2c628281526473ef0b268c73b85b0a40b227b415
[linux-2.6.git] / net / dccp / ipv4.c
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/module.h>
16 #include <linux/skbuff.h>
17 #include <linux/random.h>
18
19 #include <net/icmp.h>
20 #include <net/inet_common.h>
21 #include <net/inet_hashtables.h>
22 #include <net/inet_sock.h>
23 #include <net/protocol.h>
24 #include <net/sock.h>
25 #include <net/timewait_sock.h>
26 #include <net/tcp_states.h>
27 #include <net/xfrm.h>
28
29 #include "ackvec.h"
30 #include "ccid.h"
31 #include "dccp.h"
32 #include "feat.h"
33
34 /*
35  * This is the global socket data structure used for responding to
36  * the Out-of-the-blue (OOTB) packets. A control sock will be created
37  * for this socket at the initialization time.
38  */
39 static struct socket *dccp_v4_ctl_socket;
40
41 static int dccp_v4_get_port(struct sock *sk, const unsigned short snum)
42 {
43         return inet_csk_get_port(&dccp_hashinfo, sk, snum,
44                                  inet_csk_bind_conflict);
45 }
46
47 int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
48 {
49         struct inet_sock *inet = inet_sk(sk);
50         struct dccp_sock *dp = dccp_sk(sk);
51         const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
52         struct rtable *rt;
53         __be32 daddr, nexthop;
54         int tmp;
55         int err;
56
57         dp->dccps_role = DCCP_ROLE_CLIENT;
58
59         if (addr_len < sizeof(struct sockaddr_in))
60                 return -EINVAL;
61
62         if (usin->sin_family != AF_INET)
63                 return -EAFNOSUPPORT;
64
65         nexthop = daddr = usin->sin_addr.s_addr;
66         if (inet->opt != NULL && inet->opt->srr) {
67                 if (daddr == 0)
68                         return -EINVAL;
69                 nexthop = inet->opt->faddr;
70         }
71
72         tmp = ip_route_connect(&rt, nexthop, inet->saddr,
73                                RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
74                                IPPROTO_DCCP,
75                                inet->sport, usin->sin_port, sk, 1);
76         if (tmp < 0)
77                 return tmp;
78
79         if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
80                 ip_rt_put(rt);
81                 return -ENETUNREACH;
82         }
83
84         if (inet->opt == NULL || !inet->opt->srr)
85                 daddr = rt->rt_dst;
86
87         if (inet->saddr == 0)
88                 inet->saddr = rt->rt_src;
89         inet->rcv_saddr = inet->saddr;
90
91         inet->dport = usin->sin_port;
92         inet->daddr = daddr;
93
94         inet_csk(sk)->icsk_ext_hdr_len = 0;
95         if (inet->opt != NULL)
96                 inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;
97         /*
98          * Socket identity is still unknown (sport may be zero).
99          * However we set state to DCCP_REQUESTING and not releasing socket
100          * lock select source port, enter ourselves into the hash tables and
101          * complete initialization after this.
102          */
103         dccp_set_state(sk, DCCP_REQUESTING);
104         err = inet_hash_connect(&dccp_death_row, sk);
105         if (err != 0)
106                 goto failure;
107
108         err = ip_route_newports(&rt, IPPROTO_DCCP, inet->sport, inet->dport,
109                                 sk);
110         if (err != 0)
111                 goto failure;
112
113         /* OK, now commit destination to socket.  */
114         sk_setup_caps(sk, &rt->u.dst);
115
116         dp->dccps_iss = secure_dccp_sequence_number(inet->saddr, inet->daddr,
117                                                     inet->sport, inet->dport);
118         inet->id = dp->dccps_iss ^ jiffies;
119
120         err = dccp_connect(sk);
121         rt = NULL;
122         if (err != 0)
123                 goto failure;
124 out:
125         return err;
126 failure:
127         /*
128          * This unhashes the socket and releases the local port, if necessary.
129          */
130         dccp_set_state(sk, DCCP_CLOSED);
131         ip_rt_put(rt);
132         sk->sk_route_caps = 0;
133         inet->dport = 0;
134         goto out;
135 }
136
137 EXPORT_SYMBOL_GPL(dccp_v4_connect);
138
139 /*
140  * This routine does path mtu discovery as defined in RFC1191.
141  */
142 static inline void dccp_do_pmtu_discovery(struct sock *sk,
143                                           const struct iphdr *iph,
144                                           u32 mtu)
145 {
146         struct dst_entry *dst;
147         const struct inet_sock *inet = inet_sk(sk);
148         const struct dccp_sock *dp = dccp_sk(sk);
149
150         /* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
151          * send out by Linux are always < 576bytes so they should go through
152          * unfragmented).
153          */
154         if (sk->sk_state == DCCP_LISTEN)
155                 return;
156
157         /* We don't check in the destentry if pmtu discovery is forbidden
158          * on this route. We just assume that no packet_to_big packets
159          * are send back when pmtu discovery is not active.
160          * There is a small race when the user changes this flag in the
161          * route, but I think that's acceptable.
162          */
163         if ((dst = __sk_dst_check(sk, 0)) == NULL)
164                 return;
165
166         dst->ops->update_pmtu(dst, mtu);
167
168         /* Something is about to be wrong... Remember soft error
169          * for the case, if this connection will not able to recover.
170          */
171         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
172                 sk->sk_err_soft = EMSGSIZE;
173
174         mtu = dst_mtu(dst);
175
176         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
177             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
178                 dccp_sync_mss(sk, mtu);
179
180                 /*
181                  * From RFC 4340, sec. 14.1:
182                  *
183                  *      DCCP-Sync packets are the best choice for upward
184                  *      probing, since DCCP-Sync probes do not risk application
185                  *      data loss.
186                  */
187                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
188         } /* else let the usual retransmit timer handle it */
189 }
190
191 /*
192  * This routine is called by the ICMP module when it gets some sort of error
193  * condition. If err < 0 then the socket should be closed and the error
194  * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
195  * After adjustment header points to the first 8 bytes of the tcp header. We
196  * need to find the appropriate port.
197  *
198  * The locking strategy used here is very "optimistic". When someone else
199  * accesses the socket the ICMP is just dropped and for some paths there is no
200  * check at all. A more general error queue to queue errors for later handling
201  * is probably better.
202  */
203 static void dccp_v4_err(struct sk_buff *skb, u32 info)
204 {
205         const struct iphdr *iph = (struct iphdr *)skb->data;
206         const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data +
207                                                         (iph->ihl << 2));
208         struct dccp_sock *dp;
209         struct inet_sock *inet;
210         const int type = icmp_hdr(skb)->type;
211         const int code = icmp_hdr(skb)->code;
212         struct sock *sk;
213         __u64 seq;
214         int err;
215
216         if (skb->len < (iph->ihl << 2) + 8) {
217                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
218                 return;
219         }
220
221         sk = inet_lookup(&dccp_hashinfo, iph->daddr, dh->dccph_dport,
222                          iph->saddr, dh->dccph_sport, inet_iif(skb));
223         if (sk == NULL) {
224                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
225                 return;
226         }
227
228         if (sk->sk_state == DCCP_TIME_WAIT) {
229                 inet_twsk_put(inet_twsk(sk));
230                 return;
231         }
232
233         bh_lock_sock(sk);
234         /* If too many ICMPs get dropped on busy
235          * servers this needs to be solved differently.
236          */
237         if (sock_owned_by_user(sk))
238                 NET_INC_STATS_BH(LINUX_MIB_LOCKDROPPEDICMPS);
239
240         if (sk->sk_state == DCCP_CLOSED)
241                 goto out;
242
243         dp = dccp_sk(sk);
244         seq = dccp_hdr_seq(skb);
245         if (sk->sk_state != DCCP_LISTEN &&
246             !between48(seq, dp->dccps_swl, dp->dccps_swh)) {
247                 NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
248                 goto out;
249         }
250
251         switch (type) {
252         case ICMP_SOURCE_QUENCH:
253                 /* Just silently ignore these. */
254                 goto out;
255         case ICMP_PARAMETERPROB:
256                 err = EPROTO;
257                 break;
258         case ICMP_DEST_UNREACH:
259                 if (code > NR_ICMP_UNREACH)
260                         goto out;
261
262                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
263                         if (!sock_owned_by_user(sk))
264                                 dccp_do_pmtu_discovery(sk, iph, info);
265                         goto out;
266                 }
267
268                 err = icmp_err_convert[code].errno;
269                 break;
270         case ICMP_TIME_EXCEEDED:
271                 err = EHOSTUNREACH;
272                 break;
273         default:
274                 goto out;
275         }
276
277         switch (sk->sk_state) {
278                 struct request_sock *req , **prev;
279         case DCCP_LISTEN:
280                 if (sock_owned_by_user(sk))
281                         goto out;
282                 req = inet_csk_search_req(sk, &prev, dh->dccph_dport,
283                                           iph->daddr, iph->saddr);
284                 if (!req)
285                         goto out;
286
287                 /*
288                  * ICMPs are not backlogged, hence we cannot get an established
289                  * socket here.
290                  */
291                 BUG_TRAP(!req->sk);
292
293                 if (seq != dccp_rsk(req)->dreq_iss) {
294                         NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
295                         goto out;
296                 }
297                 /*
298                  * Still in RESPOND, just remove it silently.
299                  * There is no good way to pass the error to the newly
300                  * created socket, and POSIX does not want network
301                  * errors returned from accept().
302                  */
303                 inet_csk_reqsk_queue_drop(sk, req, prev);
304                 goto out;
305
306         case DCCP_REQUESTING:
307         case DCCP_RESPOND:
308                 if (!sock_owned_by_user(sk)) {
309                         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
310                         sk->sk_err = err;
311
312                         sk->sk_error_report(sk);
313
314                         dccp_done(sk);
315                 } else
316                         sk->sk_err_soft = err;
317                 goto out;
318         }
319
320         /* If we've already connected we will keep trying
321          * until we time out, or the user gives up.
322          *
323          * rfc1122 4.2.3.9 allows to consider as hard errors
324          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
325          * but it is obsoleted by pmtu discovery).
326          *
327          * Note, that in modern internet, where routing is unreliable
328          * and in each dark corner broken firewalls sit, sending random
329          * errors ordered by their masters even this two messages finally lose
330          * their original sense (even Linux sends invalid PORT_UNREACHs)
331          *
332          * Now we are in compliance with RFCs.
333          *                                                      --ANK (980905)
334          */
335
336         inet = inet_sk(sk);
337         if (!sock_owned_by_user(sk) && inet->recverr) {
338                 sk->sk_err = err;
339                 sk->sk_error_report(sk);
340         } else /* Only an error on timeout */
341                 sk->sk_err_soft = err;
342 out:
343         bh_unlock_sock(sk);
344         sock_put(sk);
345 }
346
347 static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
348                                       __be32 src, __be32 dst)
349 {
350         return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
351 }
352
353 void dccp_v4_send_check(struct sock *sk, int unused, struct sk_buff *skb)
354 {
355         const struct inet_sock *inet = inet_sk(sk);
356         struct dccp_hdr *dh = dccp_hdr(skb);
357
358         dccp_csum_outgoing(skb);
359         dh->dccph_checksum = dccp_v4_csum_finish(skb, inet->saddr, inet->daddr);
360 }
361
362 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
363
364 static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
365 {
366         return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
367                                            ip_hdr(skb)->saddr,
368                                            dccp_hdr(skb)->dccph_dport,
369                                            dccp_hdr(skb)->dccph_sport);
370 }
371
372 /*
373  * The three way handshake has completed - we got a valid ACK or DATAACK -
374  * now create the new socket.
375  *
376  * This is the equivalent of TCP's tcp_v4_syn_recv_sock
377  */
378 struct sock *dccp_v4_request_recv_sock(struct sock *sk, struct sk_buff *skb,
379                                        struct request_sock *req,
380                                        struct dst_entry *dst)
381 {
382         struct inet_request_sock *ireq;
383         struct inet_sock *newinet;
384         struct sock *newsk;
385
386         if (sk_acceptq_is_full(sk))
387                 goto exit_overflow;
388
389         if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
390                 goto exit;
391
392         newsk = dccp_create_openreq_child(sk, req, skb);
393         if (newsk == NULL)
394                 goto exit;
395
396         sk_setup_caps(newsk, dst);
397
398         newinet            = inet_sk(newsk);
399         ireq               = inet_rsk(req);
400         newinet->daddr     = ireq->rmt_addr;
401         newinet->rcv_saddr = ireq->loc_addr;
402         newinet->saddr     = ireq->loc_addr;
403         newinet->opt       = ireq->opt;
404         ireq->opt          = NULL;
405         newinet->mc_index  = inet_iif(skb);
406         newinet->mc_ttl    = ip_hdr(skb)->ttl;
407         newinet->id        = jiffies;
408
409         dccp_sync_mss(newsk, dst_mtu(dst));
410
411         __inet_hash(&dccp_hashinfo, newsk, 0);
412         __inet_inherit_port(&dccp_hashinfo, sk, newsk);
413
414         return newsk;
415
416 exit_overflow:
417         NET_INC_STATS_BH(LINUX_MIB_LISTENOVERFLOWS);
418 exit:
419         NET_INC_STATS_BH(LINUX_MIB_LISTENDROPS);
420         dst_release(dst);
421         return NULL;
422 }
423
424 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
425
426 static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
427 {
428         const struct dccp_hdr *dh = dccp_hdr(skb);
429         const struct iphdr *iph = ip_hdr(skb);
430         struct sock *nsk;
431         struct request_sock **prev;
432         /* Find possible connection requests. */
433         struct request_sock *req = inet_csk_search_req(sk, &prev,
434                                                        dh->dccph_sport,
435                                                        iph->saddr, iph->daddr);
436         if (req != NULL)
437                 return dccp_check_req(sk, skb, req, prev);
438
439         nsk = inet_lookup_established(&dccp_hashinfo,
440                                       iph->saddr, dh->dccph_sport,
441                                       iph->daddr, dh->dccph_dport,
442                                       inet_iif(skb));
443         if (nsk != NULL) {
444                 if (nsk->sk_state != DCCP_TIME_WAIT) {
445                         bh_lock_sock(nsk);
446                         return nsk;
447                 }
448                 inet_twsk_put(inet_twsk(nsk));
449                 return NULL;
450         }
451
452         return sk;
453 }
454
455 static struct dst_entry* dccp_v4_route_skb(struct sock *sk,
456                                            struct sk_buff *skb)
457 {
458         struct rtable *rt;
459         struct flowi fl = { .oif = ((struct rtable *)skb->dst)->rt_iif,
460                             .nl_u = { .ip4_u =
461                                       { .daddr = ip_hdr(skb)->saddr,
462                                         .saddr = ip_hdr(skb)->daddr,
463                                         .tos = RT_CONN_FLAGS(sk) } },
464                             .proto = sk->sk_protocol,
465                             .uli_u = { .ports =
466                                        { .sport = dccp_hdr(skb)->dccph_dport,
467                                          .dport = dccp_hdr(skb)->dccph_sport }
468                                      }
469                           };
470
471         security_skb_classify_flow(skb, &fl);
472         if (ip_route_output_flow(&rt, &fl, sk, 0)) {
473                 IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
474                 return NULL;
475         }
476
477         return &rt->u.dst;
478 }
479
480 static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
481                                  struct dst_entry *dst)
482 {
483         int err = -1;
484         struct sk_buff *skb;
485
486         /* First, grab a route. */
487
488         if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
489                 goto out;
490
491         skb = dccp_make_response(sk, dst, req);
492         if (skb != NULL) {
493                 const struct inet_request_sock *ireq = inet_rsk(req);
494                 struct dccp_hdr *dh = dccp_hdr(skb);
495
496                 dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->loc_addr,
497                                                               ireq->rmt_addr);
498                 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
499                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
500                                             ireq->rmt_addr,
501                                             ireq->opt);
502                 err = net_xmit_eval(err);
503         }
504
505 out:
506         dst_release(dst);
507         return err;
508 }
509
510 static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
511 {
512         int err;
513         struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
514         const struct iphdr *rxiph;
515         const int dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
516                                        sizeof(struct dccp_hdr_ext) +
517                                        sizeof(struct dccp_hdr_reset);
518         struct sk_buff *skb;
519         struct dst_entry *dst;
520         u64 seqno = 0;
521
522         /* Never send a reset in response to a reset. */
523         if (rxdh->dccph_type == DCCP_PKT_RESET)
524                 return;
525
526         if (((struct rtable *)rxskb->dst)->rt_type != RTN_LOCAL)
527                 return;
528
529         dst = dccp_v4_route_skb(dccp_v4_ctl_socket->sk, rxskb);
530         if (dst == NULL)
531                 return;
532
533         skb = alloc_skb(dccp_v4_ctl_socket->sk->sk_prot->max_header,
534                         GFP_ATOMIC);
535         if (skb == NULL)
536                 goto out;
537
538         /* Reserve space for headers. */
539         skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
540         skb->dst = dst_clone(dst);
541
542         dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
543
544         /* Build DCCP header and checksum it. */
545         dh->dccph_type     = DCCP_PKT_RESET;
546         dh->dccph_sport    = rxdh->dccph_dport;
547         dh->dccph_dport    = rxdh->dccph_sport;
548         dh->dccph_doff     = dccp_hdr_reset_len / 4;
549         dh->dccph_x        = 1;
550         dccp_hdr_reset(skb)->dccph_reset_code =
551                                 DCCP_SKB_CB(rxskb)->dccpd_reset_code;
552
553         /* See "8.3.1. Abnormal Termination" in RFC 4340 */
554         if (DCCP_SKB_CB(rxskb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
555                 dccp_set_seqno(&seqno, DCCP_SKB_CB(rxskb)->dccpd_ack_seq + 1);
556
557         dccp_hdr_set_seq(dh, seqno);
558         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), DCCP_SKB_CB(rxskb)->dccpd_seq);
559
560         dccp_csum_outgoing(skb);
561         rxiph = ip_hdr(rxskb);
562         dh->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
563                                                  rxiph->daddr);
564
565         bh_lock_sock(dccp_v4_ctl_socket->sk);
566         err = ip_build_and_send_pkt(skb, dccp_v4_ctl_socket->sk,
567                                     rxiph->daddr, rxiph->saddr, NULL);
568         bh_unlock_sock(dccp_v4_ctl_socket->sk);
569
570         if (net_xmit_eval(err) == 0) {
571                 DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
572                 DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
573         }
574 out:
575          dst_release(dst);
576 }
577
578 static void dccp_v4_reqsk_destructor(struct request_sock *req)
579 {
580         kfree(inet_rsk(req)->opt);
581 }
582
583 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
584         .family         = PF_INET,
585         .obj_size       = sizeof(struct dccp_request_sock),
586         .rtx_syn_ack    = dccp_v4_send_response,
587         .send_ack       = dccp_reqsk_send_ack,
588         .destructor     = dccp_v4_reqsk_destructor,
589         .send_reset     = dccp_v4_ctl_send_reset,
590 };
591
592 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
593 {
594         struct inet_request_sock *ireq;
595         struct request_sock *req;
596         struct dccp_request_sock *dreq;
597         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
598         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
599         __u8 reset_code = DCCP_RESET_CODE_TOO_BUSY;
600
601         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
602         if (((struct rtable *)skb->dst)->rt_flags &
603             (RTCF_BROADCAST | RTCF_MULTICAST)) {
604                 reset_code = DCCP_RESET_CODE_NO_CONNECTION;
605                 goto drop;
606         }
607
608         if (dccp_bad_service_code(sk, service)) {
609                 reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
610                 goto drop;
611         }
612         /*
613          * TW buckets are converted to open requests without
614          * limitations, they conserve resources and peer is
615          * evidently real one.
616          */
617         if (inet_csk_reqsk_queue_is_full(sk))
618                 goto drop;
619
620         /*
621          * Accept backlog is full. If we have already queued enough
622          * of warm entries in syn queue, drop request. It is better than
623          * clogging syn queue with openreqs with exponentially increasing
624          * timeout.
625          */
626         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
627                 goto drop;
628
629         req = reqsk_alloc(&dccp_request_sock_ops);
630         if (req == NULL)
631                 goto drop;
632
633         if (dccp_parse_options(sk, skb))
634                 goto drop_and_free;
635
636         dccp_reqsk_init(req, skb);
637
638         if (security_inet_conn_request(sk, skb, req))
639                 goto drop_and_free;
640
641         ireq = inet_rsk(req);
642         ireq->loc_addr = ip_hdr(skb)->daddr;
643         ireq->rmt_addr = ip_hdr(skb)->saddr;
644         ireq->opt       = NULL;
645
646         /*
647          * Step 3: Process LISTEN state
648          *
649          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
650          *
651          * In fact we defer setting S.GSR, S.SWL, S.SWH to
652          * dccp_create_openreq_child.
653          */
654         dreq = dccp_rsk(req);
655         dreq->dreq_isr     = dcb->dccpd_seq;
656         dreq->dreq_iss     = dccp_v4_init_sequence(skb);
657         dreq->dreq_service = service;
658
659         if (dccp_v4_send_response(sk, req, NULL))
660                 goto drop_and_free;
661
662         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
663         return 0;
664
665 drop_and_free:
666         reqsk_free(req);
667 drop:
668         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
669         dcb->dccpd_reset_code = reset_code;
670         return -1;
671 }
672
673 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
674
675 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
676 {
677         struct dccp_hdr *dh = dccp_hdr(skb);
678
679         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
680                 if (dccp_rcv_established(sk, skb, dh, skb->len))
681                         goto reset;
682                 return 0;
683         }
684
685         /*
686          *  Step 3: Process LISTEN state
687          *       If P.type == Request or P contains a valid Init Cookie option,
688          *            (* Must scan the packet's options to check for Init
689          *               Cookies.  Only Init Cookies are processed here,
690          *               however; other options are processed in Step 8.  This
691          *               scan need only be performed if the endpoint uses Init
692          *               Cookies *)
693          *            (* Generate a new socket and switch to that socket *)
694          *            Set S := new socket for this port pair
695          *            S.state = RESPOND
696          *            Choose S.ISS (initial seqno) or set from Init Cookies
697          *            Initialize S.GAR := S.ISS
698          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
699          *            Continue with S.state == RESPOND
700          *            (* A Response packet will be generated in Step 11 *)
701          *       Otherwise,
702          *            Generate Reset(No Connection) unless P.type == Reset
703          *            Drop packet and return
704          *
705          * NOTE: the check for the packet types is done in
706          *       dccp_rcv_state_process
707          */
708         if (sk->sk_state == DCCP_LISTEN) {
709                 struct sock *nsk = dccp_v4_hnd_req(sk, skb);
710
711                 if (nsk == NULL)
712                         goto discard;
713
714                 if (nsk != sk) {
715                         if (dccp_child_process(sk, nsk, skb))
716                                 goto reset;
717                         return 0;
718                 }
719         }
720
721         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
722                 goto reset;
723         return 0;
724
725 reset:
726         dccp_v4_ctl_send_reset(sk, skb);
727 discard:
728         kfree_skb(skb);
729         return 0;
730 }
731
732 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
733
734 /**
735  *      dccp_invalid_packet  -  check for malformed packets
736  *      Implements RFC 4340, 8.5:  Step 1: Check header basics
737  *      Packets that fail these checks are ignored and do not receive Resets.
738  */
739 int dccp_invalid_packet(struct sk_buff *skb)
740 {
741         const struct dccp_hdr *dh;
742         unsigned int cscov;
743
744         if (skb->pkt_type != PACKET_HOST)
745                 return 1;
746
747         /* If the packet is shorter than 12 bytes, drop packet and return */
748         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
749                 DCCP_WARN("pskb_may_pull failed\n");
750                 return 1;
751         }
752
753         dh = dccp_hdr(skb);
754
755         /* If P.type is not understood, drop packet and return */
756         if (dh->dccph_type >= DCCP_PKT_INVALID) {
757                 DCCP_WARN("invalid packet type\n");
758                 return 1;
759         }
760
761         /*
762          * If P.Data Offset is too small for packet type, drop packet and return
763          */
764         if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
765                 DCCP_WARN("P.Data Offset(%u) too small\n", dh->dccph_doff);
766                 return 1;
767         }
768         /*
769          * If P.Data Offset is too too large for packet, drop packet and return
770          */
771         if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
772                 DCCP_WARN("P.Data Offset(%u) too large\n", dh->dccph_doff);
773                 return 1;
774         }
775
776         /*
777          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
778          * has short sequence numbers), drop packet and return
779          */
780         if (dh->dccph_type >= DCCP_PKT_DATA    &&
781             dh->dccph_type <= DCCP_PKT_DATAACK && dh->dccph_x == 0)  {
782                 DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
783                           dccp_packet_name(dh->dccph_type));
784                 return 1;
785         }
786
787         /*
788          * If P.CsCov is too large for the packet size, drop packet and return.
789          * This must come _before_ checksumming (not as RFC 4340 suggests).
790          */
791         cscov = dccp_csum_coverage(skb);
792         if (cscov > skb->len) {
793                 DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
794                           dh->dccph_cscov, skb->len);
795                 return 1;
796         }
797
798         /* If header checksum is incorrect, drop packet and return.
799          * (This step is completed in the AF-dependent functions.) */
800         skb->csum = skb_checksum(skb, 0, cscov, 0);
801
802         return 0;
803 }
804
805 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
806
807 /* this is called when real data arrives */
808 static int dccp_v4_rcv(struct sk_buff *skb)
809 {
810         const struct dccp_hdr *dh;
811         const struct iphdr *iph;
812         struct sock *sk;
813         int min_cov;
814
815         /* Step 1: Check header basics */
816
817         if (dccp_invalid_packet(skb))
818                 goto discard_it;
819
820         iph = ip_hdr(skb);
821         /* Step 1: If header checksum is incorrect, drop packet and return */
822         if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
823                 DCCP_WARN("dropped packet with invalid checksum\n");
824                 goto discard_it;
825         }
826
827         dh = dccp_hdr(skb);
828
829         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(skb);
830         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
831
832         dccp_pr_debug("%8.8s "
833                       "src=%u.%u.%u.%u@%-5d "
834                       "dst=%u.%u.%u.%u@%-5d seq=%llu",
835                       dccp_packet_name(dh->dccph_type),
836                       NIPQUAD(iph->saddr), ntohs(dh->dccph_sport),
837                       NIPQUAD(iph->daddr), ntohs(dh->dccph_dport),
838                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
839
840         if (dccp_packet_without_ack(skb)) {
841                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
842                 dccp_pr_debug_cat("\n");
843         } else {
844                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
845                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
846                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
847         }
848
849         /* Step 2:
850          *      Look up flow ID in table and get corresponding socket */
851         sk = __inet_lookup(&dccp_hashinfo,
852                            iph->saddr, dh->dccph_sport,
853                            iph->daddr, dh->dccph_dport, inet_iif(skb));
854         /*
855          * Step 2:
856          *      If no socket ...
857          */
858         if (sk == NULL) {
859                 dccp_pr_debug("failed to look up flow ID in table and "
860                               "get corresponding socket\n");
861                 goto no_dccp_socket;
862         }
863
864         /*
865          * Step 2:
866          *      ... or S.state == TIMEWAIT,
867          *              Generate Reset(No Connection) unless P.type == Reset
868          *              Drop packet and return
869          */
870         if (sk->sk_state == DCCP_TIME_WAIT) {
871                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
872                 inet_twsk_put(inet_twsk(sk));
873                 goto no_dccp_socket;
874         }
875
876         /*
877          * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
878          *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
879          *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
880          */
881         min_cov = dccp_sk(sk)->dccps_pcrlen;
882         if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
883                 dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
884                               dh->dccph_cscov, min_cov);
885                 /* FIXME: "Such packets SHOULD be reported using Data Dropped
886                  *         options (Section 11.7) with Drop Code 0, Protocol
887                  *         Constraints."                                     */
888                 goto discard_and_relse;
889         }
890
891         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
892                 goto discard_and_relse;
893         nf_reset(skb);
894
895         return sk_receive_skb(sk, skb, 1);
896
897 no_dccp_socket:
898         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
899                 goto discard_it;
900         /*
901          * Step 2:
902          *      If no socket ...
903          *              Generate Reset(No Connection) unless P.type == Reset
904          *              Drop packet and return
905          */
906         if (dh->dccph_type != DCCP_PKT_RESET) {
907                 DCCP_SKB_CB(skb)->dccpd_reset_code =
908                                         DCCP_RESET_CODE_NO_CONNECTION;
909                 dccp_v4_ctl_send_reset(sk, skb);
910         }
911
912 discard_it:
913         kfree_skb(skb);
914         return 0;
915
916 discard_and_relse:
917         sock_put(sk);
918         goto discard_it;
919 }
920
921 static struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
922         .queue_xmit        = ip_queue_xmit,
923         .send_check        = dccp_v4_send_check,
924         .rebuild_header    = inet_sk_rebuild_header,
925         .conn_request      = dccp_v4_conn_request,
926         .syn_recv_sock     = dccp_v4_request_recv_sock,
927         .net_header_len    = sizeof(struct iphdr),
928         .setsockopt        = ip_setsockopt,
929         .getsockopt        = ip_getsockopt,
930         .addr2sockaddr     = inet_csk_addr2sockaddr,
931         .sockaddr_len      = sizeof(struct sockaddr_in),
932 #ifdef CONFIG_COMPAT
933         .compat_setsockopt = compat_ip_setsockopt,
934         .compat_getsockopt = compat_ip_getsockopt,
935 #endif
936 };
937
938 static int dccp_v4_init_sock(struct sock *sk)
939 {
940         static __u8 dccp_v4_ctl_sock_initialized;
941         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
942
943         if (err == 0) {
944                 if (unlikely(!dccp_v4_ctl_sock_initialized))
945                         dccp_v4_ctl_sock_initialized = 1;
946                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
947         }
948
949         return err;
950 }
951
952 static struct timewait_sock_ops dccp_timewait_sock_ops = {
953         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
954 };
955
956 static struct proto dccp_v4_prot = {
957         .name                   = "DCCP",
958         .owner                  = THIS_MODULE,
959         .close                  = dccp_close,
960         .connect                = dccp_v4_connect,
961         .disconnect             = dccp_disconnect,
962         .ioctl                  = dccp_ioctl,
963         .init                   = dccp_v4_init_sock,
964         .setsockopt             = dccp_setsockopt,
965         .getsockopt             = dccp_getsockopt,
966         .sendmsg                = dccp_sendmsg,
967         .recvmsg                = dccp_recvmsg,
968         .backlog_rcv            = dccp_v4_do_rcv,
969         .hash                   = dccp_hash,
970         .unhash                 = dccp_unhash,
971         .accept                 = inet_csk_accept,
972         .get_port               = dccp_v4_get_port,
973         .shutdown               = dccp_shutdown,
974         .destroy                = dccp_destroy_sock,
975         .orphan_count           = &dccp_orphan_count,
976         .max_header             = MAX_DCCP_HEADER,
977         .obj_size               = sizeof(struct dccp_sock),
978         .rsk_prot               = &dccp_request_sock_ops,
979         .twsk_prot              = &dccp_timewait_sock_ops,
980 #ifdef CONFIG_COMPAT
981         .compat_setsockopt      = compat_dccp_setsockopt,
982         .compat_getsockopt      = compat_dccp_getsockopt,
983 #endif
984 };
985
986 static struct net_protocol dccp_v4_protocol = {
987         .handler        = dccp_v4_rcv,
988         .err_handler    = dccp_v4_err,
989         .no_policy      = 1,
990 };
991
992 static const struct proto_ops inet_dccp_ops = {
993         .family            = PF_INET,
994         .owner             = THIS_MODULE,
995         .release           = inet_release,
996         .bind              = inet_bind,
997         .connect           = inet_stream_connect,
998         .socketpair        = sock_no_socketpair,
999         .accept            = inet_accept,
1000         .getname           = inet_getname,
1001         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
1002         .poll              = dccp_poll,
1003         .ioctl             = inet_ioctl,
1004         /* FIXME: work on inet_listen to rename it to sock_common_listen */
1005         .listen            = inet_dccp_listen,
1006         .shutdown          = inet_shutdown,
1007         .setsockopt        = sock_common_setsockopt,
1008         .getsockopt        = sock_common_getsockopt,
1009         .sendmsg           = inet_sendmsg,
1010         .recvmsg           = sock_common_recvmsg,
1011         .mmap              = sock_no_mmap,
1012         .sendpage          = sock_no_sendpage,
1013 #ifdef CONFIG_COMPAT
1014         .compat_setsockopt = compat_sock_common_setsockopt,
1015         .compat_getsockopt = compat_sock_common_getsockopt,
1016 #endif
1017 };
1018
1019 static struct inet_protosw dccp_v4_protosw = {
1020         .type           = SOCK_DCCP,
1021         .protocol       = IPPROTO_DCCP,
1022         .prot           = &dccp_v4_prot,
1023         .ops            = &inet_dccp_ops,
1024         .capability     = -1,
1025         .no_check       = 0,
1026         .flags          = INET_PROTOSW_ICSK,
1027 };
1028
1029 static int __init dccp_v4_init(void)
1030 {
1031         int err = proto_register(&dccp_v4_prot, 1);
1032
1033         if (err != 0)
1034                 goto out;
1035
1036         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1037         if (err != 0)
1038                 goto out_proto_unregister;
1039
1040         inet_register_protosw(&dccp_v4_protosw);
1041
1042         err = inet_csk_ctl_sock_create(&dccp_v4_ctl_socket, PF_INET,
1043                                        SOCK_DCCP, IPPROTO_DCCP);
1044         if (err)
1045                 goto out_unregister_protosw;
1046 out:
1047         return err;
1048 out_unregister_protosw:
1049         inet_unregister_protosw(&dccp_v4_protosw);
1050         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1051 out_proto_unregister:
1052         proto_unregister(&dccp_v4_prot);
1053         goto out;
1054 }
1055
1056 static void __exit dccp_v4_exit(void)
1057 {
1058         inet_unregister_protosw(&dccp_v4_protosw);
1059         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1060         proto_unregister(&dccp_v4_prot);
1061 }
1062
1063 module_init(dccp_v4_init);
1064 module_exit(dccp_v4_exit);
1065
1066 /*
1067  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1068  * values directly, Also cover the case where the protocol is not specified,
1069  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1070  */
1071 MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-33-type-6");
1072 MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-0-type-6");
1073 MODULE_LICENSE("GPL");
1074 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1075 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");