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  * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/types.h>
  12 #include <linux/ip.h>
  13 #include <linux/netfilter.h>
  14 #include <linux/module.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/icmp.h>
  17 #include <linux/sysctl.h>
  18 #include <net/route.h>
  19 #include <net/ip.h>
  20
  21 #include <linux/netfilter_ipv4.h>
  22 #include <net/netfilter/nf_conntrack.h>
  23 #include <net/netfilter/nf_conntrack_helper.h>
  24 #include <net/netfilter/nf_conntrack_l4proto.h>
  25 #include <net/netfilter/nf_conntrack_l3proto.h>
  26 #include <net/netfilter/nf_conntrack_zones.h>
  27 #include <net/netfilter/nf_conntrack_core.h>
  28 #include <net/netfilter/nf_conntrack_seqadj.h>
  29 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
  30 #include <net/netfilter/nf_nat_helper.h>
  31 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  32 #include <net/netfilter/nf_log.h>
  33
  34 static int conntrack4_net_id __read_mostly;
  35 static DEFINE_MUTEX(register_ipv4_hooks);
  36
  37 struct conntrack4_net {
  38         unsigned int users;
  39 };
  40
  41 static bool ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
  42                               struct nf_conntrack_tuple *tuple)
  43 {
  44         const __be32 *ap;
  45         __be32 _addrs[2];
  46         ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
  47                                 sizeof(u_int32_t) * 2, _addrs);
  48         if (ap == NULL)
  49                 return false;
  50
  51         tuple->src.u3.ip = ap[0];
  52         tuple->dst.u3.ip = ap[1];
  53
  54         return true;
  55 }
  56
  57 static bool ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
  58                               const struct nf_conntrack_tuple *orig)
  59 {
  60         tuple->src.u3.ip = orig->dst.u3.ip;
  61         tuple->dst.u3.ip = orig->src.u3.ip;
  62
  63         return true;
  64 }
  65
  66 static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
  67                             unsigned int *dataoff, u_int8_t *protonum)
  68 {
  69         const struct iphdr *iph;
  70         struct iphdr _iph;
  71
  72         iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  73         if (iph == NULL)
  74                 return -NF_ACCEPT;
  75
  76         /* Conntrack defragments packets, we might still see fragments
  77          * inside ICMP packets though. */
  78         if (iph->frag_off & htons(IP_OFFSET))
  79                 return -NF_ACCEPT;
  80
  81         *dataoff = nhoff + (iph->ihl << 2);
  82         *protonum = iph->protocol;
  83
  84         /* Check bogus IP headers */
  85         if (*dataoff > skb->len) {
  86                 pr_debug("nf_conntrack_ipv4: bogus IPv4 packet: "
  87                          "nhoff %u, ihl %u, skblen %u\n",
  88                          nhoff, iph->ihl << 2, skb->len);
  89                 return -NF_ACCEPT;
  90         }
  91
  92         return NF_ACCEPT;
  93 }
  94
  95 static unsigned int ipv4_helper(void *priv,
  96                                 struct sk_buff *skb,
  97                                 const struct nf_hook_state *state)
  98 {
  99         struct nf_conn *ct;
 100         enum ip_conntrack_info ctinfo;
 101         const struct nf_conn_help *help;
 102         const struct nf_conntrack_helper *helper;
 103
 104         /* This is where we call the helper: as the packet goes out. */
 105         ct = nf_ct_get(skb, &ctinfo);
 106         if (!ct || ctinfo == IP_CT_RELATED_REPLY)
 107                 return NF_ACCEPT;
 108
 109         help = nfct_help(ct);
 110         if (!help)
 111                 return NF_ACCEPT;
 112
 113         /* rcu_read_lock()ed by nf_hook_thresh */
 114         helper = rcu_dereference(help->helper);
 115         if (!helper)
 116                 return NF_ACCEPT;
 117
 118         return helper->help(skb, skb_network_offset(skb) + ip_hdrlen(skb),
 119                             ct, ctinfo);
 120 }
 121
 122 static unsigned int ipv4_confirm(void *priv,
 123                                  struct sk_buff *skb,
 124                                  const struct nf_hook_state *state)
 125 {
 126         struct nf_conn *ct;
 127         enum ip_conntrack_info ctinfo;
 128
 129         ct = nf_ct_get(skb, &ctinfo);
 130         if (!ct || ctinfo == IP_CT_RELATED_REPLY)
 131                 goto out;
 132
 133         /* adjust seqs for loopback traffic only in outgoing direction */
 134         if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) &&
 135             !nf_is_loopback_packet(skb)) {
 136                 if (!nf_ct_seq_adjust(skb, ct, ctinfo, ip_hdrlen(skb))) {
 137                         NF_CT_STAT_INC_ATOMIC(nf_ct_net(ct), drop);
 138                         return NF_DROP;
 139                 }
 140         }
 141 out:
 142         /* We've seen it coming out the other side: confirm it */
 143         return nf_conntrack_confirm(skb);
 144 }
 145
 146 static unsigned int ipv4_conntrack_in(void *priv,
 147                                       struct sk_buff *skb,
 148                                       const struct nf_hook_state *state)
 149 {
 150         return nf_conntrack_in(state->net, PF_INET, state->hook, skb);
 151 }
 152
 153 static unsigned int ipv4_conntrack_local(void *priv,
 154                                          struct sk_buff *skb,
 155                                          const struct nf_hook_state *state)
 156 {
 157         /* root is playing with raw sockets. */
 158         if (skb->len < sizeof(struct iphdr) ||
 159             ip_hdrlen(skb) < sizeof(struct iphdr))
 160                 return NF_ACCEPT;
 161
 162         if (ip_is_fragment(ip_hdr(skb))) { /* IP_NODEFRAG setsockopt set */
 163                 enum ip_conntrack_info ctinfo;
 164                 struct nf_conn *tmpl;
 165
 166                 tmpl = nf_ct_get(skb, &ctinfo);
 167                 if (tmpl && nf_ct_is_template(tmpl)) {
 168                         /* when skipping ct, clear templates to avoid fooling
 169                          * later targets/matches
 170                          */
 171                         skb->_nfct = 0;
 172                         nf_ct_put(tmpl);
 173                 }
 174                 return NF_ACCEPT;
 175         }
 176
 177         return nf_conntrack_in(state->net, PF_INET, state->hook, skb);
 178 }
 179
 180 /* Connection tracking may drop packets, but never alters them, so
 181    make it the first hook. */
 182 static const struct nf_hook_ops ipv4_conntrack_ops[] = {
 183         {
 184                 .hook           = ipv4_conntrack_in,
 185                 .pf             = NFPROTO_IPV4,
 186                 .hooknum        = NF_INET_PRE_ROUTING,
 187                 .priority       = NF_IP_PRI_CONNTRACK,
 188         },
 189         {
 190                 .hook           = ipv4_conntrack_local,
 191                 .pf             = NFPROTO_IPV4,
 192                 .hooknum        = NF_INET_LOCAL_OUT,
 193                 .priority       = NF_IP_PRI_CONNTRACK,
 194         },
 195         {
 196                 .hook           = ipv4_helper,
 197                 .pf             = NFPROTO_IPV4,
 198                 .hooknum        = NF_INET_POST_ROUTING,
 199                 .priority       = NF_IP_PRI_CONNTRACK_HELPER,
 200         },
 201         {
 202                 .hook           = ipv4_confirm,
 203                 .pf             = NFPROTO_IPV4,
 204                 .hooknum        = NF_INET_POST_ROUTING,
 205                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 206         },
 207         {
 208                 .hook           = ipv4_helper,
 209                 .pf             = NFPROTO_IPV4,
 210                 .hooknum        = NF_INET_LOCAL_IN,
 211                 .priority       = NF_IP_PRI_CONNTRACK_HELPER,
 212         },
 213         {
 214                 .hook           = ipv4_confirm,
 215                 .pf             = NFPROTO_IPV4,
 216                 .hooknum        = NF_INET_LOCAL_IN,
 217                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 218         },
 219 };
 220
 221 /* Fast function for those who don't want to parse /proc (and I don't
 222    blame them). */
 223 /* Reversing the socket's dst/src point of view gives us the reply
 224    mapping. */
 225 static int
 226 getorigdst(struct sock *sk, int optval, void __user *user, int *len)
 227 {
 228         const struct inet_sock *inet = inet_sk(sk);
 229         const struct nf_conntrack_tuple_hash *h;
 230         struct nf_conntrack_tuple tuple;
 231
 232         memset(&tuple, 0, sizeof(tuple));
 233
 234         lock_sock(sk);
 235         tuple.src.u3.ip = inet->inet_rcv_saddr;
 236         tuple.src.u.tcp.port = inet->inet_sport;
 237         tuple.dst.u3.ip = inet->inet_daddr;
 238         tuple.dst.u.tcp.port = inet->inet_dport;
 239         tuple.src.l3num = PF_INET;
 240         tuple.dst.protonum = sk->sk_protocol;
 241         release_sock(sk);
 242
 243         /* We only do TCP and SCTP at the moment: is there a better way? */
 244         if (tuple.dst.protonum != IPPROTO_TCP &&
 245             tuple.dst.protonum != IPPROTO_SCTP) {
 246                 pr_debug("SO_ORIGINAL_DST: Not a TCP/SCTP socket\n");
 247                 return -ENOPROTOOPT;
 248         }
 249
 250         if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
 251                 pr_debug("SO_ORIGINAL_DST: len %d not %zu\n",
 252                          *len, sizeof(struct sockaddr_in));
 253                 return -EINVAL;
 254         }
 255
 256         h = nf_conntrack_find_get(sock_net(sk), &nf_ct_zone_dflt, &tuple);
 257         if (h) {
 258                 struct sockaddr_in sin;
 259                 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
 260
 261                 sin.sin_family = AF_INET;
 262                 sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 263                         .tuple.dst.u.tcp.port;
 264                 sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 265                         .tuple.dst.u3.ip;
 266                 memset(sin.sin_zero, 0, sizeof(sin.sin_zero));
 267
 268                 pr_debug("SO_ORIGINAL_DST: %pI4 %u\n",
 269                          &sin.sin_addr.s_addr, ntohs(sin.sin_port));
 270                 nf_ct_put(ct);
 271                 if (copy_to_user(user, &sin, sizeof(sin)) != 0)
 272                         return -EFAULT;
 273                 else
 274                         return 0;
 275         }
 276         pr_debug("SO_ORIGINAL_DST: Can't find %pI4/%u-%pI4/%u.\n",
 277                  &tuple.src.u3.ip, ntohs(tuple.src.u.tcp.port),
 278                  &tuple.dst.u3.ip, ntohs(tuple.dst.u.tcp.port));
 279         return -ENOENT;
 280 }
 281
 282 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 283
 284 #include <linux/netfilter/nfnetlink.h>
 285 #include <linux/netfilter/nfnetlink_conntrack.h>
 286
 287 static int ipv4_tuple_to_nlattr(struct sk_buff *skb,
 288                                 const struct nf_conntrack_tuple *tuple)
 289 {
 290         if (nla_put_in_addr(skb, CTA_IP_V4_SRC, tuple->src.u3.ip) ||
 291             nla_put_in_addr(skb, CTA_IP_V4_DST, tuple->dst.u3.ip))
 292                 goto nla_put_failure;
 293         return 0;
 294
 295 nla_put_failure:
 296         return -1;
 297 }
 298
 299 static const struct nla_policy ipv4_nla_policy[CTA_IP_MAX+1] = {
 300         [CTA_IP_V4_SRC] = { .type = NLA_U32 },
 301         [CTA_IP_V4_DST] = { .type = NLA_U32 },
 302 };
 303
 304 static int ipv4_nlattr_to_tuple(struct nlattr *tb[],
 305                                 struct nf_conntrack_tuple *t)
 306 {
 307         if (!tb[CTA_IP_V4_SRC] || !tb[CTA_IP_V4_DST])
 308                 return -EINVAL;
 309
 310         t->src.u3.ip = nla_get_in_addr(tb[CTA_IP_V4_SRC]);
 311         t->dst.u3.ip = nla_get_in_addr(tb[CTA_IP_V4_DST]);
 312
 313         return 0;
 314 }
 315 #endif
 316
 317 static struct nf_sockopt_ops so_getorigdst = {
 318         .pf             = PF_INET,
 319         .get_optmin     = SO_ORIGINAL_DST,
 320         .get_optmax     = SO_ORIGINAL_DST+1,
 321         .get            = getorigdst,
 322         .owner          = THIS_MODULE,
 323 };
 324
 325 static int ipv4_hooks_register(struct net *net)
 326 {
 327         struct conntrack4_net *cnet = net_generic(net, conntrack4_net_id);
 328         int err = 0;
 329
 330         mutex_lock(&register_ipv4_hooks);
 331
 332         cnet->users++;
 333         if (cnet->users > 1)
 334                 goto out_unlock;
 335
 336         err = nf_defrag_ipv4_enable(net);
 337         if (err) {
 338                 cnet->users = 0;
 339                 goto out_unlock;
 340         }
 341
 342         err = nf_register_net_hooks(net, ipv4_conntrack_ops,
 343                                     ARRAY_SIZE(ipv4_conntrack_ops));
 344
 345         if (err)
 346                 cnet->users = 0;
 347  out_unlock:
 348         mutex_unlock(&register_ipv4_hooks);
 349         return err;
 350 }
 351
 352 static void ipv4_hooks_unregister(struct net *net)
 353 {
 354         struct conntrack4_net *cnet = net_generic(net, conntrack4_net_id);
 355
 356         mutex_lock(&register_ipv4_hooks);
 357         if (cnet->users && (--cnet->users == 0))
 358                 nf_unregister_net_hooks(net, ipv4_conntrack_ops,
 359                                         ARRAY_SIZE(ipv4_conntrack_ops));
 360         mutex_unlock(&register_ipv4_hooks);
 361 }
 362
 363 struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 __read_mostly = {
 364         .l3proto         = PF_INET,
 365         .pkt_to_tuple    = ipv4_pkt_to_tuple,
 366         .invert_tuple    = ipv4_invert_tuple,
 367         .get_l4proto     = ipv4_get_l4proto,
 368 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 369         .tuple_to_nlattr = ipv4_tuple_to_nlattr,
 370         .nlattr_to_tuple = ipv4_nlattr_to_tuple,
 371         .nla_policy      = ipv4_nla_policy,
 372         .nla_size        = NLA_ALIGN(NLA_HDRLEN + sizeof(u32)) + /* CTA_IP_V4_SRC */
 373                            NLA_ALIGN(NLA_HDRLEN + sizeof(u32)),  /* CTA_IP_V4_DST */
 374 #endif
 375         .net_ns_get      = ipv4_hooks_register,
 376         .net_ns_put      = ipv4_hooks_unregister,
 377         .me              = THIS_MODULE,
 378 };
 379
 380 module_param_call(hashsize, nf_conntrack_set_hashsize, param_get_uint,
 381                   &nf_conntrack_htable_size, 0600);
 382
 383 MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET));
 384 MODULE_ALIAS("ip_conntrack");
 385 MODULE_LICENSE("GPL");
 386
 387 static struct nf_conntrack_l4proto *builtin_l4proto4[] = {
 388         &nf_conntrack_l4proto_tcp4,
 389         &nf_conntrack_l4proto_udp4,
 390         &nf_conntrack_l4proto_icmp,
 391 #ifdef CONFIG_NF_CT_PROTO_DCCP
 392         &nf_conntrack_l4proto_dccp4,
 393 #endif
 394 #ifdef CONFIG_NF_CT_PROTO_SCTP
 395         &nf_conntrack_l4proto_sctp4,
 396 #endif
 397 #ifdef CONFIG_NF_CT_PROTO_UDPLITE
 398         &nf_conntrack_l4proto_udplite4,
 399 #endif
 400 };
 401
 402 static int ipv4_net_init(struct net *net)
 403 {
 404         return nf_ct_l4proto_pernet_register(net, builtin_l4proto4,
 405                                              ARRAY_SIZE(builtin_l4proto4));
 406 }
 407
 408 static void ipv4_net_exit(struct net *net)
 409 {
 410         nf_ct_l4proto_pernet_unregister(net, builtin_l4proto4,
 411                                         ARRAY_SIZE(builtin_l4proto4));
 412 }
 413
 414 static struct pernet_operations ipv4_net_ops = {
 415         .init = ipv4_net_init,
 416         .exit = ipv4_net_exit,
 417         .id = &conntrack4_net_id,
 418         .size = sizeof(struct conntrack4_net),
 419 };
 420
 421 static int __init nf_conntrack_l3proto_ipv4_init(void)
 422 {
 423         int ret = 0;
 424
 425         need_conntrack();
 426
 427 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 428         if (WARN_ON(nla_policy_len(ipv4_nla_policy, CTA_IP_MAX + 1) !=
 429             nf_conntrack_l3proto_ipv4.nla_size))
 430                 return -EINVAL;
 431 #endif
 432         ret = nf_register_sockopt(&so_getorigdst);
 433         if (ret < 0) {
 434                 pr_err("Unable to register netfilter socket option\n");
 435                 return ret;
 436         }
 437
 438         ret = register_pernet_subsys(&ipv4_net_ops);
 439         if (ret < 0) {
 440                 pr_err("nf_conntrack_ipv4: can't register pernet ops\n");
 441                 goto cleanup_sockopt;
 442         }
 443
 444         ret = nf_ct_l4proto_register(builtin_l4proto4,
 445                                      ARRAY_SIZE(builtin_l4proto4));
 446         if (ret < 0)
 447                 goto cleanup_pernet;
 448
 449         ret = nf_ct_l3proto_register(&nf_conntrack_l3proto_ipv4);
 450         if (ret < 0) {
 451                 pr_err("nf_conntrack_ipv4: can't register ipv4 proto.\n");
 452                 goto cleanup_l4proto;
 453         }
 454
 455         return ret;
 456 cleanup_l4proto:
 457         nf_ct_l4proto_unregister(builtin_l4proto4,
 458                                  ARRAY_SIZE(builtin_l4proto4));
 459  cleanup_pernet:
 460         unregister_pernet_subsys(&ipv4_net_ops);
 461  cleanup_sockopt:
 462         nf_unregister_sockopt(&so_getorigdst);
 463         return ret;
 464 }
 465
 466 static void __exit nf_conntrack_l3proto_ipv4_fini(void)
 467 {
 468         synchronize_net();
 469         nf_ct_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 470         nf_ct_l4proto_unregister(builtin_l4proto4,
 471                                  ARRAY_SIZE(builtin_l4proto4));
 472         unregister_pernet_subsys(&ipv4_net_ops);
 473         nf_unregister_sockopt(&so_getorigdst);
 474 }
 475
 476 module_init(nf_conntrack_l3proto_ipv4_init);
 477 module_exit(nf_conntrack_l3proto_ipv4_fini);