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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 int 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), 0);
260         if (!sk) {
261                 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
262                 return -ENOENT;
263         }
264 
265         if (sk->sk_state == DCCP_TIME_WAIT) {
266                 inet_twsk_put(inet_twsk(sk));
267                 return 0;
268         }
269         seq = dccp_hdr_seq(dh);
270         if (sk->sk_state == DCCP_NEW_SYN_RECV) {
271                 dccp_req_err(sk, seq);
272                 return 0;
273         }
274 
275         bh_lock_sock(sk);
276         /* If too many ICMPs get dropped on busy
277          * servers this needs to be solved differently.
278          */
279         if (sock_owned_by_user(sk))
280                 __NET_INC_STATS(net, LINUX_MIB_LOCKDROPPEDICMPS);
281 
282         if (sk->sk_state == DCCP_CLOSED)
283                 goto out;
284 
285         dp = dccp_sk(sk);
286         if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
287             !between48(seq, dp->dccps_awl, dp->dccps_awh)) {
288                 __NET_INC_STATS(net, LINUX_MIB_OUTOFWINDOWICMPS);
289                 goto out;
290         }
291 
292         switch (type) {
293         case ICMP_REDIRECT:
294                 if (!sock_owned_by_user(sk))
295                         dccp_do_redirect(skb, sk);
296                 goto out;
297         case ICMP_SOURCE_QUENCH:
298                 /* Just silently ignore these. */
299                 goto out;
300         case ICMP_PARAMETERPROB:
301                 err = EPROTO;
302                 break;
303         case ICMP_DEST_UNREACH:
304                 if (code > NR_ICMP_UNREACH)
305                         goto out;
306 
307                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
308                         if (!sock_owned_by_user(sk))
309                                 dccp_do_pmtu_discovery(sk, iph, info);
310                         goto out;
311                 }
312 
313                 err = icmp_err_convert[code].errno;
314                 break;
315         case ICMP_TIME_EXCEEDED:
316                 err = EHOSTUNREACH;
317                 break;
318         default:
319                 goto out;
320         }
321 
322         switch (sk->sk_state) {
323         case DCCP_REQUESTING:
324         case DCCP_RESPOND:
325                 if (!sock_owned_by_user(sk)) {
326                         __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
327                         sk->sk_err = err;
328 
329                         sk->sk_error_report(sk);
330 
331                         dccp_done(sk);
332                 } else
333                         sk->sk_err_soft = err;
334                 goto out;
335         }
336 
337         /* If we've already connected we will keep trying
338          * until we time out, or the user gives up.
339          *
340          * rfc1122 4.2.3.9 allows to consider as hard errors
341          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
342          * but it is obsoleted by pmtu discovery).
343          *
344          * Note, that in modern internet, where routing is unreliable
345          * and in each dark corner broken firewalls sit, sending random
346          * errors ordered by their masters even this two messages finally lose
347          * their original sense (even Linux sends invalid PORT_UNREACHs)
348          *
349          * Now we are in compliance with RFCs.
350          *                                                      --ANK (980905)
351          */
352 
353         inet = inet_sk(sk);
354         if (!sock_owned_by_user(sk) && inet->recverr) {
355                 sk->sk_err = err;
356                 sk->sk_error_report(sk);
357         } else /* Only an error on timeout */
358                 sk->sk_err_soft = err;
359 out:
360         bh_unlock_sock(sk);
361         sock_put(sk);
362         return 0;
363 }
364 
365 static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
366                                       __be32 src, __be32 dst)
367 {
368         return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
369 }
370 
371 void dccp_v4_send_check(struct sock *sk, struct sk_buff *skb)
372 {
373         const struct inet_sock *inet = inet_sk(sk);
374         struct dccp_hdr *dh = dccp_hdr(skb);
375 
376         dccp_csum_outgoing(skb);
377         dh->dccph_checksum = dccp_v4_csum_finish(skb,
378                                                  inet->inet_saddr,
379                                                  inet->inet_daddr);
380 }
381 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
382 
383 static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
384 {
385         return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
386                                            ip_hdr(skb)->saddr,
387                                            dccp_hdr(skb)->dccph_dport,
388                                            dccp_hdr(skb)->dccph_sport);
389 }
390 
391 /*
392  * The three way handshake has completed - we got a valid ACK or DATAACK -
393  * now create the new socket.
394  *
395  * This is the equivalent of TCP's tcp_v4_syn_recv_sock
396  */
397 struct sock *dccp_v4_request_recv_sock(const struct sock *sk,
398                                        struct sk_buff *skb,
399                                        struct request_sock *req,
400                                        struct dst_entry *dst,
401                                        struct request_sock *req_unhash,
402                                        bool *own_req)
403 {
404         struct inet_request_sock *ireq;
405         struct inet_sock *newinet;
406         struct sock *newsk;
407 
408         if (sk_acceptq_is_full(sk))
409                 goto exit_overflow;
410 
411         newsk = dccp_create_openreq_child(sk, req, skb);
412         if (newsk == NULL)
413                 goto exit_nonewsk;
414 
415         newinet            = inet_sk(newsk);
416         ireq               = inet_rsk(req);
417         sk_daddr_set(newsk, ireq->ir_rmt_addr);
418         sk_rcv_saddr_set(newsk, ireq->ir_loc_addr);
419         newinet->inet_saddr     = ireq->ir_loc_addr;
420         RCU_INIT_POINTER(newinet->inet_opt, rcu_dereference(ireq->ireq_opt));
421         newinet->mc_index  = inet_iif(skb);
422         newinet->mc_ttl    = ip_hdr(skb)->ttl;
423         newinet->inet_id   = jiffies;
424 
425         if (dst == NULL && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
426                 goto put_and_exit;
427 
428         sk_setup_caps(newsk, dst);
429 
430         dccp_sync_mss(newsk, dst_mtu(dst));
431 
432         if (__inet_inherit_port(sk, newsk) < 0)
433                 goto put_and_exit;
434         *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash));
435         if (*own_req)
436                 ireq->ireq_opt = NULL;
437         else
438                 newinet->inet_opt = NULL;
439         return newsk;
440 
441 exit_overflow:
442         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
443 exit_nonewsk:
444         dst_release(dst);
445 exit:
446         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
447         return NULL;
448 put_and_exit:
449         newinet->inet_opt = NULL;
450         inet_csk_prepare_forced_close(newsk);
451         dccp_done(newsk);
452         goto exit;
453 }
454 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
455 
456 static struct dst_entry* dccp_v4_route_skb(struct net *net, struct sock *sk,
457                                            struct sk_buff *skb)
458 {
459         struct rtable *rt;
460         const struct iphdr *iph = ip_hdr(skb);
461         struct flowi4 fl4 = {
462                 .flowi4_oif = inet_iif(skb),
463                 .daddr = iph->saddr,
464                 .saddr = iph->daddr,
465                 .flowi4_tos = RT_CONN_FLAGS(sk),
466                 .flowi4_proto = sk->sk_protocol,
467                 .fl4_sport = dccp_hdr(skb)->dccph_dport,
468                 .fl4_dport = dccp_hdr(skb)->dccph_sport,
469         };
470 
471         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
472         rt = ip_route_output_flow(net, &fl4, sk);
473         if (IS_ERR(rt)) {
474                 IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
475                 return NULL;
476         }
477 
478         return &rt->dst;
479 }
480 
481 static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req)
482 {
483         int err = -1;
484         struct sk_buff *skb;
485         struct dst_entry *dst;
486         struct flowi4 fl4;
487 
488         dst = inet_csk_route_req(sk, &fl4, req);
489         if (dst == NULL)
490                 goto out;
491 
492         skb = dccp_make_response(sk, dst, req);
493         if (skb != NULL) {
494                 const struct inet_request_sock *ireq = inet_rsk(req);
495                 struct dccp_hdr *dh = dccp_hdr(skb);
496 
497                 dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->ir_loc_addr,
498                                                               ireq->ir_rmt_addr);
499                 rcu_read_lock();
500                 err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
501                                             ireq->ir_rmt_addr,
502                                             rcu_dereference(ireq->ireq_opt));
503                 rcu_read_unlock();
504                 err = net_xmit_eval(err);
505         }
506 
507 out:
508         dst_release(dst);
509         return err;
510 }
511 
512 static void dccp_v4_ctl_send_reset(const struct sock *sk, struct sk_buff *rxskb)
513 {
514         int err;
515         const struct iphdr *rxiph;
516         struct sk_buff *skb;
517         struct dst_entry *dst;
518         struct net *net = dev_net(skb_dst(rxskb)->dev);
519         struct sock *ctl_sk = net->dccp.v4_ctl_sk;
520 
521         /* Never send a reset in response to a reset. */
522         if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
523                 return;
524 
525         if (skb_rtable(rxskb)->rt_type != RTN_LOCAL)
526                 return;
527 
528         dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
529         if (dst == NULL)
530                 return;
531 
532         skb = dccp_ctl_make_reset(ctl_sk, rxskb);
533         if (skb == NULL)
534                 goto out;
535 
536         rxiph = ip_hdr(rxskb);
537         dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
538                                                                  rxiph->daddr);
539         skb_dst_set(skb, dst_clone(dst));
540 
541         local_bh_disable();
542         bh_lock_sock(ctl_sk);
543         err = ip_build_and_send_pkt(skb, ctl_sk,
544                                     rxiph->daddr, rxiph->saddr, NULL);
545         bh_unlock_sock(ctl_sk);
546 
547         if (net_xmit_eval(err) == 0) {
548                 __DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
549                 __DCCP_INC_STATS(DCCP_MIB_OUTRSTS);
550         }
551         local_bh_enable();
552 out:
553         dst_release(dst);
554 }
555 
556 static void dccp_v4_reqsk_destructor(struct request_sock *req)
557 {
558         dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
559         kfree(rcu_dereference_protected(inet_rsk(req)->ireq_opt, 1));
560 }
561 
562 void dccp_syn_ack_timeout(const struct request_sock *req)
563 {
564 }
565 EXPORT_SYMBOL(dccp_syn_ack_timeout);
566 
567 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
568         .family         = PF_INET,
569         .obj_size       = sizeof(struct dccp_request_sock),
570         .rtx_syn_ack    = dccp_v4_send_response,
571         .send_ack       = dccp_reqsk_send_ack,
572         .destructor     = dccp_v4_reqsk_destructor,
573         .send_reset     = dccp_v4_ctl_send_reset,
574         .syn_ack_timeout = dccp_syn_ack_timeout,
575 };
576 
577 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
578 {
579         struct inet_request_sock *ireq;
580         struct request_sock *req;
581         struct dccp_request_sock *dreq;
582         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
583         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
584 
585         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
586         if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
587                 return 0;       /* discard, don't send a reset here */
588 
589         if (dccp_bad_service_code(sk, service)) {
590                 dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
591                 goto drop;
592         }
593         /*
594          * TW buckets are converted to open requests without
595          * limitations, they conserve resources and peer is
596          * evidently real one.
597          */
598         dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
599         if (inet_csk_reqsk_queue_is_full(sk))
600                 goto drop;
601 
602         if (sk_acceptq_is_full(sk))
603                 goto drop;
604 
605         req = inet_reqsk_alloc(&dccp_request_sock_ops, sk, true);
606         if (req == NULL)
607                 goto drop;
608 
609         if (dccp_reqsk_init(req, dccp_sk(sk), skb))
610                 goto drop_and_free;
611 
612         dreq = dccp_rsk(req);
613         if (dccp_parse_options(sk, dreq, skb))
614                 goto drop_and_free;
615 
616         if (security_inet_conn_request(sk, skb, req))
617                 goto drop_and_free;
618 
619         ireq = inet_rsk(req);
620         sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
621         sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
622         ireq->ir_mark = inet_request_mark(sk, skb);
623         ireq->ireq_family = AF_INET;
624         ireq->ir_iif = sk->sk_bound_dev_if;
625 
626         /*
627          * Step 3: Process LISTEN state
628          *
629          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
630          *
631          * Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
632          */
633         dreq->dreq_isr     = dcb->dccpd_seq;
634         dreq->dreq_gsr     = dreq->dreq_isr;
635         dreq->dreq_iss     = dccp_v4_init_sequence(skb);
636         dreq->dreq_gss     = dreq->dreq_iss;
637         dreq->dreq_service = service;
638 
639         if (dccp_v4_send_response(sk, req))
640                 goto drop_and_free;
641 
642         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
643         reqsk_put(req);
644         return 0;
645 
646 drop_and_free:
647         reqsk_free(req);
648 drop:
649         __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
650         return -1;
651 }
652 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
653 
654 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
655 {
656         struct dccp_hdr *dh = dccp_hdr(skb);
657 
658         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
659                 if (dccp_rcv_established(sk, skb, dh, skb->len))
660                         goto reset;
661                 return 0;
662         }
663 
664         /*
665          *  Step 3: Process LISTEN state
666          *       If P.type == Request or P contains a valid Init Cookie option,
667          *            (* Must scan the packet's options to check for Init
668          *               Cookies.  Only Init Cookies are processed here,
669          *               however; other options are processed in Step 8.  This
670          *               scan need only be performed if the endpoint uses Init
671          *               Cookies *)
672          *            (* Generate a new socket and switch to that socket *)
673          *            Set S := new socket for this port pair
674          *            S.state = RESPOND
675          *            Choose S.ISS (initial seqno) or set from Init Cookies
676          *            Initialize S.GAR := S.ISS
677          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
678          *            Continue with S.state == RESPOND
679          *            (* A Response packet will be generated in Step 11 *)
680          *       Otherwise,
681          *            Generate Reset(No Connection) unless P.type == Reset
682          *            Drop packet and return
683          *
684          * NOTE: the check for the packet types is done in
685          *       dccp_rcv_state_process
686          */
687 
688         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
689                 goto reset;
690         return 0;
691 
692 reset:
693         dccp_v4_ctl_send_reset(sk, skb);
694         kfree_skb(skb);
695         return 0;
696 }
697 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
698 
699 /**
700  *      dccp_invalid_packet  -  check for malformed packets
701  *      Implements RFC 4340, 8.5:  Step 1: Check header basics
702  *      Packets that fail these checks are ignored and do not receive Resets.
703  */
704 int dccp_invalid_packet(struct sk_buff *skb)
705 {
706         const struct dccp_hdr *dh;
707         unsigned int cscov;
708         u8 dccph_doff;
709 
710         if (skb->pkt_type != PACKET_HOST)
711                 return 1;
712 
713         /* If the packet is shorter than 12 bytes, drop packet and return */
714         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
715                 DCCP_WARN("pskb_may_pull failed\n");
716                 return 1;
717         }
718 
719         dh = dccp_hdr(skb);
720 
721         /* If P.type is not understood, drop packet and return */
722         if (dh->dccph_type >= DCCP_PKT_INVALID) {
723                 DCCP_WARN("invalid packet type\n");
724                 return 1;
725         }
726 
727         /*
728          * If P.Data Offset is too small for packet type, drop packet and return
729          */
730         dccph_doff = dh->dccph_doff;
731         if (dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
732                 DCCP_WARN("P.Data Offset(%u) too small\n", dccph_doff);
733                 return 1;
734         }
735         /*
736          * If P.Data Offset is too too large for packet, drop packet and return
737          */
738         if (!pskb_may_pull(skb, dccph_doff * sizeof(u32))) {
739                 DCCP_WARN("P.Data Offset(%u) too large\n", dccph_doff);
740                 return 1;
741         }
742         dh = dccp_hdr(skb);
743         /*
744          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
745          * has short sequence numbers), drop packet and return
746          */
747         if ((dh->dccph_type < DCCP_PKT_DATA    ||
748             dh->dccph_type > DCCP_PKT_DATAACK) && dh->dccph_x == 0)  {
749                 DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
750                           dccp_packet_name(dh->dccph_type));
751                 return 1;
752         }
753 
754         /*
755          * If P.CsCov is too large for the packet size, drop packet and return.
756          * This must come _before_ checksumming (not as RFC 4340 suggests).
757          */
758         cscov = dccp_csum_coverage(skb);
759         if (cscov > skb->len) {
760                 DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
761                           dh->dccph_cscov, skb->len);
762                 return 1;
763         }
764 
765         /* If header checksum is incorrect, drop packet and return.
766          * (This step is completed in the AF-dependent functions.) */
767         skb->csum = skb_checksum(skb, 0, cscov, 0);
768 
769         return 0;
770 }
771 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
772 
773 /* this is called when real data arrives */
774 static int dccp_v4_rcv(struct sk_buff *skb)
775 {
776         const struct dccp_hdr *dh;
777         const struct iphdr *iph;
778         bool refcounted;
779         struct sock *sk;
780         int min_cov;
781 
782         /* Step 1: Check header basics */
783 
784         if (dccp_invalid_packet(skb))
785                 goto discard_it;
786 
787         iph = ip_hdr(skb);
788         /* Step 1: If header checksum is incorrect, drop packet and return */
789         if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
790                 DCCP_WARN("dropped packet with invalid checksum\n");
791                 goto discard_it;
792         }
793 
794         dh = dccp_hdr(skb);
795 
796         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
797         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
798 
799         dccp_pr_debug("%8.8s src=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
800                       dccp_packet_name(dh->dccph_type),
801                       &iph->saddr, ntohs(dh->dccph_sport),
802                       &iph->daddr, ntohs(dh->dccph_dport),
803                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
804 
805         if (dccp_packet_without_ack(skb)) {
806                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
807                 dccp_pr_debug_cat("\n");
808         } else {
809                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
810                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
811                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
812         }
813 
814 lookup:
815         sk = __inet_lookup_skb(&dccp_hashinfo, skb, __dccp_hdr_len(dh),
816                                dh->dccph_sport, dh->dccph_dport, 0, &refcounted);
817         if (!sk) {
818                 dccp_pr_debug("failed to look up flow ID in table and "
819                               "get corresponding socket\n");
820                 goto no_dccp_socket;
821         }
822 
823         /*
824          * Step 2:
825          *      ... or S.state == TIMEWAIT,
826          *              Generate Reset(No Connection) unless P.type == Reset
827          *              Drop packet and return
828          */
829         if (sk->sk_state == DCCP_TIME_WAIT) {
830                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
831                 inet_twsk_put(inet_twsk(sk));
832                 goto no_dccp_socket;
833         }
834 
835         if (sk->sk_state == DCCP_NEW_SYN_RECV) {
836                 struct request_sock *req = inet_reqsk(sk);
837                 struct sock *nsk;
838 
839                 sk = req->rsk_listener;
840                 if (unlikely(sk->sk_state != DCCP_LISTEN)) {
841                         inet_csk_reqsk_queue_drop_and_put(sk, req);
842                         goto lookup;
843                 }
844                 sock_hold(sk);
845                 refcounted = true;
846                 nsk = dccp_check_req(sk, skb, req);
847                 if (!nsk) {
848                         reqsk_put(req);
849                         goto discard_and_relse;
850                 }
851                 if (nsk == sk) {
852                         reqsk_put(req);
853                 } else if (dccp_child_process(sk, nsk, skb)) {
854                         dccp_v4_ctl_send_reset(sk, skb);
855                         goto discard_and_relse;
856                 } else {
857                         sock_put(sk);
858                         return 0;
859                 }
860         }
861         /*
862          * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
863          *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
864          *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
865          */
866         min_cov = dccp_sk(sk)->dccps_pcrlen;
867         if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
868                 dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
869                               dh->dccph_cscov, min_cov);
870                 /* FIXME: "Such packets SHOULD be reported using Data Dropped
871                  *         options (Section 11.7) with Drop Code 0, Protocol
872                  *         Constraints."                                     */
873                 goto discard_and_relse;
874         }
875 
876         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
877                 goto discard_and_relse;
878         nf_reset(skb);
879 
880         return __sk_receive_skb(sk, skb, 1, dh->dccph_doff * 4, refcounted);
881 
882 no_dccp_socket:
883         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
884                 goto discard_it;
885         /*
886          * Step 2:
887          *      If no socket ...
888          *              Generate Reset(No Connection) unless P.type == Reset
889          *              Drop packet and return
890          */
891         if (dh->dccph_type != DCCP_PKT_RESET) {
892                 DCCP_SKB_CB(skb)->dccpd_reset_code =
893                                         DCCP_RESET_CODE_NO_CONNECTION;
894                 dccp_v4_ctl_send_reset(sk, skb);
895         }
896 
897 discard_it:
898         kfree_skb(skb);
899         return 0;
900 
901 discard_and_relse:
902         if (refcounted)
903                 sock_put(sk);
904         goto discard_it;
905 }
906 
907 static const struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
908         .queue_xmit        = ip_queue_xmit,
909         .send_check        = dccp_v4_send_check,
910         .rebuild_header    = inet_sk_rebuild_header,
911         .conn_request      = dccp_v4_conn_request,
912         .syn_recv_sock     = dccp_v4_request_recv_sock,
913         .net_header_len    = sizeof(struct iphdr),
914         .setsockopt        = ip_setsockopt,
915         .getsockopt        = ip_getsockopt,
916         .addr2sockaddr     = inet_csk_addr2sockaddr,
917         .sockaddr_len      = sizeof(struct sockaddr_in),
918 #ifdef CONFIG_COMPAT
919         .compat_setsockopt = compat_ip_setsockopt,
920         .compat_getsockopt = compat_ip_getsockopt,
921 #endif
922 };
923 
924 static int dccp_v4_init_sock(struct sock *sk)
925 {
926         static __u8 dccp_v4_ctl_sock_initialized;
927         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
928 
929         if (err == 0) {
930                 if (unlikely(!dccp_v4_ctl_sock_initialized))
931                         dccp_v4_ctl_sock_initialized = 1;
932                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
933         }
934 
935         return err;
936 }
937 
938 static struct timewait_sock_ops dccp_timewait_sock_ops = {
939         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
940 };
941 
942 static struct proto dccp_v4_prot = {
943         .name                   = "DCCP",
944         .owner                  = THIS_MODULE,
945         .close                  = dccp_close,
946         .connect                = dccp_v4_connect,
947         .disconnect             = dccp_disconnect,
948         .ioctl                  = dccp_ioctl,
949         .init                   = dccp_v4_init_sock,
950         .setsockopt             = dccp_setsockopt,
951         .getsockopt             = dccp_getsockopt,
952         .sendmsg                = dccp_sendmsg,
953         .recvmsg                = dccp_recvmsg,
954         .backlog_rcv            = dccp_v4_do_rcv,
955         .hash                   = inet_hash,
956         .unhash                 = inet_unhash,
957         .accept                 = inet_csk_accept,
958         .get_port               = inet_csk_get_port,
959         .shutdown               = dccp_shutdown,
960         .destroy                = dccp_destroy_sock,
961         .orphan_count           = &dccp_orphan_count,
962         .max_header             = MAX_DCCP_HEADER,
963         .obj_size               = sizeof(struct dccp_sock),
964         .slab_flags             = SLAB_TYPESAFE_BY_RCU,
965         .rsk_prot               = &dccp_request_sock_ops,
966         .twsk_prot              = &dccp_timewait_sock_ops,
967         .h.hashinfo             = &dccp_hashinfo,
968 #ifdef CONFIG_COMPAT
969         .compat_setsockopt      = compat_dccp_setsockopt,
970         .compat_getsockopt      = compat_dccp_getsockopt,
971 #endif
972 };
973 
974 static const struct net_protocol dccp_v4_protocol = {
975         .handler        = dccp_v4_rcv,
976         .err_handler    = dccp_v4_err,
977         .no_policy      = 1,
978         .netns_ok       = 1,
979         .icmp_strict_tag_validation = 1,
980 };
981 
982 static const struct proto_ops inet_dccp_ops = {
983         .family            = PF_INET,
984         .owner             = THIS_MODULE,
985         .release           = inet_release,
986         .bind              = inet_bind,
987         .connect           = inet_stream_connect,
988         .socketpair        = sock_no_socketpair,
989         .accept            = inet_accept,
990         .getname           = inet_getname,
991         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
992         .poll              = dccp_poll,
993         .ioctl             = inet_ioctl,
994         /* FIXME: work on inet_listen to rename it to sock_common_listen */
995         .listen            = inet_dccp_listen,
996         .shutdown          = inet_shutdown,
997         .setsockopt        = sock_common_setsockopt,
998         .getsockopt        = sock_common_getsockopt,
999         .sendmsg           = inet_sendmsg,
1000         .recvmsg           = sock_common_recvmsg,
1001         .mmap              = sock_no_mmap,
1002         .sendpage          = sock_no_sendpage,
1003 #ifdef CONFIG_COMPAT
1004         .compat_setsockopt = compat_sock_common_setsockopt,
1005         .compat_getsockopt = compat_sock_common_getsockopt,
1006 #endif
1007 };
1008 
1009 static struct inet_protosw dccp_v4_protosw = {
1010         .type           = SOCK_DCCP,
1011         .protocol       = IPPROTO_DCCP,
1012         .prot           = &dccp_v4_prot,
1013         .ops            = &inet_dccp_ops,
1014         .flags          = INET_PROTOSW_ICSK,
1015 };
1016 
1017 static int __net_init dccp_v4_init_net(struct net *net)
1018 {
1019         if (dccp_hashinfo.bhash == NULL)
1020                 return -ESOCKTNOSUPPORT;
1021 
1022         return inet_ctl_sock_create(&net->dccp.v4_ctl_sk, PF_INET,
1023                                     SOCK_DCCP, IPPROTO_DCCP, net);
1024 }
1025 
1026 static void __net_exit dccp_v4_exit_net(struct net *net)
1027 {
1028         inet_ctl_sock_destroy(net->dccp.v4_ctl_sk);
1029 }
1030 
1031 static void __net_exit dccp_v4_exit_batch(struct list_head *net_exit_list)
1032 {
1033         inet_twsk_purge(&dccp_hashinfo, AF_INET);
1034 }
1035 
1036 static struct pernet_operations dccp_v4_ops = {
1037         .init   = dccp_v4_init_net,
1038         .exit   = dccp_v4_exit_net,
1039         .exit_batch = dccp_v4_exit_batch,
1040 };
1041 
1042 static int __init dccp_v4_init(void)
1043 {
1044         int err = proto_register(&dccp_v4_prot, 1);
1045 
1046         if (err)
1047                 goto out;
1048 
1049         inet_register_protosw(&dccp_v4_protosw);
1050 
1051         err = register_pernet_subsys(&dccp_v4_ops);
1052         if (err)
1053                 goto out_destroy_ctl_sock;
1054 
1055         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1056         if (err)
1057                 goto out_proto_unregister;
1058 
1059 out:
1060         return err;
1061 out_proto_unregister:
1062         unregister_pernet_subsys(&dccp_v4_ops);
1063 out_destroy_ctl_sock:
1064         inet_unregister_protosw(&dccp_v4_protosw);
1065         proto_unregister(&dccp_v4_prot);
1066         goto out;
1067 }
1068 
1069 static void __exit dccp_v4_exit(void)
1070 {
1071         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1072         unregister_pernet_subsys(&dccp_v4_ops);
1073         inet_unregister_protosw(&dccp_v4_protosw);
1074         proto_unregister(&dccp_v4_prot);
1075 }
1076 
1077 module_init(dccp_v4_init);
1078 module_exit(dccp_v4_exit);
1079 
1080 /*
1081  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1082  * values directly, Also cover the case where the protocol is not specified,
1083  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1084  */
1085 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
1086 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
1087 MODULE_LICENSE("GPL");
1088 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1089 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");
1090 

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