1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * net/dccp/input.c
4 *
5 * An implementation of the DCCP protocol
6 * Arnaldo Carvalho de Melo <acme@conectiva.com.br>
7 */
8
9 #include <linux/dccp.h>
10 #include <linux/skbuff.h>
11 #include <linux/slab.h>
12
13 #include <net/sock.h>
14
15 #include "ackvec.h"
16 #include "ccid.h"
17 #include "dccp.h"
18
19 /* rate-limit for syncs in reply to sequence-invalid packets; RFC 4340, 7.5.4 */
20 int sysctl_dccp_sync_ratelimit __read_mostly = HZ / 8;
21
22 static void dccp_enqueue_skb(struct sock *sk, struct sk_buff *skb)
23 {
24 __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
25 __skb_queue_tail(&sk->sk_receive_queue, skb);
26 skb_set_owner_r(skb, sk);
27 sk->sk_data_ready(sk);
28 }
29
30 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
31 {
32 /*
33 * On receiving Close/CloseReq, both RD/WR shutdown are performed.
34 * RFC 4340, 8.3 says that we MAY send further Data/DataAcks after
35 * receiving the closing segment, but there is no guarantee that such
36 * data will be processed at all.
37 */
38 sk->sk_shutdown = SHUTDOWN_MASK;
39 sock_set_flag(sk, SOCK_DONE);
40 dccp_enqueue_skb(sk, skb);
41 }
42
43 static int dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
44 {
45 int queued = 0;
46
47 switch (sk->sk_state) {
48 /*
49 * We ignore Close when received in one of the following states:
50 * - CLOSED (may be a late or duplicate packet)
51 * - PASSIVE_CLOSEREQ (the peer has sent a CloseReq earlier)
52 * - RESPOND (already handled by dccp_check_req)
53 */
54 case DCCP_CLOSING:
55 /*
56 * Simultaneous-close: receiving a Close after sending one. This
57 * can happen if both client and server perform active-close and
58 * will result in an endless ping-pong of crossing and retrans-
59 * mitted Close packets, which only terminates when one of the
60 * nodes times out (min. 64 seconds). Quicker convergence can be
61 * achieved when one of the nodes acts as tie-breaker.
62 * This is ok as both ends are done with data transfer and each
63 * end is just waiting for the other to acknowledge termination.
64 */
65 if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT)
66 break;
67 /* fall through */
68 case DCCP_REQUESTING:
69 case DCCP_ACTIVE_CLOSEREQ:
70 dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
71 dccp_done(sk);
72 break;
73 case DCCP_OPEN:
74 case DCCP_PARTOPEN:
75 /* Give waiting application a chance to read pending data */
76 queued = 1;
77 dccp_fin(sk, skb);
78 dccp_set_state(sk, DCCP_PASSIVE_CLOSE);
79 /* fall through */
80 case DCCP_PASSIVE_CLOSE:
81 /*
82 * Retransmitted Close: we have already enqueued the first one.
83 */
84 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
85 }
86 return queued;
87 }
88
89 static int dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
90 {
91 int queued = 0;
92
93 /*
94 * Step 7: Check for unexpected packet types
95 * If (S.is_server and P.type == CloseReq)
96 * Send Sync packet acknowledging P.seqno
97 * Drop packet and return
98 */
99 if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
100 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
101 return queued;
102 }
103
104 /* Step 13: process relevant Client states < CLOSEREQ */
105 switch (sk->sk_state) {
106 case DCCP_REQUESTING:
107 dccp_send_close(sk, 0);
108 dccp_set_state(sk, DCCP_CLOSING);
109 break;
110 case DCCP_OPEN:
111 case DCCP_PARTOPEN:
112 /* Give waiting application a chance to read pending data */
113 queued = 1;
114 dccp_fin(sk, skb);
115 dccp_set_state(sk, DCCP_PASSIVE_CLOSEREQ);
116 /* fall through */
117 case DCCP_PASSIVE_CLOSEREQ:
118 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
119 }
120 return queued;
121 }
122
123 static u16 dccp_reset_code_convert(const u8 code)
124 {
125 static const u16 error_code[] = {
126 [DCCP_RESET_CODE_CLOSED] = 0, /* normal termination */
127 [DCCP_RESET_CODE_UNSPECIFIED] = 0, /* nothing known */
128 [DCCP_RESET_CODE_ABORTED] = ECONNRESET,
129
130 [DCCP_RESET_CODE_NO_CONNECTION] = ECONNREFUSED,
131 [DCCP_RESET_CODE_CONNECTION_REFUSED] = ECONNREFUSED,
132 [DCCP_RESET_CODE_TOO_BUSY] = EUSERS,
133 [DCCP_RESET_CODE_AGGRESSION_PENALTY] = EDQUOT,
134
135 [DCCP_RESET_CODE_PACKET_ERROR] = ENOMSG,
136 [DCCP_RESET_CODE_BAD_INIT_COOKIE] = EBADR,
137 [DCCP_RESET_CODE_BAD_SERVICE_CODE] = EBADRQC,
138 [DCCP_RESET_CODE_OPTION_ERROR] = EILSEQ,
139 [DCCP_RESET_CODE_MANDATORY_ERROR] = EOPNOTSUPP,
140 };
141
142 return code >= DCCP_MAX_RESET_CODES ? 0 : error_code[code];
143 }
144
145 static void dccp_rcv_reset(struct sock *sk, struct sk_buff *skb)
146 {
147 u16 err = dccp_reset_code_convert(dccp_hdr_reset(skb)->dccph_reset_code);
148
149 sk->sk_err = err;
150
151 /* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
152 dccp_fin(sk, skb);
153
154 if (err && !sock_flag(sk, SOCK_DEAD))
155 sk_wake_async(sk, SOCK_WAKE_IO, POLL_ERR);
156 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
157 }
158
159 static void dccp_handle_ackvec_processing(struct sock *sk, struct sk_buff *skb)
160 {
161 struct dccp_ackvec *av = dccp_sk(sk)->dccps_hc_rx_ackvec;
162
163 if (av == NULL)
164 return;
165 if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
166 dccp_ackvec_clear_state(av, DCCP_SKB_CB(skb)->dccpd_ack_seq);
167 dccp_ackvec_input(av, skb);
168 }
169
170 static void dccp_deliver_input_to_ccids(struct sock *sk, struct sk_buff *skb)
171 {
172 const struct dccp_sock *dp = dccp_sk(sk);
173
174 /* Don't deliver to RX CCID when node has shut down read end. */
175 if (!(sk->sk_shutdown & RCV_SHUTDOWN))
176 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
177 /*
178 * Until the TX queue has been drained, we can not honour SHUT_WR, since
179 * we need received feedback as input to adjust congestion control.
180 */
181 if (sk->sk_write_queue.qlen > 0 || !(sk->sk_shutdown & SEND_SHUTDOWN))
182 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
183 }
184
185 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
186 {
187 const struct dccp_hdr *dh = dccp_hdr(skb);
188 struct dccp_sock *dp = dccp_sk(sk);
189 u64 lswl, lawl, seqno = DCCP_SKB_CB(skb)->dccpd_seq,
190 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
191
192 /*
193 * Step 5: Prepare sequence numbers for Sync
194 * If P.type == Sync or P.type == SyncAck,
195 * If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
196 * / * P is valid, so update sequence number variables
197 * accordingly. After this update, P will pass the tests
198 * in Step 6. A SyncAck is generated if necessary in
199 * Step 15 * /
200 * Update S.GSR, S.SWL, S.SWH
201 * Otherwise,
202 * Drop packet and return
203 */
204 if (dh->dccph_type == DCCP_PKT_SYNC ||
205 dh->dccph_type == DCCP_PKT_SYNCACK) {
206 if (between48(ackno, dp->dccps_awl, dp->dccps_awh) &&
207 dccp_delta_seqno(dp->dccps_swl, seqno) >= 0)
208 dccp_update_gsr(sk, seqno);
209 else
210 return -1;
211 }
212
213 /*
214 * Step 6: Check sequence numbers
215 * Let LSWL = S.SWL and LAWL = S.AWL
216 * If P.type == CloseReq or P.type == Close or P.type == Reset,
217 * LSWL := S.GSR + 1, LAWL := S.GAR
218 * If LSWL <= P.seqno <= S.SWH
219 * and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
220 * Update S.GSR, S.SWL, S.SWH
221 * If P.type != Sync,
222 * Update S.GAR
223 */
224 lswl = dp->dccps_swl;
225 lawl = dp->dccps_awl;
226
227 if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
228 dh->dccph_type == DCCP_PKT_CLOSE ||
229 dh->dccph_type == DCCP_PKT_RESET) {
230 lswl = ADD48(dp->dccps_gsr, 1);
231 lawl = dp->dccps_gar;
232 }
233
234 if (between48(seqno, lswl, dp->dccps_swh) &&
235 (ackno == DCCP_PKT_WITHOUT_ACK_SEQ ||
236 between48(ackno, lawl, dp->dccps_awh))) {
237 dccp_update_gsr(sk, seqno);
238
239 if (dh->dccph_type != DCCP_PKT_SYNC &&
240 ackno != DCCP_PKT_WITHOUT_ACK_SEQ &&
241 after48(ackno, dp->dccps_gar))
242 dp->dccps_gar = ackno;
243 } else {
244 unsigned long now = jiffies;
245 /*
246 * Step 6: Check sequence numbers
247 * Otherwise,
248 * If P.type == Reset,
249 * Send Sync packet acknowledging S.GSR
250 * Otherwise,
251 * Send Sync packet acknowledging P.seqno
252 * Drop packet and return
253 *
254 * These Syncs are rate-limited as per RFC 4340, 7.5.4:
255 * at most 1 / (dccp_sync_rate_limit * HZ) Syncs per second.
256 */
257 if (time_before(now, (dp->dccps_rate_last +
258 sysctl_dccp_sync_ratelimit)))
259 return -1;
260
261 DCCP_WARN("Step 6 failed for %s packet, "
262 "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
263 "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
264 "sending SYNC...\n", dccp_packet_name(dh->dccph_type),
265 (unsigned long long) lswl, (unsigned long long) seqno,
266 (unsigned long long) dp->dccps_swh,
267 (ackno == DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist"
268 : "exists",
269 (unsigned long long) lawl, (unsigned long long) ackno,
270 (unsigned long long) dp->dccps_awh);
271
272 dp->dccps_rate_last = now;
273
274 if (dh->dccph_type == DCCP_PKT_RESET)
275 seqno = dp->dccps_gsr;
276 dccp_send_sync(sk, seqno, DCCP_PKT_SYNC);
277 return -1;
278 }
279
280 return 0;
281 }
282
283 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
284 const struct dccp_hdr *dh, const unsigned int len)
285 {
286 struct dccp_sock *dp = dccp_sk(sk);
287
288 switch (dccp_hdr(skb)->dccph_type) {
289 case DCCP_PKT_DATAACK:
290 case DCCP_PKT_DATA:
291 /*
292 * FIXME: schedule DATA_DROPPED (RFC 4340, 11.7.2) if and when
293 * - sk_shutdown == RCV_SHUTDOWN, use Code 1, "Not Listening"
294 * - sk_receive_queue is full, use Code 2, "Receive Buffer"
295 */
296 dccp_enqueue_skb(sk, skb);
297 return 0;
298 case DCCP_PKT_ACK:
299 goto discard;
300 case DCCP_PKT_RESET:
301 /*
302 * Step 9: Process Reset
303 * If P.type == Reset,
304 * Tear down connection
305 * S.state := TIMEWAIT
306 * Set TIMEWAIT timer
307 * Drop packet and return
308 */
309 dccp_rcv_reset(sk, skb);
310 return 0;
311 case DCCP_PKT_CLOSEREQ:
312 if (dccp_rcv_closereq(sk, skb))
313 return 0;
314 goto discard;
315 case DCCP_PKT_CLOSE:
316 if (dccp_rcv_close(sk, skb))
317 return 0;
318 goto discard;
319 case DCCP_PKT_REQUEST:
320 /* Step 7
321 * or (S.is_server and P.type == Response)
322 * or (S.is_client and P.type == Request)
323 * or (S.state >= OPEN and P.type == Request
324 * and P.seqno >= S.OSR)
325 * or (S.state >= OPEN and P.type == Response
326 * and P.seqno >= S.OSR)
327 * or (S.state == RESPOND and P.type == Data),
328 * Send Sync packet acknowledging P.seqno
329 * Drop packet and return
330 */
331 if (dp->dccps_role != DCCP_ROLE_LISTEN)
332 goto send_sync;
333 goto check_seq;
334 case DCCP_PKT_RESPONSE:
335 if (dp->dccps_role != DCCP_ROLE_CLIENT)
336 goto send_sync;
337 check_seq:
338 if (dccp_delta_seqno(dp->dccps_osr,
339 DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
340 send_sync:
341 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
342 DCCP_PKT_SYNC);
343 }
344 break;
345 case DCCP_PKT_SYNC:
346 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
347 DCCP_PKT_SYNCACK);
348 /*
349 * From RFC 4340, sec. 5.7
350 *
351 * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
352 * MAY have non-zero-length application data areas, whose
353 * contents receivers MUST ignore.
354 */
355 goto discard;
356 }
357
358 DCCP_INC_STATS(DCCP_MIB_INERRS);
359 discard:
360 __kfree_skb(skb);
361 return 0;
362 }
363
364 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
365 const struct dccp_hdr *dh, const unsigned int len)
366 {
367 if (dccp_check_seqno(sk, skb))
368 goto discard;
369
370 if (dccp_parse_options(sk, NULL, skb))
371 return 1;
372
373 dccp_handle_ackvec_processing(sk, skb);
374 dccp_deliver_input_to_ccids(sk, skb);
375
376 return __dccp_rcv_established(sk, skb, dh, len);
377 discard:
378 __kfree_skb(skb);
379 return 0;
380 }
381
382 EXPORT_SYMBOL_GPL(dccp_rcv_established);
383
384 static int dccp_rcv_request_sent_state_process(struct sock *sk,
385 struct sk_buff *skb,
386 const struct dccp_hdr *dh,
387 const unsigned int len)
388 {
389 /*
390 * Step 4: Prepare sequence numbers in REQUEST
391 * If S.state == REQUEST,
392 * If (P.type == Response or P.type == Reset)
393 * and S.AWL <= P.ackno <= S.AWH,
394 * / * Set sequence number variables corresponding to the
395 * other endpoint, so P will pass the tests in Step 6 * /
396 * Set S.GSR, S.ISR, S.SWL, S.SWH
397 * / * Response processing continues in Step 10; Reset
398 * processing continues in Step 9 * /
399 */
400 if (dh->dccph_type == DCCP_PKT_RESPONSE) {
401 const struct inet_connection_sock *icsk = inet_csk(sk);
402 struct dccp_sock *dp = dccp_sk(sk);
403 long tstamp = dccp_timestamp();
404
405 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
406 dp->dccps_awl, dp->dccps_awh)) {
407 dccp_pr_debug("invalid ackno: S.AWL=%llu, "
408 "P.ackno=%llu, S.AWH=%llu\n",
409 (unsigned long long)dp->dccps_awl,
410 (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
411 (unsigned long long)dp->dccps_awh);
412 goto out_invalid_packet;
413 }
414
415 /*
416 * If option processing (Step 8) failed, return 1 here so that
417 * dccp_v4_do_rcv() sends a Reset. The Reset code depends on
418 * the option type and is set in dccp_parse_options().
419 */
420 if (dccp_parse_options(sk, NULL, skb))
421 return 1;
422
423 /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
424 if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
425 dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
426 dp->dccps_options_received.dccpor_timestamp_echo));
427
428 /* Stop the REQUEST timer */
429 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
430 WARN_ON(sk->sk_send_head == NULL);
431 kfree_skb(sk->sk_send_head);
432 sk->sk_send_head = NULL;
433
434 /*
435 * Set ISR, GSR from packet. ISS was set in dccp_v{4,6}_connect
436 * and GSS in dccp_transmit_skb(). Setting AWL/AWH and SWL/SWH
437 * is done as part of activating the feature values below, since
438 * these settings depend on the local/remote Sequence Window
439 * features, which were undefined or not confirmed until now.
440 */
441 dp->dccps_gsr = dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
442
443 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
444
445 /*
446 * Step 10: Process REQUEST state (second part)
447 * If S.state == REQUEST,
448 * / * If we get here, P is a valid Response from the
449 * server (see Step 4), and we should move to
450 * PARTOPEN state. PARTOPEN means send an Ack,
451 * don't send Data packets, retransmit Acks
452 * periodically, and always include any Init Cookie
453 * from the Response * /
454 * S.state := PARTOPEN
455 * Set PARTOPEN timer
456 * Continue with S.state == PARTOPEN
457 * / * Step 12 will send the Ack completing the
458 * three-way handshake * /
459 */
460 dccp_set_state(sk, DCCP_PARTOPEN);
461
462 /*
463 * If feature negotiation was successful, activate features now;
464 * an activation failure means that this host could not activate
465 * one ore more features (e.g. insufficient memory), which would
466 * leave at least one feature in an undefined state.
467 */
468 if (dccp_feat_activate_values(sk, &dp->dccps_featneg))
469 goto unable_to_proceed;
470
471 /* Make sure socket is routed, for correct metrics. */
472 icsk->icsk_af_ops->rebuild_header(sk);
473
474 if (!sock_flag(sk, SOCK_DEAD)) {
475 sk->sk_state_change(sk);
476 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
477 }
478
479 if (sk->sk_write_pending || inet_csk_in_pingpong_mode(sk) ||
480 icsk->icsk_accept_queue.rskq_defer_accept) {
481 /* Save one ACK. Data will be ready after
482 * several ticks, if write_pending is set.
483 *
484 * It may be deleted, but with this feature tcpdumps
485 * look so _wonderfully_ clever, that I was not able
486 * to stand against the temptation 8) --ANK
487 */
488 /*
489 * OK, in DCCP we can as well do a similar trick, its
490 * even in the draft, but there is no need for us to
491 * schedule an ack here, as dccp_sendmsg does this for
492 * us, also stated in the draft. -acme
493 */
494 __kfree_skb(skb);
495 return 0;
496 }
497 dccp_send_ack(sk);
498 return -1;
499 }
500
501 out_invalid_packet:
502 /* dccp_v4_do_rcv will send a reset */
503 DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
504 return 1;
505
506 unable_to_proceed:
507 DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_ABORTED;
508 /*
509 * We mark this socket as no longer usable, so that the loop in
510 * dccp_sendmsg() terminates and the application gets notified.
511 */
512 dccp_set_state(sk, DCCP_CLOSED);
513 sk->sk_err = ECOMM;
514 return 1;
515 }
516
517 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
518 struct sk_buff *skb,
519 const struct dccp_hdr *dh,
520 const unsigned int len)
521 {
522 struct dccp_sock *dp = dccp_sk(sk);
523 u32 sample = dp->dccps_options_received.dccpor_timestamp_echo;
524 int queued = 0;
525
526 switch (dh->dccph_type) {
527 case DCCP_PKT_RESET:
528 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
529 break;
530 case DCCP_PKT_DATA:
531 if (sk->sk_state == DCCP_RESPOND)
532 break;
533 /* fall through */
534 case DCCP_PKT_DATAACK:
535 case DCCP_PKT_ACK:
536 /*
537 * FIXME: we should be resetting the PARTOPEN (DELACK) timer
538 * here but only if we haven't used the DELACK timer for
539 * something else, like sending a delayed ack for a TIMESTAMP
540 * echo, etc, for now were not clearing it, sending an extra
541 * ACK when there is nothing else to do in DELACK is not a big
542 * deal after all.
543 */
544
545 /* Stop the PARTOPEN timer */
546 if (sk->sk_state == DCCP_PARTOPEN)
547 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
548
549 /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
550 if (likely(sample)) {
551 long delta = dccp_timestamp() - sample;
552
553 dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * delta);
554 }
555
556 dp->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
557 dccp_set_state(sk, DCCP_OPEN);
558
559 if (dh->dccph_type == DCCP_PKT_DATAACK ||
560 dh->dccph_type == DCCP_PKT_DATA) {
561 __dccp_rcv_established(sk, skb, dh, len);
562 queued = 1; /* packet was queued
563 (by __dccp_rcv_established) */
564 }
565 break;
566 }
567
568 return queued;
569 }
570
571 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
572 struct dccp_hdr *dh, unsigned int len)
573 {
574 struct dccp_sock *dp = dccp_sk(sk);
575 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
576 const int old_state = sk->sk_state;
577 bool acceptable;
578 int queued = 0;
579
580 /*
581 * Step 3: Process LISTEN state
582 *
583 * If S.state == LISTEN,
584 * If P.type == Request or P contains a valid Init Cookie option,
585 * (* Must scan the packet's options to check for Init
586 * Cookies. Only Init Cookies are processed here,
587 * however; other options are processed in Step 8. This
588 * scan need only be performed if the endpoint uses Init
589 * Cookies *)
590 * (* Generate a new socket and switch to that socket *)
591 * Set S := new socket for this port pair
592 * S.state = RESPOND
593 * Choose S.ISS (initial seqno) or set from Init Cookies
594 * Initialize S.GAR := S.ISS
595 * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
596 * Cookies Continue with S.state == RESPOND
597 * (* A Response packet will be generated in Step 11 *)
598 * Otherwise,
599 * Generate Reset(No Connection) unless P.type == Reset
600 * Drop packet and return
601 */
602 if (sk->sk_state == DCCP_LISTEN) {
603 if (dh->dccph_type == DCCP_PKT_REQUEST) {
604 /* It is possible that we process SYN packets from backlog,
605 * so we need to make sure to disable BH and RCU right there.
606 */
607 rcu_read_lock();
608 local_bh_disable();
609 acceptable = inet_csk(sk)->icsk_af_ops->conn_request(sk, skb) >= 0;
610 local_bh_enable();
611 rcu_read_unlock();
612 if (!acceptable)
613 return 1;
614 consume_skb(skb);
615 return 0;
616 }
617 if (dh->dccph_type == DCCP_PKT_RESET)
618 goto discard;
619
620 /* Caller (dccp_v4_do_rcv) will send Reset */
621 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
622 return 1;
623 } else if (sk->sk_state == DCCP_CLOSED) {
624 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
625 return 1;
626 }
627
628 /* Step 6: Check sequence numbers (omitted in LISTEN/REQUEST state) */
629 if (sk->sk_state != DCCP_REQUESTING && dccp_check_seqno(sk, skb))
630 goto discard;
631
632 /*
633 * Step 7: Check for unexpected packet types
634 * If (S.is_server and P.type == Response)
635 * or (S.is_client and P.type == Request)
636 * or (S.state == RESPOND and P.type == Data),
637 * Send Sync packet acknowledging P.seqno
638 * Drop packet and return
639 */
640 if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
641 dh->dccph_type == DCCP_PKT_RESPONSE) ||
642 (dp->dccps_role == DCCP_ROLE_CLIENT &&
643 dh->dccph_type == DCCP_PKT_REQUEST) ||
644 (sk->sk_state == DCCP_RESPOND && dh->dccph_type == DCCP_PKT_DATA)) {
645 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
646 goto discard;
647 }
648
649 /* Step 8: Process options */
650 if (dccp_parse_options(sk, NULL, skb))
651 return 1;
652
653 /*
654 * Step 9: Process Reset
655 * If P.type == Reset,
656 * Tear down connection
657 * S.state := TIMEWAIT
658 * Set TIMEWAIT timer
659 * Drop packet and return
660 */
661 if (dh->dccph_type == DCCP_PKT_RESET) {
662 dccp_rcv_reset(sk, skb);
663 return 0;
664 } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) { /* Step 13 */
665 if (dccp_rcv_closereq(sk, skb))
666 return 0;
667 goto discard;
668 } else if (dh->dccph_type == DCCP_PKT_CLOSE) { /* Step 14 */
669 if (dccp_rcv_close(sk, skb))
670 return 0;
671 goto discard;
672 }
673
674 switch (sk->sk_state) {
675 case DCCP_REQUESTING:
676 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
677 if (queued >= 0)
678 return queued;
679
680 __kfree_skb(skb);
681 return 0;
682
683 case DCCP_PARTOPEN:
684 /* Step 8: if using Ack Vectors, mark packet acknowledgeable */
685 dccp_handle_ackvec_processing(sk, skb);
686 dccp_deliver_input_to_ccids(sk, skb);
687 /* fall through */
688 case DCCP_RESPOND:
689 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
690 dh, len);
691 break;
692 }
693
694 if (dh->dccph_type == DCCP_PKT_ACK ||
695 dh->dccph_type == DCCP_PKT_DATAACK) {
696 switch (old_state) {
697 case DCCP_PARTOPEN:
698 sk->sk_state_change(sk);
699 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
700 break;
701 }
702 } else if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
703 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
704 goto discard;
705 }
706
707 if (!queued) {
708 discard:
709 __kfree_skb(skb);
710 }
711 return 0;
712 }
713
714 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);
715
716 /**
717 * dccp_sample_rtt - Validate and finalise computation of RTT sample
718 * @delta: number of microseconds between packet and acknowledgment
719 *
720 * The routine is kept generic to work in different contexts. It should be
721 * called immediately when the ACK used for the RTT sample arrives.
722 */
723 u32 dccp_sample_rtt(struct sock *sk, long delta)
724 {
725 /* dccpor_elapsed_time is either zeroed out or set and > 0 */
726 delta -= dccp_sk(sk)->dccps_options_received.dccpor_elapsed_time * 10;
727
728 if (unlikely(delta <= 0)) {
729 DCCP_WARN("unusable RTT sample %ld, using min\n", delta);
730 return DCCP_SANE_RTT_MIN;
731 }
732 if (unlikely(delta > DCCP_SANE_RTT_MAX)) {
733 DCCP_WARN("RTT sample %ld too large, using max\n", delta);
734 return DCCP_SANE_RTT_MAX;
735 }
736
737 return delta;
738 }