net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
   9  *      - move L3 protocol dependent part to this file.
  10  * 23 Mar 2004: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
  11  *      - add get_features() to support various size of conntrack
  12  *        structures.
  13  *
  14  * Derived from net/ipv4/netfilter/ip_conntrack_standalone.c
  15  */
  16
  17 #include <linux/config.h>
  18 #include <linux/types.h>
  19 #include <linux/ip.h>
  20 #include <linux/netfilter.h>
  21 #include <linux/module.h>
  22 #include <linux/skbuff.h>
  23 #include <linux/icmp.h>
  24 #include <linux/sysctl.h>
  25 #include <net/ip.h>
  26
  27 #include <linux/netfilter_ipv4.h>
  28 #include <net/netfilter/nf_conntrack.h>
  29 #include <net/netfilter/nf_conntrack_helper.h>
  30 #include <net/netfilter/nf_conntrack_protocol.h>
  31 #include <net/netfilter/nf_conntrack_l3proto.h>
  32 #include <net/netfilter/nf_conntrack_core.h>
  33 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
  34
  35 #if 0
  36 #define DEBUGP printk
  37 #else
  38 #define DEBUGP(format, args...)
  39 #endif
  40
  41 DECLARE_PER_CPU(struct nf_conntrack_stat, nf_conntrack_stat);
  42
  43 static int ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
  44                              struct nf_conntrack_tuple *tuple)
  45 {
  46         u_int32_t _addrs[2], *ap;
  47         ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
  48                                 sizeof(u_int32_t) * 2, _addrs);
  49         if (ap == NULL)
  50                 return 0;
  51
  52         tuple->src.u3.ip = ap[0];
  53         tuple->dst.u3.ip = ap[1];
  54
  55         return 1;
  56 }
  57
  58 static int ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
  59                            const struct nf_conntrack_tuple *orig)
  60 {
  61         tuple->src.u3.ip = orig->dst.u3.ip;
  62         tuple->dst.u3.ip = orig->src.u3.ip;
  63
  64         return 1;
  65 }
  66
  67 static int ipv4_print_tuple(struct seq_file *s,
  68                             const struct nf_conntrack_tuple *tuple)
  69 {
  70         return seq_printf(s, "src=%u.%u.%u.%u dst=%u.%u.%u.%u ",
  71                           NIPQUAD(tuple->src.u3.ip),
  72                           NIPQUAD(tuple->dst.u3.ip));
  73 }
  74
  75 static int ipv4_print_conntrack(struct seq_file *s,
  76                                 const struct nf_conn *conntrack)
  77 {
  78         return 0;
  79 }
  80
  81 /* Returns new sk_buff, or NULL */
  82 static struct sk_buff *
  83 nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
  84 {
  85         skb_orphan(skb);
  86
  87         local_bh_disable();
  88         skb = ip_defrag(skb, user);
  89         local_bh_enable();
  90
  91         if (skb)
  92                 ip_send_check(skb->nh.iph);
  93
  94         return skb;
  95 }
  96
  97 static int
  98 ipv4_prepare(struct sk_buff **pskb, unsigned int hooknum, unsigned int *dataoff,
  99              u_int8_t *protonum)
 100 {
 101         /* Never happen */
 102         if ((*pskb)->nh.iph->frag_off & htons(IP_OFFSET)) {
 103                 if (net_ratelimit()) {
 104                         printk(KERN_ERR "ipv4_prepare: Frag of proto %u (hook=%u)\n",
 105                         (*pskb)->nh.iph->protocol, hooknum);
 106                 }
 107                 return -NF_DROP;
 108         }
 109
 110         *dataoff = (*pskb)->nh.raw - (*pskb)->data + (*pskb)->nh.iph->ihl*4;
 111         *protonum = (*pskb)->nh.iph->protocol;
 112
 113         return NF_ACCEPT;
 114 }
 115
 116 int nat_module_is_loaded = 0;
 117 static u_int32_t ipv4_get_features(const struct nf_conntrack_tuple *tuple)
 118 {
 119         if (nat_module_is_loaded)
 120                 return NF_CT_F_NAT;
 121
 122         return NF_CT_F_BASIC;
 123 }
 124
 125 static unsigned int ipv4_confirm(unsigned int hooknum,
 126                                  struct sk_buff **pskb,
 127                                  const struct net_device *in,
 128                                  const struct net_device *out,
 129                                  int (*okfn)(struct sk_buff *))
 130 {
 131         /* We've seen it coming out the other side: confirm it */
 132         return nf_conntrack_confirm(pskb);
 133 }
 134
 135 static unsigned int ipv4_conntrack_help(unsigned int hooknum,
 136                                       struct sk_buff **pskb,
 137                                       const struct net_device *in,
 138                                       const struct net_device *out,
 139                                       int (*okfn)(struct sk_buff *))
 140 {
 141         struct nf_conn *ct;
 142         enum ip_conntrack_info ctinfo;
 143
 144         /* This is where we call the helper: as the packet goes out. */
 145         ct = nf_ct_get(*pskb, &ctinfo);
 146         if (ct && ct->helper) {
 147                 unsigned int ret;
 148                 ret = ct->helper->help(pskb,
 149                                        (*pskb)->nh.raw - (*pskb)->data
 150                                                        + (*pskb)->nh.iph->ihl*4,
 151                                        ct, ctinfo);
 152                 if (ret != NF_ACCEPT)
 153                         return ret;
 154         }
 155         return NF_ACCEPT;
 156 }
 157
 158 static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,
 159                                           struct sk_buff **pskb,
 160                                           const struct net_device *in,
 161                                           const struct net_device *out,
 162                                           int (*okfn)(struct sk_buff *))
 163 {
 164 #if !defined(CONFIG_IP_NF_NAT) && !defined(CONFIG_IP_NF_NAT_MODULE)
 165         /* Previously seen (loopback)?  Ignore.  Do this before
 166            fragment check. */
 167         if ((*pskb)->nfct)
 168                 return NF_ACCEPT;
 169 #endif
 170
 171         /* Gather fragments. */
 172         if ((*pskb)->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
 173                 *pskb = nf_ct_ipv4_gather_frags(*pskb,
 174                                                 hooknum == NF_IP_PRE_ROUTING ?
 175                                                 IP_DEFRAG_CONNTRACK_IN :
 176                                                 IP_DEFRAG_CONNTRACK_OUT);
 177                 if (!*pskb)
 178                         return NF_STOLEN;
 179         }
 180         return NF_ACCEPT;
 181 }
 182
 183 static unsigned int ipv4_refrag(unsigned int hooknum,
 184                                 struct sk_buff **pskb,
 185                                 const struct net_device *in,
 186                                 const struct net_device *out,
 187                                 int (*okfn)(struct sk_buff *))
 188 {
 189         struct rtable *rt = (struct rtable *)(*pskb)->dst;
 190
 191         /* We've seen it coming out the other side: confirm */
 192         if (ipv4_confirm(hooknum, pskb, in, out, okfn) != NF_ACCEPT)
 193                 return NF_DROP;
 194
 195         /* Local packets are never produced too large for their
 196            interface.  We degfragment them at LOCAL_OUT, however,
 197            so we have to refragment them here. */
 198         if ((*pskb)->len > dst_mtu(&rt->u.dst) &&
 199             !skb_shinfo(*pskb)->tso_size) {
 200                 /* No hook can be after us, so this should be OK. */
 201                 ip_fragment(*pskb, okfn);
 202                 return NF_STOLEN;
 203         }
 204         return NF_ACCEPT;
 205 }
 206
 207 static unsigned int ipv4_conntrack_in(unsigned int hooknum,
 208                                       struct sk_buff **pskb,
 209                                       const struct net_device *in,
 210                                       const struct net_device *out,
 211                                       int (*okfn)(struct sk_buff *))
 212 {
 213         return nf_conntrack_in(PF_INET, hooknum, pskb);
 214 }
 215
 216 static unsigned int ipv4_conntrack_local(unsigned int hooknum,
 217                                          struct sk_buff **pskb,
 218                                          const struct net_device *in,
 219                                          const struct net_device *out,
 220                                          int (*okfn)(struct sk_buff *))
 221 {
 222         /* root is playing with raw sockets. */
 223         if ((*pskb)->len < sizeof(struct iphdr)
 224             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) {
 225                 if (net_ratelimit())
 226                         printk("ipt_hook: happy cracking.\n");
 227                 return NF_ACCEPT;
 228         }
 229         return nf_conntrack_in(PF_INET, hooknum, pskb);
 230 }
 231
 232 /* Connection tracking may drop packets, but never alters them, so
 233    make it the first hook. */
 234 static struct nf_hook_ops ipv4_conntrack_defrag_ops = {
 235         .hook           = ipv4_conntrack_defrag,
 236         .owner          = THIS_MODULE,
 237         .pf             = PF_INET,
 238         .hooknum        = NF_IP_PRE_ROUTING,
 239         .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 240 };
 241
 242 static struct nf_hook_ops ipv4_conntrack_in_ops = {
 243         .hook           = ipv4_conntrack_in,
 244         .owner          = THIS_MODULE,
 245         .pf             = PF_INET,
 246         .hooknum        = NF_IP_PRE_ROUTING,
 247         .priority       = NF_IP_PRI_CONNTRACK,
 248 };
 249
 250 static struct nf_hook_ops ipv4_conntrack_defrag_local_out_ops = {
 251         .hook           = ipv4_conntrack_defrag,
 252         .owner          = THIS_MODULE,
 253         .pf             = PF_INET,
 254         .hooknum        = NF_IP_LOCAL_OUT,
 255         .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 256 };
 257
 258 static struct nf_hook_ops ipv4_conntrack_local_out_ops = {
 259         .hook           = ipv4_conntrack_local,
 260         .owner          = THIS_MODULE,
 261         .pf             = PF_INET,
 262         .hooknum        = NF_IP_LOCAL_OUT,
 263         .priority       = NF_IP_PRI_CONNTRACK,
 264 };
 265
 266 /* helpers */
 267 static struct nf_hook_ops ipv4_conntrack_helper_out_ops = {
 268         .hook           = ipv4_conntrack_help,
 269         .owner          = THIS_MODULE,
 270         .pf             = PF_INET,
 271         .hooknum        = NF_IP_POST_ROUTING,
 272         .priority       = NF_IP_PRI_CONNTRACK_HELPER,
 273 };
 274
 275 static struct nf_hook_ops ipv4_conntrack_helper_in_ops = {
 276         .hook           = ipv4_conntrack_help,
 277         .owner          = THIS_MODULE,
 278         .pf             = PF_INET,
 279         .hooknum        = NF_IP_LOCAL_IN,
 280         .priority       = NF_IP_PRI_CONNTRACK_HELPER,
 281 };
 282
 283
 284 /* Refragmenter; last chance. */
 285 static struct nf_hook_ops ipv4_conntrack_out_ops = {
 286         .hook           = ipv4_refrag,
 287         .owner          = THIS_MODULE,
 288         .pf             = PF_INET,
 289         .hooknum        = NF_IP_POST_ROUTING,
 290         .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 291 };
 292
 293 static struct nf_hook_ops ipv4_conntrack_local_in_ops = {
 294         .hook           = ipv4_confirm,
 295         .owner          = THIS_MODULE,
 296         .pf             = PF_INET,
 297         .hooknum        = NF_IP_LOCAL_IN,
 298         .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 299 };
 300
 301 #ifdef CONFIG_SYSCTL
 302 /* From nf_conntrack_proto_icmp.c */
 303 extern unsigned long nf_ct_icmp_timeout;
 304 static struct ctl_table_header *nf_ct_ipv4_sysctl_header;
 305
 306 static ctl_table nf_ct_sysctl_table[] = {
 307         {
 308                 .ctl_name       = NET_NF_CONNTRACK_ICMP_TIMEOUT,
 309                 .procname       = "nf_conntrack_icmp_timeout",
 310                 .data           = &nf_ct_icmp_timeout,
 311                 .maxlen         = sizeof(unsigned int),
 312                 .mode           = 0644,
 313                 .proc_handler   = &proc_dointvec_jiffies,
 314         },
 315         { .ctl_name = 0 }
 316 };
 317
 318 static ctl_table nf_ct_netfilter_table[] = {
 319         {
 320                 .ctl_name       = NET_NETFILTER,
 321                 .procname       = "netfilter",
 322                 .mode           = 0555,
 323                 .child          = nf_ct_sysctl_table,
 324         },
 325         { .ctl_name = 0 }
 326 };
 327
 328 static ctl_table nf_ct_net_table[] = {
 329         {
 330                 .ctl_name       = CTL_NET,
 331                 .procname       = "net",
 332                 .mode           = 0555,
 333                 .child          = nf_ct_netfilter_table,
 334         },
 335         { .ctl_name = 0 }
 336 };
 337 #endif
 338
 339 /* Fast function for those who don't want to parse /proc (and I don't
 340    blame them). */
 341 /* Reversing the socket's dst/src point of view gives us the reply
 342    mapping. */
 343 static int
 344 getorigdst(struct sock *sk, int optval, void __user *user, int *len)
 345 {
 346         struct inet_sock *inet = inet_sk(sk);
 347         struct nf_conntrack_tuple_hash *h;
 348         struct nf_conntrack_tuple tuple;
 349
 350         NF_CT_TUPLE_U_BLANK(&tuple);
 351         tuple.src.u3.ip = inet->rcv_saddr;
 352         tuple.src.u.tcp.port = inet->sport;
 353         tuple.dst.u3.ip = inet->daddr;
 354         tuple.dst.u.tcp.port = inet->dport;
 355         tuple.src.l3num = PF_INET;
 356         tuple.dst.protonum = IPPROTO_TCP;
 357
 358         /* We only do TCP at the moment: is there a better way? */
 359         if (strcmp(sk->sk_prot->name, "TCP")) {
 360                 DEBUGP("SO_ORIGINAL_DST: Not a TCP socket\n");
 361                 return -ENOPROTOOPT;
 362         }
 363
 364         if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
 365                 DEBUGP("SO_ORIGINAL_DST: len %u not %u\n",
 366                        *len, sizeof(struct sockaddr_in));
 367                 return -EINVAL;
 368         }
 369
 370         h = nf_conntrack_find_get(&tuple, NULL);
 371         if (h) {
 372                 struct sockaddr_in sin;
 373                 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
 374
 375                 sin.sin_family = AF_INET;
 376                 sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 377                         .tuple.dst.u.tcp.port;
 378                 sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 379                         .tuple.dst.u3.ip;
 380
 381                 DEBUGP("SO_ORIGINAL_DST: %u.%u.%u.%u %u\n",
 382                        NIPQUAD(sin.sin_addr.s_addr), ntohs(sin.sin_port));
 383                 nf_ct_put(ct);
 384                 if (copy_to_user(user, &sin, sizeof(sin)) != 0)
 385                         return -EFAULT;
 386                 else
 387                         return 0;
 388         }
 389         DEBUGP("SO_ORIGINAL_DST: Can't find %u.%u.%u.%u/%u-%u.%u.%u.%u/%u.\n",
 390                NIPQUAD(tuple.src.u3.ip), ntohs(tuple.src.u.tcp.port),
 391                NIPQUAD(tuple.dst.u3.ip), ntohs(tuple.dst.u.tcp.port));
 392         return -ENOENT;
 393 }
 394
 395 static struct nf_sockopt_ops so_getorigdst = {
 396         .pf             = PF_INET,
 397         .get_optmin     = SO_ORIGINAL_DST,
 398         .get_optmax     = SO_ORIGINAL_DST+1,
 399         .get            = &getorigdst,
 400 };
 401
 402 struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 = {
 403         .l3proto         = PF_INET,
 404         .name            = "ipv4",
 405         .pkt_to_tuple    = ipv4_pkt_to_tuple,
 406         .invert_tuple    = ipv4_invert_tuple,
 407         .print_tuple     = ipv4_print_tuple,
 408         .print_conntrack = ipv4_print_conntrack,
 409         .prepare         = ipv4_prepare,
 410         .get_features    = ipv4_get_features,
 411         .me              = THIS_MODULE,
 412 };
 413
 414 extern struct nf_conntrack_protocol nf_conntrack_protocol_tcp4;
 415 extern struct nf_conntrack_protocol nf_conntrack_protocol_udp4;
 416 extern struct nf_conntrack_protocol nf_conntrack_protocol_icmp;
 417 static int init_or_cleanup(int init)
 418 {
 419         int ret = 0;
 420
 421         if (!init) goto cleanup;
 422
 423         ret = nf_register_sockopt(&so_getorigdst);
 424         if (ret < 0) {
 425                 printk(KERN_ERR "Unable to register netfilter socket option\n");
 426                 goto cleanup_nothing;
 427         }
 428
 429         ret = nf_conntrack_protocol_register(&nf_conntrack_protocol_tcp4);
 430         if (ret < 0) {
 431                 printk("nf_conntrack_ipv4: can't register tcp.\n");
 432                 goto cleanup_sockopt;
 433         }
 434
 435         ret = nf_conntrack_protocol_register(&nf_conntrack_protocol_udp4);
 436         if (ret < 0) {
 437                 printk("nf_conntrack_ipv4: can't register udp.\n");
 438                 goto cleanup_tcp;
 439         }
 440
 441         ret = nf_conntrack_protocol_register(&nf_conntrack_protocol_icmp);
 442         if (ret < 0) {
 443                 printk("nf_conntrack_ipv4: can't register icmp.\n");
 444                 goto cleanup_udp;
 445         }
 446
 447         ret = nf_conntrack_l3proto_register(&nf_conntrack_l3proto_ipv4);
 448         if (ret < 0) {
 449                 printk("nf_conntrack_ipv4: can't register ipv4\n");
 450                 goto cleanup_icmp;
 451         }
 452
 453         ret = nf_register_hook(&ipv4_conntrack_defrag_ops);
 454         if (ret < 0) {
 455                 printk("nf_conntrack_ipv4: can't register pre-routing defrag hook.\n");
 456                 goto cleanup_ipv4;
 457         }
 458         ret = nf_register_hook(&ipv4_conntrack_defrag_local_out_ops);
 459         if (ret < 0) {
 460                 printk("nf_conntrack_ipv4: can't register local_out defrag hook.\n");
 461                 goto cleanup_defragops;
 462         }
 463
 464         ret = nf_register_hook(&ipv4_conntrack_in_ops);
 465         if (ret < 0) {
 466                 printk("nf_conntrack_ipv4: can't register pre-routing hook.\n");
 467                 goto cleanup_defraglocalops;
 468         }
 469
 470         ret = nf_register_hook(&ipv4_conntrack_local_out_ops);
 471         if (ret < 0) {
 472                 printk("nf_conntrack_ipv4: can't register local out hook.\n");
 473                 goto cleanup_inops;
 474         }
 475
 476         ret = nf_register_hook(&ipv4_conntrack_helper_in_ops);
 477         if (ret < 0) {
 478                 printk("nf_conntrack_ipv4: can't register local helper hook.\n");
 479                 goto cleanup_inandlocalops;
 480         }
 481
 482         ret = nf_register_hook(&ipv4_conntrack_helper_out_ops);
 483         if (ret < 0) {
 484                 printk("nf_conntrack_ipv4: can't register postrouting helper hook.\n");
 485                 goto cleanup_helperinops;
 486         }
 487
 488         ret = nf_register_hook(&ipv4_conntrack_out_ops);
 489         if (ret < 0) {
 490                 printk("nf_conntrack_ipv4: can't register post-routing hook.\n");
 491                 goto cleanup_helperoutops;
 492         }
 493
 494         ret = nf_register_hook(&ipv4_conntrack_local_in_ops);
 495         if (ret < 0) {
 496                 printk("nf_conntrack_ipv4: can't register local in hook.\n");
 497                 goto cleanup_inoutandlocalops;
 498         }
 499
 500 #ifdef CONFIG_SYSCTL
 501         nf_ct_ipv4_sysctl_header = register_sysctl_table(nf_ct_net_table, 0);
 502         if (nf_ct_ipv4_sysctl_header == NULL) {
 503                 printk("nf_conntrack: can't register to sysctl.\n");
 504                 ret = -ENOMEM;
 505                 goto cleanup_localinops;
 506         }
 507 #endif
 508
 509         /* For use by REJECT target */
 510         ip_ct_attach = __nf_conntrack_attach;
 511
 512         return ret;
 513
 514  cleanup:
 515         synchronize_net();
 516         ip_ct_attach = NULL;
 517 #ifdef CONFIG_SYSCTL
 518         unregister_sysctl_table(nf_ct_ipv4_sysctl_header);
 519  cleanup_localinops:
 520 #endif
 521         nf_unregister_hook(&ipv4_conntrack_local_in_ops);
 522  cleanup_inoutandlocalops:
 523         nf_unregister_hook(&ipv4_conntrack_out_ops);
 524  cleanup_helperoutops:
 525         nf_unregister_hook(&ipv4_conntrack_helper_out_ops);
 526  cleanup_helperinops:
 527         nf_unregister_hook(&ipv4_conntrack_helper_in_ops);
 528  cleanup_inandlocalops:
 529         nf_unregister_hook(&ipv4_conntrack_local_out_ops);
 530  cleanup_inops:
 531         nf_unregister_hook(&ipv4_conntrack_in_ops);
 532  cleanup_defraglocalops:
 533         nf_unregister_hook(&ipv4_conntrack_defrag_local_out_ops);
 534  cleanup_defragops:
 535         nf_unregister_hook(&ipv4_conntrack_defrag_ops);
 536  cleanup_ipv4:
 537         nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 538  cleanup_icmp:
 539         nf_conntrack_protocol_unregister(&nf_conntrack_protocol_icmp);
 540  cleanup_udp:
 541         nf_conntrack_protocol_unregister(&nf_conntrack_protocol_udp4);
 542  cleanup_tcp:
 543         nf_conntrack_protocol_unregister(&nf_conntrack_protocol_tcp4);
 544  cleanup_sockopt:
 545         nf_unregister_sockopt(&so_getorigdst);
 546  cleanup_nothing:
 547         return ret;
 548 }
 549
 550 MODULE_LICENSE("GPL");
 551
 552 static int __init init(void)
 553 {
 554         need_nf_conntrack();
 555         return init_or_cleanup(1);
 556 }
 557
 558 static void __exit fini(void)
 559 {
 560         init_or_cleanup(0);
 561 }
 562
 563 module_init(init);
 564 module_exit(fini);
 565
 566 void need_ip_conntrack(void)
 567 {
 568 }
 569
 570 EXPORT_SYMBOL(need_ip_conntrack);
 571 EXPORT_SYMBOL(nf_ct_ipv4_gather_frags);