git.oblomov.eu Git - linux-2.6/blob - 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         struct net_device *dev = skb->dst->dev;
 206
 207         skb->dev = dev;
 208         skb->protocol = htons(ETH_P_IP);
 209
 210         return NF_HOOK(PF_INET, NF_IP_POST_ROUTING, skb, NULL, dev,
 211                        ip_finish_output2);
 212 }
 213
 214 int ip_mc_output(struct sk_buff *skb)
 215 {
 216         struct sock *sk = skb->sk;
 217         struct rtable *rt = (struct rtable*)skb->dst;
 218         struct net_device *dev = rt->u.dst.dev;
 219
 220         /*
 221          *      If the indicated interface is up and running, send the packet.
 222          */
 223         IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
 224
 225         skb->dev = dev;
 226         skb->protocol = htons(ETH_P_IP);
 227
 228         /*
 229          *      Multicasts are looped back for other local users
 230          */
 231
 232         if (rt->rt_flags&RTCF_MULTICAST) {
 233                 if ((!sk || inet_sk(sk)->mc_loop)
 234 #ifdef CONFIG_IP_MROUTE
 235                 /* Small optimization: do not loopback not local frames,
 236                    which returned after forwarding; they will be  dropped
 237                    by ip_mr_input in any case.
 238                    Note, that local frames are looped back to be delivered
 239                    to local recipients.
 240
 241                    This check is duplicated in ip_mr_input at the moment.
 242                  */
 243                     && ((rt->rt_flags&RTCF_LOCAL) || !(IPCB(skb)->flags&IPSKB_FORWARDED))
 244 #endif
 245                 ) {
 246                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 247                         if (newskb)
 248                                 NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL,
 249                                         newskb->dev,
 250                                         ip_dev_loopback_xmit);
 251                 }
 252
 253                 /* Multicasts with ttl 0 must not go beyond the host */
 254
 255                 if (skb->nh.iph->ttl == 0) {
 256                         kfree_skb(skb);
 257                         return 0;
 258                 }
 259         }
 260
 261         if (rt->rt_flags&RTCF_BROADCAST) {
 262                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 263                 if (newskb)
 264                         NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL,
 265                                 newskb->dev, ip_dev_loopback_xmit);
 266         }
 267
 268         if (skb->len > dst_mtu(&rt->u.dst))
 269                 return ip_fragment(skb, ip_finish_output);
 270         else
 271                 return ip_finish_output(skb);
 272 }
 273
 274 int ip_output(struct sk_buff *skb)
 275 {
 276         IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
 277
 278         if (skb->len > dst_mtu(skb->dst) &&
 279                 !(skb_shinfo(skb)->ufo_size || skb_shinfo(skb)->tso_size))
 280                 return ip_fragment(skb, ip_finish_output);
 281         else
 282                 return ip_finish_output(skb);
 283 }
 284
 285 int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
 286 {
 287         struct sock *sk = skb->sk;
 288         struct inet_sock *inet = inet_sk(sk);
 289         struct ip_options *opt = inet->opt;
 290         struct rtable *rt;
 291         struct iphdr *iph;
 292
 293         /* Skip all of this if the packet is already routed,
 294          * f.e. by something like SCTP.
 295          */
 296         rt = (struct rtable *) skb->dst;
 297         if (rt != NULL)
 298                 goto packet_routed;
 299
 300         /* Make sure we can route this packet. */
 301         rt = (struct rtable *)__sk_dst_check(sk, 0);
 302         if (rt == NULL) {
 303                 u32 daddr;
 304
 305                 /* Use correct destination address if we have options. */
 306                 daddr = inet->daddr;
 307                 if(opt && opt->srr)
 308                         daddr = opt->faddr;
 309
 310                 {
 311                         struct flowi fl = { .oif = sk->sk_bound_dev_if,
 312                                             .nl_u = { .ip4_u =
 313                                                       { .daddr = daddr,
 314                                                         .saddr = inet->saddr,
 315                                                         .tos = RT_CONN_FLAGS(sk) } },
 316                                             .proto = sk->sk_protocol,
 317                                             .uli_u = { .ports =
 318                                                        { .sport = inet->sport,
 319                                                          .dport = inet->dport } } };
 320
 321                         /* If this fails, retransmit mechanism of transport layer will
 322                          * keep trying until route appears or the connection times
 323                          * itself out.
 324                          */
 325                         if (ip_route_output_flow(&rt, &fl, sk, 0))
 326                                 goto no_route;
 327                 }
 328                 sk_setup_caps(sk, &rt->u.dst);
 329         }
 330         skb->dst = dst_clone(&rt->u.dst);
 331
 332 packet_routed:
 333         if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
 334                 goto no_route;
 335
 336         /* OK, we know where to send it, allocate and build IP header. */
 337         iph = (struct iphdr *) skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
 338         *((__u16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
 339         iph->tot_len = htons(skb->len);
 340         if (ip_dont_fragment(sk, &rt->u.dst) && !ipfragok)
 341                 iph->frag_off = htons(IP_DF);
 342         else
 343                 iph->frag_off = 0;
 344         iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
 345         iph->protocol = sk->sk_protocol;
 346         iph->saddr    = rt->rt_src;
 347         iph->daddr    = rt->rt_dst;
 348         skb->nh.iph   = iph;
 349         /* Transport layer set skb->h.foo itself. */
 350
 351         if (opt && opt->optlen) {
 352                 iph->ihl += opt->optlen >> 2;
 353                 ip_options_build(skb, opt, inet->daddr, rt, 0);
 354         }
 355
 356         ip_select_ident_more(iph, &rt->u.dst, sk, skb_shinfo(skb)->tso_segs);
 357
 358         /* Add an IP checksum. */
 359         ip_send_check(iph);
 360
 361         skb->priority = sk->sk_priority;
 362
 363         return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev,
 364                        dst_output);
 365
 366 no_route:
 367         IP_INC_STATS(IPSTATS_MIB_OUTNOROUTES);
 368         kfree_skb(skb);
 369         return -EHOSTUNREACH;
 370 }
 371
 372
 373 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 374 {
 375         to->pkt_type = from->pkt_type;
 376         to->priority = from->priority;
 377         to->protocol = from->protocol;
 378         dst_release(to->dst);
 379         to->dst = dst_clone(from->dst);
 380         to->dev = from->dev;
 381
 382         /* Copy the flags to each fragment. */
 383         IPCB(to)->flags = IPCB(from)->flags;
 384
 385 #ifdef CONFIG_NET_SCHED
 386         to->tc_index = from->tc_index;
 387 #endif
 388 #ifdef CONFIG_NETFILTER
 389         to->nfmark = from->nfmark;
 390         /* Connection association is same as pre-frag packet */
 391         nf_conntrack_put(to->nfct);
 392         to->nfct = from->nfct;
 393         nf_conntrack_get(to->nfct);
 394         to->nfctinfo = from->nfctinfo;
 395 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
 396         to->ipvs_property = from->ipvs_property;
 397 #endif
 398 #ifdef CONFIG_BRIDGE_NETFILTER
 399         nf_bridge_put(to->nf_bridge);
 400         to->nf_bridge = from->nf_bridge;
 401         nf_bridge_get(to->nf_bridge);
 402 #endif
 403 #endif
 404 }
 405
 406 /*
 407  *      This IP datagram is too large to be sent in one piece.  Break it up into
 408  *      smaller pieces (each of size equal to IP header plus
 409  *      a block of the data of the original IP data part) that will yet fit in a
 410  *      single device frame, and queue such a frame for sending.
 411  */
 412
 413 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 414 {
 415         struct iphdr *iph;
 416         int raw = 0;
 417         int ptr;
 418         struct net_device *dev;
 419         struct sk_buff *skb2;
 420         unsigned int mtu, hlen, left, len, ll_rs;
 421         int offset;
 422         int not_last_frag;
 423         struct rtable *rt = (struct rtable*)skb->dst;
 424         int err = 0;
 425
 426         dev = rt->u.dst.dev;
 427
 428         /*
 429          *      Point into the IP datagram header.
 430          */
 431
 432         iph = skb->nh.iph;
 433
 434         if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
 435                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 436                           htonl(dst_mtu(&rt->u.dst)));
 437                 kfree_skb(skb);
 438                 return -EMSGSIZE;
 439         }
 440
 441         /*
 442          *      Setup starting values.
 443          */
 444
 445         hlen = iph->ihl * 4;
 446         mtu = dst_mtu(&rt->u.dst) - hlen;       /* Size of data space */
 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 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         if (inet->cork.opt) {
1266                 kfree(inet->cork.opt);
1267                 inet->cork.opt = NULL;
1268         }
1269         if (inet->cork.rt) {
1270                 ip_rt_put(inet->cork.rt);
1271                 inet->cork.rt = NULL;
1272         }
1273         return err;
1274
1275 error:
1276         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1277         goto out;
1278 }
1279
1280 /*
1281  *      Throw away all pending data on the socket.
1282  */
1283 void ip_flush_pending_frames(struct sock *sk)
1284 {
1285         struct inet_sock *inet = inet_sk(sk);
1286         struct sk_buff *skb;
1287
1288         while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
1289                 kfree_skb(skb);
1290
1291         inet->cork.flags &= ~IPCORK_OPT;
1292         if (inet->cork.opt) {
1293                 kfree(inet->cork.opt);
1294                 inet->cork.opt = NULL;
1295         }
1296         if (inet->cork.rt) {
1297                 ip_rt_put(inet->cork.rt);
1298                 inet->cork.rt = NULL;
1299         }
1300 }
1301
1302
1303 /*
1304  *      Fetch data from kernel space and fill in checksum if needed.
1305  */
1306 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1307                               int len, int odd, struct sk_buff *skb)
1308 {
1309         unsigned int csum;
1310
1311         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1312         skb->csum = csum_block_add(skb->csum, csum, odd);
1313         return 0;
1314 }
1315
1316 /*
1317  *      Generic function to send a packet as reply to another packet.
1318  *      Used to send TCP resets so far. ICMP should use this function too.
1319  *
1320  *      Should run single threaded per socket because it uses the sock
1321  *      structure to pass arguments.
1322  *
1323  *      LATER: switch from ip_build_xmit to ip_append_*
1324  */
1325 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1326                    unsigned int len)
1327 {
1328         struct inet_sock *inet = inet_sk(sk);
1329         struct {
1330                 struct ip_options       opt;
1331                 char                    data[40];
1332         } replyopts;
1333         struct ipcm_cookie ipc;
1334         u32 daddr;
1335         struct rtable *rt = (struct rtable*)skb->dst;
1336
1337         if (ip_options_echo(&replyopts.opt, skb))
1338                 return;
1339
1340         daddr = ipc.addr = rt->rt_src;
1341         ipc.opt = NULL;
1342
1343         if (replyopts.opt.optlen) {
1344                 ipc.opt = &replyopts.opt;
1345
1346                 if (ipc.opt->srr)
1347                         daddr = replyopts.opt.faddr;
1348         }
1349
1350         {
1351                 struct flowi fl = { .nl_u = { .ip4_u =
1352                                               { .daddr = daddr,
1353                                                 .saddr = rt->rt_spec_dst,
1354                                                 .tos = RT_TOS(skb->nh.iph->tos) } },
1355                                     /* Not quite clean, but right. */
1356                                     .uli_u = { .ports =
1357                                                { .sport = skb->h.th->dest,
1358                                                  .dport = skb->h.th->source } },
1359                                     .proto = sk->sk_protocol };
1360                 if (ip_route_output_key(&rt, &fl))
1361                         return;
1362         }
1363
1364         /* And let IP do all the hard work.
1365
1366            This chunk is not reenterable, hence spinlock.
1367            Note that it uses the fact, that this function is called
1368            with locally disabled BH and that sk cannot be already spinlocked.
1369          */
1370         bh_lock_sock(sk);
1371         inet->tos = skb->nh.iph->tos;
1372         sk->sk_priority = skb->priority;
1373         sk->sk_protocol = skb->nh.iph->protocol;
1374         ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1375                        &ipc, rt, MSG_DONTWAIT);
1376         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1377                 if (arg->csumoffset >= 0)
1378                         *((u16 *)skb->h.raw + arg->csumoffset) = csum_fold(csum_add(skb->csum, arg->csum));
1379                 skb->ip_summed = CHECKSUM_NONE;
1380                 ip_push_pending_frames(sk);
1381         }
1382
1383         bh_unlock_sock(sk);
1384
1385         ip_rt_put(rt);
1386 }
1387
1388 void __init ip_init(void)
1389 {
1390         ip_rt_init();
1391         inet_initpeers();
1392
1393 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1394         igmp_mc_proc_init();
1395 #endif
1396 }
1397
1398 EXPORT_SYMBOL(ip_fragment);
1399 EXPORT_SYMBOL(ip_generic_getfrag);
1400 EXPORT_SYMBOL(ip_queue_xmit);
1401 EXPORT_SYMBOL(ip_send_check);