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 <net/tcp.h> 73 #include <net/udp.h> 74 #include <linux/skbuff.h> 75 #include <net/sock.h> 76 #include <net/arp.h> 77 #include <net/icmp.h> 78 #include <net/raw.h> 79 #include <net/checksum.h> 80 #include <net/inetpeer.h> 81 #include <net/checksum.h> 82 #include <linux/igmp.h> 83 #include <linux/netfilter_ipv4.h> 84 #include <linux/netfilter_bridge.h> 85 #include <linux/mroute.h> 86 #include <linux/netlink.h> 87 88 /* 89 * Shall we try to damage output packets if routing dev changes? 90 */ 91 92 int sysctl_ip_dynaddr; 93 int sysctl_ip_default_ttl = IPDEFTTL; 94 95 /* Generate a checksum for an outgoing IP datagram. */ 96 __inline__ void ip_send_check(struct iphdr *iph) 97 { 98 iph->check = 0; 99 iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl); 100 } 101 102 /* dev_loopback_xmit for use with netfilter. */ 103 static int ip_dev_loopback_xmit(struct sk_buff *newskb) 104 { 105 newskb->mac.raw = newskb->data; 106 __skb_pull(newskb, newskb->nh.raw - newskb->data); 107 newskb->pkt_type = PACKET_LOOPBACK; 108 newskb->ip_summed = CHECKSUM_UNNECESSARY; 109 BUG_TRAP(newskb->dst); 110 nf_reset(newskb); 111 netif_rx(newskb); 112 return 0; 113 } 114 115 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst) 116 { 117 int ttl = inet->uc_ttl; 118 119 if (ttl < 0) 120 ttl = dst_metric(dst, RTAX_HOPLIMIT); 121 return ttl; 122 } 123 124 /* 125 * Add an ip header to a skbuff and send it out. 126 * 127 */ 128 int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk, 129 u32 saddr, u32 daddr, struct ip_options *opt) 130 { 131 struct inet_sock *inet = inet_sk(sk); 132 struct rtable *rt = (struct rtable *)skb->dst; 133 struct iphdr *iph; 134 135 /* Build the IP header. */ 136 if (opt) 137 iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr) + opt->optlen); 138 else 139 iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr)); 140 141 iph->version = 4; 142 iph->ihl = 5; 143 iph->tos = inet->tos; 144 if (ip_dont_fragment(sk, &rt->u.dst)) 145 iph->frag_off = htons(IP_DF); 146 else 147 iph->frag_off = 0; 148 iph->ttl = ip_select_ttl(inet, &rt->u.dst); 149 iph->daddr = rt->rt_dst; 150 iph->saddr = rt->rt_src; 151 iph->protocol = sk->sk_protocol; 152 iph->tot_len = htons(skb->len); 153 ip_select_ident(iph, &rt->u.dst, sk); 154 skb->nh.iph = iph; 155 156 if (opt && opt->optlen) { 157 iph->ihl += opt->optlen>>2; 158 ip_options_build(skb, opt, daddr, rt, 0); 159 } 160 ip_send_check(iph); 161 162 skb->priority = sk->sk_priority; 163 164 /* Send it out. */ 165 return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev, 166 dst_output); 167 } 168 169 static inline int ip_finish_output2(struct sk_buff *skb) 170 { 171 struct dst_entry *dst = skb->dst; 172 struct hh_cache *hh = dst->hh; 173 struct net_device *dev = dst->dev; 174 int hh_len = LL_RESERVED_SPACE(dev); 175 176 /* Be paranoid, rather than too clever. */ 177 if (unlikely(skb_headroom(skb) < hh_len && dev->hard_header)) { 178 struct sk_buff *skb2; 179 180 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev)); 181 if (skb2 == NULL) { 182 kfree_skb(skb); 183 return -ENOMEM; 184 } 185 if (skb->sk) 186 skb_set_owner_w(skb2, skb->sk); 187 kfree_skb(skb); 188 skb = skb2; 189 } 190 191 nf_reset(skb); 192 193 if (hh) { 194 int hh_alen; 195 196 read_lock_bh(&hh->hh_lock); 197 hh_alen = HH_DATA_ALIGN(hh->hh_len); 198 memcpy(skb->data - hh_alen, hh->hh_data, hh_alen); 199 read_unlock_bh(&hh->hh_lock); 200 skb_push(skb, hh->hh_len); 201 return hh->hh_output(skb); 202 } else if (dst->neighbour) 203 return dst->neighbour->output(skb); 204 205 if (net_ratelimit()) 206 printk(KERN_DEBUG "ip_finish_output2: No header cache and no neighbour!\n"); 207 kfree_skb(skb); 208 return -EINVAL; 209 } 210 211 int ip_finish_output(struct sk_buff *skb) 212 { 213 struct net_device *dev = skb->dst->dev; 214 215 skb->dev = dev; 216 skb->protocol = htons(ETH_P_IP); 217 218 return NF_HOOK(PF_INET, NF_IP_POST_ROUTING, skb, NULL, dev, 219 ip_finish_output2); 220 } 221 222 int ip_mc_output(struct sk_buff *skb) 223 { 224 struct sock *sk = skb->sk; 225 struct rtable *rt = (struct rtable*)skb->dst; 226 struct net_device *dev = rt->u.dst.dev; 227 228 /* 229 * If the indicated interface is up and running, send the packet. 230 */ 231 IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS); 232 233 skb->dev = dev; 234 skb->protocol = htons(ETH_P_IP); 235 236 /* 237 * Multicasts are looped back for other local users 238 */ 239 240 if (rt->rt_flags&RTCF_MULTICAST) { 241 if ((!sk || inet_sk(sk)->mc_loop) 242 #ifdef CONFIG_IP_MROUTE 243 /* Small optimization: do not loopback not local frames, 244 which returned after forwarding; they will be dropped 245 by ip_mr_input in any case. 246 Note, that local frames are looped back to be delivered 247 to local recipients. 248 249 This check is duplicated in ip_mr_input at the moment. 250 */ 251 && ((rt->rt_flags&RTCF_LOCAL) || !(IPCB(skb)->flags&IPSKB_FORWARDED)) 252 #endif 253 ) { 254 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC); 255 if (newskb) 256 NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL, 257 newskb->dev, 258 ip_dev_loopback_xmit); 259 } 260 261 /* Multicasts with ttl 0 must not go beyond the host */ 262 263 if (skb->nh.iph->ttl == 0) { 264 kfree_skb(skb); 265 return 0; 266 } 267 } 268 269 if (rt->rt_flags&RTCF_BROADCAST) { 270 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC); 271 if (newskb) 272 NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL, 273 newskb->dev, ip_dev_loopback_xmit); 274 } 275 276 if (skb->len > dst_mtu(&rt->u.dst)) 277 return ip_fragment(skb, ip_finish_output); 278 else 279 return ip_finish_output(skb); 280 } 281 282 int ip_output(struct sk_buff *skb) 283 { 284 IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS); 285 286 if (skb->len > dst_mtu(skb->dst) && !skb_shinfo(skb)->tso_size) 287 return ip_fragment(skb, ip_finish_output); 288 else 289 return ip_finish_output(skb); 290 } 291 292 int ip_queue_xmit(struct sk_buff *skb, int ipfragok) 293 { 294 struct sock *sk = skb->sk; 295 struct inet_sock *inet = inet_sk(sk); 296 struct ip_options *opt = inet->opt; 297 struct rtable *rt; 298 struct iphdr *iph; 299 300 /* Skip all of this if the packet is already routed, 301 * f.e. by something like SCTP. 302 */ 303 rt = (struct rtable *) skb->dst; 304 if (rt != NULL) 305 goto packet_routed; 306 307 /* Make sure we can route this packet. */ 308 rt = (struct rtable *)__sk_dst_check(sk, 0); 309 if (rt == NULL) { 310 u32 daddr; 311 312 /* Use correct destination address if we have options. */ 313 daddr = inet->daddr; 314 if(opt && opt->srr) 315 daddr = opt->faddr; 316 317 { 318 struct flowi fl = { .oif = sk->sk_bound_dev_if, 319 .nl_u = { .ip4_u = 320 { .daddr = daddr, 321 .saddr = inet->saddr, 322 .tos = RT_CONN_FLAGS(sk) } }, 323 .proto = sk->sk_protocol, 324 .uli_u = { .ports = 325 { .sport = inet->sport, 326 .dport = inet->dport } } }; 327 328 /* If this fails, retransmit mechanism of transport layer will 329 * keep trying until route appears or the connection times 330 * itself out. 331 */ 332 if (ip_route_output_flow(&rt, &fl, sk, 0)) 333 goto no_route; 334 } 335 __sk_dst_set(sk, &rt->u.dst); 336 tcp_v4_setup_caps(sk, &rt->u.dst); 337 } 338 skb->dst = dst_clone(&rt->u.dst); 339 340 packet_routed: 341 if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway) 342 goto no_route; 343 344 /* OK, we know where to send it, allocate and build IP header. */ 345 iph = (struct iphdr *) skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0)); 346 *((__u16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff)); 347 iph->tot_len = htons(skb->len); 348 if (ip_dont_fragment(sk, &rt->u.dst) && !ipfragok) 349 iph->frag_off = htons(IP_DF); 350 else 351 iph->frag_off = 0; 352 iph->ttl = ip_select_ttl(inet, &rt->u.dst); 353 iph->protocol = sk->sk_protocol; 354 iph->saddr = rt->rt_src; 355 iph->daddr = rt->rt_dst; 356 skb->nh.iph = iph; 357 /* Transport layer set skb->h.foo itself. */ 358 359 if (opt && opt->optlen) { 360 iph->ihl += opt->optlen >> 2; 361 ip_options_build(skb, opt, inet->daddr, rt, 0); 362 } 363 364 ip_select_ident_more(iph, &rt->u.dst, sk, skb_shinfo(skb)->tso_segs); 365 366 /* Add an IP checksum. */ 367 ip_send_check(iph); 368 369 skb->priority = sk->sk_priority; 370 371 return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev, 372 dst_output); 373 374 no_route: 375 IP_INC_STATS(IPSTATS_MIB_OUTNOROUTES); 376 kfree_skb(skb); 377 return -EHOSTUNREACH; 378 } 379 380 381 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from) 382 { 383 to->pkt_type = from->pkt_type; 384 to->priority = from->priority; 385 to->protocol = from->protocol; 386 to->security = from->security; 387 dst_release(to->dst); 388 to->dst = dst_clone(from->dst); 389 to->dev = from->dev; 390 391 /* Copy the flags to each fragment. */ 392 IPCB(to)->flags = IPCB(from)->flags; 393 394 #ifdef CONFIG_NET_SCHED 395 to->tc_index = from->tc_index; 396 #endif 397 #ifdef CONFIG_NETFILTER 398 to->nfmark = from->nfmark; 399 to->nfcache = from->nfcache; 400 /* Connection association is same as pre-frag packet */ 401 nf_conntrack_put(to->nfct); 402 to->nfct = from->nfct; 403 nf_conntrack_get(to->nfct); 404 to->nfctinfo = from->nfctinfo; 405 #ifdef CONFIG_BRIDGE_NETFILTER 406 nf_bridge_put(to->nf_bridge); 407 to->nf_bridge = from->nf_bridge; 408 nf_bridge_get(to->nf_bridge); 409 #endif 410 #endif 411 } 412 413 /* 414 * This IP datagram is too large to be sent in one piece. Break it up into 415 * smaller pieces (each of size equal to IP header plus 416 * a block of the data of the original IP data part) that will yet fit in a 417 * single device frame, and queue such a frame for sending. 418 */ 419 420 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*)) 421 { 422 struct iphdr *iph; 423 int raw = 0; 424 int ptr; 425 struct net_device *dev; 426 struct sk_buff *skb2; 427 unsigned int mtu, hlen, left, len, ll_rs; 428 int offset; 429 int not_last_frag; 430 struct rtable *rt = (struct rtable*)skb->dst; 431 int err = 0; 432 433 dev = rt->u.dst.dev; 434 435 /* 436 * Point into the IP datagram header. 437 */ 438 439 iph = skb->nh.iph; 440 441 if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) { 442 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, 443 htonl(dst_mtu(&rt->u.dst))); 444 kfree_skb(skb); 445 return -EMSGSIZE; 446 } 447 448 /* 449 * Setup starting values. 450 */ 451 452 hlen = iph->ihl * 4; 453 mtu = dst_mtu(&rt->u.dst) - hlen; /* Size of data space */ 454 455 /* When frag_list is given, use it. First, check its validity: 456 * some transformers could create wrong frag_list or break existing 457 * one, it is not prohibited. In this case fall back to copying. 458 * 459 * LATER: this step can be merged to real generation of fragments, 460 * we can switch to copy when see the first bad fragment. 461 */ 462 if (skb_shinfo(skb)->frag_list) { 463 struct sk_buff *frag; 464 int first_len = skb_pagelen(skb); 465 466 if (first_len - hlen > mtu || 467 ((first_len - hlen) & 7) || 468 (iph->frag_off & htons(IP_MF|IP_OFFSET)) || 469 skb_cloned(skb)) 470 goto slow_path; 471 472 for (frag = skb_shinfo(skb)->frag_list; frag; frag = frag->next) { 473 /* Correct geometry. */ 474 if (frag->len > mtu || 475 ((frag->len & 7) && frag->next) || 476 skb_headroom(frag) < hlen) 477 goto slow_path; 478 479 /* Partially cloned skb? */ 480 if (skb_shared(frag)) 481 goto slow_path; 482 483 BUG_ON(frag->sk); 484 if (skb->sk) { 485 sock_hold(skb->sk); 486 frag->sk = skb->sk; 487 frag->destructor = sock_wfree; 488 skb->truesize -= frag->truesize; 489 } 490 } 491 492 /* Everything is OK. Generate! */ 493 494 err = 0; 495 offset = 0; 496 frag = skb_shinfo(skb)->frag_list; 497 skb_shinfo(skb)->frag_list = NULL; 498 skb->data_len = first_len - skb_headlen(skb); 499 skb->len = first_len; 500 iph->tot_len = htons(first_len); 501 iph->frag_off = htons(IP_MF); 502 ip_send_check(iph); 503 504 for (;;) { 505 /* Prepare header of the next frame, 506 * before previous one went down. */ 507 if (frag) { 508 frag->ip_summed = CHECKSUM_NONE; 509 frag->h.raw = frag->data; 510 frag->nh.raw = __skb_push(frag, hlen); 511 memcpy(frag->nh.raw, iph, hlen); 512 iph = frag->nh.iph; 513 iph->tot_len = htons(frag->len); 514 ip_copy_metadata(frag, skb); 515 if (offset == 0) 516 ip_options_fragment(frag); 517 offset += skb->len - hlen; 518 iph->frag_off = htons(offset>>3); 519 if (frag->next != NULL) 520 iph->frag_off |= htons(IP_MF); 521 /* Ready, complete checksum */ 522 ip_send_check(iph); 523 } 524 525 err = output(skb); 526 527 if (err || !frag) 528 break; 529 530 skb = frag; 531 frag = skb->next; 532 skb->next = NULL; 533 } 534 535 if (err == 0) { 536 IP_INC_STATS(IPSTATS_MIB_FRAGOKS); 537 return 0; 538 } 539 540 while (frag) { 541 skb = frag->next; 542 kfree_skb(frag); 543 frag = skb; 544 } 545 IP_INC_STATS(IPSTATS_MIB_FRAGFAILS); 546 return err; 547 } 548 549 slow_path: 550 left = skb->len - hlen; /* Space per frame */ 551 ptr = raw + hlen; /* Where to start from */ 552 553 #ifdef CONFIG_BRIDGE_NETFILTER 554 /* for bridged IP traffic encapsulated inside f.e. a vlan header, 555 * we need to make room for the encapsulating header */ 556 ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, nf_bridge_pad(skb)); 557 mtu -= nf_bridge_pad(skb); 558 #else 559 ll_rs = LL_RESERVED_SPACE(rt->u.dst.dev); 560 #endif 561 /* 562 * Fragment the datagram. 563 */ 564 565 offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3; 566 not_last_frag = iph->frag_off & htons(IP_MF); 567 568 /* 569 * Keep copying data until we run out. 570 */ 571 572 while(left > 0) { 573 len = left; 574 /* IF: it doesn't fit, use 'mtu' - the data space left */ 575 if (len > mtu) 576 len = mtu; 577 /* IF: we are not sending upto and including the packet end 578 then align the next start on an eight byte boundary */ 579 if (len < left) { 580 len &= ~7; 581 } 582 /* 583 * Allocate buffer. 584 */ 585 586 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) { 587 NETDEBUG(printk(KERN_INFO "IP: frag: no memory for new fragment!\n")); 588 err = -ENOMEM; 589 goto fail; 590 } 591 592 /* 593 * Set up data on packet 594 */ 595 596 ip_copy_metadata(skb2, skb); 597 skb_reserve(skb2, ll_rs); 598 skb_put(skb2, len + hlen); 599 skb2->nh.raw = skb2->data; 600 skb2->h.raw = skb2->data + hlen; 601 602 /* 603 * Charge the memory for the fragment to any owner 604 * it might possess 605 */ 606 607 if (skb->sk) 608 skb_set_owner_w(skb2, skb->sk); 609 610 /* 611 * Copy the packet header into the new buffer. 612 */ 613 614 memcpy(skb2->nh.raw, skb->data, hlen); 615 616 /* 617 * Copy a block of the IP datagram. 618 */ 619 if (skb_copy_bits(skb, ptr, skb2->h.raw, len)) 620 BUG(); 621 left -= len; 622 623 /* 624 * Fill in the new header fields. 625 */ 626 iph = skb2->nh.iph; 627 iph->frag_off = htons((offset >> 3)); 628 629 /* ANK: dirty, but effective trick. Upgrade options only if 630 * the segment to be fragmented was THE FIRST (otherwise, 631 * options are already fixed) and make it ONCE 632 * on the initial skb, so that all the following fragments 633 * will inherit fixed options. 634 */ 635 if (offset == 0) 636 ip_options_fragment(skb); 637 638 /* 639 * Added AC : If we are fragmenting a fragment that's not the 640 * last fragment then keep MF on each bit 641 */ 642 if (left > 0 || not_last_frag) 643 iph->frag_off |= htons(IP_MF); 644 ptr += len; 645 offset += len; 646 647 /* 648 * Put this fragment into the sending queue. 649 */ 650 651 IP_INC_STATS(IPSTATS_MIB_FRAGCREATES); 652 653 iph->tot_len = htons(len + hlen); 654 655 ip_send_check(iph); 656 657 err = output(skb2); 658 if (err) 659 goto fail; 660 } 661 kfree_skb(skb); 662 IP_INC_STATS(IPSTATS_MIB_FRAGOKS); 663 return err; 664 665 fail: 666 kfree_skb(skb); 667 IP_INC_STATS(IPSTATS_MIB_FRAGFAILS); 668 return err; 669 } 670 671 int 672 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb) 673 { 674 struct iovec *iov = from; 675 676 if (skb->ip_summed == CHECKSUM_HW) { 677 if (memcpy_fromiovecend(to, iov, offset, len) < 0) 678 return -EFAULT; 679 } else { 680 unsigned int csum = 0; 681 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0) 682 return -EFAULT; 683 skb->csum = csum_block_add(skb->csum, csum, odd); 684 } 685 return 0; 686 } 687 688 static inline unsigned int 689 csum_page(struct page *page, int offset, int copy) 690 { 691 char *kaddr; 692 unsigned int csum; 693 kaddr = kmap(page); 694 csum = csum_partial(kaddr + offset, copy, 0); 695 kunmap(page); 696 return csum; 697 } 698 699 /* 700 * ip_append_data() and ip_append_page() can make one large IP datagram 701 * from many pieces of data. Each pieces will be holded on the socket 702 * until ip_push_pending_frames() is called. Each piece can be a page 703 * or non-page data. 704 * 705 * Not only UDP, other transport protocols - e.g. raw sockets - can use 706 * this interface potentially. 707 * 708 * LATER: length must be adjusted by pad at tail, when it is required. 709 */ 710 int ip_append_data(struct sock *sk, 711 int getfrag(void *from, char *to, int offset, int len, 712 int odd, struct sk_buff *skb), 713 void *from, int length, int transhdrlen, 714 struct ipcm_cookie *ipc, struct rtable *rt, 715 unsigned int flags) 716 { 717 struct inet_sock *inet = inet_sk(sk); 718 struct sk_buff *skb; 719 720 struct ip_options *opt = NULL; 721 int hh_len; 722 int exthdrlen; 723 int mtu; 724 int copy; 725 int err; 726 int offset = 0; 727 unsigned int maxfraglen, fragheaderlen; 728 int csummode = CHECKSUM_NONE; 729 730 if (flags&MSG_PROBE) 731 return 0; 732 733 if (skb_queue_empty(&sk->sk_write_queue)) { 734 /* 735 * setup for corking. 736 */ 737 opt = ipc->opt; 738 if (opt) { 739 if (inet->cork.opt == NULL) { 740 inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation); 741 if (unlikely(inet->cork.opt == NULL)) 742 return -ENOBUFS; 743 } 744 memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen); 745 inet->cork.flags |= IPCORK_OPT; 746 inet->cork.addr = ipc->addr; 747 } 748 dst_hold(&rt->u.dst); 749 inet->cork.fragsize = mtu = dst_mtu(rt->u.dst.path); 750 inet->cork.rt = rt; 751 inet->cork.length = 0; 752 sk->sk_sndmsg_page = NULL; 753 sk->sk_sndmsg_off = 0; 754 if ((exthdrlen = rt->u.dst.header_len) != 0) { 755 length += exthdrlen; 756 transhdrlen += exthdrlen; 757 } 758 } else { 759 rt = inet->cork.rt; 760 if (inet->cork.flags & IPCORK_OPT) 761 opt = inet->cork.opt; 762 763 transhdrlen = 0; 764 exthdrlen = 0; 765 mtu = inet->cork.fragsize; 766 } 767 hh_len = LL_RESERVED_SPACE(rt->u.dst.dev); 768 769 fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0); 770 maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen; 771 772 if (inet->cork.length + length > 0xFFFF - fragheaderlen) { 773 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen); 774 return -EMSGSIZE; 775 } 776 777 /* 778 * transhdrlen > 0 means that this is the first fragment and we wish 779 * it won't be fragmented in the future. 780 */ 781 if (transhdrlen && 782 length + fragheaderlen <= mtu && 783 rt->u.dst.dev->features&(NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM) && 784 !exthdrlen) 785 csummode = CHECKSUM_HW; 786 787 inet->cork.length += length; 788 789 /* So, what's going on in the loop below? 790 * 791 * We use calculated fragment length to generate chained skb, 792 * each of segments is IP fragment ready for sending to network after 793 * adding appropriate IP header. 794 */ 795 796 if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) 797 goto alloc_new_skb; 798 799 while (length > 0) { 800 /* Check if the remaining data fits into current packet. */ 801 copy = mtu - skb->len; 802 if (copy < length) 803 copy = maxfraglen - skb->len; 804 if (copy <= 0) { 805 char *data; 806 unsigned int datalen; 807 unsigned int fraglen; 808 unsigned int fraggap; 809 unsigned int alloclen; 810 struct sk_buff *skb_prev; 811 alloc_new_skb: 812 skb_prev = skb; 813 if (skb_prev) 814 fraggap = skb_prev->len - maxfraglen; 815 else 816 fraggap = 0; 817 818 /* 819 * If remaining data exceeds the mtu, 820 * we know we need more fragment(s). 821 */ 822 datalen = length + fraggap; 823 if (datalen > mtu - fragheaderlen) 824 datalen = maxfraglen - fragheaderlen; 825 fraglen = datalen + fragheaderlen; 826 827 if ((flags & MSG_MORE) && 828 !(rt->u.dst.dev->features&NETIF_F_SG)) 829 alloclen = mtu; 830 else 831 alloclen = datalen + fragheaderlen; 832 833 /* The last fragment gets additional space at tail. 834 * Note, with MSG_MORE we overallocate on fragments, 835 * because we have no idea what fragment will be 836 * the last. 837 */ 838 if (datalen == length) 839 alloclen += rt->u.dst.trailer_len; 840 841 if (transhdrlen) { 842 skb = sock_alloc_send_skb(sk, 843 alloclen + hh_len + 15, 844 (flags & MSG_DONTWAIT), &err); 845 } else { 846 skb = NULL; 847 if (atomic_read(&sk->sk_wmem_alloc) <= 848 2 * sk->sk_sndbuf) 849 skb = sock_wmalloc(sk, 850 alloclen + hh_len + 15, 1, 851 sk->sk_allocation); 852 if (unlikely(skb == NULL)) 853 err = -ENOBUFS; 854 } 855 if (skb == NULL) 856 goto error; 857 858 /* 859 * Fill in the control structures 860 */ 861 skb->ip_summed = csummode; 862 skb->csum = 0; 863 skb_reserve(skb, hh_len); 864 865 /* 866 * Find where to start putting bytes. 867 */ 868 data = skb_put(skb, fraglen); 869 skb->nh.raw = data + exthdrlen; 870 data += fragheaderlen; 871 skb->h.raw = data + exthdrlen; 872 873 if (fraggap) { 874 skb->csum = skb_copy_and_csum_bits( 875 skb_prev, maxfraglen, 876 data + transhdrlen, fraggap, 0); 877 skb_prev->csum = csum_sub(skb_prev->csum, 878 skb->csum); 879 data += fraggap; 880 skb_trim(skb_prev, maxfraglen); 881 } 882 883 copy = datalen - transhdrlen - fraggap; 884 if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) { 885 err = -EFAULT; 886 kfree_skb(skb); 887 goto error; 888 } 889 890 offset += copy; 891 length -= datalen - fraggap; 892 transhdrlen = 0; 893 exthdrlen = 0; 894 csummode = CHECKSUM_NONE; 895 896 /* 897 * Put the packet on the pending queue. 898 */ 899 __skb_queue_tail(&sk->sk_write_queue, skb); 900 continue; 901 } 902 903 if (copy > length) 904 copy = length; 905 906 if (!(rt->u.dst.dev->features&NETIF_F_SG)) { 907 unsigned int off; 908 909 off = skb->len; 910 if (getfrag(from, skb_put(skb, copy), 911 offset, copy, off, skb) < 0) { 912 __skb_trim(skb, off); 913 err = -EFAULT; 914 goto error; 915 } 916 } else { 917 int i = skb_shinfo(skb)->nr_frags; 918 skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1]; 919 struct page *page = sk->sk_sndmsg_page; 920 int off = sk->sk_sndmsg_off; 921 unsigned int left; 922 923 if (page && (left = PAGE_SIZE - off) > 0) { 924 if (copy >= left) 925 copy = left; 926 if (page != frag->page) { 927 if (i == MAX_SKB_FRAGS) { 928 err = -EMSGSIZE; 929 goto error; 930 } 931 get_page(page); 932 skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0); 933 frag = &skb_shinfo(skb)->frags[i]; 934 } 935 } else if (i < MAX_SKB_FRAGS) { 936 if (copy > PAGE_SIZE) 937 copy = PAGE_SIZE; 938 page = alloc_pages(sk->sk_allocation, 0); 939 if (page == NULL) { 940 err = -ENOMEM; 941 goto error; 942 } 943 sk->sk_sndmsg_page = page; 944 sk->sk_sndmsg_off = 0; 945 946 skb_fill_page_desc(skb, i, page, 0, 0); 947 frag = &skb_shinfo(skb)->frags[i]; 948 skb->truesize += PAGE_SIZE; 949 atomic_add(PAGE_SIZE, &sk->sk_wmem_alloc); 950 } else { 951 err = -EMSGSIZE; 952 goto error; 953 } 954 if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) { 955 err = -EFAULT; 956 goto error; 957 } 958 sk->sk_sndmsg_off += copy; 959 frag->size += copy; 960 skb->len += copy; 961 skb->data_len += copy; 962 } 963 offset += copy; 964 length -= copy; 965 } 966 967 return 0; 968 969 error: 970 inet->cork.length -= length; 971 IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS); 972 return err; 973 } 974 975 ssize_t ip_append_page(struct sock *sk, struct page *page, 976 int offset, size_t size, int flags) 977 { 978 struct inet_sock *inet = inet_sk(sk); 979 struct sk_buff *skb; 980 struct rtable *rt; 981 struct ip_options *opt = NULL; 982 int hh_len; 983 int mtu; 984 int len; 985 int err; 986 unsigned int maxfraglen, fragheaderlen, fraggap; 987 988 if (inet->hdrincl) 989 return -EPERM; 990 991 if (flags&MSG_PROBE) 992 return 0; 993 994 if (skb_queue_empty(&sk->sk_write_queue)) 995 return -EINVAL; 996 997 rt = inet->cork.rt; 998 if (inet->cork.flags & IPCORK_OPT) 999 opt = inet->cork.opt; 1000 1001 if (!(rt->u.dst.dev->features&NETIF_F_SG)) 1002 return -EOPNOTSUPP; 1003 1004 hh_len = LL_RESERVED_SPACE(rt->u.dst.dev); 1005 mtu = inet->cork.fragsize; 1006 1007 fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0); 1008 maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen; 1009 1010 if (inet->cork.length + size > 0xFFFF - fragheaderlen) { 1011 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu); 1012 return -EMSGSIZE; 1013 } 1014 1015 if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) 1016 return -EINVAL; 1017 1018 inet->cork.length += size; 1019 1020 while (size > 0) { 1021 int i; 1022 1023 /* Check if the remaining data fits into current packet. */ 1024 len = mtu - skb->len; 1025 if (len < size) 1026 len = maxfraglen - skb->len; 1027 if (len <= 0) { 1028 struct sk_buff *skb_prev; 1029 char *data; 1030 struct iphdr *iph; 1031 int alloclen; 1032 1033 skb_prev = skb; 1034 if (skb_prev) 1035 fraggap = skb_prev->len - maxfraglen; 1036 else 1037 fraggap = 0; 1038 1039 alloclen = fragheaderlen + hh_len + fraggap + 15; 1040 skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation); 1041 if (unlikely(!skb)) { 1042 err = -ENOBUFS; 1043 goto error; 1044 } 1045 1046 /* 1047 * Fill in the control structures 1048 */ 1049 skb->ip_summed = CHECKSUM_NONE; 1050 skb->csum = 0; 1051 skb_reserve(skb, hh_len); 1052 1053 /* 1054 * Find where to start putting bytes. 1055 */ 1056 data = skb_put(skb, fragheaderlen + fraggap); 1057 skb->nh.iph = iph = (struct iphdr *)data; 1058 data += fragheaderlen; 1059 skb->h.raw = data; 1060 1061 if (fraggap) { 1062 skb->csum = skb_copy_and_csum_bits( 1063 skb_prev, maxfraglen, 1064 data, fraggap, 0); 1065 skb_prev->csum = csum_sub(skb_prev->csum, 1066 skb->csum); 1067 skb_trim(skb_prev, maxfraglen); 1068 } 1069 1070 /* 1071 * Put the packet on the pending queue. 1072 */ 1073 __skb_queue_tail(&sk->sk_write_queue, skb); 1074 continue; 1075 } 1076 1077 i = skb_shinfo(skb)->nr_frags; 1078 if (len > size) 1079 len = size; 1080 if (skb_can_coalesce(skb, i, page, offset)) { 1081 skb_shinfo(skb)->frags[i-1].size += len; 1082 } else if (i < MAX_SKB_FRAGS) { 1083 get_page(page); 1084 skb_fill_page_desc(skb, i, page, offset, len); 1085 } else { 1086 err = -EMSGSIZE; 1087 goto error; 1088 } 1089 1090 if (skb->ip_summed == CHECKSUM_NONE) { 1091 unsigned int csum; 1092 csum = csum_page(page, offset, len); 1093 skb->csum = csum_block_add(skb->csum, csum, skb->len); 1094 } 1095 1096 skb->len += len; 1097 skb->data_len += len; 1098 offset += len; 1099 size -= len; 1100 } 1101 return 0; 1102 1103 error: 1104 inet->cork.length -= size; 1105 IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS); 1106 return err; 1107 } 1108 1109 /* 1110 * Combined all pending IP fragments on the socket as one IP datagram 1111 * and push them out. 1112 */ 1113 int ip_push_pending_frames(struct sock *sk) 1114 { 1115 struct sk_buff *skb, *tmp_skb; 1116 struct sk_buff **tail_skb; 1117 struct inet_sock *inet = inet_sk(sk); 1118 struct ip_options *opt = NULL; 1119 struct rtable *rt = inet->cork.rt; 1120 struct iphdr *iph; 1121 int df = 0; 1122 __u8 ttl; 1123 int err = 0; 1124 1125 if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL) 1126 goto out; 1127 tail_skb = &(skb_shinfo(skb)->frag_list); 1128 1129 /* move skb->data to ip header from ext header */ 1130 if (skb->data < skb->nh.raw) 1131 __skb_pull(skb, skb->nh.raw - skb->data); 1132 while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) { 1133 __skb_pull(tmp_skb, skb->h.raw - skb->nh.raw); 1134 *tail_skb = tmp_skb; 1135 tail_skb = &(tmp_skb->next); 1136 skb->len += tmp_skb->len; 1137 skb->data_len += tmp_skb->len; 1138 skb->truesize += tmp_skb->truesize; 1139 __sock_put(tmp_skb->sk); 1140 tmp_skb->destructor = NULL; 1141 tmp_skb->sk = NULL; 1142 } 1143 1144 /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow 1145 * to fragment the frame generated here. No matter, what transforms 1146 * how transforms change size of the packet, it will come out. 1147 */ 1148 if (inet->pmtudisc != IP_PMTUDISC_DO) 1149 skb->local_df = 1; 1150 1151 /* DF bit is set when we want to see DF on outgoing frames. 1152 * If local_df is set too, we still allow to fragment this frame 1153 * locally. */ 1154 if (inet->pmtudisc == IP_PMTUDISC_DO || 1155 (skb->len <= dst_mtu(&rt->u.dst) && 1156 ip_dont_fragment(sk, &rt->u.dst))) 1157 df = htons(IP_DF); 1158 1159 if (inet->cork.flags & IPCORK_OPT) 1160 opt = inet->cork.opt; 1161 1162 if (rt->rt_type == RTN_MULTICAST) 1163 ttl = inet->mc_ttl; 1164 else 1165 ttl = ip_select_ttl(inet, &rt->u.dst); 1166 1167 iph = (struct iphdr *)skb->data; 1168 iph->version = 4; 1169 iph->ihl = 5; 1170 if (opt) { 1171 iph->ihl += opt->optlen>>2; 1172 ip_options_build(skb, opt, inet->cork.addr, rt, 0); 1173 } 1174 iph->tos = inet->tos; 1175 iph->tot_len = htons(skb->len); 1176 iph->frag_off = df; 1177 if (!df) { 1178 __ip_select_ident(iph, &rt->u.dst, 0); 1179 } else { 1180 iph->id = htons(inet->id++); 1181 } 1182 iph->ttl = ttl; 1183 iph->protocol = sk->sk_protocol; 1184 iph->saddr = rt->rt_src; 1185 iph->daddr = rt->rt_dst; 1186 ip_send_check(iph); 1187 1188 skb->priority = sk->sk_priority; 1189 skb->dst = dst_clone(&rt->u.dst); 1190 1191 /* Netfilter gets whole the not fragmented skb. */ 1192 err = NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, 1193 skb->dst->dev, dst_output); 1194 if (err) { 1195 if (err > 0) 1196 err = inet->recverr ? net_xmit_errno(err) : 0; 1197 if (err) 1198 goto error; 1199 } 1200 1201 out: 1202 inet->cork.flags &= ~IPCORK_OPT; 1203 if (inet->cork.opt) { 1204 kfree(inet->cork.opt); 1205 inet->cork.opt = NULL; 1206 } 1207 if (inet->cork.rt) { 1208 ip_rt_put(inet->cork.rt); 1209 inet->cork.rt = NULL; 1210 } 1211 return err; 1212 1213 error: 1214 IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS); 1215 goto out; 1216 } 1217 1218 /* 1219 * Throw away all pending data on the socket. 1220 */ 1221 void ip_flush_pending_frames(struct sock *sk) 1222 { 1223 struct inet_sock *inet = inet_sk(sk); 1224 struct sk_buff *skb; 1225 1226 while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL) 1227 kfree_skb(skb); 1228 1229 inet->cork.flags &= ~IPCORK_OPT; 1230 if (inet->cork.opt) { 1231 kfree(inet->cork.opt); 1232 inet->cork.opt = NULL; 1233 } 1234 if (inet->cork.rt) { 1235 ip_rt_put(inet->cork.rt); 1236 inet->cork.rt = NULL; 1237 } 1238 } 1239 1240 1241 /* 1242 * Fetch data from kernel space and fill in checksum if needed. 1243 */ 1244 static int ip_reply_glue_bits(void *dptr, char *to, int offset, 1245 int len, int odd, struct sk_buff *skb) 1246 { 1247 unsigned int csum; 1248 1249 csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0); 1250 skb->csum = csum_block_add(skb->csum, csum, odd); 1251 return 0; 1252 } 1253 1254 /* 1255 * Generic function to send a packet as reply to another packet. 1256 * Used to send TCP resets so far. ICMP should use this function too. 1257 * 1258 * Should run single threaded per socket because it uses the sock 1259 * structure to pass arguments. 1260 * 1261 * LATER: switch from ip_build_xmit to ip_append_* 1262 */ 1263 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg, 1264 unsigned int len) 1265 { 1266 struct inet_sock *inet = inet_sk(sk); 1267 struct { 1268 struct ip_options opt; 1269 char data[40]; 1270 } replyopts; 1271 struct ipcm_cookie ipc; 1272 u32 daddr; 1273 struct rtable *rt = (struct rtable*)skb->dst; 1274 1275 if (ip_options_echo(&replyopts.opt, skb)) 1276 return; 1277 1278 daddr = ipc.addr = rt->rt_src; 1279 ipc.opt = NULL; 1280 1281 if (replyopts.opt.optlen) { 1282 ipc.opt = &replyopts.opt; 1283 1284 if (ipc.opt->srr) 1285 daddr = replyopts.opt.faddr; 1286 } 1287 1288 { 1289 struct flowi fl = { .nl_u = { .ip4_u = 1290 { .daddr = daddr, 1291 .saddr = rt->rt_spec_dst, 1292 .tos = RT_TOS(skb->nh.iph->tos) } }, 1293 /* Not quite clean, but right. */ 1294 .uli_u = { .ports = 1295 { .sport = skb->h.th->dest, 1296 .dport = skb->h.th->source } }, 1297 .proto = sk->sk_protocol }; 1298 if (ip_route_output_key(&rt, &fl)) 1299 return; 1300 } 1301 1302 /* And let IP do all the hard work. 1303 1304 This chunk is not reenterable, hence spinlock. 1305 Note that it uses the fact, that this function is called 1306 with locally disabled BH and that sk cannot be already spinlocked. 1307 */ 1308 bh_lock_sock(sk); 1309 inet->tos = skb->nh.iph->tos; 1310 sk->sk_priority = skb->priority; 1311 sk->sk_protocol = skb->nh.iph->protocol; 1312 ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0, 1313 &ipc, rt, MSG_DONTWAIT); 1314 if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) { 1315 if (arg->csumoffset >= 0) 1316 *((u16 *)skb->h.raw + arg->csumoffset) = csum_fold(csum_add(skb->csum, arg->csum)); 1317 skb->ip_summed = CHECKSUM_NONE; 1318 ip_push_pending_frames(sk); 1319 } 1320 1321 bh_unlock_sock(sk); 1322 1323 ip_rt_put(rt); 1324 } 1325 1326 /* 1327 * IP protocol layer initialiser 1328 */ 1329 1330 static struct packet_type ip_packet_type = { 1331 .type = __constant_htons(ETH_P_IP), 1332 .func = ip_rcv, 1333 }; 1334 1335 /* 1336 * IP registers the packet type and then calls the subprotocol initialisers 1337 */ 1338 1339 void __init ip_init(void) 1340 { 1341 dev_add_pack(&ip_packet_type); 1342 1343 ip_rt_init(); 1344 inet_initpeers(); 1345 1346 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS) 1347 igmp_mc_proc_init(); 1348 #endif 1349 } 1350 1351 EXPORT_SYMBOL(ip_finish_output); 1352 EXPORT_SYMBOL(ip_fragment); 1353 EXPORT_SYMBOL(ip_generic_getfrag); 1354 EXPORT_SYMBOL(ip_queue_xmit); 1355 EXPORT_SYMBOL(ip_send_check); 1356 1357 #ifdef CONFIG_SYSCTL 1358 EXPORT_SYMBOL(sysctl_ip_default_ttl); 1359 #endif 1360