xref: /openbmc/linux/net/mptcp/options.c (revision 3d2e1b82)
1 // SPDX-License-Identifier: GPL-2.0
2 /* Multipath TCP
3  *
4  * Copyright (c) 2017 - 2019, Intel Corporation.
5  */
6 
7 #define pr_fmt(fmt) "MPTCP: " fmt
8 
9 #include <linux/kernel.h>
10 #include <crypto/sha2.h>
11 #include <net/tcp.h>
12 #include <net/mptcp.h>
13 #include "protocol.h"
14 #include "mib.h"
15 
16 #include <trace/events/mptcp.h>
17 
mptcp_cap_flag_sha256(u8 flags)18 static bool mptcp_cap_flag_sha256(u8 flags)
19 {
20 	return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
21 }
22 
mptcp_parse_option(const struct sk_buff * skb,const unsigned char * ptr,int opsize,struct mptcp_options_received * mp_opt)23 static void mptcp_parse_option(const struct sk_buff *skb,
24 			       const unsigned char *ptr, int opsize,
25 			       struct mptcp_options_received *mp_opt)
26 {
27 	u8 subtype = *ptr >> 4;
28 	int expected_opsize;
29 	u16 subopt;
30 	u8 version;
31 	u8 flags;
32 	u8 i;
33 
34 	switch (subtype) {
35 	case MPTCPOPT_MP_CAPABLE:
36 		/* strict size checking */
37 		if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
38 			if (skb->len > tcp_hdr(skb)->doff << 2)
39 				expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
40 			else
41 				expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
42 			subopt = OPTION_MPTCP_MPC_ACK;
43 		} else {
44 			if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) {
45 				expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
46 				subopt = OPTION_MPTCP_MPC_SYNACK;
47 			} else {
48 				expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
49 				subopt = OPTION_MPTCP_MPC_SYN;
50 			}
51 		}
52 
53 		/* Cfr RFC 8684 Section 3.3.0:
54 		 * If a checksum is present but its use had
55 		 * not been negotiated in the MP_CAPABLE handshake, the receiver MUST
56 		 * close the subflow with a RST, as it is not behaving as negotiated.
57 		 * If a checksum is not present when its use has been negotiated, the
58 		 * receiver MUST close the subflow with a RST, as it is considered
59 		 * broken
60 		 * We parse even option with mismatching csum presence, so that
61 		 * later in subflow_data_ready we can trigger the reset.
62 		 */
63 		if (opsize != expected_opsize &&
64 		    (expected_opsize != TCPOLEN_MPTCP_MPC_ACK_DATA ||
65 		     opsize != TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM))
66 			break;
67 
68 		/* try to be gentle vs future versions on the initial syn */
69 		version = *ptr++ & MPTCP_VERSION_MASK;
70 		if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
71 			if (version != MPTCP_SUPPORTED_VERSION)
72 				break;
73 		} else if (version < MPTCP_SUPPORTED_VERSION) {
74 			break;
75 		}
76 
77 		flags = *ptr++;
78 		if (!mptcp_cap_flag_sha256(flags) ||
79 		    (flags & MPTCP_CAP_EXTENSIBILITY))
80 			break;
81 
82 		/* RFC 6824, Section 3.1:
83 		 * "For the Checksum Required bit (labeled "A"), if either
84 		 * host requires the use of checksums, checksums MUST be used.
85 		 * In other words, the only way for checksums not to be used
86 		 * is if both hosts in their SYNs set A=0."
87 		 */
88 		if (flags & MPTCP_CAP_CHECKSUM_REQD)
89 			mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
90 
91 		mp_opt->deny_join_id0 = !!(flags & MPTCP_CAP_DENY_JOIN_ID0);
92 
93 		mp_opt->suboptions |= subopt;
94 		if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
95 			mp_opt->sndr_key = get_unaligned_be64(ptr);
96 			ptr += 8;
97 		}
98 		if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
99 			mp_opt->rcvr_key = get_unaligned_be64(ptr);
100 			ptr += 8;
101 		}
102 		if (opsize >= TCPOLEN_MPTCP_MPC_ACK_DATA) {
103 			/* Section 3.1.:
104 			 * "the data parameters in a MP_CAPABLE are semantically
105 			 * equivalent to those in a DSS option and can be used
106 			 * interchangeably."
107 			 */
108 			mp_opt->suboptions |= OPTION_MPTCP_DSS;
109 			mp_opt->use_map = 1;
110 			mp_opt->mpc_map = 1;
111 			mp_opt->use_ack = 0;
112 			mp_opt->data_len = get_unaligned_be16(ptr);
113 			ptr += 2;
114 		}
115 		if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
116 			mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
117 			mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
118 			ptr += 2;
119 		}
120 		pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d csum=%u\n",
121 			 version, flags, opsize, mp_opt->sndr_key,
122 			 mp_opt->rcvr_key, mp_opt->data_len, mp_opt->csum);
123 		break;
124 
125 	case MPTCPOPT_MP_JOIN:
126 		if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
127 			mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYN;
128 			mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
129 			mp_opt->join_id = *ptr++;
130 			mp_opt->token = get_unaligned_be32(ptr);
131 			ptr += 4;
132 			mp_opt->nonce = get_unaligned_be32(ptr);
133 			ptr += 4;
134 			pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u\n",
135 				 mp_opt->backup, mp_opt->join_id,
136 				 mp_opt->token, mp_opt->nonce);
137 		} else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
138 			mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYNACK;
139 			mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
140 			mp_opt->join_id = *ptr++;
141 			mp_opt->thmac = get_unaligned_be64(ptr);
142 			ptr += 8;
143 			mp_opt->nonce = get_unaligned_be32(ptr);
144 			ptr += 4;
145 			pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u\n",
146 				 mp_opt->backup, mp_opt->join_id,
147 				 mp_opt->thmac, mp_opt->nonce);
148 		} else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
149 			mp_opt->suboptions |= OPTION_MPTCP_MPJ_ACK;
150 			ptr += 2;
151 			memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
152 			pr_debug("MP_JOIN hmac\n");
153 		}
154 		break;
155 
156 	case MPTCPOPT_DSS:
157 		pr_debug("DSS\n");
158 		ptr++;
159 
160 		/* we must clear 'mpc_map' be able to detect MP_CAPABLE
161 		 * map vs DSS map in mptcp_incoming_options(), and reconstruct
162 		 * map info accordingly
163 		 */
164 		mp_opt->mpc_map = 0;
165 		flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
166 		mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
167 		mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
168 		mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
169 		mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
170 		mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
171 
172 		pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d\n",
173 			 mp_opt->data_fin, mp_opt->dsn64,
174 			 mp_opt->use_map, mp_opt->ack64,
175 			 mp_opt->use_ack);
176 
177 		expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
178 
179 		if (mp_opt->use_ack) {
180 			if (mp_opt->ack64)
181 				expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
182 			else
183 				expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
184 		}
185 
186 		if (mp_opt->use_map) {
187 			if (mp_opt->dsn64)
188 				expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
189 			else
190 				expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
191 		}
192 
193 		/* Always parse any csum presence combination, we will enforce
194 		 * RFC 8684 Section 3.3.0 checks later in subflow_data_ready
195 		 */
196 		if (opsize != expected_opsize &&
197 		    opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
198 			break;
199 
200 		mp_opt->suboptions |= OPTION_MPTCP_DSS;
201 		if (mp_opt->use_ack) {
202 			if (mp_opt->ack64) {
203 				mp_opt->data_ack = get_unaligned_be64(ptr);
204 				ptr += 8;
205 			} else {
206 				mp_opt->data_ack = get_unaligned_be32(ptr);
207 				ptr += 4;
208 			}
209 
210 			pr_debug("data_ack=%llu\n", mp_opt->data_ack);
211 		}
212 
213 		if (mp_opt->use_map) {
214 			if (mp_opt->dsn64) {
215 				mp_opt->data_seq = get_unaligned_be64(ptr);
216 				ptr += 8;
217 			} else {
218 				mp_opt->data_seq = get_unaligned_be32(ptr);
219 				ptr += 4;
220 			}
221 
222 			mp_opt->subflow_seq = get_unaligned_be32(ptr);
223 			ptr += 4;
224 
225 			mp_opt->data_len = get_unaligned_be16(ptr);
226 			ptr += 2;
227 
228 			if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
229 				mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
230 				mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
231 				ptr += 2;
232 			}
233 
234 			pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u\n",
235 				 mp_opt->data_seq, mp_opt->subflow_seq,
236 				 mp_opt->data_len, !!(mp_opt->suboptions & OPTION_MPTCP_CSUMREQD),
237 				 mp_opt->csum);
238 		}
239 
240 		break;
241 
242 	case MPTCPOPT_ADD_ADDR:
243 		mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
244 		if (!mp_opt->echo) {
245 			if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
246 			    opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
247 				mp_opt->addr.family = AF_INET;
248 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
249 			else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
250 				 opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
251 				mp_opt->addr.family = AF_INET6;
252 #endif
253 			else
254 				break;
255 		} else {
256 			if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
257 			    opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
258 				mp_opt->addr.family = AF_INET;
259 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
260 			else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
261 				 opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
262 				mp_opt->addr.family = AF_INET6;
263 #endif
264 			else
265 				break;
266 		}
267 
268 		mp_opt->suboptions |= OPTION_MPTCP_ADD_ADDR;
269 		mp_opt->addr.id = *ptr++;
270 		mp_opt->addr.port = 0;
271 		mp_opt->ahmac = 0;
272 		if (mp_opt->addr.family == AF_INET) {
273 			memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4);
274 			ptr += 4;
275 			if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
276 			    opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
277 				mp_opt->addr.port = htons(get_unaligned_be16(ptr));
278 				ptr += 2;
279 			}
280 		}
281 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
282 		else {
283 			memcpy(mp_opt->addr.addr6.s6_addr, (u8 *)ptr, 16);
284 			ptr += 16;
285 			if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
286 			    opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
287 				mp_opt->addr.port = htons(get_unaligned_be16(ptr));
288 				ptr += 2;
289 			}
290 		}
291 #endif
292 		if (!mp_opt->echo) {
293 			mp_opt->ahmac = get_unaligned_be64(ptr);
294 			ptr += 8;
295 		}
296 		pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d\n",
297 			 (mp_opt->addr.family == AF_INET6) ? "6" : "",
298 			 mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port));
299 		break;
300 
301 	case MPTCPOPT_RM_ADDR:
302 		if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
303 		    opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
304 			break;
305 
306 		ptr++;
307 
308 		mp_opt->suboptions |= OPTION_MPTCP_RM_ADDR;
309 		mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
310 		for (i = 0; i < mp_opt->rm_list.nr; i++)
311 			mp_opt->rm_list.ids[i] = *ptr++;
312 		pr_debug("RM_ADDR: rm_list_nr=%d\n", mp_opt->rm_list.nr);
313 		break;
314 
315 	case MPTCPOPT_MP_PRIO:
316 		if (opsize != TCPOLEN_MPTCP_PRIO)
317 			break;
318 
319 		mp_opt->suboptions |= OPTION_MPTCP_PRIO;
320 		mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
321 		pr_debug("MP_PRIO: prio=%d\n", mp_opt->backup);
322 		break;
323 
324 	case MPTCPOPT_MP_FASTCLOSE:
325 		if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
326 			break;
327 
328 		ptr += 2;
329 		mp_opt->rcvr_key = get_unaligned_be64(ptr);
330 		ptr += 8;
331 		mp_opt->suboptions |= OPTION_MPTCP_FASTCLOSE;
332 		pr_debug("MP_FASTCLOSE: recv_key=%llu\n", mp_opt->rcvr_key);
333 		break;
334 
335 	case MPTCPOPT_RST:
336 		if (opsize != TCPOLEN_MPTCP_RST)
337 			break;
338 
339 		if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
340 			break;
341 
342 		mp_opt->suboptions |= OPTION_MPTCP_RST;
343 		flags = *ptr++;
344 		mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
345 		mp_opt->reset_reason = *ptr;
346 		pr_debug("MP_RST: transient=%u reason=%u\n",
347 			 mp_opt->reset_transient, mp_opt->reset_reason);
348 		break;
349 
350 	case MPTCPOPT_MP_FAIL:
351 		if (opsize != TCPOLEN_MPTCP_FAIL)
352 			break;
353 
354 		ptr += 2;
355 		mp_opt->suboptions |= OPTION_MPTCP_FAIL;
356 		mp_opt->fail_seq = get_unaligned_be64(ptr);
357 		pr_debug("MP_FAIL: data_seq=%llu\n", mp_opt->fail_seq);
358 		break;
359 
360 	default:
361 		break;
362 	}
363 }
364 
mptcp_get_options(const struct sk_buff * skb,struct mptcp_options_received * mp_opt)365 void mptcp_get_options(const struct sk_buff *skb,
366 		       struct mptcp_options_received *mp_opt)
367 {
368 	const struct tcphdr *th = tcp_hdr(skb);
369 	const unsigned char *ptr;
370 	int length;
371 
372 	/* initialize option status */
373 	mp_opt->suboptions = 0;
374 
375 	length = (th->doff * 4) - sizeof(struct tcphdr);
376 	ptr = (const unsigned char *)(th + 1);
377 
378 	while (length > 0) {
379 		int opcode = *ptr++;
380 		int opsize;
381 
382 		switch (opcode) {
383 		case TCPOPT_EOL:
384 			return;
385 		case TCPOPT_NOP:	/* Ref: RFC 793 section 3.1 */
386 			length--;
387 			continue;
388 		default:
389 			if (length < 2)
390 				return;
391 			opsize = *ptr++;
392 			if (opsize < 2) /* "silly options" */
393 				return;
394 			if (opsize > length)
395 				return;	/* don't parse partial options */
396 			if (opcode == TCPOPT_MPTCP)
397 				mptcp_parse_option(skb, ptr, opsize, mp_opt);
398 			ptr += opsize - 2;
399 			length -= opsize;
400 		}
401 	}
402 }
403 
mptcp_syn_options(struct sock * sk,const struct sk_buff * skb,unsigned int * size,struct mptcp_out_options * opts)404 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
405 		       unsigned int *size, struct mptcp_out_options *opts)
406 {
407 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
408 
409 	/* we will use snd_isn to detect first pkt [re]transmission
410 	 * in mptcp_established_options_mp()
411 	 */
412 	subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
413 	if (subflow->request_mptcp) {
414 		opts->suboptions = OPTION_MPTCP_MPC_SYN;
415 		opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
416 		opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
417 		*size = TCPOLEN_MPTCP_MPC_SYN;
418 		return true;
419 	} else if (subflow->request_join) {
420 		pr_debug("remote_token=%u, nonce=%u\n", subflow->remote_token,
421 			 subflow->local_nonce);
422 		opts->suboptions = OPTION_MPTCP_MPJ_SYN;
423 		opts->join_id = subflow->local_id;
424 		opts->token = subflow->remote_token;
425 		opts->nonce = subflow->local_nonce;
426 		opts->backup = subflow->request_bkup;
427 		*size = TCPOLEN_MPTCP_MPJ_SYN;
428 		return true;
429 	}
430 	return false;
431 }
432 
clear_3rdack_retransmission(struct sock * sk)433 static void clear_3rdack_retransmission(struct sock *sk)
434 {
435 	struct inet_connection_sock *icsk = inet_csk(sk);
436 
437 	sk_stop_timer(sk, &icsk->icsk_delack_timer);
438 	icsk->icsk_ack.timeout = 0;
439 	icsk->icsk_ack.ato = 0;
440 	icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
441 }
442 
mptcp_established_options_mp(struct sock * sk,struct sk_buff * skb,bool snd_data_fin_enable,unsigned int * size,struct mptcp_out_options * opts)443 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
444 					 bool snd_data_fin_enable,
445 					 unsigned int *size,
446 					 struct mptcp_out_options *opts)
447 {
448 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
449 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
450 	struct mptcp_ext *mpext;
451 	unsigned int data_len;
452 	u8 len;
453 
454 	/* When skb is not available, we better over-estimate the emitted
455 	 * options len. A full DSS option (28 bytes) is longer than
456 	 * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
457 	 * tell the caller to defer the estimate to
458 	 * mptcp_established_options_dss(), which will reserve enough space.
459 	 */
460 	if (!skb)
461 		return false;
462 
463 	/* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
464 	if (subflow->fully_established || snd_data_fin_enable ||
465 	    subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
466 	    sk->sk_state != TCP_ESTABLISHED)
467 		return false;
468 
469 	if (subflow->mp_capable) {
470 		mpext = mptcp_get_ext(skb);
471 		data_len = mpext ? mpext->data_len : 0;
472 
473 		/* we will check ops->data_len in mptcp_write_options() to
474 		 * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
475 		 * TCPOLEN_MPTCP_MPC_ACK
476 		 */
477 		opts->data_len = data_len;
478 		opts->suboptions = OPTION_MPTCP_MPC_ACK;
479 		opts->sndr_key = subflow->local_key;
480 		opts->rcvr_key = subflow->remote_key;
481 		opts->csum_reqd = READ_ONCE(msk->csum_enabled);
482 		opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
483 
484 		/* Section 3.1.
485 		 * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
486 		 * packets that start the first subflow of an MPTCP connection,
487 		 * as well as the first packet that carries data
488 		 */
489 		if (data_len > 0) {
490 			len = TCPOLEN_MPTCP_MPC_ACK_DATA;
491 			if (opts->csum_reqd) {
492 				/* we need to propagate more info to csum the pseudo hdr */
493 				opts->data_seq = mpext->data_seq;
494 				opts->subflow_seq = mpext->subflow_seq;
495 				opts->csum = mpext->csum;
496 				len += TCPOLEN_MPTCP_DSS_CHECKSUM;
497 			}
498 			*size = ALIGN(len, 4);
499 		} else {
500 			*size = TCPOLEN_MPTCP_MPC_ACK;
501 		}
502 
503 		pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d\n",
504 			 subflow, subflow->local_key, subflow->remote_key,
505 			 data_len);
506 
507 		return true;
508 	} else if (subflow->mp_join) {
509 		opts->suboptions = OPTION_MPTCP_MPJ_ACK;
510 		memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
511 		*size = TCPOLEN_MPTCP_MPJ_ACK;
512 		pr_debug("subflow=%p\n", subflow);
513 
514 		/* we can use the full delegate action helper only from BH context
515 		 * If we are in process context - sk is flushing the backlog at
516 		 * socket lock release time - just set the appropriate flag, will
517 		 * be handled by the release callback
518 		 */
519 		if (sock_owned_by_user(sk))
520 			set_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status);
521 		else
522 			mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_ACK);
523 		return true;
524 	}
525 	return false;
526 }
527 
mptcp_write_data_fin(struct mptcp_subflow_context * subflow,struct sk_buff * skb,struct mptcp_ext * ext)528 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
529 				 struct sk_buff *skb, struct mptcp_ext *ext)
530 {
531 	/* The write_seq value has already been incremented, so the actual
532 	 * sequence number for the DATA_FIN is one less.
533 	 */
534 	u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
535 
536 	if (!ext->use_map || !skb->len) {
537 		/* RFC6824 requires a DSS mapping with specific values
538 		 * if DATA_FIN is set but no data payload is mapped
539 		 */
540 		ext->data_fin = 1;
541 		ext->use_map = 1;
542 		ext->dsn64 = 1;
543 		ext->data_seq = data_fin_tx_seq;
544 		ext->subflow_seq = 0;
545 		ext->data_len = 1;
546 	} else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
547 		/* If there's an existing DSS mapping and it is the
548 		 * final mapping, DATA_FIN consumes 1 additional byte of
549 		 * mapping space.
550 		 */
551 		ext->data_fin = 1;
552 		ext->data_len++;
553 	}
554 }
555 
mptcp_established_options_dss(struct sock * sk,struct sk_buff * skb,bool snd_data_fin_enable,unsigned int * size,struct mptcp_out_options * opts)556 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
557 					  bool snd_data_fin_enable,
558 					  unsigned int *size,
559 					  struct mptcp_out_options *opts)
560 {
561 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
562 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
563 	unsigned int dss_size = 0;
564 	struct mptcp_ext *mpext;
565 	unsigned int ack_size;
566 	bool ret = false;
567 	u64 ack_seq;
568 
569 	opts->csum_reqd = READ_ONCE(msk->csum_enabled);
570 	mpext = skb ? mptcp_get_ext(skb) : NULL;
571 
572 	if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
573 		unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
574 
575 		if (mpext) {
576 			if (opts->csum_reqd)
577 				map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;
578 
579 			opts->ext_copy = *mpext;
580 		}
581 
582 		dss_size = map_size;
583 		if (skb && snd_data_fin_enable)
584 			mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
585 		opts->suboptions = OPTION_MPTCP_DSS;
586 		ret = true;
587 	}
588 
589 	/* passive sockets msk will set the 'can_ack' after accept(), even
590 	 * if the first subflow may have the already the remote key handy
591 	 */
592 	opts->ext_copy.use_ack = 0;
593 	if (!READ_ONCE(msk->can_ack)) {
594 		*size = ALIGN(dss_size, 4);
595 		return ret;
596 	}
597 
598 	ack_seq = READ_ONCE(msk->ack_seq);
599 	if (READ_ONCE(msk->use_64bit_ack)) {
600 		ack_size = TCPOLEN_MPTCP_DSS_ACK64;
601 		opts->ext_copy.data_ack = ack_seq;
602 		opts->ext_copy.ack64 = 1;
603 	} else {
604 		ack_size = TCPOLEN_MPTCP_DSS_ACK32;
605 		opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
606 		opts->ext_copy.ack64 = 0;
607 	}
608 	opts->ext_copy.use_ack = 1;
609 	opts->suboptions = OPTION_MPTCP_DSS;
610 	WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
611 
612 	/* Add kind/length/subtype/flag overhead if mapping is not populated */
613 	if (dss_size == 0)
614 		ack_size += TCPOLEN_MPTCP_DSS_BASE;
615 
616 	dss_size += ack_size;
617 
618 	*size = ALIGN(dss_size, 4);
619 	return true;
620 }
621 
add_addr_generate_hmac(u64 key1,u64 key2,struct mptcp_addr_info * addr)622 static u64 add_addr_generate_hmac(u64 key1, u64 key2,
623 				  struct mptcp_addr_info *addr)
624 {
625 	u16 port = ntohs(addr->port);
626 	u8 hmac[SHA256_DIGEST_SIZE];
627 	u8 msg[19];
628 	int i = 0;
629 
630 	msg[i++] = addr->id;
631 	if (addr->family == AF_INET) {
632 		memcpy(&msg[i], &addr->addr.s_addr, 4);
633 		i += 4;
634 	}
635 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
636 	else if (addr->family == AF_INET6) {
637 		memcpy(&msg[i], &addr->addr6.s6_addr, 16);
638 		i += 16;
639 	}
640 #endif
641 	msg[i++] = port >> 8;
642 	msg[i++] = port & 0xFF;
643 
644 	mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
645 
646 	return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
647 }
648 
mptcp_established_options_add_addr(struct sock * sk,struct sk_buff * skb,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)649 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
650 					       unsigned int *size,
651 					       unsigned int remaining,
652 					       struct mptcp_out_options *opts)
653 {
654 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
655 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
656 	bool drop_other_suboptions = false;
657 	unsigned int opt_size = *size;
658 	bool echo;
659 	int len;
660 
661 	/* add addr will strip the existing options, be sure to avoid breaking
662 	 * MPC/MPJ handshakes
663 	 */
664 	if (!mptcp_pm_should_add_signal(msk) ||
665 	    (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
666 	    !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &opts->addr,
667 		    &echo, &drop_other_suboptions))
668 		return false;
669 
670 	if (drop_other_suboptions)
671 		remaining += opt_size;
672 	len = mptcp_add_addr_len(opts->addr.family, echo, !!opts->addr.port);
673 	if (remaining < len)
674 		return false;
675 
676 	*size = len;
677 	if (drop_other_suboptions) {
678 		pr_debug("drop other suboptions\n");
679 		opts->suboptions = 0;
680 
681 		/* note that e.g. DSS could have written into the memory
682 		 * aliased by ahmac, we must reset the field here
683 		 * to avoid appending the hmac even for ADD_ADDR echo
684 		 * options
685 		 */
686 		opts->ahmac = 0;
687 		*size -= opt_size;
688 	}
689 	opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
690 	if (!echo) {
691 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDRTX);
692 		opts->ahmac = add_addr_generate_hmac(msk->local_key,
693 						     msk->remote_key,
694 						     &opts->addr);
695 	} else {
696 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADDTX);
697 	}
698 	pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d\n",
699 		 opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port));
700 
701 	return true;
702 }
703 
mptcp_established_options_rm_addr(struct sock * sk,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)704 static bool mptcp_established_options_rm_addr(struct sock *sk,
705 					      unsigned int *size,
706 					      unsigned int remaining,
707 					      struct mptcp_out_options *opts)
708 {
709 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
710 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
711 	struct mptcp_rm_list rm_list;
712 	int i, len;
713 
714 	if (!mptcp_pm_should_rm_signal(msk) ||
715 	    !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list)))
716 		return false;
717 
718 	len = mptcp_rm_addr_len(&rm_list);
719 	if (len < 0)
720 		return false;
721 	if (remaining < len)
722 		return false;
723 
724 	*size = len;
725 	opts->suboptions |= OPTION_MPTCP_RM_ADDR;
726 	opts->rm_list = rm_list;
727 
728 	for (i = 0; i < opts->rm_list.nr; i++)
729 		pr_debug("rm_list_ids[%d]=%d\n", i, opts->rm_list.ids[i]);
730 	MPTCP_ADD_STATS(sock_net(sk), MPTCP_MIB_RMADDRTX, opts->rm_list.nr);
731 	return true;
732 }
733 
mptcp_established_options_mp_prio(struct sock * sk,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)734 static bool mptcp_established_options_mp_prio(struct sock *sk,
735 					      unsigned int *size,
736 					      unsigned int remaining,
737 					      struct mptcp_out_options *opts)
738 {
739 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
740 
741 	/* can't send MP_PRIO with MPC, as they share the same option space:
742 	 * 'backup'. Also it makes no sense at all
743 	 */
744 	if (!subflow->send_mp_prio || (opts->suboptions & OPTIONS_MPTCP_MPC))
745 		return false;
746 
747 	/* account for the trailing 'nop' option */
748 	if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
749 		return false;
750 
751 	*size = TCPOLEN_MPTCP_PRIO_ALIGN;
752 	opts->suboptions |= OPTION_MPTCP_PRIO;
753 	opts->backup = subflow->request_bkup;
754 
755 	pr_debug("prio=%d\n", opts->backup);
756 
757 	return true;
758 }
759 
mptcp_established_options_rst(struct sock * sk,struct sk_buff * skb,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)760 static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
761 						   unsigned int *size,
762 						   unsigned int remaining,
763 						   struct mptcp_out_options *opts)
764 {
765 	const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
766 
767 	if (remaining < TCPOLEN_MPTCP_RST)
768 		return false;
769 
770 	*size = TCPOLEN_MPTCP_RST;
771 	opts->suboptions |= OPTION_MPTCP_RST;
772 	opts->reset_transient = subflow->reset_transient;
773 	opts->reset_reason = subflow->reset_reason;
774 	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTTX);
775 
776 	return true;
777 }
778 
mptcp_established_options_fastclose(struct sock * sk,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)779 static bool mptcp_established_options_fastclose(struct sock *sk,
780 						unsigned int *size,
781 						unsigned int remaining,
782 						struct mptcp_out_options *opts)
783 {
784 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
785 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
786 
787 	if (likely(!subflow->send_fastclose))
788 		return false;
789 
790 	if (remaining < TCPOLEN_MPTCP_FASTCLOSE)
791 		return false;
792 
793 	*size = TCPOLEN_MPTCP_FASTCLOSE;
794 	opts->suboptions |= OPTION_MPTCP_FASTCLOSE;
795 	opts->rcvr_key = msk->remote_key;
796 
797 	pr_debug("FASTCLOSE key=%llu\n", opts->rcvr_key);
798 	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSETX);
799 	return true;
800 }
801 
mptcp_established_options_mp_fail(struct sock * sk,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)802 static bool mptcp_established_options_mp_fail(struct sock *sk,
803 					      unsigned int *size,
804 					      unsigned int remaining,
805 					      struct mptcp_out_options *opts)
806 {
807 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
808 
809 	if (likely(!subflow->send_mp_fail))
810 		return false;
811 
812 	if (remaining < TCPOLEN_MPTCP_FAIL)
813 		return false;
814 
815 	*size = TCPOLEN_MPTCP_FAIL;
816 	opts->suboptions |= OPTION_MPTCP_FAIL;
817 	opts->fail_seq = subflow->map_seq;
818 
819 	pr_debug("MP_FAIL fail_seq=%llu\n", opts->fail_seq);
820 	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILTX);
821 
822 	return true;
823 }
824 
mptcp_established_options(struct sock * sk,struct sk_buff * skb,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)825 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
826 			       unsigned int *size, unsigned int remaining,
827 			       struct mptcp_out_options *opts)
828 {
829 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
830 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
831 	unsigned int opt_size = 0;
832 	bool snd_data_fin;
833 	bool ret = false;
834 
835 	opts->suboptions = 0;
836 
837 	if (unlikely(__mptcp_check_fallback(msk) && !mptcp_check_infinite_map(skb)))
838 		return false;
839 
840 	if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
841 		if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) ||
842 		    mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
843 			*size += opt_size;
844 			remaining -= opt_size;
845 		}
846 		/* MP_RST can be used with MP_FASTCLOSE and MP_FAIL if there is room */
847 		if (mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) {
848 			*size += opt_size;
849 			remaining -= opt_size;
850 		}
851 		return true;
852 	}
853 
854 	snd_data_fin = mptcp_data_fin_enabled(msk);
855 	if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, opts))
856 		ret = true;
857 	else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, opts)) {
858 		unsigned int mp_fail_size;
859 
860 		ret = true;
861 		if (mptcp_established_options_mp_fail(sk, &mp_fail_size,
862 						      remaining - opt_size, opts)) {
863 			*size += opt_size + mp_fail_size;
864 			remaining -= opt_size - mp_fail_size;
865 			return true;
866 		}
867 	}
868 
869 	/* we reserved enough space for the above options, and exceeding the
870 	 * TCP option space would be fatal
871 	 */
872 	if (WARN_ON_ONCE(opt_size > remaining))
873 		return false;
874 
875 	*size += opt_size;
876 	remaining -= opt_size;
877 	if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
878 		*size += opt_size;
879 		remaining -= opt_size;
880 		ret = true;
881 	} else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
882 		*size += opt_size;
883 		remaining -= opt_size;
884 		ret = true;
885 	}
886 
887 	if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
888 		*size += opt_size;
889 		remaining -= opt_size;
890 		ret = true;
891 	}
892 
893 	return ret;
894 }
895 
mptcp_synack_options(const struct request_sock * req,unsigned int * size,struct mptcp_out_options * opts)896 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
897 			  struct mptcp_out_options *opts)
898 {
899 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
900 
901 	if (subflow_req->mp_capable) {
902 		opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
903 		opts->sndr_key = subflow_req->local_key;
904 		opts->csum_reqd = subflow_req->csum_reqd;
905 		opts->allow_join_id0 = subflow_req->allow_join_id0;
906 		*size = TCPOLEN_MPTCP_MPC_SYNACK;
907 		pr_debug("subflow_req=%p, local_key=%llu\n",
908 			 subflow_req, subflow_req->local_key);
909 		return true;
910 	} else if (subflow_req->mp_join) {
911 		opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
912 		opts->backup = subflow_req->request_bkup;
913 		opts->join_id = subflow_req->local_id;
914 		opts->thmac = subflow_req->thmac;
915 		opts->nonce = subflow_req->local_nonce;
916 		pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u\n",
917 			 subflow_req, opts->backup, opts->join_id,
918 			 opts->thmac, opts->nonce);
919 		*size = TCPOLEN_MPTCP_MPJ_SYNACK;
920 		return true;
921 	}
922 	return false;
923 }
924 
check_fully_established(struct mptcp_sock * msk,struct sock * ssk,struct mptcp_subflow_context * subflow,struct sk_buff * skb,struct mptcp_options_received * mp_opt)925 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
926 				    struct mptcp_subflow_context *subflow,
927 				    struct sk_buff *skb,
928 				    struct mptcp_options_received *mp_opt)
929 {
930 	/* here we can process OoO, in-window pkts, only in-sequence 4th ack
931 	 * will make the subflow fully established
932 	 */
933 	if (likely(subflow->fully_established)) {
934 		/* on passive sockets, check for 3rd ack retransmission
935 		 * note that msk is always set by subflow_syn_recv_sock()
936 		 * for mp_join subflows
937 		 */
938 		if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
939 		    TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
940 		    subflow->mp_join && (mp_opt->suboptions & OPTIONS_MPTCP_MPJ) &&
941 		    !subflow->request_join)
942 			tcp_send_ack(ssk);
943 		goto check_notify;
944 	}
945 
946 	/* we must process OoO packets before the first subflow is fully
947 	 * established. OoO packets are instead a protocol violation
948 	 * for MP_JOIN subflows as the peer must not send any data
949 	 * before receiving the forth ack - cfr. RFC 8684 section 3.2.
950 	 */
951 	if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
952 		if (subflow->mp_join)
953 			goto reset;
954 		if (subflow->is_mptfo && mp_opt->suboptions & OPTION_MPTCP_MPC_ACK)
955 			goto set_fully_established;
956 		return subflow->mp_capable;
957 	}
958 
959 	if (subflow->remote_key_valid &&
960 	    (((mp_opt->suboptions & OPTION_MPTCP_DSS) && mp_opt->use_ack) ||
961 	     ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) &&
962 	      (!mp_opt->echo || subflow->mp_join)))) {
963 		/* subflows are fully established as soon as we get any
964 		 * additional ack, including ADD_ADDR.
965 		 */
966 		goto set_fully_established;
967 	}
968 
969 	/* If the first established packet does not contain MP_CAPABLE + data
970 	 * then fallback to TCP. Fallback scenarios requires a reset for
971 	 * MP_JOIN subflows.
972 	 */
973 	if (!(mp_opt->suboptions & OPTIONS_MPTCP_MPC)) {
974 		if (subflow->mp_join)
975 			goto reset;
976 		subflow->mp_capable = 0;
977 		pr_fallback(msk);
978 		mptcp_do_fallback(ssk);
979 		return false;
980 	}
981 
982 	if (mp_opt->deny_join_id0)
983 		WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
984 
985 	if (unlikely(!READ_ONCE(msk->pm.server_side)))
986 		pr_warn_once("bogus mpc option on established client sk");
987 
988 set_fully_established:
989 	mptcp_data_lock((struct sock *)msk);
990 	__mptcp_subflow_fully_established(msk, subflow, mp_opt);
991 	mptcp_data_unlock((struct sock *)msk);
992 
993 check_notify:
994 	/* if the subflow is not already linked into the conn_list, we can't
995 	 * notify the PM: this subflow is still on the listener queue
996 	 * and the PM possibly acquiring the subflow lock could race with
997 	 * the listener close
998 	 */
999 	if (likely(subflow->pm_notified) || list_empty(&subflow->node))
1000 		return true;
1001 
1002 	subflow->pm_notified = 1;
1003 	if (subflow->mp_join) {
1004 		clear_3rdack_retransmission(ssk);
1005 		mptcp_pm_subflow_established(msk);
1006 	} else {
1007 		mptcp_pm_fully_established(msk, ssk);
1008 	}
1009 	return true;
1010 
1011 reset:
1012 	mptcp_subflow_reset(ssk);
1013 	return false;
1014 }
1015 
__mptcp_expand_seq(u64 old_seq,u64 cur_seq)1016 u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
1017 {
1018 	u32 old_seq32, cur_seq32;
1019 
1020 	old_seq32 = (u32)old_seq;
1021 	cur_seq32 = (u32)cur_seq;
1022 	cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
1023 	if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
1024 		return cur_seq + (1LL << 32);
1025 
1026 	/* reverse wrap could happen, too */
1027 	if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
1028 		return cur_seq - (1LL << 32);
1029 	return cur_seq;
1030 }
1031 
__mptcp_snd_una_update(struct mptcp_sock * msk,u64 new_snd_una)1032 static void __mptcp_snd_una_update(struct mptcp_sock *msk, u64 new_snd_una)
1033 {
1034 	msk->bytes_acked += new_snd_una - msk->snd_una;
1035 	msk->snd_una = new_snd_una;
1036 }
1037 
ack_update_msk(struct mptcp_sock * msk,struct sock * ssk,struct mptcp_options_received * mp_opt)1038 static void ack_update_msk(struct mptcp_sock *msk,
1039 			   struct sock *ssk,
1040 			   struct mptcp_options_received *mp_opt)
1041 {
1042 	u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
1043 	struct sock *sk = (struct sock *)msk;
1044 	u64 old_snd_una;
1045 
1046 	mptcp_data_lock(sk);
1047 
1048 	/* avoid ack expansion on update conflict, to reduce the risk of
1049 	 * wrongly expanding to a future ack sequence number, which is way
1050 	 * more dangerous than missing an ack
1051 	 */
1052 	old_snd_una = msk->snd_una;
1053 	new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
1054 
1055 	/* ACK for data not even sent yet? Ignore.*/
1056 	if (unlikely(after64(new_snd_una, snd_nxt)))
1057 		new_snd_una = old_snd_una;
1058 
1059 	new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
1060 
1061 	if (after64(new_wnd_end, msk->wnd_end))
1062 		msk->wnd_end = new_wnd_end;
1063 
1064 	/* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
1065 	if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
1066 		__mptcp_check_push(sk, ssk);
1067 
1068 	if (after64(new_snd_una, old_snd_una)) {
1069 		__mptcp_snd_una_update(msk, new_snd_una);
1070 		__mptcp_data_acked(sk);
1071 	}
1072 	mptcp_data_unlock(sk);
1073 
1074 	trace_ack_update_msk(mp_opt->data_ack,
1075 			     old_snd_una, new_snd_una,
1076 			     new_wnd_end, msk->wnd_end);
1077 }
1078 
mptcp_update_rcv_data_fin(struct mptcp_sock * msk,u64 data_fin_seq,bool use_64bit)1079 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
1080 {
1081 	/* Skip if DATA_FIN was already received.
1082 	 * If updating simultaneously with the recvmsg loop, values
1083 	 * should match. If they mismatch, the peer is misbehaving and
1084 	 * we will prefer the most recent information.
1085 	 */
1086 	if (READ_ONCE(msk->rcv_data_fin))
1087 		return false;
1088 
1089 	WRITE_ONCE(msk->rcv_data_fin_seq,
1090 		   mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
1091 	WRITE_ONCE(msk->rcv_data_fin, 1);
1092 
1093 	return true;
1094 }
1095 
add_addr_hmac_valid(struct mptcp_sock * msk,struct mptcp_options_received * mp_opt)1096 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
1097 				struct mptcp_options_received *mp_opt)
1098 {
1099 	u64 hmac = 0;
1100 
1101 	if (mp_opt->echo)
1102 		return true;
1103 
1104 	hmac = add_addr_generate_hmac(msk->remote_key,
1105 				      msk->local_key,
1106 				      &mp_opt->addr);
1107 
1108 	pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
1109 		 msk, hmac, mp_opt->ahmac);
1110 
1111 	return hmac == mp_opt->ahmac;
1112 }
1113 
1114 /* Return false if a subflow has been reset, else return true */
mptcp_incoming_options(struct sock * sk,struct sk_buff * skb)1115 bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
1116 {
1117 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1118 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1119 	struct mptcp_options_received mp_opt;
1120 	struct mptcp_ext *mpext;
1121 
1122 	if (__mptcp_check_fallback(msk)) {
1123 		/* Keep it simple and unconditionally trigger send data cleanup and
1124 		 * pending queue spooling. We will need to acquire the data lock
1125 		 * for more accurate checks, and once the lock is acquired, such
1126 		 * helpers are cheap.
1127 		 */
1128 		mptcp_data_lock(subflow->conn);
1129 		if (sk_stream_memory_free(sk))
1130 			__mptcp_check_push(subflow->conn, sk);
1131 
1132 		/* on fallback we just need to ignore the msk-level snd_una, as
1133 		 * this is really plain TCP
1134 		 */
1135 		__mptcp_snd_una_update(msk, READ_ONCE(msk->snd_nxt));
1136 
1137 		__mptcp_data_acked(subflow->conn);
1138 		mptcp_data_unlock(subflow->conn);
1139 		return true;
1140 	}
1141 
1142 	mptcp_get_options(skb, &mp_opt);
1143 
1144 	/* The subflow can be in close state only if check_fully_established()
1145 	 * just sent a reset. If so, tell the caller to ignore the current packet.
1146 	 */
1147 	if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1148 		return sk->sk_state != TCP_CLOSE;
1149 
1150 	if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
1151 		if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
1152 		    msk->local_key == mp_opt.rcvr_key) {
1153 			WRITE_ONCE(msk->rcv_fastclose, true);
1154 			mptcp_schedule_work((struct sock *)msk);
1155 			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSERX);
1156 		}
1157 
1158 		if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) &&
1159 		    add_addr_hmac_valid(msk, &mp_opt)) {
1160 			if (!mp_opt.echo) {
1161 				mptcp_pm_add_addr_received(sk, &mp_opt.addr);
1162 				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1163 			} else {
1164 				mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1165 				mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
1166 				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1167 			}
1168 
1169 			if (mp_opt.addr.port)
1170 				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1171 		}
1172 
1173 		if (mp_opt.suboptions & OPTION_MPTCP_RM_ADDR)
1174 			mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1175 
1176 		if (mp_opt.suboptions & OPTION_MPTCP_PRIO) {
1177 			mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1178 			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1179 		}
1180 
1181 		if (mp_opt.suboptions & OPTION_MPTCP_FAIL) {
1182 			mptcp_pm_mp_fail_received(sk, mp_opt.fail_seq);
1183 			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILRX);
1184 		}
1185 
1186 		if (mp_opt.suboptions & OPTION_MPTCP_RST) {
1187 			subflow->reset_seen = 1;
1188 			subflow->reset_reason = mp_opt.reset_reason;
1189 			subflow->reset_transient = mp_opt.reset_transient;
1190 			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTRX);
1191 		}
1192 
1193 		if (!(mp_opt.suboptions & OPTION_MPTCP_DSS))
1194 			return true;
1195 	}
1196 
1197 	/* we can't wait for recvmsg() to update the ack_seq, otherwise
1198 	 * monodirectional flows will stuck
1199 	 */
1200 	if (mp_opt.use_ack)
1201 		ack_update_msk(msk, sk, &mp_opt);
1202 
1203 	/* Zero-data-length packets are dropped by the caller and not
1204 	 * propagated to the MPTCP layer, so the skb extension does not
1205 	 * need to be allocated or populated. DATA_FIN information, if
1206 	 * present, needs to be updated here before the skb is freed.
1207 	 */
1208 	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1209 		if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1210 		    mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64))
1211 			mptcp_schedule_work((struct sock *)msk);
1212 
1213 		return true;
1214 	}
1215 
1216 	mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1217 	if (!mpext)
1218 		return true;
1219 
1220 	memset(mpext, 0, sizeof(*mpext));
1221 
1222 	if (likely(mp_opt.use_map)) {
1223 		if (mp_opt.mpc_map) {
1224 			/* this is an MP_CAPABLE carrying MPTCP data
1225 			 * we know this map the first chunk of data
1226 			 */
1227 			mptcp_crypto_key_sha(subflow->remote_key, NULL,
1228 					     &mpext->data_seq);
1229 			mpext->data_seq++;
1230 			mpext->subflow_seq = 1;
1231 			mpext->dsn64 = 1;
1232 			mpext->mpc_map = 1;
1233 			mpext->data_fin = 0;
1234 		} else {
1235 			mpext->data_seq = mp_opt.data_seq;
1236 			mpext->subflow_seq = mp_opt.subflow_seq;
1237 			mpext->dsn64 = mp_opt.dsn64;
1238 			mpext->data_fin = mp_opt.data_fin;
1239 		}
1240 		mpext->data_len = mp_opt.data_len;
1241 		mpext->use_map = 1;
1242 		mpext->csum_reqd = !!(mp_opt.suboptions & OPTION_MPTCP_CSUMREQD);
1243 
1244 		if (mpext->csum_reqd)
1245 			mpext->csum = mp_opt.csum;
1246 	}
1247 
1248 	return true;
1249 }
1250 
mptcp_set_rwin(struct tcp_sock * tp,struct tcphdr * th)1251 static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
1252 {
1253 	const struct sock *ssk = (const struct sock *)tp;
1254 	struct mptcp_subflow_context *subflow;
1255 	u64 ack_seq, rcv_wnd_old, rcv_wnd_new;
1256 	struct mptcp_sock *msk;
1257 	u32 new_win;
1258 	u64 win;
1259 
1260 	subflow = mptcp_subflow_ctx(ssk);
1261 	msk = mptcp_sk(subflow->conn);
1262 
1263 	ack_seq = READ_ONCE(msk->ack_seq);
1264 	rcv_wnd_new = ack_seq + tp->rcv_wnd;
1265 
1266 	rcv_wnd_old = atomic64_read(&msk->rcv_wnd_sent);
1267 	if (after64(rcv_wnd_new, rcv_wnd_old)) {
1268 		u64 rcv_wnd;
1269 
1270 		for (;;) {
1271 			rcv_wnd = atomic64_cmpxchg(&msk->rcv_wnd_sent, rcv_wnd_old, rcv_wnd_new);
1272 
1273 			if (rcv_wnd == rcv_wnd_old)
1274 				break;
1275 
1276 			rcv_wnd_old = rcv_wnd;
1277 			if (before64(rcv_wnd_new, rcv_wnd_old)) {
1278 				MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE);
1279 				goto raise_win;
1280 			}
1281 			MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT);
1282 		}
1283 		return;
1284 	}
1285 
1286 	if (rcv_wnd_new != rcv_wnd_old) {
1287 raise_win:
1288 		win = rcv_wnd_old - ack_seq;
1289 		tp->rcv_wnd = min_t(u64, win, U32_MAX);
1290 		new_win = tp->rcv_wnd;
1291 
1292 		/* Make sure we do not exceed the maximum possible
1293 		 * scaled window.
1294 		 */
1295 		if (unlikely(th->syn))
1296 			new_win = min(new_win, 65535U) << tp->rx_opt.rcv_wscale;
1297 		if (!tp->rx_opt.rcv_wscale &&
1298 		    READ_ONCE(sock_net(ssk)->ipv4.sysctl_tcp_workaround_signed_windows))
1299 			new_win = min(new_win, MAX_TCP_WINDOW);
1300 		else
1301 			new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
1302 
1303 		/* RFC1323 scaling applied */
1304 		new_win >>= tp->rx_opt.rcv_wscale;
1305 		th->window = htons(new_win);
1306 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDSHARED);
1307 	}
1308 }
1309 
__mptcp_make_csum(u64 data_seq,u32 subflow_seq,u16 data_len,__wsum sum)1310 __sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
1311 {
1312 	struct csum_pseudo_header header;
1313 	__wsum csum;
1314 
1315 	/* cfr RFC 8684 3.3.1.:
1316 	 * the data sequence number used in the pseudo-header is
1317 	 * always the 64-bit value, irrespective of what length is used in the
1318 	 * DSS option itself.
1319 	 */
1320 	header.data_seq = cpu_to_be64(data_seq);
1321 	header.subflow_seq = htonl(subflow_seq);
1322 	header.data_len = htons(data_len);
1323 	header.csum = 0;
1324 
1325 	csum = csum_partial(&header, sizeof(header), sum);
1326 	return csum_fold(csum);
1327 }
1328 
mptcp_make_csum(const struct mptcp_ext * mpext)1329 static __sum16 mptcp_make_csum(const struct mptcp_ext *mpext)
1330 {
1331 	return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
1332 				 ~csum_unfold(mpext->csum));
1333 }
1334 
put_len_csum(u16 len,__sum16 csum,void * data)1335 static void put_len_csum(u16 len, __sum16 csum, void *data)
1336 {
1337 	__sum16 *sumptr = data + 2;
1338 	__be16 *ptr = data;
1339 
1340 	put_unaligned_be16(len, ptr);
1341 
1342 	put_unaligned(csum, sumptr);
1343 }
1344 
mptcp_write_options(struct tcphdr * th,__be32 * ptr,struct tcp_sock * tp,struct mptcp_out_options * opts)1345 void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
1346 			 struct mptcp_out_options *opts)
1347 {
1348 	const struct sock *ssk = (const struct sock *)tp;
1349 	struct mptcp_subflow_context *subflow;
1350 
1351 	/* Which options can be used together?
1352 	 *
1353 	 * X: mutually exclusive
1354 	 * O: often used together
1355 	 * C: can be used together in some cases
1356 	 * P: could be used together but we prefer not to (optimisations)
1357 	 *
1358 	 *  Opt: | MPC  | MPJ  | DSS  | ADD  |  RM  | PRIO | FAIL |  FC  |
1359 	 * ------|------|------|------|------|------|------|------|------|
1360 	 *  MPC  |------|------|------|------|------|------|------|------|
1361 	 *  MPJ  |  X   |------|------|------|------|------|------|------|
1362 	 *  DSS  |  X   |  X   |------|------|------|------|------|------|
1363 	 *  ADD  |  X   |  X   |  P   |------|------|------|------|------|
1364 	 *  RM   |  C   |  C   |  C   |  P   |------|------|------|------|
1365 	 *  PRIO |  X   |  C   |  C   |  C   |  C   |------|------|------|
1366 	 *  FAIL |  X   |  X   |  C   |  X   |  X   |  X   |------|------|
1367 	 *  FC   |  X   |  X   |  X   |  X   |  X   |  X   |  X   |------|
1368 	 *  RST  |  X   |  X   |  X   |  X   |  X   |  X   |  O   |  O   |
1369 	 * ------|------|------|------|------|------|------|------|------|
1370 	 *
1371 	 * The same applies in mptcp_established_options() function.
1372 	 */
1373 	if (likely(OPTION_MPTCP_DSS & opts->suboptions)) {
1374 		struct mptcp_ext *mpext = &opts->ext_copy;
1375 		u8 len = TCPOLEN_MPTCP_DSS_BASE;
1376 		u8 flags = 0;
1377 
1378 		if (mpext->use_ack) {
1379 			flags = MPTCP_DSS_HAS_ACK;
1380 			if (mpext->ack64) {
1381 				len += TCPOLEN_MPTCP_DSS_ACK64;
1382 				flags |= MPTCP_DSS_ACK64;
1383 			} else {
1384 				len += TCPOLEN_MPTCP_DSS_ACK32;
1385 			}
1386 		}
1387 
1388 		if (mpext->use_map) {
1389 			len += TCPOLEN_MPTCP_DSS_MAP64;
1390 
1391 			/* Use only 64-bit mapping flags for now, add
1392 			 * support for optional 32-bit mappings later.
1393 			 */
1394 			flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1395 			if (mpext->data_fin)
1396 				flags |= MPTCP_DSS_DATA_FIN;
1397 
1398 			if (opts->csum_reqd)
1399 				len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1400 		}
1401 
1402 		*ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1403 
1404 		if (mpext->use_ack) {
1405 			if (mpext->ack64) {
1406 				put_unaligned_be64(mpext->data_ack, ptr);
1407 				ptr += 2;
1408 			} else {
1409 				put_unaligned_be32(mpext->data_ack32, ptr);
1410 				ptr += 1;
1411 			}
1412 		}
1413 
1414 		if (mpext->use_map) {
1415 			put_unaligned_be64(mpext->data_seq, ptr);
1416 			ptr += 2;
1417 			put_unaligned_be32(mpext->subflow_seq, ptr);
1418 			ptr += 1;
1419 			if (opts->csum_reqd) {
1420 				/* data_len == 0 is reserved for the infinite mapping,
1421 				 * the checksum will also be set to 0.
1422 				 */
1423 				put_len_csum(mpext->data_len,
1424 					     (mpext->data_len ? mptcp_make_csum(mpext) : 0),
1425 					     ptr);
1426 			} else {
1427 				put_unaligned_be32(mpext->data_len << 16 |
1428 						   TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1429 			}
1430 			ptr += 1;
1431 		}
1432 
1433 		/* We might need to add MP_FAIL options in rare cases */
1434 		if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions))
1435 			goto mp_fail;
1436 	} else if (OPTIONS_MPTCP_MPC & opts->suboptions) {
1437 		u8 len, flag = MPTCP_CAP_HMAC_SHA256;
1438 
1439 		if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
1440 			len = TCPOLEN_MPTCP_MPC_SYN;
1441 		} else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
1442 			len = TCPOLEN_MPTCP_MPC_SYNACK;
1443 		} else if (opts->data_len) {
1444 			len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1445 			if (opts->csum_reqd)
1446 				len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1447 		} else {
1448 			len = TCPOLEN_MPTCP_MPC_ACK;
1449 		}
1450 
1451 		if (opts->csum_reqd)
1452 			flag |= MPTCP_CAP_CHECKSUM_REQD;
1453 
1454 		if (!opts->allow_join_id0)
1455 			flag |= MPTCP_CAP_DENY_JOIN_ID0;
1456 
1457 		*ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1458 				      MPTCP_SUPPORTED_VERSION,
1459 				      flag);
1460 
1461 		if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1462 		    opts->suboptions))
1463 			goto mp_capable_done;
1464 
1465 		put_unaligned_be64(opts->sndr_key, ptr);
1466 		ptr += 2;
1467 		if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1468 			goto mp_capable_done;
1469 
1470 		put_unaligned_be64(opts->rcvr_key, ptr);
1471 		ptr += 2;
1472 		if (!opts->data_len)
1473 			goto mp_capable_done;
1474 
1475 		if (opts->csum_reqd) {
1476 			put_len_csum(opts->data_len,
1477 				     __mptcp_make_csum(opts->data_seq,
1478 						       opts->subflow_seq,
1479 						       opts->data_len,
1480 						       ~csum_unfold(opts->csum)),
1481 				     ptr);
1482 		} else {
1483 			put_unaligned_be32(opts->data_len << 16 |
1484 					   TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1485 		}
1486 		ptr += 1;
1487 
1488 		/* MPC is additionally mutually exclusive with MP_PRIO */
1489 		goto mp_capable_done;
1490 	} else if (OPTIONS_MPTCP_MPJ & opts->suboptions) {
1491 		if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1492 			*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1493 					      TCPOLEN_MPTCP_MPJ_SYN,
1494 					      opts->backup, opts->join_id);
1495 			put_unaligned_be32(opts->token, ptr);
1496 			ptr += 1;
1497 			put_unaligned_be32(opts->nonce, ptr);
1498 			ptr += 1;
1499 		} else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1500 			*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1501 					      TCPOLEN_MPTCP_MPJ_SYNACK,
1502 					      opts->backup, opts->join_id);
1503 			put_unaligned_be64(opts->thmac, ptr);
1504 			ptr += 2;
1505 			put_unaligned_be32(opts->nonce, ptr);
1506 			ptr += 1;
1507 		} else {
1508 			*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1509 					      TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1510 			memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1511 			ptr += 5;
1512 		}
1513 	} else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1514 		u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1515 		u8 echo = MPTCP_ADDR_ECHO;
1516 
1517 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1518 		if (opts->addr.family == AF_INET6)
1519 			len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1520 #endif
1521 
1522 		if (opts->addr.port)
1523 			len += TCPOLEN_MPTCP_PORT_LEN;
1524 
1525 		if (opts->ahmac) {
1526 			len += sizeof(opts->ahmac);
1527 			echo = 0;
1528 		}
1529 
1530 		*ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1531 				      len, echo, opts->addr.id);
1532 		if (opts->addr.family == AF_INET) {
1533 			memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1534 			ptr += 1;
1535 		}
1536 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1537 		else if (opts->addr.family == AF_INET6) {
1538 			memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1539 			ptr += 4;
1540 		}
1541 #endif
1542 
1543 		if (!opts->addr.port) {
1544 			if (opts->ahmac) {
1545 				put_unaligned_be64(opts->ahmac, ptr);
1546 				ptr += 2;
1547 			}
1548 		} else {
1549 			u16 port = ntohs(opts->addr.port);
1550 
1551 			if (opts->ahmac) {
1552 				u8 *bptr = (u8 *)ptr;
1553 
1554 				put_unaligned_be16(port, bptr);
1555 				bptr += 2;
1556 				put_unaligned_be64(opts->ahmac, bptr);
1557 				bptr += 8;
1558 				put_unaligned_be16(TCPOPT_NOP << 8 |
1559 						   TCPOPT_NOP, bptr);
1560 
1561 				ptr += 3;
1562 			} else {
1563 				put_unaligned_be32(port << 16 |
1564 						   TCPOPT_NOP << 8 |
1565 						   TCPOPT_NOP, ptr);
1566 				ptr += 1;
1567 			}
1568 		}
1569 	} else if (unlikely(OPTION_MPTCP_FASTCLOSE & opts->suboptions)) {
1570 		/* FASTCLOSE is mutually exclusive with others except RST */
1571 		*ptr++ = mptcp_option(MPTCPOPT_MP_FASTCLOSE,
1572 				      TCPOLEN_MPTCP_FASTCLOSE,
1573 				      0, 0);
1574 		put_unaligned_be64(opts->rcvr_key, ptr);
1575 		ptr += 2;
1576 
1577 		if (OPTION_MPTCP_RST & opts->suboptions)
1578 			goto mp_rst;
1579 		return;
1580 	} else if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) {
1581 mp_fail:
1582 		/* MP_FAIL is mutually exclusive with others except RST */
1583 		subflow = mptcp_subflow_ctx(ssk);
1584 		subflow->send_mp_fail = 0;
1585 
1586 		*ptr++ = mptcp_option(MPTCPOPT_MP_FAIL,
1587 				      TCPOLEN_MPTCP_FAIL,
1588 				      0, 0);
1589 		put_unaligned_be64(opts->fail_seq, ptr);
1590 		ptr += 2;
1591 
1592 		if (OPTION_MPTCP_RST & opts->suboptions)
1593 			goto mp_rst;
1594 		return;
1595 	} else if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
1596 mp_rst:
1597 		*ptr++ = mptcp_option(MPTCPOPT_RST,
1598 				      TCPOLEN_MPTCP_RST,
1599 				      opts->reset_transient,
1600 				      opts->reset_reason);
1601 		return;
1602 	}
1603 
1604 	if (OPTION_MPTCP_PRIO & opts->suboptions) {
1605 		subflow = mptcp_subflow_ctx(ssk);
1606 		subflow->send_mp_prio = 0;
1607 
1608 		*ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1609 				      TCPOLEN_MPTCP_PRIO,
1610 				      opts->backup, TCPOPT_NOP);
1611 
1612 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPPRIOTX);
1613 	}
1614 
1615 mp_capable_done:
1616 	if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1617 		u8 i = 1;
1618 
1619 		*ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1620 				      TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1621 				      0, opts->rm_list.ids[0]);
1622 
1623 		while (i < opts->rm_list.nr) {
1624 			u8 id1, id2, id3, id4;
1625 
1626 			id1 = opts->rm_list.ids[i];
1627 			id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1628 			id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1629 			id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1630 			put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1631 			ptr += 1;
1632 			i += 4;
1633 		}
1634 	}
1635 
1636 	if (tp)
1637 		mptcp_set_rwin(tp, th);
1638 }
1639 
mptcp_get_reset_option(const struct sk_buff * skb)1640 __be32 mptcp_get_reset_option(const struct sk_buff *skb)
1641 {
1642 	const struct mptcp_ext *ext = mptcp_get_ext(skb);
1643 	u8 flags, reason;
1644 
1645 	if (ext) {
1646 		flags = ext->reset_transient;
1647 		reason = ext->reset_reason;
1648 
1649 		return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1650 				    flags, reason);
1651 	}
1652 
1653 	return htonl(0u);
1654 }
1655 EXPORT_SYMBOL_GPL(mptcp_get_reset_option);
1656