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