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TOMOYO Linux Cross Reference
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                                              sock_owned_by_user(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, true);
 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         inet->inet_rcv_saddr = inet->inet_saddr;
 93 
 94         inet->inet_dport = usin->sin_port;
 95         inet->inet_daddr = daddr;
 96 
 97         inet_csk(sk)->icsk_ext_hdr_len = 0;
 98         if (inet_opt)
 99                 inet_csk(sk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
100         /*
101          * Socket identity is still unknown (sport may be zero).
102          * However we set state to DCCP_REQUESTING and not releasing socket
103          * lock select source port, enter ourselves into the hash tables and
104          * complete initialization after this.
105          */
106         dccp_set_state(sk, DCCP_REQUESTING);
107         err = inet_hash_connect(&dccp_death_row, sk);
108         if (err != 0)
109                 goto failure;
110 
111         rt = ip_route_newports(fl4, rt, orig_sport, orig_dport,
112                                inet->inet_sport, inet->inet_dport, sk);
113         if (IS_ERR(rt)) {
114                 err = PTR_ERR(rt);
115                 rt = NULL;
116                 goto failure;
117         }
118         /* OK, now commit destination to socket.  */
119         sk_setup_caps(sk, &rt->dst);
120 
121         dp->dccps_iss = secure_dccp_sequence_number(inet->inet_saddr,
122                                                     inet->inet_daddr,
123                                                     inet->inet_sport,
124                                                     inet->inet_dport);
125         inet->inet_id = dp->dccps_iss ^ jiffies;
126 
127         err = dccp_connect(sk);
128         rt = NULL;
129         if (err != 0)
130                 goto failure;
131 out:
132         return err;
133 failure:
134         /*
135          * This unhashes the socket and releases the local port, if necessary.
136          */
137         dccp_set_state(sk, DCCP_CLOSED);
138         ip_rt_put(rt);
139         sk->sk_route_caps = 0;
140         inet->inet_dport = 0;
141         goto out;
142 }
143 
144 EXPORT_SYMBOL_GPL(dccp_v4_connect);
145 
146 /*
147  * This routine does path mtu discovery as defined in RFC1191.
148  */
149 static inline void dccp_do_pmtu_discovery(struct sock *sk,
150                                           const struct iphdr *iph,
151                                           u32 mtu)
152 {
153         struct dst_entry *dst;
154         const struct inet_sock *inet = inet_sk(sk);
155         const struct dccp_sock *dp = dccp_sk(sk);
156 
157         /* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
158          * send out by Linux are always < 576bytes so they should go through
159          * unfragmented).
160          */
161         if (sk->sk_state == DCCP_LISTEN)
162                 return;
163 
164         /* We don't check in the destentry if pmtu discovery is forbidden
165          * on this route. We just assume that no packet_to_big packets
166          * are send back when pmtu discovery is not active.
167          * There is a small race when the user changes this flag in the
168          * route, but I think that's acceptable.
169          */
170         if ((dst = __sk_dst_check(sk, 0)) == NULL)
171                 return;
172 
173         dst->ops->update_pmtu(dst, mtu);
174 
175         /* Something is about to be wrong... Remember soft error
176          * for the case, if this connection will not able to recover.
177          */
178         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
179                 sk->sk_err_soft = EMSGSIZE;
180 
181         mtu = dst_mtu(dst);
182 
183         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
184             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
185                 dccp_sync_mss(sk, mtu);
186 
187                 /*
188                  * From RFC 4340, sec. 14.1:
189                  *
190                  *      DCCP-Sync packets are the best choice for upward
191                  *      probing, since DCCP-Sync probes do not risk application
192                  *      data loss.
193                  */
194                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
195         } /* else let the usual retransmit timer handle it */
196 }
197 
198 /*
199  * This routine is called by the ICMP module when it gets some sort of error
200  * condition. If err < 0 then the socket should be closed and the error
201  * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
202  * After adjustment header points to the first 8 bytes of the tcp header. We
203  * need to find the appropriate port.
204  *
205  * The locking strategy used here is very "optimistic". When someone else
206  * accesses the socket the ICMP is just dropped and for some paths there is no
207  * check at all. A more general error queue to queue errors for later handling
208  * is probably better.
209  */
210 static void dccp_v4_err(struct sk_buff *skb, u32 info)
211 {
212         const struct iphdr *iph = (struct iphdr *)skb->data;
213         const u8 offset = iph->ihl << 2;
214         const struct dccp_hdr *dh;
215         struct dccp_sock *dp;
216         struct inet_sock *inet;
217         const int type = icmp_hdr(skb)->type;
218         const int code = icmp_hdr(skb)->code;
219         struct sock *sk;
220         __u64 seq;
221         int err;
222         struct net *net = dev_net(skb->dev);
223 
224         /* Only need dccph_dport & dccph_sport which are the first
225          * 4 bytes in dccp header.
226          * Our caller (icmp_socket_deliver()) already pulled 8 bytes for us.
227          */
228         BUILD_BUG_ON(offsetof(struct dccp_hdr, dccph_sport) + sizeof(dh->dccph_sport) > 8);
229         BUILD_BUG_ON(offsetof(struct dccp_hdr, dccph_dport) + sizeof(dh->dccph_dport) > 8);
230         dh = (struct dccp_hdr *)(skb->data + offset);
231 
232         sk = inet_lookup(net, &dccp_hashinfo,
233                         iph->daddr, dh->dccph_dport,
234                         iph->saddr, dh->dccph_sport, inet_iif(skb));
235         if (sk == NULL) {
236                 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
237                 return;
238         }
239 
240         if (sk->sk_state == DCCP_TIME_WAIT) {
241                 inet_twsk_put(inet_twsk(sk));
242                 return;
243         }
244 
245         bh_lock_sock(sk);
246         /* If too many ICMPs get dropped on busy
247          * servers this needs to be solved differently.
248          */
249         if (sock_owned_by_user(sk))
250                 NET_INC_STATS_BH(net, LINUX_MIB_LOCKDROPPEDICMPS);
251 
252         if (sk->sk_state == DCCP_CLOSED)
253                 goto out;
254 
255         dp = dccp_sk(sk);
256         seq = dccp_hdr_seq(dh);
257         if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
258             !between48(seq, dp->dccps_awl, dp->dccps_awh)) {
259                 NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
260                 goto out;
261         }
262 
263         switch (type) {
264         case ICMP_SOURCE_QUENCH:
265                 /* Just silently ignore these. */
266                 goto out;
267         case ICMP_PARAMETERPROB:
268                 err = EPROTO;
269                 break;
270         case ICMP_DEST_UNREACH:
271                 if (code > NR_ICMP_UNREACH)
272                         goto out;
273 
274                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
275                         if (!sock_owned_by_user(sk))
276                                 dccp_do_pmtu_discovery(sk, iph, info);
277                         goto out;
278                 }
279 
280                 err = icmp_err_convert[code].errno;
281                 break;
282         case ICMP_TIME_EXCEEDED:
283                 err = EHOSTUNREACH;
284                 break;
285         default:
286                 goto out;
287         }
288 
289         switch (sk->sk_state) {
290                 struct request_sock *req , **prev;
291         case DCCP_LISTEN:
292                 if (sock_owned_by_user(sk))
293                         goto out;
294                 req = inet_csk_search_req(sk, &prev, dh->dccph_dport,
295                                           iph->daddr, iph->saddr);
296                 if (!req)
297                         goto out;
298 
299                 /*
300                  * ICMPs are not backlogged, hence we cannot get an established
301                  * socket here.
302                  */
303                 WARN_ON(req->sk);
304 
305                 if (seq != dccp_rsk(req)->dreq_iss) {
306                         NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
307                         goto out;
308                 }
309                 /*
310                  * Still in RESPOND, just remove it silently.
311                  * There is no good way to pass the error to the newly
312                  * created socket, and POSIX does not want network
313                  * errors returned from accept().
314                  */
315                 inet_csk_reqsk_queue_drop(sk, req, prev);
316                 goto out;
317 
318         case DCCP_REQUESTING:
319         case DCCP_RESPOND:
320                 if (!sock_owned_by_user(sk)) {
321                         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
322                         sk->sk_err = err;
323 
324                         sk->sk_error_report(sk);
325 
326                         dccp_done(sk);
327                 } else
328                         sk->sk_err_soft = err;
329                 goto out;
330         }
331 
332         /* If we've already connected we will keep trying
333          * until we time out, or the user gives up.
334          *
335          * rfc1122 4.2.3.9 allows to consider as hard errors
336          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
337          * but it is obsoleted by pmtu discovery).
338          *
339          * Note, that in modern internet, where routing is unreliable
340          * and in each dark corner broken firewalls sit, sending random
341          * errors ordered by their masters even this two messages finally lose
342          * their original sense (even Linux sends invalid PORT_UNREACHs)
343          *
344          * Now we are in compliance with RFCs.
345          *                                                      --ANK (980905)
346          */
347 
348         inet = inet_sk(sk);
349         if (!sock_owned_by_user(sk) && inet->recverr) {
350                 sk->sk_err = err;
351                 sk->sk_error_report(sk);
352         } else /* Only an error on timeout */
353                 sk->sk_err_soft = err;
354 out:
355         bh_unlock_sock(sk);
356         sock_put(sk);
357 }
358 
359 static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
360                                       __be32 src, __be32 dst)
361 {
362         return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
363 }
364 
365 void dccp_v4_send_check(struct sock *sk, struct sk_buff *skb)
366 {
367         const struct inet_sock *inet = inet_sk(sk);
368         struct dccp_hdr *dh = dccp_hdr(skb);
369 
370         dccp_csum_outgoing(skb);
371         dh->dccph_checksum = dccp_v4_csum_finish(skb,
372                                                  inet->inet_saddr,
373                                                  inet->inet_daddr);
374 }
375 
376 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
377 
378 static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
379 {
380         return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
381                                            ip_hdr(skb)->saddr,
382                                            dccp_hdr(skb)->dccph_dport,
383                                            dccp_hdr(skb)->dccph_sport);
384 }
385 
386 /*
387  * The three way handshake has completed - we got a valid ACK or DATAACK -
388  * now create the new socket.
389  *
390  * This is the equivalent of TCP's tcp_v4_syn_recv_sock
391  */
392 struct sock *dccp_v4_request_recv_sock(struct sock *sk, struct sk_buff *skb,
393                                        struct request_sock *req,
394                                        struct dst_entry *dst)
395 {
396         struct inet_request_sock *ireq;
397         struct inet_sock *newinet;
398         struct sock *newsk;
399 
400         if (sk_acceptq_is_full(sk))
401                 goto exit_overflow;
402 
403         newsk = dccp_create_openreq_child(sk, req, skb);
404         if (newsk == NULL)
405                 goto exit_nonewsk;
406 
407         newinet            = inet_sk(newsk);
408         ireq               = inet_rsk(req);
409         newinet->inet_daddr     = ireq->rmt_addr;
410         newinet->inet_rcv_saddr = ireq->loc_addr;
411         newinet->inet_saddr     = ireq->loc_addr;
412         newinet->inet_opt       = ireq->opt;
413         ireq->opt          = NULL;
414         newinet->mc_index  = inet_iif(skb);
415         newinet->mc_ttl    = ip_hdr(skb)->ttl;
416         newinet->inet_id   = jiffies;
417 
418         if (dst == NULL && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
419                 goto put_and_exit;
420 
421         sk_setup_caps(newsk, dst);
422 
423         dccp_sync_mss(newsk, dst_mtu(dst));
424 
425         if (__inet_inherit_port(sk, newsk) < 0)
426                 goto put_and_exit;
427         __inet_hash_nolisten(newsk, NULL);
428 
429         return newsk;
430 
431 exit_overflow:
432         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
433 exit_nonewsk:
434         dst_release(dst);
435 exit:
436         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
437         return NULL;
438 put_and_exit:
439         inet_csk_prepare_forced_close(newsk);
440         dccp_done(newsk);
441         goto exit;
442 }
443 
444 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
445 
446 static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
447 {
448         const struct dccp_hdr *dh = dccp_hdr(skb);
449         const struct iphdr *iph = ip_hdr(skb);
450         struct sock *nsk;
451         struct request_sock **prev;
452         /* Find possible connection requests. */
453         struct request_sock *req = inet_csk_search_req(sk, &prev,
454                                                        dh->dccph_sport,
455                                                        iph->saddr, iph->daddr);
456         if (req != NULL)
457                 return dccp_check_req(sk, skb, req, prev);
458 
459         nsk = inet_lookup_established(sock_net(sk), &dccp_hashinfo,
460                                       iph->saddr, dh->dccph_sport,
461                                       iph->daddr, dh->dccph_dport,
462                                       inet_iif(skb));
463         if (nsk != NULL) {
464                 if (nsk->sk_state != DCCP_TIME_WAIT) {
465                         bh_lock_sock(nsk);
466                         return nsk;
467                 }
468                 inet_twsk_put(inet_twsk(nsk));
469                 return NULL;
470         }
471 
472         return sk;
473 }
474 
475 static struct dst_entry* dccp_v4_route_skb(struct net *net, struct sock *sk,
476                                            struct sk_buff *skb)
477 {
478         struct rtable *rt;
479         struct flowi4 fl4 = {
480                 .flowi4_oif = skb_rtable(skb)->rt_iif,
481                 .daddr = ip_hdr(skb)->saddr,
482                 .saddr = ip_hdr(skb)->daddr,
483                 .flowi4_tos = RT_CONN_FLAGS(sk),
484                 .flowi4_proto = sk->sk_protocol,
485                 .fl4_sport = dccp_hdr(skb)->dccph_dport,
486                 .fl4_dport = dccp_hdr(skb)->dccph_sport,
487         };
488 
489         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
490         rt = ip_route_output_flow(net, &fl4, sk);
491         if (IS_ERR(rt)) {
492                 IP_INC_STATS_BH(net, IPSTATS_MIB_OUTNOROUTES);
493                 return NULL;
494         }
495 
496         return &rt->dst;
497 }
498 
499 static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
500                                  struct request_values *rv_unused)
501 {
502         int err = -1;
503         struct sk_buff *skb;
504         struct dst_entry *dst;
505         struct flowi4 fl4;
506 
507         dst = inet_csk_route_req(sk, &fl4, req);
508         if (dst == NULL)
509                 goto out;
510 
511         skb = dccp_make_response(sk, dst, req);
512         if (skb != NULL) {
513                 const struct inet_request_sock *ireq = inet_rsk(req);
514                 struct dccp_hdr *dh = dccp_hdr(skb);
515 
516                 dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->loc_addr,
517                                                               ireq->rmt_addr);
518                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
519                                             ireq->rmt_addr,
520                                             ireq->opt);
521                 err = net_xmit_eval(err);
522         }
523 
524 out:
525         dst_release(dst);
526         return err;
527 }
528 
529 static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
530 {
531         int err;
532         const struct iphdr *rxiph;
533         struct sk_buff *skb;
534         struct dst_entry *dst;
535         struct net *net = dev_net(skb_dst(rxskb)->dev);
536         struct sock *ctl_sk = net->dccp.v4_ctl_sk;
537 
538         /* Never send a reset in response to a reset. */
539         if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
540                 return;
541 
542         if (skb_rtable(rxskb)->rt_type != RTN_LOCAL)
543                 return;
544 
545         dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
546         if (dst == NULL)
547                 return;
548 
549         skb = dccp_ctl_make_reset(ctl_sk, rxskb);
550         if (skb == NULL)
551                 goto out;
552 
553         rxiph = ip_hdr(rxskb);
554         dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
555                                                                  rxiph->daddr);
556         skb_dst_set(skb, dst_clone(dst));
557 
558         bh_lock_sock(ctl_sk);
559         err = ip_build_and_send_pkt(skb, ctl_sk,
560                                     rxiph->daddr, rxiph->saddr, NULL);
561         bh_unlock_sock(ctl_sk);
562 
563         if (net_xmit_eval(err) == 0) {
564                 DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
565                 DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
566         }
567 out:
568          dst_release(dst);
569 }
570 
571 static void dccp_v4_reqsk_destructor(struct request_sock *req)
572 {
573         dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
574         kfree(inet_rsk(req)->opt);
575 }
576 
577 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
578         .family         = PF_INET,
579         .obj_size       = sizeof(struct dccp_request_sock),
580         .rtx_syn_ack    = dccp_v4_send_response,
581         .send_ack       = dccp_reqsk_send_ack,
582         .destructor     = dccp_v4_reqsk_destructor,
583         .send_reset     = dccp_v4_ctl_send_reset,
584 };
585 
586 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
587 {
588         struct inet_request_sock *ireq;
589         struct request_sock *req;
590         struct dccp_request_sock *dreq;
591         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
592         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
593 
594         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
595         if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
596                 return 0;       /* discard, don't send a reset here */
597 
598         if (dccp_bad_service_code(sk, service)) {
599                 dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
600                 goto drop;
601         }
602         /*
603          * TW buckets are converted to open requests without
604          * limitations, they conserve resources and peer is
605          * evidently real one.
606          */
607         dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
608         if (inet_csk_reqsk_queue_is_full(sk))
609                 goto drop;
610 
611         /*
612          * Accept backlog is full. If we have already queued enough
613          * of warm entries in syn queue, drop request. It is better than
614          * clogging syn queue with openreqs with exponentially increasing
615          * timeout.
616          */
617         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
618                 goto drop;
619 
620         req = inet_reqsk_alloc(&dccp_request_sock_ops);
621         if (req == NULL)
622                 goto drop;
623 
624         if (dccp_reqsk_init(req, dccp_sk(sk), skb))
625                 goto drop_and_free;
626 
627         dreq = dccp_rsk(req);
628         if (dccp_parse_options(sk, dreq, skb))
629                 goto drop_and_free;
630 
631         if (security_inet_conn_request(sk, skb, req))
632                 goto drop_and_free;
633 
634         ireq = inet_rsk(req);
635         ireq->loc_addr = ip_hdr(skb)->daddr;
636         ireq->rmt_addr = ip_hdr(skb)->saddr;
637 
638         /*
639          * Step 3: Process LISTEN state
640          *
641          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
642          *
643          * In fact we defer setting S.GSR, S.SWL, S.SWH to
644          * dccp_create_openreq_child.
645          */
646         dreq->dreq_isr     = dcb->dccpd_seq;
647         dreq->dreq_iss     = dccp_v4_init_sequence(skb);
648         dreq->dreq_service = service;
649 
650         if (dccp_v4_send_response(sk, req, NULL))
651                 goto drop_and_free;
652 
653         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
654         return 0;
655 
656 drop_and_free:
657         reqsk_free(req);
658 drop:
659         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
660         return -1;
661 }
662 
663 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
664 
665 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
666 {
667         struct dccp_hdr *dh = dccp_hdr(skb);
668 
669         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
670                 if (dccp_rcv_established(sk, skb, dh, skb->len))
671                         goto reset;
672                 return 0;
673         }
674 
675         /*
676          *  Step 3: Process LISTEN state
677          *       If P.type == Request or P contains a valid Init Cookie option,
678          *            (* Must scan the packet's options to check for Init
679          *               Cookies.  Only Init Cookies are processed here,
680          *               however; other options are processed in Step 8.  This
681          *               scan need only be performed if the endpoint uses Init
682          *               Cookies *)
683          *            (* Generate a new socket and switch to that socket *)
684          *            Set S := new socket for this port pair
685          *            S.state = RESPOND
686          *            Choose S.ISS (initial seqno) or set from Init Cookies
687          *            Initialize S.GAR := S.ISS
688          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
689          *            Continue with S.state == RESPOND
690          *            (* A Response packet will be generated in Step 11 *)
691          *       Otherwise,
692          *            Generate Reset(No Connection) unless P.type == Reset
693          *            Drop packet and return
694          *
695          * NOTE: the check for the packet types is done in
696          *       dccp_rcv_state_process
697          */
698         if (sk->sk_state == DCCP_LISTEN) {
699                 struct sock *nsk = dccp_v4_hnd_req(sk, skb);
700 
701                 if (nsk == NULL)
702                         goto discard;
703 
704                 if (nsk != sk) {
705                         if (dccp_child_process(sk, nsk, skb))
706                                 goto reset;
707                         return 0;
708                 }
709         }
710 
711         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
712                 goto reset;
713         return 0;
714 
715 reset:
716         dccp_v4_ctl_send_reset(sk, skb);
717 discard:
718         kfree_skb(skb);
719         return 0;
720 }
721 
722 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
723 
724 /**
725  *      dccp_invalid_packet  -  check for malformed packets
726  *      Implements RFC 4340, 8.5:  Step 1: Check header basics
727  *      Packets that fail these checks are ignored and do not receive Resets.
728  */
729 int dccp_invalid_packet(struct sk_buff *skb)
730 {
731         const struct dccp_hdr *dh;
732         unsigned int cscov;
733         u8 dccph_doff;
734 
735         if (skb->pkt_type != PACKET_HOST)
736                 return 1;
737 
738         /* If the packet is shorter than 12 bytes, drop packet and return */
739         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
740                 DCCP_WARN("pskb_may_pull failed\n");
741                 return 1;
742         }
743 
744         dh = dccp_hdr(skb);
745 
746         /* If P.type is not understood, drop packet and return */
747         if (dh->dccph_type >= DCCP_PKT_INVALID) {
748                 DCCP_WARN("invalid packet type\n");
749                 return 1;
750         }
751 
752         /*
753          * If P.Data Offset is too small for packet type, drop packet and return
754          */
755         dccph_doff = dh->dccph_doff;
756         if (dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
757                 DCCP_WARN("P.Data Offset(%u) too small\n", dccph_doff);
758                 return 1;
759         }
760         /*
761          * If P.Data Offset is too too large for packet, drop packet and return
762          */
763         if (!pskb_may_pull(skb, dccph_doff * sizeof(u32))) {
764                 DCCP_WARN("P.Data Offset(%u) too large\n", dccph_doff);
765                 return 1;
766         }
767         dh = dccp_hdr(skb);
768         /*
769          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
770          * has short sequence numbers), drop packet and return
771          */
772         if ((dh->dccph_type < DCCP_PKT_DATA    ||
773             dh->dccph_type > DCCP_PKT_DATAACK) && dh->dccph_x == 0)  {
774                 DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
775                           dccp_packet_name(dh->dccph_type));
776                 return 1;
777         }
778 
779         /*
780          * If P.CsCov is too large for the packet size, drop packet and return.
781          * This must come _before_ checksumming (not as RFC 4340 suggests).
782          */
783         cscov = dccp_csum_coverage(skb);
784         if (cscov > skb->len) {
785                 DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
786                           dh->dccph_cscov, skb->len);
787                 return 1;
788         }
789 
790         /* If header checksum is incorrect, drop packet and return.
791          * (This step is completed in the AF-dependent functions.) */
792         skb->csum = skb_checksum(skb, 0, cscov, 0);
793 
794         return 0;
795 }
796 
797 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
798 
799 /* this is called when real data arrives */
800 static int dccp_v4_rcv(struct sk_buff *skb)
801 {
802         const struct dccp_hdr *dh;
803         const struct iphdr *iph;
804         struct sock *sk;
805         int min_cov;
806 
807         /* Step 1: Check header basics */
808 
809         if (dccp_invalid_packet(skb))
810                 goto discard_it;
811 
812         iph = ip_hdr(skb);
813         /* Step 1: If header checksum is incorrect, drop packet and return */
814         if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
815                 DCCP_WARN("dropped packet with invalid checksum\n");
816                 goto discard_it;
817         }
818 
819         dh = dccp_hdr(skb);
820 
821         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
822         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
823 
824         dccp_pr_debug("%8.8s src=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
825                       dccp_packet_name(dh->dccph_type),
826                       &iph->saddr, ntohs(dh->dccph_sport),
827                       &iph->daddr, ntohs(dh->dccph_dport),
828                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
829 
830         if (dccp_packet_without_ack(skb)) {
831                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
832                 dccp_pr_debug_cat("\n");
833         } else {
834                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
835                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
836                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
837         }
838 
839         /* Step 2:
840          *      Look up flow ID in table and get corresponding socket */
841         sk = __inet_lookup_skb(&dccp_hashinfo, skb,
842                                dh->dccph_sport, dh->dccph_dport);
843         /*
844          * Step 2:
845          *      If no socket ...
846          */
847         if (sk == NULL) {
848                 dccp_pr_debug("failed to look up flow ID in table and "
849                               "get corresponding socket\n");
850                 goto no_dccp_socket;
851         }
852 
853         /*
854          * Step 2:
855          *      ... or S.state == TIMEWAIT,
856          *              Generate Reset(No Connection) unless P.type == Reset
857          *              Drop packet and return
858          */
859         if (sk->sk_state == DCCP_TIME_WAIT) {
860                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
861                 inet_twsk_put(inet_twsk(sk));
862                 goto no_dccp_socket;
863         }
864 
865         /*
866          * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
867          *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
868          *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
869          */
870         min_cov = dccp_sk(sk)->dccps_pcrlen;
871         if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
872                 dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
873                               dh->dccph_cscov, min_cov);
874                 /* FIXME: "Such packets SHOULD be reported using Data Dropped
875                  *         options (Section 11.7) with Drop Code 0, Protocol
876                  *         Constraints."                                     */
877                 goto discard_and_relse;
878         }
879 
880         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
881                 goto discard_and_relse;
882         nf_reset(skb);
883 
884         return __sk_receive_skb(sk, skb, 1, dh->dccph_doff * 4);
885 
886 no_dccp_socket:
887         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
888                 goto discard_it;
889         /*
890          * Step 2:
891          *      If no socket ...
892          *              Generate Reset(No Connection) unless P.type == Reset
893          *              Drop packet and return
894          */
895         if (dh->dccph_type != DCCP_PKT_RESET) {
896                 DCCP_SKB_CB(skb)->dccpd_reset_code =
897                                         DCCP_RESET_CODE_NO_CONNECTION;
898                 dccp_v4_ctl_send_reset(sk, skb);
899         }
900 
901 discard_it:
902         kfree_skb(skb);
903         return 0;
904 
905 discard_and_relse:
906         sock_put(sk);
907         goto discard_it;
908 }
909 
910 static const struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
911         .queue_xmit        = ip_queue_xmit,
912         .send_check        = dccp_v4_send_check,
913         .rebuild_header    = inet_sk_rebuild_header,
914         .conn_request      = dccp_v4_conn_request,
915         .syn_recv_sock     = dccp_v4_request_recv_sock,
916         .net_header_len    = sizeof(struct iphdr),
917         .setsockopt        = ip_setsockopt,
918         .getsockopt        = ip_getsockopt,
919         .addr2sockaddr     = inet_csk_addr2sockaddr,
920         .sockaddr_len      = sizeof(struct sockaddr_in),
921         .bind_conflict     = inet_csk_bind_conflict,
922 #ifdef CONFIG_COMPAT
923         .compat_setsockopt = compat_ip_setsockopt,
924         .compat_getsockopt = compat_ip_getsockopt,
925 #endif
926 };
927 
928 static int dccp_v4_init_sock(struct sock *sk)
929 {
930         static __u8 dccp_v4_ctl_sock_initialized;
931         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
932 
933         if (err == 0) {
934                 if (unlikely(!dccp_v4_ctl_sock_initialized))
935                         dccp_v4_ctl_sock_initialized = 1;
936                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
937         }
938 
939         return err;
940 }
941 
942 static struct timewait_sock_ops dccp_timewait_sock_ops = {
943         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
944 };
945 
946 static struct proto dccp_v4_prot = {
947         .name                   = "DCCP",
948         .owner                  = THIS_MODULE,
949         .close                  = dccp_close,
950         .connect                = dccp_v4_connect,
951         .disconnect             = dccp_disconnect,
952         .ioctl                  = dccp_ioctl,
953         .init                   = dccp_v4_init_sock,
954         .setsockopt             = dccp_setsockopt,
955         .getsockopt             = dccp_getsockopt,
956         .sendmsg                = dccp_sendmsg,
957         .recvmsg                = dccp_recvmsg,
958         .backlog_rcv            = dccp_v4_do_rcv,
959         .hash                   = inet_hash,
960         .unhash                 = inet_unhash,
961         .accept                 = inet_csk_accept,
962         .get_port               = inet_csk_get_port,
963         .shutdown               = dccp_shutdown,
964         .destroy                = dccp_destroy_sock,
965         .orphan_count           = &dccp_orphan_count,
966         .max_header             = MAX_DCCP_HEADER,
967         .obj_size               = sizeof(struct dccp_sock),
968         .slab_flags             = SLAB_DESTROY_BY_RCU,
969         .rsk_prot               = &dccp_request_sock_ops,
970         .twsk_prot              = &dccp_timewait_sock_ops,
971         .h.hashinfo             = &dccp_hashinfo,
972 #ifdef CONFIG_COMPAT
973         .compat_setsockopt      = compat_dccp_setsockopt,
974         .compat_getsockopt      = compat_dccp_getsockopt,
975 #endif
976 };
977 
978 static const struct net_protocol dccp_v4_protocol = {
979         .handler        = dccp_v4_rcv,
980         .err_handler    = dccp_v4_err,
981         .no_policy      = 1,
982         .netns_ok       = 1,
983 };
984 
985 static const struct proto_ops inet_dccp_ops = {
986         .family            = PF_INET,
987         .owner             = THIS_MODULE,
988         .release           = inet_release,
989         .bind              = inet_bind,
990         .connect           = inet_stream_connect,
991         .socketpair        = sock_no_socketpair,
992         .accept            = inet_accept,
993         .getname           = inet_getname,
994         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
995         .poll              = dccp_poll,
996         .ioctl             = inet_ioctl,
997         /* FIXME: work on inet_listen to rename it to sock_common_listen */
998         .listen            = inet_dccp_listen,
999         .shutdown          = inet_shutdown,
1000         .setsockopt        = sock_common_setsockopt,
1001         .getsockopt        = sock_common_getsockopt,
1002         .sendmsg           = inet_sendmsg,
1003         .recvmsg           = sock_common_recvmsg,
1004         .mmap              = sock_no_mmap,
1005         .sendpage          = sock_no_sendpage,
1006 #ifdef CONFIG_COMPAT
1007         .compat_setsockopt = compat_sock_common_setsockopt,
1008         .compat_getsockopt = compat_sock_common_getsockopt,
1009 #endif
1010 };
1011 
1012 static struct inet_protosw dccp_v4_protosw = {
1013         .type           = SOCK_DCCP,
1014         .protocol       = IPPROTO_DCCP,
1015         .prot           = &dccp_v4_prot,
1016         .ops            = &inet_dccp_ops,
1017         .no_check       = 0,
1018         .flags          = INET_PROTOSW_ICSK,
1019 };
1020 
1021 static int __net_init dccp_v4_init_net(struct net *net)
1022 {
1023         if (dccp_hashinfo.bhash == NULL)
1024                 return -ESOCKTNOSUPPORT;
1025 
1026         return inet_ctl_sock_create(&net->dccp.v4_ctl_sk, PF_INET,
1027                                     SOCK_DCCP, IPPROTO_DCCP, net);
1028 }
1029 
1030 static void __net_exit dccp_v4_exit_net(struct net *net)
1031 {
1032         inet_ctl_sock_destroy(net->dccp.v4_ctl_sk);
1033 }
1034 
1035 static void __net_exit dccp_v4_exit_batch(struct list_head *net_exit_list)
1036 {
1037         inet_twsk_purge(&dccp_hashinfo, &dccp_death_row, AF_INET);
1038 }
1039 
1040 static struct pernet_operations dccp_v4_ops = {
1041         .init   = dccp_v4_init_net,
1042         .exit   = dccp_v4_exit_net,
1043         .exit_batch = dccp_v4_exit_batch,
1044 };
1045 
1046 static int __init dccp_v4_init(void)
1047 {
1048         int err = proto_register(&dccp_v4_prot, 1);
1049 
1050         if (err != 0)
1051                 goto out;
1052 
1053         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1054         if (err != 0)
1055                 goto out_proto_unregister;
1056 
1057         inet_register_protosw(&dccp_v4_protosw);
1058 
1059         err = register_pernet_subsys(&dccp_v4_ops);
1060         if (err)
1061                 goto out_destroy_ctl_sock;
1062 out:
1063         return err;
1064 out_destroy_ctl_sock:
1065         inet_unregister_protosw(&dccp_v4_protosw);
1066         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1067 out_proto_unregister:
1068         proto_unregister(&dccp_v4_prot);
1069         goto out;
1070 }
1071 
1072 static void __exit dccp_v4_exit(void)
1073 {
1074         unregister_pernet_subsys(&dccp_v4_ops);
1075         inet_unregister_protosw(&dccp_v4_protosw);
1076         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1077         proto_unregister(&dccp_v4_prot);
1078 }
1079 
1080 module_init(dccp_v4_init);
1081 module_exit(dccp_v4_exit);
1082 
1083 /*
1084  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1085  * values directly, Also cover the case where the protocol is not specified,
1086  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1087  */
1088 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
1089 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
1090 MODULE_LICENSE("GPL");
1091 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1092 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");
1093 

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