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