1 /* Netfilter messages via netlink socket. Allows for user space 2 * protocol helpers and general trouble making from userspace. 3 * 4 * (C) 2001 by Jay Schulist <jschlst@samba.org>, 5 * (C) 2002-2005 by Harald Welte <laforge@gnumonks.org> 6 * (C) 2005,2007 by Pablo Neira Ayuso <pablo@netfilter.org> 7 * 8 * Initial netfilter messages via netlink development funded and 9 * generally made possible by Network Robots, Inc. (www.networkrobots.com) 10 * 11 * Further development of this code funded by Astaro AG (http://www.astaro.com) 12 * 13 * This software may be used and distributed according to the terms 14 * of the GNU General Public License, incorporated herein by reference. 15 */ 16 17 #include <linux/module.h> 18 #include <linux/types.h> 19 #include <linux/socket.h> 20 #include <linux/kernel.h> 21 #include <linux/string.h> 22 #include <linux/sockios.h> 23 #include <linux/net.h> 24 #include <linux/skbuff.h> 25 #include <asm/uaccess.h> 26 #include <net/sock.h> 27 #include <linux/init.h> 28 29 #include <net/netlink.h> 30 #include <linux/netfilter/nfnetlink.h> 31 32 MODULE_LICENSE("GPL"); 33 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 34 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER); 35 36 static char __initdata nfversion[] = "0.30"; 37 38 static struct { 39 struct mutex mutex; 40 const struct nfnetlink_subsystem __rcu *subsys; 41 } table[NFNL_SUBSYS_COUNT]; 42 43 static const int nfnl_group2type[NFNLGRP_MAX+1] = { 44 [NFNLGRP_CONNTRACK_NEW] = NFNL_SUBSYS_CTNETLINK, 45 [NFNLGRP_CONNTRACK_UPDATE] = NFNL_SUBSYS_CTNETLINK, 46 [NFNLGRP_CONNTRACK_DESTROY] = NFNL_SUBSYS_CTNETLINK, 47 [NFNLGRP_CONNTRACK_EXP_NEW] = NFNL_SUBSYS_CTNETLINK_EXP, 48 [NFNLGRP_CONNTRACK_EXP_UPDATE] = NFNL_SUBSYS_CTNETLINK_EXP, 49 [NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP, 50 }; 51 52 void nfnl_lock(__u8 subsys_id) 53 { 54 mutex_lock(&table[subsys_id].mutex); 55 } 56 EXPORT_SYMBOL_GPL(nfnl_lock); 57 58 void nfnl_unlock(__u8 subsys_id) 59 { 60 mutex_unlock(&table[subsys_id].mutex); 61 } 62 EXPORT_SYMBOL_GPL(nfnl_unlock); 63 64 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n) 65 { 66 nfnl_lock(n->subsys_id); 67 if (table[n->subsys_id].subsys) { 68 nfnl_unlock(n->subsys_id); 69 return -EBUSY; 70 } 71 rcu_assign_pointer(table[n->subsys_id].subsys, n); 72 nfnl_unlock(n->subsys_id); 73 74 return 0; 75 } 76 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register); 77 78 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n) 79 { 80 nfnl_lock(n->subsys_id); 81 table[n->subsys_id].subsys = NULL; 82 nfnl_unlock(n->subsys_id); 83 synchronize_rcu(); 84 return 0; 85 } 86 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister); 87 88 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type) 89 { 90 u_int8_t subsys_id = NFNL_SUBSYS_ID(type); 91 92 if (subsys_id >= NFNL_SUBSYS_COUNT) 93 return NULL; 94 95 return rcu_dereference(table[subsys_id].subsys); 96 } 97 98 static inline const struct nfnl_callback * 99 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss) 100 { 101 u_int8_t cb_id = NFNL_MSG_TYPE(type); 102 103 if (cb_id >= ss->cb_count) 104 return NULL; 105 106 return &ss->cb[cb_id]; 107 } 108 109 int nfnetlink_has_listeners(struct net *net, unsigned int group) 110 { 111 return netlink_has_listeners(net->nfnl, group); 112 } 113 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners); 114 115 struct sk_buff *nfnetlink_alloc_skb(struct net *net, unsigned int size, 116 u32 dst_portid, gfp_t gfp_mask) 117 { 118 return netlink_alloc_skb(net->nfnl, size, dst_portid, gfp_mask); 119 } 120 EXPORT_SYMBOL_GPL(nfnetlink_alloc_skb); 121 122 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid, 123 unsigned int group, int echo, gfp_t flags) 124 { 125 return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags); 126 } 127 EXPORT_SYMBOL_GPL(nfnetlink_send); 128 129 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error) 130 { 131 return netlink_set_err(net->nfnl, portid, group, error); 132 } 133 EXPORT_SYMBOL_GPL(nfnetlink_set_err); 134 135 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid, 136 int flags) 137 { 138 return netlink_unicast(net->nfnl, skb, portid, flags); 139 } 140 EXPORT_SYMBOL_GPL(nfnetlink_unicast); 141 142 /* Process one complete nfnetlink message. */ 143 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh) 144 { 145 struct net *net = sock_net(skb->sk); 146 const struct nfnl_callback *nc; 147 const struct nfnetlink_subsystem *ss; 148 int type, err; 149 150 /* All the messages must at least contain nfgenmsg */ 151 if (nlmsg_len(nlh) < sizeof(struct nfgenmsg)) 152 return 0; 153 154 type = nlh->nlmsg_type; 155 replay: 156 rcu_read_lock(); 157 ss = nfnetlink_get_subsys(type); 158 if (!ss) { 159 #ifdef CONFIG_MODULES 160 rcu_read_unlock(); 161 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type)); 162 rcu_read_lock(); 163 ss = nfnetlink_get_subsys(type); 164 if (!ss) 165 #endif 166 { 167 rcu_read_unlock(); 168 return -EINVAL; 169 } 170 } 171 172 nc = nfnetlink_find_client(type, ss); 173 if (!nc) { 174 rcu_read_unlock(); 175 return -EINVAL; 176 } 177 178 { 179 int min_len = nlmsg_total_size(sizeof(struct nfgenmsg)); 180 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type); 181 struct nlattr *cda[ss->cb[cb_id].attr_count + 1]; 182 struct nlattr *attr = (void *)nlh + min_len; 183 int attrlen = nlh->nlmsg_len - min_len; 184 __u8 subsys_id = NFNL_SUBSYS_ID(type); 185 186 err = nla_parse(cda, ss->cb[cb_id].attr_count, 187 attr, attrlen, ss->cb[cb_id].policy); 188 if (err < 0) { 189 rcu_read_unlock(); 190 return err; 191 } 192 193 if (nc->call_rcu) { 194 err = nc->call_rcu(net->nfnl, skb, nlh, 195 (const struct nlattr **)cda); 196 rcu_read_unlock(); 197 } else { 198 rcu_read_unlock(); 199 nfnl_lock(subsys_id); 200 if (rcu_dereference_protected(table[subsys_id].subsys, 201 lockdep_is_held(&table[subsys_id].mutex)) != ss || 202 nfnetlink_find_client(type, ss) != nc) 203 err = -EAGAIN; 204 else if (nc->call) 205 err = nc->call(net->nfnl, skb, nlh, 206 (const struct nlattr **)cda); 207 else 208 err = -EINVAL; 209 nfnl_unlock(subsys_id); 210 } 211 if (err == -EAGAIN) 212 goto replay; 213 return err; 214 } 215 } 216 217 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh, 218 u_int16_t subsys_id) 219 { 220 struct sk_buff *nskb, *oskb = skb; 221 struct net *net = sock_net(skb->sk); 222 const struct nfnetlink_subsystem *ss; 223 const struct nfnl_callback *nc; 224 bool success = true, done = false; 225 int err; 226 227 if (subsys_id >= NFNL_SUBSYS_COUNT) 228 return netlink_ack(skb, nlh, -EINVAL); 229 replay: 230 nskb = netlink_skb_clone(oskb, GFP_KERNEL); 231 if (!nskb) 232 return netlink_ack(oskb, nlh, -ENOMEM); 233 234 nskb->sk = oskb->sk; 235 skb = nskb; 236 237 nfnl_lock(subsys_id); 238 ss = rcu_dereference_protected(table[subsys_id].subsys, 239 lockdep_is_held(&table[subsys_id].mutex)); 240 if (!ss) { 241 #ifdef CONFIG_MODULES 242 nfnl_unlock(subsys_id); 243 request_module("nfnetlink-subsys-%d", subsys_id); 244 nfnl_lock(subsys_id); 245 ss = rcu_dereference_protected(table[subsys_id].subsys, 246 lockdep_is_held(&table[subsys_id].mutex)); 247 if (!ss) 248 #endif 249 { 250 nfnl_unlock(subsys_id); 251 kfree_skb(nskb); 252 return netlink_ack(skb, nlh, -EOPNOTSUPP); 253 } 254 } 255 256 if (!ss->commit || !ss->abort) { 257 nfnl_unlock(subsys_id); 258 kfree_skb(nskb); 259 return netlink_ack(skb, nlh, -EOPNOTSUPP); 260 } 261 262 while (skb->len >= nlmsg_total_size(0)) { 263 int msglen, type; 264 265 nlh = nlmsg_hdr(skb); 266 err = 0; 267 268 if (nlh->nlmsg_len < NLMSG_HDRLEN) { 269 err = -EINVAL; 270 goto ack; 271 } 272 273 /* Only requests are handled by the kernel */ 274 if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) { 275 err = -EINVAL; 276 goto ack; 277 } 278 279 type = nlh->nlmsg_type; 280 if (type == NFNL_MSG_BATCH_BEGIN) { 281 /* Malformed: Batch begin twice */ 282 success = false; 283 goto done; 284 } else if (type == NFNL_MSG_BATCH_END) { 285 done = true; 286 goto done; 287 } else if (type < NLMSG_MIN_TYPE) { 288 err = -EINVAL; 289 goto ack; 290 } 291 292 /* We only accept a batch with messages for the same 293 * subsystem. 294 */ 295 if (NFNL_SUBSYS_ID(type) != subsys_id) { 296 err = -EINVAL; 297 goto ack; 298 } 299 300 nc = nfnetlink_find_client(type, ss); 301 if (!nc) { 302 err = -EINVAL; 303 goto ack; 304 } 305 306 { 307 int min_len = nlmsg_total_size(sizeof(struct nfgenmsg)); 308 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type); 309 struct nlattr *cda[ss->cb[cb_id].attr_count + 1]; 310 struct nlattr *attr = (void *)nlh + min_len; 311 int attrlen = nlh->nlmsg_len - min_len; 312 313 err = nla_parse(cda, ss->cb[cb_id].attr_count, 314 attr, attrlen, ss->cb[cb_id].policy); 315 if (err < 0) 316 goto ack; 317 318 if (nc->call_batch) { 319 err = nc->call_batch(net->nfnl, skb, nlh, 320 (const struct nlattr **)cda); 321 } 322 323 /* The lock was released to autoload some module, we 324 * have to abort and start from scratch using the 325 * original skb. 326 */ 327 if (err == -EAGAIN) { 328 ss->abort(skb); 329 nfnl_unlock(subsys_id); 330 kfree_skb(nskb); 331 goto replay; 332 } 333 } 334 ack: 335 if (nlh->nlmsg_flags & NLM_F_ACK || err) { 336 /* We don't stop processing the batch on errors, thus, 337 * userspace gets all the errors that the batch 338 * triggers. 339 */ 340 netlink_ack(skb, nlh, err); 341 if (err) 342 success = false; 343 } 344 345 msglen = NLMSG_ALIGN(nlh->nlmsg_len); 346 if (msglen > skb->len) 347 msglen = skb->len; 348 skb_pull(skb, msglen); 349 } 350 done: 351 if (success && done) 352 ss->commit(skb); 353 else 354 ss->abort(skb); 355 356 nfnl_unlock(subsys_id); 357 kfree_skb(nskb); 358 } 359 360 static void nfnetlink_rcv(struct sk_buff *skb) 361 { 362 struct nlmsghdr *nlh = nlmsg_hdr(skb); 363 struct net *net = sock_net(skb->sk); 364 int msglen; 365 366 if (nlh->nlmsg_len < NLMSG_HDRLEN || 367 skb->len < nlh->nlmsg_len) 368 return; 369 370 if (!ns_capable(net->user_ns, CAP_NET_ADMIN)) { 371 netlink_ack(skb, nlh, -EPERM); 372 return; 373 } 374 375 if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN) { 376 struct nfgenmsg *nfgenmsg; 377 378 msglen = NLMSG_ALIGN(nlh->nlmsg_len); 379 if (msglen > skb->len) 380 msglen = skb->len; 381 382 if (nlh->nlmsg_len < NLMSG_HDRLEN || 383 skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg)) 384 return; 385 386 nfgenmsg = nlmsg_data(nlh); 387 skb_pull(skb, msglen); 388 nfnetlink_rcv_batch(skb, nlh, nfgenmsg->res_id); 389 } else { 390 netlink_rcv_skb(skb, &nfnetlink_rcv_msg); 391 } 392 } 393 394 #ifdef CONFIG_MODULES 395 static void nfnetlink_bind(int group) 396 { 397 const struct nfnetlink_subsystem *ss; 398 int type = nfnl_group2type[group]; 399 400 rcu_read_lock(); 401 ss = nfnetlink_get_subsys(type); 402 if (!ss) { 403 rcu_read_unlock(); 404 request_module("nfnetlink-subsys-%d", type); 405 return; 406 } 407 rcu_read_unlock(); 408 } 409 #endif 410 411 static int __net_init nfnetlink_net_init(struct net *net) 412 { 413 struct sock *nfnl; 414 struct netlink_kernel_cfg cfg = { 415 .groups = NFNLGRP_MAX, 416 .input = nfnetlink_rcv, 417 #ifdef CONFIG_MODULES 418 .bind = nfnetlink_bind, 419 #endif 420 }; 421 422 nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg); 423 if (!nfnl) 424 return -ENOMEM; 425 net->nfnl_stash = nfnl; 426 rcu_assign_pointer(net->nfnl, nfnl); 427 return 0; 428 } 429 430 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list) 431 { 432 struct net *net; 433 434 list_for_each_entry(net, net_exit_list, exit_list) 435 RCU_INIT_POINTER(net->nfnl, NULL); 436 synchronize_net(); 437 list_for_each_entry(net, net_exit_list, exit_list) 438 netlink_kernel_release(net->nfnl_stash); 439 } 440 441 static struct pernet_operations nfnetlink_net_ops = { 442 .init = nfnetlink_net_init, 443 .exit_batch = nfnetlink_net_exit_batch, 444 }; 445 446 static int __init nfnetlink_init(void) 447 { 448 int i; 449 450 for (i=0; i<NFNL_SUBSYS_COUNT; i++) 451 mutex_init(&table[i].mutex); 452 453 pr_info("Netfilter messages via NETLINK v%s.\n", nfversion); 454 return register_pernet_subsys(&nfnetlink_net_ops); 455 } 456 457 static void __exit nfnetlink_exit(void) 458 { 459 pr_info("Removing netfilter NETLINK layer.\n"); 460 unregister_pernet_subsys(&nfnetlink_net_ops); 461 } 462 module_init(nfnetlink_init); 463 module_exit(nfnetlink_exit); 464