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
  34 #include <linux/netlink.h>
  35 #include <linux/netfilter/nfnetlink.h>
  36
  37 MODULE_LICENSE("GPL");
  38 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  39 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
  40
  41 static char __initdata nfversion[] = "0.30";
  42
  43 static struct sock *nfnl = NULL;
  44 static const struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
  45 static DEFINE_MUTEX(nfnl_mutex);
  46
  47 static inline void nfnl_lock(void)
  48 {
  49         mutex_lock(&nfnl_mutex);
  50 }
  51
  52 static inline void nfnl_unlock(void)
  53 {
  54         mutex_unlock(&nfnl_mutex);
  55 }
  56
  57 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
  58 {
  59         nfnl_lock();
  60         if (subsys_table[n->subsys_id]) {
  61                 nfnl_unlock();
  62                 return -EBUSY;
  63         }
  64         subsys_table[n->subsys_id] = n;
  65         nfnl_unlock();
  66
  67         return 0;
  68 }
  69 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  70
  71 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
  72 {
  73         nfnl_lock();
  74         subsys_table[n->subsys_id] = NULL;
  75         nfnl_unlock();
  76
  77         return 0;
  78 }
  79 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
  80
  81 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  82 {
  83         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  84
  85         if (subsys_id >= NFNL_SUBSYS_COUNT)
  86                 return NULL;
  87
  88         return subsys_table[subsys_id];
  89 }
  90
  91 static inline const struct nfnl_callback *
  92 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
  93 {
  94         u_int8_t cb_id = NFNL_MSG_TYPE(type);
  95
  96         if (cb_id >= ss->cb_count)
  97                 return NULL;
  98
  99         return &ss->cb[cb_id];
 100 }
 101
 102 int nfnetlink_has_listeners(unsigned int group)
 103 {
 104         return netlink_has_listeners(nfnl, group);
 105 }
 106 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 107
 108 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 109 {
 110         return nlmsg_notify(nfnl, skb, pid, group, echo, gfp_any());
 111 }
 112 EXPORT_SYMBOL_GPL(nfnetlink_send);
 113
 114 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
 115 {
 116         return netlink_unicast(nfnl, skb, pid, flags);
 117 }
 118 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 119
 120 /* Process one complete nfnetlink message. */
 121 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 122 {
 123         const struct nfnl_callback *nc;
 124         const struct nfnetlink_subsystem *ss;
 125         int type, err;
 126
 127         if (security_netlink_recv(skb, CAP_NET_ADMIN))
 128                 return -EPERM;
 129
 130         /* All the messages must at least contain nfgenmsg */
 131         if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg)))
 132                 return 0;
 133
 134         type = nlh->nlmsg_type;
 135         ss = nfnetlink_get_subsys(type);
 136         if (!ss) {
 137 #ifdef CONFIG_KMOD
 138                 nfnl_unlock();
 139                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 140                 nfnl_lock();
 141                 ss = nfnetlink_get_subsys(type);
 142                 if (!ss)
 143 #endif
 144                         return -EINVAL;
 145         }
 146
 147         nc = nfnetlink_find_client(type, ss);
 148         if (!nc)
 149                 return -EINVAL;
 150
 151         {
 152                 int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 153                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 154                 u_int16_t attr_count = ss->cb[cb_id].attr_count;
 155                 struct nlattr *cda[attr_count+1];
 156
 157                 if (likely(nlh->nlmsg_len >= min_len)) {
 158                         struct nlattr *attr = (void *)nlh + NLMSG_ALIGN(min_len);
 159                         int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 160
 161                         err = nla_parse(cda, attr_count, attr, attrlen,
 162                                         ss->cb[cb_id].policy);
 163                         if (err < 0)
 164                                 return err;
 165                 } else
 166                         return -EINVAL;
 167
 168                 return nc->call(nfnl, skb, nlh, cda);
 169         }
 170 }
 171
 172 static void nfnetlink_rcv(struct sk_buff *skb)
 173 {
 174         nfnl_lock();
 175         netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 176         nfnl_unlock();
 177 }
 178
 179 static void __exit nfnetlink_exit(void)
 180 {
 181         printk("Removing netfilter NETLINK layer.\n");
 182         sock_release(nfnl->sk_socket);
 183         return;
 184 }
 185
 186 static int __init nfnetlink_init(void)
 187 {
 188         printk("Netfilter messages via NETLINK v%s.\n", nfversion);
 189
 190         nfnl = netlink_kernel_create(&init_net, NETLINK_NETFILTER, NFNLGRP_MAX,
 191                                      nfnetlink_rcv, NULL, THIS_MODULE);
 192         if (!nfnl) {
 193                 printk(KERN_ERR "cannot initialize nfnetlink!\n");
 194                 return -1;
 195         }
 196
 197         return 0;
 198 }
 199
 200 module_init(nfnetlink_init);
 201 module_exit(nfnetlink_exit);