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 __rcu *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         rcu_assign_pointer(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         synchronize_rcu();
  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 rcu_dereference(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         rcu_read_lock();
 143         ss = nfnetlink_get_subsys(type);
 144         if (!ss) {
 145 #ifdef CONFIG_MODULES
 146                 rcu_read_unlock();
 147                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 148                 rcu_read_lock();
 149                 ss = nfnetlink_get_subsys(type);
 150                 if (!ss)
 151 #endif
 152                 {
 153                         rcu_read_unlock();
 154                         return -EINVAL;
 155                 }
 156         }
 157
 158         nc = nfnetlink_find_client(type, ss);
 159         if (!nc) {
 160                 rcu_read_unlock();
 161                 return -EINVAL;
 162         }
 163
 164         {
 165                 int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 166                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 167                 struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 168                 struct nlattr *attr = (void *)nlh + min_len;
 169                 int attrlen = nlh->nlmsg_len - min_len;
 170
 171                 err = nla_parse(cda, ss->cb[cb_id].attr_count,
 172                                 attr, attrlen, ss->cb[cb_id].policy);
 173                 if (err < 0)
 174                         return err;
 175
 176                 if (nc->call_rcu) {
 177                         err = nc->call_rcu(net->nfnl, skb, nlh,
 178                                            (const struct nlattr **)cda);
 179                         rcu_read_unlock();
 180                 } else {
 181                         rcu_read_unlock();
 182                         nfnl_lock();
 183                         if (rcu_dereference_protected(
 184                                         subsys_table[NFNL_SUBSYS_ID(type)],
 185                                         lockdep_is_held(&nfnl_mutex)) != ss ||
 186                             nfnetlink_find_client(type, ss) != nc)
 187                                 err = -EAGAIN;
 188                         else
 189                                 err = nc->call(net->nfnl, skb, nlh,
 190                                                    (const struct nlattr **)cda);
 191                         nfnl_unlock();
 192                 }
 193                 if (err == -EAGAIN)
 194                         goto replay;
 195                 return err;
 196         }
 197 }
 198
 199 static void nfnetlink_rcv(struct sk_buff *skb)
 200 {
 201         netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 202 }
 203
 204 static int __net_init nfnetlink_net_init(struct net *net)
 205 {
 206         struct sock *nfnl;
 207
 208         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, NFNLGRP_MAX,
 209                                      nfnetlink_rcv, NULL, THIS_MODULE);
 210         if (!nfnl)
 211                 return -ENOMEM;
 212         net->nfnl_stash = nfnl;
 213         rcu_assign_pointer(net->nfnl, nfnl);
 214         return 0;
 215 }
 216
 217 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 218 {
 219         struct net *net;
 220
 221         list_for_each_entry(net, net_exit_list, exit_list)
 222                 rcu_assign_pointer(net->nfnl, NULL);
 223         synchronize_net();
 224         list_for_each_entry(net, net_exit_list, exit_list)
 225                 netlink_kernel_release(net->nfnl_stash);
 226 }
 227
 228 static struct pernet_operations nfnetlink_net_ops = {
 229         .init           = nfnetlink_net_init,
 230         .exit_batch     = nfnetlink_net_exit_batch,
 231 };
 232
 233 static int __init nfnetlink_init(void)
 234 {
 235         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 236         return register_pernet_subsys(&nfnetlink_net_ops);
 237 }
 238
 239 static void __exit nfnetlink_exit(void)
 240 {
 241         pr_info("Removing netfilter NETLINK layer.\n");
 242         unregister_pernet_subsys(&nfnetlink_net_ops);
 243 }
 244 module_init(nfnetlink_init);
 245 module_exit(nfnetlink_exit);