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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 static int ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
  28                              struct nf_conntrack_tuple *tuple)
  29 {
  30         __be32 _addrs[2], *ap;
  31         ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
  32                                 sizeof(u_int32_t) * 2, _addrs);
  33         if (ap == NULL)
  34                 return 0;
  35
  36         tuple->src.u3.ip = ap[0];
  37         tuple->dst.u3.ip = ap[1];
  38
  39         return 1;
  40 }
  41
  42 static int ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
  43                            const struct nf_conntrack_tuple *orig)
  44 {
  45         tuple->src.u3.ip = orig->dst.u3.ip;
  46         tuple->dst.u3.ip = orig->src.u3.ip;
  47
  48         return 1;
  49 }
  50
  51 static int ipv4_print_tuple(struct seq_file *s,
  52                             const struct nf_conntrack_tuple *tuple)
  53 {
  54         return seq_printf(s, "src=%u.%u.%u.%u dst=%u.%u.%u.%u ",
  55                           NIPQUAD(tuple->src.u3.ip),
  56                           NIPQUAD(tuple->dst.u3.ip));
  57 }
  58
  59 static int ipv4_print_conntrack(struct seq_file *s,
  60                                 const struct nf_conn *conntrack)
  61 {
  62         return 0;
  63 }
  64
  65 /* Returns new sk_buff, or NULL */
  66 static struct sk_buff *
  67 nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
  68 {
  69         skb_orphan(skb);
  70
  71         local_bh_disable();
  72         skb = ip_defrag(skb, user);
  73         local_bh_enable();
  74
  75         if (skb)
  76                 ip_send_check(ip_hdr(skb));
  77
  78         return skb;
  79 }
  80
  81 static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
  82                             unsigned int *dataoff, u_int8_t *protonum)
  83 {
  84         struct iphdr _iph, *iph;
  85
  86         iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  87         if (iph == NULL)
  88                 return -NF_DROP;
  89
  90         /* Conntrack defragments packets, we might still see fragments
  91          * inside ICMP packets though. */
  92         if (iph->frag_off & htons(IP_OFFSET))
  93                 return -NF_DROP;
  94
  95         *dataoff = nhoff + (iph->ihl << 2);
  96         *protonum = iph->protocol;
  97
  98         return NF_ACCEPT;
  99 }
 100
 101 static unsigned int ipv4_confirm(unsigned int hooknum,
 102                                  struct sk_buff **pskb,
 103                                  const struct net_device *in,
 104                                  const struct net_device *out,
 105                                  int (*okfn)(struct sk_buff *))
 106 {
 107         /* We've seen it coming out the other side: confirm it */
 108         return nf_conntrack_confirm(pskb);
 109 }
 110
 111 static unsigned int ipv4_conntrack_help(unsigned int hooknum,
 112                                       struct sk_buff **pskb,
 113                                       const struct net_device *in,
 114                                       const struct net_device *out,
 115                                       int (*okfn)(struct sk_buff *))
 116 {
 117         struct nf_conn *ct;
 118         enum ip_conntrack_info ctinfo;
 119         struct nf_conn_help *help;
 120         struct nf_conntrack_helper *helper;
 121
 122         /* This is where we call the helper: as the packet goes out. */
 123         ct = nf_ct_get(*pskb, &ctinfo);
 124         if (!ct || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY)
 125                 return NF_ACCEPT;
 126
 127         help = nfct_help(ct);
 128         if (!help)
 129                 return NF_ACCEPT;
 130         /* rcu_read_lock()ed by nf_hook_slow */
 131         helper = rcu_dereference(help->helper);
 132         if (!helper)
 133                 return NF_ACCEPT;
 134         return helper->help(pskb, skb_network_offset(*pskb) + ip_hdrlen(*pskb),
 135                             ct, ctinfo);
 136 }
 137
 138 static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,
 139                                           struct sk_buff **pskb,
 140                                           const struct net_device *in,
 141                                           const struct net_device *out,
 142                                           int (*okfn)(struct sk_buff *))
 143 {
 144         /* Previously seen (loopback)?  Ignore.  Do this before
 145            fragment check. */
 146         if ((*pskb)->nfct)
 147                 return NF_ACCEPT;
 148
 149         /* Gather fragments. */
 150         if (ip_hdr(*pskb)->frag_off & htons(IP_MF | IP_OFFSET)) {
 151                 *pskb = nf_ct_ipv4_gather_frags(*pskb,
 152                                                 hooknum == NF_IP_PRE_ROUTING ?
 153                                                 IP_DEFRAG_CONNTRACK_IN :
 154                                                 IP_DEFRAG_CONNTRACK_OUT);
 155                 if (!*pskb)
 156                         return NF_STOLEN;
 157         }
 158         return NF_ACCEPT;
 159 }
 160
 161 static unsigned int ipv4_conntrack_in(unsigned int hooknum,
 162                                       struct sk_buff **pskb,
 163                                       const struct net_device *in,
 164                                       const struct net_device *out,
 165                                       int (*okfn)(struct sk_buff *))
 166 {
 167         return nf_conntrack_in(PF_INET, hooknum, pskb);
 168 }
 169
 170 static unsigned int ipv4_conntrack_local(unsigned int hooknum,
 171                                          struct sk_buff **pskb,
 172                                          const struct net_device *in,
 173                                          const struct net_device *out,
 174                                          int (*okfn)(struct sk_buff *))
 175 {
 176         /* root is playing with raw sockets. */
 177         if ((*pskb)->len < sizeof(struct iphdr)
 178             || ip_hdrlen(*pskb) < sizeof(struct iphdr)) {
 179                 if (net_ratelimit())
 180                         printk("ipt_hook: happy cracking.\n");
 181                 return NF_ACCEPT;
 182         }
 183         return nf_conntrack_in(PF_INET, hooknum, pskb);
 184 }
 185
 186 /* Connection tracking may drop packets, but never alters them, so
 187    make it the first hook. */
 188 static struct nf_hook_ops ipv4_conntrack_ops[] = {
 189         {
 190                 .hook           = ipv4_conntrack_defrag,
 191                 .owner          = THIS_MODULE,
 192                 .pf             = PF_INET,
 193                 .hooknum        = NF_IP_PRE_ROUTING,
 194                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 195         },
 196         {
 197                 .hook           = ipv4_conntrack_in,
 198                 .owner          = THIS_MODULE,
 199                 .pf             = PF_INET,
 200                 .hooknum        = NF_IP_PRE_ROUTING,
 201                 .priority       = NF_IP_PRI_CONNTRACK,
 202         },
 203         {
 204                 .hook           = ipv4_conntrack_defrag,
 205                 .owner          = THIS_MODULE,
 206                 .pf             = PF_INET,
 207                 .hooknum        = NF_IP_LOCAL_OUT,
 208                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 209         },
 210         {
 211                 .hook           = ipv4_conntrack_local,
 212                 .owner          = THIS_MODULE,
 213                 .pf             = PF_INET,
 214                 .hooknum        = NF_IP_LOCAL_OUT,
 215                 .priority       = NF_IP_PRI_CONNTRACK,
 216         },
 217         {
 218                 .hook           = ipv4_conntrack_help,
 219                 .owner          = THIS_MODULE,
 220                 .pf             = PF_INET,
 221                 .hooknum        = NF_IP_POST_ROUTING,
 222                 .priority       = NF_IP_PRI_CONNTRACK_HELPER,
 223         },
 224         {
 225                 .hook           = ipv4_conntrack_help,
 226                 .owner          = THIS_MODULE,
 227                 .pf             = PF_INET,
 228                 .hooknum        = NF_IP_LOCAL_IN,
 229                 .priority       = NF_IP_PRI_CONNTRACK_HELPER,
 230         },
 231         {
 232                 .hook           = ipv4_confirm,
 233                 .owner          = THIS_MODULE,
 234                 .pf             = PF_INET,
 235                 .hooknum        = NF_IP_POST_ROUTING,
 236                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 237         },
 238         {
 239                 .hook           = ipv4_confirm,
 240                 .owner          = THIS_MODULE,
 241                 .pf             = PF_INET,
 242                 .hooknum        = NF_IP_LOCAL_IN,
 243                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 244         },
 245 };
 246
 247 #if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 248 static int log_invalid_proto_min = 0;
 249 static int log_invalid_proto_max = 255;
 250
 251 static ctl_table ip_ct_sysctl_table[] = {
 252         {
 253                 .ctl_name       = NET_IPV4_NF_CONNTRACK_MAX,
 254                 .procname       = "ip_conntrack_max",
 255                 .data           = &nf_conntrack_max,
 256                 .maxlen         = sizeof(int),
 257                 .mode           = 0644,
 258                 .proc_handler   = &proc_dointvec,
 259         },
 260         {
 261                 .ctl_name       = NET_IPV4_NF_CONNTRACK_COUNT,
 262                 .procname       = "ip_conntrack_count",
 263                 .data           = &nf_conntrack_count,
 264                 .maxlen         = sizeof(int),
 265                 .mode           = 0444,
 266                 .proc_handler   = &proc_dointvec,
 267         },
 268         {
 269                 .ctl_name       = NET_IPV4_NF_CONNTRACK_BUCKETS,
 270                 .procname       = "ip_conntrack_buckets",
 271                 .data           = &nf_conntrack_htable_size,
 272                 .maxlen         = sizeof(unsigned int),
 273                 .mode           = 0444,
 274                 .proc_handler   = &proc_dointvec,
 275         },
 276         {
 277                 .ctl_name       = NET_IPV4_NF_CONNTRACK_CHECKSUM,
 278                 .procname       = "ip_conntrack_checksum",
 279                 .data           = &nf_conntrack_checksum,
 280                 .maxlen         = sizeof(int),
 281                 .mode           = 0644,
 282                 .proc_handler   = &proc_dointvec,
 283         },
 284         {
 285                 .ctl_name       = NET_IPV4_NF_CONNTRACK_LOG_INVALID,
 286                 .procname       = "ip_conntrack_log_invalid",
 287                 .data           = &nf_ct_log_invalid,
 288                 .maxlen         = sizeof(unsigned int),
 289                 .mode           = 0644,
 290                 .proc_handler   = &proc_dointvec_minmax,
 291                 .strategy       = &sysctl_intvec,
 292                 .extra1         = &log_invalid_proto_min,
 293                 .extra2         = &log_invalid_proto_max,
 294         },
 295         {
 296                 .ctl_name       = 0
 297         }
 298 };
 299 #endif /* CONFIG_SYSCTL && CONFIG_NF_CONNTRACK_PROC_COMPAT */
 300
 301 /* Fast function for those who don't want to parse /proc (and I don't
 302    blame them). */
 303 /* Reversing the socket's dst/src point of view gives us the reply
 304    mapping. */
 305 static int
 306 getorigdst(struct sock *sk, int optval, void __user *user, int *len)
 307 {
 308         struct inet_sock *inet = inet_sk(sk);
 309         struct nf_conntrack_tuple_hash *h;
 310         struct nf_conntrack_tuple tuple;
 311
 312         NF_CT_TUPLE_U_BLANK(&tuple);
 313         tuple.src.u3.ip = inet->rcv_saddr;
 314         tuple.src.u.tcp.port = inet->sport;
 315         tuple.dst.u3.ip = inet->daddr;
 316         tuple.dst.u.tcp.port = inet->dport;
 317         tuple.src.l3num = PF_INET;
 318         tuple.dst.protonum = IPPROTO_TCP;
 319
 320         /* We only do TCP at the moment: is there a better way? */
 321         if (strcmp(sk->sk_prot->name, "TCP")) {
 322                 pr_debug("SO_ORIGINAL_DST: Not a TCP socket\n");
 323                 return -ENOPROTOOPT;
 324         }
 325
 326         if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
 327                 pr_debug("SO_ORIGINAL_DST: len %d not %Zu\n",
 328                          *len, sizeof(struct sockaddr_in));
 329                 return -EINVAL;
 330         }
 331
 332         h = nf_conntrack_find_get(&tuple);
 333         if (h) {
 334                 struct sockaddr_in sin;
 335                 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
 336
 337                 sin.sin_family = AF_INET;
 338                 sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 339                         .tuple.dst.u.tcp.port;
 340                 sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 341                         .tuple.dst.u3.ip;
 342                 memset(sin.sin_zero, 0, sizeof(sin.sin_zero));
 343
 344                 pr_debug("SO_ORIGINAL_DST: %u.%u.%u.%u %u\n",
 345                          NIPQUAD(sin.sin_addr.s_addr), ntohs(sin.sin_port));
 346                 nf_ct_put(ct);
 347                 if (copy_to_user(user, &sin, sizeof(sin)) != 0)
 348                         return -EFAULT;
 349                 else
 350                         return 0;
 351         }
 352         pr_debug("SO_ORIGINAL_DST: Can't find %u.%u.%u.%u/%u-%u.%u.%u.%u/%u.\n",
 353                  NIPQUAD(tuple.src.u3.ip), ntohs(tuple.src.u.tcp.port),
 354                  NIPQUAD(tuple.dst.u3.ip), ntohs(tuple.dst.u.tcp.port));
 355         return -ENOENT;
 356 }
 357
 358 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 359
 360 #include <linux/netfilter/nfnetlink.h>
 361 #include <linux/netfilter/nfnetlink_conntrack.h>
 362
 363 static int ipv4_tuple_to_nlattr(struct sk_buff *skb,
 364                                 const struct nf_conntrack_tuple *tuple)
 365 {
 366         NLA_PUT(skb, CTA_IP_V4_SRC, sizeof(u_int32_t),
 367                 &tuple->src.u3.ip);
 368         NLA_PUT(skb, CTA_IP_V4_DST, sizeof(u_int32_t),
 369                 &tuple->dst.u3.ip);
 370         return 0;
 371
 372 nla_put_failure:
 373         return -1;
 374 }
 375
 376 static const size_t cta_min_ip[CTA_IP_MAX+1] = {
 377         [CTA_IP_V4_SRC] = sizeof(u_int32_t),
 378         [CTA_IP_V4_DST] = sizeof(u_int32_t),
 379 };
 380
 381 static int ipv4_nlattr_to_tuple(struct nlattr *tb[],
 382                                 struct nf_conntrack_tuple *t)
 383 {
 384         if (!tb[CTA_IP_V4_SRC] || !tb[CTA_IP_V4_DST])
 385                 return -EINVAL;
 386
 387         if (nlattr_bad_size(tb, CTA_IP_MAX, cta_min_ip))
 388                 return -EINVAL;
 389
 390         t->src.u3.ip = *(__be32 *)nla_data(tb[CTA_IP_V4_SRC]);
 391         t->dst.u3.ip = *(__be32 *)nla_data(tb[CTA_IP_V4_DST]);
 392
 393         return 0;
 394 }
 395 #endif
 396
 397 static struct nf_sockopt_ops so_getorigdst = {
 398         .pf             = PF_INET,
 399         .get_optmin     = SO_ORIGINAL_DST,
 400         .get_optmax     = SO_ORIGINAL_DST+1,
 401         .get            = &getorigdst,
 402         .owner          = THIS_MODULE,
 403 };
 404
 405 struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 __read_mostly = {
 406         .l3proto         = PF_INET,
 407         .name            = "ipv4",
 408         .pkt_to_tuple    = ipv4_pkt_to_tuple,
 409         .invert_tuple    = ipv4_invert_tuple,
 410         .print_tuple     = ipv4_print_tuple,
 411         .print_conntrack = ipv4_print_conntrack,
 412         .get_l4proto     = ipv4_get_l4proto,
 413 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 414         .tuple_to_nlattr = ipv4_tuple_to_nlattr,
 415         .nlattr_to_tuple = ipv4_nlattr_to_tuple,
 416 #endif
 417 #if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 418         .ctl_table_path  = nf_net_ipv4_netfilter_sysctl_path,
 419         .ctl_table       = ip_ct_sysctl_table,
 420 #endif
 421         .me              = THIS_MODULE,
 422 };
 423
 424 MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET));
 425 MODULE_ALIAS("ip_conntrack");
 426 MODULE_LICENSE("GPL");
 427
 428 static int __init nf_conntrack_l3proto_ipv4_init(void)
 429 {
 430         int ret = 0;
 431
 432         need_conntrack();
 433
 434         ret = nf_register_sockopt(&so_getorigdst);
 435         if (ret < 0) {
 436                 printk(KERN_ERR "Unable to register netfilter socket option\n");
 437                 return ret;
 438         }
 439
 440         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_tcp4);
 441         if (ret < 0) {
 442                 printk("nf_conntrack_ipv4: can't register tcp.\n");
 443                 goto cleanup_sockopt;
 444         }
 445
 446         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_udp4);
 447         if (ret < 0) {
 448                 printk("nf_conntrack_ipv4: can't register udp.\n");
 449                 goto cleanup_tcp;
 450         }
 451
 452         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_icmp);
 453         if (ret < 0) {
 454                 printk("nf_conntrack_ipv4: can't register icmp.\n");
 455                 goto cleanup_udp;
 456         }
 457
 458         ret = nf_conntrack_l3proto_register(&nf_conntrack_l3proto_ipv4);
 459         if (ret < 0) {
 460                 printk("nf_conntrack_ipv4: can't register ipv4\n");
 461                 goto cleanup_icmp;
 462         }
 463
 464         ret = nf_register_hooks(ipv4_conntrack_ops,
 465                                 ARRAY_SIZE(ipv4_conntrack_ops));
 466         if (ret < 0) {
 467                 printk("nf_conntrack_ipv4: can't register hooks.\n");
 468                 goto cleanup_ipv4;
 469         }
 470 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 471         ret = nf_conntrack_ipv4_compat_init();
 472         if (ret < 0)
 473                 goto cleanup_hooks;
 474 #endif
 475         return ret;
 476 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 477  cleanup_hooks:
 478         nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
 479 #endif
 480  cleanup_ipv4:
 481         nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 482  cleanup_icmp:
 483         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_icmp);
 484  cleanup_udp:
 485         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_udp4);
 486  cleanup_tcp:
 487         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_tcp4);
 488  cleanup_sockopt:
 489         nf_unregister_sockopt(&so_getorigdst);
 490         return ret;
 491 }
 492
 493 static void __exit nf_conntrack_l3proto_ipv4_fini(void)
 494 {
 495         synchronize_net();
 496 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 497         nf_conntrack_ipv4_compat_fini();
 498 #endif
 499         nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
 500         nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 501         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_icmp);
 502         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_udp4);
 503         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_tcp4);
 504         nf_unregister_sockopt(&so_getorigdst);
 505 }
 506
 507 module_init(nf_conntrack_l3proto_ipv4_init);
 508 module_exit(nf_conntrack_l3proto_ipv4_fini);
 509
 510 void need_ipv4_conntrack(void)
 511 {
 512         return;
 513 }
 514 EXPORT_SYMBOL_GPL(need_ipv4_conntrack);