[DCCP]: Simplified conditions due to use of enum:8 states
[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);
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 = skb->h.icmph->type;
211         const int code = skb->h.icmph->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(skb->nh.iph->daddr,
367                                            skb->nh.iph->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 dccp_sock *newdp;
385         struct sock *newsk;
386
387         if (sk_acceptq_is_full(sk))
388                 goto exit_overflow;
389
390         if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
391                 goto exit;
392
393         newsk = dccp_create_openreq_child(sk, req, skb);
394         if (newsk == NULL)
395                 goto exit;
396
397         sk_setup_caps(newsk, dst);
398
399         newdp              = dccp_sk(newsk);
400         newinet            = inet_sk(newsk);
401         ireq               = inet_rsk(req);
402         newinet->daddr     = ireq->rmt_addr;
403         newinet->rcv_saddr = ireq->loc_addr;
404         newinet->saddr     = ireq->loc_addr;
405         newinet->opt       = ireq->opt;
406         ireq->opt          = NULL;
407         newinet->mc_index  = inet_iif(skb);
408         newinet->mc_ttl    = skb->nh.iph->ttl;
409         newinet->id        = jiffies;
410
411         dccp_sync_mss(newsk, dst_mtu(dst));
412
413         __inet_hash(&dccp_hashinfo, newsk, 0);
414         __inet_inherit_port(&dccp_hashinfo, sk, newsk);
415
416         return newsk;
417
418 exit_overflow:
419         NET_INC_STATS_BH(LINUX_MIB_LISTENOVERFLOWS);
420 exit:
421         NET_INC_STATS_BH(LINUX_MIB_LISTENDROPS);
422         dst_release(dst);
423         return NULL;
424 }
425
426 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
427
428 static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
429 {
430         const struct dccp_hdr *dh = dccp_hdr(skb);
431         const struct iphdr *iph = skb->nh.iph;
432         struct sock *nsk;
433         struct request_sock **prev;
434         /* Find possible connection requests. */
435         struct request_sock *req = inet_csk_search_req(sk, &prev,
436                                                        dh->dccph_sport,
437                                                        iph->saddr, iph->daddr);
438         if (req != NULL)
439                 return dccp_check_req(sk, skb, req, prev);
440
441         nsk = inet_lookup_established(&dccp_hashinfo,
442                                       iph->saddr, dh->dccph_sport,
443                                       iph->daddr, dh->dccph_dport,
444                                       inet_iif(skb));
445         if (nsk != NULL) {
446                 if (nsk->sk_state != DCCP_TIME_WAIT) {
447                         bh_lock_sock(nsk);
448                         return nsk;
449                 }
450                 inet_twsk_put(inet_twsk(nsk));
451                 return NULL;
452         }
453
454         return sk;
455 }
456
457 static struct dst_entry* dccp_v4_route_skb(struct sock *sk,
458                                            struct sk_buff *skb)
459 {
460         struct rtable *rt;
461         struct flowi fl = { .oif = ((struct rtable *)skb->dst)->rt_iif,
462                             .nl_u = { .ip4_u =
463                                       { .daddr = skb->nh.iph->saddr,
464                                         .saddr = skb->nh.iph->daddr,
465                                         .tos = RT_CONN_FLAGS(sk) } },
466                             .proto = sk->sk_protocol,
467                             .uli_u = { .ports =
468                                        { .sport = dccp_hdr(skb)->dccph_dport,
469                                          .dport = dccp_hdr(skb)->dccph_sport }
470                                      }
471                           };
472
473         security_skb_classify_flow(skb, &fl);
474         if (ip_route_output_flow(&rt, &fl, sk, 0)) {
475                 IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
476                 return NULL;
477         }
478
479         return &rt->u.dst;
480 }
481
482 static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
483                                  struct dst_entry *dst)
484 {
485         int err = -1;
486         struct sk_buff *skb;
487
488         /* First, grab a route. */
489         
490         if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
491                 goto out;
492
493         skb = dccp_make_response(sk, dst, req);
494         if (skb != NULL) {
495                 const struct inet_request_sock *ireq = inet_rsk(req);
496                 struct dccp_hdr *dh = dccp_hdr(skb);
497
498                 dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->loc_addr,
499                                                               ireq->rmt_addr);
500                 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
501                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
502                                             ireq->rmt_addr,
503                                             ireq->opt);
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(struct sock *sk, struct sk_buff *rxskb)
513 {
514         int err;
515         struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
516         const int dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
517                                        sizeof(struct dccp_hdr_ext) +
518                                        sizeof(struct dccp_hdr_reset);
519         struct sk_buff *skb;
520         struct dst_entry *dst;
521         u64 seqno = 0;
522
523         /* Never send a reset in response to a reset. */
524         if (rxdh->dccph_type == DCCP_PKT_RESET)
525                 return;
526
527         if (((struct rtable *)rxskb->dst)->rt_type != RTN_LOCAL)
528                 return;
529
530         dst = dccp_v4_route_skb(dccp_v4_ctl_socket->sk, rxskb);
531         if (dst == NULL)
532                 return;
533
534         skb = alloc_skb(dccp_v4_ctl_socket->sk->sk_prot->max_header,
535                         GFP_ATOMIC);
536         if (skb == NULL)
537                 goto out;
538
539         /* Reserve space for headers. */
540         skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
541         skb->dst = dst_clone(dst);
542
543         dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
544
545         /* Build DCCP header and checksum it. */
546         dh->dccph_type     = DCCP_PKT_RESET;
547         dh->dccph_sport    = rxdh->dccph_dport;
548         dh->dccph_dport    = rxdh->dccph_sport;
549         dh->dccph_doff     = dccp_hdr_reset_len / 4;
550         dh->dccph_x        = 1;
551         dccp_hdr_reset(skb)->dccph_reset_code =
552                                 DCCP_SKB_CB(rxskb)->dccpd_reset_code;
553
554         /* See "8.3.1. Abnormal Termination" in RFC 4340 */
555         if (DCCP_SKB_CB(rxskb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
556                 dccp_set_seqno(&seqno, DCCP_SKB_CB(rxskb)->dccpd_ack_seq + 1);
557
558         dccp_hdr_set_seq(dh, seqno);
559         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), DCCP_SKB_CB(rxskb)->dccpd_seq);
560
561         dccp_csum_outgoing(skb);
562         dh->dccph_checksum = dccp_v4_csum_finish(skb, rxskb->nh.iph->saddr,
563                                                       rxskb->nh.iph->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                                     rxskb->nh.iph->daddr,
568                                     rxskb->nh.iph->saddr, NULL);
569         bh_unlock_sock(dccp_v4_ctl_socket->sk);
570
571         if (net_xmit_eval(err) == 0) {
572                 DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
573                 DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
574         }
575 out:
576          dst_release(dst);
577 }
578
579 static void dccp_v4_reqsk_destructor(struct request_sock *req)
580 {
581         kfree(inet_rsk(req)->opt);
582 }
583
584 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
585         .family         = PF_INET,
586         .obj_size       = sizeof(struct dccp_request_sock),
587         .rtx_syn_ack    = dccp_v4_send_response,
588         .send_ack       = dccp_reqsk_send_ack,
589         .destructor     = dccp_v4_reqsk_destructor,
590         .send_reset     = dccp_v4_ctl_send_reset,
591 };
592
593 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
594 {
595         struct inet_request_sock *ireq;
596         struct request_sock *req;
597         struct dccp_request_sock *dreq;
598         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
599         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
600         __u8 reset_code = DCCP_RESET_CODE_TOO_BUSY;
601
602         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
603         if (((struct rtable *)skb->dst)->rt_flags &
604             (RTCF_BROADCAST | RTCF_MULTICAST)) {
605                 reset_code = DCCP_RESET_CODE_NO_CONNECTION;
606                 goto drop;
607         }
608
609         if (dccp_bad_service_code(sk, service)) {
610                 reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
611                 goto drop;
612         }
613         /*
614          * TW buckets are converted to open requests without
615          * limitations, they conserve resources and peer is
616          * evidently real one.
617          */
618         if (inet_csk_reqsk_queue_is_full(sk))
619                 goto drop;
620
621         /*
622          * Accept backlog is full. If we have already queued enough
623          * of warm entries in syn queue, drop request. It is better than
624          * clogging syn queue with openreqs with exponentially increasing
625          * timeout.
626          */
627         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
628                 goto drop;
629
630         req = reqsk_alloc(&dccp_request_sock_ops);
631         if (req == NULL)
632                 goto drop;
633
634         if (dccp_parse_options(sk, skb))
635                 goto drop_and_free;
636
637         dccp_reqsk_init(req, skb);
638
639         if (security_inet_conn_request(sk, skb, req))
640                 goto drop_and_free;
641
642         ireq = inet_rsk(req);
643         ireq->loc_addr = skb->nh.iph->daddr;
644         ireq->rmt_addr = skb->nh.iph->saddr;
645         ireq->opt       = NULL;
646
647         /* 
648          * Step 3: Process LISTEN state
649          *
650          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
651          *
652          * In fact we defer setting S.GSR, S.SWL, S.SWH to
653          * dccp_create_openreq_child.
654          */
655         dreq = dccp_rsk(req);
656         dreq->dreq_isr     = dcb->dccpd_seq;
657         dreq->dreq_iss     = dccp_v4_init_sequence(skb);
658         dreq->dreq_service = service;
659
660         if (dccp_v4_send_response(sk, req, NULL))
661                 goto drop_and_free;
662
663         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
664         return 0;
665
666 drop_and_free:
667         reqsk_free(req);
668 drop:
669         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
670         dcb->dccpd_reset_code = reset_code;
671         return -1;
672 }
673
674 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
675
676 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
677 {
678         struct dccp_hdr *dh = dccp_hdr(skb);
679
680         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
681                 if (dccp_rcv_established(sk, skb, dh, skb->len))
682                         goto reset;
683                 return 0;
684         }
685
686         /*
687          *  Step 3: Process LISTEN state
688          *       If P.type == Request or P contains a valid Init Cookie option,
689          *            (* Must scan the packet's options to check for Init
690          *               Cookies.  Only Init Cookies are processed here,
691          *               however; other options are processed in Step 8.  This
692          *               scan need only be performed if the endpoint uses Init
693          *               Cookies *)
694          *            (* Generate a new socket and switch to that socket *)
695          *            Set S := new socket for this port pair
696          *            S.state = RESPOND
697          *            Choose S.ISS (initial seqno) or set from Init Cookies
698          *            Initialize S.GAR := S.ISS
699          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
700          *            Continue with S.state == RESPOND
701          *            (* A Response packet will be generated in Step 11 *)
702          *       Otherwise,
703          *            Generate Reset(No Connection) unless P.type == Reset
704          *            Drop packet and return
705          *
706          * NOTE: the check for the packet types is done in
707          *       dccp_rcv_state_process
708          */
709         if (sk->sk_state == DCCP_LISTEN) {
710                 struct sock *nsk = dccp_v4_hnd_req(sk, skb);
711
712                 if (nsk == NULL)
713                         goto discard;
714
715                 if (nsk != sk) {
716                         if (dccp_child_process(sk, nsk, skb))
717                                 goto reset;
718                         return 0;
719                 }
720         }
721
722         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
723                 goto reset;
724         return 0;
725
726 reset:
727         dccp_v4_ctl_send_reset(sk, skb);
728 discard:
729         kfree_skb(skb);
730         return 0;
731 }
732
733 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
734
735 /**
736  *      dccp_invalid_packet  -  check for malformed packets
737  *      Implements RFC 4340, 8.5:  Step 1: Check header basics
738  *      Packets that fail these checks are ignored and do not receive Resets.
739  */
740 int dccp_invalid_packet(struct sk_buff *skb)
741 {
742         const struct dccp_hdr *dh;
743         unsigned int cscov;
744
745         if (skb->pkt_type != PACKET_HOST)
746                 return 1;
747
748         /* If the packet is shorter than 12 bytes, drop packet and return */
749         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
750                 DCCP_WARN("pskb_may_pull failed\n");
751                 return 1;
752         }
753
754         dh = dccp_hdr(skb);
755
756         /* If P.type is not understood, drop packet and return */
757         if (dh->dccph_type >= DCCP_PKT_INVALID) {
758                 DCCP_WARN("invalid packet type\n");
759                 return 1;
760         }
761
762         /*
763          * If P.Data Offset is too small for packet type, drop packet and return
764          */
765         if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
766                 DCCP_WARN("P.Data Offset(%u) too small\n", dh->dccph_doff);
767                 return 1;
768         }
769         /*
770          * If P.Data Offset is too too large for packet, drop packet and return
771          */
772         if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
773                 DCCP_WARN("P.Data Offset(%u) too large\n", dh->dccph_doff);
774                 return 1;
775         }
776
777         /*
778          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
779          * has short sequence numbers), drop packet and return
780          */
781         if (dh->dccph_type >= DCCP_PKT_DATA    &&
782             dh->dccph_type <= DCCP_PKT_DATAACK && dh->dccph_x == 0)  {
783                 DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
784                           dccp_packet_name(dh->dccph_type));
785                 return 1;
786         }
787
788         /*
789          * If P.CsCov is too large for the packet size, drop packet and return.
790          * This must come _before_ checksumming (not as RFC 4340 suggests).
791          */
792         cscov = dccp_csum_coverage(skb);
793         if (cscov > skb->len) {
794                 DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
795                           dh->dccph_cscov, skb->len);
796                 return 1;
797         }
798
799         /* If header checksum is incorrect, drop packet and return.
800          * (This step is completed in the AF-dependent functions.) */
801         skb->csum = skb_checksum(skb, 0, cscov, 0);
802
803         return 0;
804 }
805
806 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
807
808 /* this is called when real data arrives */
809 static int dccp_v4_rcv(struct sk_buff *skb)
810 {
811         const struct dccp_hdr *dh;
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         /* Step 1: If header checksum is incorrect, drop packet and return */
821         if (dccp_v4_csum_finish(skb, skb->nh.iph->saddr, skb->nh.iph->daddr)) {
822                 DCCP_WARN("dropped packet with invalid checksum\n");
823                 goto discard_it;
824         }
825
826         dh = dccp_hdr(skb);
827
828         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(skb);
829         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
830
831         dccp_pr_debug("%8.8s "
832                       "src=%u.%u.%u.%u@%-5d "
833                       "dst=%u.%u.%u.%u@%-5d seq=%llu",
834                       dccp_packet_name(dh->dccph_type),
835                       NIPQUAD(skb->nh.iph->saddr), ntohs(dh->dccph_sport),
836                       NIPQUAD(skb->nh.iph->daddr), ntohs(dh->dccph_dport),
837                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
838
839         if (dccp_packet_without_ack(skb)) {
840                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
841                 dccp_pr_debug_cat("\n");
842         } else {
843                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
844                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
845                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
846         }
847
848         /* Step 2:
849          *      Look up flow ID in table and get corresponding socket */
850         sk = __inet_lookup(&dccp_hashinfo,
851                            skb->nh.iph->saddr, dh->dccph_sport,
852                            skb->nh.iph->daddr, dh->dccph_dport,
853                            inet_iif(skb));
854
855         /* 
856          * Step 2:
857          *      If no socket ...
858          */
859         if (sk == NULL) {
860                 dccp_pr_debug("failed to look up flow ID in table and "
861                               "get corresponding socket\n");
862                 goto no_dccp_socket;
863         }
864
865         /* 
866          * Step 2:
867          *      ... or S.state == TIMEWAIT,
868          *              Generate Reset(No Connection) unless P.type == Reset
869          *              Drop packet and return
870          */
871         if (sk->sk_state == DCCP_TIME_WAIT) {
872                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
873                 inet_twsk_put(inet_twsk(sk));
874                 goto no_dccp_socket;
875         }
876
877         /*
878          * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
879          *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
880          *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
881          */
882         min_cov = dccp_sk(sk)->dccps_pcrlen;
883         if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
884                 dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
885                               dh->dccph_cscov, min_cov);
886                 /* FIXME: "Such packets SHOULD be reported using Data Dropped
887                  *         options (Section 11.7) with Drop Code 0, Protocol
888                  *         Constraints."                                     */
889                 goto discard_and_relse;
890         }
891
892         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
893                 goto discard_and_relse;
894         nf_reset(skb);
895
896         return sk_receive_skb(sk, skb, 1);
897
898 no_dccp_socket:
899         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
900                 goto discard_it;
901         /*
902          * Step 2:
903          *      If no socket ...
904          *              Generate Reset(No Connection) unless P.type == Reset
905          *              Drop packet and return
906          */
907         if (dh->dccph_type != DCCP_PKT_RESET) {
908                 DCCP_SKB_CB(skb)->dccpd_reset_code =
909                                         DCCP_RESET_CODE_NO_CONNECTION;
910                 dccp_v4_ctl_send_reset(sk, skb);
911         }
912
913 discard_it:
914         kfree_skb(skb);
915         return 0;
916
917 discard_and_relse:
918         sock_put(sk);
919         goto discard_it;
920 }
921
922 static struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
923         .queue_xmit        = ip_queue_xmit,
924         .send_check        = dccp_v4_send_check,
925         .rebuild_header    = inet_sk_rebuild_header,
926         .conn_request      = dccp_v4_conn_request,
927         .syn_recv_sock     = dccp_v4_request_recv_sock,
928         .net_header_len    = sizeof(struct iphdr),
929         .setsockopt        = ip_setsockopt,
930         .getsockopt        = ip_getsockopt,
931         .addr2sockaddr     = inet_csk_addr2sockaddr,
932         .sockaddr_len      = sizeof(struct sockaddr_in),
933 #ifdef CONFIG_COMPAT
934         .compat_setsockopt = compat_ip_setsockopt,
935         .compat_getsockopt = compat_ip_getsockopt,
936 #endif
937 };
938
939 static int dccp_v4_init_sock(struct sock *sk)
940 {
941         static __u8 dccp_v4_ctl_sock_initialized;
942         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
943
944         if (err == 0) {
945                 if (unlikely(!dccp_v4_ctl_sock_initialized))
946                         dccp_v4_ctl_sock_initialized = 1;
947                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
948         }
949
950         return err;
951 }
952
953 static struct timewait_sock_ops dccp_timewait_sock_ops = {
954         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
955 };
956
957 static struct proto dccp_v4_prot = {
958         .name                   = "DCCP",
959         .owner                  = THIS_MODULE,
960         .close                  = dccp_close,
961         .connect                = dccp_v4_connect,
962         .disconnect             = dccp_disconnect,
963         .ioctl                  = dccp_ioctl,
964         .init                   = dccp_v4_init_sock,
965         .setsockopt             = dccp_setsockopt,
966         .getsockopt             = dccp_getsockopt,
967         .sendmsg                = dccp_sendmsg,
968         .recvmsg                = dccp_recvmsg,
969         .backlog_rcv            = dccp_v4_do_rcv,
970         .hash                   = dccp_hash,
971         .unhash                 = dccp_unhash,
972         .accept                 = inet_csk_accept,
973         .get_port               = dccp_v4_get_port,
974         .shutdown               = dccp_shutdown,
975         .destroy                = dccp_destroy_sock,
976         .orphan_count           = &dccp_orphan_count,
977         .max_header             = MAX_DCCP_HEADER,
978         .obj_size               = sizeof(struct dccp_sock),
979         .rsk_prot               = &dccp_request_sock_ops,
980         .twsk_prot              = &dccp_timewait_sock_ops,
981 #ifdef CONFIG_COMPAT
982         .compat_setsockopt      = compat_dccp_setsockopt,
983         .compat_getsockopt      = compat_dccp_getsockopt,
984 #endif
985 };
986
987 static struct net_protocol dccp_v4_protocol = {
988         .handler        = dccp_v4_rcv,
989         .err_handler    = dccp_v4_err,
990         .no_policy      = 1,
991 };
992
993 static const struct proto_ops inet_dccp_ops = {
994         .family            = PF_INET,
995         .owner             = THIS_MODULE,
996         .release           = inet_release,
997         .bind              = inet_bind,
998         .connect           = inet_stream_connect,
999         .socketpair        = sock_no_socketpair,
1000         .accept            = inet_accept,
1001         .getname           = inet_getname,
1002         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
1003         .poll              = dccp_poll,
1004         .ioctl             = inet_ioctl,
1005         /* FIXME: work on inet_listen to rename it to sock_common_listen */
1006         .listen            = inet_dccp_listen,
1007         .shutdown          = inet_shutdown,
1008         .setsockopt        = sock_common_setsockopt,
1009         .getsockopt        = sock_common_getsockopt,
1010         .sendmsg           = inet_sendmsg,
1011         .recvmsg           = sock_common_recvmsg,
1012         .mmap              = sock_no_mmap,
1013         .sendpage          = sock_no_sendpage,
1014 #ifdef CONFIG_COMPAT
1015         .compat_setsockopt = compat_sock_common_setsockopt,
1016         .compat_getsockopt = compat_sock_common_getsockopt,
1017 #endif
1018 };
1019
1020 static struct inet_protosw dccp_v4_protosw = {
1021         .type           = SOCK_DCCP,
1022         .protocol       = IPPROTO_DCCP,
1023         .prot           = &dccp_v4_prot,
1024         .ops            = &inet_dccp_ops,
1025         .capability     = -1,
1026         .no_check       = 0,
1027         .flags          = INET_PROTOSW_ICSK,
1028 };
1029
1030 static int __init dccp_v4_init(void)
1031 {
1032         int err = proto_register(&dccp_v4_prot, 1);
1033
1034         if (err != 0)
1035                 goto out;
1036
1037         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1038         if (err != 0)
1039                 goto out_proto_unregister;
1040
1041         inet_register_protosw(&dccp_v4_protosw);
1042
1043         err = inet_csk_ctl_sock_create(&dccp_v4_ctl_socket, PF_INET,
1044                                        SOCK_DCCP, IPPROTO_DCCP);
1045         if (err)
1046                 goto out_unregister_protosw;
1047 out:
1048         return err;
1049 out_unregister_protosw:
1050         inet_unregister_protosw(&dccp_v4_protosw);
1051         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1052 out_proto_unregister:
1053         proto_unregister(&dccp_v4_prot);
1054         goto out;
1055 }
1056
1057 static void __exit dccp_v4_exit(void)
1058 {
1059         inet_unregister_protosw(&dccp_v4_protosw);
1060         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1061         proto_unregister(&dccp_v4_prot);
1062 }
1063
1064 module_init(dccp_v4_init);
1065 module_exit(dccp_v4_exit);
1066
1067 /*
1068  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1069  * values directly, Also cover the case where the protocol is not specified,
1070  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1071  */
1072 MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-33-type-6");
1073 MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-0-type-6");
1074 MODULE_LICENSE("GPL");
1075 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1076 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");