1 /* SPDX-License-Identifier: GPL-2.0-or-later */ 2 #ifndef _TCP_ECN_H 3 #define _TCP_ECN_H 4 5 #include <linux/tcp.h> 6 #include <linux/skbuff.h> 7 #include <linux/bitfield.h> 8 9 #include <net/inet_connection_sock.h> 10 #include <net/sock.h> 11 #include <net/tcp.h> 12 #include <net/inet_ecn.h> 13 14 /* The highest ECN variant (Accurate ECN, ECN, or no ECN) that is 15 * attemped to be negotiated and requested for incoming connection 16 * and outgoing connection, respectively. 17 */ 18 enum tcp_ecn_mode { 19 TCP_ECN_IN_NOECN_OUT_NOECN = 0, 20 TCP_ECN_IN_ECN_OUT_ECN = 1, 21 TCP_ECN_IN_ECN_OUT_NOECN = 2, 22 TCP_ECN_IN_ACCECN_OUT_ACCECN = 3, 23 TCP_ECN_IN_ACCECN_OUT_ECN = 4, 24 TCP_ECN_IN_ACCECN_OUT_NOECN = 5, 25 }; 26 27 /* AccECN option sending when AccECN has been successfully negotiated */ 28 enum tcp_accecn_option { 29 TCP_ACCECN_OPTION_DISABLED = 0, 30 TCP_ACCECN_OPTION_MINIMUM = 1, 31 TCP_ACCECN_OPTION_FULL = 2, 32 }; 33 34 static inline void tcp_ecn_queue_cwr(struct tcp_sock *tp) 35 { 36 /* Do not set CWR if in AccECN mode! */ 37 if (tcp_ecn_mode_rfc3168(tp)) 38 tp->ecn_flags |= TCP_ECN_QUEUE_CWR; 39 } 40 41 static inline void tcp_ecn_accept_cwr(struct sock *sk, 42 const struct sk_buff *skb) 43 { 44 struct tcp_sock *tp = tcp_sk(sk); 45 46 if (tcp_ecn_mode_rfc3168(tp) && tcp_hdr(skb)->cwr) { 47 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; 48 49 /* If the sender is telling us it has entered CWR, then its 50 * cwnd may be very low (even just 1 packet), so we should ACK 51 * immediately. 52 */ 53 if (TCP_SKB_CB(skb)->seq != TCP_SKB_CB(skb)->end_seq) 54 inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW; 55 } 56 } 57 58 static inline void tcp_ecn_withdraw_cwr(struct tcp_sock *tp) 59 { 60 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR; 61 } 62 63 /* tp->accecn_fail_mode */ 64 #define TCP_ACCECN_ACE_FAIL_SEND BIT(0) 65 #define TCP_ACCECN_ACE_FAIL_RECV BIT(1) 66 #define TCP_ACCECN_OPT_FAIL_SEND BIT(2) 67 #define TCP_ACCECN_OPT_FAIL_RECV BIT(3) 68 69 static inline bool tcp_accecn_ace_fail_send(const struct tcp_sock *tp) 70 { 71 return tp->accecn_fail_mode & TCP_ACCECN_ACE_FAIL_SEND; 72 } 73 74 static inline bool tcp_accecn_ace_fail_recv(const struct tcp_sock *tp) 75 { 76 return tp->accecn_fail_mode & TCP_ACCECN_ACE_FAIL_RECV; 77 } 78 79 static inline bool tcp_accecn_opt_fail_send(const struct tcp_sock *tp) 80 { 81 return tp->accecn_fail_mode & TCP_ACCECN_OPT_FAIL_SEND; 82 } 83 84 static inline bool tcp_accecn_opt_fail_recv(const struct tcp_sock *tp) 85 { 86 return tp->accecn_fail_mode & TCP_ACCECN_OPT_FAIL_RECV; 87 } 88 89 static inline void tcp_accecn_fail_mode_set(struct tcp_sock *tp, u8 mode) 90 { 91 tp->accecn_fail_mode |= mode; 92 } 93 94 static inline u8 tcp_accecn_ace(const struct tcphdr *th) 95 { 96 return (th->ae << 2) | (th->cwr << 1) | th->ece; 97 } 98 99 /* Infer the ECT value our SYN arrived with from the echoed ACE field */ 100 static inline int tcp_accecn_extract_syn_ect(u8 ace) 101 { 102 /* Below is an excerpt from the 1st block of Table 2 of AccECN spec */ 103 static const int ace_to_ecn[8] = { 104 INET_ECN_ECT_0, /* 0b000 (Undefined) */ 105 INET_ECN_ECT_1, /* 0b001 (Undefined) */ 106 INET_ECN_NOT_ECT, /* 0b010 (Not-ECT is received) */ 107 INET_ECN_ECT_1, /* 0b011 (ECT-1 is received) */ 108 INET_ECN_ECT_0, /* 0b100 (ECT-0 is received) */ 109 INET_ECN_ECT_1, /* 0b101 (Reserved) */ 110 INET_ECN_CE, /* 0b110 (CE is received) */ 111 INET_ECN_ECT_1 /* 0b111 (Undefined) */ 112 }; 113 114 return ace_to_ecn[ace & 0x7]; 115 } 116 117 /* Check ECN field transition to detect invalid transitions */ 118 static inline bool tcp_ect_transition_valid(u8 snt, u8 rcv) 119 { 120 if (rcv == snt) 121 return true; 122 123 /* Non-ECT altered to something or something became non-ECT */ 124 if (snt == INET_ECN_NOT_ECT || rcv == INET_ECN_NOT_ECT) 125 return false; 126 /* CE -> ECT(0/1)? */ 127 if (snt == INET_ECN_CE) 128 return false; 129 return true; 130 } 131 132 static inline bool tcp_accecn_validate_syn_feedback(struct sock *sk, u8 ace, 133 u8 sent_ect) 134 { 135 u8 ect = tcp_accecn_extract_syn_ect(ace); 136 struct tcp_sock *tp = tcp_sk(sk); 137 138 if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)) 139 return true; 140 141 if (!tcp_ect_transition_valid(sent_ect, ect)) { 142 tcp_accecn_fail_mode_set(tp, TCP_ACCECN_ACE_FAIL_RECV); 143 return false; 144 } 145 146 return true; 147 } 148 149 /* Validate the 3rd ACK based on the ACE field, see Table 4 of AccECN spec */ 150 static inline void tcp_accecn_third_ack(struct sock *sk, 151 const struct sk_buff *skb, u8 sent_ect) 152 { 153 u8 ace = tcp_accecn_ace(tcp_hdr(skb)); 154 struct tcp_sock *tp = tcp_sk(sk); 155 156 switch (ace) { 157 case 0x0: 158 /* Invalid value */ 159 tcp_accecn_fail_mode_set(tp, TCP_ACCECN_ACE_FAIL_RECV); 160 break; 161 case 0x7: 162 case 0x5: 163 case 0x1: 164 /* Unused but legal values */ 165 break; 166 default: 167 /* Validation only applies to first non-data packet */ 168 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq && 169 !TCP_SKB_CB(skb)->sacked && 170 tcp_accecn_validate_syn_feedback(sk, ace, sent_ect)) { 171 if ((tcp_accecn_extract_syn_ect(ace) == INET_ECN_CE) && 172 !tp->delivered_ce) 173 tp->delivered_ce++; 174 } 175 break; 176 } 177 } 178 179 /* Demand the minimum # to send AccECN optnio */ 180 static inline void tcp_accecn_opt_demand_min(struct sock *sk, 181 u8 opt_demand_min) 182 { 183 struct tcp_sock *tp = tcp_sk(sk); 184 u8 opt_demand; 185 186 opt_demand = max_t(u8, opt_demand_min, tp->accecn_opt_demand); 187 tp->accecn_opt_demand = opt_demand; 188 } 189 190 /* Maps IP ECN field ECT/CE code point to AccECN option field number, given 191 * we are sending fields with Accurate ECN Order 1: ECT(1), CE, ECT(0). 192 */ 193 static inline u8 tcp_ecnfield_to_accecn_optfield(u8 ecnfield) 194 { 195 switch (ecnfield & INET_ECN_MASK) { 196 case INET_ECN_NOT_ECT: 197 return 0; /* AccECN does not send counts of NOT_ECT */ 198 case INET_ECN_ECT_1: 199 return 1; 200 case INET_ECN_CE: 201 return 2; 202 case INET_ECN_ECT_0: 203 return 3; 204 } 205 return 0; 206 } 207 208 /* Maps IP ECN field ECT/CE code point to AccECN option field value offset. 209 * Some fields do not start from zero, to detect zeroing by middleboxes. 210 */ 211 static inline u32 tcp_accecn_field_init_offset(u8 ecnfield) 212 { 213 switch (ecnfield & INET_ECN_MASK) { 214 case INET_ECN_NOT_ECT: 215 return 0; /* AccECN does not send counts of NOT_ECT */ 216 case INET_ECN_ECT_1: 217 return TCP_ACCECN_E1B_INIT_OFFSET; 218 case INET_ECN_CE: 219 return TCP_ACCECN_CEB_INIT_OFFSET; 220 case INET_ECN_ECT_0: 221 return TCP_ACCECN_E0B_INIT_OFFSET; 222 } 223 return 0; 224 } 225 226 /* Maps AccECN option field #nr to IP ECN field ECT/CE bits */ 227 static inline unsigned int tcp_accecn_optfield_to_ecnfield(unsigned int option, 228 bool order) 229 { 230 /* Based on Table 5 of the AccECN spec to map (option, order) to 231 * the corresponding ECN conuters (ECT-1, ECT-0, or CE). 232 */ 233 static const u8 optfield_lookup[2][3] = { 234 /* order = 0: 1st field ECT-0, 2nd field CE, 3rd field ECT-1 */ 235 { INET_ECN_ECT_0, INET_ECN_CE, INET_ECN_ECT_1 }, 236 /* order = 1: 1st field ECT-1, 2nd field CE, 3rd field ECT-0 */ 237 { INET_ECN_ECT_1, INET_ECN_CE, INET_ECN_ECT_0 } 238 }; 239 240 return optfield_lookup[order][option % 3]; 241 } 242 243 /* Handles AccECN option ECT and CE 24-bit byte counters update into 244 * the u32 value in tcp_sock. As we're processing TCP options, it is 245 * safe to access from - 1. 246 */ 247 static inline s32 tcp_update_ecn_bytes(u32 *cnt, const char *from, 248 u32 init_offset) 249 { 250 u32 truncated = (get_unaligned_be32(from - 1) - init_offset) & 251 0xFFFFFFU; 252 u32 delta = (truncated - *cnt) & 0xFFFFFFU; 253 254 /* If delta has the highest bit set (24th bit) indicating 255 * negative, sign extend to correct an estimation using 256 * sign_extend32(delta, 24 - 1) 257 */ 258 delta = sign_extend32(delta, 23); 259 *cnt += delta; 260 return (s32)delta; 261 } 262 263 /* Updates Accurate ECN received counters from the received IP ECN field */ 264 static inline void tcp_ecn_received_counters(struct sock *sk, 265 const struct sk_buff *skb, u32 len) 266 { 267 u8 ecnfield = TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK; 268 u8 is_ce = INET_ECN_is_ce(ecnfield); 269 struct tcp_sock *tp = tcp_sk(sk); 270 bool ecn_edge; 271 272 if (!INET_ECN_is_not_ect(ecnfield)) { 273 u32 pcount = is_ce * max_t(u16, 1, skb_shinfo(skb)->gso_segs); 274 275 /* As for accurate ECN, the TCP_ECN_SEEN flag is set by 276 * tcp_ecn_received_counters() when the ECN codepoint of 277 * received TCP data or ACK contains ECT(0), ECT(1), or CE. 278 */ 279 if (!tcp_ecn_mode_rfc3168(tp)) 280 tp->ecn_flags |= TCP_ECN_SEEN; 281 282 /* ACE counter tracks *all* segments including pure ACKs */ 283 tp->received_ce += pcount; 284 tp->received_ce_pending = min(tp->received_ce_pending + pcount, 285 0xfU); 286 287 if (len > 0) { 288 u8 minlen = tcp_ecnfield_to_accecn_optfield(ecnfield); 289 u32 oldbytes = tp->received_ecn_bytes[ecnfield - 1]; 290 u32 bytes_mask = GENMASK_U32(31, 22); 291 292 tp->received_ecn_bytes[ecnfield - 1] += len; 293 tp->accecn_minlen = max_t(u8, tp->accecn_minlen, 294 minlen); 295 296 /* Send AccECN option at least once per 2^22-byte 297 * increase in any ECN byte counter. 298 */ 299 if ((tp->received_ecn_bytes[ecnfield - 1] ^ oldbytes) & 300 bytes_mask) { 301 tcp_accecn_opt_demand_min(sk, 1); 302 } 303 } 304 } 305 306 ecn_edge = tp->prev_ecnfield != ecnfield; 307 if (ecn_edge || is_ce) { 308 tp->prev_ecnfield = ecnfield; 309 /* Demand Accurate ECN change-triggered ACKs. Two ACK are 310 * demanded to indicate unambiguously the ecnfield value 311 * in the latter ACK. 312 */ 313 if (tcp_ecn_mode_accecn(tp)) { 314 if (ecn_edge) 315 inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW; 316 tp->accecn_opt_demand = 2; 317 } 318 } 319 } 320 321 /* AccECN specification, 2.2: [...] A Data Receiver maintains four counters 322 * initialized at the start of the half-connection. [...] These byte counters 323 * reflect only the TCP payload length, excluding TCP header and TCP options. 324 */ 325 static inline void tcp_ecn_received_counters_payload(struct sock *sk, 326 const struct sk_buff *skb) 327 { 328 const struct tcphdr *th = (const struct tcphdr *)skb->data; 329 330 tcp_ecn_received_counters(sk, skb, skb->len - th->doff * 4); 331 } 332 333 /* AccECN specification, 5.1: [...] a server can determine that it 334 * negotiated AccECN as [...] if the ACK contains an ACE field with 335 * the value 0b010 to 0b111 (decimal 2 to 7). 336 */ 337 static inline bool cookie_accecn_ok(const struct tcphdr *th) 338 { 339 return tcp_accecn_ace(th) > 0x1; 340 } 341 342 /* Used to form the ACE flags for SYN/ACK */ 343 static inline u16 tcp_accecn_reflector_flags(u8 ect) 344 { 345 /* TCP ACE flags of SYN/ACK are set based on IP-ECN received from SYN. 346 * Below is an excerpt from the 1st block of Table 2 of AccECN spec, 347 * in which TCP ACE flags are encoded as: (AE << 2) | (CWR << 1) | ECE 348 */ 349 static const u8 ecn_to_ace_flags[4] = { 350 0b010, /* Not-ECT is received */ 351 0b011, /* ECT(1) is received */ 352 0b100, /* ECT(0) is received */ 353 0b110 /* CE is received */ 354 }; 355 356 return FIELD_PREP(TCPHDR_ACE, ecn_to_ace_flags[ect & 0x3]); 357 } 358 359 /* AccECN specification, 3.1.2: If a TCP server that implements AccECN 360 * receives a SYN with the three TCP header flags (AE, CWR and ECE) set 361 * to any combination other than 000, 011 or 111, it MUST negotiate the 362 * use of AccECN as if they had been set to 111. 363 */ 364 static inline bool tcp_accecn_syn_requested(const struct tcphdr *th) 365 { 366 u8 ace = tcp_accecn_ace(th); 367 368 return ace && ace != 0x3; 369 } 370 371 static inline void __tcp_accecn_init_bytes_counters(int *counter_array) 372 { 373 BUILD_BUG_ON(INET_ECN_ECT_1 != 0x1); 374 BUILD_BUG_ON(INET_ECN_ECT_0 != 0x2); 375 BUILD_BUG_ON(INET_ECN_CE != 0x3); 376 377 counter_array[INET_ECN_ECT_1 - 1] = 0; 378 counter_array[INET_ECN_ECT_0 - 1] = 0; 379 counter_array[INET_ECN_CE - 1] = 0; 380 } 381 382 static inline void tcp_accecn_init_counters(struct tcp_sock *tp) 383 { 384 tp->received_ce = 0; 385 tp->received_ce_pending = 0; 386 __tcp_accecn_init_bytes_counters(tp->received_ecn_bytes); 387 __tcp_accecn_init_bytes_counters(tp->delivered_ecn_bytes); 388 tp->accecn_minlen = 0; 389 tp->accecn_opt_demand = 0; 390 tp->est_ecnfield = 0; 391 } 392 393 /* Used for make_synack to form the ACE flags */ 394 static inline void tcp_accecn_echo_syn_ect(struct tcphdr *th, u8 ect) 395 { 396 /* TCP ACE flags of SYN/ACK are set based on IP-ECN codepoint received 397 * from SYN. Below is an excerpt from Table 2 of the AccECN spec: 398 * +====================+====================================+ 399 * | IP-ECN codepoint | Respective ACE falgs on SYN/ACK | 400 * | received on SYN | AE CWR ECE | 401 * +====================+====================================+ 402 * | Not-ECT | 0 1 0 | 403 * | ECT(1) | 0 1 1 | 404 * | ECT(0) | 1 0 0 | 405 * | CE | 1 1 0 | 406 * +====================+====================================+ 407 */ 408 th->ae = !!(ect & INET_ECN_ECT_0); 409 th->cwr = ect != INET_ECN_ECT_0; 410 th->ece = ect == INET_ECN_ECT_1; 411 } 412 413 static inline void tcp_accecn_set_ace(struct tcp_sock *tp, struct sk_buff *skb, 414 struct tcphdr *th) 415 { 416 u32 wire_ace; 417 418 /* The final packet of the 3WHS or anything like it must reflect 419 * the SYN/ACK ECT instead of putting CEP into ACE field, such 420 * case show up in tcp_flags. 421 */ 422 if (likely(!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACE))) { 423 wire_ace = tp->received_ce + TCP_ACCECN_CEP_INIT_OFFSET; 424 th->ece = !!(wire_ace & 0x1); 425 th->cwr = !!(wire_ace & 0x2); 426 th->ae = !!(wire_ace & 0x4); 427 tp->received_ce_pending = 0; 428 } 429 } 430 431 /* See Table 2 of the AccECN draft */ 432 static inline void tcp_ecn_rcv_synack(struct sock *sk, const struct tcphdr *th, 433 u8 ip_dsfield) 434 { 435 struct tcp_sock *tp = tcp_sk(sk); 436 u8 ace = tcp_accecn_ace(th); 437 438 switch (ace) { 439 case 0x0: 440 case 0x7: 441 /* +========+========+============+=============+ 442 * | A | B | SYN/ACK | Feedback | 443 * | | | B->A | Mode of A | 444 * | | | AE CWR ECE | | 445 * +========+========+============+=============+ 446 * | AccECN | No ECN | 0 0 0 | Not ECN | 447 * | AccECN | Broken | 1 1 1 | Not ECN | 448 * +========+========+============+=============+ 449 */ 450 tcp_ecn_mode_set(tp, TCP_ECN_DISABLED); 451 break; 452 case 0x1: 453 case 0x5: 454 /* +========+========+============+=============+ 455 * | A | B | SYN/ACK | Feedback | 456 * | | | B->A | Mode of A | 457 * | | | AE CWR ECE | | 458 * +========+========+============+=============+ 459 * | AccECN | Nonce | 1 0 1 | (Reserved) | 460 * | AccECN | ECN | 0 0 1 | Classic ECN | 461 * | Nonce | AccECN | 0 0 1 | Classic ECN | 462 * | ECN | AccECN | 0 0 1 | Classic ECN | 463 * +========+========+============+=============+ 464 */ 465 if (tcp_ecn_mode_pending(tp)) 466 /* Downgrade from AccECN, or requested initially */ 467 tcp_ecn_mode_set(tp, TCP_ECN_MODE_RFC3168); 468 break; 469 default: 470 tcp_ecn_mode_set(tp, TCP_ECN_MODE_ACCECN); 471 tp->syn_ect_rcv = ip_dsfield & INET_ECN_MASK; 472 tp->accecn_opt_demand = 2; 473 if (INET_ECN_is_ce(ip_dsfield) && 474 tcp_accecn_validate_syn_feedback(sk, ace, 475 tp->syn_ect_snt)) { 476 tp->received_ce++; 477 tp->received_ce_pending++; 478 } 479 break; 480 } 481 } 482 483 static inline void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th, 484 const struct sk_buff *skb) 485 { 486 if (tcp_ecn_mode_pending(tp)) { 487 if (!tcp_accecn_syn_requested(th)) { 488 /* Downgrade to classic ECN feedback */ 489 tcp_ecn_mode_set(tp, TCP_ECN_MODE_RFC3168); 490 } else { 491 tp->syn_ect_rcv = TCP_SKB_CB(skb)->ip_dsfield & 492 INET_ECN_MASK; 493 tp->prev_ecnfield = tp->syn_ect_rcv; 494 tcp_ecn_mode_set(tp, TCP_ECN_MODE_ACCECN); 495 } 496 } 497 if (tcp_ecn_mode_rfc3168(tp) && (!th->ece || !th->cwr)) 498 tcp_ecn_mode_set(tp, TCP_ECN_DISABLED); 499 } 500 501 static inline bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, 502 const struct tcphdr *th) 503 { 504 if (th->ece && !th->syn && tcp_ecn_mode_rfc3168(tp)) 505 return true; 506 return false; 507 } 508 509 /* Packet ECN state for a SYN-ACK */ 510 static inline void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb) 511 { 512 struct tcp_sock *tp = tcp_sk(sk); 513 514 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR; 515 if (tcp_ecn_disabled(tp)) 516 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE; 517 else if (tcp_ca_needs_ecn(sk) || 518 tcp_bpf_ca_needs_ecn(sk)) 519 INET_ECN_xmit(sk); 520 521 if (tp->ecn_flags & TCP_ECN_MODE_ACCECN) { 522 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ACE; 523 TCP_SKB_CB(skb)->tcp_flags |= 524 tcp_accecn_reflector_flags(tp->syn_ect_rcv); 525 tp->syn_ect_snt = inet_sk(sk)->tos & INET_ECN_MASK; 526 } 527 } 528 529 /* Packet ECN state for a SYN. */ 530 static inline void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb) 531 { 532 struct tcp_sock *tp = tcp_sk(sk); 533 bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk); 534 bool use_ecn, use_accecn; 535 u8 tcp_ecn = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn); 536 537 use_accecn = tcp_ecn == TCP_ECN_IN_ACCECN_OUT_ACCECN; 538 use_ecn = tcp_ecn == TCP_ECN_IN_ECN_OUT_ECN || 539 tcp_ecn == TCP_ECN_IN_ACCECN_OUT_ECN || 540 tcp_ca_needs_ecn(sk) || bpf_needs_ecn || use_accecn; 541 542 if (!use_ecn) { 543 const struct dst_entry *dst = __sk_dst_get(sk); 544 545 if (dst && dst_feature(dst, RTAX_FEATURE_ECN)) 546 use_ecn = true; 547 } 548 549 tp->ecn_flags = 0; 550 551 if (use_ecn) { 552 if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn) 553 INET_ECN_xmit(sk); 554 555 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR; 556 if (use_accecn) { 557 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_AE; 558 tcp_ecn_mode_set(tp, TCP_ECN_MODE_PENDING); 559 tp->syn_ect_snt = inet_sk(sk)->tos & INET_ECN_MASK; 560 } else { 561 tcp_ecn_mode_set(tp, TCP_ECN_MODE_RFC3168); 562 } 563 } 564 } 565 566 static inline void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb) 567 { 568 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)) { 569 /* tp->ecn_flags are cleared at a later point in time when 570 * SYN ACK is ultimatively being received. 571 */ 572 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ACE; 573 } 574 } 575 576 static inline void 577 tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th) 578 { 579 if (tcp_rsk(req)->accecn_ok) 580 tcp_accecn_echo_syn_ect(th, tcp_rsk(req)->syn_ect_rcv); 581 else if (inet_rsk(req)->ecn_ok) 582 th->ece = 1; 583 } 584 585 static inline bool tcp_accecn_option_beacon_check(const struct sock *sk) 586 { 587 u32 ecn_beacon = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option_beacon); 588 const struct tcp_sock *tp = tcp_sk(sk); 589 590 if (!ecn_beacon) 591 return false; 592 593 return tcp_stamp_us_delta(tp->tcp_mstamp, tp->accecn_opt_tstamp) * ecn_beacon >= 594 (tp->srtt_us >> 3); 595 } 596 597 #endif /* _LINUX_TCP_ECN_H */ 598