF2_ACE_PERMIT);
195 			break;
196 		}
197 		/*
198 		 * Set the AccECN Codepoints on
199 		 * the outgoing <ACK> to the ECN
200 		 * state of the <SYN,ACK>
201 		 * according to table 3 in the
202 		 * AccECN draft
203 		 */
204 		switch (iptos & IPTOS_ECN_MASK) {
205 		case (IPTOS_ECN_NOTECT):
206 			tp->t_rcep = 0b010;
207 			break;
208 		case (IPTOS_ECN_ECT0):
209 			tp->t_rcep = 0b100;
210 			break;
211 		case (IPTOS_ECN_ECT1):
212 			tp->t_rcep = 0b011;
213 			break;
214 		case (IPTOS_ECN_CE):
215 			tp->t_rcep = 0b110;
216 			break;
217 		}
218 		break;
219 	}
220 }
221 
222 /*
223  * Handle parallel SYN for ECN
224  */
225 void
tcp_ecn_input_parallel_syn(struct tcpcb * tp,uint16_t thflags,int iptos)226 tcp_ecn_input_parallel_syn(struct tcpcb *tp, uint16_t thflags, int iptos)
227 {
228 	if (thflags & TH_ACK)
229 		return;
230 	switch (V_tcp_do_ecn) {
231 	case 0:
232 		return;
233 	case 1:
234 		/* FALLTHROUGH */
235 	case 2:
236 		/* RFC3168 ECN handling */
237 		if ((thflags & (TH_CWR | TH_ECE)) == (TH_CWR | TH_ECE)) {
238 			tp->t_flags2 |= TF2_ECN_PERMIT;
239 			tp->t_flags2 &= ~TF2_ACE_PERMIT;
240 			tp->t_flags2 |= TF2_ECN_SND_ECE;
241 			TCPSTAT_INC(tcps_ecn_shs);
242 		}
243 		break;
244 	case 3:
245 		/* FALLTHROUGH */
246 	case 4:
247 		/* AccECN handling */
248 		switch (thflags & (TH_AE | TH_CWR | TH_ECE)) {
249 		default:
250 		case (0|0|0):
251 			tp->t_flags2 &= ~(TF2_ECN_PERMIT | TF2_ACE_PERMIT);
252 			break;
253 		case (0|TH_CWR|TH_ECE):
254 			tp->t_flags2 |= TF2_ECN_PERMIT;
255 			tp->t_flags2 &= ~TF2_ACE_PERMIT;
256 			tp->t_flags2 |= TF2_ECN_SND_ECE;
257 			TCPSTAT_INC(tcps_ecn_shs);
258 			break;
259 		case (TH_AE|TH_CWR|TH_ECE):
260 			tp->t_flags2 |= TF2_ACE_PERMIT;
261 			tp->t_flags2 &= ~TF2_ECN_PERMIT;
262 			TCPSTAT_INC(tcps_ecn_shs);
263 			/*
264 			 * Set the AccECN Codepoints on
265 			 * the outgoing <ACK> to the ECN
266 			 * state of the <SYN,ACK>
267 			 * according to table 3 in the
268 			 * AccECN draft
269 			 */
270 			switch (iptos & IPTOS_ECN_MASK) {
271 			case (IPTOS_ECN_NOTECT):
272 				tp->t_rcep = 0b010;
273 				break;
274 			case (IPTOS_ECN_ECT0):
275 				tp->t_rcep = 0b100;
276 				break;
277 			case (IPTOS_ECN_ECT1):
278 				tp->t_rcep = 0b011;
279 				break;
280 			case (IPTOS_ECN_CE):
281 				tp->t_rcep = 0b110;
282 				break;
283 			}
284 			break;
285 		}
286 		break;
287 	}
288 }
289 
290 /*
291  * TCP ECN processing.
292  */
293 int
tcp_ecn_input_segment(struct tcpcb * tp,uint16_t thflags,int tlen,int pkts,int iptos)294 tcp_ecn_input_segment(struct tcpcb *tp, uint16_t thflags, int tlen, int pkts, int iptos)
295 {
296 	int delta_cep = 0;
297 
298 	switch (iptos & IPTOS_ECN_MASK) {
299 	case IPTOS_ECN_CE:
300 		TCPSTAT_INC(tcps_ecn_rcvce);
301 		break;
302 	case IPTOS_ECN_ECT0:
303 		TCPSTAT_INC(tcps_ecn_rcvect0);
304 		break;
305 	case IPTOS_ECN_ECT1:
306 		TCPSTAT_INC(tcps_ecn_rcvect1);
307 		break;
308 	}
309 
310 	if (tp->t_flags2 & (TF2_ECN_PERMIT | TF2_ACE_PERMIT)) {
311 		if (tp->t_flags2 & TF2_ACE_PERMIT) {
312 			if ((iptos & IPTOS_ECN_MASK) == IPTOS_ECN_CE)
313 				tp->t_rcep += 1;
314 			if (tp->t_flags2 & TF2_ECN_PERMIT) {
315 				delta_cep = (tcp_ecn_get_ace(thflags) + 8 -
316 					    (tp->t_scep & 7)) & 7;
317 				if (delta_cep < pkts)
318 					delta_cep = pkts -
319 					    ((pkts - delta_cep) & 7);
320 				tp->t_scep += delta_cep;
321 			} else {
322 				/*
323 				 * process the final ACK of the 3WHS
324 				 * see table 3 in draft-ietf-tcpm-accurate-ecn
325 				 */
326 				switch (tcp_ecn_get_ace(thflags)) {
327 				case 0b010:
328 					/* nonECT SYN or SYN,ACK */
329 					/* FALLTHROUGH */
330 				case 0b011:
331 					/* ECT1 SYN or SYN,ACK */
332 					/* FALLTHROUGH */
333 				case 0b100:
334 					/* ECT0 SYN or SYN,ACK */
335 					tp->t_scep = 5;
336 					break;
337 				case 0b110:
338 					/* CE SYN or SYN,ACK */
339 					tp->t_scep = 6;
340 					tp->snd_cwnd = 2 * tcp_maxseg(tp);
341 					break;
342 				default:
343 					/* mangled AccECN handshake */
344 					tp->t_scep = 5;
345 					break;
346 				}
347 				tp->t_flags2 |= TF2_ECN_PERMIT;
348 			}
349 		} else {
350 			/* RFC3168 ECN handling */
351 			if ((thflags & (TH_SYN | TH_ECE)) == TH_ECE) {
352 				delta_cep = 1;
353 				tp->t_scep++;
354 			}
355 			if (thflags & TH_CWR) {
356 				tp->t_flags2 &= ~TF2_ECN_SND_ECE;
357 				tp->t_flags |= TF_ACKNOW;
358 			}
359 			if ((iptos & IPTOS_ECN_MASK) == IPTOS_ECN_CE)
360 				tp->t_flags2 |= TF2_ECN_SND_ECE;
361 		}
362 
363 		/* Process a packet differently from RFC3168. */
364 		cc_ecnpkt_handler_flags(tp, thflags, iptos);
365 	}
366 
367 	return delta_cep;
368 }
369 
370 /*
371  * Send ECN setup <SYN> packet header flags
372  */
373 uint16_t
tcp_ecn_output_syn_sent(struct tcpcb * tp)374 tcp_ecn_output_syn_sent(struct tcpcb *tp)
375 {
376 	uint16_t thflags = 0;
377 
378 	if (V_tcp_do_ecn == 0)
379 		return thflags;
380 	if (V_tcp_do_ecn == 1) {
381 		/* Send a RFC3168 ECN setup <SYN> packet */
382 		if (tp->t_rxtshift >= 1) {
383 			if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
384 				thflags = TH_ECE|TH_CWR;
385 		} else
386 			thflags = TH_ECE|TH_CWR;
387 	} else if (V_tcp_do_ecn == 3) {
388 		/* Send an Accurate ECN setup <SYN> packet */
389 		if (tp->t_rxtshift >= 1) {
390 			if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
391 				thflags = TH_ECE|TH_CWR|TH_AE;
392 		} else
393 			thflags = TH_ECE|TH_CWR|TH_AE;
394 	}
395 
396 	return thflags;
397 }
398 
399 /*
400  * output processing of ECN feature
401  * returning IP ECN header codepoint
402  */
403 int
tcp_ecn_output_established(struct tcpcb * tp,uint16_t * thflags,int len,bool rxmit)404 tcp_ecn_output_established(struct tcpcb *tp, uint16_t *thflags, int len, bool rxmit)
405 {
406 	int ipecn = IPTOS_ECN_NOTECT;
407 	bool newdata;
408 
409 	/*
410 	 * If the peer has ECN, mark data packets with
411 	 * ECN capable transmission (ECT).
412 	 * Ignore pure control packets, retransmissions
413 	 * and window probes.
414 	 */
415 	newdata = (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) &&
416 		    !rxmit &&
417 		    !((tp->t_flags & TF_FORCEDATA) && len == 1));
418 	/* RFC3168 ECN marking, only new data segments */
419 	if (newdata) {
420 		if (tp->t_flags2 & TF2_ECN_USE_ECT1) {
421 			ipecn = IPTOS_ECN_ECT1;
422 			TCPSTAT_INC(tcps_ecn_sndect1);
423 		} else {
424 			ipecn = IPTOS_ECN_ECT0;
425 			TCPSTAT_INC(tcps_ecn_sndect0);
426 		}
427 	}
428 	/*
429 	 * Reply with proper ECN notifications.
430 	 */
431 	if (tp->t_flags2 & TF2_ACE_PERMIT) {
432 		tcp_ecn_set_ace(thflags, tp->t_rcep);
433 		if (!(tp->t_flags2 & TF2_ECN_PERMIT)) {
434 			/*
435 			 * here we process the final
436 			 * ACK of the 3WHS
437 			 */
438 			if (tp->t_rcep == 0b110) {
439 				tp->t_rcep = 6;
440 			} else {
441 				tp->t_rcep = 5;
442 			}
443 			tp->t_flags2 |= TF2_ECN_PERMIT;
444 		}
445 	} else {
446 		if (newdata &&
447 		    (tp->t_flags2 & TF2_ECN_SND_CWR)) {
448 			*thflags |= TH_CWR;
449 			tp->t_flags2 &= ~TF2_ECN_SND_CWR;
450 		}
451 		if (tp->t_flags2 & TF2_ECN_SND_ECE)
452 			*thflags |= TH_ECE;
453 	}
454 
455 	return ipecn;
456 }
457 
458 /*
459  * Set up the ECN related tcpcb fields from
460  * a syncache entry
461  */
462 void
tcp_ecn_syncache_socket(struct tcpcb * tp,struct syncache * sc)463 tcp_ecn_syncache_socket(struct tcpcb *tp, struct syncache *sc)
464 {
465 	if (sc->sc_flags & SCF_ECN_MASK) {
466 		switch (sc->sc_flags & SCF_ECN_MASK) {
467 		case SCF_ECN:
468 			tp->t_flags2 |= TF2_ECN_PERMIT;
469 			break;
470 		case SCF_ACE_N:
471 			/* FALLTHROUGH */
472 		case SCF_ACE_0:
473 			/* FALLTHROUGH */
474 		case SCF_ACE_1:
475 			tp->t_flags2 |= TF2_ACE_PERMIT;
476 			tp->t_scep = 5;
477 			tp->t_rcep = 5;
478 			break;
479 		case SCF_ACE_CE:
480 			tp->t_flags2 |= TF2_ACE_PERMIT;
481 			tp->t_scep = 6;
482 			tp->t_rcep = 6;
483 			break;
484 		}
485 	}
486 }
487 
488 /*
489  * Process a <SYN> packets ECN information, and provide the
490  * syncache with the relevant information.
491  */
492 int
tcp_ecn_syncache_add(uint16_t thflags,int iptos)493 tcp_ecn_syncache_add(uint16_t thflags, int iptos)
494 {
495 	int scflags = 0;
496 
497 	switch (iptos & IPTOS_ECN_MASK) {
498 	case IPTOS_ECN_CE:
499 		TCPSTAT_INC(tcps_ecn_rcvce);
500 		break;
501 	case IPTOS_ECN_ECT0:
502 		TCPSTAT_INC(tcps_ecn_rcvect0);
503 		break;
504 	case IPTOS_ECN_ECT1:
505 		TCPSTAT_INC(tcps_ecn_rcvect1);
506 		break;
507 	}
508 
509 	switch (thflags & (TH_AE|TH_CWR|TH_ECE)) {
510 	/* no ECN */
511 	case (0|0|0):
512 		break;
513 	/* legacy ECN */
514 	case (0|TH_CWR|TH_ECE):
515 		scflags = SCF_ECN;
516 		break;
517 	/* Accurate ECN */
518 	case (TH_AE|TH_CWR|TH_ECE):
519 		if ((V_tcp_do_ecn == 3) ||
520 		    (V_tcp_do_ecn == 4)) {
521 			switch (iptos & IPTOS_ECN_MASK) {
522 			case IPTOS_ECN_CE:
523 				scflags = SCF_ACE_CE;
524 				break;
525 			case IPTOS_ECN_ECT0:
526 				scflags = SCF_ACE_0;
527 				break;
528 			case IPTOS_ECN_ECT1:
529 				scflags = SCF_ACE_1;
530 				break;
531 			case IPTOS_ECN_NOTECT:
532 				scflags = SCF_ACE_N;
533 				break;
534 			}
535 		} else
536 			scflags = SCF_ECN;
537 		break;
538 	/* Default Case (section 3.1.2) */
539 	default:
540 		if ((V_tcp_do_ecn == 3) ||
541 		    (V_tcp_do_ecn == 4)) {
542 			switch (iptos & IPTOS_ECN_MASK) {
543 			case IPTOS_ECN_CE:
544 				scflags = SCF_ACE_CE;
545 				break;
546 			case IPTOS_ECN_ECT0:
547 				scflags = SCF_ACE_0;
548 				break;
549 			case IPTOS_ECN_ECT1:
550 				scflags = SCF_ACE_1;
551 				break;
552 			case IPTOS_ECN_NOTECT:
553 				scflags = SCF_ACE_N;
554 				break;
555 			}
556 		}
557 		break;
558 	}
559 	return scflags;
560 }
561 
562 /*
563  * Set up the ECN information for the <SYN,ACK> from
564  * syncache information.
565  */
566 uint16_t
tcp_ecn_syncache_respond(uint16_t thflags,struct syncache * sc)567 tcp_ecn_syncache_respond(uint16_t thflags, struct syncache *sc)
568 {
569 	if ((thflags & TH_SYN) &&
570 	    (sc->sc_flags & SCF_ECN_MASK)) {
571 		switch (sc->sc_flags & SCF_ECN_MASK) {
572 		case SCF_ECN:
573 			thflags |= (0 | 0 | TH_ECE);
574 			TCPSTAT_INC(tcps_ecn_shs);
575 			break;
576 		case SCF_ACE_N:
577 			thflags |= (0 | TH_CWR | 0);
578 			TCPSTAT_INC(tcps_ecn_shs);
579 			TCPSTAT_INC(tcps_ace_nect);
580 			break;
581 		case SCF_ACE_0:
582 			thflags |= (TH_AE | 0 | 0);
583 			TCPSTAT_INC(tcps_ecn_shs);
584 			TCPSTAT_INC(tcps_ace_ect0);
585 			break;
586 		case SCF_ACE_1:
587 			thflags |= (0 | TH_ECE | TH_CWR);
588 			TCPSTAT_INC(tcps_ecn_shs);
589 			TCPSTAT_INC(tcps_ace_ect1);
590 			break;
591 		case SCF_ACE_CE:
592 			thflags |= (TH_AE | TH_CWR | 0);
593 			TCPSTAT_INC(tcps_ecn_shs);
594 			TCPSTAT_INC(tcps_ace_ce);
595 			break;
596 		}
597 	}
598 	return thflags;
599 }
600 
601 static inline int
tcp_ecn_get_ace(uint16_t thflags)602 tcp_ecn_get_ace(uint16_t thflags)
603 {
604 	return ((thflags & (TH_AE|TH_CWR|TH_ECE)) >> TH_ACE_SHIFT);
605 }
606 
607 static inline void
tcp_ecn_set_ace(uint16_t * thflags,uint32_t t_rcep)608 tcp_ecn_set_ace(uint16_t *thflags, uint32_t t_rcep)
609 {
610 	*thflags &= ~(TH_AE|TH_CWR|TH_ECE);
611 	*thflags |= ((t_rcep << TH_ACE_SHIFT) & (TH_AE|TH_CWR|TH_ECE));
612 }
613