net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c

   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
  30 int (*nf_nat_seq_adjust_hook)(struct sk_buff *skb,
  31                               struct nf_conn *ct,
  32                               enum ip_conntrack_info ctinfo);
  33 EXPORT_SYMBOL_GPL(nf_nat_seq_adjust_hook);
  34
  35 static bool ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
  36                               struct nf_conntrack_tuple *tuple)
  37 {
  38         const __be32 *ap;
  39         __be32 _addrs[2];
  40         ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
  41                                 sizeof(u_int32_t) * 2, _addrs);
  42         if (ap == NULL)
  43                 return false;
  44
  45         tuple->src.u3.ip = ap[0];
  46         tuple->dst.u3.ip = ap[1];
  47
  48         return true;
  49 }
  50
  51 static bool ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
  52                               const struct nf_conntrack_tuple *orig)
  53 {
  54         tuple->src.u3.ip = orig->dst.u3.ip;
  55         tuple->dst.u3.ip = orig->src.u3.ip;
  56
  57         return true;
  58 }
  59
  60 static int ipv4_print_tuple(struct seq_file *s,
  61                             const struct nf_conntrack_tuple *tuple)
  62 {
  63         return seq_printf(s, "src=%pI4 dst=%pI4 ",
  64                           &tuple->src.u3.ip, &tuple->dst.u3.ip);
  65 }
  66
  67 static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
  68                             unsigned int *dataoff, u_int8_t *protonum)
  69 {
  70         const struct iphdr *iph;
  71         struct iphdr _iph;
  72
  73         iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  74         if (iph == NULL)
  75                 return -NF_DROP;
  76
  77         /* Conntrack defragments packets, we might still see fragments
  78          * inside ICMP packets though. */
  79         if (iph->frag_off & htons(IP_OFFSET))
  80                 return -NF_DROP;
  81
  82         *dataoff = nhoff + (iph->ihl << 2);
  83         *protonum = iph->protocol;
  84
  85         return NF_ACCEPT;
  86 }
  87
  88 static unsigned int ipv4_confirm(unsigned int hooknum,
  89                                  struct sk_buff *skb,
  90                                  const struct net_device *in,
  91                                  const struct net_device *out,
  92                                  int (*okfn)(struct sk_buff *))
  93 {
  94         struct nf_conn *ct;
  95         enum ip_conntrack_info ctinfo;
  96         const struct nf_conn_help *help;
  97         const struct nf_conntrack_helper *helper;
  98         unsigned int ret;
  99
 100         /* This is where we call the helper: as the packet goes out. */
 101         ct = nf_ct_get(skb, &ctinfo);
 102         if (!ct || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY)
 103                 goto out;
 104
 105         help = nfct_help(ct);
 106         if (!help)
 107                 goto out;
 108
 109         /* rcu_read_lock()ed by nf_hook_slow */
 110         helper = rcu_dereference(help->helper);
 111         if (!helper)
 112                 goto out;
 113
 114         ret = helper->help(skb, skb_network_offset(skb) + ip_hdrlen(skb),
 115                            ct, ctinfo);
 116         if (ret != NF_ACCEPT)
 117                 return ret;
 118
 119         if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) {
 120                 typeof(nf_nat_seq_adjust_hook) seq_adjust;
 121
 122                 seq_adjust = rcu_dereference(nf_nat_seq_adjust_hook);
 123                 if (!seq_adjust || !seq_adjust(skb, ct, ctinfo)) {
 124                         NF_CT_STAT_INC_ATOMIC(nf_ct_net(ct), drop);
 125                         return NF_DROP;
 126                 }
 127         }
 128 out:
 129         /* We've seen it coming out the other side: confirm it */
 130         return nf_conntrack_confirm(skb);
 131 }
 132
 133 static unsigned int ipv4_conntrack_in(unsigned int hooknum,
 134                                       struct sk_buff *skb,
 135                                       const struct net_device *in,
 136                                       const struct net_device *out,
 137                                       int (*okfn)(struct sk_buff *))
 138 {
 139         return nf_conntrack_in(dev_net(in), PF_INET, hooknum, skb);
 140 }
 141
 142 static unsigned int ipv4_conntrack_local(unsigned int hooknum,
 143                                          struct sk_buff *skb,
 144                                          const struct net_device *in,
 145                                          const struct net_device *out,
 146                                          int (*okfn)(struct sk_buff *))
 147 {
 148         /* root is playing with raw sockets. */
 149         if (skb->len < sizeof(struct iphdr) ||
 150             ip_hdrlen(skb) < sizeof(struct iphdr))
 151                 return NF_ACCEPT;
 152         return nf_conntrack_in(dev_net(out), PF_INET, hooknum, skb);
 153 }
 154
 155 /* Connection tracking may drop packets, but never alters them, so
 156    make it the first hook. */
 157 static struct nf_hook_ops ipv4_conntrack_ops[] __read_mostly = {
 158         {
 159                 .hook           = ipv4_conntrack_in,
 160                 .owner          = THIS_MODULE,
 161                 .pf             = PF_INET,
 162                 .hooknum        = NF_INET_PRE_ROUTING,
 163                 .priority       = NF_IP_PRI_CONNTRACK,
 164         },
 165         {
 166                 .hook           = ipv4_conntrack_local,
 167                 .owner          = THIS_MODULE,
 168                 .pf             = PF_INET,
 169                 .hooknum        = NF_INET_LOCAL_OUT,
 170                 .priority       = NF_IP_PRI_CONNTRACK,
 171         },
 172         {
 173                 .hook           = ipv4_confirm,
 174                 .owner          = THIS_MODULE,
 175                 .pf             = PF_INET,
 176                 .hooknum        = NF_INET_POST_ROUTING,
 177                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 178         },
 179         {
 180                 .hook           = ipv4_confirm,
 181                 .owner          = THIS_MODULE,
 182                 .pf             = PF_INET,
 183                 .hooknum        = NF_INET_LOCAL_IN,
 184                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 185         },
 186 };
 187
 188 #if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 189 static int log_invalid_proto_min = 0;
 190 static int log_invalid_proto_max = 255;
 191
 192 static ctl_table ip_ct_sysctl_table[] = {
 193         {
 194                 .ctl_name       = NET_IPV4_NF_CONNTRACK_MAX,
 195                 .procname       = "ip_conntrack_max",
 196                 .data           = &nf_conntrack_max,
 197                 .maxlen         = sizeof(int),
 198                 .mode           = 0644,
 199                 .proc_handler   = proc_dointvec,
 200         },
 201         {
 202                 .ctl_name       = NET_IPV4_NF_CONNTRACK_COUNT,
 203                 .procname       = "ip_conntrack_count",
 204                 .data           = &init_net.ct.count,
 205                 .maxlen         = sizeof(int),
 206                 .mode           = 0444,
 207                 .proc_handler   = proc_dointvec,
 208         },
 209         {
 210                 .ctl_name       = NET_IPV4_NF_CONNTRACK_BUCKETS,
 211                 .procname       = "ip_conntrack_buckets",
 212                 .data           = &nf_conntrack_htable_size,
 213                 .maxlen         = sizeof(unsigned int),
 214                 .mode           = 0444,
 215                 .proc_handler   = proc_dointvec,
 216         },
 217         {
 218                 .ctl_name       = NET_IPV4_NF_CONNTRACK_CHECKSUM,
 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                 .ctl_name       = NET_IPV4_NF_CONNTRACK_LOG_INVALID,
 227                 .procname       = "ip_conntrack_log_invalid",
 228                 .data           = &init_net.ct.sysctl_log_invalid,
 229                 .maxlen         = sizeof(unsigned int),
 230                 .mode           = 0644,
 231                 .proc_handler   = proc_dointvec_minmax,
 232                 .strategy       = sysctl_intvec,
 233                 .extra1         = &log_invalid_proto_min,
 234                 .extra2         = &log_invalid_proto_max,
 235         },
 236         {
 237                 .ctl_name       = 0
 238         }
 239 };
 240 #endif /* CONFIG_SYSCTL && CONFIG_NF_CONNTRACK_PROC_COMPAT */
 241
 242 /* Fast function for those who don't want to parse /proc (and I don't
 243    blame them). */
 244 /* Reversing the socket's dst/src point of view gives us the reply
 245    mapping. */
 246 static int
 247 getorigdst(struct sock *sk, int optval, void __user *user, int *len)
 248 {
 249         const struct inet_sock *inet = inet_sk(sk);
 250         const struct nf_conntrack_tuple_hash *h;
 251         struct nf_conntrack_tuple tuple;
 252
 253         memset(&tuple, 0, sizeof(tuple));
 254         tuple.src.u3.ip = inet->rcv_saddr;
 255         tuple.src.u.tcp.port = inet->sport;
 256         tuple.dst.u3.ip = inet->daddr;
 257         tuple.dst.u.tcp.port = inet->dport;
 258         tuple.src.l3num = PF_INET;
 259         tuple.dst.protonum = IPPROTO_TCP;
 260
 261         /* We only do TCP at the moment: is there a better way? */
 262         if (strcmp(sk->sk_prot->name, "TCP")) {
 263                 pr_debug("SO_ORIGINAL_DST: Not a TCP socket\n");
 264                 return -ENOPROTOOPT;
 265         }
 266
 267         if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
 268                 pr_debug("SO_ORIGINAL_DST: len %d not %Zu\n",
 269                          *len, sizeof(struct sockaddr_in));
 270                 return -EINVAL;
 271         }
 272
 273         h = nf_conntrack_find_get(sock_net(sk), &tuple);
 274         if (h) {
 275                 struct sockaddr_in sin;
 276                 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
 277
 278                 sin.sin_family = AF_INET;
 279                 sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 280                         .tuple.dst.u.tcp.port;
 281                 sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 282                         .tuple.dst.u3.ip;
 283                 memset(sin.sin_zero, 0, sizeof(sin.sin_zero));
 284
 285                 pr_debug("SO_ORIGINAL_DST: %pI4 %u\n",
 286                          &sin.sin_addr.s_addr, ntohs(sin.sin_port));
 287                 nf_ct_put(ct);
 288                 if (copy_to_user(user, &sin, sizeof(sin)) != 0)
 289                         return -EFAULT;
 290                 else
 291                         return 0;
 292         }
 293         pr_debug("SO_ORIGINAL_DST: Can't find %pI4/%u-%pI4/%u.\n",
 294                  &tuple.src.u3.ip, ntohs(tuple.src.u.tcp.port),
 295                  &tuple.dst.u3.ip, ntohs(tuple.dst.u.tcp.port));
 296         return -ENOENT;
 297 }
 298
 299 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 300
 301 #include <linux/netfilter/nfnetlink.h>
 302 #include <linux/netfilter/nfnetlink_conntrack.h>
 303
 304 static int ipv4_tuple_to_nlattr(struct sk_buff *skb,
 305                                 const struct nf_conntrack_tuple *tuple)
 306 {
 307         NLA_PUT_BE32(skb, CTA_IP_V4_SRC, tuple->src.u3.ip);
 308         NLA_PUT_BE32(skb, CTA_IP_V4_DST, tuple->dst.u3.ip);
 309         return 0;
 310
 311 nla_put_failure:
 312         return -1;
 313 }
 314
 315 static const struct nla_policy ipv4_nla_policy[CTA_IP_MAX+1] = {
 316         [CTA_IP_V4_SRC] = { .type = NLA_U32 },
 317         [CTA_IP_V4_DST] = { .type = NLA_U32 },
 318 };
 319
 320 static int ipv4_nlattr_to_tuple(struct nlattr *tb[],
 321                                 struct nf_conntrack_tuple *t)
 322 {
 323         if (!tb[CTA_IP_V4_SRC] || !tb[CTA_IP_V4_DST])
 324                 return -EINVAL;
 325
 326         t->src.u3.ip = nla_get_be32(tb[CTA_IP_V4_SRC]);
 327         t->dst.u3.ip = nla_get_be32(tb[CTA_IP_V4_DST]);
 328
 329         return 0;
 330 }
 331
 332 static int ipv4_nlattr_tuple_size(void)
 333 {
 334         return nla_policy_len(ipv4_nla_policy, CTA_IP_MAX + 1);
 335 }
 336 #endif
 337
 338 static struct nf_sockopt_ops so_getorigdst = {
 339         .pf             = PF_INET,
 340         .get_optmin     = SO_ORIGINAL_DST,
 341         .get_optmax     = SO_ORIGINAL_DST+1,
 342         .get            = &getorigdst,
 343         .owner          = THIS_MODULE,
 344 };
 345
 346 struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 __read_mostly = {
 347         .l3proto         = PF_INET,
 348         .name            = "ipv4",
 349         .pkt_to_tuple    = ipv4_pkt_to_tuple,
 350         .invert_tuple    = ipv4_invert_tuple,
 351         .print_tuple     = ipv4_print_tuple,
 352         .get_l4proto     = ipv4_get_l4proto,
 353 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 354         .tuple_to_nlattr = ipv4_tuple_to_nlattr,
 355         .nlattr_tuple_size = ipv4_nlattr_tuple_size,
 356         .nlattr_to_tuple = ipv4_nlattr_to_tuple,
 357         .nla_policy      = ipv4_nla_policy,
 358 #endif
 359 #if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 360         .ctl_table_path  = nf_net_ipv4_netfilter_sysctl_path,
 361         .ctl_table       = ip_ct_sysctl_table,
 362 #endif
 363         .me              = THIS_MODULE,
 364 };
 365
 366 module_param_call(hashsize, nf_conntrack_set_hashsize, param_get_uint,
 367                   &nf_conntrack_htable_size, 0600);
 368
 369 MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET));
 370 MODULE_ALIAS("ip_conntrack");
 371 MODULE_LICENSE("GPL");
 372
 373 static int __init nf_conntrack_l3proto_ipv4_init(void)
 374 {
 375         int ret = 0;
 376
 377         need_conntrack();
 378         nf_defrag_ipv4_enable();
 379
 380         ret = nf_register_sockopt(&so_getorigdst);
 381         if (ret < 0) {
 382                 printk(KERN_ERR "Unable to register netfilter socket option\n");
 383                 return ret;
 384         }
 385
 386         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_tcp4);
 387         if (ret < 0) {
 388                 printk("nf_conntrack_ipv4: can't register tcp.\n");
 389                 goto cleanup_sockopt;
 390         }
 391
 392         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_udp4);
 393         if (ret < 0) {
 394                 printk("nf_conntrack_ipv4: can't register udp.\n");
 395                 goto cleanup_tcp;
 396         }
 397
 398         ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_icmp);
 399         if (ret < 0) {
 400                 printk("nf_conntrack_ipv4: can't register icmp.\n");
 401                 goto cleanup_udp;
 402         }
 403
 404         ret = nf_conntrack_l3proto_register(&nf_conntrack_l3proto_ipv4);
 405         if (ret < 0) {
 406                 printk("nf_conntrack_ipv4: can't register ipv4\n");
 407                 goto cleanup_icmp;
 408         }
 409
 410         ret = nf_register_hooks(ipv4_conntrack_ops,
 411                                 ARRAY_SIZE(ipv4_conntrack_ops));
 412         if (ret < 0) {
 413                 printk("nf_conntrack_ipv4: can't register hooks.\n");
 414                 goto cleanup_ipv4;
 415         }
 416 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 417         ret = nf_conntrack_ipv4_compat_init();
 418         if (ret < 0)
 419                 goto cleanup_hooks;
 420 #endif
 421         return ret;
 422 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 423  cleanup_hooks:
 424         nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
 425 #endif
 426  cleanup_ipv4:
 427         nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 428  cleanup_icmp:
 429         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_icmp);
 430  cleanup_udp:
 431         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_udp4);
 432  cleanup_tcp:
 433         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_tcp4);
 434  cleanup_sockopt:
 435         nf_unregister_sockopt(&so_getorigdst);
 436         return ret;
 437 }
 438
 439 static void __exit nf_conntrack_l3proto_ipv4_fini(void)
 440 {
 441         synchronize_net();
 442 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 443         nf_conntrack_ipv4_compat_fini();
 444 #endif
 445         nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
 446         nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 447         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_icmp);
 448         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_udp4);
 449         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_tcp4);
 450         nf_unregister_sockopt(&so_getorigdst);
 451 }
 452
 453 module_init(nf_conntrack_l3proto_ipv4_init);
 454 module_exit(nf_conntrack_l3proto_ipv4_fini);
 455
 456 void need_ipv4_conntrack(void)
 457 {
 458         return;
 459 }
 460 EXPORT_SYMBOL_GPL(need_ipv4_conntrack);