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   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
   9 #include <linux/types.h>
  10 #include <linux/ip.h>
  11 #include <linux/netfilter.h>
  12 #include <linux/module.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/icmp.h>
  15 #include <linux/sysctl.h>
  16 #include <net/route.h>
  17 #include <net/ip.h>
  18
  19 #include <linux/netfilter_ipv4.h>
  20 #include <net/netfilter/nf_conntrack.h>
  21 #include <net/netfilter/nf_conntrack_helper.h>
  22 #include <net/netfilter/nf_conntrack_l4proto.h>
  23 #include <net/netfilter/nf_conntrack_l3proto.h>
  24 #include <net/netfilter/nf_conntrack_core.h>
  25 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
  26
  27 #if 0
  28 #define DEBUGP printk
  29 #else
  30 #define DEBUGP(format, args...)
  31 #endif
  32
  33 static int ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
  34                              struct nf_conntrack_tuple *tuple)
  35 {
  36         __be32 _addrs[2], *ap;
  37         ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
  38                                 sizeof(u_int32_t) * 2, _addrs);
  39         if (ap == NULL)
  40                 return 0;
  41
  42         tuple->src.u3.ip = ap[0];
  43         tuple->dst.u3.ip = ap[1];
  44
  45         return 1;
  46 }
  47
  48 static int ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
  49                            const struct nf_conntrack_tuple *orig)
  50 {
  51         tuple->src.u3.ip = orig->dst.u3.ip;
  52         tuple->dst.u3.ip = orig->src.u3.ip;
  53
  54         return 1;
  55 }
  56
  57 static int ipv4_print_tuple(struct seq_file *s,
  58                             const struct nf_conntrack_tuple *tuple)
  59 {
  60         return seq_printf(s, "src=%u.%u.%u.%u dst=%u.%u.%u.%u ",
  61                           NIPQUAD(tuple->src.u3.ip),
  62                           NIPQUAD(tuple->dst.u3.ip));
  63 }
  64
  65 static int ipv4_print_conntrack(struct seq_file *s,
  66                                 const struct nf_conn *conntrack)
  67 {
  68         return 0;
  69 }
  70
  71 /* Returns new sk_buff, or NULL */
  72 static struct sk_buff *
  73 nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
  74 {
  75         skb_orphan(skb);
  76
  77         local_bh_disable();
  78         skb = ip_defrag(skb, user);
  79         local_bh_enable();
  80
  81         if (skb)
  82                 ip_send_check(ip_hdr(skb));
  83
  84         return skb;
  85 }
  86
  87 static int
  88 ipv4_prepare(struct sk_buff **pskb, unsigned int hooknum, unsigned int *dataoff,
  89              u_int8_t *protonum)
  90 {
  91         /* Never happen */
  92         if (ip_hdr(*pskb)->frag_off & htons(IP_OFFSET)) {
  93                 if (net_ratelimit()) {
  94                         printk(KERN_ERR "ipv4_prepare: Frag of proto %u (hook=%u)\n",
  95                         ip_hdr(*pskb)->protocol, hooknum);
  96                 }
  97                 return -NF_DROP;
  98         }
  99
 100         *dataoff = skb_network_offset(*pskb) + ip_hdrlen(*pskb);
 101         *protonum = ip_hdr(*pskb)->protocol;
 102
 103         return NF_ACCEPT;
 104 }
 105
 106 static unsigned int ipv4_confirm(unsigned int hooknum,
 107                                  struct sk_buff **pskb,
 108                                  const struct net_device *in,
 109                                  const struct net_device *out,
 110                                  int (*okfn)(struct sk_buff *))
 111 {
 112         /* We've seen it coming out the other side: confirm it */
 113         return nf_conntrack_confirm(pskb);
 114 }
 115
 116 static unsigned int ipv4_conntrack_help(unsigned int hooknum,
 117                                       struct sk_buff **pskb,
 118                                       const struct net_device *in,
 119                                       const struct net_device *out,
 120                                       int (*okfn)(struct sk_buff *))
 121 {
 122         struct nf_conn *ct;
 123         enum ip_conntrack_info ctinfo;
 124         struct nf_conn_help *help;
 125         struct nf_conntrack_helper *helper;
 126
 127         /* This is where we call the helper: as the packet goes out. */
 128         ct = nf_ct_get(*pskb, &ctinfo);
 129         if (!ct || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY)
 130                 return NF_ACCEPT;
 131
 132         help = nfct_help(ct);
 133         if (!help)
 134                 return NF_ACCEPT;
 135         /* rcu_read_lock()ed by nf_hook_slow */
 136         helper = rcu_dereference(help->helper);
 137         if (!helper)
 138                 return NF_ACCEPT;
 139         return helper->help(pskb, skb_network_offset(*pskb) + ip_hdrlen(*pskb),
 140                             ct, ctinfo);
 141 }
 142
 143 static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,
 144                                           struct sk_buff **pskb,
 145                                           const struct net_device *in,
 146                                           const struct net_device *out,
 147                                           int (*okfn)(struct sk_buff *))
 148 {
 149         /* Previously seen (loopback)?  Ignore.  Do this before
 150            fragment check. */
 151         if ((*pskb)->nfct)
 152                 return NF_ACCEPT;
 153
 154         /* Gather fragments. */
 155         if (ip_hdr(*pskb)->frag_off & htons(IP_MF | IP_OFFSET)) {
 156                 *pskb = nf_ct_ipv4_gather_frags(*pskb,
 157                                                 hooknum == NF_IP_PRE_ROUTING ?
 158                                                 IP_DEFRAG_CONNTRACK_IN :
 159                                                 IP_DEFRAG_CONNTRACK_OUT);
 160                 if (!*pskb)
 161                         return NF_STOLEN;
 162         }
 163         return NF_ACCEPT;
 164 }
 165
 166 static unsigned int ipv4_conntrack_in(unsigned int hooknum,
 167                                       struct sk_buff **pskb,
 168                                       const struct net_device *in,
 169                                       const struct net_device *out,
 170                                       int (*okfn)(struct sk_buff *))
 171 {
 172         return nf_conntrack_in(PF_INET, hooknum, pskb);
 173 }
 174
 175 static unsigned int ipv4_conntrack_local(unsigned int hooknum,
 176                                          struct sk_buff **pskb,
 177                                          const struct net_device *in,
 178                                          const struct net_device *out,
 179                                          int (*okfn)(struct sk_buff *))
 180 {
 181         /* root is playing with raw sockets. */
 182         if ((*pskb)->len < sizeof(struct iphdr)
 183             || ip_hdrlen(*pskb) < sizeof(struct iphdr)) {
 184                 if (net_ratelimit())
 185                         printk("ipt_hook: happy cracking.\n");
 186                 return NF_ACCEPT;
 187         }
 188         return nf_conntrack_in(PF_INET, hooknum, pskb);
 189 }
 190
 191 /* Connection tracking may drop packets, but never alters them, so
 192    make it the first hook. */
 193 static struct nf_hook_ops ipv4_conntrack_ops[] = {
 194         {
 195                 .hook           = ipv4_conntrack_defrag,
 196                 .owner          = THIS_MODULE,
 197                 .pf             = PF_INET,
 198                 .hooknum        = NF_IP_PRE_ROUTING,
 199                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 200         },
 201         {
 202                 .hook           = ipv4_conntrack_in,
 203                 .owner          = THIS_MODULE,
 204                 .pf             = PF_INET,
 205                 .hooknum        = NF_IP_PRE_ROUTING,
 206                 .priority       = NF_IP_PRI_CONNTRACK,
 207         },
 208         {
 209                 .hook           = ipv4_conntrack_defrag,
 210                 .owner          = THIS_MODULE,
 211                 .pf             = PF_INET,
 212                 .hooknum        = NF_IP_LOCAL_OUT,
 213                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 214         },
 215         {
 216                 .hook           = ipv4_conntrack_local,
 217                 .owner          = THIS_MODULE,
 218                 .pf             = PF_INET,
 219                 .hooknum        = NF_IP_LOCAL_OUT,
 220                 .priority       = NF_IP_PRI_CONNTRACK,
 221         },
 222         {
 223                 .hook           = ipv4_conntrack_help,
 224                 .owner          = THIS_MODULE,
 225                 .pf             = PF_INET,
 226                 .hooknum        = NF_IP_POST_ROUTING,
 227                 .priority       = NF_IP_PRI_CONNTRACK_HELPER,
 228         },
 229         {
 230                 .hook           = ipv4_conntrack_help,
 231                 .owner          = THIS_MODULE,
 232                 .pf             = PF_INET,
 233                 .hooknum        = NF_IP_LOCAL_IN,
 234                 .priority       = NF_IP_PRI_CONNTRACK_HELPER,
 235         },
 236         {
 237                 .hook           = ipv4_confirm,
 238                 .owner          = THIS_MODULE,
 239                 .pf             = PF_INET,
 240                 .hooknum        = NF_IP_POST_ROUTING,
 241                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 242         },
 243         {
 244                 .hook           = ipv4_confirm,
 245                 .owner          = THIS_MODULE,
 246                 .pf             = PF_INET,
 247                 .hooknum        = NF_IP_LOCAL_IN,
 248                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 249         },
 250 };
 251
 252 #if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 253 static int log_invalid_proto_min = 0;
 254 static int log_invalid_proto_max = 255;
 255
 256 static ctl_table ip_ct_sysctl_table[] = {
 257         {
 258                 .ctl_name       = NET_IPV4_NF_CONNTRACK_MAX,
 259                 .procname       = "ip_conntrack_max",
 260                 .data           = &nf_conntrack_max,
 261                 .maxlen         = sizeof(int),
 262                 .mode           = 0644,
 263                 .proc_handler   = &proc_dointvec,
 264         },
 265         {
 266                 .ctl_name       = NET_IPV4_NF_CONNTRACK_COUNT,
 267                 .procname       = "ip_conntrack_count",
 268                 .data           = &nf_conntrack_count,
 269                 .maxlen         = sizeof(int),
 270                 .mode           = 0444,
 271                 .proc_handler   = &proc_dointvec,
 272         },
 273         {
 274                 .ctl_name       = NET_IPV4_NF_CONNTRACK_BUCKETS,
 275                 .procname       = "ip_conntrack_buckets",
 276                 .data           = &nf_conntrack_htable_size,
 277                 .maxlen         = sizeof(unsigned int),
 278                 .mode           = 0444,
 279                 .proc_handler   = &proc_dointvec,
 280         },
 281         {
 282                 .ctl_name       = NET_IPV4_NF_CONNTRACK_CHECKSUM,
 283                 .procname       = "ip_conntrack_checksum",
 284                 .data           = &nf_conntrack_checksum,
 285                 .maxlen         = sizeof(int),
 286                 .mode           = 0644,
 287                 .proc_handler   = &proc_dointvec,
 288         },
 289         {
 290                 .ctl_name       = NET_IPV4_NF_CONNTRACK_LOG_INVALID,
 291                 .procname       = "ip_conntrack_log_invalid",
 292                 .data           = &nf_ct_log_invalid,
 293                 .maxlen         = sizeof(unsigned int),
 294                 .mode           = 0644,
 295                 .proc_handler   = &proc_dointvec_minmax,
 296                 .strategy       = &sysctl_intvec,
 297                 .extra1         = &log_invalid_proto_min,
 298                 .extra2         = &log_invalid_proto_max,
 299         },
 300         {
 301                 .ctl_name       = 0
 302         }
 303 };
 304 #endif /* CONFIG_SYSCTL && CONFIG_NF_CONNTRACK_PROC_COMPAT */
 305
 306 /* Fast function for those who don't want to parse /proc (and I don't
 307    blame them). */
 308 /* Reversing the socket's dst/src point of view gives us the reply
 309    mapping. */
 310 static int
 311 getorigdst(struct sock *sk, int optval, void __user *user, int *len)
 312 {
 313         struct inet_sock *inet = inet_sk(sk);
 314         struct nf_conntrack_tuple_hash *h;
 315         struct nf_conntrack_tuple tuple;
 316
 317         NF_CT_TUPLE_U_BLANK(&tuple);
 318         tuple.src.u3.ip = inet->rcv_saddr;
 319         tuple.src.u.tcp.port = inet->sport;
 320         tuple.dst.u3.ip = inet->daddr;
 321         tuple.dst.u.tcp.port = inet->dport;
 322         tuple.src.l3num = PF_INET;
 323         tuple.dst.protonum = IPPROTO_TCP;
 324
 325         /* We only do TCP at the moment: is there a better way? */
 326         if (strcmp(sk->sk_prot->name, "TCP")) {
 327                 DEBUGP("SO_ORIGINAL_DST: Not a TCP socket\n");
 328                 return -ENOPROTOOPT;
 329         }
 330
 331         if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
 332                 DEBUGP("SO_ORIGINAL_DST: len %u not %u\n",
 333                        *len, sizeof(struct sockaddr_in));
 334                 return -EINVAL;
 335         }
 336
 337         h = nf_conntrack_find_get(&tuple);
 338         if (h) {
 339                 struct sockaddr_in sin;
 340                 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
 341
 342                 sin.sin_family = AF_INET;
 343                 sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 344                         .tuple.dst.u.tcp.port;
 345                 sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 346                         .tuple.dst.u3.ip;
 347                 memset(sin.sin_zero, 0, sizeof(sin.sin_zero));
 348
 349                 DEBUGP("SO_ORIGINAL_DST: %u.%u.%u.%u %u\n",
 350                        NIPQUAD(sin.sin_addr.s_addr), ntohs(sin.sin_port));
 351                 nf_ct_put(ct);
 352                 if (copy_to_user(user, &sin, sizeof(sin)) != 0)
 353                         return -EFAULT;
 354                 else
 355                         return 0;
 356         }
 357         DEBUGP("SO_ORIGINAL_DST: Can't find %u.%u.%u.%u/%u-%u.%u.%u.%u/%u.\n",
 358                NIPQUAD(tuple.src.u3.ip), ntohs(tuple.src.u.tcp.port),
 359                NIPQUAD(tuple.dst.u3.ip), ntohs(tuple.dst.u.tcp.port));
 360         return -ENOENT;
 361 }
 362
 363 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 364
 365 #include <linux/netfilter/nfnetlink.h>
 366 #include <linux/netfilter/nfnetlink_conntrack.h>
 367
 368 static int ipv4_tuple_to_nfattr(struct sk_buff *skb,
 369                                 const struct nf_conntrack_tuple *tuple)
 370 {
 371         NFA_PUT(skb, CTA_IP_V4_SRC, sizeof(u_int32_t),
 372                 &tuple->src.u3.ip);
 373         NFA_PUT(skb, CTA_IP_V4_DST, sizeof(u_int32_t),
 374                 &tuple->dst.u3.ip);
 375         return 0;
 376
 377 nfattr_failure:
 378         return -1;
 379 }
 380
 381 static const size_t cta_min_ip[CTA_IP_MAX] = {
 382         [CTA_IP_V4_SRC-1]       = sizeof(u_int32_t),
 383         [CTA_IP_V4_DST-1]       = sizeof(u_int32_t),
 384 };
 385
 386 static int ipv4_nfattr_to_tuple(struct nfattr *tb[],
 387                                 struct nf_conntrack_tuple *t)
 388 {
 389         if (!tb[CTA_IP_V4_SRC-1] || !tb[CTA_IP_V4_DST-1])
 390                 return -EINVAL;
 391
 392         if (nfattr_bad_size(tb, CTA_IP_MAX, cta_min_ip))
 393                 return -EINVAL;
 394
 395         t->src.u3.ip = *(__be32 *)NFA_DATA(tb[CTA_IP_V4_SRC-1]);
 396         t->dst.u3.ip = *(__be32 *)NFA_DATA(tb[CTA_IP_V4_DST-1]);
 397
 398         return 0;
 399 }
 400 #endif
 401
 402 static struct nf_sockopt_ops so_getorigdst = {
 403         .pf             = PF_INET,
 404         .get_optmin     = SO_ORIGINAL_DST,
 405         .get_optmax     = SO_ORIGINAL_DST+1,
 406         .get            = &getorigdst,
 407 };
 408
 409 struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 = {
 410         .l3proto         = PF_INET,
 411         .name            = "ipv4",
 412         .pkt_to_tuple    = ipv4_pkt_to_tuple,
 413         .invert_tuple    = ipv4_invert_tuple,
 414         .print_tuple     = ipv4_print_tuple,
 415         .print_conntrack = ipv4_print_conntrack,
 416         .prepare         = ipv4_prepare,
 417 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 418         .tuple_to_nfattr = ipv4_tuple_to_nfattr,
 419         .nfattr_to_tuple = ipv4_nfattr_to_tuple,
 420 #endif
 421 #if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 422         .ctl_table_path  = nf_net_ipv4_netfilter_sysctl_path,
 423         .ctl_table       = ip_ct_sysctl_table,
 424 #endif
 425         .me              = THIS_MODULE,
 426 };
 427
 428 MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET));
 429 MODULE_ALIAS("ip_conntrack");
 430 MODULE_LICENSE("GPL");
 431
 432 static int __init nf_conntrack_l3proto_ipv4_init(void)
 433 {
 434         int ret = 0;
 435
 436         need_conntrack();
 437
 438         ret = nf_register_sockopt(&so_getorigdst);
 439         if (ret < 0) {
 440                 printk(KERN_ERR "Unable to register netfilter socket option\n");
 441                 return ret;
 442         }
 443
 444         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_tcp4);
 445         if (ret < 0) {
 446                 printk("nf_conntrack_ipv4: can't register tcp.\n");
 447                 goto cleanup_sockopt;
 448         }
 449
 450         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_udp4);
 451         if (ret < 0) {
 452                 printk("nf_conntrack_ipv4: can't register udp.\n");
 453                 goto cleanup_tcp;
 454         }
 455
 456         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_icmp);
 457         if (ret < 0) {
 458                 printk("nf_conntrack_ipv4: can't register icmp.\n");
 459                 goto cleanup_udp;
 460         }
 461
 462         ret = nf_conntrack_l3proto_register(&nf_conntrack_l3proto_ipv4);
 463         if (ret < 0) {
 464                 printk("nf_conntrack_ipv4: can't register ipv4\n");
 465                 goto cleanup_icmp;
 466         }
 467
 468         ret = nf_register_hooks(ipv4_conntrack_ops,
 469                                 ARRAY_SIZE(ipv4_conntrack_ops));
 470         if (ret < 0) {
 471                 printk("nf_conntrack_ipv4: can't register hooks.\n");
 472                 goto cleanup_ipv4;
 473         }
 474 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 475         ret = nf_conntrack_ipv4_compat_init();
 476         if (ret < 0)
 477                 goto cleanup_hooks;
 478 #endif
 479         return ret;
 480 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 481  cleanup_hooks:
 482         nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
 483 #endif
 484  cleanup_ipv4:
 485         nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 486  cleanup_icmp:
 487         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_icmp);
 488  cleanup_udp:
 489         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_udp4);
 490  cleanup_tcp:
 491         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_tcp4);
 492  cleanup_sockopt:
 493         nf_unregister_sockopt(&so_getorigdst);
 494         return ret;
 495 }
 496
 497 static void __exit nf_conntrack_l3proto_ipv4_fini(void)
 498 {
 499         synchronize_net();
 500 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 501         nf_conntrack_ipv4_compat_fini();
 502 #endif
 503         nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
 504         nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 505         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_icmp);
 506         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_udp4);
 507         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_tcp4);
 508         nf_unregister_sockopt(&so_getorigdst);
 509 }
 510
 511 module_init(nf_conntrack_l3proto_ipv4_init);
 512 module_exit(nf_conntrack_l3proto_ipv4_fini);