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 by Pablo Neira Ayuso <pablo@eurodev.net>
   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/major.h>
  22 #include <linux/timer.h>
  23 #include <linux/string.h>
  24 #include <linux/sockios.h>
  25 #include <linux/net.h>
  26 #include <linux/fcntl.h>
  27 #include <linux/skbuff.h>
  28 #include <asm/uaccess.h>
  29 #include <asm/system.h>
  30 #include <net/sock.h>
  31 #include <net/netlink.h>
  32 #include <linux/init.h>
  33 #include <linux/spinlock.h>
  34
  35 #include <linux/netfilter.h>
  36 #include <linux/netlink.h>
  37 #include <linux/netfilter/nfnetlink.h>
  38
  39 MODULE_LICENSE("GPL");
  40 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  41 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
  42
  43 static char __initdata nfversion[] = "0.30";
  44
  45 #if 0
  46 #define DEBUGP(format, args...) \
  47                 printk(KERN_DEBUG "%s(%d):%s(): " format, __FILE__, \
  48                         __LINE__, __FUNCTION__, ## args)
  49 #else
  50 #define DEBUGP(format, args...)
  51 #endif
  52
  53 static struct sock *nfnl = NULL;
  54 static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
  55 static DEFINE_MUTEX(nfnl_mutex);
  56
  57 static void nfnl_lock(void)
  58 {
  59         mutex_lock(&nfnl_mutex);
  60 }
  61
  62 static int nfnl_trylock(void)
  63 {
  64         return !mutex_trylock(&nfnl_mutex);
  65 }
  66
  67 static void __nfnl_unlock(void)
  68 {
  69         mutex_unlock(&nfnl_mutex);
  70 }
  71
  72 static void nfnl_unlock(void)
  73 {
  74         mutex_unlock(&nfnl_mutex);
  75         if (nfnl->sk_receive_queue.qlen)
  76                 nfnl->sk_data_ready(nfnl, 0);
  77 }
  78
  79 int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
  80 {
  81         DEBUGP("registering subsystem ID %u\n", n->subsys_id);
  82
  83         nfnl_lock();
  84         if (subsys_table[n->subsys_id]) {
  85                 nfnl_unlock();
  86                 return -EBUSY;
  87         }
  88         subsys_table[n->subsys_id] = n;
  89         nfnl_unlock();
  90
  91         return 0;
  92 }
  93
  94 int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
  95 {
  96         DEBUGP("unregistering subsystem ID %u\n", n->subsys_id);
  97
  98         nfnl_lock();
  99         subsys_table[n->subsys_id] = NULL;
 100         nfnl_unlock();
 101
 102         return 0;
 103 }
 104
 105 static inline struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
 106 {
 107         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
 108
 109         if (subsys_id >= NFNL_SUBSYS_COUNT
 110             || subsys_table[subsys_id] == NULL)
 111                 return NULL;
 112
 113         return subsys_table[subsys_id];
 114 }
 115
 116 static inline struct nfnl_callback *
 117 nfnetlink_find_client(u_int16_t type, struct nfnetlink_subsystem *ss)
 118 {
 119         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 120
 121         if (cb_id >= ss->cb_count) {
 122                 DEBUGP("msgtype %u >= %u, returning\n", type, ss->cb_count);
 123                 return NULL;
 124         }
 125
 126         return &ss->cb[cb_id];
 127 }
 128
 129 void __nfa_fill(struct sk_buff *skb, int attrtype, int attrlen,
 130                 const void *data)
 131 {
 132         struct nfattr *nfa;
 133         int size = NFA_LENGTH(attrlen);
 134
 135         nfa = (struct nfattr *)skb_put(skb, NFA_ALIGN(size));
 136         nfa->nfa_type = attrtype;
 137         nfa->nfa_len  = size;
 138         memcpy(NFA_DATA(nfa), data, attrlen);
 139         memset(NFA_DATA(nfa) + attrlen, 0, NFA_ALIGN(size) - size);
 140 }
 141
 142 void nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
 143 {
 144         memset(tb, 0, sizeof(struct nfattr *) * maxattr);
 145
 146         while (NFA_OK(nfa, len)) {
 147                 unsigned flavor = NFA_TYPE(nfa);
 148                 if (flavor && flavor <= maxattr)
 149                         tb[flavor-1] = nfa;
 150                 nfa = NFA_NEXT(nfa, len);
 151         }
 152 }
 153
 154 /**
 155  * nfnetlink_check_attributes - check and parse nfnetlink attributes
 156  *
 157  * subsys: nfnl subsystem for which this message is to be parsed
 158  * nlmsghdr: netlink message to be checked/parsed
 159  * cda: array of pointers, needs to be at least subsys->attr_count big
 160  *
 161  */
 162 static int
 163 nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
 164                            struct nlmsghdr *nlh, struct nfattr *cda[])
 165 {
 166         int min_len;
 167         u_int16_t attr_count;
 168         u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 169
 170         if (unlikely(cb_id >= subsys->cb_count)) {
 171                 DEBUGP("msgtype %u >= %u, returning\n",
 172                         cb_id, subsys->cb_count);
 173                 return -EINVAL;
 174         }
 175
 176         min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 177         if (unlikely(nlh->nlmsg_len < min_len))
 178                 return -EINVAL;
 179
 180         attr_count = subsys->cb[cb_id].attr_count;
 181         memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 182
 183         /* check attribute lengths. */
 184         if (likely(nlh->nlmsg_len > min_len)) {
 185                 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
 186                 int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 187
 188                 while (NFA_OK(attr, attrlen)) {
 189                         unsigned flavor = NFA_TYPE(attr);
 190                         if (flavor) {
 191                                 if (flavor > attr_count)
 192                                         return -EINVAL;
 193                                 cda[flavor - 1] = attr;
 194                         }
 195                         attr = NFA_NEXT(attr, attrlen);
 196                 }
 197         }
 198
 199         /* implicit: if nlmsg_len == min_len, we return 0, and an empty
 200          * (zeroed) cda[] array. The message is valid, but empty. */
 201
 202         return 0;
 203 }
 204
 205 int nfnetlink_has_listeners(unsigned int group)
 206 {
 207         return netlink_has_listeners(nfnl, group);
 208 }
 209 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 210
 211 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 212 {
 213         int err = 0;
 214
 215         NETLINK_CB(skb).dst_group = group;
 216         if (echo)
 217                 atomic_inc(&skb->users);
 218         netlink_broadcast(nfnl, skb, pid, group, gfp_any());
 219         if (echo)
 220                 err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
 221
 222         return err;
 223 }
 224
 225 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
 226 {
 227         return netlink_unicast(nfnl, skb, pid, flags);
 228 }
 229
 230 /* Process one complete nfnetlink message. */
 231 static int nfnetlink_rcv_msg(struct sk_buff *skb,
 232                                     struct nlmsghdr *nlh, int *errp)
 233 {
 234         struct nfnl_callback *nc;
 235         struct nfnetlink_subsystem *ss;
 236         int type, err = 0;
 237
 238         DEBUGP("entered; subsys=%u, msgtype=%u\n",
 239                  NFNL_SUBSYS_ID(nlh->nlmsg_type),
 240                  NFNL_MSG_TYPE(nlh->nlmsg_type));
 241
 242         if (security_netlink_recv(skb, CAP_NET_ADMIN)) {
 243                 DEBUGP("missing CAP_NET_ADMIN\n");
 244                 *errp = -EPERM;
 245                 return -1;
 246         }
 247
 248         /* Only requests are handled by kernel now. */
 249         if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
 250                 DEBUGP("received non-request message\n");
 251                 return 0;
 252         }
 253
 254         /* All the messages must at least contain nfgenmsg */
 255         if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg))) {
 256                 DEBUGP("received message was too short\n");
 257                 return 0;
 258         }
 259
 260         type = nlh->nlmsg_type;
 261         ss = nfnetlink_get_subsys(type);
 262         if (!ss) {
 263 #ifdef CONFIG_KMOD
 264                 /* don't call nfnl_unlock, since it would reenter
 265                  * with further packet processing */
 266                 __nfnl_unlock();
 267                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 268                 nfnl_lock();
 269                 ss = nfnetlink_get_subsys(type);
 270                 if (!ss)
 271 #endif
 272                         goto err_inval;
 273         }
 274
 275         nc = nfnetlink_find_client(type, ss);
 276         if (!nc) {
 277                 DEBUGP("unable to find client for type %d\n", type);
 278                 goto err_inval;
 279         }
 280
 281         {
 282                 u_int16_t attr_count =
 283                         ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count;
 284                 struct nfattr *cda[attr_count];
 285
 286                 memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 287
 288                 err = nfnetlink_check_attributes(ss, nlh, cda);
 289                 if (err < 0)
 290                         goto err_inval;
 291
 292                 DEBUGP("calling handler\n");
 293                 err = nc->call(nfnl, skb, nlh, cda, errp);
 294                 *errp = err;
 295                 return err;
 296         }
 297
 298 err_inval:
 299         DEBUGP("returning -EINVAL\n");
 300         *errp = -EINVAL;
 301         return -1;
 302 }
 303
 304 static void nfnetlink_rcv(struct sock *sk, int len)
 305 {
 306         unsigned int qlen = 0;
 307
 308         do {
 309                 if (nfnl_trylock())
 310                         return;
 311                 netlink_run_queue(sk, &qlen, nfnetlink_rcv_msg);
 312                 __nfnl_unlock();
 313         } while (qlen);
 314 }
 315
 316 static void __exit nfnetlink_exit(void)
 317 {
 318         printk("Removing netfilter NETLINK layer.\n");
 319         sock_release(nfnl->sk_socket);
 320         return;
 321 }
 322
 323 static int __init nfnetlink_init(void)
 324 {
 325         printk("Netfilter messages via NETLINK v%s.\n", nfversion);
 326
 327         nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX,
 328                                      nfnetlink_rcv, THIS_MODULE);
 329         if (!nfnl) {
 330                 printk(KERN_ERR "cannot initialize nfnetlink!\n");
 331                 return -1;
 332         }
 333
 334         return 0;
 335 }
 336
 337 module_init(nfnetlink_init);
 338 module_exit(nfnetlink_exit);
 339
 340 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
 341 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
 342 EXPORT_SYMBOL_GPL(nfnetlink_send);
 343 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 344 EXPORT_SYMBOL_GPL(nfattr_parse);
 345 EXPORT_SYMBOL_GPL(__nfa_fill);