1 /* 2 * ip_conntrack_proto_gre.c - Version 3.0 3 * 4 * Connection tracking protocol helper module for GRE. 5 * 6 * GRE is a generic encapsulation protocol, which is generally not very 7 * suited for NAT, as it has no protocol-specific part as port numbers. 8 * 9 * It has an optional key field, which may help us distinguishing two 10 * connections between the same two hosts. 11 * 12 * GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784 13 * 14 * PPTP is built on top of a modified version of GRE, and has a mandatory 15 * field called "CallID", which serves us for the same purpose as the key 16 * field in plain GRE. 17 * 18 * Documentation about PPTP can be found in RFC 2637 19 * 20 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org> 21 * 22 * Development of this code funded by Astaro AG (http://www.astaro.com/) 23 * 24 * (C) 2006-2012 Patrick McHardy <kaber@trash.net> 25 */ 26 27 #include <linux/module.h> 28 #include <linux/types.h> 29 #include <linux/timer.h> 30 #include <linux/list.h> 31 #include <linux/seq_file.h> 32 #include <linux/in.h> 33 #include <linux/netdevice.h> 34 #include <linux/skbuff.h> 35 #include <linux/slab.h> 36 #include <net/dst.h> 37 #include <net/net_namespace.h> 38 #include <net/netns/generic.h> 39 #include <net/netfilter/nf_conntrack_l4proto.h> 40 #include <net/netfilter/nf_conntrack_helper.h> 41 #include <net/netfilter/nf_conntrack_core.h> 42 #include <net/netfilter/nf_conntrack_timeout.h> 43 #include <linux/netfilter/nf_conntrack_proto_gre.h> 44 #include <linux/netfilter/nf_conntrack_pptp.h> 45 46 enum grep_conntrack { 47 GRE_CT_UNREPLIED, 48 GRE_CT_REPLIED, 49 GRE_CT_MAX 50 }; 51 52 static const unsigned int gre_timeouts[GRE_CT_MAX] = { 53 [GRE_CT_UNREPLIED] = 30*HZ, 54 [GRE_CT_REPLIED] = 180*HZ, 55 }; 56 57 static unsigned int proto_gre_net_id __read_mostly; 58 struct netns_proto_gre { 59 struct nf_proto_net nf; 60 rwlock_t keymap_lock; 61 struct list_head keymap_list; 62 unsigned int gre_timeouts[GRE_CT_MAX]; 63 }; 64 65 static inline struct netns_proto_gre *gre_pernet(struct net *net) 66 { 67 return net_generic(net, proto_gre_net_id); 68 } 69 70 static void nf_ct_gre_keymap_flush(struct net *net) 71 { 72 struct netns_proto_gre *net_gre = gre_pernet(net); 73 struct nf_ct_gre_keymap *km, *tmp; 74 75 write_lock_bh(&net_gre->keymap_lock); 76 list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) { 77 list_del(&km->list); 78 kfree(km); 79 } 80 write_unlock_bh(&net_gre->keymap_lock); 81 } 82 83 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km, 84 const struct nf_conntrack_tuple *t) 85 { 86 return km->tuple.src.l3num == t->src.l3num && 87 !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) && 88 !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) && 89 km->tuple.dst.protonum == t->dst.protonum && 90 km->tuple.dst.u.all == t->dst.u.all; 91 } 92 93 /* look up the source key for a given tuple */ 94 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t) 95 { 96 struct netns_proto_gre *net_gre = gre_pernet(net); 97 struct nf_ct_gre_keymap *km; 98 __be16 key = 0; 99 100 read_lock_bh(&net_gre->keymap_lock); 101 list_for_each_entry(km, &net_gre->keymap_list, list) { 102 if (gre_key_cmpfn(km, t)) { 103 key = km->tuple.src.u.gre.key; 104 break; 105 } 106 } 107 read_unlock_bh(&net_gre->keymap_lock); 108 109 pr_debug("lookup src key 0x%x for ", key); 110 nf_ct_dump_tuple(t); 111 112 return key; 113 } 114 115 /* add a single keymap entry, associate with specified master ct */ 116 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir, 117 struct nf_conntrack_tuple *t) 118 { 119 struct net *net = nf_ct_net(ct); 120 struct netns_proto_gre *net_gre = gre_pernet(net); 121 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct); 122 struct nf_ct_gre_keymap **kmp, *km; 123 124 kmp = &ct_pptp_info->keymap[dir]; 125 if (*kmp) { 126 /* check whether it's a retransmission */ 127 read_lock_bh(&net_gre->keymap_lock); 128 list_for_each_entry(km, &net_gre->keymap_list, list) { 129 if (gre_key_cmpfn(km, t) && km == *kmp) { 130 read_unlock_bh(&net_gre->keymap_lock); 131 return 0; 132 } 133 } 134 read_unlock_bh(&net_gre->keymap_lock); 135 pr_debug("trying to override keymap_%s for ct %p\n", 136 dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct); 137 return -EEXIST; 138 } 139 140 km = kmalloc(sizeof(*km), GFP_ATOMIC); 141 if (!km) 142 return -ENOMEM; 143 memcpy(&km->tuple, t, sizeof(*t)); 144 *kmp = km; 145 146 pr_debug("adding new entry %p: ", km); 147 nf_ct_dump_tuple(&km->tuple); 148 149 write_lock_bh(&net_gre->keymap_lock); 150 list_add_tail(&km->list, &net_gre->keymap_list); 151 write_unlock_bh(&net_gre->keymap_lock); 152 153 return 0; 154 } 155 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add); 156 157 /* destroy the keymap entries associated with specified master ct */ 158 void nf_ct_gre_keymap_destroy(struct nf_conn *ct) 159 { 160 struct net *net = nf_ct_net(ct); 161 struct netns_proto_gre *net_gre = gre_pernet(net); 162 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct); 163 enum ip_conntrack_dir dir; 164 165 pr_debug("entering for ct %p\n", ct); 166 167 write_lock_bh(&net_gre->keymap_lock); 168 for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) { 169 if (ct_pptp_info->keymap[dir]) { 170 pr_debug("removing %p from list\n", 171 ct_pptp_info->keymap[dir]); 172 list_del(&ct_pptp_info->keymap[dir]->list); 173 kfree(ct_pptp_info->keymap[dir]); 174 ct_pptp_info->keymap[dir] = NULL; 175 } 176 } 177 write_unlock_bh(&net_gre->keymap_lock); 178 } 179 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy); 180 181 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */ 182 183 /* gre hdr info to tuple */ 184 static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff, 185 struct net *net, struct nf_conntrack_tuple *tuple) 186 { 187 const struct pptp_gre_header *pgrehdr; 188 struct pptp_gre_header _pgrehdr; 189 __be16 srckey; 190 const struct gre_base_hdr *grehdr; 191 struct gre_base_hdr _grehdr; 192 193 /* first only delinearize old RFC1701 GRE header */ 194 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr); 195 if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) { 196 /* try to behave like "nf_conntrack_proto_generic" */ 197 tuple->src.u.all = 0; 198 tuple->dst.u.all = 0; 199 return true; 200 } 201 202 /* PPTP header is variable length, only need up to the call_id field */ 203 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr); 204 if (!pgrehdr) 205 return true; 206 207 if (grehdr->protocol != GRE_PROTO_PPP) { 208 pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol)); 209 return false; 210 } 211 212 tuple->dst.u.gre.key = pgrehdr->call_id; 213 srckey = gre_keymap_lookup(net, tuple); 214 tuple->src.u.gre.key = srckey; 215 216 return true; 217 } 218 219 #ifdef CONFIG_NF_CONNTRACK_PROCFS 220 /* print private data for conntrack */ 221 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct) 222 { 223 seq_printf(s, "timeout=%u, stream_timeout=%u ", 224 (ct->proto.gre.timeout / HZ), 225 (ct->proto.gre.stream_timeout / HZ)); 226 } 227 #endif 228 229 static unsigned int *gre_get_timeouts(struct net *net) 230 { 231 return gre_pernet(net)->gre_timeouts; 232 } 233 234 /* Returns verdict for packet, and may modify conntrack */ 235 static int gre_packet(struct nf_conn *ct, 236 struct sk_buff *skb, 237 unsigned int dataoff, 238 enum ip_conntrack_info ctinfo, 239 const struct nf_hook_state *state) 240 { 241 if (state->pf != NFPROTO_IPV4) 242 return -NF_ACCEPT; 243 244 if (!nf_ct_is_confirmed(ct)) { 245 unsigned int *timeouts = nf_ct_timeout_lookup(ct); 246 247 if (!timeouts) 248 timeouts = gre_get_timeouts(nf_ct_net(ct)); 249 250 /* initialize to sane value. Ideally a conntrack helper 251 * (e.g. in case of pptp) is increasing them */ 252 ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED]; 253 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED]; 254 } 255 256 /* If we've seen traffic both ways, this is a GRE connection. 257 * Extend timeout. */ 258 if (ct->status & IPS_SEEN_REPLY) { 259 nf_ct_refresh_acct(ct, ctinfo, skb, 260 ct->proto.gre.stream_timeout); 261 /* Also, more likely to be important, and not a probe. */ 262 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status)) 263 nf_conntrack_event_cache(IPCT_ASSURED, ct); 264 } else 265 nf_ct_refresh_acct(ct, ctinfo, skb, 266 ct->proto.gre.timeout); 267 268 return NF_ACCEPT; 269 } 270 271 /* Called when a conntrack entry has already been removed from the hashes 272 * and is about to be deleted from memory */ 273 static void gre_destroy(struct nf_conn *ct) 274 { 275 struct nf_conn *master = ct->master; 276 pr_debug(" entering\n"); 277 278 if (!master) 279 pr_debug("no master !?!\n"); 280 else 281 nf_ct_gre_keymap_destroy(master); 282 } 283 284 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT 285 286 #include <linux/netfilter/nfnetlink.h> 287 #include <linux/netfilter/nfnetlink_cttimeout.h> 288 289 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[], 290 struct net *net, void *data) 291 { 292 unsigned int *timeouts = data; 293 struct netns_proto_gre *net_gre = gre_pernet(net); 294 295 if (!timeouts) 296 timeouts = gre_get_timeouts(net); 297 /* set default timeouts for GRE. */ 298 timeouts[GRE_CT_UNREPLIED] = net_gre->gre_timeouts[GRE_CT_UNREPLIED]; 299 timeouts[GRE_CT_REPLIED] = net_gre->gre_timeouts[GRE_CT_REPLIED]; 300 301 if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) { 302 timeouts[GRE_CT_UNREPLIED] = 303 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ; 304 } 305 if (tb[CTA_TIMEOUT_GRE_REPLIED]) { 306 timeouts[GRE_CT_REPLIED] = 307 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ; 308 } 309 return 0; 310 } 311 312 static int 313 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data) 314 { 315 const unsigned int *timeouts = data; 316 317 if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED, 318 htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) || 319 nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED, 320 htonl(timeouts[GRE_CT_REPLIED] / HZ))) 321 goto nla_put_failure; 322 return 0; 323 324 nla_put_failure: 325 return -ENOSPC; 326 } 327 328 static const struct nla_policy 329 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = { 330 [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 }, 331 [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 }, 332 }; 333 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ 334 335 static int gre_init_net(struct net *net) 336 { 337 struct netns_proto_gre *net_gre = gre_pernet(net); 338 int i; 339 340 rwlock_init(&net_gre->keymap_lock); 341 INIT_LIST_HEAD(&net_gre->keymap_list); 342 for (i = 0; i < GRE_CT_MAX; i++) 343 net_gre->gre_timeouts[i] = gre_timeouts[i]; 344 345 return 0; 346 } 347 348 /* protocol helper struct */ 349 static const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 = { 350 .l4proto = IPPROTO_GRE, 351 .pkt_to_tuple = gre_pkt_to_tuple, 352 #ifdef CONFIG_NF_CONNTRACK_PROCFS 353 .print_conntrack = gre_print_conntrack, 354 #endif 355 .packet = gre_packet, 356 .destroy = gre_destroy, 357 .me = THIS_MODULE, 358 #if IS_ENABLED(CONFIG_NF_CT_NETLINK) 359 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr, 360 .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size, 361 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple, 362 .nla_policy = nf_ct_port_nla_policy, 363 #endif 364 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT 365 .ctnl_timeout = { 366 .nlattr_to_obj = gre_timeout_nlattr_to_obj, 367 .obj_to_nlattr = gre_timeout_obj_to_nlattr, 368 .nlattr_max = CTA_TIMEOUT_GRE_MAX, 369 .obj_size = sizeof(unsigned int) * GRE_CT_MAX, 370 .nla_policy = gre_timeout_nla_policy, 371 }, 372 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ 373 .net_id = &proto_gre_net_id, 374 .init_net = gre_init_net, 375 }; 376 377 static int proto_gre_net_init(struct net *net) 378 { 379 int ret = 0; 380 381 ret = nf_ct_l4proto_pernet_register_one(net, 382 &nf_conntrack_l4proto_gre4); 383 if (ret < 0) 384 pr_err("nf_conntrack_gre4: pernet registration failed.\n"); 385 return ret; 386 } 387 388 static void proto_gre_net_exit(struct net *net) 389 { 390 nf_ct_l4proto_pernet_unregister_one(net, &nf_conntrack_l4proto_gre4); 391 nf_ct_gre_keymap_flush(net); 392 } 393 394 static struct pernet_operations proto_gre_net_ops = { 395 .init = proto_gre_net_init, 396 .exit = proto_gre_net_exit, 397 .id = &proto_gre_net_id, 398 .size = sizeof(struct netns_proto_gre), 399 }; 400 401 static int __init nf_ct_proto_gre_init(void) 402 { 403 int ret; 404 405 ret = register_pernet_subsys(&proto_gre_net_ops); 406 if (ret < 0) 407 goto out_pernet; 408 ret = nf_ct_l4proto_register_one(&nf_conntrack_l4proto_gre4); 409 if (ret < 0) 410 goto out_gre4; 411 412 return 0; 413 out_gre4: 414 unregister_pernet_subsys(&proto_gre_net_ops); 415 out_pernet: 416 return ret; 417 } 418 419 static void __exit nf_ct_proto_gre_fini(void) 420 { 421 nf_ct_l4proto_unregister_one(&nf_conntrack_l4proto_gre4); 422 unregister_pernet_subsys(&proto_gre_net_ops); 423 } 424 425 module_init(nf_ct_proto_gre_init); 426 module_exit(nf_ct_proto_gre_fini); 427 428 MODULE_LICENSE("GPL"); 429