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 <linux/netfilter/nf_conntrack_proto_gre.h> 43 #include <linux/netfilter/nf_conntrack_pptp.h> 44 45 enum grep_conntrack { 46 GRE_CT_UNREPLIED, 47 GRE_CT_REPLIED, 48 GRE_CT_MAX 49 }; 50 51 static unsigned int gre_timeouts[GRE_CT_MAX] = { 52 [GRE_CT_UNREPLIED] = 30*HZ, 53 [GRE_CT_REPLIED] = 180*HZ, 54 }; 55 56 static unsigned int proto_gre_net_id __read_mostly; 57 struct netns_proto_gre { 58 struct nf_proto_net nf; 59 rwlock_t keymap_lock; 60 struct list_head keymap_list; 61 unsigned int gre_timeouts[GRE_CT_MAX]; 62 }; 63 64 static inline struct netns_proto_gre *gre_pernet(struct net *net) 65 { 66 return net_generic(net, proto_gre_net_id); 67 } 68 69 static void nf_ct_gre_keymap_flush(struct net *net) 70 { 71 struct netns_proto_gre *net_gre = gre_pernet(net); 72 struct nf_ct_gre_keymap *km, *tmp; 73 74 write_lock_bh(&net_gre->keymap_lock); 75 list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) { 76 list_del(&km->list); 77 kfree(km); 78 } 79 write_unlock_bh(&net_gre->keymap_lock); 80 } 81 82 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km, 83 const struct nf_conntrack_tuple *t) 84 { 85 return km->tuple.src.l3num == t->src.l3num && 86 !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) && 87 !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) && 88 km->tuple.dst.protonum == t->dst.protonum && 89 km->tuple.dst.u.all == t->dst.u.all; 90 } 91 92 /* look up the source key for a given tuple */ 93 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t) 94 { 95 struct netns_proto_gre *net_gre = gre_pernet(net); 96 struct nf_ct_gre_keymap *km; 97 __be16 key = 0; 98 99 read_lock_bh(&net_gre->keymap_lock); 100 list_for_each_entry(km, &net_gre->keymap_list, list) { 101 if (gre_key_cmpfn(km, t)) { 102 key = km->tuple.src.u.gre.key; 103 break; 104 } 105 } 106 read_unlock_bh(&net_gre->keymap_lock); 107 108 pr_debug("lookup src key 0x%x for ", key); 109 nf_ct_dump_tuple(t); 110 111 return key; 112 } 113 114 /* add a single keymap entry, associate with specified master ct */ 115 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir, 116 struct nf_conntrack_tuple *t) 117 { 118 struct net *net = nf_ct_net(ct); 119 struct netns_proto_gre *net_gre = gre_pernet(net); 120 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct); 121 struct nf_ct_gre_keymap **kmp, *km; 122 123 kmp = &ct_pptp_info->keymap[dir]; 124 if (*kmp) { 125 /* check whether it's a retransmission */ 126 read_lock_bh(&net_gre->keymap_lock); 127 list_for_each_entry(km, &net_gre->keymap_list, list) { 128 if (gre_key_cmpfn(km, t) && km == *kmp) { 129 read_unlock_bh(&net_gre->keymap_lock); 130 return 0; 131 } 132 } 133 read_unlock_bh(&net_gre->keymap_lock); 134 pr_debug("trying to override keymap_%s for ct %p\n", 135 dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct); 136 return -EEXIST; 137 } 138 139 km = kmalloc(sizeof(*km), GFP_ATOMIC); 140 if (!km) 141 return -ENOMEM; 142 memcpy(&km->tuple, t, sizeof(*t)); 143 *kmp = km; 144 145 pr_debug("adding new entry %p: ", km); 146 nf_ct_dump_tuple(&km->tuple); 147 148 write_lock_bh(&net_gre->keymap_lock); 149 list_add_tail(&km->list, &net_gre->keymap_list); 150 write_unlock_bh(&net_gre->keymap_lock); 151 152 return 0; 153 } 154 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add); 155 156 /* destroy the keymap entries associated with specified master ct */ 157 void nf_ct_gre_keymap_destroy(struct nf_conn *ct) 158 { 159 struct net *net = nf_ct_net(ct); 160 struct netns_proto_gre *net_gre = gre_pernet(net); 161 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct); 162 enum ip_conntrack_dir dir; 163 164 pr_debug("entering for ct %p\n", ct); 165 166 write_lock_bh(&net_gre->keymap_lock); 167 for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) { 168 if (ct_pptp_info->keymap[dir]) { 169 pr_debug("removing %p from list\n", 170 ct_pptp_info->keymap[dir]); 171 list_del(&ct_pptp_info->keymap[dir]->list); 172 kfree(ct_pptp_info->keymap[dir]); 173 ct_pptp_info->keymap[dir] = NULL; 174 } 175 } 176 write_unlock_bh(&net_gre->keymap_lock); 177 } 178 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy); 179 180 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */ 181 182 /* invert gre part of tuple */ 183 static bool gre_invert_tuple(struct nf_conntrack_tuple *tuple, 184 const struct nf_conntrack_tuple *orig) 185 { 186 tuple->dst.u.gre.key = orig->src.u.gre.key; 187 tuple->src.u.gre.key = orig->dst.u.gre.key; 188 return true; 189 } 190 191 /* gre hdr info to tuple */ 192 static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff, 193 struct net *net, struct nf_conntrack_tuple *tuple) 194 { 195 const struct pptp_gre_header *pgrehdr; 196 struct pptp_gre_header _pgrehdr; 197 __be16 srckey; 198 const struct gre_base_hdr *grehdr; 199 struct gre_base_hdr _grehdr; 200 201 /* first only delinearize old RFC1701 GRE header */ 202 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr); 203 if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) { 204 /* try to behave like "nf_conntrack_proto_generic" */ 205 tuple->src.u.all = 0; 206 tuple->dst.u.all = 0; 207 return true; 208 } 209 210 /* PPTP header is variable length, only need up to the call_id field */ 211 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr); 212 if (!pgrehdr) 213 return true; 214 215 if (grehdr->protocol != GRE_PROTO_PPP) { 216 pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol)); 217 return false; 218 } 219 220 tuple->dst.u.gre.key = pgrehdr->call_id; 221 srckey = gre_keymap_lookup(net, tuple); 222 tuple->src.u.gre.key = srckey; 223 224 return true; 225 } 226 227 #ifdef CONFIG_NF_CONNTRACK_PROCFS 228 /* print private data for conntrack */ 229 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct) 230 { 231 seq_printf(s, "timeout=%u, stream_timeout=%u ", 232 (ct->proto.gre.timeout / HZ), 233 (ct->proto.gre.stream_timeout / HZ)); 234 } 235 #endif 236 237 static unsigned int *gre_get_timeouts(struct net *net) 238 { 239 return gre_pernet(net)->gre_timeouts; 240 } 241 242 /* Returns verdict for packet, and may modify conntrack */ 243 static int gre_packet(struct nf_conn *ct, 244 const struct sk_buff *skb, 245 unsigned int dataoff, 246 enum ip_conntrack_info ctinfo, 247 u_int8_t pf, 248 unsigned int *timeouts) 249 { 250 /* If we've seen traffic both ways, this is a GRE connection. 251 * Extend timeout. */ 252 if (ct->status & IPS_SEEN_REPLY) { 253 nf_ct_refresh_acct(ct, ctinfo, skb, 254 ct->proto.gre.stream_timeout); 255 /* Also, more likely to be important, and not a probe. */ 256 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status)) 257 nf_conntrack_event_cache(IPCT_ASSURED, ct); 258 } else 259 nf_ct_refresh_acct(ct, ctinfo, skb, 260 ct->proto.gre.timeout); 261 262 return NF_ACCEPT; 263 } 264 265 /* Called when a new connection for this protocol found. */ 266 static bool gre_new(struct nf_conn *ct, const struct sk_buff *skb, 267 unsigned int dataoff, unsigned int *timeouts) 268 { 269 pr_debug(": "); 270 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple); 271 272 /* initialize to sane value. Ideally a conntrack helper 273 * (e.g. in case of pptp) is increasing them */ 274 ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED]; 275 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED]; 276 277 return true; 278 } 279 280 /* Called when a conntrack entry has already been removed from the hashes 281 * and is about to be deleted from memory */ 282 static void gre_destroy(struct nf_conn *ct) 283 { 284 struct nf_conn *master = ct->master; 285 pr_debug(" entering\n"); 286 287 if (!master) 288 pr_debug("no master !?!\n"); 289 else 290 nf_ct_gre_keymap_destroy(master); 291 } 292 293 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT) 294 295 #include <linux/netfilter/nfnetlink.h> 296 #include <linux/netfilter/nfnetlink_cttimeout.h> 297 298 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[], 299 struct net *net, void *data) 300 { 301 unsigned int *timeouts = data; 302 struct netns_proto_gre *net_gre = gre_pernet(net); 303 304 /* set default timeouts for GRE. */ 305 timeouts[GRE_CT_UNREPLIED] = net_gre->gre_timeouts[GRE_CT_UNREPLIED]; 306 timeouts[GRE_CT_REPLIED] = net_gre->gre_timeouts[GRE_CT_REPLIED]; 307 308 if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) { 309 timeouts[GRE_CT_UNREPLIED] = 310 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ; 311 } 312 if (tb[CTA_TIMEOUT_GRE_REPLIED]) { 313 timeouts[GRE_CT_REPLIED] = 314 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ; 315 } 316 return 0; 317 } 318 319 static int 320 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data) 321 { 322 const unsigned int *timeouts = data; 323 324 if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED, 325 htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) || 326 nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED, 327 htonl(timeouts[GRE_CT_REPLIED] / HZ))) 328 goto nla_put_failure; 329 return 0; 330 331 nla_put_failure: 332 return -ENOSPC; 333 } 334 335 static const struct nla_policy 336 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = { 337 [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 }, 338 [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 }, 339 }; 340 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */ 341 342 static int gre_init_net(struct net *net, u_int16_t proto) 343 { 344 struct netns_proto_gre *net_gre = gre_pernet(net); 345 int i; 346 347 rwlock_init(&net_gre->keymap_lock); 348 INIT_LIST_HEAD(&net_gre->keymap_list); 349 for (i = 0; i < GRE_CT_MAX; i++) 350 net_gre->gre_timeouts[i] = gre_timeouts[i]; 351 352 return 0; 353 } 354 355 /* protocol helper struct */ 356 static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 __read_mostly = { 357 .l3proto = AF_INET, 358 .l4proto = IPPROTO_GRE, 359 .pkt_to_tuple = gre_pkt_to_tuple, 360 .invert_tuple = gre_invert_tuple, 361 #ifdef CONFIG_NF_CONNTRACK_PROCFS 362 .print_conntrack = gre_print_conntrack, 363 #endif 364 .get_timeouts = gre_get_timeouts, 365 .packet = gre_packet, 366 .new = gre_new, 367 .destroy = gre_destroy, 368 .me = THIS_MODULE, 369 #if IS_ENABLED(CONFIG_NF_CT_NETLINK) 370 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr, 371 .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size, 372 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple, 373 .nla_policy = nf_ct_port_nla_policy, 374 #endif 375 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT) 376 .ctnl_timeout = { 377 .nlattr_to_obj = gre_timeout_nlattr_to_obj, 378 .obj_to_nlattr = gre_timeout_obj_to_nlattr, 379 .nlattr_max = CTA_TIMEOUT_GRE_MAX, 380 .obj_size = sizeof(unsigned int) * GRE_CT_MAX, 381 .nla_policy = gre_timeout_nla_policy, 382 }, 383 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */ 384 .net_id = &proto_gre_net_id, 385 .init_net = gre_init_net, 386 }; 387 388 static int proto_gre_net_init(struct net *net) 389 { 390 int ret = 0; 391 392 ret = nf_ct_l4proto_pernet_register_one(net, 393 &nf_conntrack_l4proto_gre4); 394 if (ret < 0) 395 pr_err("nf_conntrack_gre4: pernet registration failed.\n"); 396 return ret; 397 } 398 399 static void proto_gre_net_exit(struct net *net) 400 { 401 nf_ct_l4proto_pernet_unregister_one(net, &nf_conntrack_l4proto_gre4); 402 nf_ct_gre_keymap_flush(net); 403 } 404 405 static struct pernet_operations proto_gre_net_ops = { 406 .init = proto_gre_net_init, 407 .exit = proto_gre_net_exit, 408 .id = &proto_gre_net_id, 409 .size = sizeof(struct netns_proto_gre), 410 }; 411 412 static int __init nf_ct_proto_gre_init(void) 413 { 414 int ret; 415 416 ret = register_pernet_subsys(&proto_gre_net_ops); 417 if (ret < 0) 418 goto out_pernet; 419 ret = nf_ct_l4proto_register_one(&nf_conntrack_l4proto_gre4); 420 if (ret < 0) 421 goto out_gre4; 422 423 return 0; 424 out_gre4: 425 unregister_pernet_subsys(&proto_gre_net_ops); 426 out_pernet: 427 return ret; 428 } 429 430 static void __exit nf_ct_proto_gre_fini(void) 431 { 432 nf_ct_l4proto_unregister_one(&nf_conntrack_l4proto_gre4); 433 unregister_pernet_subsys(&proto_gre_net_ops); 434 } 435 436 module_init(nf_ct_proto_gre_init); 437 module_exit(nf_ct_proto_gre_fini); 438 439 MODULE_LICENSE("GPL"); 440