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,
 357                              (skb_shinfo(skb)->tso_segs ?: 1) - 1);
 358
 359         /* Add an IP checksum. */
 360         ip_send_check(iph);
 361
 362         skb->priority = sk->sk_priority;
 363
 364         return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev,
 365                        dst_output);
 366
 367 no_route:
 368         IP_INC_STATS(IPSTATS_MIB_OUTNOROUTES);
 369         kfree_skb(skb);
 370         return -EHOSTUNREACH;
 371 }
 372
 373
 374 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 375 {
 376         to->pkt_type = from->pkt_type;
 377         to->priority = from->priority;
 378         to->protocol = from->protocol;
 379         dst_release(to->dst);
 380         to->dst = dst_clone(from->dst);
 381         to->dev = from->dev;
 382
 383         /* Copy the flags to each fragment. */
 384         IPCB(to)->flags = IPCB(from)->flags;
 385
 386 #ifdef CONFIG_NET_SCHED
 387         to->tc_index = from->tc_index;
 388 #endif
 389 #ifdef CONFIG_NETFILTER
 390         to->nfmark = from->nfmark;
 391         /* Connection association is same as pre-frag packet */
 392         nf_conntrack_put(to->nfct);
 393         to->nfct = from->nfct;
 394         nf_conntrack_get(to->nfct);
 395         to->nfctinfo = from->nfctinfo;
 396 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
 397         to->ipvs_property = from->ipvs_property;
 398 #endif
 399 #ifdef CONFIG_BRIDGE_NETFILTER
 400         nf_bridge_put(to->nf_bridge);
 401         to->nf_bridge = from->nf_bridge;
 402         nf_bridge_get(to->nf_bridge);
 403 #endif
 404 #endif
 405 }
 406
 407 /*
 408  *      This IP datagram is too large to be sent in one piece.  Break it up into
 409  *      smaller pieces (each of size equal to IP header plus
 410  *      a block of the data of the original IP data part) that will yet fit in a
 411  *      single device frame, and queue such a frame for sending.
 412  */
 413
 414 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 415 {
 416         struct iphdr *iph;
 417         int raw = 0;
 418         int ptr;
 419         struct net_device *dev;
 420         struct sk_buff *skb2;
 421         unsigned int mtu, hlen, left, len, ll_rs;
 422         int offset;
 423         int not_last_frag;
 424         struct rtable *rt = (struct rtable*)skb->dst;
 425         int err = 0;
 426
 427         dev = rt->u.dst.dev;
 428
 429         /*
 430          *      Point into the IP datagram header.
 431          */
 432
 433         iph = skb->nh.iph;
 434
 435         if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
 436                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 437                           htonl(dst_mtu(&rt->u.dst)));
 438                 kfree_skb(skb);
 439                 return -EMSGSIZE;
 440         }
 441
 442         /*
 443          *      Setup starting values.
 444          */
 445
 446         hlen = iph->ihl * 4;
 447         mtu = dst_mtu(&rt->u.dst) - hlen;       /* Size of data space */
 448         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
 449
 450         /* When frag_list is given, use it. First, check its validity:
 451          * some transformers could create wrong frag_list or break existing
 452          * one, it is not prohibited. In this case fall back to copying.
 453          *
 454          * LATER: this step can be merged to real generation of fragments,
 455          * we can switch to copy when see the first bad fragment.
 456          */
 457         if (skb_shinfo(skb)->frag_list) {
 458                 struct sk_buff *frag;
 459                 int first_len = skb_pagelen(skb);
 460
 461                 if (first_len - hlen > mtu ||
 462                     ((first_len - hlen) & 7) ||
 463                     (iph->frag_off & htons(IP_MF|IP_OFFSET)) ||
 464                     skb_cloned(skb))
 465                         goto slow_path;
 466
 467                 for (frag = skb_shinfo(skb)->frag_list; frag; frag = frag->next) {
 468                         /* Correct geometry. */
 469                         if (frag->len > mtu ||
 470                             ((frag->len & 7) && frag->next) ||
 471                             skb_headroom(frag) < hlen)
 472                             goto slow_path;
 473
 474                         /* Partially cloned skb? */
 475                         if (skb_shared(frag))
 476                                 goto slow_path;
 477
 478                         BUG_ON(frag->sk);
 479                         if (skb->sk) {
 480                                 sock_hold(skb->sk);
 481                                 frag->sk = skb->sk;
 482                                 frag->destructor = sock_wfree;
 483                                 skb->truesize -= frag->truesize;
 484                         }
 485                 }
 486
 487                 /* Everything is OK. Generate! */
 488
 489                 err = 0;
 490                 offset = 0;
 491                 frag = skb_shinfo(skb)->frag_list;
 492                 skb_shinfo(skb)->frag_list = NULL;
 493                 skb->data_len = first_len - skb_headlen(skb);
 494                 skb->len = first_len;
 495                 iph->tot_len = htons(first_len);
 496                 iph->frag_off = htons(IP_MF);
 497                 ip_send_check(iph);
 498
 499                 for (;;) {
 500                         /* Prepare header of the next frame,
 501                          * before previous one went down. */
 502                         if (frag) {
 503                                 frag->ip_summed = CHECKSUM_NONE;
 504                                 frag->h.raw = frag->data;
 505                                 frag->nh.raw = __skb_push(frag, hlen);
 506                                 memcpy(frag->nh.raw, iph, hlen);
 507                                 iph = frag->nh.iph;
 508                                 iph->tot_len = htons(frag->len);
 509                                 ip_copy_metadata(frag, skb);
 510                                 if (offset == 0)
 511                                         ip_options_fragment(frag);
 512                                 offset += skb->len - hlen;
 513                                 iph->frag_off = htons(offset>>3);
 514                                 if (frag->next != NULL)
 515                                         iph->frag_off |= htons(IP_MF);
 516                                 /* Ready, complete checksum */
 517                                 ip_send_check(iph);
 518                         }
 519
 520                         err = output(skb);
 521
 522                         if (err || !frag)
 523                                 break;
 524
 525                         skb = frag;
 526                         frag = skb->next;
 527                         skb->next = NULL;
 528                 }
 529
 530                 if (err == 0) {
 531                         IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
 532                         return 0;
 533                 }
 534
 535                 while (frag) {
 536                         skb = frag->next;
 537                         kfree_skb(frag);
 538                         frag = skb;
 539                 }
 540                 IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
 541                 return err;
 542         }
 543
 544 slow_path:
 545         left = skb->len - hlen;         /* Space per frame */
 546         ptr = raw + hlen;               /* Where to start from */
 547
 548 #ifdef CONFIG_BRIDGE_NETFILTER
 549         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
 550          * we need to make room for the encapsulating header */
 551         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, nf_bridge_pad(skb));
 552         mtu -= nf_bridge_pad(skb);
 553 #else
 554         ll_rs = LL_RESERVED_SPACE(rt->u.dst.dev);
 555 #endif
 556         /*
 557          *      Fragment the datagram.
 558          */
 559
 560         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
 561         not_last_frag = iph->frag_off & htons(IP_MF);
 562
 563         /*
 564          *      Keep copying data until we run out.
 565          */
 566
 567         while(left > 0) {
 568                 len = left;
 569                 /* IF: it doesn't fit, use 'mtu' - the data space left */
 570                 if (len > mtu)
 571                         len = mtu;
 572                 /* IF: we are not sending upto and including the packet end
 573                    then align the next start on an eight byte boundary */
 574                 if (len < left) {
 575                         len &= ~7;
 576                 }
 577                 /*
 578                  *      Allocate buffer.
 579                  */
 580
 581                 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
 582                         NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
 583                         err = -ENOMEM;
 584                         goto fail;
 585                 }
 586
 587                 /*
 588                  *      Set up data on packet
 589                  */
 590
 591                 ip_copy_metadata(skb2, skb);
 592                 skb_reserve(skb2, ll_rs);
 593                 skb_put(skb2, len + hlen);
 594                 skb2->nh.raw = skb2->data;
 595                 skb2->h.raw = skb2->data + hlen;
 596
 597                 /*
 598                  *      Charge the memory for the fragment to any owner
 599                  *      it might possess
 600                  */
 601
 602                 if (skb->sk)
 603                         skb_set_owner_w(skb2, skb->sk);
 604
 605                 /*
 606                  *      Copy the packet header into the new buffer.
 607                  */
 608
 609                 memcpy(skb2->nh.raw, skb->data, hlen);
 610
 611                 /*
 612                  *      Copy a block of the IP datagram.
 613                  */
 614                 if (skb_copy_bits(skb, ptr, skb2->h.raw, len))
 615                         BUG();
 616                 left -= len;
 617
 618                 /*
 619                  *      Fill in the new header fields.
 620                  */
 621                 iph = skb2->nh.iph;
 622                 iph->frag_off = htons((offset >> 3));
 623
 624                 /* ANK: dirty, but effective trick. Upgrade options only if
 625                  * the segment to be fragmented was THE FIRST (otherwise,
 626                  * options are already fixed) and make it ONCE
 627                  * on the initial skb, so that all the following fragments
 628                  * will inherit fixed options.
 629                  */
 630                 if (offset == 0)
 631                         ip_options_fragment(skb);
 632
 633                 /*
 634                  *      Added AC : If we are fragmenting a fragment that's not the
 635                  *                 last fragment then keep MF on each bit
 636                  */
 637                 if (left > 0 || not_last_frag)
 638                         iph->frag_off |= htons(IP_MF);
 639                 ptr += len;
 640                 offset += len;
 641
 642                 /*
 643                  *      Put this fragment into the sending queue.
 644                  */
 645
 646                 IP_INC_STATS(IPSTATS_MIB_FRAGCREATES);
 647
 648                 iph->tot_len = htons(len + hlen);
 649
 650                 ip_send_check(iph);
 651
 652                 err = output(skb2);
 653                 if (err)
 654                         goto fail;
 655         }
 656         kfree_skb(skb);
 657         IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
 658         return err;
 659
 660 fail:
 661         kfree_skb(skb);
 662         IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
 663         return err;
 664 }
 665
 666 int
 667 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
 668 {
 669         struct iovec *iov = from;
 670
 671         if (skb->ip_summed == CHECKSUM_HW) {
 672                 if (memcpy_fromiovecend(to, iov, offset, len) < 0)
 673                         return -EFAULT;
 674         } else {
 675                 unsigned int csum = 0;
 676                 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
 677                         return -EFAULT;
 678                 skb->csum = csum_block_add(skb->csum, csum, odd);
 679         }
 680         return 0;
 681 }
 682
 683 static inline unsigned int
 684 csum_page(struct page *page, int offset, int copy)
 685 {
 686         char *kaddr;
 687         unsigned int csum;
 688         kaddr = kmap(page);
 689         csum = csum_partial(kaddr + offset, copy, 0);
 690         kunmap(page);
 691         return csum;
 692 }
 693
 694 static inline int ip_ufo_append_data(struct sock *sk,
 695                         int getfrag(void *from, char *to, int offset, int len,
 696                                int odd, struct sk_buff *skb),
 697                         void *from, int length, int hh_len, int fragheaderlen,
 698                         int transhdrlen, int mtu,unsigned int flags)
 699 {
 700         struct sk_buff *skb;
 701         int err;
 702
 703         /* There is support for UDP fragmentation offload by network
 704          * device, so create one single skb packet containing complete
 705          * udp datagram
 706          */
 707         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
 708                 skb = sock_alloc_send_skb(sk,
 709                         hh_len + fragheaderlen + transhdrlen + 20,
 710                         (flags & MSG_DONTWAIT), &err);
 711
 712                 if (skb == NULL)
 713                         return err;
 714
 715                 /* reserve space for Hardware header */
 716                 skb_reserve(skb, hh_len);
 717
 718                 /* create space for UDP/IP header */
 719                 skb_put(skb,fragheaderlen + transhdrlen);
 720
 721                 /* initialize network header pointer */
 722                 skb->nh.raw = skb->data;
 723
 724                 /* initialize protocol header pointer */
 725                 skb->h.raw = skb->data + fragheaderlen;
 726
 727                 skb->ip_summed = CHECKSUM_HW;
 728                 skb->csum = 0;
 729                 sk->sk_sndmsg_off = 0;
 730         }
 731
 732         err = skb_append_datato_frags(sk,skb, getfrag, from,
 733                                (length - transhdrlen));
 734         if (!err) {
 735                 /* specify the length of each IP datagram fragment*/
 736                 skb_shinfo(skb)->ufo_size = (mtu - fragheaderlen);
 737                 __skb_queue_tail(&sk->sk_write_queue, skb);
 738
 739                 return 0;
 740         }
 741         /* There is not enough support do UFO ,
 742          * so follow normal path
 743          */
 744         kfree_skb(skb);
 745         return err;
 746 }
 747
 748 /*
 749  *      ip_append_data() and ip_append_page() can make one large IP datagram
 750  *      from many pieces of data. Each pieces will be holded on the socket
 751  *      until ip_push_pending_frames() is called. Each piece can be a page
 752  *      or non-page data.
 753  *
 754  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
 755  *      this interface potentially.
 756  *
 757  *      LATER: length must be adjusted by pad at tail, when it is required.
 758  */
 759 int ip_append_data(struct sock *sk,
 760                    int getfrag(void *from, char *to, int offset, int len,
 761                                int odd, struct sk_buff *skb),
 762                    void *from, int length, int transhdrlen,
 763                    struct ipcm_cookie *ipc, struct rtable *rt,
 764                    unsigned int flags)
 765 {
 766         struct inet_sock *inet = inet_sk(sk);
 767         struct sk_buff *skb;
 768
 769         struct ip_options *opt = NULL;
 770         int hh_len;
 771         int exthdrlen;
 772         int mtu;
 773         int copy;
 774         int err;
 775         int offset = 0;
 776         unsigned int maxfraglen, fragheaderlen;
 777         int csummode = CHECKSUM_NONE;
 778
 779         if (flags&MSG_PROBE)
 780                 return 0;
 781
 782         if (skb_queue_empty(&sk->sk_write_queue)) {
 783                 /*
 784                  * setup for corking.
 785                  */
 786                 opt = ipc->opt;
 787                 if (opt) {
 788                         if (inet->cork.opt == NULL) {
 789                                 inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation);
 790                                 if (unlikely(inet->cork.opt == NULL))
 791                                         return -ENOBUFS;
 792                         }
 793                         memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen);
 794                         inet->cork.flags |= IPCORK_OPT;
 795                         inet->cork.addr = ipc->addr;
 796                 }
 797                 dst_hold(&rt->u.dst);
 798                 inet->cork.fragsize = mtu = dst_mtu(rt->u.dst.path);
 799                 inet->cork.rt = rt;
 800                 inet->cork.length = 0;
 801                 sk->sk_sndmsg_page = NULL;
 802                 sk->sk_sndmsg_off = 0;
 803                 if ((exthdrlen = rt->u.dst.header_len) != 0) {
 804                         length += exthdrlen;
 805                         transhdrlen += exthdrlen;
 806                 }
 807         } else {
 808                 rt = inet->cork.rt;
 809                 if (inet->cork.flags & IPCORK_OPT)
 810                         opt = inet->cork.opt;
 811
 812                 transhdrlen = 0;
 813                 exthdrlen = 0;
 814                 mtu = inet->cork.fragsize;
 815         }
 816         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
 817
 818         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
 819         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 820
 821         if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
 822                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen);
 823                 return -EMSGSIZE;
 824         }
 825
 826         /*
 827          * transhdrlen > 0 means that this is the first fragment and we wish
 828          * it won't be fragmented in the future.
 829          */
 830         if (transhdrlen &&
 831             length + fragheaderlen <= mtu &&
 832             rt->u.dst.dev->features&(NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM) &&
 833             !exthdrlen)
 834                 csummode = CHECKSUM_HW;
 835
 836         inet->cork.length += length;
 837         if (((length > mtu) && (sk->sk_protocol == IPPROTO_UDP)) &&
 838                         (rt->u.dst.dev->features & NETIF_F_UFO)) {
 839
 840                 if(ip_ufo_append_data(sk, getfrag, from, length, hh_len,
 841                                fragheaderlen, transhdrlen, mtu, flags))
 842                         goto error;
 843
 844                 return 0;
 845         }
 846
 847         /* So, what's going on in the loop below?
 848          *
 849          * We use calculated fragment length to generate chained skb,
 850          * each of segments is IP fragment ready for sending to network after
 851          * adding appropriate IP header.
 852          */
 853
 854         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
 855                 goto alloc_new_skb;
 856
 857         while (length > 0) {
 858                 /* Check if the remaining data fits into current packet. */
 859                 copy = mtu - skb->len;
 860                 if (copy < length)
 861                         copy = maxfraglen - skb->len;
 862                 if (copy <= 0) {
 863                         char *data;
 864                         unsigned int datalen;
 865                         unsigned int fraglen;
 866                         unsigned int fraggap;
 867                         unsigned int alloclen;
 868                         struct sk_buff *skb_prev;
 869 alloc_new_skb:
 870                         skb_prev = skb;
 871                         if (skb_prev)
 872                                 fraggap = skb_prev->len - maxfraglen;
 873                         else
 874                                 fraggap = 0;
 875
 876                         /*
 877                          * If remaining data exceeds the mtu,
 878                          * we know we need more fragment(s).
 879                          */
 880                         datalen = length + fraggap;
 881                         if (datalen > mtu - fragheaderlen)
 882                                 datalen = maxfraglen - fragheaderlen;
 883                         fraglen = datalen + fragheaderlen;
 884
 885                         if ((flags & MSG_MORE) &&
 886                             !(rt->u.dst.dev->features&NETIF_F_SG))
 887                                 alloclen = mtu;
 888                         else
 889                                 alloclen = datalen + fragheaderlen;
 890
 891                         /* The last fragment gets additional space at tail.
 892                          * Note, with MSG_MORE we overallocate on fragments,
 893                          * because we have no idea what fragment will be
 894                          * the last.
 895                          */
 896                         if (datalen == length)
 897                                 alloclen += rt->u.dst.trailer_len;
 898
 899                         if (transhdrlen) {
 900                                 skb = sock_alloc_send_skb(sk,
 901                                                 alloclen + hh_len + 15,
 902                                                 (flags & MSG_DONTWAIT), &err);
 903                         } else {
 904                                 skb = NULL;
 905                                 if (atomic_read(&sk->sk_wmem_alloc) <=
 906                                     2 * sk->sk_sndbuf)
 907                                         skb = sock_wmalloc(sk,
 908                                                            alloclen + hh_len + 15, 1,
 909                                                            sk->sk_allocation);
 910                                 if (unlikely(skb == NULL))
 911                                         err = -ENOBUFS;
 912                         }
 913                         if (skb == NULL)
 914                                 goto error;
 915
 916                         /*
 917                          *      Fill in the control structures
 918                          */
 919                         skb->ip_summed = csummode;
 920                         skb->csum = 0;
 921                         skb_reserve(skb, hh_len);
 922
 923                         /*
 924                          *      Find where to start putting bytes.
 925                          */
 926                         data = skb_put(skb, fraglen);
 927                         skb->nh.raw = data + exthdrlen;
 928                         data += fragheaderlen;
 929                         skb->h.raw = data + exthdrlen;
 930
 931                         if (fraggap) {
 932                                 skb->csum = skb_copy_and_csum_bits(
 933                                         skb_prev, maxfraglen,
 934                                         data + transhdrlen, fraggap, 0);
 935                                 skb_prev->csum = csum_sub(skb_prev->csum,
 936                                                           skb->csum);
 937                                 data += fraggap;
 938                                 skb_trim(skb_prev, maxfraglen);
 939                         }
 940
 941                         copy = datalen - transhdrlen - fraggap;
 942                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
 943                                 err = -EFAULT;
 944                                 kfree_skb(skb);
 945                                 goto error;
 946                         }
 947
 948                         offset += copy;
 949                         length -= datalen - fraggap;
 950                         transhdrlen = 0;
 951                         exthdrlen = 0;
 952                         csummode = CHECKSUM_NONE;
 953
 954                         /*
 955                          * Put the packet on the pending queue.
 956                          */
 957                         __skb_queue_tail(&sk->sk_write_queue, skb);
 958                         continue;
 959                 }
 960
 961                 if (copy > length)
 962                         copy = length;
 963
 964                 if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
 965                         unsigned int off;
 966
 967                         off = skb->len;
 968                         if (getfrag(from, skb_put(skb, copy),
 969                                         offset, copy, off, skb) < 0) {
 970                                 __skb_trim(skb, off);
 971                                 err = -EFAULT;
 972                                 goto error;
 973                         }
 974                 } else {
 975                         int i = skb_shinfo(skb)->nr_frags;
 976                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
 977                         struct page *page = sk->sk_sndmsg_page;
 978                         int off = sk->sk_sndmsg_off;
 979                         unsigned int left;
 980
 981                         if (page && (left = PAGE_SIZE - off) > 0) {
 982                                 if (copy >= left)
 983                                         copy = left;
 984                                 if (page != frag->page) {
 985                                         if (i == MAX_SKB_FRAGS) {
 986                                                 err = -EMSGSIZE;
 987                                                 goto error;
 988                                         }
 989                                         get_page(page);
 990                                         skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);
 991                                         frag = &skb_shinfo(skb)->frags[i];
 992                                 }
 993                         } else if (i < MAX_SKB_FRAGS) {
 994                                 if (copy > PAGE_SIZE)
 995                                         copy = PAGE_SIZE;
 996                                 page = alloc_pages(sk->sk_allocation, 0);
 997                                 if (page == NULL)  {
 998                                         err = -ENOMEM;
 999                                         goto error;
1000                                 }
1001                                 sk->sk_sndmsg_page = page;
1002                                 sk->sk_sndmsg_off = 0;
1003
1004                                 skb_fill_page_desc(skb, i, page, 0, 0);
1005                                 frag = &skb_shinfo(skb)->frags[i];
1006                                 skb->truesize += PAGE_SIZE;
1007                                 atomic_add(PAGE_SIZE, &sk->sk_wmem_alloc);
1008                         } else {
1009                                 err = -EMSGSIZE;
1010                                 goto error;
1011                         }
1012                         if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) {
1013                                 err = -EFAULT;
1014                                 goto error;
1015                         }
1016                         sk->sk_sndmsg_off += copy;
1017                         frag->size += copy;
1018                         skb->len += copy;
1019                         skb->data_len += copy;
1020                 }
1021                 offset += copy;
1022                 length -= copy;
1023         }
1024
1025         return 0;
1026
1027 error:
1028         inet->cork.length -= length;
1029         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1030         return err;
1031 }
1032
1033 ssize_t ip_append_page(struct sock *sk, struct page *page,
1034                        int offset, size_t size, int flags)
1035 {
1036         struct inet_sock *inet = inet_sk(sk);
1037         struct sk_buff *skb;
1038         struct rtable *rt;
1039         struct ip_options *opt = NULL;
1040         int hh_len;
1041         int mtu;
1042         int len;
1043         int err;
1044         unsigned int maxfraglen, fragheaderlen, fraggap;
1045
1046         if (inet->hdrincl)
1047                 return -EPERM;
1048
1049         if (flags&MSG_PROBE)
1050                 return 0;
1051
1052         if (skb_queue_empty(&sk->sk_write_queue))
1053                 return -EINVAL;
1054
1055         rt = inet->cork.rt;
1056         if (inet->cork.flags & IPCORK_OPT)
1057                 opt = inet->cork.opt;
1058
1059         if (!(rt->u.dst.dev->features&NETIF_F_SG))
1060                 return -EOPNOTSUPP;
1061
1062         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
1063         mtu = inet->cork.fragsize;
1064
1065         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1066         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1067
1068         if (inet->cork.length + size > 0xFFFF - fragheaderlen) {
1069                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu);
1070                 return -EMSGSIZE;
1071         }
1072
1073         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1074                 return -EINVAL;
1075
1076         inet->cork.length += size;
1077         if ((sk->sk_protocol == IPPROTO_UDP) &&
1078             (rt->u.dst.dev->features & NETIF_F_UFO))
1079                 skb_shinfo(skb)->ufo_size = (mtu - fragheaderlen);
1080
1081
1082         while (size > 0) {
1083                 int i;
1084
1085                 if (skb_shinfo(skb)->ufo_size)
1086                         len = size;
1087                 else {
1088
1089                         /* Check if the remaining data fits into current packet. */
1090                         len = mtu - skb->len;
1091                         if (len < size)
1092                                 len = maxfraglen - skb->len;
1093                 }
1094                 if (len <= 0) {
1095                         struct sk_buff *skb_prev;
1096                         char *data;
1097                         struct iphdr *iph;
1098                         int alloclen;
1099
1100                         skb_prev = skb;
1101                         fraggap = skb_prev->len - maxfraglen;
1102
1103                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1104                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1105                         if (unlikely(!skb)) {
1106                                 err = -ENOBUFS;
1107                                 goto error;
1108                         }
1109
1110                         /*
1111                          *      Fill in the control structures
1112                          */
1113                         skb->ip_summed = CHECKSUM_NONE;
1114                         skb->csum = 0;
1115                         skb_reserve(skb, hh_len);
1116
1117                         /*
1118                          *      Find where to start putting bytes.
1119                          */
1120                         data = skb_put(skb, fragheaderlen + fraggap);
1121                         skb->nh.iph = iph = (struct iphdr *)data;
1122                         data += fragheaderlen;
1123                         skb->h.raw = data;
1124
1125                         if (fraggap) {
1126                                 skb->csum = skb_copy_and_csum_bits(
1127                                         skb_prev, maxfraglen,
1128                                         data, fraggap, 0);
1129                                 skb_prev->csum = csum_sub(skb_prev->csum,
1130                                                           skb->csum);
1131                                 skb_trim(skb_prev, maxfraglen);
1132                         }
1133
1134                         /*
1135                          * Put the packet on the pending queue.
1136                          */
1137                         __skb_queue_tail(&sk->sk_write_queue, skb);
1138                         continue;
1139                 }
1140
1141                 i = skb_shinfo(skb)->nr_frags;
1142                 if (len > size)
1143                         len = size;
1144                 if (skb_can_coalesce(skb, i, page, offset)) {
1145                         skb_shinfo(skb)->frags[i-1].size += len;
1146                 } else if (i < MAX_SKB_FRAGS) {
1147                         get_page(page);
1148                         skb_fill_page_desc(skb, i, page, offset, len);
1149                 } else {
1150                         err = -EMSGSIZE;
1151                         goto error;
1152                 }
1153
1154                 if (skb->ip_summed == CHECKSUM_NONE) {
1155                         unsigned int csum;
1156                         csum = csum_page(page, offset, len);
1157                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1158                 }
1159
1160                 skb->len += len;
1161                 skb->data_len += len;
1162                 offset += len;
1163                 size -= len;
1164         }
1165         return 0;
1166
1167 error:
1168         inet->cork.length -= size;
1169         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1170         return err;
1171 }
1172
1173 /*
1174  *      Combined all pending IP fragments on the socket as one IP datagram
1175  *      and push them out.
1176  */
1177 int ip_push_pending_frames(struct sock *sk)
1178 {
1179         struct sk_buff *skb, *tmp_skb;
1180         struct sk_buff **tail_skb;
1181         struct inet_sock *inet = inet_sk(sk);
1182         struct ip_options *opt = NULL;
1183         struct rtable *rt = inet->cork.rt;
1184         struct iphdr *iph;
1185         int df = 0;
1186         __u8 ttl;
1187         int err = 0;
1188
1189         if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
1190                 goto out;
1191         tail_skb = &(skb_shinfo(skb)->frag_list);
1192
1193         /* move skb->data to ip header from ext header */
1194         if (skb->data < skb->nh.raw)
1195                 __skb_pull(skb, skb->nh.raw - skb->data);
1196         while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
1197                 __skb_pull(tmp_skb, skb->h.raw - skb->nh.raw);
1198                 *tail_skb = tmp_skb;
1199                 tail_skb = &(tmp_skb->next);
1200                 skb->len += tmp_skb->len;
1201                 skb->data_len += tmp_skb->len;
1202                 skb->truesize += tmp_skb->truesize;
1203                 __sock_put(tmp_skb->sk);
1204                 tmp_skb->destructor = NULL;
1205                 tmp_skb->sk = NULL;
1206         }
1207
1208         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1209          * to fragment the frame generated here. No matter, what transforms
1210          * how transforms change size of the packet, it will come out.
1211          */
1212         if (inet->pmtudisc != IP_PMTUDISC_DO)
1213                 skb->local_df = 1;
1214
1215         /* DF bit is set when we want to see DF on outgoing frames.
1216          * If local_df is set too, we still allow to fragment this frame
1217          * locally. */
1218         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1219             (skb->len <= dst_mtu(&rt->u.dst) &&
1220              ip_dont_fragment(sk, &rt->u.dst)))
1221                 df = htons(IP_DF);
1222
1223         if (inet->cork.flags & IPCORK_OPT)
1224                 opt = inet->cork.opt;
1225
1226         if (rt->rt_type == RTN_MULTICAST)
1227                 ttl = inet->mc_ttl;
1228         else
1229                 ttl = ip_select_ttl(inet, &rt->u.dst);
1230
1231         iph = (struct iphdr *)skb->data;
1232         iph->version = 4;
1233         iph->ihl = 5;
1234         if (opt) {
1235                 iph->ihl += opt->optlen>>2;
1236                 ip_options_build(skb, opt, inet->cork.addr, rt, 0);
1237         }
1238         iph->tos = inet->tos;
1239         iph->tot_len = htons(skb->len);
1240         iph->frag_off = df;
1241         if (!df) {
1242                 __ip_select_ident(iph, &rt->u.dst, 0);
1243         } else {
1244                 iph->id = htons(inet->id++);
1245         }
1246         iph->ttl = ttl;
1247         iph->protocol = sk->sk_protocol;
1248         iph->saddr = rt->rt_src;
1249         iph->daddr = rt->rt_dst;
1250         ip_send_check(iph);
1251
1252         skb->priority = sk->sk_priority;
1253         skb->dst = dst_clone(&rt->u.dst);
1254
1255         /* Netfilter gets whole the not fragmented skb. */
1256         err = NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL,
1257                       skb->dst->dev, dst_output);
1258         if (err) {
1259                 if (err > 0)
1260                         err = inet->recverr ? net_xmit_errno(err) : 0;
1261                 if (err)
1262                         goto error;
1263         }
1264
1265 out:
1266         inet->cork.flags &= ~IPCORK_OPT;
1267         kfree(inet->cork.opt);
1268         inet->cork.opt = NULL;
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         kfree(inet->cork.opt);
1293         inet->cork.opt = NULL;
1294         if (inet->cork.rt) {
1295                 ip_rt_put(inet->cork.rt);
1296                 inet->cork.rt = NULL;
1297         }
1298 }
1299
1300
1301 /*
1302  *      Fetch data from kernel space and fill in checksum if needed.
1303  */
1304 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1305                               int len, int odd, struct sk_buff *skb)
1306 {
1307         unsigned int csum;
1308
1309         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1310         skb->csum = csum_block_add(skb->csum, csum, odd);
1311         return 0;
1312 }
1313
1314 /*
1315  *      Generic function to send a packet as reply to another packet.
1316  *      Used to send TCP resets so far. ICMP should use this function too.
1317  *
1318  *      Should run single threaded per socket because it uses the sock
1319  *      structure to pass arguments.
1320  *
1321  *      LATER: switch from ip_build_xmit to ip_append_*
1322  */
1323 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1324                    unsigned int len)
1325 {
1326         struct inet_sock *inet = inet_sk(sk);
1327         struct {
1328                 struct ip_options       opt;
1329                 char                    data[40];
1330         } replyopts;
1331         struct ipcm_cookie ipc;
1332         u32 daddr;
1333         struct rtable *rt = (struct rtable*)skb->dst;
1334
1335         if (ip_options_echo(&replyopts.opt, skb))
1336                 return;
1337
1338         daddr = ipc.addr = rt->rt_src;
1339         ipc.opt = NULL;
1340
1341         if (replyopts.opt.optlen) {
1342                 ipc.opt = &replyopts.opt;
1343
1344                 if (ipc.opt->srr)
1345                         daddr = replyopts.opt.faddr;
1346         }
1347
1348         {
1349                 struct flowi fl = { .nl_u = { .ip4_u =
1350                                               { .daddr = daddr,
1351                                                 .saddr = rt->rt_spec_dst,
1352                                                 .tos = RT_TOS(skb->nh.iph->tos) } },
1353                                     /* Not quite clean, but right. */
1354                                     .uli_u = { .ports =
1355                                                { .sport = skb->h.th->dest,
1356                                                  .dport = skb->h.th->source } },
1357                                     .proto = sk->sk_protocol };
1358                 if (ip_route_output_key(&rt, &fl))
1359                         return;
1360         }
1361
1362         /* And let IP do all the hard work.
1363
1364            This chunk is not reenterable, hence spinlock.
1365            Note that it uses the fact, that this function is called
1366            with locally disabled BH and that sk cannot be already spinlocked.
1367          */
1368         bh_lock_sock(sk);
1369         inet->tos = skb->nh.iph->tos;
1370         sk->sk_priority = skb->priority;
1371         sk->sk_protocol = skb->nh.iph->protocol;
1372         ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1373                        &ipc, rt, MSG_DONTWAIT);
1374         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1375                 if (arg->csumoffset >= 0)
1376                         *((u16 *)skb->h.raw + arg->csumoffset) = csum_fold(csum_add(skb->csum, arg->csum));
1377                 skb->ip_summed = CHECKSUM_NONE;
1378                 ip_push_pending_frames(sk);
1379         }
1380
1381         bh_unlock_sock(sk);
1382
1383         ip_rt_put(rt);
1384 }
1385
1386 void __init ip_init(void)
1387 {
1388         ip_rt_init();
1389         inet_initpeers();
1390
1391 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1392         igmp_mc_proc_init();
1393 #endif
1394 }
1395
1396 EXPORT_SYMBOL(ip_fragment);
1397 EXPORT_SYMBOL(ip_generic_getfrag);
1398 EXPORT_SYMBOL(ip_queue_xmit);
1399 EXPORT_SYMBOL(ip_send_check);