ed6202652bccd66d4bc1ef03059656c968f3eca7
[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_gar =
117                 dp->dccps_iss = secure_dccp_sequence_number(inet->saddr,
118                                                             inet->daddr,
119                                                             inet->sport,
120                                                             usin->sin_port);
121         dccp_update_gss(sk, dp->dccps_iss);
122
123         inet->id = dp->dccps_iss ^ jiffies;
124
125         err = dccp_connect(sk);
126         rt = NULL;
127         if (err != 0)
128                 goto failure;
129 out:
130         return err;
131 failure:
132         /*
133          * This unhashes the socket and releases the local port, if necessary.
134          */
135         dccp_set_state(sk, DCCP_CLOSED);
136         ip_rt_put(rt);
137         sk->sk_route_caps = 0;
138         inet->dport = 0;
139         goto out;
140 }
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         /* We don't check in the destentry if pmtu discovery is forbidden
163          * on this route. We just assume that no packet_to_big packets
164          * are send back when pmtu discovery is not active.
165          * There is a small race when the user changes this flag in the
166          * route, but I think that's acceptable.
167          */
168         if ((dst = __sk_dst_check(sk, 0)) == NULL)
169                 return;
170
171         dst->ops->update_pmtu(dst, mtu);
172
173         /* Something is about to be wrong... Remember soft error
174          * for the case, if this connection will not able to recover.
175          */
176         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
177                 sk->sk_err_soft = EMSGSIZE;
178
179         mtu = dst_mtu(dst);
180
181         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
182             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
183                 dccp_sync_mss(sk, mtu);
184
185                 /*
186                  * From RFC 4340, sec. 14.1:
187                  *
188                  *      DCCP-Sync packets are the best choice for upward
189                  *      probing, since DCCP-Sync probes do not risk application
190                  *      data loss.
191                  */
192                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
193         } /* else let the usual retransmit timer handle it */
194 }
195
196 /*
197  * This routine is called by the ICMP module when it gets some sort of error
198  * condition. If err < 0 then the socket should be closed and the error
199  * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
200  * After adjustment header points to the first 8 bytes of the tcp header. We
201  * need to find the appropriate port.
202  *
203  * The locking strategy used here is very "optimistic". When someone else
204  * accesses the socket the ICMP is just dropped and for some paths there is no
205  * check at all. A more general error queue to queue errors for later handling
206  * is probably better.
207  */
208 static void dccp_v4_err(struct sk_buff *skb, u32 info)
209 {
210         const struct iphdr *iph = (struct iphdr *)skb->data;
211         const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data +
212                                                         (iph->ihl << 2));
213         struct dccp_sock *dp;
214         struct inet_sock *inet;
215         const int type = skb->h.icmph->type;
216         const int code = skb->h.icmph->code;
217         struct sock *sk;
218         __u64 seq;
219         int err;
220
221         if (skb->len < (iph->ihl << 2) + 8) {
222                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
223                 return;
224         }
225
226         sk = inet_lookup(&dccp_hashinfo, iph->daddr, dh->dccph_dport,
227                          iph->saddr, dh->dccph_sport, inet_iif(skb));
228         if (sk == NULL) {
229                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
230                 return;
231         }
232
233         if (sk->sk_state == DCCP_TIME_WAIT) {
234                 inet_twsk_put(inet_twsk(sk));
235                 return;
236         }
237
238         bh_lock_sock(sk);
239         /* If too many ICMPs get dropped on busy
240          * servers this needs to be solved differently.
241          */
242         if (sock_owned_by_user(sk))
243                 NET_INC_STATS_BH(LINUX_MIB_LOCKDROPPEDICMPS);
244
245         if (sk->sk_state == DCCP_CLOSED)
246                 goto out;
247
248         dp = dccp_sk(sk);
249         seq = dccp_hdr_seq(skb);
250         if (sk->sk_state != DCCP_LISTEN &&
251             !between48(seq, dp->dccps_swl, dp->dccps_swh)) {
252                 NET_INC_STATS(LINUX_MIB_OUTOFWINDOWICMPS);
253                 goto out;
254         }
255
256         switch (type) {
257         case ICMP_SOURCE_QUENCH:
258                 /* Just silently ignore these. */
259                 goto out;
260         case ICMP_PARAMETERPROB:
261                 err = EPROTO;
262                 break;
263         case ICMP_DEST_UNREACH:
264                 if (code > NR_ICMP_UNREACH)
265                         goto out;
266
267                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
268                         if (!sock_owned_by_user(sk))
269                                 dccp_do_pmtu_discovery(sk, iph, info);
270                         goto out;
271                 }
272
273                 err = icmp_err_convert[code].errno;
274                 break;
275         case ICMP_TIME_EXCEEDED:
276                 err = EHOSTUNREACH;
277                 break;
278         default:
279                 goto out;
280         }
281
282         switch (sk->sk_state) {
283                 struct request_sock *req , **prev;
284         case DCCP_LISTEN:
285                 if (sock_owned_by_user(sk))
286                         goto out;
287                 req = inet_csk_search_req(sk, &prev, dh->dccph_dport,
288                                           iph->daddr, iph->saddr);
289                 if (!req)
290                         goto out;
291
292                 /*
293                  * ICMPs are not backlogged, hence we cannot get an established
294                  * socket here.
295                  */
296                 BUG_TRAP(!req->sk);
297
298                 if (seq != dccp_rsk(req)->dreq_iss) {
299                         NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
300                         goto out;
301                 }
302                 /*
303                  * Still in RESPOND, just remove it silently.
304                  * There is no good way to pass the error to the newly
305                  * created socket, and POSIX does not want network
306                  * errors returned from accept().
307                  */
308                 inet_csk_reqsk_queue_drop(sk, req, prev);
309                 goto out;
310
311         case DCCP_REQUESTING:
312         case DCCP_RESPOND:
313                 if (!sock_owned_by_user(sk)) {
314                         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
315                         sk->sk_err = err;
316
317                         sk->sk_error_report(sk);
318
319                         dccp_done(sk);
320                 } else
321                         sk->sk_err_soft = err;
322                 goto out;
323         }
324
325         /* If we've already connected we will keep trying
326          * until we time out, or the user gives up.
327          *
328          * rfc1122 4.2.3.9 allows to consider as hard errors
329          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
330          * but it is obsoleted by pmtu discovery).
331          *
332          * Note, that in modern internet, where routing is unreliable
333          * and in each dark corner broken firewalls sit, sending random
334          * errors ordered by their masters even this two messages finally lose
335          * their original sense (even Linux sends invalid PORT_UNREACHs)
336          *
337          * Now we are in compliance with RFCs.
338          *                                                      --ANK (980905)
339          */
340
341         inet = inet_sk(sk);
342         if (!sock_owned_by_user(sk) && inet->recverr) {
343                 sk->sk_err = err;
344                 sk->sk_error_report(sk);
345         } else /* Only an error on timeout */
346                 sk->sk_err_soft = err;
347 out:
348         bh_unlock_sock(sk);
349         sock_put(sk);
350 }
351
352 /* This routine computes an IPv4 DCCP checksum. */
353 void dccp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb)
354 {
355         const struct inet_sock *inet = inet_sk(sk);
356         struct dccp_hdr *dh = dccp_hdr(skb);
357
358         dh->dccph_checksum = dccp_v4_checksum(skb, inet->saddr, inet->daddr);
359 }
360
361 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
362
363 static inline u64 dccp_v4_init_sequence(const struct sock *sk,
364                                         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 int dccp_v4_checksum(const struct sk_buff *skb, const __be32 saddr,
458                      const __be32 daddr)
459 {
460         const struct dccp_hdr* dh = dccp_hdr(skb);
461         int checksum_len;
462         u32 tmp;
463
464         if (dh->dccph_cscov == 0)
465                 checksum_len = skb->len;
466         else {
467                 checksum_len = (dh->dccph_cscov + dh->dccph_x) * sizeof(u32);
468                 checksum_len = checksum_len < skb->len ? checksum_len :
469                                                          skb->len;
470         }
471
472         tmp = csum_partial((unsigned char *)dh, checksum_len, 0);
473         return csum_tcpudp_magic(saddr, daddr, checksum_len,
474                                  IPPROTO_DCCP, tmp);
475 }
476
477 EXPORT_SYMBOL_GPL(dccp_v4_checksum);
478
479 static int dccp_v4_verify_checksum(struct sk_buff *skb,
480                                    const __be32 saddr, const __be32 daddr)
481 {
482         struct dccp_hdr *dh = dccp_hdr(skb);
483         int checksum_len;
484         u32 tmp;
485
486         if (dh->dccph_cscov == 0)
487                 checksum_len = skb->len;
488         else {
489                 checksum_len = (dh->dccph_cscov + dh->dccph_x) * sizeof(u32);
490                 checksum_len = checksum_len < skb->len ? checksum_len :
491                                                          skb->len;
492         }
493         tmp = csum_partial((unsigned char *)dh, checksum_len, 0);
494         return csum_tcpudp_magic(saddr, daddr, checksum_len,
495                                  IPPROTO_DCCP, tmp) == 0 ? 0 : -1;
496 }
497
498 static struct dst_entry* dccp_v4_route_skb(struct sock *sk,
499                                            struct sk_buff *skb)
500 {
501         struct rtable *rt;
502         struct flowi fl = { .oif = ((struct rtable *)skb->dst)->rt_iif,
503                             .nl_u = { .ip4_u =
504                                       { .daddr = skb->nh.iph->saddr,
505                                         .saddr = skb->nh.iph->daddr,
506                                         .tos = RT_CONN_FLAGS(sk) } },
507                             .proto = sk->sk_protocol,
508                             .uli_u = { .ports =
509                                        { .sport = dccp_hdr(skb)->dccph_dport,
510                                          .dport = dccp_hdr(skb)->dccph_sport }
511                                      }
512                           };
513
514         security_skb_classify_flow(skb, &fl);
515         if (ip_route_output_flow(&rt, &fl, sk, 0)) {
516                 IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
517                 return NULL;
518         }
519
520         return &rt->u.dst;
521 }
522
523 static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
524                                  struct dst_entry *dst)
525 {
526         int err = -1;
527         struct sk_buff *skb;
528
529         /* First, grab a route. */
530         
531         if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
532                 goto out;
533
534         skb = dccp_make_response(sk, dst, req);
535         if (skb != NULL) {
536                 const struct inet_request_sock *ireq = inet_rsk(req);
537                 struct dccp_hdr *dh = dccp_hdr(skb);
538
539                 dh->dccph_checksum = dccp_v4_checksum(skb, ireq->loc_addr,
540                                                       ireq->rmt_addr);
541                 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
542                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
543                                             ireq->rmt_addr,
544                                             ireq->opt);
545                 if (err == NET_XMIT_CN)
546                         err = 0;
547         }
548
549 out:
550         dst_release(dst);
551         return err;
552 }
553
554 static void dccp_v4_ctl_send_reset(struct sk_buff *rxskb)
555 {
556         int err;
557         struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
558         const int dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
559                                        sizeof(struct dccp_hdr_ext) +
560                                        sizeof(struct dccp_hdr_reset);
561         struct sk_buff *skb;
562         struct dst_entry *dst;
563         u64 seqno;
564
565         /* Never send a reset in response to a reset. */
566         if (rxdh->dccph_type == DCCP_PKT_RESET)
567                 return;
568
569         if (((struct rtable *)rxskb->dst)->rt_type != RTN_LOCAL)
570                 return;
571
572         dst = dccp_v4_route_skb(dccp_v4_ctl_socket->sk, rxskb);
573         if (dst == NULL)
574                 return;
575
576         skb = alloc_skb(dccp_v4_ctl_socket->sk->sk_prot->max_header,
577                         GFP_ATOMIC);
578         if (skb == NULL)
579                 goto out;
580
581         /* Reserve space for headers. */
582         skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
583         skb->dst = dst_clone(dst);
584
585         dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
586
587         /* Build DCCP header and checksum it. */
588         dh->dccph_type     = DCCP_PKT_RESET;
589         dh->dccph_sport    = rxdh->dccph_dport;
590         dh->dccph_dport    = rxdh->dccph_sport;
591         dh->dccph_doff     = dccp_hdr_reset_len / 4;
592         dh->dccph_x        = 1;
593         dccp_hdr_reset(skb)->dccph_reset_code =
594                                 DCCP_SKB_CB(rxskb)->dccpd_reset_code;
595
596         /* See "8.3.1. Abnormal Termination" in RFC 4340 */
597         seqno = 0;
598         if (DCCP_SKB_CB(rxskb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
599                 dccp_set_seqno(&seqno, DCCP_SKB_CB(rxskb)->dccpd_ack_seq + 1);
600
601         dccp_hdr_set_seq(dh, seqno);
602         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb),
603                          DCCP_SKB_CB(rxskb)->dccpd_seq);
604
605         dh->dccph_checksum = dccp_v4_checksum(skb, rxskb->nh.iph->saddr,
606                                               rxskb->nh.iph->daddr);
607
608         bh_lock_sock(dccp_v4_ctl_socket->sk);
609         err = ip_build_and_send_pkt(skb, dccp_v4_ctl_socket->sk,
610                                     rxskb->nh.iph->daddr,
611                                     rxskb->nh.iph->saddr, NULL);
612         bh_unlock_sock(dccp_v4_ctl_socket->sk);
613
614         if (err == NET_XMIT_CN || err == 0) {
615                 DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
616                 DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
617         }
618 out:
619          dst_release(dst);
620 }
621
622 static void dccp_v4_reqsk_destructor(struct request_sock *req)
623 {
624         kfree(inet_rsk(req)->opt);
625 }
626
627 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
628         .family         = PF_INET,
629         .obj_size       = sizeof(struct dccp_request_sock),
630         .rtx_syn_ack    = dccp_v4_send_response,
631         .send_ack       = dccp_reqsk_send_ack,
632         .destructor     = dccp_v4_reqsk_destructor,
633         .send_reset     = dccp_v4_ctl_send_reset,
634 };
635
636 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
637 {
638         struct inet_request_sock *ireq;
639         struct dccp_sock dp;
640         struct request_sock *req;
641         struct dccp_request_sock *dreq;
642         const __be32 saddr = skb->nh.iph->saddr;
643         const __be32 daddr = skb->nh.iph->daddr;
644         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
645         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
646         __u8 reset_code = DCCP_RESET_CODE_TOO_BUSY;
647
648         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
649         if (((struct rtable *)skb->dst)->rt_flags &
650             (RTCF_BROADCAST | RTCF_MULTICAST)) {
651                 reset_code = DCCP_RESET_CODE_NO_CONNECTION;
652                 goto drop;
653         }
654
655         if (dccp_bad_service_code(sk, service)) {
656                 reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
657                 goto drop;
658         }
659         /*
660          * TW buckets are converted to open requests without
661          * limitations, they conserve resources and peer is
662          * evidently real one.
663          */
664         if (inet_csk_reqsk_queue_is_full(sk))
665                 goto drop;
666
667         /*
668          * Accept backlog is full. If we have already queued enough
669          * of warm entries in syn queue, drop request. It is better than
670          * clogging syn queue with openreqs with exponentially increasing
671          * timeout.
672          */
673         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
674                 goto drop;
675
676         req = reqsk_alloc(&dccp_request_sock_ops);
677         if (req == NULL)
678                 goto drop;
679
680         if (dccp_parse_options(sk, skb))
681                 goto drop_and_free;
682
683         dccp_openreq_init(req, &dp, skb);
684
685         if (security_inet_conn_request(sk, skb, req))
686                 goto drop_and_free;
687
688         ireq = inet_rsk(req);
689         ireq->loc_addr = daddr;
690         ireq->rmt_addr = saddr;
691         req->rcv_wnd    = dccp_feat_default_sequence_window;
692         ireq->opt       = NULL;
693
694         /* 
695          * Step 3: Process LISTEN state
696          *
697          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
698          *
699          * In fact we defer setting S.GSR, S.SWL, S.SWH to
700          * dccp_create_openreq_child.
701          */
702         dreq = dccp_rsk(req);
703         dreq->dreq_isr     = dcb->dccpd_seq;
704         dreq->dreq_iss     = dccp_v4_init_sequence(sk, skb);
705         dreq->dreq_service = service;
706
707         if (dccp_v4_send_response(sk, req, NULL))
708                 goto drop_and_free;
709
710         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
711         return 0;
712
713 drop_and_free:
714         reqsk_free(req);
715 drop:
716         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
717         dcb->dccpd_reset_code = reset_code;
718         return -1;
719 }
720
721 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
722
723 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
724 {
725         struct dccp_hdr *dh = dccp_hdr(skb);
726
727         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
728                 if (dccp_rcv_established(sk, skb, dh, skb->len))
729                         goto reset;
730                 return 0;
731         }
732
733         /*
734          *  Step 3: Process LISTEN state
735          *     If S.state == LISTEN,
736          *        If P.type == Request or P contains a valid Init Cookie
737          *              option,
738          *           * Must scan the packet's options to check for an Init
739          *              Cookie.  Only the Init Cookie is processed here,
740          *              however; other options are processed in Step 8.  This
741          *              scan need only be performed if the endpoint uses Init
742          *              Cookies *
743          *           * Generate a new socket and switch to that socket *
744          *           Set S := new socket for this port pair
745          *           S.state = RESPOND
746          *           Choose S.ISS (initial seqno) or set from Init Cookie
747          *           Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
748          *           Continue with S.state == RESPOND
749          *           * A Response packet will be generated in Step 11 *
750          *        Otherwise,
751          *           Generate Reset(No Connection) unless P.type == Reset
752          *           Drop packet and return
753          *
754          * NOTE: the check for the packet types is done in
755          *       dccp_rcv_state_process
756          */
757         if (sk->sk_state == DCCP_LISTEN) {
758                 struct sock *nsk = dccp_v4_hnd_req(sk, skb);
759
760                 if (nsk == NULL)
761                         goto discard;
762
763                 if (nsk != sk) {
764                         if (dccp_child_process(sk, nsk, skb))
765                                 goto reset;
766                         return 0;
767                 }
768         }
769
770         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
771                 goto reset;
772         return 0;
773
774 reset:
775         dccp_v4_ctl_send_reset(skb);
776 discard:
777         kfree_skb(skb);
778         return 0;
779 }
780
781 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
782
783 int dccp_invalid_packet(struct sk_buff *skb)
784 {
785         const struct dccp_hdr *dh;
786
787         if (skb->pkt_type != PACKET_HOST)
788                 return 1;
789
790         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
791                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: pskb_may_pull failed\n");
792                 return 1;
793         }
794
795         dh = dccp_hdr(skb);
796
797         /* If the packet type is not understood, drop packet and return */
798         if (dh->dccph_type >= DCCP_PKT_INVALID) {
799                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: invalid packet type\n");
800                 return 1;
801         }
802
803         /*
804          * If P.Data Offset is too small for packet type, or too large for
805          * packet, drop packet and return
806          */
807         if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
808                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: P.Data Offset(%u) "
809                                             "too small 1\n",
810                                dh->dccph_doff);
811                 return 1;
812         }
813
814         if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
815                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: P.Data Offset(%u) "
816                                             "too small 2\n",
817                                dh->dccph_doff);
818                 return 1;
819         }
820
821         dh = dccp_hdr(skb);
822
823         /*
824          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
825          * has short sequence numbers), drop packet and return
826          */
827         if (dh->dccph_x == 0 &&
828             dh->dccph_type != DCCP_PKT_DATA &&
829             dh->dccph_type != DCCP_PKT_ACK &&
830             dh->dccph_type != DCCP_PKT_DATAACK) {
831                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: P.type (%s) not Data, Ack "
832                                             "nor DataAck and P.X == 0\n",
833                                dccp_packet_name(dh->dccph_type));
834                 return 1;
835         }
836
837         return 0;
838 }
839
840 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
841
842 /* this is called when real data arrives */
843 static int dccp_v4_rcv(struct sk_buff *skb)
844 {
845         const struct dccp_hdr *dh;
846         struct sock *sk;
847
848         /* Step 1: Check header basics: */
849
850         if (dccp_invalid_packet(skb))
851                 goto discard_it;
852
853         /* If the header checksum is incorrect, drop packet and return */
854         if (dccp_v4_verify_checksum(skb, skb->nh.iph->saddr,
855                                     skb->nh.iph->daddr) < 0) {
856                 LIMIT_NETDEBUG(KERN_WARNING "%s: incorrect header checksum\n",
857                                __FUNCTION__);
858                 goto discard_it;
859         }
860
861         dh = dccp_hdr(skb);
862
863         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(skb);
864         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
865
866         dccp_pr_debug("%8.8s "
867                       "src=%u.%u.%u.%u@%-5d "
868                       "dst=%u.%u.%u.%u@%-5d seq=%llu",
869                       dccp_packet_name(dh->dccph_type),
870                       NIPQUAD(skb->nh.iph->saddr), ntohs(dh->dccph_sport),
871                       NIPQUAD(skb->nh.iph->daddr), ntohs(dh->dccph_dport),
872                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
873
874         if (dccp_packet_without_ack(skb)) {
875                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
876                 dccp_pr_debug_cat("\n");
877         } else {
878                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
879                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
880                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
881         }
882
883         /* Step 2:
884          *      Look up flow ID in table and get corresponding socket */
885         sk = __inet_lookup(&dccp_hashinfo,
886                            skb->nh.iph->saddr, dh->dccph_sport,
887                            skb->nh.iph->daddr, dh->dccph_dport,
888                            inet_iif(skb));
889
890         /* 
891          * Step 2:
892          *      If no socket ...
893          *              Generate Reset(No Connection) unless P.type == Reset
894          *              Drop packet and return
895          */
896         if (sk == NULL) {
897                 dccp_pr_debug("failed to look up flow ID in table and "
898                               "get corresponding socket\n");
899                 goto no_dccp_socket;
900         }
901
902         /* 
903          * Step 2:
904          *      ... or S.state == TIMEWAIT,
905          *              Generate Reset(No Connection) unless P.type == Reset
906          *              Drop packet and return
907          */
908         if (sk->sk_state == DCCP_TIME_WAIT) {
909                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
910                 inet_twsk_put(inet_twsk(sk));
911                 goto no_dccp_socket;
912         }
913
914         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
915                 goto discard_and_relse;
916         nf_reset(skb);
917
918         return sk_receive_skb(sk, skb);
919
920 no_dccp_socket:
921         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
922                 goto discard_it;
923         /*
924          * Step 2:
925          *              Generate Reset(No Connection) unless P.type == Reset
926          *              Drop packet and return
927          */
928         if (dh->dccph_type != DCCP_PKT_RESET) {
929                 DCCP_SKB_CB(skb)->dccpd_reset_code =
930                                         DCCP_RESET_CODE_NO_CONNECTION;
931                 dccp_v4_ctl_send_reset(skb);
932         }
933
934 discard_it:
935         kfree_skb(skb);
936         return 0;
937
938 discard_and_relse:
939         sock_put(sk);
940         goto discard_it;
941 }
942
943 static struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
944         .queue_xmit        = ip_queue_xmit,
945         .send_check        = dccp_v4_send_check,
946         .rebuild_header    = inet_sk_rebuild_header,
947         .conn_request      = dccp_v4_conn_request,
948         .syn_recv_sock     = dccp_v4_request_recv_sock,
949         .net_header_len    = sizeof(struct iphdr),
950         .setsockopt        = ip_setsockopt,
951         .getsockopt        = ip_getsockopt,
952         .addr2sockaddr     = inet_csk_addr2sockaddr,
953         .sockaddr_len      = sizeof(struct sockaddr_in),
954 #ifdef CONFIG_COMPAT
955         .compat_setsockopt = compat_ip_setsockopt,
956         .compat_getsockopt = compat_ip_getsockopt,
957 #endif
958 };
959
960 static int dccp_v4_init_sock(struct sock *sk)
961 {
962         static __u8 dccp_v4_ctl_sock_initialized;
963         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
964
965         if (err == 0) {
966                 if (unlikely(!dccp_v4_ctl_sock_initialized))
967                         dccp_v4_ctl_sock_initialized = 1;
968                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
969         }
970
971         return err;
972 }
973
974 static struct timewait_sock_ops dccp_timewait_sock_ops = {
975         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
976 };
977
978 static struct proto dccp_v4_prot = {
979         .name                   = "DCCP",
980         .owner                  = THIS_MODULE,
981         .close                  = dccp_close,
982         .connect                = dccp_v4_connect,
983         .disconnect             = dccp_disconnect,
984         .ioctl                  = dccp_ioctl,
985         .init                   = dccp_v4_init_sock,
986         .setsockopt             = dccp_setsockopt,
987         .getsockopt             = dccp_getsockopt,
988         .sendmsg                = dccp_sendmsg,
989         .recvmsg                = dccp_recvmsg,
990         .backlog_rcv            = dccp_v4_do_rcv,
991         .hash                   = dccp_hash,
992         .unhash                 = dccp_unhash,
993         .accept                 = inet_csk_accept,
994         .get_port               = dccp_v4_get_port,
995         .shutdown               = dccp_shutdown,
996         .destroy                = dccp_destroy_sock,
997         .orphan_count           = &dccp_orphan_count,
998         .max_header             = MAX_DCCP_HEADER,
999         .obj_size               = sizeof(struct dccp_sock),
1000         .rsk_prot               = &dccp_request_sock_ops,
1001         .twsk_prot              = &dccp_timewait_sock_ops,
1002 #ifdef CONFIG_COMPAT
1003         .compat_setsockopt      = compat_dccp_setsockopt,
1004         .compat_getsockopt      = compat_dccp_getsockopt,
1005 #endif
1006 };
1007
1008 static struct net_protocol dccp_v4_protocol = {
1009         .handler        = dccp_v4_rcv,
1010         .err_handler    = dccp_v4_err,
1011         .no_policy      = 1,
1012 };
1013
1014 static const struct proto_ops inet_dccp_ops = {
1015         .family            = PF_INET,
1016         .owner             = THIS_MODULE,
1017         .release           = inet_release,
1018         .bind              = inet_bind,
1019         .connect           = inet_stream_connect,
1020         .socketpair        = sock_no_socketpair,
1021         .accept            = inet_accept,
1022         .getname           = inet_getname,
1023         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
1024         .poll              = dccp_poll,
1025         .ioctl             = inet_ioctl,
1026         /* FIXME: work on inet_listen to rename it to sock_common_listen */
1027         .listen            = inet_dccp_listen,
1028         .shutdown          = inet_shutdown,
1029         .setsockopt        = sock_common_setsockopt,
1030         .getsockopt        = sock_common_getsockopt,
1031         .sendmsg           = inet_sendmsg,
1032         .recvmsg           = sock_common_recvmsg,
1033         .mmap              = sock_no_mmap,
1034         .sendpage          = sock_no_sendpage,
1035 #ifdef CONFIG_COMPAT
1036         .compat_setsockopt = compat_sock_common_setsockopt,
1037         .compat_getsockopt = compat_sock_common_getsockopt,
1038 #endif
1039 };
1040
1041 static struct inet_protosw dccp_v4_protosw = {
1042         .type           = SOCK_DCCP,
1043         .protocol       = IPPROTO_DCCP,
1044         .prot           = &dccp_v4_prot,
1045         .ops            = &inet_dccp_ops,
1046         .capability     = -1,
1047         .no_check       = 0,
1048         .flags          = INET_PROTOSW_ICSK,
1049 };
1050
1051 static int __init dccp_v4_init(void)
1052 {
1053         int err = proto_register(&dccp_v4_prot, 1);
1054
1055         if (err != 0)
1056                 goto out;
1057
1058         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1059         if (err != 0)
1060                 goto out_proto_unregister;
1061
1062         inet_register_protosw(&dccp_v4_protosw);
1063
1064         err = inet_csk_ctl_sock_create(&dccp_v4_ctl_socket, PF_INET,
1065                                        SOCK_DCCP, IPPROTO_DCCP);
1066         if (err)
1067                 goto out_unregister_protosw;
1068 out:
1069         return err;
1070 out_unregister_protosw:
1071         inet_unregister_protosw(&dccp_v4_protosw);
1072         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1073 out_proto_unregister:
1074         proto_unregister(&dccp_v4_prot);
1075         goto out;
1076 }
1077
1078 static void __exit dccp_v4_exit(void)
1079 {
1080         inet_unregister_protosw(&dccp_v4_protosw);
1081         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1082         proto_unregister(&dccp_v4_prot);
1083 }
1084
1085 module_init(dccp_v4_init);
1086 module_exit(dccp_v4_exit);
1087
1088 /*
1089  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1090  * values directly, Also cover the case where the protocol is not specified,
1091  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1092  */
1093 MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-33-type-6");
1094 MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-0-type-6");
1095 MODULE_LICENSE("GPL");
1096 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1097 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");