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 void nfnl_lock(void)
  48 {
  49         mutex_lock(&nfnl_mutex);
  50 }
  51 EXPORT_SYMBOL_GPL(nfnl_lock);
  52
  53 void nfnl_unlock(void)
  54 {
  55         mutex_unlock(&nfnl_mutex);
  56 }
  57 EXPORT_SYMBOL_GPL(nfnl_unlock);
  58
  59 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
  60 {
  61         nfnl_lock();
  62         if (subsys_table[n->subsys_id]) {
  63                 nfnl_unlock();
  64                 return -EBUSY;
  65         }
  66         subsys_table[n->subsys_id] = n;
  67         nfnl_unlock();
  68
  69         return 0;
  70 }
  71 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  72
  73 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
  74 {
  75         nfnl_lock();
  76         subsys_table[n->subsys_id] = NULL;
  77         nfnl_unlock();
  78
  79         return 0;
  80 }
  81 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
  82
  83 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  84 {
  85         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  86
  87         if (subsys_id >= NFNL_SUBSYS_COUNT)
  88                 return NULL;
  89
  90         return subsys_table[subsys_id];
  91 }
  92
  93 static inline const struct nfnl_callback *
  94 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
  95 {
  96         u_int8_t cb_id = NFNL_MSG_TYPE(type);
  97
  98         if (cb_id >= ss->cb_count)
  99                 return NULL;
 100
 101         return &ss->cb[cb_id];
 102 }
 103
 104 int nfnetlink_has_listeners(unsigned int group)
 105 {
 106         return netlink_has_listeners(nfnl, group);
 107 }
 108 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 109
 110 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 111 {
 112         return nlmsg_notify(nfnl, skb, pid, group, echo, gfp_any());
 113 }
 114 EXPORT_SYMBOL_GPL(nfnetlink_send);
 115
 116 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
 117 {
 118         return netlink_unicast(nfnl, skb, pid, flags);
 119 }
 120 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 121
 122 /* Process one complete nfnetlink message. */
 123 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 124 {
 125         const struct nfnl_callback *nc;
 126         const struct nfnetlink_subsystem *ss;
 127         int type, err;
 128
 129         if (security_netlink_recv(skb, CAP_NET_ADMIN))
 130                 return -EPERM;
 131
 132         /* All the messages must at least contain nfgenmsg */
 133         if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg)))
 134                 return 0;
 135
 136         type = nlh->nlmsg_type;
 137 replay:
 138         ss = nfnetlink_get_subsys(type);
 139         if (!ss) {
 140 #ifdef CONFIG_MODULES
 141                 nfnl_unlock();
 142                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 143                 nfnl_lock();
 144                 ss = nfnetlink_get_subsys(type);
 145                 if (!ss)
 146 #endif
 147                         return -EINVAL;
 148         }
 149
 150         nc = nfnetlink_find_client(type, ss);
 151         if (!nc)
 152                 return -EINVAL;
 153
 154         {
 155                 int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 156                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 157                 u_int16_t attr_count = ss->cb[cb_id].attr_count;
 158                 struct nlattr *cda[attr_count+1];
 159
 160                 if (likely(nlh->nlmsg_len >= min_len)) {
 161                         struct nlattr *attr = (void *)nlh + NLMSG_ALIGN(min_len);
 162                         int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 163
 164                         err = nla_parse(cda, attr_count, attr, attrlen,
 165                                         ss->cb[cb_id].policy);
 166                         if (err < 0)
 167                                 return err;
 168                 } else
 169                         return -EINVAL;
 170
 171                 err = nc->call(nfnl, skb, nlh, cda);
 172                 if (err == -EAGAIN)
 173                         goto replay;
 174                 return err;
 175         }
 176 }
 177
 178 static void nfnetlink_rcv(struct sk_buff *skb)
 179 {
 180         nfnl_lock();
 181         netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 182         nfnl_unlock();
 183 }
 184
 185 static void __exit nfnetlink_exit(void)
 186 {
 187         printk("Removing netfilter NETLINK layer.\n");
 188         netlink_kernel_release(nfnl);
 189         return;
 190 }
 191
 192 static int __init nfnetlink_init(void)
 193 {
 194         printk("Netfilter messages via NETLINK v%s.\n", nfversion);
 195
 196         nfnl = netlink_kernel_create(&init_net, NETLINK_NETFILTER, NFNLGRP_MAX,
 197                                      nfnetlink_rcv, NULL, THIS_MODULE);
 198         if (!nfnl) {
 199                 printk(KERN_ERR "cannot initialize nfnetlink!\n");
 200                 return -1;
 201         }
 202
 203         return 0;
 204 }
 205
 206 module_init(nfnetlink_init);
 207 module_exit(nfnetlink_exit);