net/netfilter/nfnetlink.c

   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 #ifdef CONFIG_PROVE_LOCKING
  65 int lockdep_nfnl_is_held(u8 subsys_id)
  66 {
  67         return lockdep_is_held(&table[subsys_id].mutex);
  68 }
  69 EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held);
  70 #endif
  71
  72 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
  73 {
  74         nfnl_lock(n->subsys_id);
  75         if (table[n->subsys_id].subsys) {
  76                 nfnl_unlock(n->subsys_id);
  77                 return -EBUSY;
  78         }
  79         rcu_assign_pointer(table[n->subsys_id].subsys, n);
  80         nfnl_unlock(n->subsys_id);
  81
  82         return 0;
  83 }
  84 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  85
  86 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
  87 {
  88         nfnl_lock(n->subsys_id);
  89         table[n->subsys_id].subsys = NULL;
  90         nfnl_unlock(n->subsys_id);
  91         synchronize_rcu();
  92         return 0;
  93 }
  94 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
  95
  96 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  97 {
  98         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  99
 100         if (subsys_id >= NFNL_SUBSYS_COUNT)
 101                 return NULL;
 102
 103         return rcu_dereference(table[subsys_id].subsys);
 104 }
 105
 106 static inline const struct nfnl_callback *
 107 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
 108 {
 109         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 110
 111         if (cb_id >= ss->cb_count)
 112                 return NULL;
 113
 114         return &ss->cb[cb_id];
 115 }
 116
 117 int nfnetlink_has_listeners(struct net *net, unsigned int group)
 118 {
 119         return netlink_has_listeners(net->nfnl, group);
 120 }
 121 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 122
 123 struct sk_buff *nfnetlink_alloc_skb(struct net *net, unsigned int size,
 124                                     u32 dst_portid, gfp_t gfp_mask)
 125 {
 126         return netlink_alloc_skb(net->nfnl, size, dst_portid, gfp_mask);
 127 }
 128 EXPORT_SYMBOL_GPL(nfnetlink_alloc_skb);
 129
 130 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
 131                    unsigned int group, int echo, gfp_t flags)
 132 {
 133         return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
 134 }
 135 EXPORT_SYMBOL_GPL(nfnetlink_send);
 136
 137 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
 138 {
 139         return netlink_set_err(net->nfnl, portid, group, error);
 140 }
 141 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
 142
 143 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
 144                       int flags)
 145 {
 146         return netlink_unicast(net->nfnl, skb, portid, flags);
 147 }
 148 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 149
 150 /* Process one complete nfnetlink message. */
 151 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 152 {
 153         struct net *net = sock_net(skb->sk);
 154         const struct nfnl_callback *nc;
 155         const struct nfnetlink_subsystem *ss;
 156         int type, err;
 157
 158         /* All the messages must at least contain nfgenmsg */
 159         if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
 160                 return 0;
 161
 162         type = nlh->nlmsg_type;
 163 replay:
 164         rcu_read_lock();
 165         ss = nfnetlink_get_subsys(type);
 166         if (!ss) {
 167 #ifdef CONFIG_MODULES
 168                 rcu_read_unlock();
 169                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 170                 rcu_read_lock();
 171                 ss = nfnetlink_get_subsys(type);
 172                 if (!ss)
 173 #endif
 174                 {
 175                         rcu_read_unlock();
 176                         return -EINVAL;
 177                 }
 178         }
 179
 180         nc = nfnetlink_find_client(type, ss);
 181         if (!nc) {
 182                 rcu_read_unlock();
 183                 return -EINVAL;
 184         }
 185
 186         {
 187                 int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 188                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 189                 struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 190                 struct nlattr *attr = (void *)nlh + min_len;
 191                 int attrlen = nlh->nlmsg_len - min_len;
 192                 __u8 subsys_id = NFNL_SUBSYS_ID(type);
 193
 194                 err = nla_parse(cda, ss->cb[cb_id].attr_count,
 195                                 attr, attrlen, ss->cb[cb_id].policy);
 196                 if (err < 0) {
 197                         rcu_read_unlock();
 198                         return err;
 199                 }
 200
 201                 if (nc->call_rcu) {
 202                         err = nc->call_rcu(net->nfnl, skb, nlh,
 203                                            (const struct nlattr **)cda);
 204                         rcu_read_unlock();
 205                 } else {
 206                         rcu_read_unlock();
 207                         nfnl_lock(subsys_id);
 208                         if (rcu_dereference_protected(table[subsys_id].subsys,
 209                                 lockdep_is_held(&table[subsys_id].mutex)) != ss ||
 210                             nfnetlink_find_client(type, ss) != nc)
 211                                 err = -EAGAIN;
 212                         else if (nc->call)
 213                                 err = nc->call(net->nfnl, skb, nlh,
 214                                                    (const struct nlattr **)cda);
 215                         else
 216                                 err = -EINVAL;
 217                         nfnl_unlock(subsys_id);
 218                 }
 219                 if (err == -EAGAIN)
 220                         goto replay;
 221                 return err;
 222         }
 223 }
 224
 225 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
 226                                 u_int16_t subsys_id)
 227 {
 228         struct sk_buff *nskb, *oskb = skb;
 229         struct net *net = sock_net(skb->sk);
 230         const struct nfnetlink_subsystem *ss;
 231         const struct nfnl_callback *nc;
 232         bool success = true, done = false;
 233         int err;
 234
 235         if (subsys_id >= NFNL_SUBSYS_COUNT)
 236                 return netlink_ack(skb, nlh, -EINVAL);
 237 replay:
 238         nskb = netlink_skb_clone(oskb, GFP_KERNEL);
 239         if (!nskb)
 240                 return netlink_ack(oskb, nlh, -ENOMEM);
 241
 242         nskb->sk = oskb->sk;
 243         skb = nskb;
 244
 245         nfnl_lock(subsys_id);
 246         ss = rcu_dereference_protected(table[subsys_id].subsys,
 247                                        lockdep_is_held(&table[subsys_id].mutex));
 248         if (!ss) {
 249 #ifdef CONFIG_MODULES
 250                 nfnl_unlock(subsys_id);
 251                 request_module("nfnetlink-subsys-%d", subsys_id);
 252                 nfnl_lock(subsys_id);
 253                 ss = rcu_dereference_protected(table[subsys_id].subsys,
 254                                                lockdep_is_held(&table[subsys_id].mutex));
 255                 if (!ss)
 256 #endif
 257                 {
 258                         nfnl_unlock(subsys_id);
 259                         netlink_ack(skb, nlh, -EOPNOTSUPP);
 260                         return kfree_skb(nskb);
 261                 }
 262         }
 263
 264         if (!ss->commit || !ss->abort) {
 265                 nfnl_unlock(subsys_id);
 266                 netlink_ack(skb, nlh, -EOPNOTSUPP);
 267                 return kfree_skb(skb);
 268         }
 269
 270         while (skb->len >= nlmsg_total_size(0)) {
 271                 int msglen, type;
 272
 273                 nlh = nlmsg_hdr(skb);
 274                 err = 0;
 275
 276                 if (nlh->nlmsg_len < NLMSG_HDRLEN) {
 277                         err = -EINVAL;
 278                         goto ack;
 279                 }
 280
 281                 /* Only requests are handled by the kernel */
 282                 if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
 283                         err = -EINVAL;
 284                         goto ack;
 285                 }
 286
 287                 type = nlh->nlmsg_type;
 288                 if (type == NFNL_MSG_BATCH_BEGIN) {
 289                         /* Malformed: Batch begin twice */
 290                         success = false;
 291                         goto done;
 292                 } else if (type == NFNL_MSG_BATCH_END) {
 293                         done = true;
 294                         goto done;
 295                 } else if (type < NLMSG_MIN_TYPE) {
 296                         err = -EINVAL;
 297                         goto ack;
 298                 }
 299
 300                 /* We only accept a batch with messages for the same
 301                  * subsystem.
 302                  */
 303                 if (NFNL_SUBSYS_ID(type) != subsys_id) {
 304                         err = -EINVAL;
 305                         goto ack;
 306                 }
 307
 308                 nc = nfnetlink_find_client(type, ss);
 309                 if (!nc) {
 310                         err = -EINVAL;
 311                         goto ack;
 312                 }
 313
 314                 {
 315                         int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 316                         u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 317                         struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 318                         struct nlattr *attr = (void *)nlh + min_len;
 319                         int attrlen = nlh->nlmsg_len - min_len;
 320
 321                         err = nla_parse(cda, ss->cb[cb_id].attr_count,
 322                                         attr, attrlen, ss->cb[cb_id].policy);
 323                         if (err < 0)
 324                                 goto ack;
 325
 326                         if (nc->call_batch) {
 327                                 err = nc->call_batch(net->nfnl, skb, nlh,
 328                                                      (const struct nlattr **)cda);
 329                         }
 330
 331                         /* The lock was released to autoload some module, we
 332                          * have to abort and start from scratch using the
 333                          * original skb.
 334                          */
 335                         if (err == -EAGAIN) {
 336                                 ss->abort(skb);
 337                                 nfnl_unlock(subsys_id);
 338                                 kfree_skb(nskb);
 339                                 goto replay;
 340                         }
 341                 }
 342 ack:
 343                 if (nlh->nlmsg_flags & NLM_F_ACK || err) {
 344                         /* We don't stop processing the batch on errors, thus,
 345                          * userspace gets all the errors that the batch
 346                          * triggers.
 347                          */
 348                         netlink_ack(skb, nlh, err);
 349                         if (err)
 350                                 success = false;
 351                 }
 352
 353                 msglen = NLMSG_ALIGN(nlh->nlmsg_len);
 354                 if (msglen > skb->len)
 355                         msglen = skb->len;
 356                 skb_pull(skb, msglen);
 357         }
 358 done:
 359         if (success && done)
 360                 ss->commit(skb);
 361         else
 362                 ss->abort(skb);
 363
 364         nfnl_unlock(subsys_id);
 365         kfree_skb(nskb);
 366 }
 367
 368 static void nfnetlink_rcv(struct sk_buff *skb)
 369 {
 370         struct nlmsghdr *nlh = nlmsg_hdr(skb);
 371         int msglen;
 372
 373         if (nlh->nlmsg_len < NLMSG_HDRLEN ||
 374             skb->len < nlh->nlmsg_len)
 375                 return;
 376
 377         if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
 378                 netlink_ack(skb, nlh, -EPERM);
 379                 return;
 380         }
 381
 382         if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN) {
 383                 struct nfgenmsg *nfgenmsg;
 384
 385                 msglen = NLMSG_ALIGN(nlh->nlmsg_len);
 386                 if (msglen > skb->len)
 387                         msglen = skb->len;
 388
 389                 if (nlh->nlmsg_len < NLMSG_HDRLEN ||
 390                     skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
 391                         return;
 392
 393                 nfgenmsg = nlmsg_data(nlh);
 394                 skb_pull(skb, msglen);
 395                 nfnetlink_rcv_batch(skb, nlh, nfgenmsg->res_id);
 396         } else {
 397                 netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 398         }
 399 }
 400
 401 #ifdef CONFIG_MODULES
 402 static int nfnetlink_bind(int group)
 403 {
 404         const struct nfnetlink_subsystem *ss;
 405         int type = nfnl_group2type[group];
 406
 407         rcu_read_lock();
 408         ss = nfnetlink_get_subsys(type);
 409         rcu_read_unlock();
 410         if (!ss)
 411                 request_module("nfnetlink-subsys-%d", type);
 412         return 0;
 413 }
 414 #endif
 415
 416 static int __net_init nfnetlink_net_init(struct net *net)
 417 {
 418         struct sock *nfnl;
 419         struct netlink_kernel_cfg cfg = {
 420                 .groups = NFNLGRP_MAX,
 421                 .input  = nfnetlink_rcv,
 422 #ifdef CONFIG_MODULES
 423                 .bind   = nfnetlink_bind,
 424 #endif
 425         };
 426
 427         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
 428         if (!nfnl)
 429                 return -ENOMEM;
 430         net->nfnl_stash = nfnl;
 431         rcu_assign_pointer(net->nfnl, nfnl);
 432         return 0;
 433 }
 434
 435 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 436 {
 437         struct net *net;
 438
 439         list_for_each_entry(net, net_exit_list, exit_list)
 440                 RCU_INIT_POINTER(net->nfnl, NULL);
 441         synchronize_net();
 442         list_for_each_entry(net, net_exit_list, exit_list)
 443                 netlink_kernel_release(net->nfnl_stash);
 444 }
 445
 446 static struct pernet_operations nfnetlink_net_ops = {
 447         .init           = nfnetlink_net_init,
 448         .exit_batch     = nfnetlink_net_exit_batch,
 449 };
 450
 451 static int __init nfnetlink_init(void)
 452 {
 453         int i;
 454
 455         for (i=0; i<NFNL_SUBSYS_COUNT; i++)
 456                 mutex_init(&table[i].mutex);
 457
 458         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 459         return register_pernet_subsys(&nfnetlink_net_ops);
 460 }
 461
 462 static void __exit nfnetlink_exit(void)
 463 {
 464         pr_info("Removing netfilter NETLINK layer.\n");
 465         unregister_pernet_subsys(&nfnetlink_net_ops);
 466 }
 467 module_init(nfnetlink_init);
 468 module_exit(nfnetlink_exit);