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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         RCU_INIT_POINTER(newinet->inet_opt, rcu_dereference(ireq->ireq_opt));
418         newinet->mc_index  = inet_iif(skb);
419         newinet->mc_ttl    = ip_hdr(skb)->ttl;
420         newinet->inet_id   = jiffies;
421 
422         if (dst == NULL && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
423                 goto put_and_exit;
424 
425         sk_setup_caps(newsk, dst);
426 
427         dccp_sync_mss(newsk, dst_mtu(dst));
428 
429         if (__inet_inherit_port(sk, newsk) < 0)
430                 goto put_and_exit;
431         *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash));
432         if (*own_req)
433                 ireq->ireq_opt = NULL;
434         else
435                 newinet->inet_opt = NULL;
436         return newsk;
437 
438 exit_overflow:
439         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
440 exit_nonewsk:
441         dst_release(dst);
442 exit:
443         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
444         return NULL;
445 put_and_exit:
446         newinet->inet_opt = NULL;
447         inet_csk_prepare_forced_close(newsk);
448         dccp_done(newsk);
449         goto exit;
450 }
451 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
452 
453 static struct dst_entry* dccp_v4_route_skb(struct net *net, struct sock *sk,
454                                            struct sk_buff *skb)
455 {
456         struct rtable *rt;
457         const struct iphdr *iph = ip_hdr(skb);
458         struct flowi4 fl4 = {
459                 .flowi4_oif = inet_iif(skb),
460                 .daddr = iph->saddr,
461                 .saddr = iph->daddr,
462                 .flowi4_tos = RT_CONN_FLAGS(sk),
463                 .flowi4_proto = sk->sk_protocol,
464                 .fl4_sport = dccp_hdr(skb)->dccph_dport,
465                 .fl4_dport = dccp_hdr(skb)->dccph_sport,
466         };
467 
468         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
469         rt = ip_route_output_flow(net, &fl4, sk);
470         if (IS_ERR(rt)) {
471                 IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
472                 return NULL;
473         }
474 
475         return &rt->dst;
476 }
477 
478 static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req)
479 {
480         int err = -1;
481         struct sk_buff *skb;
482         struct dst_entry *dst;
483         struct flowi4 fl4;
484 
485         dst = inet_csk_route_req(sk, &fl4, req);
486         if (dst == NULL)
487                 goto out;
488 
489         skb = dccp_make_response(sk, dst, req);
490         if (skb != NULL) {
491                 const struct inet_request_sock *ireq = inet_rsk(req);
492                 struct dccp_hdr *dh = dccp_hdr(skb);
493 
494                 dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->ir_loc_addr,
495                                                               ireq->ir_rmt_addr);
496                 err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
497                                             ireq->ir_rmt_addr,
498                                             ireq_opt_deref(ireq));
499                 err = net_xmit_eval(err);
500         }
501 
502 out:
503         dst_release(dst);
504         return err;
505 }
506 
507 static void dccp_v4_ctl_send_reset(const struct sock *sk, struct sk_buff *rxskb)
508 {
509         int err;
510         const struct iphdr *rxiph;
511         struct sk_buff *skb;
512         struct dst_entry *dst;
513         struct net *net = dev_net(skb_dst(rxskb)->dev);
514         struct sock *ctl_sk = net->dccp.v4_ctl_sk;
515 
516         /* Never send a reset in response to a reset. */
517         if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
518                 return;
519 
520         if (skb_rtable(rxskb)->rt_type != RTN_LOCAL)
521                 return;
522 
523         dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
524         if (dst == NULL)
525                 return;
526 
527         skb = dccp_ctl_make_reset(ctl_sk, rxskb);
528         if (skb == NULL)
529                 goto out;
530 
531         rxiph = ip_hdr(rxskb);
532         dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
533                                                                  rxiph->daddr);
534         skb_dst_set(skb, dst_clone(dst));
535 
536         local_bh_disable();
537         bh_lock_sock(ctl_sk);
538         err = ip_build_and_send_pkt(skb, ctl_sk,
539                                     rxiph->daddr, rxiph->saddr, NULL);
540         bh_unlock_sock(ctl_sk);
541 
542         if (net_xmit_eval(err) == 0) {
543                 __DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
544                 __DCCP_INC_STATS(DCCP_MIB_OUTRSTS);
545         }
546         local_bh_enable();
547 out:
548         dst_release(dst);
549 }
550 
551 static void dccp_v4_reqsk_destructor(struct request_sock *req)
552 {
553         dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
554         kfree(rcu_dereference_protected(inet_rsk(req)->ireq_opt, 1));
555 }
556 
557 void dccp_syn_ack_timeout(const struct request_sock *req)
558 {
559 }
560 EXPORT_SYMBOL(dccp_syn_ack_timeout);
561 
562 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
563         .family         = PF_INET,
564         .obj_size       = sizeof(struct dccp_request_sock),
565         .rtx_syn_ack    = dccp_v4_send_response,
566         .send_ack       = dccp_reqsk_send_ack,
567         .destructor     = dccp_v4_reqsk_destructor,
568         .send_reset     = dccp_v4_ctl_send_reset,
569         .syn_ack_timeout = dccp_syn_ack_timeout,
570 };
571 
572 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
573 {
574         struct inet_request_sock *ireq;
575         struct request_sock *req;
576         struct dccp_request_sock *dreq;
577         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
578         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
579 
580         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
581         if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
582                 return 0;       /* discard, don't send a reset here */
583 
584         if (dccp_bad_service_code(sk, service)) {
585                 dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
586                 goto drop;
587         }
588         /*
589          * TW buckets are converted to open requests without
590          * limitations, they conserve resources and peer is
591          * evidently real one.
592          */
593         dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
594         if (inet_csk_reqsk_queue_is_full(sk))
595                 goto drop;
596 
597         if (sk_acceptq_is_full(sk))
598                 goto drop;
599 
600         req = inet_reqsk_alloc(&dccp_request_sock_ops, sk, true);
601         if (req == NULL)
602                 goto drop;
603 
604         if (dccp_reqsk_init(req, dccp_sk(sk), skb))
605                 goto drop_and_free;
606 
607         dreq = dccp_rsk(req);
608         if (dccp_parse_options(sk, dreq, skb))
609                 goto drop_and_free;
610 
611         if (security_inet_conn_request(sk, skb, req))
612                 goto drop_and_free;
613 
614         ireq = inet_rsk(req);
615         sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
616         sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
617         ireq->ireq_family = AF_INET;
618         ireq->ir_iif = sk->sk_bound_dev_if;
619 
620         /*
621          * Step 3: Process LISTEN state
622          *
623          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
624          *
625          * Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
626          */
627         dreq->dreq_isr     = dcb->dccpd_seq;
628         dreq->dreq_gsr     = dreq->dreq_isr;
629         dreq->dreq_iss     = dccp_v4_init_sequence(skb);
630         dreq->dreq_gss     = dreq->dreq_iss;
631         dreq->dreq_service = service;
632 
633         if (dccp_v4_send_response(sk, req))
634                 goto drop_and_free;
635 
636         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
637         reqsk_put(req);
638         return 0;
639 
640 drop_and_free:
641         reqsk_free(req);
642 drop:
643         __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
644         return -1;
645 }
646 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
647 
648 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
649 {
650         struct dccp_hdr *dh = dccp_hdr(skb);
651 
652         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
653                 if (dccp_rcv_established(sk, skb, dh, skb->len))
654                         goto reset;
655                 return 0;
656         }
657 
658         /*
659          *  Step 3: Process LISTEN state
660          *       If P.type == Request or P contains a valid Init Cookie option,
661          *            (* Must scan the packet's options to check for Init
662          *               Cookies.  Only Init Cookies are processed here,
663          *               however; other options are processed in Step 8.  This
664          *               scan need only be performed if the endpoint uses Init
665          *               Cookies *)
666          *            (* Generate a new socket and switch to that socket *)
667          *            Set S := new socket for this port pair
668          *            S.state = RESPOND
669          *            Choose S.ISS (initial seqno) or set from Init Cookies
670          *            Initialize S.GAR := S.ISS
671          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
672          *            Continue with S.state == RESPOND
673          *            (* A Response packet will be generated in Step 11 *)
674          *       Otherwise,
675          *            Generate Reset(No Connection) unless P.type == Reset
676          *            Drop packet and return
677          *
678          * NOTE: the check for the packet types is done in
679          *       dccp_rcv_state_process
680          */
681 
682         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
683                 goto reset;
684         return 0;
685 
686 reset:
687         dccp_v4_ctl_send_reset(sk, skb);
688         kfree_skb(skb);
689         return 0;
690 }
691 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
692 
693 /**
694  *      dccp_invalid_packet  -  check for malformed packets
695  *      Implements RFC 4340, 8.5:  Step 1: Check header basics
696  *      Packets that fail these checks are ignored and do not receive Resets.
697  */
698 int dccp_invalid_packet(struct sk_buff *skb)
699 {
700         const struct dccp_hdr *dh;
701         unsigned int cscov;
702         u8 dccph_doff;
703 
704         if (skb->pkt_type != PACKET_HOST)
705                 return 1;
706 
707         /* If the packet is shorter than 12 bytes, drop packet and return */
708         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
709                 DCCP_WARN("pskb_may_pull failed\n");
710                 return 1;
711         }
712 
713         dh = dccp_hdr(skb);
714 
715         /* If P.type is not understood, drop packet and return */
716         if (dh->dccph_type >= DCCP_PKT_INVALID) {
717                 DCCP_WARN("invalid packet type\n");
718                 return 1;
719         }
720 
721         /*
722          * If P.Data Offset is too small for packet type, drop packet and return
723          */
724         dccph_doff = dh->dccph_doff;
725         if (dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
726                 DCCP_WARN("P.Data Offset(%u) too small\n", dccph_doff);
727                 return 1;
728         }
729         /*
730          * If P.Data Offset is too too large for packet, drop packet and return
731          */
732         if (!pskb_may_pull(skb, dccph_doff * sizeof(u32))) {
733                 DCCP_WARN("P.Data Offset(%u) too large\n", dccph_doff);
734                 return 1;
735         }
736         dh = dccp_hdr(skb);
737         /*
738          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
739          * has short sequence numbers), drop packet and return
740          */
741         if ((dh->dccph_type < DCCP_PKT_DATA    ||
742             dh->dccph_type > DCCP_PKT_DATAACK) && dh->dccph_x == 0)  {
743                 DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
744                           dccp_packet_name(dh->dccph_type));
745                 return 1;
746         }
747 
748         /*
749          * If P.CsCov is too large for the packet size, drop packet and return.
750          * This must come _before_ checksumming (not as RFC 4340 suggests).
751          */
752         cscov = dccp_csum_coverage(skb);
753         if (cscov > skb->len) {
754                 DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
755                           dh->dccph_cscov, skb->len);
756                 return 1;
757         }
758 
759         /* If header checksum is incorrect, drop packet and return.
760          * (This step is completed in the AF-dependent functions.) */
761         skb->csum = skb_checksum(skb, 0, cscov, 0);
762 
763         return 0;
764 }
765 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
766 
767 /* this is called when real data arrives */
768 static int dccp_v4_rcv(struct sk_buff *skb)
769 {
770         const struct dccp_hdr *dh;
771         const struct iphdr *iph;
772         bool refcounted;
773         struct sock *sk;
774         int min_cov;
775 
776         /* Step 1: Check header basics */
777 
778         if (dccp_invalid_packet(skb))
779                 goto discard_it;
780 
781         iph = ip_hdr(skb);
782         /* Step 1: If header checksum is incorrect, drop packet and return */
783         if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
784                 DCCP_WARN("dropped packet with invalid checksum\n");
785                 goto discard_it;
786         }
787 
788         dh = dccp_hdr(skb);
789 
790         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
791         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
792 
793         dccp_pr_debug("%8.8s src=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
794                       dccp_packet_name(dh->dccph_type),
795                       &iph->saddr, ntohs(dh->dccph_sport),
796                       &iph->daddr, ntohs(dh->dccph_dport),
797                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
798 
799         if (dccp_packet_without_ack(skb)) {
800                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
801                 dccp_pr_debug_cat("\n");
802         } else {
803                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
804                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
805                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
806         }
807 
808 lookup:
809         sk = __inet_lookup_skb(&dccp_hashinfo, skb, __dccp_hdr_len(dh),
810                                dh->dccph_sport, dh->dccph_dport, &refcounted);
811         if (!sk) {
812                 dccp_pr_debug("failed to look up flow ID in table and "
813                               "get corresponding socket\n");
814                 goto no_dccp_socket;
815         }
816 
817         /*
818          * Step 2:
819          *      ... or S.state == TIMEWAIT,
820          *              Generate Reset(No Connection) unless P.type == Reset
821          *              Drop packet and return
822          */
823         if (sk->sk_state == DCCP_TIME_WAIT) {
824                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
825                 inet_twsk_put(inet_twsk(sk));
826                 goto no_dccp_socket;
827         }
828 
829         if (sk->sk_state == DCCP_NEW_SYN_RECV) {
830                 struct request_sock *req = inet_reqsk(sk);
831                 struct sock *nsk;
832 
833                 sk = req->rsk_listener;
834                 if (unlikely(sk->sk_state != DCCP_LISTEN)) {
835                         inet_csk_reqsk_queue_drop_and_put(sk, req);
836                         goto lookup;
837                 }
838                 sock_hold(sk);
839                 refcounted = true;
840                 nsk = dccp_check_req(sk, skb, req);
841                 if (!nsk) {
842                         reqsk_put(req);
843                         goto discard_and_relse;
844                 }
845                 if (nsk == sk) {
846                         reqsk_put(req);
847                 } else if (dccp_child_process(sk, nsk, skb)) {
848                         dccp_v4_ctl_send_reset(sk, skb);
849                         goto discard_and_relse;
850                 } else {
851                         sock_put(sk);
852                         return 0;
853                 }
854         }
855         /*
856          * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
857          *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
858          *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
859          */
860         min_cov = dccp_sk(sk)->dccps_pcrlen;
861         if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
862                 dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
863                               dh->dccph_cscov, min_cov);
864                 /* FIXME: "Such packets SHOULD be reported using Data Dropped
865                  *         options (Section 11.7) with Drop Code 0, Protocol
866                  *         Constraints."                                     */
867                 goto discard_and_relse;
868         }
869 
870         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
871                 goto discard_and_relse;
872         nf_reset(skb);
873 
874         return __sk_receive_skb(sk, skb, 1, dh->dccph_doff * 4, refcounted);
875 
876 no_dccp_socket:
877         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
878                 goto discard_it;
879         /*
880          * Step 2:
881          *      If no socket ...
882          *              Generate Reset(No Connection) unless P.type == Reset
883          *              Drop packet and return
884          */
885         if (dh->dccph_type != DCCP_PKT_RESET) {
886                 DCCP_SKB_CB(skb)->dccpd_reset_code =
887                                         DCCP_RESET_CODE_NO_CONNECTION;
888                 dccp_v4_ctl_send_reset(sk, skb);
889         }
890 
891 discard_it:
892         kfree_skb(skb);
893         return 0;
894 
895 discard_and_relse:
896         if (refcounted)
897                 sock_put(sk);
898         goto discard_it;
899 }
900 
901 static const struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
902         .queue_xmit        = ip_queue_xmit,
903         .send_check        = dccp_v4_send_check,
904         .rebuild_header    = inet_sk_rebuild_header,
905         .conn_request      = dccp_v4_conn_request,
906         .syn_recv_sock     = dccp_v4_request_recv_sock,
907         .net_header_len    = sizeof(struct iphdr),
908         .setsockopt        = ip_setsockopt,
909         .getsockopt        = ip_getsockopt,
910         .addr2sockaddr     = inet_csk_addr2sockaddr,
911         .sockaddr_len      = sizeof(struct sockaddr_in),
912 #ifdef CONFIG_COMPAT
913         .compat_setsockopt = compat_ip_setsockopt,
914         .compat_getsockopt = compat_ip_getsockopt,
915 #endif
916 };
917 
918 static int dccp_v4_init_sock(struct sock *sk)
919 {
920         static __u8 dccp_v4_ctl_sock_initialized;
921         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
922 
923         if (err == 0) {
924                 if (unlikely(!dccp_v4_ctl_sock_initialized))
925                         dccp_v4_ctl_sock_initialized = 1;
926                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
927         }
928 
929         return err;
930 }
931 
932 static struct timewait_sock_ops dccp_timewait_sock_ops = {
933         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
934 };
935 
936 static struct proto dccp_v4_prot = {
937         .name                   = "DCCP",
938         .owner                  = THIS_MODULE,
939         .close                  = dccp_close,
940         .connect                = dccp_v4_connect,
941         .disconnect             = dccp_disconnect,
942         .ioctl                  = dccp_ioctl,
943         .init                   = dccp_v4_init_sock,
944         .setsockopt             = dccp_setsockopt,
945         .getsockopt             = dccp_getsockopt,
946         .sendmsg                = dccp_sendmsg,
947         .recvmsg                = dccp_recvmsg,
948         .backlog_rcv            = dccp_v4_do_rcv,
949         .hash                   = inet_hash,
950         .unhash                 = inet_unhash,
951         .accept                 = inet_csk_accept,
952         .get_port               = inet_csk_get_port,
953         .shutdown               = dccp_shutdown,
954         .destroy                = dccp_destroy_sock,
955         .orphan_count           = &dccp_orphan_count,
956         .max_header             = MAX_DCCP_HEADER,
957         .obj_size               = sizeof(struct dccp_sock),
958         .slab_flags             = SLAB_TYPESAFE_BY_RCU,
959         .rsk_prot               = &dccp_request_sock_ops,
960         .twsk_prot              = &dccp_timewait_sock_ops,
961         .h.hashinfo             = &dccp_hashinfo,
962 #ifdef CONFIG_COMPAT
963         .compat_setsockopt      = compat_dccp_setsockopt,
964         .compat_getsockopt      = compat_dccp_getsockopt,
965 #endif
966 };
967 
968 static const struct net_protocol dccp_v4_protocol = {
969         .handler        = dccp_v4_rcv,
970         .err_handler    = dccp_v4_err,
971         .no_policy      = 1,
972         .netns_ok       = 1,
973         .icmp_strict_tag_validation = 1,
974 };
975 
976 static const struct proto_ops inet_dccp_ops = {
977         .family            = PF_INET,
978         .owner             = THIS_MODULE,
979         .release           = inet_release,
980         .bind              = inet_bind,
981         .connect           = inet_stream_connect,
982         .socketpair        = sock_no_socketpair,
983         .accept            = inet_accept,
984         .getname           = inet_getname,
985         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
986         .poll              = dccp_poll,
987         .ioctl             = inet_ioctl,
988         /* FIXME: work on inet_listen to rename it to sock_common_listen */
989         .listen            = inet_dccp_listen,
990         .shutdown          = inet_shutdown,
991         .setsockopt        = sock_common_setsockopt,
992         .getsockopt        = sock_common_getsockopt,
993         .sendmsg           = inet_sendmsg,
994         .recvmsg           = sock_common_recvmsg,
995         .mmap              = sock_no_mmap,
996         .sendpage          = sock_no_sendpage,
997 #ifdef CONFIG_COMPAT
998         .compat_setsockopt = compat_sock_common_setsockopt,
999         .compat_getsockopt = compat_sock_common_getsockopt,
1000 #endif
1001 };
1002 
1003 static struct inet_protosw dccp_v4_protosw = {
1004         .type           = SOCK_DCCP,
1005         .protocol       = IPPROTO_DCCP,
1006         .prot           = &dccp_v4_prot,
1007         .ops            = &inet_dccp_ops,
1008         .flags          = INET_PROTOSW_ICSK,
1009 };
1010 
1011 static int __net_init dccp_v4_init_net(struct net *net)
1012 {
1013         if (dccp_hashinfo.bhash == NULL)
1014                 return -ESOCKTNOSUPPORT;
1015 
1016         return inet_ctl_sock_create(&net->dccp.v4_ctl_sk, PF_INET,
1017                                     SOCK_DCCP, IPPROTO_DCCP, net);
1018 }
1019 
1020 static void __net_exit dccp_v4_exit_net(struct net *net)
1021 {
1022         inet_ctl_sock_destroy(net->dccp.v4_ctl_sk);
1023 }
1024 
1025 static void __net_exit dccp_v4_exit_batch(struct list_head *net_exit_list)
1026 {
1027         inet_twsk_purge(&dccp_hashinfo, AF_INET);
1028 }
1029 
1030 static struct pernet_operations dccp_v4_ops = {
1031         .init   = dccp_v4_init_net,
1032         .exit   = dccp_v4_exit_net,
1033         .exit_batch = dccp_v4_exit_batch,
1034 };
1035 
1036 static int __init dccp_v4_init(void)
1037 {
1038         int err = proto_register(&dccp_v4_prot, 1);
1039 
1040         if (err)
1041                 goto out;
1042 
1043         inet_register_protosw(&dccp_v4_protosw);
1044 
1045         err = register_pernet_subsys(&dccp_v4_ops);
1046         if (err)
1047                 goto out_destroy_ctl_sock;
1048 
1049         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1050         if (err)
1051                 goto out_proto_unregister;
1052 
1053 out:
1054         return err;
1055 out_proto_unregister:
1056         unregister_pernet_subsys(&dccp_v4_ops);
1057 out_destroy_ctl_sock:
1058         inet_unregister_protosw(&dccp_v4_protosw);
1059         proto_unregister(&dccp_v4_prot);
1060         goto out;
1061 }
1062 
1063 static void __exit dccp_v4_exit(void)
1064 {
1065         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1066         unregister_pernet_subsys(&dccp_v4_ops);
1067         inet_unregister_protosw(&dccp_v4_protosw);
1068         proto_unregister(&dccp_v4_prot);
1069 }
1070 
1071 module_init(dccp_v4_init);
1072 module_exit(dccp_v4_exit);
1073 
1074 /*
1075  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1076  * values directly, Also cover the case where the protocol is not specified,
1077  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1078  */
1079 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
1080 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
1081 MODULE_LICENSE("GPL");
1082 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1083 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");
1084 

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