[NET]: Conversions from kmalloc+memset to k(z|c)alloc.
[linux-3.10.git] / net / ipv4 / tcp_ipv4.c
1 /*
2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
3  *              operating system.  INET is implemented using the  BSD Socket
4  *              interface as the means of communication with the user level.
5  *
6  *              Implementation of the Transmission Control Protocol(TCP).
7  *
8  * Version:     $Id: tcp_ipv4.c,v 1.240 2002/02/01 22:01:04 davem Exp $
9  *
10  *              IPv4 specific functions
11  *
12  *
13  *              code split from:
14  *              linux/ipv4/tcp.c
15  *              linux/ipv4/tcp_input.c
16  *              linux/ipv4/tcp_output.c
17  *
18  *              See tcp.c for author information
19  *
20  *      This program is free software; you can redistribute it and/or
21  *      modify it under the terms of the GNU General Public License
22  *      as published by the Free Software Foundation; either version
23  *      2 of the License, or (at your option) any later version.
24  */
25
26 /*
27  * Changes:
28  *              David S. Miller :       New socket lookup architecture.
29  *                                      This code is dedicated to John Dyson.
30  *              David S. Miller :       Change semantics of established hash,
31  *                                      half is devoted to TIME_WAIT sockets
32  *                                      and the rest go in the other half.
33  *              Andi Kleen :            Add support for syncookies and fixed
34  *                                      some bugs: ip options weren't passed to
35  *                                      the TCP layer, missed a check for an
36  *                                      ACK bit.
37  *              Andi Kleen :            Implemented fast path mtu discovery.
38  *                                      Fixed many serious bugs in the
39  *                                      request_sock handling and moved
40  *                                      most of it into the af independent code.
41  *                                      Added tail drop and some other bugfixes.
42  *                                      Added new listen semantics.
43  *              Mike McLagan    :       Routing by source
44  *      Juan Jose Ciarlante:            ip_dynaddr bits
45  *              Andi Kleen:             various fixes.
46  *      Vitaly E. Lavrov        :       Transparent proxy revived after year
47  *                                      coma.
48  *      Andi Kleen              :       Fix new listen.
49  *      Andi Kleen              :       Fix accept error reporting.
50  *      YOSHIFUJI Hideaki @USAGI and:   Support IPV6_V6ONLY socket option, which
51  *      Alexey Kuznetsov                allow both IPv4 and IPv6 sockets to bind
52  *                                      a single port at the same time.
53  */
54
55
56 #include <linux/types.h>
57 #include <linux/fcntl.h>
58 #include <linux/module.h>
59 #include <linux/random.h>
60 #include <linux/cache.h>
61 #include <linux/jhash.h>
62 #include <linux/init.h>
63 #include <linux/times.h>
64
65 #include <net/icmp.h>
66 #include <net/inet_hashtables.h>
67 #include <net/tcp.h>
68 #include <net/transp_v6.h>
69 #include <net/ipv6.h>
70 #include <net/inet_common.h>
71 #include <net/timewait_sock.h>
72 #include <net/xfrm.h>
73 #include <net/netdma.h>
74
75 #include <linux/inet.h>
76 #include <linux/ipv6.h>
77 #include <linux/stddef.h>
78 #include <linux/proc_fs.h>
79 #include <linux/seq_file.h>
80
81 int sysctl_tcp_tw_reuse;
82 int sysctl_tcp_low_latency;
83
84 /* Check TCP sequence numbers in ICMP packets. */
85 #define ICMP_MIN_LENGTH 8
86
87 /* Socket used for sending RSTs */
88 static struct socket *tcp_socket;
89
90 void tcp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb);
91
92 struct inet_hashinfo __cacheline_aligned tcp_hashinfo = {
93         .lhash_lock     = __RW_LOCK_UNLOCKED(tcp_hashinfo.lhash_lock),
94         .lhash_users    = ATOMIC_INIT(0),
95         .lhash_wait     = __WAIT_QUEUE_HEAD_INITIALIZER(tcp_hashinfo.lhash_wait),
96 };
97
98 static int tcp_v4_get_port(struct sock *sk, unsigned short snum)
99 {
100         return inet_csk_get_port(&tcp_hashinfo, sk, snum,
101                                  inet_csk_bind_conflict);
102 }
103
104 static void tcp_v4_hash(struct sock *sk)
105 {
106         inet_hash(&tcp_hashinfo, sk);
107 }
108
109 void tcp_unhash(struct sock *sk)
110 {
111         inet_unhash(&tcp_hashinfo, sk);
112 }
113
114 static inline __u32 tcp_v4_init_sequence(struct sock *sk, struct sk_buff *skb)
115 {
116         return secure_tcp_sequence_number(skb->nh.iph->daddr,
117                                           skb->nh.iph->saddr,
118                                           skb->h.th->dest,
119                                           skb->h.th->source);
120 }
121
122 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
123 {
124         const struct tcp_timewait_sock *tcptw = tcp_twsk(sktw);
125         struct tcp_sock *tp = tcp_sk(sk);
126
127         /* With PAWS, it is safe from the viewpoint
128            of data integrity. Even without PAWS it is safe provided sequence
129            spaces do not overlap i.e. at data rates <= 80Mbit/sec.
130
131            Actually, the idea is close to VJ's one, only timestamp cache is
132            held not per host, but per port pair and TW bucket is used as state
133            holder.
134
135            If TW bucket has been already destroyed we fall back to VJ's scheme
136            and use initial timestamp retrieved from peer table.
137          */
138         if (tcptw->tw_ts_recent_stamp &&
139             (twp == NULL || (sysctl_tcp_tw_reuse &&
140                              xtime.tv_sec - tcptw->tw_ts_recent_stamp > 1))) {
141                 tp->write_seq = tcptw->tw_snd_nxt + 65535 + 2;
142                 if (tp->write_seq == 0)
143                         tp->write_seq = 1;
144                 tp->rx_opt.ts_recent       = tcptw->tw_ts_recent;
145                 tp->rx_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
146                 sock_hold(sktw);
147                 return 1;
148         }
149
150         return 0;
151 }
152
153 EXPORT_SYMBOL_GPL(tcp_twsk_unique);
154
155 /* This will initiate an outgoing connection. */
156 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
157 {
158         struct inet_sock *inet = inet_sk(sk);
159         struct tcp_sock *tp = tcp_sk(sk);
160         struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
161         struct rtable *rt;
162         u32 daddr, nexthop;
163         int tmp;
164         int err;
165
166         if (addr_len < sizeof(struct sockaddr_in))
167                 return -EINVAL;
168
169         if (usin->sin_family != AF_INET)
170                 return -EAFNOSUPPORT;
171
172         nexthop = daddr = usin->sin_addr.s_addr;
173         if (inet->opt && inet->opt->srr) {
174                 if (!daddr)
175                         return -EINVAL;
176                 nexthop = inet->opt->faddr;
177         }
178
179         tmp = ip_route_connect(&rt, nexthop, inet->saddr,
180                                RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
181                                IPPROTO_TCP,
182                                inet->sport, usin->sin_port, sk);
183         if (tmp < 0)
184                 return tmp;
185
186         if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
187                 ip_rt_put(rt);
188                 return -ENETUNREACH;
189         }
190
191         if (!inet->opt || !inet->opt->srr)
192                 daddr = rt->rt_dst;
193
194         if (!inet->saddr)
195                 inet->saddr = rt->rt_src;
196         inet->rcv_saddr = inet->saddr;
197
198         if (tp->rx_opt.ts_recent_stamp && inet->daddr != daddr) {
199                 /* Reset inherited state */
200                 tp->rx_opt.ts_recent       = 0;
201                 tp->rx_opt.ts_recent_stamp = 0;
202                 tp->write_seq              = 0;
203         }
204
205         if (tcp_death_row.sysctl_tw_recycle &&
206             !tp->rx_opt.ts_recent_stamp && rt->rt_dst == daddr) {
207                 struct inet_peer *peer = rt_get_peer(rt);
208
209                 /* VJ's idea. We save last timestamp seen from
210                  * the destination in peer table, when entering state TIME-WAIT
211                  * and initialize rx_opt.ts_recent from it, when trying new connection.
212                  */
213
214                 if (peer && peer->tcp_ts_stamp + TCP_PAWS_MSL >= xtime.tv_sec) {
215                         tp->rx_opt.ts_recent_stamp = peer->tcp_ts_stamp;
216                         tp->rx_opt.ts_recent = peer->tcp_ts;
217                 }
218         }
219
220         inet->dport = usin->sin_port;
221         inet->daddr = daddr;
222
223         inet_csk(sk)->icsk_ext_hdr_len = 0;
224         if (inet->opt)
225                 inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;
226
227         tp->rx_opt.mss_clamp = 536;
228
229         /* Socket identity is still unknown (sport may be zero).
230          * However we set state to SYN-SENT and not releasing socket
231          * lock select source port, enter ourselves into the hash tables and
232          * complete initialization after this.
233          */
234         tcp_set_state(sk, TCP_SYN_SENT);
235         err = inet_hash_connect(&tcp_death_row, sk);
236         if (err)
237                 goto failure;
238
239         err = ip_route_newports(&rt, IPPROTO_TCP, inet->sport, inet->dport, sk);
240         if (err)
241                 goto failure;
242
243         /* OK, now commit destination to socket.  */
244         sk->sk_gso_type = SKB_GSO_TCPV4;
245         sk_setup_caps(sk, &rt->u.dst);
246
247         if (!tp->write_seq)
248                 tp->write_seq = secure_tcp_sequence_number(inet->saddr,
249                                                            inet->daddr,
250                                                            inet->sport,
251                                                            usin->sin_port);
252
253         inet->id = tp->write_seq ^ jiffies;
254
255         err = tcp_connect(sk);
256         rt = NULL;
257         if (err)
258                 goto failure;
259
260         return 0;
261
262 failure:
263         /* This unhashes the socket and releases the local port, if necessary. */
264         tcp_set_state(sk, TCP_CLOSE);
265         ip_rt_put(rt);
266         sk->sk_route_caps = 0;
267         inet->dport = 0;
268         return err;
269 }
270
271 /*
272  * This routine does path mtu discovery as defined in RFC1191.
273  */
274 static void do_pmtu_discovery(struct sock *sk, struct iphdr *iph, u32 mtu)
275 {
276         struct dst_entry *dst;
277         struct inet_sock *inet = inet_sk(sk);
278
279         /* We are not interested in TCP_LISTEN and open_requests (SYN-ACKs
280          * send out by Linux are always <576bytes so they should go through
281          * unfragmented).
282          */
283         if (sk->sk_state == TCP_LISTEN)
284                 return;
285
286         /* We don't check in the destentry if pmtu discovery is forbidden
287          * on this route. We just assume that no packet_to_big packets
288          * are send back when pmtu discovery is not active.
289          * There is a small race when the user changes this flag in the
290          * route, but I think that's acceptable.
291          */
292         if ((dst = __sk_dst_check(sk, 0)) == NULL)
293                 return;
294
295         dst->ops->update_pmtu(dst, mtu);
296
297         /* Something is about to be wrong... Remember soft error
298          * for the case, if this connection will not able to recover.
299          */
300         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
301                 sk->sk_err_soft = EMSGSIZE;
302
303         mtu = dst_mtu(dst);
304
305         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
306             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
307                 tcp_sync_mss(sk, mtu);
308
309                 /* Resend the TCP packet because it's
310                  * clear that the old packet has been
311                  * dropped. This is the new "fast" path mtu
312                  * discovery.
313                  */
314                 tcp_simple_retransmit(sk);
315         } /* else let the usual retransmit timer handle it */
316 }
317
318 /*
319  * This routine is called by the ICMP module when it gets some
320  * sort of error condition.  If err < 0 then the socket should
321  * be closed and the error returned to the user.  If err > 0
322  * it's just the icmp type << 8 | icmp code.  After adjustment
323  * header points to the first 8 bytes of the tcp header.  We need
324  * to find the appropriate port.
325  *
326  * The locking strategy used here is very "optimistic". When
327  * someone else accesses the socket the ICMP is just dropped
328  * and for some paths there is no check at all.
329  * A more general error queue to queue errors for later handling
330  * is probably better.
331  *
332  */
333
334 void tcp_v4_err(struct sk_buff *skb, u32 info)
335 {
336         struct iphdr *iph = (struct iphdr *)skb->data;
337         struct tcphdr *th = (struct tcphdr *)(skb->data + (iph->ihl << 2));
338         struct tcp_sock *tp;
339         struct inet_sock *inet;
340         int type = skb->h.icmph->type;
341         int code = skb->h.icmph->code;
342         struct sock *sk;
343         __u32 seq;
344         int err;
345
346         if (skb->len < (iph->ihl << 2) + 8) {
347                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
348                 return;
349         }
350
351         sk = inet_lookup(&tcp_hashinfo, iph->daddr, th->dest, iph->saddr,
352                          th->source, inet_iif(skb));
353         if (!sk) {
354                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
355                 return;
356         }
357         if (sk->sk_state == TCP_TIME_WAIT) {
358                 inet_twsk_put((struct inet_timewait_sock *)sk);
359                 return;
360         }
361
362         bh_lock_sock(sk);
363         /* If too many ICMPs get dropped on busy
364          * servers this needs to be solved differently.
365          */
366         if (sock_owned_by_user(sk))
367                 NET_INC_STATS_BH(LINUX_MIB_LOCKDROPPEDICMPS);
368
369         if (sk->sk_state == TCP_CLOSE)
370                 goto out;
371
372         tp = tcp_sk(sk);
373         seq = ntohl(th->seq);
374         if (sk->sk_state != TCP_LISTEN &&
375             !between(seq, tp->snd_una, tp->snd_nxt)) {
376                 NET_INC_STATS(LINUX_MIB_OUTOFWINDOWICMPS);
377                 goto out;
378         }
379
380         switch (type) {
381         case ICMP_SOURCE_QUENCH:
382                 /* Just silently ignore these. */
383                 goto out;
384         case ICMP_PARAMETERPROB:
385                 err = EPROTO;
386                 break;
387         case ICMP_DEST_UNREACH:
388                 if (code > NR_ICMP_UNREACH)
389                         goto out;
390
391                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
392                         if (!sock_owned_by_user(sk))
393                                 do_pmtu_discovery(sk, iph, info);
394                         goto out;
395                 }
396
397                 err = icmp_err_convert[code].errno;
398                 break;
399         case ICMP_TIME_EXCEEDED:
400                 err = EHOSTUNREACH;
401                 break;
402         default:
403                 goto out;
404         }
405
406         switch (sk->sk_state) {
407                 struct request_sock *req, **prev;
408         case TCP_LISTEN:
409                 if (sock_owned_by_user(sk))
410                         goto out;
411
412                 req = inet_csk_search_req(sk, &prev, th->dest,
413                                           iph->daddr, iph->saddr);
414                 if (!req)
415                         goto out;
416
417                 /* ICMPs are not backlogged, hence we cannot get
418                    an established socket here.
419                  */
420                 BUG_TRAP(!req->sk);
421
422                 if (seq != tcp_rsk(req)->snt_isn) {
423                         NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
424                         goto out;
425                 }
426
427                 /*
428                  * Still in SYN_RECV, just remove it silently.
429                  * There is no good way to pass the error to the newly
430                  * created socket, and POSIX does not want network
431                  * errors returned from accept().
432                  */
433                 inet_csk_reqsk_queue_drop(sk, req, prev);
434                 goto out;
435
436         case TCP_SYN_SENT:
437         case TCP_SYN_RECV:  /* Cannot happen.
438                                It can f.e. if SYNs crossed.
439                              */
440                 if (!sock_owned_by_user(sk)) {
441                         TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
442                         sk->sk_err = err;
443
444                         sk->sk_error_report(sk);
445
446                         tcp_done(sk);
447                 } else {
448                         sk->sk_err_soft = err;
449                 }
450                 goto out;
451         }
452
453         /* If we've already connected we will keep trying
454          * until we time out, or the user gives up.
455          *
456          * rfc1122 4.2.3.9 allows to consider as hard errors
457          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
458          * but it is obsoleted by pmtu discovery).
459          *
460          * Note, that in modern internet, where routing is unreliable
461          * and in each dark corner broken firewalls sit, sending random
462          * errors ordered by their masters even this two messages finally lose
463          * their original sense (even Linux sends invalid PORT_UNREACHs)
464          *
465          * Now we are in compliance with RFCs.
466          *                                                      --ANK (980905)
467          */
468
469         inet = inet_sk(sk);
470         if (!sock_owned_by_user(sk) && inet->recverr) {
471                 sk->sk_err = err;
472                 sk->sk_error_report(sk);
473         } else  { /* Only an error on timeout */
474                 sk->sk_err_soft = err;
475         }
476
477 out:
478         bh_unlock_sock(sk);
479         sock_put(sk);
480 }
481
482 /* This routine computes an IPv4 TCP checksum. */
483 void tcp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb)
484 {
485         struct inet_sock *inet = inet_sk(sk);
486         struct tcphdr *th = skb->h.th;
487
488         if (skb->ip_summed == CHECKSUM_HW) {
489                 th->check = ~tcp_v4_check(th, len, inet->saddr, inet->daddr, 0);
490                 skb->csum = offsetof(struct tcphdr, check);
491         } else {
492                 th->check = tcp_v4_check(th, len, inet->saddr, inet->daddr,
493                                          csum_partial((char *)th,
494                                                       th->doff << 2,
495                                                       skb->csum));
496         }
497 }
498
499 int tcp_v4_gso_send_check(struct sk_buff *skb)
500 {
501         struct iphdr *iph;
502         struct tcphdr *th;
503
504         if (!pskb_may_pull(skb, sizeof(*th)))
505                 return -EINVAL;
506
507         iph = skb->nh.iph;
508         th = skb->h.th;
509
510         th->check = 0;
511         th->check = ~tcp_v4_check(th, skb->len, iph->saddr, iph->daddr, 0);
512         skb->csum = offsetof(struct tcphdr, check);
513         skb->ip_summed = CHECKSUM_HW;
514         return 0;
515 }
516
517 /*
518  *      This routine will send an RST to the other tcp.
519  *
520  *      Someone asks: why I NEVER use socket parameters (TOS, TTL etc.)
521  *                    for reset.
522  *      Answer: if a packet caused RST, it is not for a socket
523  *              existing in our system, if it is matched to a socket,
524  *              it is just duplicate segment or bug in other side's TCP.
525  *              So that we build reply only basing on parameters
526  *              arrived with segment.
527  *      Exception: precedence violation. We do not implement it in any case.
528  */
529
530 static void tcp_v4_send_reset(struct sk_buff *skb)
531 {
532         struct tcphdr *th = skb->h.th;
533         struct tcphdr rth;
534         struct ip_reply_arg arg;
535
536         /* Never send a reset in response to a reset. */
537         if (th->rst)
538                 return;
539
540         if (((struct rtable *)skb->dst)->rt_type != RTN_LOCAL)
541                 return;
542
543         /* Swap the send and the receive. */
544         memset(&rth, 0, sizeof(struct tcphdr));
545         rth.dest   = th->source;
546         rth.source = th->dest;
547         rth.doff   = sizeof(struct tcphdr) / 4;
548         rth.rst    = 1;
549
550         if (th->ack) {
551                 rth.seq = th->ack_seq;
552         } else {
553                 rth.ack = 1;
554                 rth.ack_seq = htonl(ntohl(th->seq) + th->syn + th->fin +
555                                     skb->len - (th->doff << 2));
556         }
557
558         memset(&arg, 0, sizeof arg);
559         arg.iov[0].iov_base = (unsigned char *)&rth;
560         arg.iov[0].iov_len  = sizeof rth;
561         arg.csum = csum_tcpudp_nofold(skb->nh.iph->daddr,
562                                       skb->nh.iph->saddr, /*XXX*/
563                                       sizeof(struct tcphdr), IPPROTO_TCP, 0);
564         arg.csumoffset = offsetof(struct tcphdr, check) / 2;
565
566         ip_send_reply(tcp_socket->sk, skb, &arg, sizeof rth);
567
568         TCP_INC_STATS_BH(TCP_MIB_OUTSEGS);
569         TCP_INC_STATS_BH(TCP_MIB_OUTRSTS);
570 }
571
572 /* The code following below sending ACKs in SYN-RECV and TIME-WAIT states
573    outside socket context is ugly, certainly. What can I do?
574  */
575
576 static void tcp_v4_send_ack(struct sk_buff *skb, u32 seq, u32 ack,
577                             u32 win, u32 ts)
578 {
579         struct tcphdr *th = skb->h.th;
580         struct {
581                 struct tcphdr th;
582                 u32 tsopt[3];
583         } rep;
584         struct ip_reply_arg arg;
585
586         memset(&rep.th, 0, sizeof(struct tcphdr));
587         memset(&arg, 0, sizeof arg);
588
589         arg.iov[0].iov_base = (unsigned char *)&rep;
590         arg.iov[0].iov_len  = sizeof(rep.th);
591         if (ts) {
592                 rep.tsopt[0] = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
593                                      (TCPOPT_TIMESTAMP << 8) |
594                                      TCPOLEN_TIMESTAMP);
595                 rep.tsopt[1] = htonl(tcp_time_stamp);
596                 rep.tsopt[2] = htonl(ts);
597                 arg.iov[0].iov_len = sizeof(rep);
598         }
599
600         /* Swap the send and the receive. */
601         rep.th.dest    = th->source;
602         rep.th.source  = th->dest;
603         rep.th.doff    = arg.iov[0].iov_len / 4;
604         rep.th.seq     = htonl(seq);
605         rep.th.ack_seq = htonl(ack);
606         rep.th.ack     = 1;
607         rep.th.window  = htons(win);
608
609         arg.csum = csum_tcpudp_nofold(skb->nh.iph->daddr,
610                                       skb->nh.iph->saddr, /*XXX*/
611                                       arg.iov[0].iov_len, IPPROTO_TCP, 0);
612         arg.csumoffset = offsetof(struct tcphdr, check) / 2;
613
614         ip_send_reply(tcp_socket->sk, skb, &arg, arg.iov[0].iov_len);
615
616         TCP_INC_STATS_BH(TCP_MIB_OUTSEGS);
617 }
618
619 static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb)
620 {
621         struct inet_timewait_sock *tw = inet_twsk(sk);
622         const struct tcp_timewait_sock *tcptw = tcp_twsk(sk);
623
624         tcp_v4_send_ack(skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
625                         tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale, tcptw->tw_ts_recent);
626
627         inet_twsk_put(tw);
628 }
629
630 static void tcp_v4_reqsk_send_ack(struct sk_buff *skb, struct request_sock *req)
631 {
632         tcp_v4_send_ack(skb, tcp_rsk(req)->snt_isn + 1, tcp_rsk(req)->rcv_isn + 1, req->rcv_wnd,
633                         req->ts_recent);
634 }
635
636 /*
637  *      Send a SYN-ACK after having received an ACK.
638  *      This still operates on a request_sock only, not on a big
639  *      socket.
640  */
641 static int tcp_v4_send_synack(struct sock *sk, struct request_sock *req,
642                               struct dst_entry *dst)
643 {
644         const struct inet_request_sock *ireq = inet_rsk(req);
645         int err = -1;
646         struct sk_buff * skb;
647
648         /* First, grab a route. */
649         if (!dst && (dst = inet_csk_route_req(sk, req)) == NULL)
650                 goto out;
651
652         skb = tcp_make_synack(sk, dst, req);
653
654         if (skb) {
655                 struct tcphdr *th = skb->h.th;
656
657                 th->check = tcp_v4_check(th, skb->len,
658                                          ireq->loc_addr,
659                                          ireq->rmt_addr,
660                                          csum_partial((char *)th, skb->len,
661                                                       skb->csum));
662
663                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
664                                             ireq->rmt_addr,
665                                             ireq->opt);
666                 if (err == NET_XMIT_CN)
667                         err = 0;
668         }
669
670 out:
671         dst_release(dst);
672         return err;
673 }
674
675 /*
676  *      IPv4 request_sock destructor.
677  */
678 static void tcp_v4_reqsk_destructor(struct request_sock *req)
679 {
680         kfree(inet_rsk(req)->opt);
681 }
682
683 #ifdef CONFIG_SYN_COOKIES
684 static void syn_flood_warning(struct sk_buff *skb)
685 {
686         static unsigned long warntime;
687
688         if (time_after(jiffies, (warntime + HZ * 60))) {
689                 warntime = jiffies;
690                 printk(KERN_INFO
691                        "possible SYN flooding on port %d. Sending cookies.\n",
692                        ntohs(skb->h.th->dest));
693         }
694 }
695 #endif
696
697 /*
698  * Save and compile IPv4 options into the request_sock if needed.
699  */
700 static struct ip_options *tcp_v4_save_options(struct sock *sk,
701                                               struct sk_buff *skb)
702 {
703         struct ip_options *opt = &(IPCB(skb)->opt);
704         struct ip_options *dopt = NULL;
705
706         if (opt && opt->optlen) {
707                 int opt_size = optlength(opt);
708                 dopt = kmalloc(opt_size, GFP_ATOMIC);
709                 if (dopt) {
710                         if (ip_options_echo(dopt, skb)) {
711                                 kfree(dopt);
712                                 dopt = NULL;
713                         }
714                 }
715         }
716         return dopt;
717 }
718
719 struct request_sock_ops tcp_request_sock_ops = {
720         .family         =       PF_INET,
721         .obj_size       =       sizeof(struct tcp_request_sock),
722         .rtx_syn_ack    =       tcp_v4_send_synack,
723         .send_ack       =       tcp_v4_reqsk_send_ack,
724         .destructor     =       tcp_v4_reqsk_destructor,
725         .send_reset     =       tcp_v4_send_reset,
726 };
727
728 static struct timewait_sock_ops tcp_timewait_sock_ops = {
729         .twsk_obj_size  = sizeof(struct tcp_timewait_sock),
730         .twsk_unique    = tcp_twsk_unique,
731 };
732
733 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
734 {
735         struct inet_request_sock *ireq;
736         struct tcp_options_received tmp_opt;
737         struct request_sock *req;
738         __u32 saddr = skb->nh.iph->saddr;
739         __u32 daddr = skb->nh.iph->daddr;
740         __u32 isn = TCP_SKB_CB(skb)->when;
741         struct dst_entry *dst = NULL;
742 #ifdef CONFIG_SYN_COOKIES
743         int want_cookie = 0;
744 #else
745 #define want_cookie 0 /* Argh, why doesn't gcc optimize this :( */
746 #endif
747
748         /* Never answer to SYNs send to broadcast or multicast */
749         if (((struct rtable *)skb->dst)->rt_flags &
750             (RTCF_BROADCAST | RTCF_MULTICAST))
751                 goto drop;
752
753         /* TW buckets are converted to open requests without
754          * limitations, they conserve resources and peer is
755          * evidently real one.
756          */
757         if (inet_csk_reqsk_queue_is_full(sk) && !isn) {
758 #ifdef CONFIG_SYN_COOKIES
759                 if (sysctl_tcp_syncookies) {
760                         want_cookie = 1;
761                 } else
762 #endif
763                 goto drop;
764         }
765
766         /* Accept backlog is full. If we have already queued enough
767          * of warm entries in syn queue, drop request. It is better than
768          * clogging syn queue with openreqs with exponentially increasing
769          * timeout.
770          */
771         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
772                 goto drop;
773
774         req = reqsk_alloc(&tcp_request_sock_ops);
775         if (!req)
776                 goto drop;
777
778         tcp_clear_options(&tmp_opt);
779         tmp_opt.mss_clamp = 536;
780         tmp_opt.user_mss  = tcp_sk(sk)->rx_opt.user_mss;
781
782         tcp_parse_options(skb, &tmp_opt, 0);
783
784         if (want_cookie) {
785                 tcp_clear_options(&tmp_opt);
786                 tmp_opt.saw_tstamp = 0;
787         }
788
789         if (tmp_opt.saw_tstamp && !tmp_opt.rcv_tsval) {
790                 /* Some OSes (unknown ones, but I see them on web server, which
791                  * contains information interesting only for windows'
792                  * users) do not send their stamp in SYN. It is easy case.
793                  * We simply do not advertise TS support.
794                  */
795                 tmp_opt.saw_tstamp = 0;
796                 tmp_opt.tstamp_ok  = 0;
797         }
798         tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
799
800         tcp_openreq_init(req, &tmp_opt, skb);
801
802         ireq = inet_rsk(req);
803         ireq->loc_addr = daddr;
804         ireq->rmt_addr = saddr;
805         ireq->opt = tcp_v4_save_options(sk, skb);
806         if (!want_cookie)
807                 TCP_ECN_create_request(req, skb->h.th);
808
809         if (want_cookie) {
810 #ifdef CONFIG_SYN_COOKIES
811                 syn_flood_warning(skb);
812 #endif
813                 isn = cookie_v4_init_sequence(sk, skb, &req->mss);
814         } else if (!isn) {
815                 struct inet_peer *peer = NULL;
816
817                 /* VJ's idea. We save last timestamp seen
818                  * from the destination in peer table, when entering
819                  * state TIME-WAIT, and check against it before
820                  * accepting new connection request.
821                  *
822                  * If "isn" is not zero, this request hit alive
823                  * timewait bucket, so that all the necessary checks
824                  * are made in the function processing timewait state.
825                  */
826                 if (tmp_opt.saw_tstamp &&
827                     tcp_death_row.sysctl_tw_recycle &&
828                     (dst = inet_csk_route_req(sk, req)) != NULL &&
829                     (peer = rt_get_peer((struct rtable *)dst)) != NULL &&
830                     peer->v4daddr == saddr) {
831                         if (xtime.tv_sec < peer->tcp_ts_stamp + TCP_PAWS_MSL &&
832                             (s32)(peer->tcp_ts - req->ts_recent) >
833                                                         TCP_PAWS_WINDOW) {
834                                 NET_INC_STATS_BH(LINUX_MIB_PAWSPASSIVEREJECTED);
835                                 dst_release(dst);
836                                 goto drop_and_free;
837                         }
838                 }
839                 /* Kill the following clause, if you dislike this way. */
840                 else if (!sysctl_tcp_syncookies &&
841                          (sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
842                           (sysctl_max_syn_backlog >> 2)) &&
843                          (!peer || !peer->tcp_ts_stamp) &&
844                          (!dst || !dst_metric(dst, RTAX_RTT))) {
845                         /* Without syncookies last quarter of
846                          * backlog is filled with destinations,
847                          * proven to be alive.
848                          * It means that we continue to communicate
849                          * to destinations, already remembered
850                          * to the moment of synflood.
851                          */
852                         LIMIT_NETDEBUG(KERN_DEBUG "TCP: drop open "
853                                        "request from %u.%u.%u.%u/%u\n",
854                                        NIPQUAD(saddr),
855                                        ntohs(skb->h.th->source));
856                         dst_release(dst);
857                         goto drop_and_free;
858                 }
859
860                 isn = tcp_v4_init_sequence(sk, skb);
861         }
862         tcp_rsk(req)->snt_isn = isn;
863
864         if (tcp_v4_send_synack(sk, req, dst))
865                 goto drop_and_free;
866
867         if (want_cookie) {
868                 reqsk_free(req);
869         } else {
870                 inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
871         }
872         return 0;
873
874 drop_and_free:
875         reqsk_free(req);
876 drop:
877         TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
878         return 0;
879 }
880
881
882 /*
883  * The three way handshake has completed - we got a valid synack -
884  * now create the new socket.
885  */
886 struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
887                                   struct request_sock *req,
888                                   struct dst_entry *dst)
889 {
890         struct inet_request_sock *ireq;
891         struct inet_sock *newinet;
892         struct tcp_sock *newtp;
893         struct sock *newsk;
894
895         if (sk_acceptq_is_full(sk))
896                 goto exit_overflow;
897
898         if (!dst && (dst = inet_csk_route_req(sk, req)) == NULL)
899                 goto exit;
900
901         newsk = tcp_create_openreq_child(sk, req, skb);
902         if (!newsk)
903                 goto exit;
904
905         newsk->sk_gso_type = SKB_GSO_TCPV4;
906         sk_setup_caps(newsk, dst);
907
908         newtp                 = tcp_sk(newsk);
909         newinet               = inet_sk(newsk);
910         ireq                  = inet_rsk(req);
911         newinet->daddr        = ireq->rmt_addr;
912         newinet->rcv_saddr    = ireq->loc_addr;
913         newinet->saddr        = ireq->loc_addr;
914         newinet->opt          = ireq->opt;
915         ireq->opt             = NULL;
916         newinet->mc_index     = inet_iif(skb);
917         newinet->mc_ttl       = skb->nh.iph->ttl;
918         inet_csk(newsk)->icsk_ext_hdr_len = 0;
919         if (newinet->opt)
920                 inet_csk(newsk)->icsk_ext_hdr_len = newinet->opt->optlen;
921         newinet->id = newtp->write_seq ^ jiffies;
922
923         tcp_mtup_init(newsk);
924         tcp_sync_mss(newsk, dst_mtu(dst));
925         newtp->advmss = dst_metric(dst, RTAX_ADVMSS);
926         tcp_initialize_rcv_mss(newsk);
927
928         __inet_hash(&tcp_hashinfo, newsk, 0);
929         __inet_inherit_port(&tcp_hashinfo, sk, newsk);
930
931         return newsk;
932
933 exit_overflow:
934         NET_INC_STATS_BH(LINUX_MIB_LISTENOVERFLOWS);
935 exit:
936         NET_INC_STATS_BH(LINUX_MIB_LISTENDROPS);
937         dst_release(dst);
938         return NULL;
939 }
940
941 static struct sock *tcp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
942 {
943         struct tcphdr *th = skb->h.th;
944         struct iphdr *iph = skb->nh.iph;
945         struct sock *nsk;
946         struct request_sock **prev;
947         /* Find possible connection requests. */
948         struct request_sock *req = inet_csk_search_req(sk, &prev, th->source,
949                                                        iph->saddr, iph->daddr);
950         if (req)
951                 return tcp_check_req(sk, skb, req, prev);
952
953         nsk = __inet_lookup_established(&tcp_hashinfo, skb->nh.iph->saddr,
954                                         th->source, skb->nh.iph->daddr,
955                                         ntohs(th->dest), inet_iif(skb));
956
957         if (nsk) {
958                 if (nsk->sk_state != TCP_TIME_WAIT) {
959                         bh_lock_sock(nsk);
960                         return nsk;
961                 }
962                 inet_twsk_put((struct inet_timewait_sock *)nsk);
963                 return NULL;
964         }
965
966 #ifdef CONFIG_SYN_COOKIES
967         if (!th->rst && !th->syn && th->ack)
968                 sk = cookie_v4_check(sk, skb, &(IPCB(skb)->opt));
969 #endif
970         return sk;
971 }
972
973 static int tcp_v4_checksum_init(struct sk_buff *skb)
974 {
975         if (skb->ip_summed == CHECKSUM_HW) {
976                 if (!tcp_v4_check(skb->h.th, skb->len, skb->nh.iph->saddr,
977                                   skb->nh.iph->daddr, skb->csum)) {
978                         skb->ip_summed = CHECKSUM_UNNECESSARY;
979                         return 0;
980                 }
981         }
982
983         skb->csum = csum_tcpudp_nofold(skb->nh.iph->saddr, skb->nh.iph->daddr,
984                                        skb->len, IPPROTO_TCP, 0);
985
986         if (skb->len <= 76) {
987                 return __skb_checksum_complete(skb);
988         }
989         return 0;
990 }
991
992
993 /* The socket must have it's spinlock held when we get
994  * here.
995  *
996  * We have a potential double-lock case here, so even when
997  * doing backlog processing we use the BH locking scheme.
998  * This is because we cannot sleep with the original spinlock
999  * held.
1000  */
1001 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
1002 {
1003         if (sk->sk_state == TCP_ESTABLISHED) { /* Fast path */
1004                 TCP_CHECK_TIMER(sk);
1005                 if (tcp_rcv_established(sk, skb, skb->h.th, skb->len))
1006                         goto reset;
1007                 TCP_CHECK_TIMER(sk);
1008                 return 0;
1009         }
1010
1011         if (skb->len < (skb->h.th->doff << 2) || tcp_checksum_complete(skb))
1012                 goto csum_err;
1013
1014         if (sk->sk_state == TCP_LISTEN) {
1015                 struct sock *nsk = tcp_v4_hnd_req(sk, skb);
1016                 if (!nsk)
1017                         goto discard;
1018
1019                 if (nsk != sk) {
1020                         if (tcp_child_process(sk, nsk, skb))
1021                                 goto reset;
1022                         return 0;
1023                 }
1024         }
1025
1026         TCP_CHECK_TIMER(sk);
1027         if (tcp_rcv_state_process(sk, skb, skb->h.th, skb->len))
1028                 goto reset;
1029         TCP_CHECK_TIMER(sk);
1030         return 0;
1031
1032 reset:
1033         tcp_v4_send_reset(skb);
1034 discard:
1035         kfree_skb(skb);
1036         /* Be careful here. If this function gets more complicated and
1037          * gcc suffers from register pressure on the x86, sk (in %ebx)
1038          * might be destroyed here. This current version compiles correctly,
1039          * but you have been warned.
1040          */
1041         return 0;
1042
1043 csum_err:
1044         TCP_INC_STATS_BH(TCP_MIB_INERRS);
1045         goto discard;
1046 }
1047
1048 /*
1049  *      From tcp_input.c
1050  */
1051
1052 int tcp_v4_rcv(struct sk_buff *skb)
1053 {
1054         struct tcphdr *th;
1055         struct sock *sk;
1056         int ret;
1057
1058         if (skb->pkt_type != PACKET_HOST)
1059                 goto discard_it;
1060
1061         /* Count it even if it's bad */
1062         TCP_INC_STATS_BH(TCP_MIB_INSEGS);
1063
1064         if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
1065                 goto discard_it;
1066
1067         th = skb->h.th;
1068
1069         if (th->doff < sizeof(struct tcphdr) / 4)
1070                 goto bad_packet;
1071         if (!pskb_may_pull(skb, th->doff * 4))
1072                 goto discard_it;
1073
1074         /* An explanation is required here, I think.
1075          * Packet length and doff are validated by header prediction,
1076          * provided case of th->doff==0 is eliminated.
1077          * So, we defer the checks. */
1078         if ((skb->ip_summed != CHECKSUM_UNNECESSARY &&
1079              tcp_v4_checksum_init(skb)))
1080                 goto bad_packet;
1081
1082         th = skb->h.th;
1083         TCP_SKB_CB(skb)->seq = ntohl(th->seq);
1084         TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
1085                                     skb->len - th->doff * 4);
1086         TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
1087         TCP_SKB_CB(skb)->when    = 0;
1088         TCP_SKB_CB(skb)->flags   = skb->nh.iph->tos;
1089         TCP_SKB_CB(skb)->sacked  = 0;
1090
1091         sk = __inet_lookup(&tcp_hashinfo, skb->nh.iph->saddr, th->source,
1092                            skb->nh.iph->daddr, ntohs(th->dest),
1093                            inet_iif(skb));
1094
1095         if (!sk)
1096                 goto no_tcp_socket;
1097
1098 process:
1099         if (sk->sk_state == TCP_TIME_WAIT)
1100                 goto do_time_wait;
1101
1102         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
1103                 goto discard_and_relse;
1104         nf_reset(skb);
1105
1106         if (sk_filter(sk, skb, 0))
1107                 goto discard_and_relse;
1108
1109         skb->dev = NULL;
1110
1111         bh_lock_sock_nested(sk);
1112         ret = 0;
1113         if (!sock_owned_by_user(sk)) {
1114 #ifdef CONFIG_NET_DMA
1115                 struct tcp_sock *tp = tcp_sk(sk);
1116                 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
1117                         tp->ucopy.dma_chan = get_softnet_dma();
1118                 if (tp->ucopy.dma_chan)
1119                         ret = tcp_v4_do_rcv(sk, skb);
1120                 else
1121 #endif
1122                 {
1123                         if (!tcp_prequeue(sk, skb))
1124                         ret = tcp_v4_do_rcv(sk, skb);
1125                 }
1126         } else
1127                 sk_add_backlog(sk, skb);
1128         bh_unlock_sock(sk);
1129
1130         sock_put(sk);
1131
1132         return ret;
1133
1134 no_tcp_socket:
1135         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
1136                 goto discard_it;
1137
1138         if (skb->len < (th->doff << 2) || tcp_checksum_complete(skb)) {
1139 bad_packet:
1140                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
1141         } else {
1142                 tcp_v4_send_reset(skb);
1143         }
1144
1145 discard_it:
1146         /* Discard frame. */
1147         kfree_skb(skb);
1148         return 0;
1149
1150 discard_and_relse:
1151         sock_put(sk);
1152         goto discard_it;
1153
1154 do_time_wait:
1155         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
1156                 inet_twsk_put((struct inet_timewait_sock *) sk);
1157                 goto discard_it;
1158         }
1159
1160         if (skb->len < (th->doff << 2) || tcp_checksum_complete(skb)) {
1161                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
1162                 inet_twsk_put((struct inet_timewait_sock *) sk);
1163                 goto discard_it;
1164         }
1165         switch (tcp_timewait_state_process((struct inet_timewait_sock *)sk,
1166                                            skb, th)) {
1167         case TCP_TW_SYN: {
1168                 struct sock *sk2 = inet_lookup_listener(&tcp_hashinfo,
1169                                                         skb->nh.iph->daddr,
1170                                                         ntohs(th->dest),
1171                                                         inet_iif(skb));
1172                 if (sk2) {
1173                         inet_twsk_deschedule((struct inet_timewait_sock *)sk,
1174                                              &tcp_death_row);
1175                         inet_twsk_put((struct inet_timewait_sock *)sk);
1176                         sk = sk2;
1177                         goto process;
1178                 }
1179                 /* Fall through to ACK */
1180         }
1181         case TCP_TW_ACK:
1182                 tcp_v4_timewait_ack(sk, skb);
1183                 break;
1184         case TCP_TW_RST:
1185                 goto no_tcp_socket;
1186         case TCP_TW_SUCCESS:;
1187         }
1188         goto discard_it;
1189 }
1190
1191 /* VJ's idea. Save last timestamp seen from this destination
1192  * and hold it at least for normal timewait interval to use for duplicate
1193  * segment detection in subsequent connections, before they enter synchronized
1194  * state.
1195  */
1196
1197 int tcp_v4_remember_stamp(struct sock *sk)
1198 {
1199         struct inet_sock *inet = inet_sk(sk);
1200         struct tcp_sock *tp = tcp_sk(sk);
1201         struct rtable *rt = (struct rtable *)__sk_dst_get(sk);
1202         struct inet_peer *peer = NULL;
1203         int release_it = 0;
1204
1205         if (!rt || rt->rt_dst != inet->daddr) {
1206                 peer = inet_getpeer(inet->daddr, 1);
1207                 release_it = 1;
1208         } else {
1209                 if (!rt->peer)
1210                         rt_bind_peer(rt, 1);
1211                 peer = rt->peer;
1212         }
1213
1214         if (peer) {
1215                 if ((s32)(peer->tcp_ts - tp->rx_opt.ts_recent) <= 0 ||
1216                     (peer->tcp_ts_stamp + TCP_PAWS_MSL < xtime.tv_sec &&
1217                      peer->tcp_ts_stamp <= tp->rx_opt.ts_recent_stamp)) {
1218                         peer->tcp_ts_stamp = tp->rx_opt.ts_recent_stamp;
1219                         peer->tcp_ts = tp->rx_opt.ts_recent;
1220                 }
1221                 if (release_it)
1222                         inet_putpeer(peer);
1223                 return 1;
1224         }
1225
1226         return 0;
1227 }
1228
1229 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw)
1230 {
1231         struct inet_peer *peer = inet_getpeer(tw->tw_daddr, 1);
1232
1233         if (peer) {
1234                 const struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
1235
1236                 if ((s32)(peer->tcp_ts - tcptw->tw_ts_recent) <= 0 ||
1237                     (peer->tcp_ts_stamp + TCP_PAWS_MSL < xtime.tv_sec &&
1238                      peer->tcp_ts_stamp <= tcptw->tw_ts_recent_stamp)) {
1239                         peer->tcp_ts_stamp = tcptw->tw_ts_recent_stamp;
1240                         peer->tcp_ts       = tcptw->tw_ts_recent;
1241                 }
1242                 inet_putpeer(peer);
1243                 return 1;
1244         }
1245
1246         return 0;
1247 }
1248
1249 struct inet_connection_sock_af_ops ipv4_specific = {
1250         .queue_xmit        = ip_queue_xmit,
1251         .send_check        = tcp_v4_send_check,
1252         .rebuild_header    = inet_sk_rebuild_header,
1253         .conn_request      = tcp_v4_conn_request,
1254         .syn_recv_sock     = tcp_v4_syn_recv_sock,
1255         .remember_stamp    = tcp_v4_remember_stamp,
1256         .net_header_len    = sizeof(struct iphdr),
1257         .setsockopt        = ip_setsockopt,
1258         .getsockopt        = ip_getsockopt,
1259         .addr2sockaddr     = inet_csk_addr2sockaddr,
1260         .sockaddr_len      = sizeof(struct sockaddr_in),
1261 #ifdef CONFIG_COMPAT
1262         .compat_setsockopt = compat_ip_setsockopt,
1263         .compat_getsockopt = compat_ip_getsockopt,
1264 #endif
1265 };
1266
1267 /* NOTE: A lot of things set to zero explicitly by call to
1268  *       sk_alloc() so need not be done here.
1269  */
1270 static int tcp_v4_init_sock(struct sock *sk)
1271 {
1272         struct inet_connection_sock *icsk = inet_csk(sk);
1273         struct tcp_sock *tp = tcp_sk(sk);
1274
1275         skb_queue_head_init(&tp->out_of_order_queue);
1276         tcp_init_xmit_timers(sk);
1277         tcp_prequeue_init(tp);
1278
1279         icsk->icsk_rto = TCP_TIMEOUT_INIT;
1280         tp->mdev = TCP_TIMEOUT_INIT;
1281
1282         /* So many TCP implementations out there (incorrectly) count the
1283          * initial SYN frame in their delayed-ACK and congestion control
1284          * algorithms that we must have the following bandaid to talk
1285          * efficiently to them.  -DaveM
1286          */
1287         tp->snd_cwnd = 2;
1288
1289         /* See draft-stevens-tcpca-spec-01 for discussion of the
1290          * initialization of these values.
1291          */
1292         tp->snd_ssthresh = 0x7fffffff;  /* Infinity */
1293         tp->snd_cwnd_clamp = ~0;
1294         tp->mss_cache = 536;
1295
1296         tp->reordering = sysctl_tcp_reordering;
1297         icsk->icsk_ca_ops = &tcp_init_congestion_ops;
1298
1299         sk->sk_state = TCP_CLOSE;
1300
1301         sk->sk_write_space = sk_stream_write_space;
1302         sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1303
1304         icsk->icsk_af_ops = &ipv4_specific;
1305         icsk->icsk_sync_mss = tcp_sync_mss;
1306
1307         sk->sk_sndbuf = sysctl_tcp_wmem[1];
1308         sk->sk_rcvbuf = sysctl_tcp_rmem[1];
1309
1310         atomic_inc(&tcp_sockets_allocated);
1311
1312         return 0;
1313 }
1314
1315 int tcp_v4_destroy_sock(struct sock *sk)
1316 {
1317         struct tcp_sock *tp = tcp_sk(sk);
1318
1319         tcp_clear_xmit_timers(sk);
1320
1321         tcp_cleanup_congestion_control(sk);
1322
1323         /* Cleanup up the write buffer. */
1324         sk_stream_writequeue_purge(sk);
1325
1326         /* Cleans up our, hopefully empty, out_of_order_queue. */
1327         __skb_queue_purge(&tp->out_of_order_queue);
1328
1329 #ifdef CONFIG_NET_DMA
1330         /* Cleans up our sk_async_wait_queue */
1331         __skb_queue_purge(&sk->sk_async_wait_queue);
1332 #endif
1333
1334         /* Clean prequeue, it must be empty really */
1335         __skb_queue_purge(&tp->ucopy.prequeue);
1336
1337         /* Clean up a referenced TCP bind bucket. */
1338         if (inet_csk(sk)->icsk_bind_hash)
1339                 inet_put_port(&tcp_hashinfo, sk);
1340
1341         /*
1342          * If sendmsg cached page exists, toss it.
1343          */
1344         if (sk->sk_sndmsg_page) {
1345                 __free_page(sk->sk_sndmsg_page);
1346                 sk->sk_sndmsg_page = NULL;
1347         }
1348
1349         atomic_dec(&tcp_sockets_allocated);
1350
1351         return 0;
1352 }
1353
1354 EXPORT_SYMBOL(tcp_v4_destroy_sock);
1355
1356 #ifdef CONFIG_PROC_FS
1357 /* Proc filesystem TCP sock list dumping. */
1358
1359 static inline struct inet_timewait_sock *tw_head(struct hlist_head *head)
1360 {
1361         return hlist_empty(head) ? NULL :
1362                 list_entry(head->first, struct inet_timewait_sock, tw_node);
1363 }
1364
1365 static inline struct inet_timewait_sock *tw_next(struct inet_timewait_sock *tw)
1366 {
1367         return tw->tw_node.next ?
1368                 hlist_entry(tw->tw_node.next, typeof(*tw), tw_node) : NULL;
1369 }
1370
1371 static void *listening_get_next(struct seq_file *seq, void *cur)
1372 {
1373         struct inet_connection_sock *icsk;
1374         struct hlist_node *node;
1375         struct sock *sk = cur;
1376         struct tcp_iter_state* st = seq->private;
1377
1378         if (!sk) {
1379                 st->bucket = 0;
1380                 sk = sk_head(&tcp_hashinfo.listening_hash[0]);
1381                 goto get_sk;
1382         }
1383
1384         ++st->num;
1385
1386         if (st->state == TCP_SEQ_STATE_OPENREQ) {
1387                 struct request_sock *req = cur;
1388
1389                 icsk = inet_csk(st->syn_wait_sk);
1390                 req = req->dl_next;
1391                 while (1) {
1392                         while (req) {
1393                                 if (req->rsk_ops->family == st->family) {
1394                                         cur = req;
1395                                         goto out;
1396                                 }
1397                                 req = req->dl_next;
1398                         }
1399                         if (++st->sbucket >= TCP_SYNQ_HSIZE)
1400                                 break;
1401 get_req:
1402                         req = icsk->icsk_accept_queue.listen_opt->syn_table[st->sbucket];
1403                 }
1404                 sk        = sk_next(st->syn_wait_sk);
1405                 st->state = TCP_SEQ_STATE_LISTENING;
1406                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1407         } else {
1408                 icsk = inet_csk(sk);
1409                 read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1410                 if (reqsk_queue_len(&icsk->icsk_accept_queue))
1411                         goto start_req;
1412                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1413                 sk = sk_next(sk);
1414         }
1415 get_sk:
1416         sk_for_each_from(sk, node) {
1417                 if (sk->sk_family == st->family) {
1418                         cur = sk;
1419                         goto out;
1420                 }
1421                 icsk = inet_csk(sk);
1422                 read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1423                 if (reqsk_queue_len(&icsk->icsk_accept_queue)) {
1424 start_req:
1425                         st->uid         = sock_i_uid(sk);
1426                         st->syn_wait_sk = sk;
1427                         st->state       = TCP_SEQ_STATE_OPENREQ;
1428                         st->sbucket     = 0;
1429                         goto get_req;
1430                 }
1431                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1432         }
1433         if (++st->bucket < INET_LHTABLE_SIZE) {
1434                 sk = sk_head(&tcp_hashinfo.listening_hash[st->bucket]);
1435                 goto get_sk;
1436         }
1437         cur = NULL;
1438 out:
1439         return cur;
1440 }
1441
1442 static void *listening_get_idx(struct seq_file *seq, loff_t *pos)
1443 {
1444         void *rc = listening_get_next(seq, NULL);
1445
1446         while (rc && *pos) {
1447                 rc = listening_get_next(seq, rc);
1448                 --*pos;
1449         }
1450         return rc;
1451 }
1452
1453 static void *established_get_first(struct seq_file *seq)
1454 {
1455         struct tcp_iter_state* st = seq->private;
1456         void *rc = NULL;
1457
1458         for (st->bucket = 0; st->bucket < tcp_hashinfo.ehash_size; ++st->bucket) {
1459                 struct sock *sk;
1460                 struct hlist_node *node;
1461                 struct inet_timewait_sock *tw;
1462
1463                 /* We can reschedule _before_ having picked the target: */
1464                 cond_resched_softirq();
1465
1466                 read_lock(&tcp_hashinfo.ehash[st->bucket].lock);
1467                 sk_for_each(sk, node, &tcp_hashinfo.ehash[st->bucket].chain) {
1468                         if (sk->sk_family != st->family) {
1469                                 continue;
1470                         }
1471                         rc = sk;
1472                         goto out;
1473                 }
1474                 st->state = TCP_SEQ_STATE_TIME_WAIT;
1475                 inet_twsk_for_each(tw, node,
1476                                    &tcp_hashinfo.ehash[st->bucket + tcp_hashinfo.ehash_size].chain) {
1477                         if (tw->tw_family != st->family) {
1478                                 continue;
1479                         }
1480                         rc = tw;
1481                         goto out;
1482                 }
1483                 read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1484                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1485         }
1486 out:
1487         return rc;
1488 }
1489
1490 static void *established_get_next(struct seq_file *seq, void *cur)
1491 {
1492         struct sock *sk = cur;
1493         struct inet_timewait_sock *tw;
1494         struct hlist_node *node;
1495         struct tcp_iter_state* st = seq->private;
1496
1497         ++st->num;
1498
1499         if (st->state == TCP_SEQ_STATE_TIME_WAIT) {
1500                 tw = cur;
1501                 tw = tw_next(tw);
1502 get_tw:
1503                 while (tw && tw->tw_family != st->family) {
1504                         tw = tw_next(tw);
1505                 }
1506                 if (tw) {
1507                         cur = tw;
1508                         goto out;
1509                 }
1510                 read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1511                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1512
1513                 /* We can reschedule between buckets: */
1514                 cond_resched_softirq();
1515
1516                 if (++st->bucket < tcp_hashinfo.ehash_size) {
1517                         read_lock(&tcp_hashinfo.ehash[st->bucket].lock);
1518                         sk = sk_head(&tcp_hashinfo.ehash[st->bucket].chain);
1519                 } else {
1520                         cur = NULL;
1521                         goto out;
1522                 }
1523         } else
1524                 sk = sk_next(sk);
1525
1526         sk_for_each_from(sk, node) {
1527                 if (sk->sk_family == st->family)
1528                         goto found;
1529         }
1530
1531         st->state = TCP_SEQ_STATE_TIME_WAIT;
1532         tw = tw_head(&tcp_hashinfo.ehash[st->bucket + tcp_hashinfo.ehash_size].chain);
1533         goto get_tw;
1534 found:
1535         cur = sk;
1536 out:
1537         return cur;
1538 }
1539
1540 static void *established_get_idx(struct seq_file *seq, loff_t pos)
1541 {
1542         void *rc = established_get_first(seq);
1543
1544         while (rc && pos) {
1545                 rc = established_get_next(seq, rc);
1546                 --pos;
1547         }               
1548         return rc;
1549 }
1550
1551 static void *tcp_get_idx(struct seq_file *seq, loff_t pos)
1552 {
1553         void *rc;
1554         struct tcp_iter_state* st = seq->private;
1555
1556         inet_listen_lock(&tcp_hashinfo);
1557         st->state = TCP_SEQ_STATE_LISTENING;
1558         rc        = listening_get_idx(seq, &pos);
1559
1560         if (!rc) {
1561                 inet_listen_unlock(&tcp_hashinfo);
1562                 local_bh_disable();
1563                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1564                 rc        = established_get_idx(seq, pos);
1565         }
1566
1567         return rc;
1568 }
1569
1570 static void *tcp_seq_start(struct seq_file *seq, loff_t *pos)
1571 {
1572         struct tcp_iter_state* st = seq->private;
1573         st->state = TCP_SEQ_STATE_LISTENING;
1574         st->num = 0;
1575         return *pos ? tcp_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
1576 }
1577
1578 static void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
1579 {
1580         void *rc = NULL;
1581         struct tcp_iter_state* st;
1582
1583         if (v == SEQ_START_TOKEN) {
1584                 rc = tcp_get_idx(seq, 0);
1585                 goto out;
1586         }
1587         st = seq->private;
1588
1589         switch (st->state) {
1590         case TCP_SEQ_STATE_OPENREQ:
1591         case TCP_SEQ_STATE_LISTENING:
1592                 rc = listening_get_next(seq, v);
1593                 if (!rc) {
1594                         inet_listen_unlock(&tcp_hashinfo);
1595                         local_bh_disable();
1596                         st->state = TCP_SEQ_STATE_ESTABLISHED;
1597                         rc        = established_get_first(seq);
1598                 }
1599                 break;
1600         case TCP_SEQ_STATE_ESTABLISHED:
1601         case TCP_SEQ_STATE_TIME_WAIT:
1602                 rc = established_get_next(seq, v);
1603                 break;
1604         }
1605 out:
1606         ++*pos;
1607         return rc;
1608 }
1609
1610 static void tcp_seq_stop(struct seq_file *seq, void *v)
1611 {
1612         struct tcp_iter_state* st = seq->private;
1613
1614         switch (st->state) {
1615         case TCP_SEQ_STATE_OPENREQ:
1616                 if (v) {
1617                         struct inet_connection_sock *icsk = inet_csk(st->syn_wait_sk);
1618                         read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1619                 }
1620         case TCP_SEQ_STATE_LISTENING:
1621                 if (v != SEQ_START_TOKEN)
1622                         inet_listen_unlock(&tcp_hashinfo);
1623                 break;
1624         case TCP_SEQ_STATE_TIME_WAIT:
1625         case TCP_SEQ_STATE_ESTABLISHED:
1626                 if (v)
1627                         read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1628                 local_bh_enable();
1629                 break;
1630         }
1631 }
1632
1633 static int tcp_seq_open(struct inode *inode, struct file *file)
1634 {
1635         struct tcp_seq_afinfo *afinfo = PDE(inode)->data;
1636         struct seq_file *seq;
1637         struct tcp_iter_state *s;
1638         int rc;
1639
1640         if (unlikely(afinfo == NULL))
1641                 return -EINVAL;
1642
1643         s = kzalloc(sizeof(*s), GFP_KERNEL);
1644         if (!s)
1645                 return -ENOMEM;
1646         s->family               = afinfo->family;
1647         s->seq_ops.start        = tcp_seq_start;
1648         s->seq_ops.next         = tcp_seq_next;
1649         s->seq_ops.show         = afinfo->seq_show;
1650         s->seq_ops.stop         = tcp_seq_stop;
1651
1652         rc = seq_open(file, &s->seq_ops);
1653         if (rc)
1654                 goto out_kfree;
1655         seq          = file->private_data;
1656         seq->private = s;
1657 out:
1658         return rc;
1659 out_kfree:
1660         kfree(s);
1661         goto out;
1662 }
1663
1664 int tcp_proc_register(struct tcp_seq_afinfo *afinfo)
1665 {
1666         int rc = 0;
1667         struct proc_dir_entry *p;
1668
1669         if (!afinfo)
1670                 return -EINVAL;
1671         afinfo->seq_fops->owner         = afinfo->owner;
1672         afinfo->seq_fops->open          = tcp_seq_open;
1673         afinfo->seq_fops->read          = seq_read;
1674         afinfo->seq_fops->llseek        = seq_lseek;
1675         afinfo->seq_fops->release       = seq_release_private;
1676         
1677         p = proc_net_fops_create(afinfo->name, S_IRUGO, afinfo->seq_fops);
1678         if (p)
1679                 p->data = afinfo;
1680         else
1681                 rc = -ENOMEM;
1682         return rc;
1683 }
1684
1685 void tcp_proc_unregister(struct tcp_seq_afinfo *afinfo)
1686 {
1687         if (!afinfo)
1688                 return;
1689         proc_net_remove(afinfo->name);
1690         memset(afinfo->seq_fops, 0, sizeof(*afinfo->seq_fops)); 
1691 }
1692
1693 static void get_openreq4(struct sock *sk, struct request_sock *req,
1694                          char *tmpbuf, int i, int uid)
1695 {
1696         const struct inet_request_sock *ireq = inet_rsk(req);
1697         int ttd = req->expires - jiffies;
1698
1699         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
1700                 " %02X %08X:%08X %02X:%08lX %08X %5d %8d %u %d %p",
1701                 i,
1702                 ireq->loc_addr,
1703                 ntohs(inet_sk(sk)->sport),
1704                 ireq->rmt_addr,
1705                 ntohs(ireq->rmt_port),
1706                 TCP_SYN_RECV,
1707                 0, 0, /* could print option size, but that is af dependent. */
1708                 1,    /* timers active (only the expire timer) */
1709                 jiffies_to_clock_t(ttd),
1710                 req->retrans,
1711                 uid,
1712                 0,  /* non standard timer */
1713                 0, /* open_requests have no inode */
1714                 atomic_read(&sk->sk_refcnt),
1715                 req);
1716 }
1717
1718 static void get_tcp4_sock(struct sock *sp, char *tmpbuf, int i)
1719 {
1720         int timer_active;
1721         unsigned long timer_expires;
1722         struct tcp_sock *tp = tcp_sk(sp);
1723         const struct inet_connection_sock *icsk = inet_csk(sp);
1724         struct inet_sock *inet = inet_sk(sp);
1725         unsigned int dest = inet->daddr;
1726         unsigned int src = inet->rcv_saddr;
1727         __u16 destp = ntohs(inet->dport);
1728         __u16 srcp = ntohs(inet->sport);
1729
1730         if (icsk->icsk_pending == ICSK_TIME_RETRANS) {
1731                 timer_active    = 1;
1732                 timer_expires   = icsk->icsk_timeout;
1733         } else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
1734                 timer_active    = 4;
1735                 timer_expires   = icsk->icsk_timeout;
1736         } else if (timer_pending(&sp->sk_timer)) {
1737                 timer_active    = 2;
1738                 timer_expires   = sp->sk_timer.expires;
1739         } else {
1740                 timer_active    = 0;
1741                 timer_expires = jiffies;
1742         }
1743
1744         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X %02X %08X:%08X %02X:%08lX "
1745                         "%08X %5d %8d %lu %d %p %u %u %u %u %d",
1746                 i, src, srcp, dest, destp, sp->sk_state,
1747                 tp->write_seq - tp->snd_una,
1748                 (sp->sk_state == TCP_LISTEN) ? sp->sk_ack_backlog : (tp->rcv_nxt - tp->copied_seq),
1749                 timer_active,
1750                 jiffies_to_clock_t(timer_expires - jiffies),
1751                 icsk->icsk_retransmits,
1752                 sock_i_uid(sp),
1753                 icsk->icsk_probes_out,
1754                 sock_i_ino(sp),
1755                 atomic_read(&sp->sk_refcnt), sp,
1756                 icsk->icsk_rto,
1757                 icsk->icsk_ack.ato,
1758                 (icsk->icsk_ack.quick << 1) | icsk->icsk_ack.pingpong,
1759                 tp->snd_cwnd,
1760                 tp->snd_ssthresh >= 0xFFFF ? -1 : tp->snd_ssthresh);
1761 }
1762
1763 static void get_timewait4_sock(struct inet_timewait_sock *tw, char *tmpbuf, int i)
1764 {
1765         unsigned int dest, src;
1766         __u16 destp, srcp;
1767         int ttd = tw->tw_ttd - jiffies;
1768
1769         if (ttd < 0)
1770                 ttd = 0;
1771
1772         dest  = tw->tw_daddr;
1773         src   = tw->tw_rcv_saddr;
1774         destp = ntohs(tw->tw_dport);
1775         srcp  = ntohs(tw->tw_sport);
1776
1777         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
1778                 " %02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %p",
1779                 i, src, srcp, dest, destp, tw->tw_substate, 0, 0,
1780                 3, jiffies_to_clock_t(ttd), 0, 0, 0, 0,
1781                 atomic_read(&tw->tw_refcnt), tw);
1782 }
1783
1784 #define TMPSZ 150
1785
1786 static int tcp4_seq_show(struct seq_file *seq, void *v)
1787 {
1788         struct tcp_iter_state* st;
1789         char tmpbuf[TMPSZ + 1];
1790
1791         if (v == SEQ_START_TOKEN) {
1792                 seq_printf(seq, "%-*s\n", TMPSZ - 1,
1793                            "  sl  local_address rem_address   st tx_queue "
1794                            "rx_queue tr tm->when retrnsmt   uid  timeout "
1795                            "inode");
1796                 goto out;
1797         }
1798         st = seq->private;
1799
1800         switch (st->state) {
1801         case TCP_SEQ_STATE_LISTENING:
1802         case TCP_SEQ_STATE_ESTABLISHED:
1803                 get_tcp4_sock(v, tmpbuf, st->num);
1804                 break;
1805         case TCP_SEQ_STATE_OPENREQ:
1806                 get_openreq4(st->syn_wait_sk, v, tmpbuf, st->num, st->uid);
1807                 break;
1808         case TCP_SEQ_STATE_TIME_WAIT:
1809                 get_timewait4_sock(v, tmpbuf, st->num);
1810                 break;
1811         }
1812         seq_printf(seq, "%-*s\n", TMPSZ - 1, tmpbuf);
1813 out:
1814         return 0;
1815 }
1816
1817 static struct file_operations tcp4_seq_fops;
1818 static struct tcp_seq_afinfo tcp4_seq_afinfo = {
1819         .owner          = THIS_MODULE,
1820         .name           = "tcp",
1821         .family         = AF_INET,
1822         .seq_show       = tcp4_seq_show,
1823         .seq_fops       = &tcp4_seq_fops,
1824 };
1825
1826 int __init tcp4_proc_init(void)
1827 {
1828         return tcp_proc_register(&tcp4_seq_afinfo);
1829 }
1830
1831 void tcp4_proc_exit(void)
1832 {
1833         tcp_proc_unregister(&tcp4_seq_afinfo);
1834 }
1835 #endif /* CONFIG_PROC_FS */
1836
1837 struct proto tcp_prot = {
1838         .name                   = "TCP",
1839         .owner                  = THIS_MODULE,
1840         .close                  = tcp_close,
1841         .connect                = tcp_v4_connect,
1842         .disconnect             = tcp_disconnect,
1843         .accept                 = inet_csk_accept,
1844         .ioctl                  = tcp_ioctl,
1845         .init                   = tcp_v4_init_sock,
1846         .destroy                = tcp_v4_destroy_sock,
1847         .shutdown               = tcp_shutdown,
1848         .setsockopt             = tcp_setsockopt,
1849         .getsockopt             = tcp_getsockopt,
1850         .sendmsg                = tcp_sendmsg,
1851         .recvmsg                = tcp_recvmsg,
1852         .backlog_rcv            = tcp_v4_do_rcv,
1853         .hash                   = tcp_v4_hash,
1854         .unhash                 = tcp_unhash,
1855         .get_port               = tcp_v4_get_port,
1856         .enter_memory_pressure  = tcp_enter_memory_pressure,
1857         .sockets_allocated      = &tcp_sockets_allocated,
1858         .orphan_count           = &tcp_orphan_count,
1859         .memory_allocated       = &tcp_memory_allocated,
1860         .memory_pressure        = &tcp_memory_pressure,
1861         .sysctl_mem             = sysctl_tcp_mem,
1862         .sysctl_wmem            = sysctl_tcp_wmem,
1863         .sysctl_rmem            = sysctl_tcp_rmem,
1864         .max_header             = MAX_TCP_HEADER,
1865         .obj_size               = sizeof(struct tcp_sock),
1866         .twsk_prot              = &tcp_timewait_sock_ops,
1867         .rsk_prot               = &tcp_request_sock_ops,
1868 #ifdef CONFIG_COMPAT
1869         .compat_setsockopt      = compat_tcp_setsockopt,
1870         .compat_getsockopt      = compat_tcp_getsockopt,
1871 #endif
1872 };
1873
1874 void __init tcp_v4_init(struct net_proto_family *ops)
1875 {
1876         if (inet_csk_ctl_sock_create(&tcp_socket, PF_INET, SOCK_RAW, IPPROTO_TCP) < 0)
1877                 panic("Failed to create the TCP control socket.\n");
1878 }
1879
1880 EXPORT_SYMBOL(ipv4_specific);
1881 EXPORT_SYMBOL(tcp_hashinfo);
1882 EXPORT_SYMBOL(tcp_prot);
1883 EXPORT_SYMBOL(tcp_unhash);
1884 EXPORT_SYMBOL(tcp_v4_conn_request);
1885 EXPORT_SYMBOL(tcp_v4_connect);
1886 EXPORT_SYMBOL(tcp_v4_do_rcv);
1887 EXPORT_SYMBOL(tcp_v4_remember_stamp);
1888 EXPORT_SYMBOL(tcp_v4_send_check);
1889 EXPORT_SYMBOL(tcp_v4_syn_recv_sock);
1890
1891 #ifdef CONFIG_PROC_FS
1892 EXPORT_SYMBOL(tcp_proc_register);
1893 EXPORT_SYMBOL(tcp_proc_unregister);
1894 #endif
1895 EXPORT_SYMBOL(sysctl_local_port_range);
1896 EXPORT_SYMBOL(sysctl_tcp_low_latency);
1897