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   1
   2 /* (C) 1999-2001 Paul `Rusty' Russell
   3  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #include <linux/types.h>
  11 #include <linux/ip.h>
  12 #include <linux/netfilter.h>
  13 #include <linux/module.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/icmp.h>
  16 #include <linux/sysctl.h>
  17 #include <net/route.h>
  18 #include <net/ip.h>
  19
  20 #include <linux/netfilter_ipv4.h>
  21 #include <net/netfilter/nf_conntrack.h>
  22 #include <net/netfilter/nf_conntrack_helper.h>
  23 #include <net/netfilter/nf_conntrack_l4proto.h>
  24 #include <net/netfilter/nf_conntrack_l3proto.h>
  25 #include <net/netfilter/nf_conntrack_core.h>
  26 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
  27 #include <net/netfilter/nf_nat_helper.h>
  28 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  29 #include <net/netfilter/nf_log.h>
  30
  31 int (*nf_nat_seq_adjust_hook)(struct sk_buff *skb,
  32                               struct nf_conn *ct,
  33                               enum ip_conntrack_info ctinfo);
  34 EXPORT_SYMBOL_GPL(nf_nat_seq_adjust_hook);
  35
  36 static bool ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
  37                               struct nf_conntrack_tuple *tuple)
  38 {
  39         const __be32 *ap;
  40         __be32 _addrs[2];
  41         ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
  42                                 sizeof(u_int32_t) * 2, _addrs);
  43         if (ap == NULL)
  44                 return false;
  45
  46         tuple->src.u3.ip = ap[0];
  47         tuple->dst.u3.ip = ap[1];
  48
  49         return true;
  50 }
  51
  52 static bool ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
  53                               const struct nf_conntrack_tuple *orig)
  54 {
  55         tuple->src.u3.ip = orig->dst.u3.ip;
  56         tuple->dst.u3.ip = orig->src.u3.ip;
  57
  58         return true;
  59 }
  60
  61 static int ipv4_print_tuple(struct seq_file *s,
  62                             const struct nf_conntrack_tuple *tuple)
  63 {
  64         return seq_printf(s, "src=%pI4 dst=%pI4 ",
  65                           &tuple->src.u3.ip, &tuple->dst.u3.ip);
  66 }
  67
  68 static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
  69                             unsigned int *dataoff, u_int8_t *protonum)
  70 {
  71         const struct iphdr *iph;
  72         struct iphdr _iph;
  73
  74         iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  75         if (iph == NULL)
  76                 return -NF_DROP;
  77
  78         /* Conntrack defragments packets, we might still see fragments
  79          * inside ICMP packets though. */
  80         if (iph->frag_off & htons(IP_OFFSET))
  81                 return -NF_DROP;
  82
  83         *dataoff = nhoff + (iph->ihl << 2);
  84         *protonum = iph->protocol;
  85
  86         return NF_ACCEPT;
  87 }
  88
  89 static unsigned int ipv4_confirm(unsigned int hooknum,
  90                                  struct sk_buff *skb,
  91                                  const struct net_device *in,
  92                                  const struct net_device *out,
  93                                  int (*okfn)(struct sk_buff *))
  94 {
  95         struct nf_conn *ct;
  96         enum ip_conntrack_info ctinfo;
  97         const struct nf_conn_help *help;
  98         const struct nf_conntrack_helper *helper;
  99         unsigned int ret;
 100
 101         /* This is where we call the helper: as the packet goes out. */
 102         ct = nf_ct_get(skb, &ctinfo);
 103         if (!ct || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY)
 104                 goto out;
 105
 106         help = nfct_help(ct);
 107         if (!help)
 108                 goto out;
 109
 110         /* rcu_read_lock()ed by nf_hook_slow */
 111         helper = rcu_dereference(help->helper);
 112         if (!helper)
 113                 goto out;
 114
 115         ret = helper->help(skb, skb_network_offset(skb) + ip_hdrlen(skb),
 116                            ct, ctinfo);
 117         if (ret != NF_ACCEPT) {
 118                 nf_log_packet(NFPROTO_IPV4, hooknum, skb, in, out, NULL,
 119                               "nf_ct_%s: dropping packet", helper->name);
 120                 return ret;
 121         }
 122
 123         if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) {
 124                 typeof(nf_nat_seq_adjust_hook) seq_adjust;
 125
 126                 seq_adjust = rcu_dereference(nf_nat_seq_adjust_hook);
 127                 if (!seq_adjust || !seq_adjust(skb, ct, ctinfo)) {
 128                         NF_CT_STAT_INC_ATOMIC(nf_ct_net(ct), drop);
 129                         return NF_DROP;
 130                 }
 131         }
 132 out:
 133         /* We've seen it coming out the other side: confirm it */
 134         return nf_conntrack_confirm(skb);
 135 }
 136
 137 static unsigned int ipv4_conntrack_in(unsigned int hooknum,
 138                                       struct sk_buff *skb,
 139                                       const struct net_device *in,
 140                                       const struct net_device *out,
 141                                       int (*okfn)(struct sk_buff *))
 142 {
 143         return nf_conntrack_in(dev_net(in), PF_INET, hooknum, skb);
 144 }
 145
 146 static unsigned int ipv4_conntrack_local(unsigned int hooknum,
 147                                          struct sk_buff *skb,
 148                                          const struct net_device *in,
 149                                          const struct net_device *out,
 150                                          int (*okfn)(struct sk_buff *))
 151 {
 152         /* root is playing with raw sockets. */
 153         if (skb->len < sizeof(struct iphdr) ||
 154             ip_hdrlen(skb) < sizeof(struct iphdr))
 155                 return NF_ACCEPT;
 156         return nf_conntrack_in(dev_net(out), PF_INET, hooknum, skb);
 157 }
 158
 159 /* Connection tracking may drop packets, but never alters them, so
 160    make it the first hook. */
 161 static struct nf_hook_ops ipv4_conntrack_ops[] __read_mostly = {
 162         {
 163                 .hook           = ipv4_conntrack_in,
 164                 .owner          = THIS_MODULE,
 165                 .pf             = NFPROTO_IPV4,
 166                 .hooknum        = NF_INET_PRE_ROUTING,
 167                 .priority       = NF_IP_PRI_CONNTRACK,
 168         },
 169         {
 170                 .hook           = ipv4_conntrack_local,
 171                 .owner          = THIS_MODULE,
 172                 .pf             = NFPROTO_IPV4,
 173                 .hooknum        = NF_INET_LOCAL_OUT,
 174                 .priority       = NF_IP_PRI_CONNTRACK,
 175         },
 176         {
 177                 .hook           = ipv4_confirm,
 178                 .owner          = THIS_MODULE,
 179                 .pf             = NFPROTO_IPV4,
 180                 .hooknum        = NF_INET_POST_ROUTING,
 181                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 182         },
 183         {
 184                 .hook           = ipv4_confirm,
 185                 .owner          = THIS_MODULE,
 186                 .pf             = NFPROTO_IPV4,
 187                 .hooknum        = NF_INET_LOCAL_IN,
 188                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 189         },
 190 };
 191
 192 #if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 193 static int log_invalid_proto_min = 0;
 194 static int log_invalid_proto_max = 255;
 195
 196 static ctl_table ip_ct_sysctl_table[] = {
 197         {
 198                 .procname       = "ip_conntrack_max",
 199                 .data           = &nf_conntrack_max,
 200                 .maxlen         = sizeof(int),
 201                 .mode           = 0644,
 202                 .proc_handler   = proc_dointvec,
 203         },
 204         {
 205                 .procname       = "ip_conntrack_count",
 206                 .data           = &init_net.ct.count,
 207                 .maxlen         = sizeof(int),
 208                 .mode           = 0444,
 209                 .proc_handler   = proc_dointvec,
 210         },
 211         {
 212                 .procname       = "ip_conntrack_buckets",
 213                 .data           = &nf_conntrack_htable_size,
 214                 .maxlen         = sizeof(unsigned int),
 215                 .mode           = 0444,
 216                 .proc_handler   = proc_dointvec,
 217         },
 218         {
 219                 .procname       = "ip_conntrack_checksum",
 220                 .data           = &init_net.ct.sysctl_checksum,
 221                 .maxlen         = sizeof(int),
 222                 .mode           = 0644,
 223                 .proc_handler   = proc_dointvec,
 224         },
 225         {
 226                 .procname       = "ip_conntrack_log_invalid",
 227                 .data           = &init_net.ct.sysctl_log_invalid,
 228                 .maxlen         = sizeof(unsigned int),
 229                 .mode           = 0644,
 230                 .proc_handler   = proc_dointvec_minmax,
 231                 .extra1         = &log_invalid_proto_min,
 232                 .extra2         = &log_invalid_proto_max,
 233         },
 234         { }
 235 };
 236 #endif /* CONFIG_SYSCTL && CONFIG_NF_CONNTRACK_PROC_COMPAT */
 237
 238 /* Fast function for those who don't want to parse /proc (and I don't
 239    blame them). */
 240 /* Reversing the socket's dst/src point of view gives us the reply
 241    mapping. */
 242 static int
 243 getorigdst(struct sock *sk, int optval, void __user *user, int *len)
 244 {
 245         const struct inet_sock *inet = inet_sk(sk);
 246         const struct nf_conntrack_tuple_hash *h;
 247         struct nf_conntrack_tuple tuple;
 248
 249         memset(&tuple, 0, sizeof(tuple));
 250         tuple.src.u3.ip = inet->inet_rcv_saddr;
 251         tuple.src.u.tcp.port = inet->inet_sport;
 252         tuple.dst.u3.ip = inet->inet_daddr;
 253         tuple.dst.u.tcp.port = inet->inet_dport;
 254         tuple.src.l3num = PF_INET;
 255         tuple.dst.protonum = sk->sk_protocol;
 256
 257         /* We only do TCP and SCTP at the moment: is there a better way? */
 258         if (sk->sk_protocol != IPPROTO_TCP && sk->sk_protocol != IPPROTO_SCTP) {
 259                 pr_debug("SO_ORIGINAL_DST: Not a TCP/SCTP socket\n");
 260                 return -ENOPROTOOPT;
 261         }
 262
 263         if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
 264                 pr_debug("SO_ORIGINAL_DST: len %d not %Zu\n",
 265                          *len, sizeof(struct sockaddr_in));
 266                 return -EINVAL;
 267         }
 268
 269         h = nf_conntrack_find_get(sock_net(sk), &tuple);
 270         if (h) {
 271                 struct sockaddr_in sin;
 272                 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
 273
 274                 sin.sin_family = AF_INET;
 275                 sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 276                         .tuple.dst.u.tcp.port;
 277                 sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 278                         .tuple.dst.u3.ip;
 279                 memset(sin.sin_zero, 0, sizeof(sin.sin_zero));
 280
 281                 pr_debug("SO_ORIGINAL_DST: %pI4 %u\n",
 282                          &sin.sin_addr.s_addr, ntohs(sin.sin_port));
 283                 nf_ct_put(ct);
 284                 if (copy_to_user(user, &sin, sizeof(sin)) != 0)
 285                         return -EFAULT;
 286                 else
 287                         return 0;
 288         }
 289         pr_debug("SO_ORIGINAL_DST: Can't find %pI4/%u-%pI4/%u.\n",
 290                  &tuple.src.u3.ip, ntohs(tuple.src.u.tcp.port),
 291                  &tuple.dst.u3.ip, ntohs(tuple.dst.u.tcp.port));
 292         return -ENOENT;
 293 }
 294
 295 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 296
 297 #include <linux/netfilter/nfnetlink.h>
 298 #include <linux/netfilter/nfnetlink_conntrack.h>
 299
 300 static int ipv4_tuple_to_nlattr(struct sk_buff *skb,
 301                                 const struct nf_conntrack_tuple *tuple)
 302 {
 303         NLA_PUT_BE32(skb, CTA_IP_V4_SRC, tuple->src.u3.ip);
 304         NLA_PUT_BE32(skb, CTA_IP_V4_DST, tuple->dst.u3.ip);
 305         return 0;
 306
 307 nla_put_failure:
 308         return -1;
 309 }
 310
 311 static const struct nla_policy ipv4_nla_policy[CTA_IP_MAX+1] = {
 312         [CTA_IP_V4_SRC] = { .type = NLA_U32 },
 313         [CTA_IP_V4_DST] = { .type = NLA_U32 },
 314 };
 315
 316 static int ipv4_nlattr_to_tuple(struct nlattr *tb[],
 317                                 struct nf_conntrack_tuple *t)
 318 {
 319         if (!tb[CTA_IP_V4_SRC] || !tb[CTA_IP_V4_DST])
 320                 return -EINVAL;
 321
 322         t->src.u3.ip = nla_get_be32(tb[CTA_IP_V4_SRC]);
 323         t->dst.u3.ip = nla_get_be32(tb[CTA_IP_V4_DST]);
 324
 325         return 0;
 326 }
 327
 328 static int ipv4_nlattr_tuple_size(void)
 329 {
 330         return nla_policy_len(ipv4_nla_policy, CTA_IP_MAX + 1);
 331 }
 332 #endif
 333
 334 static struct nf_sockopt_ops so_getorigdst = {
 335         .pf             = PF_INET,
 336         .get_optmin     = SO_ORIGINAL_DST,
 337         .get_optmax     = SO_ORIGINAL_DST+1,
 338         .get            = &getorigdst,
 339         .owner          = THIS_MODULE,
 340 };
 341
 342 struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 __read_mostly = {
 343         .l3proto         = PF_INET,
 344         .name            = "ipv4",
 345         .pkt_to_tuple    = ipv4_pkt_to_tuple,
 346         .invert_tuple    = ipv4_invert_tuple,
 347         .print_tuple     = ipv4_print_tuple,
 348         .get_l4proto     = ipv4_get_l4proto,
 349 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 350         .tuple_to_nlattr = ipv4_tuple_to_nlattr,
 351         .nlattr_tuple_size = ipv4_nlattr_tuple_size,
 352         .nlattr_to_tuple = ipv4_nlattr_to_tuple,
 353         .nla_policy      = ipv4_nla_policy,
 354 #endif
 355 #if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 356         .ctl_table_path  = nf_net_ipv4_netfilter_sysctl_path,
 357         .ctl_table       = ip_ct_sysctl_table,
 358 #endif
 359         .me              = THIS_MODULE,
 360 };
 361
 362 module_param_call(hashsize, nf_conntrack_set_hashsize, param_get_uint,
 363                   &nf_conntrack_htable_size, 0600);
 364
 365 MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET));
 366 MODULE_ALIAS("ip_conntrack");
 367 MODULE_LICENSE("GPL");
 368
 369 static int __init nf_conntrack_l3proto_ipv4_init(void)
 370 {
 371         int ret = 0;
 372
 373         need_conntrack();
 374         nf_defrag_ipv4_enable();
 375
 376         ret = nf_register_sockopt(&so_getorigdst);
 377         if (ret < 0) {
 378                 printk(KERN_ERR "Unable to register netfilter socket option\n");
 379                 return ret;
 380         }
 381
 382         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_tcp4);
 383         if (ret < 0) {
 384                 printk("nf_conntrack_ipv4: can't register tcp.\n");
 385                 goto cleanup_sockopt;
 386         }
 387
 388         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_udp4);
 389         if (ret < 0) {
 390                 printk("nf_conntrack_ipv4: can't register udp.\n");
 391                 goto cleanup_tcp;
 392         }
 393
 394         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_icmp);
 395         if (ret < 0) {
 396                 printk("nf_conntrack_ipv4: can't register icmp.\n");
 397                 goto cleanup_udp;
 398         }
 399
 400         ret = nf_conntrack_l3proto_register(&nf_conntrack_l3proto_ipv4);
 401         if (ret < 0) {
 402                 printk("nf_conntrack_ipv4: can't register ipv4\n");
 403                 goto cleanup_icmp;
 404         }
 405
 406         ret = nf_register_hooks(ipv4_conntrack_ops,
 407                                 ARRAY_SIZE(ipv4_conntrack_ops));
 408         if (ret < 0) {
 409                 printk("nf_conntrack_ipv4: can't register hooks.\n");
 410                 goto cleanup_ipv4;
 411         }
 412 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 413         ret = nf_conntrack_ipv4_compat_init();
 414         if (ret < 0)
 415                 goto cleanup_hooks;
 416 #endif
 417         return ret;
 418 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 419  cleanup_hooks:
 420         nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
 421 #endif
 422  cleanup_ipv4:
 423         nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 424  cleanup_icmp:
 425         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_icmp);
 426  cleanup_udp:
 427         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_udp4);
 428  cleanup_tcp:
 429         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_tcp4);
 430  cleanup_sockopt:
 431         nf_unregister_sockopt(&so_getorigdst);
 432         return ret;
 433 }
 434
 435 static void __exit nf_conntrack_l3proto_ipv4_fini(void)
 436 {
 437         synchronize_net();
 438 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 439         nf_conntrack_ipv4_compat_fini();
 440 #endif
 441         nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
 442         nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 443         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_icmp);
 444         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_udp4);
 445         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_tcp4);
 446         nf_unregister_sockopt(&so_getorigdst);
 447 }
 448
 449 module_init(nf_conntrack_l3proto_ipv4_init);
 450 module_exit(nf_conntrack_l3proto_ipv4_fini);
 451
 452 void need_ipv4_conntrack(void)
 453 {
 454         return;
 455 }
 456 EXPORT_SYMBOL_GPL(need_ipv4_conntrack);