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Linux/net/dccp/input.c

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  1 /*
  2  *  net/dccp/input.c
  3  *
  4  *  An implementation of the DCCP protocol
  5  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  6  *
  7  *      This program is free software; you can redistribute it and/or
  8  *      modify it under the terms of the GNU General Public License
  9  *      as published by the Free Software Foundation; either version
 10  *      2 of the License, or (at your option) any later version.
 11  */
 12 
 13 #include <linux/dccp.h>
 14 #include <linux/skbuff.h>
 15 #include <linux/slab.h>
 16 
 17 #include <net/sock.h>
 18 
 19 #include "ackvec.h"
 20 #include "ccid.h"
 21 #include "dccp.h"
 22 
 23 /* rate-limit for syncs in reply to sequence-invalid packets; RFC 4340, 7.5.4 */
 24 int sysctl_dccp_sync_ratelimit  __read_mostly = HZ / 8;
 25 
 26 static void dccp_enqueue_skb(struct sock *sk, struct sk_buff *skb)
 27 {
 28         __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
 29         __skb_queue_tail(&sk->sk_receive_queue, skb);
 30         skb_set_owner_r(skb, sk);
 31         sk->sk_data_ready(sk);
 32 }
 33 
 34 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
 35 {
 36         /*
 37          * On receiving Close/CloseReq, both RD/WR shutdown are performed.
 38          * RFC 4340, 8.3 says that we MAY send further Data/DataAcks after
 39          * receiving the closing segment, but there is no guarantee that such
 40          * data will be processed at all.
 41          */
 42         sk->sk_shutdown = SHUTDOWN_MASK;
 43         sock_set_flag(sk, SOCK_DONE);
 44         dccp_enqueue_skb(sk, skb);
 45 }
 46 
 47 static int dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
 48 {
 49         int queued = 0;
 50 
 51         switch (sk->sk_state) {
 52         /*
 53          * We ignore Close when received in one of the following states:
 54          *  - CLOSED            (may be a late or duplicate packet)
 55          *  - PASSIVE_CLOSEREQ  (the peer has sent a CloseReq earlier)
 56          *  - RESPOND           (already handled by dccp_check_req)
 57          */
 58         case DCCP_CLOSING:
 59                 /*
 60                  * Simultaneous-close: receiving a Close after sending one. This
 61                  * can happen if both client and server perform active-close and
 62                  * will result in an endless ping-pong of crossing and retrans-
 63                  * mitted Close packets, which only terminates when one of the
 64                  * nodes times out (min. 64 seconds). Quicker convergence can be
 65                  * achieved when one of the nodes acts as tie-breaker.
 66                  * This is ok as both ends are done with data transfer and each
 67                  * end is just waiting for the other to acknowledge termination.
 68                  */
 69                 if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT)
 70                         break;
 71                 /* fall through */
 72         case DCCP_REQUESTING:
 73         case DCCP_ACTIVE_CLOSEREQ:
 74                 dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
 75                 dccp_done(sk);
 76                 break;
 77         case DCCP_OPEN:
 78         case DCCP_PARTOPEN:
 79                 /* Give waiting application a chance to read pending data */
 80                 queued = 1;
 81                 dccp_fin(sk, skb);
 82                 dccp_set_state(sk, DCCP_PASSIVE_CLOSE);
 83                 /* fall through */
 84         case DCCP_PASSIVE_CLOSE:
 85                 /*
 86                  * Retransmitted Close: we have already enqueued the first one.
 87                  */
 88                 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
 89         }
 90         return queued;
 91 }
 92 
 93 static int dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
 94 {
 95         int queued = 0;
 96 
 97         /*
 98          *   Step 7: Check for unexpected packet types
 99          *      If (S.is_server and P.type == CloseReq)
100          *        Send Sync packet acknowledging P.seqno
101          *        Drop packet and return
102          */
103         if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
104                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
105                 return queued;
106         }
107 
108         /* Step 13: process relevant Client states < CLOSEREQ */
109         switch (sk->sk_state) {
110         case DCCP_REQUESTING:
111                 dccp_send_close(sk, 0);
112                 dccp_set_state(sk, DCCP_CLOSING);
113                 break;
114         case DCCP_OPEN:
115         case DCCP_PARTOPEN:
116                 /* Give waiting application a chance to read pending data */
117                 queued = 1;
118                 dccp_fin(sk, skb);
119                 dccp_set_state(sk, DCCP_PASSIVE_CLOSEREQ);
120                 /* fall through */
121         case DCCP_PASSIVE_CLOSEREQ:
122                 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
123         }
124         return queued;
125 }
126 
127 static u16 dccp_reset_code_convert(const u8 code)
128 {
129         const u16 error_code[] = {
130         [DCCP_RESET_CODE_CLOSED]             = 0,       /* normal termination */
131         [DCCP_RESET_CODE_UNSPECIFIED]        = 0,       /* nothing known */
132         [DCCP_RESET_CODE_ABORTED]            = ECONNRESET,
133 
134         [DCCP_RESET_CODE_NO_CONNECTION]      = ECONNREFUSED,
135         [DCCP_RESET_CODE_CONNECTION_REFUSED] = ECONNREFUSED,
136         [DCCP_RESET_CODE_TOO_BUSY]           = EUSERS,
137         [DCCP_RESET_CODE_AGGRESSION_PENALTY] = EDQUOT,
138 
139         [DCCP_RESET_CODE_PACKET_ERROR]       = ENOMSG,
140         [DCCP_RESET_CODE_BAD_INIT_COOKIE]    = EBADR,
141         [DCCP_RESET_CODE_BAD_SERVICE_CODE]   = EBADRQC,
142         [DCCP_RESET_CODE_OPTION_ERROR]       = EILSEQ,
143         [DCCP_RESET_CODE_MANDATORY_ERROR]    = EOPNOTSUPP,
144         };
145 
146         return code >= DCCP_MAX_RESET_CODES ? 0 : error_code[code];
147 }
148 
149 static void dccp_rcv_reset(struct sock *sk, struct sk_buff *skb)
150 {
151         u16 err = dccp_reset_code_convert(dccp_hdr_reset(skb)->dccph_reset_code);
152 
153         sk->sk_err = err;
154 
155         /* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
156         dccp_fin(sk, skb);
157 
158         if (err && !sock_flag(sk, SOCK_DEAD))
159                 sk_wake_async(sk, SOCK_WAKE_IO, POLL_ERR);
160         dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
161 }
162 
163 static void dccp_handle_ackvec_processing(struct sock *sk, struct sk_buff *skb)
164 {
165         struct dccp_ackvec *av = dccp_sk(sk)->dccps_hc_rx_ackvec;
166 
167         if (av == NULL)
168                 return;
169         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
170                 dccp_ackvec_clear_state(av, DCCP_SKB_CB(skb)->dccpd_ack_seq);
171         dccp_ackvec_input(av, skb);
172 }
173 
174 static void dccp_deliver_input_to_ccids(struct sock *sk, struct sk_buff *skb)
175 {
176         const struct dccp_sock *dp = dccp_sk(sk);
177 
178         /* Don't deliver to RX CCID when node has shut down read end. */
179         if (!(sk->sk_shutdown & RCV_SHUTDOWN))
180                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
181         /*
182          * Until the TX queue has been drained, we can not honour SHUT_WR, since
183          * we need received feedback as input to adjust congestion control.
184          */
185         if (sk->sk_write_queue.qlen > 0 || !(sk->sk_shutdown & SEND_SHUTDOWN))
186                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
187 }
188 
189 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
190 {
191         const struct dccp_hdr *dh = dccp_hdr(skb);
192         struct dccp_sock *dp = dccp_sk(sk);
193         u64 lswl, lawl, seqno = DCCP_SKB_CB(skb)->dccpd_seq,
194                         ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
195 
196         /*
197          *   Step 5: Prepare sequence numbers for Sync
198          *     If P.type == Sync or P.type == SyncAck,
199          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
200          *           / * P is valid, so update sequence number variables
201          *               accordingly.  After this update, P will pass the tests
202          *               in Step 6.  A SyncAck is generated if necessary in
203          *               Step 15 * /
204          *           Update S.GSR, S.SWL, S.SWH
205          *        Otherwise,
206          *           Drop packet and return
207          */
208         if (dh->dccph_type == DCCP_PKT_SYNC ||
209             dh->dccph_type == DCCP_PKT_SYNCACK) {
210                 if (between48(ackno, dp->dccps_awl, dp->dccps_awh) &&
211                     dccp_delta_seqno(dp->dccps_swl, seqno) >= 0)
212                         dccp_update_gsr(sk, seqno);
213                 else
214                         return -1;
215         }
216 
217         /*
218          *   Step 6: Check sequence numbers
219          *      Let LSWL = S.SWL and LAWL = S.AWL
220          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
221          *        LSWL := S.GSR + 1, LAWL := S.GAR
222          *      If LSWL <= P.seqno <= S.SWH
223          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
224          *        Update S.GSR, S.SWL, S.SWH
225          *        If P.type != Sync,
226          *           Update S.GAR
227          */
228         lswl = dp->dccps_swl;
229         lawl = dp->dccps_awl;
230 
231         if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
232             dh->dccph_type == DCCP_PKT_CLOSE ||
233             dh->dccph_type == DCCP_PKT_RESET) {
234                 lswl = ADD48(dp->dccps_gsr, 1);
235                 lawl = dp->dccps_gar;
236         }
237 
238         if (between48(seqno, lswl, dp->dccps_swh) &&
239             (ackno == DCCP_PKT_WITHOUT_ACK_SEQ ||
240              between48(ackno, lawl, dp->dccps_awh))) {
241                 dccp_update_gsr(sk, seqno);
242 
243                 if (dh->dccph_type != DCCP_PKT_SYNC &&
244                     ackno != DCCP_PKT_WITHOUT_ACK_SEQ &&
245                     after48(ackno, dp->dccps_gar))
246                         dp->dccps_gar = ackno;
247         } else {
248                 unsigned long now = jiffies;
249                 /*
250                  *   Step 6: Check sequence numbers
251                  *      Otherwise,
252                  *         If P.type == Reset,
253                  *            Send Sync packet acknowledging S.GSR
254                  *         Otherwise,
255                  *            Send Sync packet acknowledging P.seqno
256                  *      Drop packet and return
257                  *
258                  *   These Syncs are rate-limited as per RFC 4340, 7.5.4:
259                  *   at most 1 / (dccp_sync_rate_limit * HZ) Syncs per second.
260                  */
261                 if (time_before(now, (dp->dccps_rate_last +
262                                       sysctl_dccp_sync_ratelimit)))
263                         return -1;
264 
265                 DCCP_WARN("Step 6 failed for %s packet, "
266                           "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
267                           "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
268                           "sending SYNC...\n",  dccp_packet_name(dh->dccph_type),
269                           (unsigned long long) lswl, (unsigned long long) seqno,
270                           (unsigned long long) dp->dccps_swh,
271                           (ackno == DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist"
272                                                               : "exists",
273                           (unsigned long long) lawl, (unsigned long long) ackno,
274                           (unsigned long long) dp->dccps_awh);
275 
276                 dp->dccps_rate_last = now;
277 
278                 if (dh->dccph_type == DCCP_PKT_RESET)
279                         seqno = dp->dccps_gsr;
280                 dccp_send_sync(sk, seqno, DCCP_PKT_SYNC);
281                 return -1;
282         }
283 
284         return 0;
285 }
286 
287 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
288                                   const struct dccp_hdr *dh, const unsigned int len)
289 {
290         struct dccp_sock *dp = dccp_sk(sk);
291 
292         switch (dccp_hdr(skb)->dccph_type) {
293         case DCCP_PKT_DATAACK:
294         case DCCP_PKT_DATA:
295                 /*
296                  * FIXME: schedule DATA_DROPPED (RFC 4340, 11.7.2) if and when
297                  * - sk_shutdown == RCV_SHUTDOWN, use Code 1, "Not Listening"
298                  * - sk_receive_queue is full, use Code 2, "Receive Buffer"
299                  */
300                 dccp_enqueue_skb(sk, skb);
301                 return 0;
302         case DCCP_PKT_ACK:
303                 goto discard;
304         case DCCP_PKT_RESET:
305                 /*
306                  *  Step 9: Process Reset
307                  *      If P.type == Reset,
308                  *              Tear down connection
309                  *              S.state := TIMEWAIT
310                  *              Set TIMEWAIT timer
311                  *              Drop packet and return
312                  */
313                 dccp_rcv_reset(sk, skb);
314                 return 0;
315         case DCCP_PKT_CLOSEREQ:
316                 if (dccp_rcv_closereq(sk, skb))
317                         return 0;
318                 goto discard;
319         case DCCP_PKT_CLOSE:
320                 if (dccp_rcv_close(sk, skb))
321                         return 0;
322                 goto discard;
323         case DCCP_PKT_REQUEST:
324                 /* Step 7
325                  *   or (S.is_server and P.type == Response)
326                  *   or (S.is_client and P.type == Request)
327                  *   or (S.state >= OPEN and P.type == Request
328                  *      and P.seqno >= S.OSR)
329                  *    or (S.state >= OPEN and P.type == Response
330                  *      and P.seqno >= S.OSR)
331                  *    or (S.state == RESPOND and P.type == Data),
332                  *  Send Sync packet acknowledging P.seqno
333                  *  Drop packet and return
334                  */
335                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
336                         goto send_sync;
337                 goto check_seq;
338         case DCCP_PKT_RESPONSE:
339                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
340                         goto send_sync;
341 check_seq:
342                 if (dccp_delta_seqno(dp->dccps_osr,
343                                      DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
344 send_sync:
345                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
346                                        DCCP_PKT_SYNC);
347                 }
348                 break;
349         case DCCP_PKT_SYNC:
350                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
351                                DCCP_PKT_SYNCACK);
352                 /*
353                  * From RFC 4340, sec. 5.7
354                  *
355                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
356                  * MAY have non-zero-length application data areas, whose
357                  * contents receivers MUST ignore.
358                  */
359                 goto discard;
360         }
361 
362         DCCP_INC_STATS(DCCP_MIB_INERRS);
363 discard:
364         __kfree_skb(skb);
365         return 0;
366 }
367 
368 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
369                          const struct dccp_hdr *dh, const unsigned int len)
370 {
371         if (dccp_check_seqno(sk, skb))
372                 goto discard;
373 
374         if (dccp_parse_options(sk, NULL, skb))
375                 return 1;
376 
377         dccp_handle_ackvec_processing(sk, skb);
378         dccp_deliver_input_to_ccids(sk, skb);
379 
380         return __dccp_rcv_established(sk, skb, dh, len);
381 discard:
382         __kfree_skb(skb);
383         return 0;
384 }
385 
386 EXPORT_SYMBOL_GPL(dccp_rcv_established);
387 
388 static int dccp_rcv_request_sent_state_process(struct sock *sk,
389                                                struct sk_buff *skb,
390                                                const struct dccp_hdr *dh,
391                                                const unsigned int len)
392 {
393         /*
394          *  Step 4: Prepare sequence numbers in REQUEST
395          *     If S.state == REQUEST,
396          *        If (P.type == Response or P.type == Reset)
397          *              and S.AWL <= P.ackno <= S.AWH,
398          *           / * Set sequence number variables corresponding to the
399          *              other endpoint, so P will pass the tests in Step 6 * /
400          *           Set S.GSR, S.ISR, S.SWL, S.SWH
401          *           / * Response processing continues in Step 10; Reset
402          *              processing continues in Step 9 * /
403         */
404         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
405                 const struct inet_connection_sock *icsk = inet_csk(sk);
406                 struct dccp_sock *dp = dccp_sk(sk);
407                 long tstamp = dccp_timestamp();
408 
409                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
410                                dp->dccps_awl, dp->dccps_awh)) {
411                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
412                                       "P.ackno=%llu, S.AWH=%llu\n",
413                                       (unsigned long long)dp->dccps_awl,
414                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
415                                       (unsigned long long)dp->dccps_awh);
416                         goto out_invalid_packet;
417                 }
418 
419                 /*
420                  * If option processing (Step 8) failed, return 1 here so that
421                  * dccp_v4_do_rcv() sends a Reset. The Reset code depends on
422                  * the option type and is set in dccp_parse_options().
423                  */
424                 if (dccp_parse_options(sk, NULL, skb))
425                         return 1;
426 
427                 /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
428                 if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
429                         dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
430                             dp->dccps_options_received.dccpor_timestamp_echo));
431 
432                 /* Stop the REQUEST timer */
433                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
434                 WARN_ON(sk->sk_send_head == NULL);
435                 kfree_skb(sk->sk_send_head);
436                 sk->sk_send_head = NULL;
437 
438                 /*
439                  * Set ISR, GSR from packet. ISS was set in dccp_v{4,6}_connect
440                  * and GSS in dccp_transmit_skb(). Setting AWL/AWH and SWL/SWH
441                  * is done as part of activating the feature values below, since
442                  * these settings depend on the local/remote Sequence Window
443                  * features, which were undefined or not confirmed until now.
444                  */
445                 dp->dccps_gsr = dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
446 
447                 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
448 
449                 /*
450                  *    Step 10: Process REQUEST state (second part)
451                  *       If S.state == REQUEST,
452                  *        / * If we get here, P is a valid Response from the
453                  *            server (see Step 4), and we should move to
454                  *            PARTOPEN state. PARTOPEN means send an Ack,
455                  *            don't send Data packets, retransmit Acks
456                  *            periodically, and always include any Init Cookie
457                  *            from the Response * /
458                  *        S.state := PARTOPEN
459                  *        Set PARTOPEN timer
460                  *        Continue with S.state == PARTOPEN
461                  *        / * Step 12 will send the Ack completing the
462                  *            three-way handshake * /
463                  */
464                 dccp_set_state(sk, DCCP_PARTOPEN);
465 
466                 /*
467                  * If feature negotiation was successful, activate features now;
468                  * an activation failure means that this host could not activate
469                  * one ore more features (e.g. insufficient memory), which would
470                  * leave at least one feature in an undefined state.
471                  */
472                 if (dccp_feat_activate_values(sk, &dp->dccps_featneg))
473                         goto unable_to_proceed;
474 
475                 /* Make sure socket is routed, for correct metrics. */
476                 icsk->icsk_af_ops->rebuild_header(sk);
477 
478                 if (!sock_flag(sk, SOCK_DEAD)) {
479                         sk->sk_state_change(sk);
480                         sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
481                 }
482 
483                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
484                     icsk->icsk_accept_queue.rskq_defer_accept) {
485                         /* Save one ACK. Data will be ready after
486                          * several ticks, if write_pending is set.
487                          *
488                          * It may be deleted, but with this feature tcpdumps
489                          * look so _wonderfully_ clever, that I was not able
490                          * to stand against the temptation 8)     --ANK
491                          */
492                         /*
493                          * OK, in DCCP we can as well do a similar trick, its
494                          * even in the draft, but there is no need for us to
495                          * schedule an ack here, as dccp_sendmsg does this for
496                          * us, also stated in the draft. -acme
497                          */
498                         __kfree_skb(skb);
499                         return 0;
500                 }
501                 dccp_send_ack(sk);
502                 return -1;
503         }
504 
505 out_invalid_packet:
506         /* dccp_v4_do_rcv will send a reset */
507         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
508         return 1;
509 
510 unable_to_proceed:
511         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_ABORTED;
512         /*
513          * We mark this socket as no longer usable, so that the loop in
514          * dccp_sendmsg() terminates and the application gets notified.
515          */
516         dccp_set_state(sk, DCCP_CLOSED);
517         sk->sk_err = ECOMM;
518         return 1;
519 }
520 
521 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
522                                                    struct sk_buff *skb,
523                                                    const struct dccp_hdr *dh,
524                                                    const unsigned int len)
525 {
526         struct dccp_sock *dp = dccp_sk(sk);
527         u32 sample = dp->dccps_options_received.dccpor_timestamp_echo;
528         int queued = 0;
529 
530         switch (dh->dccph_type) {
531         case DCCP_PKT_RESET:
532                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
533                 break;
534         case DCCP_PKT_DATA:
535                 if (sk->sk_state == DCCP_RESPOND)
536                         break;
537         case DCCP_PKT_DATAACK:
538         case DCCP_PKT_ACK:
539                 /*
540                  * FIXME: we should be resetting the PARTOPEN (DELACK) timer
541                  * here but only if we haven't used the DELACK timer for
542                  * something else, like sending a delayed ack for a TIMESTAMP
543                  * echo, etc, for now were not clearing it, sending an extra
544                  * ACK when there is nothing else to do in DELACK is not a big
545                  * deal after all.
546                  */
547 
548                 /* Stop the PARTOPEN timer */
549                 if (sk->sk_state == DCCP_PARTOPEN)
550                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
551 
552                 /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
553                 if (likely(sample)) {
554                         long delta = dccp_timestamp() - sample;
555 
556                         dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * delta);
557                 }
558 
559                 dp->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
560                 dccp_set_state(sk, DCCP_OPEN);
561 
562                 if (dh->dccph_type == DCCP_PKT_DATAACK ||
563                     dh->dccph_type == DCCP_PKT_DATA) {
564                         __dccp_rcv_established(sk, skb, dh, len);
565                         queued = 1; /* packet was queued
566                                        (by __dccp_rcv_established) */
567                 }
568                 break;
569         }
570 
571         return queued;
572 }
573 
574 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
575                            struct dccp_hdr *dh, unsigned int len)
576 {
577         struct dccp_sock *dp = dccp_sk(sk);
578         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
579         const int old_state = sk->sk_state;
580         bool acceptable;
581         int queued = 0;
582 
583         /*
584          *  Step 3: Process LISTEN state
585          *
586          *     If S.state == LISTEN,
587          *       If P.type == Request or P contains a valid Init Cookie option,
588          *            (* Must scan the packet's options to check for Init
589          *               Cookies.  Only Init Cookies are processed here,
590          *               however; other options are processed in Step 8.  This
591          *               scan need only be performed if the endpoint uses Init
592          *               Cookies *)
593          *            (* Generate a new socket and switch to that socket *)
594          *            Set S := new socket for this port pair
595          *            S.state = RESPOND
596          *            Choose S.ISS (initial seqno) or set from Init Cookies
597          *            Initialize S.GAR := S.ISS
598          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
599          *            Cookies Continue with S.state == RESPOND
600          *            (* A Response packet will be generated in Step 11 *)
601          *       Otherwise,
602          *            Generate Reset(No Connection) unless P.type == Reset
603          *            Drop packet and return
604          */
605         if (sk->sk_state == DCCP_LISTEN) {
606                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
607                         /* It is possible that we process SYN packets from backlog,
608                          * so we need to make sure to disable BH right there.
609                          */
610                         local_bh_disable();
611                         acceptable = inet_csk(sk)->icsk_af_ops->conn_request(sk, skb) >= 0;
612                         local_bh_enable();
613                         if (!acceptable)
614                                 return 1;
615                         consume_skb(skb);
616                         return 0;
617                 }
618                 if (dh->dccph_type == DCCP_PKT_RESET)
619                         goto discard;
620 
621                 /* Caller (dccp_v4_do_rcv) will send Reset */
622                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
623                 return 1;
624         } else if (sk->sk_state == DCCP_CLOSED) {
625                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
626                 return 1;
627         }
628 
629         /* Step 6: Check sequence numbers (omitted in LISTEN/REQUEST state) */
630         if (sk->sk_state != DCCP_REQUESTING && dccp_check_seqno(sk, skb))
631                 goto discard;
632 
633         /*
634          *   Step 7: Check for unexpected packet types
635          *      If (S.is_server and P.type == Response)
636          *          or (S.is_client and P.type == Request)
637          *          or (S.state == RESPOND and P.type == Data),
638          *        Send Sync packet acknowledging P.seqno
639          *        Drop packet and return
640          */
641         if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
642              dh->dccph_type == DCCP_PKT_RESPONSE) ||
643             (dp->dccps_role == DCCP_ROLE_CLIENT &&
644              dh->dccph_type == DCCP_PKT_REQUEST) ||
645             (sk->sk_state == DCCP_RESPOND && dh->dccph_type == DCCP_PKT_DATA)) {
646                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
647                 goto discard;
648         }
649 
650         /*  Step 8: Process options */
651         if (dccp_parse_options(sk, NULL, skb))
652                 return 1;
653 
654         /*
655          *  Step 9: Process Reset
656          *      If P.type == Reset,
657          *              Tear down connection
658          *              S.state := TIMEWAIT
659          *              Set TIMEWAIT timer
660          *              Drop packet and return
661          */
662         if (dh->dccph_type == DCCP_PKT_RESET) {
663                 dccp_rcv_reset(sk, skb);
664                 return 0;
665         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {       /* Step 13 */
666                 if (dccp_rcv_closereq(sk, skb))
667                         return 0;
668                 goto discard;
669         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {          /* Step 14 */
670                 if (dccp_rcv_close(sk, skb))
671                         return 0;
672                 goto discard;
673         }
674 
675         switch (sk->sk_state) {
676         case DCCP_REQUESTING:
677                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
678                 if (queued >= 0)
679                         return queued;
680 
681                 __kfree_skb(skb);
682                 return 0;
683 
684         case DCCP_PARTOPEN:
685                 /* Step 8: if using Ack Vectors, mark packet acknowledgeable */
686                 dccp_handle_ackvec_processing(sk, skb);
687                 dccp_deliver_input_to_ccids(sk, skb);
688                 /* fall through */
689         case DCCP_RESPOND:
690                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
691                                                                  dh, len);
692                 break;
693         }
694 
695         if (dh->dccph_type == DCCP_PKT_ACK ||
696             dh->dccph_type == DCCP_PKT_DATAACK) {
697                 switch (old_state) {
698                 case DCCP_PARTOPEN:
699                         sk->sk_state_change(sk);
700                         sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
701                         break;
702                 }
703         } else if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
704                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
705                 goto discard;
706         }
707 
708         if (!queued) {
709 discard:
710                 __kfree_skb(skb);
711         }
712         return 0;
713 }
714 
715 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);
716 
717 /**
718  *  dccp_sample_rtt  -  Validate and finalise computation of RTT sample
719  *  @delta:     number of microseconds between packet and acknowledgment
720  *
721  *  The routine is kept generic to work in different contexts. It should be
722  *  called immediately when the ACK used for the RTT sample arrives.
723  */
724 u32 dccp_sample_rtt(struct sock *sk, long delta)
725 {
726         /* dccpor_elapsed_time is either zeroed out or set and > 0 */
727         delta -= dccp_sk(sk)->dccps_options_received.dccpor_elapsed_time * 10;
728 
729         if (unlikely(delta <= 0)) {
730                 DCCP_WARN("unusable RTT sample %ld, using min\n", delta);
731                 return DCCP_SANE_RTT_MIN;
732         }
733         if (unlikely(delta > DCCP_SANE_RTT_MAX)) {
734                 DCCP_WARN("RTT sample %ld too large, using max\n", delta);
735                 return DCCP_SANE_RTT_MAX;
736         }
737 
738         return delta;
739 }
740 

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