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Linux/net/dccp/ipv4.c

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  1 /*
  2  *  net/dccp/ipv4.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/icmp.h>
 15 #include <linux/slab.h>
 16 #include <linux/module.h>
 17 #include <linux/skbuff.h>
 18 #include <linux/random.h>
 19 
 20 #include <net/icmp.h>
 21 #include <net/inet_common.h>
 22 #include <net/inet_hashtables.h>
 23 #include <net/inet_sock.h>
 24 #include <net/protocol.h>
 25 #include <net/sock.h>
 26 #include <net/timewait_sock.h>
 27 #include <net/tcp_states.h>
 28 #include <net/xfrm.h>
 29 #include <net/secure_seq.h>
 30 
 31 #include "ackvec.h"
 32 #include "ccid.h"
 33 #include "dccp.h"
 34 #include "feat.h"
 35 
 36 /*
 37  * The per-net dccp.v4_ctl_sk socket is used for responding to
 38  * the Out-of-the-blue (OOTB) packets. A control sock will be created
 39  * for this socket at the initialization time.
 40  */
 41 
 42 int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 43 {
 44         const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
 45         struct inet_sock *inet = inet_sk(sk);
 46         struct dccp_sock *dp = dccp_sk(sk);
 47         __be16 orig_sport, orig_dport;
 48         __be32 daddr, nexthop;
 49         struct flowi4 *fl4;
 50         struct rtable *rt;
 51         int err;
 52         struct ip_options_rcu *inet_opt;
 53 
 54         dp->dccps_role = DCCP_ROLE_CLIENT;
 55 
 56         if (addr_len < sizeof(struct sockaddr_in))
 57                 return -EINVAL;
 58 
 59         if (usin->sin_family != AF_INET)
 60                 return -EAFNOSUPPORT;
 61 
 62         nexthop = daddr = usin->sin_addr.s_addr;
 63 
 64         inet_opt = rcu_dereference_protected(inet->inet_opt,
 65                                              lockdep_sock_is_held(sk));
 66         if (inet_opt != NULL && inet_opt->opt.srr) {
 67                 if (daddr == 0)
 68                         return -EINVAL;
 69                 nexthop = inet_opt->opt.faddr;
 70         }
 71 
 72         orig_sport = inet->inet_sport;
 73         orig_dport = usin->sin_port;
 74         fl4 = &inet->cork.fl.u.ip4;
 75         rt = ip_route_connect(fl4, nexthop, inet->inet_saddr,
 76                               RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
 77                               IPPROTO_DCCP,
 78                               orig_sport, orig_dport, sk);
 79         if (IS_ERR(rt))
 80                 return PTR_ERR(rt);
 81 
 82         if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
 83                 ip_rt_put(rt);
 84                 return -ENETUNREACH;
 85         }
 86 
 87         if (inet_opt == NULL || !inet_opt->opt.srr)
 88                 daddr = fl4->daddr;
 89 
 90         if (inet->inet_saddr == 0)
 91                 inet->inet_saddr = fl4->saddr;
 92         sk_rcv_saddr_set(sk, inet->inet_saddr);
 93         inet->inet_dport = usin->sin_port;
 94         sk_daddr_set(sk, daddr);
 95 
 96         inet_csk(sk)->icsk_ext_hdr_len = 0;
 97         if (inet_opt)
 98                 inet_csk(sk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
 99         /*
100          * Socket identity is still unknown (sport may be zero).
101          * However we set state to DCCP_REQUESTING and not releasing socket
102          * lock select source port, enter ourselves into the hash tables and
103          * complete initialization after this.
104          */
105         dccp_set_state(sk, DCCP_REQUESTING);
106         err = inet_hash_connect(&dccp_death_row, sk);
107         if (err != 0)
108                 goto failure;
109 
110         rt = ip_route_newports(fl4, rt, orig_sport, orig_dport,
111                                inet->inet_sport, inet->inet_dport, sk);
112         if (IS_ERR(rt)) {
113                 err = PTR_ERR(rt);
114                 rt = NULL;
115                 goto failure;
116         }
117         /* OK, now commit destination to socket.  */
118         sk_setup_caps(sk, &rt->dst);
119 
120         dp->dccps_iss = secure_dccp_sequence_number(inet->inet_saddr,
121                                                     inet->inet_daddr,
122                                                     inet->inet_sport,
123                                                     inet->inet_dport);
124         inet->inet_id = dp->dccps_iss ^ jiffies;
125 
126         err = dccp_connect(sk);
127         rt = NULL;
128         if (err != 0)
129                 goto failure;
130 out:
131         return err;
132 failure:
133         /*
134          * This unhashes the socket and releases the local port, if necessary.
135          */
136         dccp_set_state(sk, DCCP_CLOSED);
137         ip_rt_put(rt);
138         sk->sk_route_caps = 0;
139         inet->inet_dport = 0;
140         goto out;
141 }
142 EXPORT_SYMBOL_GPL(dccp_v4_connect);
143 
144 /*
145  * This routine does path mtu discovery as defined in RFC1191.
146  */
147 static inline void dccp_do_pmtu_discovery(struct sock *sk,
148                                           const struct iphdr *iph,
149                                           u32 mtu)
150 {
151         struct dst_entry *dst;
152         const struct inet_sock *inet = inet_sk(sk);
153         const struct dccp_sock *dp = dccp_sk(sk);
154 
155         /* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
156          * send out by Linux are always < 576bytes so they should go through
157          * unfragmented).
158          */
159         if (sk->sk_state == DCCP_LISTEN)
160                 return;
161 
162         dst = inet_csk_update_pmtu(sk, mtu);
163         if (!dst)
164                 return;
165 
166         /* Something is about to be wrong... Remember soft error
167          * for the case, if this connection will not able to recover.
168          */
169         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
170                 sk->sk_err_soft = EMSGSIZE;
171 
172         mtu = dst_mtu(dst);
173 
174         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
175             ip_sk_accept_pmtu(sk) &&
176             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
177                 dccp_sync_mss(sk, mtu);
178 
179                 /*
180                  * From RFC 4340, sec. 14.1:
181                  *
182                  *      DCCP-Sync packets are the best choice for upward
183                  *      probing, since DCCP-Sync probes do not risk application
184                  *      data loss.
185                  */
186                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
187         } /* else let the usual retransmit timer handle it */
188 }
189 
190 static void dccp_do_redirect(struct sk_buff *skb, struct sock *sk)
191 {
192         struct dst_entry *dst = __sk_dst_check(sk, 0);
193 
194         if (dst)
195                 dst->ops->redirect(dst, sk, skb);
196 }
197 
198 void dccp_req_err(struct sock *sk, u64 seq)
199         {
200         struct request_sock *req = inet_reqsk(sk);
201         struct net *net = sock_net(sk);
202 
203         /*
204          * ICMPs are not backlogged, hence we cannot get an established
205          * socket here.
206          */
207         if (!between48(seq, dccp_rsk(req)->dreq_iss, dccp_rsk(req)->dreq_gss)) {
208                 __NET_INC_STATS(net, LINUX_MIB_OUTOFWINDOWICMPS);
209         } else {
210                 /*
211                  * Still in RESPOND, just remove it silently.
212                  * There is no good way to pass the error to the newly
213                  * created socket, and POSIX does not want network
214                  * errors returned from accept().
215                  */
216                 inet_csk_reqsk_queue_drop(req->rsk_listener, req);
217         }
218         reqsk_put(req);
219 }
220 EXPORT_SYMBOL(dccp_req_err);
221 
222 /*
223  * This routine is called by the ICMP module when it gets some sort of error
224  * condition. If err < 0 then the socket should be closed and the error
225  * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
226  * After adjustment header points to the first 8 bytes of the tcp header. We
227  * need to find the appropriate port.
228  *
229  * The locking strategy used here is very "optimistic". When someone else
230  * accesses the socket the ICMP is just dropped and for some paths there is no
231  * check at all. A more general error queue to queue errors for later handling
232  * is probably better.
233  */
234 static void dccp_v4_err(struct sk_buff *skb, u32 info)
235 {
236         const struct iphdr *iph = (struct iphdr *)skb->data;
237         const u8 offset = iph->ihl << 2;
238         const struct dccp_hdr *dh;
239         struct dccp_sock *dp;
240         struct inet_sock *inet;
241         const int type = icmp_hdr(skb)->type;
242         const int code = icmp_hdr(skb)->code;
243         struct sock *sk;
244         __u64 seq;
245         int err;
246         struct net *net = dev_net(skb->dev);
247 
248         /* Only need dccph_dport & dccph_sport which are the first
249          * 4 bytes in dccp header.
250          * Our caller (icmp_socket_deliver()) already pulled 8 bytes for us.
251          */
252         BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_sport) > 8);
253         BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_dport) > 8);
254         dh = (struct dccp_hdr *)(skb->data + offset);
255 
256         sk = __inet_lookup_established(net, &dccp_hashinfo,
257                                        iph->daddr, dh->dccph_dport,
258                                        iph->saddr, ntohs(dh->dccph_sport),
259                                        inet_iif(skb));
260         if (!sk) {
261                 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
262                 return;
263         }
264 
265         if (sk->sk_state == DCCP_TIME_WAIT) {
266                 inet_twsk_put(inet_twsk(sk));
267                 return;
268         }
269         seq = dccp_hdr_seq(dh);
270         if (sk->sk_state == DCCP_NEW_SYN_RECV)
271                 return dccp_req_err(sk, seq);
272 
273         bh_lock_sock(sk);
274         /* If too many ICMPs get dropped on busy
275          * servers this needs to be solved differently.
276          */
277         if (sock_owned_by_user(sk))
278                 __NET_INC_STATS(net, LINUX_MIB_LOCKDROPPEDICMPS);
279 
280         if (sk->sk_state == DCCP_CLOSED)
281                 goto out;
282 
283         dp = dccp_sk(sk);
284         if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
285             !between48(seq, dp->dccps_awl, dp->dccps_awh)) {
286                 __NET_INC_STATS(net, LINUX_MIB_OUTOFWINDOWICMPS);
287                 goto out;
288         }
289 
290         switch (type) {
291         case ICMP_REDIRECT:
292                 if (!sock_owned_by_user(sk))
293                         dccp_do_redirect(skb, sk);
294                 goto out;
295         case ICMP_SOURCE_QUENCH:
296                 /* Just silently ignore these. */
297                 goto out;
298         case ICMP_PARAMETERPROB:
299                 err = EPROTO;
300                 break;
301         case ICMP_DEST_UNREACH:
302                 if (code > NR_ICMP_UNREACH)
303                         goto out;
304 
305                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
306                         if (!sock_owned_by_user(sk))
307                                 dccp_do_pmtu_discovery(sk, iph, info);
308                         goto out;
309                 }
310 
311                 err = icmp_err_convert[code].errno;
312                 break;
313         case ICMP_TIME_EXCEEDED:
314                 err = EHOSTUNREACH;
315                 break;
316         default:
317                 goto out;
318         }
319 
320         switch (sk->sk_state) {
321         case DCCP_REQUESTING:
322         case DCCP_RESPOND:
323                 if (!sock_owned_by_user(sk)) {
324                         __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
325                         sk->sk_err = err;
326 
327                         sk->sk_error_report(sk);
328 
329                         dccp_done(sk);
330                 } else
331                         sk->sk_err_soft = err;
332                 goto out;
333         }
334 
335         /* If we've already connected we will keep trying
336          * until we time out, or the user gives up.
337          *
338          * rfc1122 4.2.3.9 allows to consider as hard errors
339          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
340          * but it is obsoleted by pmtu discovery).
341          *
342          * Note, that in modern internet, where routing is unreliable
343          * and in each dark corner broken firewalls sit, sending random
344          * errors ordered by their masters even this two messages finally lose
345          * their original sense (even Linux sends invalid PORT_UNREACHs)
346          *
347          * Now we are in compliance with RFCs.
348          *                                                      --ANK (980905)
349          */
350 
351         inet = inet_sk(sk);
352         if (!sock_owned_by_user(sk) && inet->recverr) {
353                 sk->sk_err = err;
354                 sk->sk_error_report(sk);
355         } else /* Only an error on timeout */
356                 sk->sk_err_soft = err;
357 out:
358         bh_unlock_sock(sk);
359         sock_put(sk);
360 }
361 
362 static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
363                                       __be32 src, __be32 dst)
364 {
365         return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
366 }
367 
368 void dccp_v4_send_check(struct sock *sk, struct sk_buff *skb)
369 {
370         const struct inet_sock *inet = inet_sk(sk);
371         struct dccp_hdr *dh = dccp_hdr(skb);
372 
373         dccp_csum_outgoing(skb);
374         dh->dccph_checksum = dccp_v4_csum_finish(skb,
375                                                  inet->inet_saddr,
376                                                  inet->inet_daddr);
377 }
378 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
379 
380 static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
381 {
382         return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
383                                            ip_hdr(skb)->saddr,
384                                            dccp_hdr(skb)->dccph_dport,
385                                            dccp_hdr(skb)->dccph_sport);
386 }
387 
388 /*
389  * The three way handshake has completed - we got a valid ACK or DATAACK -
390  * now create the new socket.
391  *
392  * This is the equivalent of TCP's tcp_v4_syn_recv_sock
393  */
394 struct sock *dccp_v4_request_recv_sock(const struct sock *sk,
395                                        struct sk_buff *skb,
396                                        struct request_sock *req,
397                                        struct dst_entry *dst,
398                                        struct request_sock *req_unhash,
399                                        bool *own_req)
400 {
401         struct inet_request_sock *ireq;
402         struct inet_sock *newinet;
403         struct sock *newsk;
404 
405         if (sk_acceptq_is_full(sk))
406                 goto exit_overflow;
407 
408         newsk = dccp_create_openreq_child(sk, req, skb);
409         if (newsk == NULL)
410                 goto exit_nonewsk;
411 
412         newinet            = inet_sk(newsk);
413         ireq               = inet_rsk(req);
414         sk_daddr_set(newsk, ireq->ir_rmt_addr);
415         sk_rcv_saddr_set(newsk, ireq->ir_loc_addr);
416         newinet->inet_saddr     = ireq->ir_loc_addr;
417         newinet->inet_opt       = ireq->opt;
418         ireq->opt          = NULL;
419         newinet->mc_index  = inet_iif(skb);
420         newinet->mc_ttl    = ip_hdr(skb)->ttl;
421         newinet->inet_id   = jiffies;
422 
423         if (dst == NULL && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
424                 goto put_and_exit;
425 
426         sk_setup_caps(newsk, dst);
427 
428         dccp_sync_mss(newsk, dst_mtu(dst));
429 
430         if (__inet_inherit_port(sk, newsk) < 0)
431                 goto put_and_exit;
432         *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash));
433 
434         return newsk;
435 
436 exit_overflow:
437         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
438 exit_nonewsk:
439         dst_release(dst);
440 exit:
441         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
442         return NULL;
443 put_and_exit:
444         inet_csk_prepare_forced_close(newsk);
445         dccp_done(newsk);
446         goto exit;
447 }
448 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
449 
450 static struct dst_entry* dccp_v4_route_skb(struct net *net, struct sock *sk,
451                                            struct sk_buff *skb)
452 {
453         struct rtable *rt;
454         const struct iphdr *iph = ip_hdr(skb);
455         struct flowi4 fl4 = {
456                 .flowi4_oif = inet_iif(skb),
457                 .daddr = iph->saddr,
458                 .saddr = iph->daddr,
459                 .flowi4_tos = RT_CONN_FLAGS(sk),
460                 .flowi4_proto = sk->sk_protocol,
461                 .fl4_sport = dccp_hdr(skb)->dccph_dport,
462                 .fl4_dport = dccp_hdr(skb)->dccph_sport,
463         };
464 
465         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
466         rt = ip_route_output_flow(net, &fl4, sk);
467         if (IS_ERR(rt)) {
468                 IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
469                 return NULL;
470         }
471 
472         return &rt->dst;
473 }
474 
475 static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req)
476 {
477         int err = -1;
478         struct sk_buff *skb;
479         struct dst_entry *dst;
480         struct flowi4 fl4;
481 
482         dst = inet_csk_route_req(sk, &fl4, req);
483         if (dst == NULL)
484                 goto out;
485 
486         skb = dccp_make_response(sk, dst, req);
487         if (skb != NULL) {
488                 const struct inet_request_sock *ireq = inet_rsk(req);
489                 struct dccp_hdr *dh = dccp_hdr(skb);
490 
491                 dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->ir_loc_addr,
492                                                               ireq->ir_rmt_addr);
493                 err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
494                                             ireq->ir_rmt_addr,
495                                             ireq->opt);
496                 err = net_xmit_eval(err);
497         }
498 
499 out:
500         dst_release(dst);
501         return err;
502 }
503 
504 static void dccp_v4_ctl_send_reset(const struct sock *sk, struct sk_buff *rxskb)
505 {
506         int err;
507         const struct iphdr *rxiph;
508         struct sk_buff *skb;
509         struct dst_entry *dst;
510         struct net *net = dev_net(skb_dst(rxskb)->dev);
511         struct sock *ctl_sk = net->dccp.v4_ctl_sk;
512 
513         /* Never send a reset in response to a reset. */
514         if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
515                 return;
516 
517         if (skb_rtable(rxskb)->rt_type != RTN_LOCAL)
518                 return;
519 
520         dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
521         if (dst == NULL)
522                 return;
523 
524         skb = dccp_ctl_make_reset(ctl_sk, rxskb);
525         if (skb == NULL)
526                 goto out;
527 
528         rxiph = ip_hdr(rxskb);
529         dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
530                                                                  rxiph->daddr);
531         skb_dst_set(skb, dst_clone(dst));
532 
533         local_bh_disable();
534         bh_lock_sock(ctl_sk);
535         err = ip_build_and_send_pkt(skb, ctl_sk,
536                                     rxiph->daddr, rxiph->saddr, NULL);
537         bh_unlock_sock(ctl_sk);
538 
539         if (net_xmit_eval(err) == 0) {
540                 __DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
541                 __DCCP_INC_STATS(DCCP_MIB_OUTRSTS);
542         }
543         local_bh_enable();
544 out:
545         dst_release(dst);
546 }
547 
548 static void dccp_v4_reqsk_destructor(struct request_sock *req)
549 {
550         dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
551         kfree(inet_rsk(req)->opt);
552 }
553 
554 void dccp_syn_ack_timeout(const struct request_sock *req)
555 {
556 }
557 EXPORT_SYMBOL(dccp_syn_ack_timeout);
558 
559 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
560         .family         = PF_INET,
561         .obj_size       = sizeof(struct dccp_request_sock),
562         .rtx_syn_ack    = dccp_v4_send_response,
563         .send_ack       = dccp_reqsk_send_ack,
564         .destructor     = dccp_v4_reqsk_destructor,
565         .send_reset     = dccp_v4_ctl_send_reset,
566         .syn_ack_timeout = dccp_syn_ack_timeout,
567 };
568 
569 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
570 {
571         struct inet_request_sock *ireq;
572         struct request_sock *req;
573         struct dccp_request_sock *dreq;
574         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
575         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
576 
577         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
578         if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
579                 return 0;       /* discard, don't send a reset here */
580 
581         if (dccp_bad_service_code(sk, service)) {
582                 dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
583                 goto drop;
584         }
585         /*
586          * TW buckets are converted to open requests without
587          * limitations, they conserve resources and peer is
588          * evidently real one.
589          */
590         dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
591         if (inet_csk_reqsk_queue_is_full(sk))
592                 goto drop;
593 
594         if (sk_acceptq_is_full(sk))
595                 goto drop;
596 
597         req = inet_reqsk_alloc(&dccp_request_sock_ops, sk, true);
598         if (req == NULL)
599                 goto drop;
600 
601         if (dccp_reqsk_init(req, dccp_sk(sk), skb))
602                 goto drop_and_free;
603 
604         dreq = dccp_rsk(req);
605         if (dccp_parse_options(sk, dreq, skb))
606                 goto drop_and_free;
607 
608         if (security_inet_conn_request(sk, skb, req))
609                 goto drop_and_free;
610 
611         ireq = inet_rsk(req);
612         sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
613         sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
614         ireq->ireq_family = AF_INET;
615         ireq->ir_iif = sk->sk_bound_dev_if;
616 
617         /*
618          * Step 3: Process LISTEN state
619          *
620          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
621          *
622          * Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
623          */
624         dreq->dreq_isr     = dcb->dccpd_seq;
625         dreq->dreq_gsr     = dreq->dreq_isr;
626         dreq->dreq_iss     = dccp_v4_init_sequence(skb);
627         dreq->dreq_gss     = dreq->dreq_iss;
628         dreq->dreq_service = service;
629 
630         if (dccp_v4_send_response(sk, req))
631                 goto drop_and_free;
632 
633         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
634         return 0;
635 
636 drop_and_free:
637         reqsk_free(req);
638 drop:
639         __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
640         return -1;
641 }
642 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
643 
644 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
645 {
646         struct dccp_hdr *dh = dccp_hdr(skb);
647 
648         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
649                 if (dccp_rcv_established(sk, skb, dh, skb->len))
650                         goto reset;
651                 return 0;
652         }
653 
654         /*
655          *  Step 3: Process LISTEN state
656          *       If P.type == Request or P contains a valid Init Cookie option,
657          *            (* Must scan the packet's options to check for Init
658          *               Cookies.  Only Init Cookies are processed here,
659          *               however; other options are processed in Step 8.  This
660          *               scan need only be performed if the endpoint uses Init
661          *               Cookies *)
662          *            (* Generate a new socket and switch to that socket *)
663          *            Set S := new socket for this port pair
664          *            S.state = RESPOND
665          *            Choose S.ISS (initial seqno) or set from Init Cookies
666          *            Initialize S.GAR := S.ISS
667          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
668          *            Continue with S.state == RESPOND
669          *            (* A Response packet will be generated in Step 11 *)
670          *       Otherwise,
671          *            Generate Reset(No Connection) unless P.type == Reset
672          *            Drop packet and return
673          *
674          * NOTE: the check for the packet types is done in
675          *       dccp_rcv_state_process
676          */
677 
678         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
679                 goto reset;
680         return 0;
681 
682 reset:
683         dccp_v4_ctl_send_reset(sk, skb);
684         kfree_skb(skb);
685         return 0;
686 }
687 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
688 
689 /**
690  *      dccp_invalid_packet  -  check for malformed packets
691  *      Implements RFC 4340, 8.5:  Step 1: Check header basics
692  *      Packets that fail these checks are ignored and do not receive Resets.
693  */
694 int dccp_invalid_packet(struct sk_buff *skb)
695 {
696         const struct dccp_hdr *dh;
697         unsigned int cscov;
698         u8 dccph_doff;
699 
700         if (skb->pkt_type != PACKET_HOST)
701                 return 1;
702 
703         /* If the packet is shorter than 12 bytes, drop packet and return */
704         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
705                 DCCP_WARN("pskb_may_pull failed\n");
706                 return 1;
707         }
708 
709         dh = dccp_hdr(skb);
710 
711         /* If P.type is not understood, drop packet and return */
712         if (dh->dccph_type >= DCCP_PKT_INVALID) {
713                 DCCP_WARN("invalid packet type\n");
714                 return 1;
715         }
716 
717         /*
718          * If P.Data Offset is too small for packet type, drop packet and return
719          */
720         dccph_doff = dh->dccph_doff;
721         if (dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
722                 DCCP_WARN("P.Data Offset(%u) too small\n", dccph_doff);
723                 return 1;
724         }
725         /*
726          * If P.Data Offset is too too large for packet, drop packet and return
727          */
728         if (!pskb_may_pull(skb, dccph_doff * sizeof(u32))) {
729                 DCCP_WARN("P.Data Offset(%u) too large\n", dccph_doff);
730                 return 1;
731         }
732         dh = dccp_hdr(skb);
733         /*
734          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
735          * has short sequence numbers), drop packet and return
736          */
737         if ((dh->dccph_type < DCCP_PKT_DATA    ||
738             dh->dccph_type > DCCP_PKT_DATAACK) && dh->dccph_x == 0)  {
739                 DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
740                           dccp_packet_name(dh->dccph_type));
741                 return 1;
742         }
743 
744         /*
745          * If P.CsCov is too large for the packet size, drop packet and return.
746          * This must come _before_ checksumming (not as RFC 4340 suggests).
747          */
748         cscov = dccp_csum_coverage(skb);
749         if (cscov > skb->len) {
750                 DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
751                           dh->dccph_cscov, skb->len);
752                 return 1;
753         }
754 
755         /* If header checksum is incorrect, drop packet and return.
756          * (This step is completed in the AF-dependent functions.) */
757         skb->csum = skb_checksum(skb, 0, cscov, 0);
758 
759         return 0;
760 }
761 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
762 
763 /* this is called when real data arrives */
764 static int dccp_v4_rcv(struct sk_buff *skb)
765 {
766         const struct dccp_hdr *dh;
767         const struct iphdr *iph;
768         bool refcounted;
769         struct sock *sk;
770         int min_cov;
771 
772         /* Step 1: Check header basics */
773 
774         if (dccp_invalid_packet(skb))
775                 goto discard_it;
776 
777         iph = ip_hdr(skb);
778         /* Step 1: If header checksum is incorrect, drop packet and return */
779         if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
780                 DCCP_WARN("dropped packet with invalid checksum\n");
781                 goto discard_it;
782         }
783 
784         dh = dccp_hdr(skb);
785 
786         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
787         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
788 
789         dccp_pr_debug("%8.8s src=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
790                       dccp_packet_name(dh->dccph_type),
791                       &iph->saddr, ntohs(dh->dccph_sport),
792                       &iph->daddr, ntohs(dh->dccph_dport),
793                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
794 
795         if (dccp_packet_without_ack(skb)) {
796                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
797                 dccp_pr_debug_cat("\n");
798         } else {
799                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
800                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
801                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
802         }
803 
804 lookup:
805         sk = __inet_lookup_skb(&dccp_hashinfo, skb, __dccp_hdr_len(dh),
806                                dh->dccph_sport, dh->dccph_dport, &refcounted);
807         if (!sk) {
808                 dccp_pr_debug("failed to look up flow ID in table and "
809                               "get corresponding socket\n");
810                 goto no_dccp_socket;
811         }
812 
813         /*
814          * Step 2:
815          *      ... or S.state == TIMEWAIT,
816          *              Generate Reset(No Connection) unless P.type == Reset
817          *              Drop packet and return
818          */
819         if (sk->sk_state == DCCP_TIME_WAIT) {
820                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
821                 inet_twsk_put(inet_twsk(sk));
822                 goto no_dccp_socket;
823         }
824 
825         if (sk->sk_state == DCCP_NEW_SYN_RECV) {
826                 struct request_sock *req = inet_reqsk(sk);
827                 struct sock *nsk;
828 
829                 sk = req->rsk_listener;
830                 if (unlikely(sk->sk_state != DCCP_LISTEN)) {
831                         inet_csk_reqsk_queue_drop_and_put(sk, req);
832                         goto lookup;
833                 }
834                 sock_hold(sk);
835                 refcounted = true;
836                 nsk = dccp_check_req(sk, skb, req);
837                 if (!nsk) {
838                         reqsk_put(req);
839                         goto discard_and_relse;
840                 }
841                 if (nsk == sk) {
842                         reqsk_put(req);
843                 } else if (dccp_child_process(sk, nsk, skb)) {
844                         dccp_v4_ctl_send_reset(sk, skb);
845                         goto discard_and_relse;
846                 } else {
847                         sock_put(sk);
848                         return 0;
849                 }
850         }
851         /*
852          * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
853          *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
854          *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
855          */
856         min_cov = dccp_sk(sk)->dccps_pcrlen;
857         if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
858                 dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
859                               dh->dccph_cscov, min_cov);
860                 /* FIXME: "Such packets SHOULD be reported using Data Dropped
861                  *         options (Section 11.7) with Drop Code 0, Protocol
862                  *         Constraints."                                     */
863                 goto discard_and_relse;
864         }
865 
866         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
867                 goto discard_and_relse;
868         nf_reset(skb);
869 
870         return __sk_receive_skb(sk, skb, 1, dh->dccph_doff * 4, refcounted);
871 
872 no_dccp_socket:
873         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
874                 goto discard_it;
875         /*
876          * Step 2:
877          *      If no socket ...
878          *              Generate Reset(No Connection) unless P.type == Reset
879          *              Drop packet and return
880          */
881         if (dh->dccph_type != DCCP_PKT_RESET) {
882                 DCCP_SKB_CB(skb)->dccpd_reset_code =
883                                         DCCP_RESET_CODE_NO_CONNECTION;
884                 dccp_v4_ctl_send_reset(sk, skb);
885         }
886 
887 discard_it:
888         kfree_skb(skb);
889         return 0;
890 
891 discard_and_relse:
892         if (refcounted)
893                 sock_put(sk);
894         goto discard_it;
895 }
896 
897 static const struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
898         .queue_xmit        = ip_queue_xmit,
899         .send_check        = dccp_v4_send_check,
900         .rebuild_header    = inet_sk_rebuild_header,
901         .conn_request      = dccp_v4_conn_request,
902         .syn_recv_sock     = dccp_v4_request_recv_sock,
903         .net_header_len    = sizeof(struct iphdr),
904         .setsockopt        = ip_setsockopt,
905         .getsockopt        = ip_getsockopt,
906         .addr2sockaddr     = inet_csk_addr2sockaddr,
907         .sockaddr_len      = sizeof(struct sockaddr_in),
908         .bind_conflict     = inet_csk_bind_conflict,
909 #ifdef CONFIG_COMPAT
910         .compat_setsockopt = compat_ip_setsockopt,
911         .compat_getsockopt = compat_ip_getsockopt,
912 #endif
913 };
914 
915 static int dccp_v4_init_sock(struct sock *sk)
916 {
917         static __u8 dccp_v4_ctl_sock_initialized;
918         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
919 
920         if (err == 0) {
921                 if (unlikely(!dccp_v4_ctl_sock_initialized))
922                         dccp_v4_ctl_sock_initialized = 1;
923                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
924         }
925 
926         return err;
927 }
928 
929 static struct timewait_sock_ops dccp_timewait_sock_ops = {
930         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
931 };
932 
933 static struct proto dccp_v4_prot = {
934         .name                   = "DCCP",
935         .owner                  = THIS_MODULE,
936         .close                  = dccp_close,
937         .connect                = dccp_v4_connect,
938         .disconnect             = dccp_disconnect,
939         .ioctl                  = dccp_ioctl,
940         .init                   = dccp_v4_init_sock,
941         .setsockopt             = dccp_setsockopt,
942         .getsockopt             = dccp_getsockopt,
943         .sendmsg                = dccp_sendmsg,
944         .recvmsg                = dccp_recvmsg,
945         .backlog_rcv            = dccp_v4_do_rcv,
946         .hash                   = inet_hash,
947         .unhash                 = inet_unhash,
948         .accept                 = inet_csk_accept,
949         .get_port               = inet_csk_get_port,
950         .shutdown               = dccp_shutdown,
951         .destroy                = dccp_destroy_sock,
952         .orphan_count           = &dccp_orphan_count,
953         .max_header             = MAX_DCCP_HEADER,
954         .obj_size               = sizeof(struct dccp_sock),
955         .slab_flags             = SLAB_DESTROY_BY_RCU,
956         .rsk_prot               = &dccp_request_sock_ops,
957         .twsk_prot              = &dccp_timewait_sock_ops,
958         .h.hashinfo             = &dccp_hashinfo,
959 #ifdef CONFIG_COMPAT
960         .compat_setsockopt      = compat_dccp_setsockopt,
961         .compat_getsockopt      = compat_dccp_getsockopt,
962 #endif
963 };
964 
965 static const struct net_protocol dccp_v4_protocol = {
966         .handler        = dccp_v4_rcv,
967         .err_handler    = dccp_v4_err,
968         .no_policy      = 1,
969         .netns_ok       = 1,
970         .icmp_strict_tag_validation = 1,
971 };
972 
973 static const struct proto_ops inet_dccp_ops = {
974         .family            = PF_INET,
975         .owner             = THIS_MODULE,
976         .release           = inet_release,
977         .bind              = inet_bind,
978         .connect           = inet_stream_connect,
979         .socketpair        = sock_no_socketpair,
980         .accept            = inet_accept,
981         .getname           = inet_getname,
982         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
983         .poll              = dccp_poll,
984         .ioctl             = inet_ioctl,
985         /* FIXME: work on inet_listen to rename it to sock_common_listen */
986         .listen            = inet_dccp_listen,
987         .shutdown          = inet_shutdown,
988         .setsockopt        = sock_common_setsockopt,
989         .getsockopt        = sock_common_getsockopt,
990         .sendmsg           = inet_sendmsg,
991         .recvmsg           = sock_common_recvmsg,
992         .mmap              = sock_no_mmap,
993         .sendpage          = sock_no_sendpage,
994 #ifdef CONFIG_COMPAT
995         .compat_setsockopt = compat_sock_common_setsockopt,
996         .compat_getsockopt = compat_sock_common_getsockopt,
997 #endif
998 };
999 
1000 static struct inet_protosw dccp_v4_protosw = {
1001         .type           = SOCK_DCCP,
1002         .protocol       = IPPROTO_DCCP,
1003         .prot           = &dccp_v4_prot,
1004         .ops            = &inet_dccp_ops,
1005         .flags          = INET_PROTOSW_ICSK,
1006 };
1007 
1008 static int __net_init dccp_v4_init_net(struct net *net)
1009 {
1010         if (dccp_hashinfo.bhash == NULL)
1011                 return -ESOCKTNOSUPPORT;
1012 
1013         return inet_ctl_sock_create(&net->dccp.v4_ctl_sk, PF_INET,
1014                                     SOCK_DCCP, IPPROTO_DCCP, net);
1015 }
1016 
1017 static void __net_exit dccp_v4_exit_net(struct net *net)
1018 {
1019         inet_ctl_sock_destroy(net->dccp.v4_ctl_sk);
1020 }
1021 
1022 static struct pernet_operations dccp_v4_ops = {
1023         .init   = dccp_v4_init_net,
1024         .exit   = dccp_v4_exit_net,
1025 };
1026 
1027 static int __init dccp_v4_init(void)
1028 {
1029         int err = proto_register(&dccp_v4_prot, 1);
1030 
1031         if (err != 0)
1032                 goto out;
1033 
1034         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1035         if (err != 0)
1036                 goto out_proto_unregister;
1037 
1038         inet_register_protosw(&dccp_v4_protosw);
1039 
1040         err = register_pernet_subsys(&dccp_v4_ops);
1041         if (err)
1042                 goto out_destroy_ctl_sock;
1043 out:
1044         return err;
1045 out_destroy_ctl_sock:
1046         inet_unregister_protosw(&dccp_v4_protosw);
1047         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1048 out_proto_unregister:
1049         proto_unregister(&dccp_v4_prot);
1050         goto out;
1051 }
1052 
1053 static void __exit dccp_v4_exit(void)
1054 {
1055         unregister_pernet_subsys(&dccp_v4_ops);
1056         inet_unregister_protosw(&dccp_v4_protosw);
1057         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1058         proto_unregister(&dccp_v4_prot);
1059 }
1060 
1061 module_init(dccp_v4_init);
1062 module_exit(dccp_v4_exit);
1063 
1064 /*
1065  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1066  * values directly, Also cover the case where the protocol is not specified,
1067  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1068  */
1069 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
1070 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
1071 MODULE_LICENSE("GPL");
1072 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1073 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");
1074 

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