net/ipv4/ip_output.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  *              The Internet Protocol (IP) output module.
   7  *
   8  * Version:     $Id: ip_output.c,v 1.100 2002/02/01 22:01:03 davem Exp $
   9  *
  10  * Authors:     Ross Biro
  11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  12  *              Donald Becker, <becker@super.org>
  13  *              Alan Cox, <Alan.Cox@linux.org>
  14  *              Richard Underwood
  15  *              Stefan Becker, <stefanb@yello.ping.de>
  16  *              Jorge Cwik, <jorge@laser.satlink.net>
  17  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  18  *              Hirokazu Takahashi, <taka@valinux.co.jp>
  19  *
  20  *      See ip_input.c for original log
  21  *
  22  *      Fixes:
  23  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
  24  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
  25  *              Bradford Johnson:       Fix faulty handling of some frames when
  26  *                                      no route is found.
  27  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
  28  *                                      (in case if packet not accepted by
  29  *                                      output firewall rules)
  30  *              Mike McLagan    :       Routing by source
  31  *              Alexey Kuznetsov:       use new route cache
  32  *              Andi Kleen:             Fix broken PMTU recovery and remove
  33  *                                      some redundant tests.
  34  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
  35  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
  36  *              Andi Kleen      :       Split fast and slow ip_build_xmit path
  37  *                                      for decreased register pressure on x86
  38  *                                      and more readibility.
  39  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
  40  *                                      silently drop skb instead of failing with -EPERM.
  41  *              Detlev Wengorz  :       Copy protocol for fragments.
  42  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
  43  *                                      datagrams.
  44  *              Hirokazu Takahashi:     sendfile() on UDP works now.
  45  */
  46
  47 #include <asm/uaccess.h>
  48 #include <asm/system.h>
  49 #include <linux/module.h>
  50 #include <linux/types.h>
  51 #include <linux/kernel.h>
  52 #include <linux/sched.h>
  53 #include <linux/mm.h>
  54 #include <linux/string.h>
  55 #include <linux/errno.h>
  56 #include <linux/config.h>
  57
  58 #include <linux/socket.h>
  59 #include <linux/sockios.h>
  60 #include <linux/in.h>
  61 #include <linux/inet.h>
  62 #include <linux/netdevice.h>
  63 #include <linux/etherdevice.h>
  64 #include <linux/proc_fs.h>
  65 #include <linux/stat.h>
  66 #include <linux/init.h>
  67
  68 #include <net/snmp.h>
  69 #include <net/ip.h>
  70 #include <net/protocol.h>
  71 #include <net/route.h>
  72 #include <linux/skbuff.h>
  73 #include <net/sock.h>
  74 #include <net/arp.h>
  75 #include <net/icmp.h>
  76 #include <net/checksum.h>
  77 #include <net/inetpeer.h>
  78 #include <net/checksum.h>
  79 #include <linux/igmp.h>
  80 #include <linux/netfilter_ipv4.h>
  81 #include <linux/netfilter_bridge.h>
  82 #include <linux/mroute.h>
  83 #include <linux/netlink.h>
  84 #include <linux/tcp.h>
  85
  86 int sysctl_ip_default_ttl = IPDEFTTL;
  87
  88 /* Generate a checksum for an outgoing IP datagram. */
  89 __inline__ void ip_send_check(struct iphdr *iph)
  90 {
  91         iph->check = 0;
  92         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
  93 }
  94
  95 /* dev_loopback_xmit for use with netfilter. */
  96 static int ip_dev_loopback_xmit(struct sk_buff *newskb)
  97 {
  98         newskb->mac.raw = newskb->data;
  99         __skb_pull(newskb, newskb->nh.raw - newskb->data);
 100         newskb->pkt_type = PACKET_LOOPBACK;
 101         newskb->ip_summed = CHECKSUM_UNNECESSARY;
 102         BUG_TRAP(newskb->dst);
 103         netif_rx(newskb);
 104         return 0;
 105 }
 106
 107 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
 108 {
 109         int ttl = inet->uc_ttl;
 110
 111         if (ttl < 0)
 112                 ttl = dst_metric(dst, RTAX_HOPLIMIT);
 113         return ttl;
 114 }
 115
 116 /*
 117  *              Add an ip header to a skbuff and send it out.
 118  *
 119  */
 120 int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
 121                           u32 saddr, u32 daddr, struct ip_options *opt)
 122 {
 123         struct inet_sock *inet = inet_sk(sk);
 124         struct rtable *rt = (struct rtable *)skb->dst;
 125         struct iphdr *iph;
 126
 127         /* Build the IP header. */
 128         if (opt)
 129                 iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr) + opt->optlen);
 130         else
 131                 iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr));
 132
 133         iph->version  = 4;
 134         iph->ihl      = 5;
 135         iph->tos      = inet->tos;
 136         if (ip_dont_fragment(sk, &rt->u.dst))
 137                 iph->frag_off = htons(IP_DF);
 138         else
 139                 iph->frag_off = 0;
 140         iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
 141         iph->daddr    = rt->rt_dst;
 142         iph->saddr    = rt->rt_src;
 143         iph->protocol = sk->sk_protocol;
 144         iph->tot_len  = htons(skb->len);
 145         ip_select_ident(iph, &rt->u.dst, sk);
 146         skb->nh.iph   = iph;
 147
 148         if (opt && opt->optlen) {
 149                 iph->ihl += opt->optlen>>2;
 150                 ip_options_build(skb, opt, daddr, rt, 0);
 151         }
 152         ip_send_check(iph);
 153
 154         skb->priority = sk->sk_priority;
 155
 156         /* Send it out. */
 157         return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev,
 158                        dst_output);
 159 }
 160
 161 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
 162
 163 static inline int ip_finish_output2(struct sk_buff *skb)
 164 {
 165         struct dst_entry *dst = skb->dst;
 166         struct hh_cache *hh = dst->hh;
 167         struct net_device *dev = dst->dev;
 168         int hh_len = LL_RESERVED_SPACE(dev);
 169
 170         /* Be paranoid, rather than too clever. */
 171         if (unlikely(skb_headroom(skb) < hh_len && dev->hard_header)) {
 172                 struct sk_buff *skb2;
 173
 174                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
 175                 if (skb2 == NULL) {
 176                         kfree_skb(skb);
 177                         return -ENOMEM;
 178                 }
 179                 if (skb->sk)
 180                         skb_set_owner_w(skb2, skb->sk);
 181                 kfree_skb(skb);
 182                 skb = skb2;
 183         }
 184
 185         if (hh) {
 186                 int hh_alen;
 187
 188                 read_lock_bh(&hh->hh_lock);
 189                 hh_alen = HH_DATA_ALIGN(hh->hh_len);
 190                 memcpy(skb->data - hh_alen, hh->hh_data, hh_alen);
 191                 read_unlock_bh(&hh->hh_lock);
 192                 skb_push(skb, hh->hh_len);
 193                 return hh->hh_output(skb);
 194         } else if (dst->neighbour)
 195                 return dst->neighbour->output(skb);
 196
 197         if (net_ratelimit())
 198                 printk(KERN_DEBUG "ip_finish_output2: No header cache and no neighbour!\n");
 199         kfree_skb(skb);
 200         return -EINVAL;
 201 }
 202
 203 static inline int ip_finish_output(struct sk_buff *skb)
 204 {
 205         if (skb->len > dst_mtu(skb->dst) &&
 206             !(skb_shinfo(skb)->ufo_size || skb_shinfo(skb)->tso_size))
 207                 return ip_fragment(skb, ip_finish_output2);
 208         else
 209                 return ip_finish_output2(skb);
 210 }
 211
 212 int ip_mc_output(struct sk_buff *skb)
 213 {
 214         struct sock *sk = skb->sk;
 215         struct rtable *rt = (struct rtable*)skb->dst;
 216         struct net_device *dev = rt->u.dst.dev;
 217
 218         /*
 219          *      If the indicated interface is up and running, send the packet.
 220          */
 221         IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
 222
 223         skb->dev = dev;
 224         skb->protocol = htons(ETH_P_IP);
 225
 226         /*
 227          *      Multicasts are looped back for other local users
 228          */
 229
 230         if (rt->rt_flags&RTCF_MULTICAST) {
 231                 if ((!sk || inet_sk(sk)->mc_loop)
 232 #ifdef CONFIG_IP_MROUTE
 233                 /* Small optimization: do not loopback not local frames,
 234                    which returned after forwarding; they will be  dropped
 235                    by ip_mr_input in any case.
 236                    Note, that local frames are looped back to be delivered
 237                    to local recipients.
 238
 239                    This check is duplicated in ip_mr_input at the moment.
 240                  */
 241                     && ((rt->rt_flags&RTCF_LOCAL) || !(IPCB(skb)->flags&IPSKB_FORWARDED))
 242 #endif
 243                 ) {
 244                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 245                         if (newskb)
 246                                 NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL,
 247                                         newskb->dev,
 248                                         ip_dev_loopback_xmit);
 249                 }
 250
 251                 /* Multicasts with ttl 0 must not go beyond the host */
 252
 253                 if (skb->nh.iph->ttl == 0) {
 254                         kfree_skb(skb);
 255                         return 0;
 256                 }
 257         }
 258
 259         if (rt->rt_flags&RTCF_BROADCAST) {
 260                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 261                 if (newskb)
 262                         NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL,
 263                                 newskb->dev, ip_dev_loopback_xmit);
 264         }
 265
 266         return NF_HOOK(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dev,
 267                        ip_finish_output);
 268 }
 269
 270 int ip_output(struct sk_buff *skb)
 271 {
 272         struct net_device *dev = skb->dst->dev;
 273
 274         IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
 275
 276         skb->dev = dev;
 277         skb->protocol = htons(ETH_P_IP);
 278
 279         return NF_HOOK(PF_INET, NF_IP_POST_ROUTING, skb, NULL, dev,
 280                        ip_finish_output);
 281 }
 282
 283 int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
 284 {
 285         struct sock *sk = skb->sk;
 286         struct inet_sock *inet = inet_sk(sk);
 287         struct ip_options *opt = inet->opt;
 288         struct rtable *rt;
 289         struct iphdr *iph;
 290
 291         /* Skip all of this if the packet is already routed,
 292          * f.e. by something like SCTP.
 293          */
 294         rt = (struct rtable *) skb->dst;
 295         if (rt != NULL)
 296                 goto packet_routed;
 297
 298         /* Make sure we can route this packet. */
 299         rt = (struct rtable *)__sk_dst_check(sk, 0);
 300         if (rt == NULL) {
 301                 u32 daddr;
 302
 303                 /* Use correct destination address if we have options. */
 304                 daddr = inet->daddr;
 305                 if(opt && opt->srr)
 306                         daddr = opt->faddr;
 307
 308                 {
 309                         struct flowi fl = { .oif = sk->sk_bound_dev_if,
 310                                             .nl_u = { .ip4_u =
 311                                                       { .daddr = daddr,
 312                                                         .saddr = inet->saddr,
 313                                                         .tos = RT_CONN_FLAGS(sk) } },
 314                                             .proto = sk->sk_protocol,
 315                                             .uli_u = { .ports =
 316                                                        { .sport = inet->sport,
 317                                                          .dport = inet->dport } } };
 318
 319                         /* If this fails, retransmit mechanism of transport layer will
 320                          * keep trying until route appears or the connection times
 321                          * itself out.
 322                          */
 323                         if (ip_route_output_flow(&rt, &fl, sk, 0))
 324                                 goto no_route;
 325                 }
 326                 sk_setup_caps(sk, &rt->u.dst);
 327         }
 328         skb->dst = dst_clone(&rt->u.dst);
 329
 330 packet_routed:
 331         if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
 332                 goto no_route;
 333
 334         /* OK, we know where to send it, allocate and build IP header. */
 335         iph = (struct iphdr *) skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
 336         *((__u16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
 337         iph->tot_len = htons(skb->len);
 338         if (ip_dont_fragment(sk, &rt->u.dst) && !ipfragok)
 339                 iph->frag_off = htons(IP_DF);
 340         else
 341                 iph->frag_off = 0;
 342         iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
 343         iph->protocol = sk->sk_protocol;
 344         iph->saddr    = rt->rt_src;
 345         iph->daddr    = rt->rt_dst;
 346         skb->nh.iph   = iph;
 347         /* Transport layer set skb->h.foo itself. */
 348
 349         if (opt && opt->optlen) {
 350                 iph->ihl += opt->optlen >> 2;
 351                 ip_options_build(skb, opt, inet->daddr, rt, 0);
 352         }
 353
 354         ip_select_ident_more(iph, &rt->u.dst, sk,
 355                              (skb_shinfo(skb)->tso_segs ?: 1) - 1);
 356
 357         /* Add an IP checksum. */
 358         ip_send_check(iph);
 359
 360         skb->priority = sk->sk_priority;
 361
 362         return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev,
 363                        dst_output);
 364
 365 no_route:
 366         IP_INC_STATS(IPSTATS_MIB_OUTNOROUTES);
 367         kfree_skb(skb);
 368         return -EHOSTUNREACH;
 369 }
 370
 371
 372 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 373 {
 374         to->pkt_type = from->pkt_type;
 375         to->priority = from->priority;
 376         to->protocol = from->protocol;
 377         dst_release(to->dst);
 378         to->dst = dst_clone(from->dst);
 379         to->dev = from->dev;
 380
 381         /* Copy the flags to each fragment. */
 382         IPCB(to)->flags = IPCB(from)->flags;
 383
 384 #ifdef CONFIG_NET_SCHED
 385         to->tc_index = from->tc_index;
 386 #endif
 387 #ifdef CONFIG_NETFILTER
 388         to->nfmark = from->nfmark;
 389         /* Connection association is same as pre-frag packet */
 390         nf_conntrack_put(to->nfct);
 391         to->nfct = from->nfct;
 392         nf_conntrack_get(to->nfct);
 393         to->nfctinfo = from->nfctinfo;
 394 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
 395         to->ipvs_property = from->ipvs_property;
 396 #endif
 397 #ifdef CONFIG_BRIDGE_NETFILTER
 398         nf_bridge_put(to->nf_bridge);
 399         to->nf_bridge = from->nf_bridge;
 400         nf_bridge_get(to->nf_bridge);
 401 #endif
 402 #endif
 403 }
 404
 405 /*
 406  *      This IP datagram is too large to be sent in one piece.  Break it up into
 407  *      smaller pieces (each of size equal to IP header plus
 408  *      a block of the data of the original IP data part) that will yet fit in a
 409  *      single device frame, and queue such a frame for sending.
 410  */
 411
 412 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 413 {
 414         struct iphdr *iph;
 415         int raw = 0;
 416         int ptr;
 417         struct net_device *dev;
 418         struct sk_buff *skb2;
 419         unsigned int mtu, hlen, left, len, ll_rs;
 420         int offset;
 421         int not_last_frag;
 422         struct rtable *rt = (struct rtable*)skb->dst;
 423         int err = 0;
 424
 425         dev = rt->u.dst.dev;
 426
 427         /*
 428          *      Point into the IP datagram header.
 429          */
 430
 431         iph = skb->nh.iph;
 432
 433         if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
 434                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 435                           htonl(dst_mtu(&rt->u.dst)));
 436                 kfree_skb(skb);
 437                 return -EMSGSIZE;
 438         }
 439
 440         /*
 441          *      Setup starting values.
 442          */
 443
 444         hlen = iph->ihl * 4;
 445         mtu = dst_mtu(&rt->u.dst) - hlen;       /* Size of data space */
 446         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
 447
 448         /* When frag_list is given, use it. First, check its validity:
 449          * some transformers could create wrong frag_list or break existing
 450          * one, it is not prohibited. In this case fall back to copying.
 451          *
 452          * LATER: this step can be merged to real generation of fragments,
 453          * we can switch to copy when see the first bad fragment.
 454          */
 455         if (skb_shinfo(skb)->frag_list) {
 456                 struct sk_buff *frag;
 457                 int first_len = skb_pagelen(skb);
 458
 459                 if (first_len - hlen > mtu ||
 460                     ((first_len - hlen) & 7) ||
 461                     (iph->frag_off & htons(IP_MF|IP_OFFSET)) ||
 462                     skb_cloned(skb))
 463                         goto slow_path;
 464
 465                 for (frag = skb_shinfo(skb)->frag_list; frag; frag = frag->next) {
 466                         /* Correct geometry. */
 467                         if (frag->len > mtu ||
 468                             ((frag->len & 7) && frag->next) ||
 469                             skb_headroom(frag) < hlen)
 470                             goto slow_path;
 471
 472                         /* Partially cloned skb? */
 473                         if (skb_shared(frag))
 474                                 goto slow_path;
 475
 476                         BUG_ON(frag->sk);
 477                         if (skb->sk) {
 478                                 sock_hold(skb->sk);
 479                                 frag->sk = skb->sk;
 480                                 frag->destructor = sock_wfree;
 481                                 skb->truesize -= frag->truesize;
 482                         }
 483                 }
 484
 485                 /* Everything is OK. Generate! */
 486
 487                 err = 0;
 488                 offset = 0;
 489                 frag = skb_shinfo(skb)->frag_list;
 490                 skb_shinfo(skb)->frag_list = NULL;
 491                 skb->data_len = first_len - skb_headlen(skb);
 492                 skb->len = first_len;
 493                 iph->tot_len = htons(first_len);
 494                 iph->frag_off = htons(IP_MF);
 495                 ip_send_check(iph);
 496
 497                 for (;;) {
 498                         /* Prepare header of the next frame,
 499                          * before previous one went down. */
 500                         if (frag) {
 501                                 frag->ip_summed = CHECKSUM_NONE;
 502                                 frag->h.raw = frag->data;
 503                                 frag->nh.raw = __skb_push(frag, hlen);
 504                                 memcpy(frag->nh.raw, iph, hlen);
 505                                 iph = frag->nh.iph;
 506                                 iph->tot_len = htons(frag->len);
 507                                 ip_copy_metadata(frag, skb);
 508                                 if (offset == 0)
 509                                         ip_options_fragment(frag);
 510                                 offset += skb->len - hlen;
 511                                 iph->frag_off = htons(offset>>3);
 512                                 if (frag->next != NULL)
 513                                         iph->frag_off |= htons(IP_MF);
 514                                 /* Ready, complete checksum */
 515                                 ip_send_check(iph);
 516                         }
 517
 518                         err = output(skb);
 519
 520                         if (err || !frag)
 521                                 break;
 522
 523                         skb = frag;
 524                         frag = skb->next;
 525                         skb->next = NULL;
 526                 }
 527
 528                 if (err == 0) {
 529                         IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
 530                         return 0;
 531                 }
 532
 533                 while (frag) {
 534                         skb = frag->next;
 535                         kfree_skb(frag);
 536                         frag = skb;
 537                 }
 538                 IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
 539                 return err;
 540         }
 541
 542 slow_path:
 543         left = skb->len - hlen;         /* Space per frame */
 544         ptr = raw + hlen;               /* Where to start from */
 545
 546 #ifdef CONFIG_BRIDGE_NETFILTER
 547         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
 548          * we need to make room for the encapsulating header */
 549         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, nf_bridge_pad(skb));
 550         mtu -= nf_bridge_pad(skb);
 551 #else
 552         ll_rs = LL_RESERVED_SPACE(rt->u.dst.dev);
 553 #endif
 554         /*
 555          *      Fragment the datagram.
 556          */
 557
 558         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
 559         not_last_frag = iph->frag_off & htons(IP_MF);
 560
 561         /*
 562          *      Keep copying data until we run out.
 563          */
 564
 565         while(left > 0) {
 566                 len = left;
 567                 /* IF: it doesn't fit, use 'mtu' - the data space left */
 568                 if (len > mtu)
 569                         len = mtu;
 570                 /* IF: we are not sending upto and including the packet end
 571                    then align the next start on an eight byte boundary */
 572                 if (len < left) {
 573                         len &= ~7;
 574                 }
 575                 /*
 576                  *      Allocate buffer.
 577                  */
 578
 579                 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
 580                         NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
 581                         err = -ENOMEM;
 582                         goto fail;
 583                 }
 584
 585                 /*
 586                  *      Set up data on packet
 587                  */
 588
 589                 ip_copy_metadata(skb2, skb);
 590                 skb_reserve(skb2, ll_rs);
 591                 skb_put(skb2, len + hlen);
 592                 skb2->nh.raw = skb2->data;
 593                 skb2->h.raw = skb2->data + hlen;
 594
 595                 /*
 596                  *      Charge the memory for the fragment to any owner
 597                  *      it might possess
 598                  */
 599
 600                 if (skb->sk)
 601                         skb_set_owner_w(skb2, skb->sk);
 602
 603                 /*
 604                  *      Copy the packet header into the new buffer.
 605                  */
 606
 607                 memcpy(skb2->nh.raw, skb->data, hlen);
 608
 609                 /*
 610                  *      Copy a block of the IP datagram.
 611                  */
 612                 if (skb_copy_bits(skb, ptr, skb2->h.raw, len))
 613                         BUG();
 614                 left -= len;
 615
 616                 /*
 617                  *      Fill in the new header fields.
 618                  */
 619                 iph = skb2->nh.iph;
 620                 iph->frag_off = htons((offset >> 3));
 621
 622                 /* ANK: dirty, but effective trick. Upgrade options only if
 623                  * the segment to be fragmented was THE FIRST (otherwise,
 624                  * options are already fixed) and make it ONCE
 625                  * on the initial skb, so that all the following fragments
 626                  * will inherit fixed options.
 627                  */
 628                 if (offset == 0)
 629                         ip_options_fragment(skb);
 630
 631                 /*
 632                  *      Added AC : If we are fragmenting a fragment that's not the
 633                  *                 last fragment then keep MF on each bit
 634                  */
 635                 if (left > 0 || not_last_frag)
 636                         iph->frag_off |= htons(IP_MF);
 637                 ptr += len;
 638                 offset += len;
 639
 640                 /*
 641                  *      Put this fragment into the sending queue.
 642                  */
 643
 644                 IP_INC_STATS(IPSTATS_MIB_FRAGCREATES);
 645
 646                 iph->tot_len = htons(len + hlen);
 647
 648                 ip_send_check(iph);
 649
 650                 err = output(skb2);
 651                 if (err)
 652                         goto fail;
 653         }
 654         kfree_skb(skb);
 655         IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
 656         return err;
 657
 658 fail:
 659         kfree_skb(skb);
 660         IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
 661         return err;
 662 }
 663
 664 int
 665 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
 666 {
 667         struct iovec *iov = from;
 668
 669         if (skb->ip_summed == CHECKSUM_HW) {
 670                 if (memcpy_fromiovecend(to, iov, offset, len) < 0)
 671                         return -EFAULT;
 672         } else {
 673                 unsigned int csum = 0;
 674                 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
 675                         return -EFAULT;
 676                 skb->csum = csum_block_add(skb->csum, csum, odd);
 677         }
 678         return 0;
 679 }
 680
 681 static inline unsigned int
 682 csum_page(struct page *page, int offset, int copy)
 683 {
 684         char *kaddr;
 685         unsigned int csum;
 686         kaddr = kmap(page);
 687         csum = csum_partial(kaddr + offset, copy, 0);
 688         kunmap(page);
 689         return csum;
 690 }
 691
 692 static inline int ip_ufo_append_data(struct sock *sk,
 693                         int getfrag(void *from, char *to, int offset, int len,
 694                                int odd, struct sk_buff *skb),
 695                         void *from, int length, int hh_len, int fragheaderlen,
 696                         int transhdrlen, int mtu,unsigned int flags)
 697 {
 698         struct sk_buff *skb;
 699         int err;
 700
 701         /* There is support for UDP fragmentation offload by network
 702          * device, so create one single skb packet containing complete
 703          * udp datagram
 704          */
 705         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
 706                 skb = sock_alloc_send_skb(sk,
 707                         hh_len + fragheaderlen + transhdrlen + 20,
 708                         (flags & MSG_DONTWAIT), &err);
 709
 710                 if (skb == NULL)
 711                         return err;
 712
 713                 /* reserve space for Hardware header */
 714                 skb_reserve(skb, hh_len);
 715
 716                 /* create space for UDP/IP header */
 717                 skb_put(skb,fragheaderlen + transhdrlen);
 718
 719                 /* initialize network header pointer */
 720                 skb->nh.raw = skb->data;
 721
 722                 /* initialize protocol header pointer */
 723                 skb->h.raw = skb->data + fragheaderlen;
 724
 725                 skb->ip_summed = CHECKSUM_HW;
 726                 skb->csum = 0;
 727                 sk->sk_sndmsg_off = 0;
 728         }
 729
 730         err = skb_append_datato_frags(sk,skb, getfrag, from,
 731                                (length - transhdrlen));
 732         if (!err) {
 733                 /* specify the length of each IP datagram fragment*/
 734                 skb_shinfo(skb)->ufo_size = (mtu - fragheaderlen);
 735                 __skb_queue_tail(&sk->sk_write_queue, skb);
 736
 737                 return 0;
 738         }
 739         /* There is not enough support do UFO ,
 740          * so follow normal path
 741          */
 742         kfree_skb(skb);
 743         return err;
 744 }
 745
 746 /*
 747  *      ip_append_data() and ip_append_page() can make one large IP datagram
 748  *      from many pieces of data. Each pieces will be holded on the socket
 749  *      until ip_push_pending_frames() is called. Each piece can be a page
 750  *      or non-page data.
 751  *
 752  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
 753  *      this interface potentially.
 754  *
 755  *      LATER: length must be adjusted by pad at tail, when it is required.
 756  */
 757 int ip_append_data(struct sock *sk,
 758                    int getfrag(void *from, char *to, int offset, int len,
 759                                int odd, struct sk_buff *skb),
 760                    void *from, int length, int transhdrlen,
 761                    struct ipcm_cookie *ipc, struct rtable *rt,
 762                    unsigned int flags)
 763 {
 764         struct inet_sock *inet = inet_sk(sk);
 765         struct sk_buff *skb;
 766
 767         struct ip_options *opt = NULL;
 768         int hh_len;
 769         int exthdrlen;
 770         int mtu;
 771         int copy;
 772         int err;
 773         int offset = 0;
 774         unsigned int maxfraglen, fragheaderlen;
 775         int csummode = CHECKSUM_NONE;
 776
 777         if (flags&MSG_PROBE)
 778                 return 0;
 779
 780         if (skb_queue_empty(&sk->sk_write_queue)) {
 781                 /*
 782                  * setup for corking.
 783                  */
 784                 opt = ipc->opt;
 785                 if (opt) {
 786                         if (inet->cork.opt == NULL) {
 787                                 inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation);
 788                                 if (unlikely(inet->cork.opt == NULL))
 789                                         return -ENOBUFS;
 790                         }
 791                         memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen);
 792                         inet->cork.flags |= IPCORK_OPT;
 793                         inet->cork.addr = ipc->addr;
 794                 }
 795                 dst_hold(&rt->u.dst);
 796                 inet->cork.fragsize = mtu = dst_mtu(rt->u.dst.path);
 797                 inet->cork.rt = rt;
 798                 inet->cork.length = 0;
 799                 sk->sk_sndmsg_page = NULL;
 800                 sk->sk_sndmsg_off = 0;
 801                 if ((exthdrlen = rt->u.dst.header_len) != 0) {
 802                         length += exthdrlen;
 803                         transhdrlen += exthdrlen;
 804                 }
 805         } else {
 806                 rt = inet->cork.rt;
 807                 if (inet->cork.flags & IPCORK_OPT)
 808                         opt = inet->cork.opt;
 809
 810                 transhdrlen = 0;
 811                 exthdrlen = 0;
 812                 mtu = inet->cork.fragsize;
 813         }
 814         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
 815
 816         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
 817         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 818
 819         if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
 820                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen);
 821                 return -EMSGSIZE;
 822         }
 823
 824         /*
 825          * transhdrlen > 0 means that this is the first fragment and we wish
 826          * it won't be fragmented in the future.
 827          */
 828         if (transhdrlen &&
 829             length + fragheaderlen <= mtu &&
 830             rt->u.dst.dev->features&(NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM) &&
 831             !exthdrlen)
 832                 csummode = CHECKSUM_HW;
 833
 834         inet->cork.length += length;
 835         if (((length > mtu) && (sk->sk_protocol == IPPROTO_UDP)) &&
 836                         (rt->u.dst.dev->features & NETIF_F_UFO)) {
 837
 838                 if(ip_ufo_append_data(sk, getfrag, from, length, hh_len,
 839                                fragheaderlen, transhdrlen, mtu, flags))
 840                         goto error;
 841
 842                 return 0;
 843         }
 844
 845         /* So, what's going on in the loop below?
 846          *
 847          * We use calculated fragment length to generate chained skb,
 848          * each of segments is IP fragment ready for sending to network after
 849          * adding appropriate IP header.
 850          */
 851
 852         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
 853                 goto alloc_new_skb;
 854
 855         while (length > 0) {
 856                 /* Check if the remaining data fits into current packet. */
 857                 copy = mtu - skb->len;
 858                 if (copy < length)
 859                         copy = maxfraglen - skb->len;
 860                 if (copy <= 0) {
 861                         char *data;
 862                         unsigned int datalen;
 863                         unsigned int fraglen;
 864                         unsigned int fraggap;
 865                         unsigned int alloclen;
 866                         struct sk_buff *skb_prev;
 867 alloc_new_skb:
 868                         skb_prev = skb;
 869                         if (skb_prev)
 870                                 fraggap = skb_prev->len - maxfraglen;
 871                         else
 872                                 fraggap = 0;
 873
 874                         /*
 875                          * If remaining data exceeds the mtu,
 876                          * we know we need more fragment(s).
 877                          */
 878                         datalen = length + fraggap;
 879                         if (datalen > mtu - fragheaderlen)
 880                                 datalen = maxfraglen - fragheaderlen;
 881                         fraglen = datalen + fragheaderlen;
 882
 883                         if ((flags & MSG_MORE) &&
 884                             !(rt->u.dst.dev->features&NETIF_F_SG))
 885                                 alloclen = mtu;
 886                         else
 887                                 alloclen = datalen + fragheaderlen;
 888
 889                         /* The last fragment gets additional space at tail.
 890                          * Note, with MSG_MORE we overallocate on fragments,
 891                          * because we have no idea what fragment will be
 892                          * the last.
 893                          */
 894                         if (datalen == length)
 895                                 alloclen += rt->u.dst.trailer_len;
 896
 897                         if (transhdrlen) {
 898                                 skb = sock_alloc_send_skb(sk,
 899                                                 alloclen + hh_len + 15,
 900                                                 (flags & MSG_DONTWAIT), &err);
 901                         } else {
 902                                 skb = NULL;
 903                                 if (atomic_read(&sk->sk_wmem_alloc) <=
 904                                     2 * sk->sk_sndbuf)
 905                                         skb = sock_wmalloc(sk,
 906                                                            alloclen + hh_len + 15, 1,
 907                                                            sk->sk_allocation);
 908                                 if (unlikely(skb == NULL))
 909                                         err = -ENOBUFS;
 910                         }
 911                         if (skb == NULL)
 912                                 goto error;
 913
 914                         /*
 915                          *      Fill in the control structures
 916                          */
 917                         skb->ip_summed = csummode;
 918                         skb->csum = 0;
 919                         skb_reserve(skb, hh_len);
 920
 921                         /*
 922                          *      Find where to start putting bytes.
 923                          */
 924                         data = skb_put(skb, fraglen);
 925                         skb->nh.raw = data + exthdrlen;
 926                         data += fragheaderlen;
 927                         skb->h.raw = data + exthdrlen;
 928
 929                         if (fraggap) {
 930                                 skb->csum = skb_copy_and_csum_bits(
 931                                         skb_prev, maxfraglen,
 932                                         data + transhdrlen, fraggap, 0);
 933                                 skb_prev->csum = csum_sub(skb_prev->csum,
 934                                                           skb->csum);
 935                                 data += fraggap;
 936                                 skb_trim(skb_prev, maxfraglen);
 937                         }
 938
 939                         copy = datalen - transhdrlen - fraggap;
 940                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
 941                                 err = -EFAULT;
 942                                 kfree_skb(skb);
 943                                 goto error;
 944                         }
 945
 946                         offset += copy;
 947                         length -= datalen - fraggap;
 948                         transhdrlen = 0;
 949                         exthdrlen = 0;
 950                         csummode = CHECKSUM_NONE;
 951
 952                         /*
 953                          * Put the packet on the pending queue.
 954                          */
 955                         __skb_queue_tail(&sk->sk_write_queue, skb);
 956                         continue;
 957                 }
 958
 959                 if (copy > length)
 960                         copy = length;
 961
 962                 if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
 963                         unsigned int off;
 964
 965                         off = skb->len;
 966                         if (getfrag(from, skb_put(skb, copy),
 967                                         offset, copy, off, skb) < 0) {
 968                                 __skb_trim(skb, off);
 969                                 err = -EFAULT;
 970                                 goto error;
 971                         }
 972                 } else {
 973                         int i = skb_shinfo(skb)->nr_frags;
 974                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
 975                         struct page *page = sk->sk_sndmsg_page;
 976                         int off = sk->sk_sndmsg_off;
 977                         unsigned int left;
 978
 979                         if (page && (left = PAGE_SIZE - off) > 0) {
 980                                 if (copy >= left)
 981                                         copy = left;
 982                                 if (page != frag->page) {
 983                                         if (i == MAX_SKB_FRAGS) {
 984                                                 err = -EMSGSIZE;
 985                                                 goto error;
 986                                         }
 987                                         get_page(page);
 988                                         skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);
 989                                         frag = &skb_shinfo(skb)->frags[i];
 990                                 }
 991                         } else if (i < MAX_SKB_FRAGS) {
 992                                 if (copy > PAGE_SIZE)
 993                                         copy = PAGE_SIZE;
 994                                 page = alloc_pages(sk->sk_allocation, 0);
 995                                 if (page == NULL)  {
 996                                         err = -ENOMEM;
 997                                         goto error;
 998                                 }
 999                                 sk->sk_sndmsg_page = page;
1000                                 sk->sk_sndmsg_off = 0;
1001
1002                                 skb_fill_page_desc(skb, i, page, 0, 0);
1003                                 frag = &skb_shinfo(skb)->frags[i];
1004                                 skb->truesize += PAGE_SIZE;
1005                                 atomic_add(PAGE_SIZE, &sk->sk_wmem_alloc);
1006                         } else {
1007                                 err = -EMSGSIZE;
1008                                 goto error;
1009                         }
1010                         if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) {
1011                                 err = -EFAULT;
1012                                 goto error;
1013                         }
1014                         sk->sk_sndmsg_off += copy;
1015                         frag->size += copy;
1016                         skb->len += copy;
1017                         skb->data_len += copy;
1018                 }
1019                 offset += copy;
1020                 length -= copy;
1021         }
1022
1023         return 0;
1024
1025 error:
1026         inet->cork.length -= length;
1027         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1028         return err;
1029 }
1030
1031 ssize_t ip_append_page(struct sock *sk, struct page *page,
1032                        int offset, size_t size, int flags)
1033 {
1034         struct inet_sock *inet = inet_sk(sk);
1035         struct sk_buff *skb;
1036         struct rtable *rt;
1037         struct ip_options *opt = NULL;
1038         int hh_len;
1039         int mtu;
1040         int len;
1041         int err;
1042         unsigned int maxfraglen, fragheaderlen, fraggap;
1043
1044         if (inet->hdrincl)
1045                 return -EPERM;
1046
1047         if (flags&MSG_PROBE)
1048                 return 0;
1049
1050         if (skb_queue_empty(&sk->sk_write_queue))
1051                 return -EINVAL;
1052
1053         rt = inet->cork.rt;
1054         if (inet->cork.flags & IPCORK_OPT)
1055                 opt = inet->cork.opt;
1056
1057         if (!(rt->u.dst.dev->features&NETIF_F_SG))
1058                 return -EOPNOTSUPP;
1059
1060         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
1061         mtu = inet->cork.fragsize;
1062
1063         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1064         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1065
1066         if (inet->cork.length + size > 0xFFFF - fragheaderlen) {
1067                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu);
1068                 return -EMSGSIZE;
1069         }
1070
1071         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1072                 return -EINVAL;
1073
1074         inet->cork.length += size;
1075         if ((sk->sk_protocol == IPPROTO_UDP) &&
1076             (rt->u.dst.dev->features & NETIF_F_UFO))
1077                 skb_shinfo(skb)->ufo_size = (mtu - fragheaderlen);
1078
1079
1080         while (size > 0) {
1081                 int i;
1082
1083                 if (skb_shinfo(skb)->ufo_size)
1084                         len = size;
1085                 else {
1086
1087                         /* Check if the remaining data fits into current packet. */
1088                         len = mtu - skb->len;
1089                         if (len < size)
1090                                 len = maxfraglen - skb->len;
1091                 }
1092                 if (len <= 0) {
1093                         struct sk_buff *skb_prev;
1094                         char *data;
1095                         struct iphdr *iph;
1096                         int alloclen;
1097
1098                         skb_prev = skb;
1099                         fraggap = skb_prev->len - maxfraglen;
1100
1101                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1102                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1103                         if (unlikely(!skb)) {
1104                                 err = -ENOBUFS;
1105                                 goto error;
1106                         }
1107
1108                         /*
1109                          *      Fill in the control structures
1110                          */
1111                         skb->ip_summed = CHECKSUM_NONE;
1112                         skb->csum = 0;
1113                         skb_reserve(skb, hh_len);
1114
1115                         /*
1116                          *      Find where to start putting bytes.
1117                          */
1118                         data = skb_put(skb, fragheaderlen + fraggap);
1119                         skb->nh.iph = iph = (struct iphdr *)data;
1120                         data += fragheaderlen;
1121                         skb->h.raw = data;
1122
1123                         if (fraggap) {
1124                                 skb->csum = skb_copy_and_csum_bits(
1125                                         skb_prev, maxfraglen,
1126                                         data, fraggap, 0);
1127                                 skb_prev->csum = csum_sub(skb_prev->csum,
1128                                                           skb->csum);
1129                                 skb_trim(skb_prev, maxfraglen);
1130                         }
1131
1132                         /*
1133                          * Put the packet on the pending queue.
1134                          */
1135                         __skb_queue_tail(&sk->sk_write_queue, skb);
1136                         continue;
1137                 }
1138
1139                 i = skb_shinfo(skb)->nr_frags;
1140                 if (len > size)
1141                         len = size;
1142                 if (skb_can_coalesce(skb, i, page, offset)) {
1143                         skb_shinfo(skb)->frags[i-1].size += len;
1144                 } else if (i < MAX_SKB_FRAGS) {
1145                         get_page(page);
1146                         skb_fill_page_desc(skb, i, page, offset, len);
1147                 } else {
1148                         err = -EMSGSIZE;
1149                         goto error;
1150                 }
1151
1152                 if (skb->ip_summed == CHECKSUM_NONE) {
1153                         unsigned int csum;
1154                         csum = csum_page(page, offset, len);
1155                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1156                 }
1157
1158                 skb->len += len;
1159                 skb->data_len += len;
1160                 offset += len;
1161                 size -= len;
1162         }
1163         return 0;
1164
1165 error:
1166         inet->cork.length -= size;
1167         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1168         return err;
1169 }
1170
1171 /*
1172  *      Combined all pending IP fragments on the socket as one IP datagram
1173  *      and push them out.
1174  */
1175 int ip_push_pending_frames(struct sock *sk)
1176 {
1177         struct sk_buff *skb, *tmp_skb;
1178         struct sk_buff **tail_skb;
1179         struct inet_sock *inet = inet_sk(sk);
1180         struct ip_options *opt = NULL;
1181         struct rtable *rt = inet->cork.rt;
1182         struct iphdr *iph;
1183         int df = 0;
1184         __u8 ttl;
1185         int err = 0;
1186
1187         if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
1188                 goto out;
1189         tail_skb = &(skb_shinfo(skb)->frag_list);
1190
1191         /* move skb->data to ip header from ext header */
1192         if (skb->data < skb->nh.raw)
1193                 __skb_pull(skb, skb->nh.raw - skb->data);
1194         while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
1195                 __skb_pull(tmp_skb, skb->h.raw - skb->nh.raw);
1196                 *tail_skb = tmp_skb;
1197                 tail_skb = &(tmp_skb->next);
1198                 skb->len += tmp_skb->len;
1199                 skb->data_len += tmp_skb->len;
1200                 skb->truesize += tmp_skb->truesize;
1201                 __sock_put(tmp_skb->sk);
1202                 tmp_skb->destructor = NULL;
1203                 tmp_skb->sk = NULL;
1204         }
1205
1206         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1207          * to fragment the frame generated here. No matter, what transforms
1208          * how transforms change size of the packet, it will come out.
1209          */
1210         if (inet->pmtudisc != IP_PMTUDISC_DO)
1211                 skb->local_df = 1;
1212
1213         /* DF bit is set when we want to see DF on outgoing frames.
1214          * If local_df is set too, we still allow to fragment this frame
1215          * locally. */
1216         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1217             (skb->len <= dst_mtu(&rt->u.dst) &&
1218              ip_dont_fragment(sk, &rt->u.dst)))
1219                 df = htons(IP_DF);
1220
1221         if (inet->cork.flags & IPCORK_OPT)
1222                 opt = inet->cork.opt;
1223
1224         if (rt->rt_type == RTN_MULTICAST)
1225                 ttl = inet->mc_ttl;
1226         else
1227                 ttl = ip_select_ttl(inet, &rt->u.dst);
1228
1229         iph = (struct iphdr *)skb->data;
1230         iph->version = 4;
1231         iph->ihl = 5;
1232         if (opt) {
1233                 iph->ihl += opt->optlen>>2;
1234                 ip_options_build(skb, opt, inet->cork.addr, rt, 0);
1235         }
1236         iph->tos = inet->tos;
1237         iph->tot_len = htons(skb->len);
1238         iph->frag_off = df;
1239         if (!df) {
1240                 __ip_select_ident(iph, &rt->u.dst, 0);
1241         } else {
1242                 iph->id = htons(inet->id++);
1243         }
1244         iph->ttl = ttl;
1245         iph->protocol = sk->sk_protocol;
1246         iph->saddr = rt->rt_src;
1247         iph->daddr = rt->rt_dst;
1248         ip_send_check(iph);
1249
1250         skb->priority = sk->sk_priority;
1251         skb->dst = dst_clone(&rt->u.dst);
1252
1253         /* Netfilter gets whole the not fragmented skb. */
1254         err = NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL,
1255                       skb->dst->dev, dst_output);
1256         if (err) {
1257                 if (err > 0)
1258                         err = inet->recverr ? net_xmit_errno(err) : 0;
1259                 if (err)
1260                         goto error;
1261         }
1262
1263 out:
1264         inet->cork.flags &= ~IPCORK_OPT;
1265         kfree(inet->cork.opt);
1266         inet->cork.opt = NULL;
1267         if (inet->cork.rt) {
1268                 ip_rt_put(inet->cork.rt);
1269                 inet->cork.rt = NULL;
1270         }
1271         return err;
1272
1273 error:
1274         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1275         goto out;
1276 }
1277
1278 /*
1279  *      Throw away all pending data on the socket.
1280  */
1281 void ip_flush_pending_frames(struct sock *sk)
1282 {
1283         struct inet_sock *inet = inet_sk(sk);
1284         struct sk_buff *skb;
1285
1286         while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
1287                 kfree_skb(skb);
1288
1289         inet->cork.flags &= ~IPCORK_OPT;
1290         kfree(inet->cork.opt);
1291         inet->cork.opt = NULL;
1292         if (inet->cork.rt) {
1293                 ip_rt_put(inet->cork.rt);
1294                 inet->cork.rt = NULL;
1295         }
1296 }
1297
1298
1299 /*
1300  *      Fetch data from kernel space and fill in checksum if needed.
1301  */
1302 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1303                               int len, int odd, struct sk_buff *skb)
1304 {
1305         unsigned int csum;
1306
1307         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1308         skb->csum = csum_block_add(skb->csum, csum, odd);
1309         return 0;
1310 }
1311
1312 /*
1313  *      Generic function to send a packet as reply to another packet.
1314  *      Used to send TCP resets so far. ICMP should use this function too.
1315  *
1316  *      Should run single threaded per socket because it uses the sock
1317  *      structure to pass arguments.
1318  *
1319  *      LATER: switch from ip_build_xmit to ip_append_*
1320  */
1321 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1322                    unsigned int len)
1323 {
1324         struct inet_sock *inet = inet_sk(sk);
1325         struct {
1326                 struct ip_options       opt;
1327                 char                    data[40];
1328         } replyopts;
1329         struct ipcm_cookie ipc;
1330         u32 daddr;
1331         struct rtable *rt = (struct rtable*)skb->dst;
1332
1333         if (ip_options_echo(&replyopts.opt, skb))
1334                 return;
1335
1336         daddr = ipc.addr = rt->rt_src;
1337         ipc.opt = NULL;
1338
1339         if (replyopts.opt.optlen) {
1340                 ipc.opt = &replyopts.opt;
1341
1342                 if (ipc.opt->srr)
1343                         daddr = replyopts.opt.faddr;
1344         }
1345
1346         {
1347                 struct flowi fl = { .nl_u = { .ip4_u =
1348                                               { .daddr = daddr,
1349                                                 .saddr = rt->rt_spec_dst,
1350                                                 .tos = RT_TOS(skb->nh.iph->tos) } },
1351                                     /* Not quite clean, but right. */
1352                                     .uli_u = { .ports =
1353                                                { .sport = skb->h.th->dest,
1354                                                  .dport = skb->h.th->source } },
1355                                     .proto = sk->sk_protocol };
1356                 if (ip_route_output_key(&rt, &fl))
1357                         return;
1358         }
1359
1360         /* And let IP do all the hard work.
1361
1362            This chunk is not reenterable, hence spinlock.
1363            Note that it uses the fact, that this function is called
1364            with locally disabled BH and that sk cannot be already spinlocked.
1365          */
1366         bh_lock_sock(sk);
1367         inet->tos = skb->nh.iph->tos;
1368         sk->sk_priority = skb->priority;
1369         sk->sk_protocol = skb->nh.iph->protocol;
1370         ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1371                        &ipc, rt, MSG_DONTWAIT);
1372         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1373                 if (arg->csumoffset >= 0)
1374                         *((u16 *)skb->h.raw + arg->csumoffset) = csum_fold(csum_add(skb->csum, arg->csum));
1375                 skb->ip_summed = CHECKSUM_NONE;
1376                 ip_push_pending_frames(sk);
1377         }
1378
1379         bh_unlock_sock(sk);
1380
1381         ip_rt_put(rt);
1382 }
1383
1384 void __init ip_init(void)
1385 {
1386         ip_rt_init();
1387         inet_initpeers();
1388
1389 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1390         igmp_mc_proc_init();
1391 #endif
1392 }
1393
1394 EXPORT_SYMBOL(ip_fragment);
1395 EXPORT_SYMBOL(ip_generic_getfrag);
1396 EXPORT_SYMBOL(ip_queue_xmit);
1397 EXPORT_SYMBOL(ip_send_check);