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 <asm/system.h>
  27 #include <net/sock.h>
  28 #include <net/netlink.h>
  29 #include <linux/init.h>
  30
  31 #include <linux/netlink.h>
  32 #include <linux/netfilter/nfnetlink.h>
  33
  34 MODULE_LICENSE("GPL");
  35 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  36 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
  37
  38 static char __initdata nfversion[] = "0.30";
  39
  40 static const struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
  41 static DEFINE_MUTEX(nfnl_mutex);
  42
  43 void nfnl_lock(void)
  44 {
  45         mutex_lock(&nfnl_mutex);
  46 }
  47 EXPORT_SYMBOL_GPL(nfnl_lock);
  48
  49 void nfnl_unlock(void)
  50 {
  51         mutex_unlock(&nfnl_mutex);
  52 }
  53 EXPORT_SYMBOL_GPL(nfnl_unlock);
  54
  55 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
  56 {
  57         nfnl_lock();
  58         if (subsys_table[n->subsys_id]) {
  59                 nfnl_unlock();
  60                 return -EBUSY;
  61         }
  62         subsys_table[n->subsys_id] = n;
  63         nfnl_unlock();
  64
  65         return 0;
  66 }
  67 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  68
  69 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
  70 {
  71         nfnl_lock();
  72         subsys_table[n->subsys_id] = NULL;
  73         nfnl_unlock();
  74
  75         return 0;
  76 }
  77 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
  78
  79 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  80 {
  81         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  82
  83         if (subsys_id >= NFNL_SUBSYS_COUNT)
  84                 return NULL;
  85
  86         return subsys_table[subsys_id];
  87 }
  88
  89 static inline const struct nfnl_callback *
  90 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
  91 {
  92         u_int8_t cb_id = NFNL_MSG_TYPE(type);
  93
  94         if (cb_id >= ss->cb_count)
  95                 return NULL;
  96
  97         return &ss->cb[cb_id];
  98 }
  99
 100 int nfnetlink_has_listeners(struct net *net, unsigned int group)
 101 {
 102         return netlink_has_listeners(net->nfnl, group);
 103 }
 104 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 105
 106 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 pid,
 107                    unsigned group, int echo, gfp_t flags)
 108 {
 109         return nlmsg_notify(net->nfnl, skb, pid, group, echo, flags);
 110 }
 111 EXPORT_SYMBOL_GPL(nfnetlink_send);
 112
 113 int nfnetlink_set_err(struct net *net, u32 pid, u32 group, int error)
 114 {
 115         return netlink_set_err(net->nfnl, pid, group, error);
 116 }
 117 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
 118
 119 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u_int32_t pid, int flags)
 120 {
 121         return netlink_unicast(net->nfnl, skb, pid, flags);
 122 }
 123 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 124
 125 /* Process one complete nfnetlink message. */
 126 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 127 {
 128         struct net *net = sock_net(skb->sk);
 129         const struct nfnl_callback *nc;
 130         const struct nfnetlink_subsystem *ss;
 131         int type, err;
 132
 133         if (security_netlink_recv(skb, CAP_NET_ADMIN))
 134                 return -EPERM;
 135
 136         /* All the messages must at least contain nfgenmsg */
 137         if (nlh->nlmsg_len < NLMSG_LENGTH(sizeof(struct nfgenmsg)))
 138                 return 0;
 139
 140         type = nlh->nlmsg_type;
 141 replay:
 142         ss = nfnetlink_get_subsys(type);
 143         if (!ss) {
 144 #ifdef CONFIG_MODULES
 145                 nfnl_unlock();
 146                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 147                 nfnl_lock();
 148                 ss = nfnetlink_get_subsys(type);
 149                 if (!ss)
 150 #endif
 151                         return -EINVAL;
 152         }
 153
 154         nc = nfnetlink_find_client(type, ss);
 155         if (!nc)
 156                 return -EINVAL;
 157
 158         {
 159                 int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 160                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 161                 struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 162                 struct nlattr *attr = (void *)nlh + min_len;
 163                 int attrlen = nlh->nlmsg_len - min_len;
 164
 165                 err = nla_parse(cda, ss->cb[cb_id].attr_count,
 166                                 attr, attrlen, ss->cb[cb_id].policy);
 167                 if (err < 0)
 168                         return err;
 169
 170                 err = nc->call(net->nfnl, skb, nlh, (const struct nlattr **)cda);
 171                 if (err == -EAGAIN)
 172                         goto replay;
 173                 return err;
 174         }
 175 }
 176
 177 static void nfnetlink_rcv(struct sk_buff *skb)
 178 {
 179         nfnl_lock();
 180         netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 181         nfnl_unlock();
 182 }
 183
 184 static int __net_init nfnetlink_net_init(struct net *net)
 185 {
 186         struct sock *nfnl;
 187
 188         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, NFNLGRP_MAX,
 189                                      nfnetlink_rcv, NULL, THIS_MODULE);
 190         if (!nfnl)
 191                 return -ENOMEM;
 192         net->nfnl_stash = nfnl;
 193         rcu_assign_pointer(net->nfnl, nfnl);
 194         return 0;
 195 }
 196
 197 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 198 {
 199         struct net *net;
 200
 201         list_for_each_entry(net, net_exit_list, exit_list)
 202                 rcu_assign_pointer(net->nfnl, NULL);
 203         synchronize_net();
 204         list_for_each_entry(net, net_exit_list, exit_list)
 205                 netlink_kernel_release(net->nfnl_stash);
 206 }
 207
 208 static struct pernet_operations nfnetlink_net_ops = {
 209         .init           = nfnetlink_net_init,
 210         .exit_batch     = nfnetlink_net_exit_batch,
 211 };
 212
 213 static int __init nfnetlink_init(void)
 214 {
 215         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 216         return register_pernet_subsys(&nfnetlink_net_ops);
 217 }
 218
 219 static void __exit nfnetlink_exit(void)
 220 {
 221         pr_info("Removing netfilter NETLINK layer.\n");
 222         unregister_pernet_subsys(&nfnetlink_net_ops);
 223 }
 224 module_init(nfnetlink_init);
 225 module_exit(nfnetlink_exit);