SAFE public projects git trees. - safe/jmp/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,
 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
 449         /* When frag_list is given, use it. First, check its validity:
 450          * some transformers could create wrong frag_list or break existing
 451          * one, it is not prohibited. In this case fall back to copying.
 452          *
 453          * LATER: this step can be merged to real generation of fragments,
 454          * we can switch to copy when see the first bad fragment.
 455          */
 456         if (skb_shinfo(skb)->frag_list) {
 457                 struct sk_buff *frag;
 458                 int first_len = skb_pagelen(skb);
 459
 460                 if (first_len - hlen > mtu ||
 461                     ((first_len - hlen) & 7) ||
 462                     (iph->frag_off & htons(IP_MF|IP_OFFSET)) ||
 463                     skb_cloned(skb))
 464                         goto slow_path;
 465
 466                 for (frag = skb_shinfo(skb)->frag_list; frag; frag = frag->next) {
 467                         /* Correct geometry. */
 468                         if (frag->len > mtu ||
 469                             ((frag->len & 7) && frag->next) ||
 470                             skb_headroom(frag) < hlen)
 471                             goto slow_path;
 472
 473                         /* Partially cloned skb? */
 474                         if (skb_shared(frag))
 475                                 goto slow_path;
 476
 477                         BUG_ON(frag->sk);
 478                         if (skb->sk) {
 479                                 sock_hold(skb->sk);
 480                                 frag->sk = skb->sk;
 481                                 frag->destructor = sock_wfree;
 482                                 skb->truesize -= frag->truesize;
 483                         }
 484                 }
 485
 486                 /* Everything is OK. Generate! */
 487
 488                 err = 0;
 489                 offset = 0;
 490                 frag = skb_shinfo(skb)->frag_list;
 491                 skb_shinfo(skb)->frag_list = NULL;
 492                 skb->data_len = first_len - skb_headlen(skb);
 493                 skb->len = first_len;
 494                 iph->tot_len = htons(first_len);
 495                 iph->frag_off = htons(IP_MF);
 496                 ip_send_check(iph);
 497
 498                 for (;;) {
 499                         /* Prepare header of the next frame,
 500                          * before previous one went down. */
 501                         if (frag) {
 502                                 frag->ip_summed = CHECKSUM_NONE;
 503                                 frag->h.raw = frag->data;
 504                                 frag->nh.raw = __skb_push(frag, hlen);
 505                                 memcpy(frag->nh.raw, iph, hlen);
 506                                 iph = frag->nh.iph;
 507                                 iph->tot_len = htons(frag->len);
 508                                 ip_copy_metadata(frag, skb);
 509                                 if (offset == 0)
 510                                         ip_options_fragment(frag);
 511                                 offset += skb->len - hlen;
 512                                 iph->frag_off = htons(offset>>3);
 513                                 if (frag->next != NULL)
 514                                         iph->frag_off |= htons(IP_MF);
 515                                 /* Ready, complete checksum */
 516                                 ip_send_check(iph);
 517                         }
 518
 519                         err = output(skb);
 520
 521                         if (err || !frag)
 522                                 break;
 523
 524                         skb = frag;
 525                         frag = skb->next;
 526                         skb->next = NULL;
 527                 }
 528
 529                 if (err == 0) {
 530                         IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
 531                         return 0;
 532                 }
 533
 534                 while (frag) {
 535                         skb = frag->next;
 536                         kfree_skb(frag);
 537                         frag = skb;
 538                 }
 539                 IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
 540                 return err;
 541         }
 542
 543 slow_path:
 544         left = skb->len - hlen;         /* Space per frame */
 545         ptr = raw + hlen;               /* Where to start from */
 546
 547 #ifdef CONFIG_BRIDGE_NETFILTER
 548         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
 549          * we need to make room for the encapsulating header */
 550         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, nf_bridge_pad(skb));
 551         mtu -= nf_bridge_pad(skb);
 552 #else
 553         ll_rs = LL_RESERVED_SPACE(rt->u.dst.dev);
 554 #endif
 555         /*
 556          *      Fragment the datagram.
 557          */
 558
 559         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
 560         not_last_frag = iph->frag_off & htons(IP_MF);
 561
 562         /*
 563          *      Keep copying data until we run out.
 564          */
 565
 566         while(left > 0) {
 567                 len = left;
 568                 /* IF: it doesn't fit, use 'mtu' - the data space left */
 569                 if (len > mtu)
 570                         len = mtu;
 571                 /* IF: we are not sending upto and including the packet end
 572                    then align the next start on an eight byte boundary */
 573                 if (len < left) {
 574                         len &= ~7;
 575                 }
 576                 /*
 577                  *      Allocate buffer.
 578                  */
 579
 580                 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
 581                         NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
 582                         err = -ENOMEM;
 583                         goto fail;
 584                 }
 585
 586                 /*
 587                  *      Set up data on packet
 588                  */
 589
 590                 ip_copy_metadata(skb2, skb);
 591                 skb_reserve(skb2, ll_rs);
 592                 skb_put(skb2, len + hlen);
 593                 skb2->nh.raw = skb2->data;
 594                 skb2->h.raw = skb2->data + hlen;
 595
 596                 /*
 597                  *      Charge the memory for the fragment to any owner
 598                  *      it might possess
 599                  */
 600
 601                 if (skb->sk)
 602                         skb_set_owner_w(skb2, skb->sk);
 603
 604                 /*
 605                  *      Copy the packet header into the new buffer.
 606                  */
 607
 608                 memcpy(skb2->nh.raw, skb->data, hlen);
 609
 610                 /*
 611                  *      Copy a block of the IP datagram.
 612                  */
 613                 if (skb_copy_bits(skb, ptr, skb2->h.raw, len))
 614                         BUG();
 615                 left -= len;
 616
 617                 /*
 618                  *      Fill in the new header fields.
 619                  */
 620                 iph = skb2->nh.iph;
 621                 iph->frag_off = htons((offset >> 3));
 622
 623                 /* ANK: dirty, but effective trick. Upgrade options only if
 624                  * the segment to be fragmented was THE FIRST (otherwise,
 625                  * options are already fixed) and make it ONCE
 626                  * on the initial skb, so that all the following fragments
 627                  * will inherit fixed options.
 628                  */
 629                 if (offset == 0)
 630                         ip_options_fragment(skb);
 631
 632                 /*
 633                  *      Added AC : If we are fragmenting a fragment that's not the
 634                  *                 last fragment then keep MF on each bit
 635                  */
 636                 if (left > 0 || not_last_frag)
 637                         iph->frag_off |= htons(IP_MF);
 638                 ptr += len;
 639                 offset += len;
 640
 641                 /*
 642                  *      Put this fragment into the sending queue.
 643                  */
 644
 645                 IP_INC_STATS(IPSTATS_MIB_FRAGCREATES);
 646
 647                 iph->tot_len = htons(len + hlen);
 648
 649                 ip_send_check(iph);
 650
 651                 err = output(skb2);
 652                 if (err)
 653                         goto fail;
 654         }
 655         kfree_skb(skb);
 656         IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
 657         return err;
 658
 659 fail:
 660         kfree_skb(skb);
 661         IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
 662         return err;
 663 }
 664
 665 int
 666 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
 667 {
 668         struct iovec *iov = from;
 669
 670         if (skb->ip_summed == CHECKSUM_HW) {
 671                 if (memcpy_fromiovecend(to, iov, offset, len) < 0)
 672                         return -EFAULT;
 673         } else {
 674                 unsigned int csum = 0;
 675                 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
 676                         return -EFAULT;
 677                 skb->csum = csum_block_add(skb->csum, csum, odd);
 678         }
 679         return 0;
 680 }
 681
 682 static inline unsigned int
 683 csum_page(struct page *page, int offset, int copy)
 684 {
 685         char *kaddr;
 686         unsigned int csum;
 687         kaddr = kmap(page);
 688         csum = csum_partial(kaddr + offset, copy, 0);
 689         kunmap(page);
 690         return csum;
 691 }
 692
 693 static inline int ip_ufo_append_data(struct sock *sk,
 694                         int getfrag(void *from, char *to, int offset, int len,
 695                                int odd, struct sk_buff *skb),
 696                         void *from, int length, int hh_len, int fragheaderlen,
 697                         int transhdrlen, int mtu,unsigned int flags)
 698 {
 699         struct sk_buff *skb;
 700         int err;
 701
 702         /* There is support for UDP fragmentation offload by network
 703          * device, so create one single skb packet containing complete
 704          * udp datagram
 705          */
 706         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
 707                 skb = sock_alloc_send_skb(sk,
 708                         hh_len + fragheaderlen + transhdrlen + 20,
 709                         (flags & MSG_DONTWAIT), &err);
 710
 711                 if (skb == NULL)
 712                         return err;
 713
 714                 /* reserve space for Hardware header */
 715                 skb_reserve(skb, hh_len);
 716
 717                 /* create space for UDP/IP header */
 718                 skb_put(skb,fragheaderlen + transhdrlen);
 719
 720                 /* initialize network header pointer */
 721                 skb->nh.raw = skb->data;
 722
 723                 /* initialize protocol header pointer */
 724                 skb->h.raw = skb->data + fragheaderlen;
 725
 726                 skb->ip_summed = CHECKSUM_HW;
 727                 skb->csum = 0;
 728                 sk->sk_sndmsg_off = 0;
 729         }
 730
 731         err = skb_append_datato_frags(sk,skb, getfrag, from,
 732                                (length - transhdrlen));
 733         if (!err) {
 734                 /* specify the length of each IP datagram fragment*/
 735                 skb_shinfo(skb)->ufo_size = (mtu - fragheaderlen);
 736                 __skb_queue_tail(&sk->sk_write_queue, skb);
 737
 738                 return 0;
 739         }
 740         /* There is not enough support do UFO ,
 741          * so follow normal path
 742          */
 743         kfree_skb(skb);
 744         return err;
 745 }
 746
 747 /*
 748  *      ip_append_data() and ip_append_page() can make one large IP datagram
 749  *      from many pieces of data. Each pieces will be holded on the socket
 750  *      until ip_push_pending_frames() is called. Each piece can be a page
 751  *      or non-page data.
 752  *
 753  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
 754  *      this interface potentially.
 755  *
 756  *      LATER: length must be adjusted by pad at tail, when it is required.
 757  */
 758 int ip_append_data(struct sock *sk,
 759                    int getfrag(void *from, char *to, int offset, int len,
 760                                int odd, struct sk_buff *skb),
 761                    void *from, int length, int transhdrlen,
 762                    struct ipcm_cookie *ipc, struct rtable *rt,
 763                    unsigned int flags)
 764 {
 765         struct inet_sock *inet = inet_sk(sk);
 766         struct sk_buff *skb;
 767
 768         struct ip_options *opt = NULL;
 769         int hh_len;
 770         int exthdrlen;
 771         int mtu;
 772         int copy;
 773         int err;
 774         int offset = 0;
 775         unsigned int maxfraglen, fragheaderlen;
 776         int csummode = CHECKSUM_NONE;
 777
 778         if (flags&MSG_PROBE)
 779                 return 0;
 780
 781         if (skb_queue_empty(&sk->sk_write_queue)) {
 782                 /*
 783                  * setup for corking.
 784                  */
 785                 opt = ipc->opt;
 786                 if (opt) {
 787                         if (inet->cork.opt == NULL) {
 788                                 inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation);
 789                                 if (unlikely(inet->cork.opt == NULL))
 790                                         return -ENOBUFS;
 791                         }
 792                         memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen);
 793                         inet->cork.flags |= IPCORK_OPT;
 794                         inet->cork.addr = ipc->addr;
 795                 }
 796                 dst_hold(&rt->u.dst);
 797                 inet->cork.fragsize = mtu = dst_mtu(rt->u.dst.path);
 798                 inet->cork.rt = rt;
 799                 inet->cork.length = 0;
 800                 sk->sk_sndmsg_page = NULL;
 801                 sk->sk_sndmsg_off = 0;
 802                 if ((exthdrlen = rt->u.dst.header_len) != 0) {
 803                         length += exthdrlen;
 804                         transhdrlen += exthdrlen;
 805                 }
 806         } else {
 807                 rt = inet->cork.rt;
 808                 if (inet->cork.flags & IPCORK_OPT)
 809                         opt = inet->cork.opt;
 810
 811                 transhdrlen = 0;
 812                 exthdrlen = 0;
 813                 mtu = inet->cork.fragsize;
 814         }
 815         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
 816
 817         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
 818         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 819
 820         if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
 821                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen);
 822                 return -EMSGSIZE;
 823         }
 824
 825         /*
 826          * transhdrlen > 0 means that this is the first fragment and we wish
 827          * it won't be fragmented in the future.
 828          */
 829         if (transhdrlen &&
 830             length + fragheaderlen <= mtu &&
 831             rt->u.dst.dev->features&(NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM) &&
 832             !exthdrlen)
 833                 csummode = CHECKSUM_HW;
 834
 835         inet->cork.length += length;
 836         if (((length > mtu) && (sk->sk_protocol == IPPROTO_UDP)) &&
 837                         (rt->u.dst.dev->features & NETIF_F_UFO)) {
 838
 839                 if(ip_ufo_append_data(sk, getfrag, from, length, hh_len,
 840                                fragheaderlen, transhdrlen, mtu, flags))
 841                         goto error;
 842
 843                 return 0;
 844         }
 845
 846         /* So, what's going on in the loop below?
 847          *
 848          * We use calculated fragment length to generate chained skb,
 849          * each of segments is IP fragment ready for sending to network after
 850          * adding appropriate IP header.
 851          */
 852
 853         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
 854                 goto alloc_new_skb;
 855
 856         while (length > 0) {
 857                 /* Check if the remaining data fits into current packet. */
 858                 copy = mtu - skb->len;
 859                 if (copy < length)
 860                         copy = maxfraglen - skb->len;
 861                 if (copy <= 0) {
 862                         char *data;
 863                         unsigned int datalen;
 864                         unsigned int fraglen;
 865                         unsigned int fraggap;
 866                         unsigned int alloclen;
 867                         struct sk_buff *skb_prev;
 868 alloc_new_skb:
 869                         skb_prev = skb;
 870                         if (skb_prev)
 871                                 fraggap = skb_prev->len - maxfraglen;
 872                         else
 873                                 fraggap = 0;
 874
 875                         /*
 876                          * If remaining data exceeds the mtu,
 877                          * we know we need more fragment(s).
 878                          */
 879                         datalen = length + fraggap;
 880                         if (datalen > mtu - fragheaderlen)
 881                                 datalen = maxfraglen - fragheaderlen;
 882                         fraglen = datalen + fragheaderlen;
 883
 884                         if ((flags & MSG_MORE) &&
 885                             !(rt->u.dst.dev->features&NETIF_F_SG))
 886                                 alloclen = mtu;
 887                         else
 888                                 alloclen = datalen + fragheaderlen;
 889
 890                         /* The last fragment gets additional space at tail.
 891                          * Note, with MSG_MORE we overallocate on fragments,
 892                          * because we have no idea what fragment will be
 893                          * the last.
 894                          */
 895                         if (datalen == length)
 896                                 alloclen += rt->u.dst.trailer_len;
 897
 898                         if (transhdrlen) {
 899                                 skb = sock_alloc_send_skb(sk,
 900                                                 alloclen + hh_len + 15,
 901                                                 (flags & MSG_DONTWAIT), &err);
 902                         } else {
 903                                 skb = NULL;
 904                                 if (atomic_read(&sk->sk_wmem_alloc) <=
 905                                     2 * sk->sk_sndbuf)
 906                                         skb = sock_wmalloc(sk,
 907                                                            alloclen + hh_len + 15, 1,
 908                                                            sk->sk_allocation);
 909                                 if (unlikely(skb == NULL))
 910                                         err = -ENOBUFS;
 911                         }
 912                         if (skb == NULL)
 913                                 goto error;
 914
 915                         /*
 916                          *      Fill in the control structures
 917                          */
 918                         skb->ip_summed = csummode;
 919                         skb->csum = 0;
 920                         skb_reserve(skb, hh_len);
 921
 922                         /*
 923                          *      Find where to start putting bytes.
 924                          */
 925                         data = skb_put(skb, fraglen);
 926                         skb->nh.raw = data + exthdrlen;
 927                         data += fragheaderlen;
 928                         skb->h.raw = data + exthdrlen;
 929
 930                         if (fraggap) {
 931                                 skb->csum = skb_copy_and_csum_bits(
 932                                         skb_prev, maxfraglen,
 933                                         data + transhdrlen, fraggap, 0);
 934                                 skb_prev->csum = csum_sub(skb_prev->csum,
 935                                                           skb->csum);
 936                                 data += fraggap;
 937                                 skb_trim(skb_prev, maxfraglen);
 938                         }
 939
 940                         copy = datalen - transhdrlen - fraggap;
 941                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
 942                                 err = -EFAULT;
 943                                 kfree_skb(skb);
 944                                 goto error;
 945                         }
 946
 947                         offset += copy;
 948                         length -= datalen - fraggap;
 949                         transhdrlen = 0;
 950                         exthdrlen = 0;
 951                         csummode = CHECKSUM_NONE;
 952
 953                         /*
 954                          * Put the packet on the pending queue.
 955                          */
 956                         __skb_queue_tail(&sk->sk_write_queue, skb);
 957                         continue;
 958                 }
 959
 960                 if (copy > length)
 961                         copy = length;
 962
 963                 if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
 964                         unsigned int off;
 965
 966                         off = skb->len;
 967                         if (getfrag(from, skb_put(skb, copy),
 968                                         offset, copy, off, skb) < 0) {
 969                                 __skb_trim(skb, off);
 970                                 err = -EFAULT;
 971                                 goto error;
 972                         }
 973                 } else {
 974                         int i = skb_shinfo(skb)->nr_frags;
 975                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
 976                         struct page *page = sk->sk_sndmsg_page;
 977                         int off = sk->sk_sndmsg_off;
 978                         unsigned int left;
 979
 980                         if (page && (left = PAGE_SIZE - off) > 0) {
 981                                 if (copy >= left)
 982                                         copy = left;
 983                                 if (page != frag->page) {
 984                                         if (i == MAX_SKB_FRAGS) {
 985                                                 err = -EMSGSIZE;
 986                                                 goto error;
 987                                         }
 988                                         get_page(page);
 989                                         skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);
 990                                         frag = &skb_shinfo(skb)->frags[i];
 991                                 }
 992                         } else if (i < MAX_SKB_FRAGS) {
 993                                 if (copy > PAGE_SIZE)
 994                                         copy = PAGE_SIZE;
 995                                 page = alloc_pages(sk->sk_allocation, 0);
 996                                 if (page == NULL)  {
 997                                         err = -ENOMEM;
 998                                         goto error;
 999                                 }
1000                                 sk->sk_sndmsg_page = page;
1001                                 sk->sk_sndmsg_off = 0;
1002
1003                                 skb_fill_page_desc(skb, i, page, 0, 0);
1004                                 frag = &skb_shinfo(skb)->frags[i];
1005                                 skb->truesize += PAGE_SIZE;
1006                                 atomic_add(PAGE_SIZE, &sk->sk_wmem_alloc);
1007                         } else {
1008                                 err = -EMSGSIZE;
1009                                 goto error;
1010                         }
1011                         if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) {
1012                                 err = -EFAULT;
1013                                 goto error;
1014                         }
1015                         sk->sk_sndmsg_off += copy;
1016                         frag->size += copy;
1017                         skb->len += copy;
1018                         skb->data_len += copy;
1019                 }
1020                 offset += copy;
1021                 length -= copy;
1022         }
1023
1024         return 0;
1025
1026 error:
1027         inet->cork.length -= length;
1028         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1029         return err;
1030 }
1031
1032 ssize_t ip_append_page(struct sock *sk, struct page *page,
1033                        int offset, size_t size, int flags)
1034 {
1035         struct inet_sock *inet = inet_sk(sk);
1036         struct sk_buff *skb;
1037         struct rtable *rt;
1038         struct ip_options *opt = NULL;
1039         int hh_len;
1040         int mtu;
1041         int len;
1042         int err;
1043         unsigned int maxfraglen, fragheaderlen, fraggap;
1044
1045         if (inet->hdrincl)
1046                 return -EPERM;
1047
1048         if (flags&MSG_PROBE)
1049                 return 0;
1050
1051         if (skb_queue_empty(&sk->sk_write_queue))
1052                 return -EINVAL;
1053
1054         rt = inet->cork.rt;
1055         if (inet->cork.flags & IPCORK_OPT)
1056                 opt = inet->cork.opt;
1057
1058         if (!(rt->u.dst.dev->features&NETIF_F_SG))
1059                 return -EOPNOTSUPP;
1060
1061         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
1062         mtu = inet->cork.fragsize;
1063
1064         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1065         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1066
1067         if (inet->cork.length + size > 0xFFFF - fragheaderlen) {
1068                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu);
1069                 return -EMSGSIZE;
1070         }
1071
1072         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1073                 return -EINVAL;
1074
1075         inet->cork.length += size;
1076         if ((sk->sk_protocol == IPPROTO_UDP) &&
1077             (rt->u.dst.dev->features & NETIF_F_UFO))
1078                 skb_shinfo(skb)->ufo_size = (mtu - fragheaderlen);
1079
1080
1081         while (size > 0) {
1082                 int i;
1083
1084                 if (skb_shinfo(skb)->ufo_size)
1085                         len = size;
1086                 else {
1087
1088                         /* Check if the remaining data fits into current packet. */
1089                         len = mtu - skb->len;
1090                         if (len < size)
1091                                 len = maxfraglen - skb->len;
1092                 }
1093                 if (len <= 0) {
1094                         struct sk_buff *skb_prev;
1095                         char *data;
1096                         struct iphdr *iph;
1097                         int alloclen;
1098
1099                         skb_prev = skb;
1100                         fraggap = skb_prev->len - maxfraglen;
1101
1102                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1103                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1104                         if (unlikely(!skb)) {
1105                                 err = -ENOBUFS;
1106                                 goto error;
1107                         }
1108
1109                         /*
1110                          *      Fill in the control structures
1111                          */
1112                         skb->ip_summed = CHECKSUM_NONE;
1113                         skb->csum = 0;
1114                         skb_reserve(skb, hh_len);
1115
1116                         /*
1117                          *      Find where to start putting bytes.
1118                          */
1119                         data = skb_put(skb, fragheaderlen + fraggap);
1120                         skb->nh.iph = iph = (struct iphdr *)data;
1121                         data += fragheaderlen;
1122                         skb->h.raw = data;
1123
1124                         if (fraggap) {
1125                                 skb->csum = skb_copy_and_csum_bits(
1126                                         skb_prev, maxfraglen,
1127                                         data, fraggap, 0);
1128                                 skb_prev->csum = csum_sub(skb_prev->csum,
1129                                                           skb->csum);
1130                                 skb_trim(skb_prev, maxfraglen);
1131                         }
1132
1133                         /*
1134                          * Put the packet on the pending queue.
1135                          */
1136                         __skb_queue_tail(&sk->sk_write_queue, skb);
1137                         continue;
1138                 }
1139
1140                 i = skb_shinfo(skb)->nr_frags;
1141                 if (len > size)
1142                         len = size;
1143                 if (skb_can_coalesce(skb, i, page, offset)) {
1144                         skb_shinfo(skb)->frags[i-1].size += len;
1145                 } else if (i < MAX_SKB_FRAGS) {
1146                         get_page(page);
1147                         skb_fill_page_desc(skb, i, page, offset, len);
1148                 } else {
1149                         err = -EMSGSIZE;
1150                         goto error;
1151                 }
1152
1153                 if (skb->ip_summed == CHECKSUM_NONE) {
1154                         unsigned int csum;
1155                         csum = csum_page(page, offset, len);
1156                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1157                 }
1158
1159                 skb->len += len;
1160                 skb->data_len += len;
1161                 offset += len;
1162                 size -= len;
1163         }
1164         return 0;
1165
1166 error:
1167         inet->cork.length -= size;
1168         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1169         return err;
1170 }
1171
1172 /*
1173  *      Combined all pending IP fragments on the socket as one IP datagram
1174  *      and push them out.
1175  */
1176 int ip_push_pending_frames(struct sock *sk)
1177 {
1178         struct sk_buff *skb, *tmp_skb;
1179         struct sk_buff **tail_skb;
1180         struct inet_sock *inet = inet_sk(sk);
1181         struct ip_options *opt = NULL;
1182         struct rtable *rt = inet->cork.rt;
1183         struct iphdr *iph;
1184         int df = 0;
1185         __u8 ttl;
1186         int err = 0;
1187
1188         if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
1189                 goto out;
1190         tail_skb = &(skb_shinfo(skb)->frag_list);
1191
1192         /* move skb->data to ip header from ext header */
1193         if (skb->data < skb->nh.raw)
1194                 __skb_pull(skb, skb->nh.raw - skb->data);
1195         while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
1196                 __skb_pull(tmp_skb, skb->h.raw - skb->nh.raw);
1197                 *tail_skb = tmp_skb;
1198                 tail_skb = &(tmp_skb->next);
1199                 skb->len += tmp_skb->len;
1200                 skb->data_len += tmp_skb->len;
1201                 skb->truesize += tmp_skb->truesize;
1202                 __sock_put(tmp_skb->sk);
1203                 tmp_skb->destructor = NULL;
1204                 tmp_skb->sk = NULL;
1205         }
1206
1207         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1208          * to fragment the frame generated here. No matter, what transforms
1209          * how transforms change size of the packet, it will come out.
1210          */
1211         if (inet->pmtudisc != IP_PMTUDISC_DO)
1212                 skb->local_df = 1;
1213
1214         /* DF bit is set when we want to see DF on outgoing frames.
1215          * If local_df is set too, we still allow to fragment this frame
1216          * locally. */
1217         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1218             (skb->len <= dst_mtu(&rt->u.dst) &&
1219              ip_dont_fragment(sk, &rt->u.dst)))
1220                 df = htons(IP_DF);
1221
1222         if (inet->cork.flags & IPCORK_OPT)
1223                 opt = inet->cork.opt;
1224
1225         if (rt->rt_type == RTN_MULTICAST)
1226                 ttl = inet->mc_ttl;
1227         else
1228                 ttl = ip_select_ttl(inet, &rt->u.dst);
1229
1230         iph = (struct iphdr *)skb->data;
1231         iph->version = 4;
1232         iph->ihl = 5;
1233         if (opt) {
1234                 iph->ihl += opt->optlen>>2;
1235                 ip_options_build(skb, opt, inet->cork.addr, rt, 0);
1236         }
1237         iph->tos = inet->tos;
1238         iph->tot_len = htons(skb->len);
1239         iph->frag_off = df;
1240         if (!df) {
1241                 __ip_select_ident(iph, &rt->u.dst, 0);
1242         } else {
1243                 iph->id = htons(inet->id++);
1244         }
1245         iph->ttl = ttl;
1246         iph->protocol = sk->sk_protocol;
1247         iph->saddr = rt->rt_src;
1248         iph->daddr = rt->rt_dst;
1249         ip_send_check(iph);
1250
1251         skb->priority = sk->sk_priority;
1252         skb->dst = dst_clone(&rt->u.dst);
1253
1254         /* Netfilter gets whole the not fragmented skb. */
1255         err = NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL,
1256                       skb->dst->dev, dst_output);
1257         if (err) {
1258                 if (err > 0)
1259                         err = inet->recverr ? net_xmit_errno(err) : 0;
1260                 if (err)
1261                         goto error;
1262         }
1263
1264 out:
1265         inet->cork.flags &= ~IPCORK_OPT;
1266         kfree(inet->cork.opt);
1267         inet->cork.opt = NULL;
1268         if (inet->cork.rt) {
1269                 ip_rt_put(inet->cork.rt);
1270                 inet->cork.rt = NULL;
1271         }
1272         return err;
1273
1274 error:
1275         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1276         goto out;
1277 }
1278
1279 /*
1280  *      Throw away all pending data on the socket.
1281  */
1282 void ip_flush_pending_frames(struct sock *sk)
1283 {
1284         struct inet_sock *inet = inet_sk(sk);
1285         struct sk_buff *skb;
1286
1287         while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
1288                 kfree_skb(skb);
1289
1290         inet->cork.flags &= ~IPCORK_OPT;
1291         kfree(inet->cork.opt);
1292         inet->cork.opt = NULL;
1293         if (inet->cork.rt) {
1294                 ip_rt_put(inet->cork.rt);
1295                 inet->cork.rt = NULL;
1296         }
1297 }
1298
1299
1300 /*
1301  *      Fetch data from kernel space and fill in checksum if needed.
1302  */
1303 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1304                               int len, int odd, struct sk_buff *skb)
1305 {
1306         unsigned int csum;
1307
1308         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1309         skb->csum = csum_block_add(skb->csum, csum, odd);
1310         return 0;
1311 }
1312
1313 /*
1314  *      Generic function to send a packet as reply to another packet.
1315  *      Used to send TCP resets so far. ICMP should use this function too.
1316  *
1317  *      Should run single threaded per socket because it uses the sock
1318  *      structure to pass arguments.
1319  *
1320  *      LATER: switch from ip_build_xmit to ip_append_*
1321  */
1322 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1323                    unsigned int len)
1324 {
1325         struct inet_sock *inet = inet_sk(sk);
1326         struct {
1327                 struct ip_options       opt;
1328                 char                    data[40];
1329         } replyopts;
1330         struct ipcm_cookie ipc;
1331         u32 daddr;
1332         struct rtable *rt = (struct rtable*)skb->dst;
1333
1334         if (ip_options_echo(&replyopts.opt, skb))
1335                 return;
1336
1337         daddr = ipc.addr = rt->rt_src;
1338         ipc.opt = NULL;
1339
1340         if (replyopts.opt.optlen) {
1341                 ipc.opt = &replyopts.opt;
1342
1343                 if (ipc.opt->srr)
1344                         daddr = replyopts.opt.faddr;
1345         }
1346
1347         {
1348                 struct flowi fl = { .nl_u = { .ip4_u =
1349                                               { .daddr = daddr,
1350                                                 .saddr = rt->rt_spec_dst,
1351                                                 .tos = RT_TOS(skb->nh.iph->tos) } },
1352                                     /* Not quite clean, but right. */
1353                                     .uli_u = { .ports =
1354                                                { .sport = skb->h.th->dest,
1355                                                  .dport = skb->h.th->source } },
1356                                     .proto = sk->sk_protocol };
1357                 if (ip_route_output_key(&rt, &fl))
1358                         return;
1359         }
1360
1361         /* And let IP do all the hard work.
1362
1363            This chunk is not reenterable, hence spinlock.
1364            Note that it uses the fact, that this function is called
1365            with locally disabled BH and that sk cannot be already spinlocked.
1366          */
1367         bh_lock_sock(sk);
1368         inet->tos = skb->nh.iph->tos;
1369         sk->sk_priority = skb->priority;
1370         sk->sk_protocol = skb->nh.iph->protocol;
1371         ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1372                        &ipc, rt, MSG_DONTWAIT);
1373         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1374                 if (arg->csumoffset >= 0)
1375                         *((u16 *)skb->h.raw + arg->csumoffset) = csum_fold(csum_add(skb->csum, arg->csum));
1376                 skb->ip_summed = CHECKSUM_NONE;
1377                 ip_push_pending_frames(sk);
1378         }
1379
1380         bh_unlock_sock(sk);
1381
1382         ip_rt_put(rt);
1383 }
1384
1385 void __init ip_init(void)
1386 {
1387         ip_rt_init();
1388         inet_initpeers();
1389
1390 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1391         igmp_mc_proc_init();
1392 #endif
1393 }
1394
1395 EXPORT_SYMBOL(ip_fragment);
1396 EXPORT_SYMBOL(ip_generic_getfrag);
1397 EXPORT_SYMBOL(ip_queue_xmit);
1398 EXPORT_SYMBOL(ip_send_check);