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 <net/sock.h>
  27 #include <net/netlink.h>
  28 #include <linux/init.h>
  29
  30 #include <linux/netlink.h>
  31 #include <linux/netfilter/nfnetlink.h>
  32
  33 MODULE_LICENSE("GPL");
  34 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  35 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
  36
  37 static char __initdata nfversion[] = "0.30";
  38
  39 static const struct nfnetlink_subsystem __rcu *subsys_table[NFNL_SUBSYS_COUNT];
  40 static DEFINE_MUTEX(nfnl_mutex);
  41
  42 void nfnl_lock(void)
  43 {
  44         mutex_lock(&nfnl_mutex);
  45 }
  46 EXPORT_SYMBOL_GPL(nfnl_lock);
  47
  48 void nfnl_unlock(void)
  49 {
  50         mutex_unlock(&nfnl_mutex);
  51 }
  52 EXPORT_SYMBOL_GPL(nfnl_unlock);
  53
  54 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
  55 {
  56         nfnl_lock();
  57         if (subsys_table[n->subsys_id]) {
  58                 nfnl_unlock();
  59                 return -EBUSY;
  60         }
  61         rcu_assign_pointer(subsys_table[n->subsys_id], n);
  62         nfnl_unlock();
  63
  64         return 0;
  65 }
  66 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  67
  68 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
  69 {
  70         nfnl_lock();
  71         subsys_table[n->subsys_id] = NULL;
  72         nfnl_unlock();
  73         synchronize_rcu();
  74         return 0;
  75 }
  76 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
  77
  78 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  79 {
  80         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  81
  82         if (subsys_id >= NFNL_SUBSYS_COUNT)
  83                 return NULL;
  84
  85         return rcu_dereference(subsys_table[subsys_id]);
  86 }
  87
  88 static inline const struct nfnl_callback *
  89 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
  90 {
  91         u_int8_t cb_id = NFNL_MSG_TYPE(type);
  92
  93         if (cb_id >= ss->cb_count)
  94                 return NULL;
  95
  96         return &ss->cb[cb_id];
  97 }
  98
  99 int nfnetlink_has_listeners(struct net *net, unsigned int group)
 100 {
 101         return netlink_has_listeners(net->nfnl, group);
 102 }
 103 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 104
 105 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 pid,
 106                    unsigned int group, int echo, gfp_t flags)
 107 {
 108         return nlmsg_notify(net->nfnl, skb, pid, group, echo, flags);
 109 }
 110 EXPORT_SYMBOL_GPL(nfnetlink_send);
 111
 112 int nfnetlink_set_err(struct net *net, u32 pid, u32 group, int error)
 113 {
 114         return netlink_set_err(net->nfnl, pid, group, error);
 115 }
 116 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
 117
 118 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u_int32_t pid, int flags)
 119 {
 120         return netlink_unicast(net->nfnl, skb, pid, flags);
 121 }
 122 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 123
 124 /* Process one complete nfnetlink message. */
 125 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 126 {
 127         struct net *net = sock_net(skb->sk);
 128         const struct nfnl_callback *nc;
 129         const struct nfnetlink_subsystem *ss;
 130         int type, err;
 131
 132         if (!capable(CAP_NET_ADMIN))
 133                 return -EPERM;
 134
 135         /* All the messages must at least contain nfgenmsg */
 136         if (nlh->nlmsg_len < NLMSG_LENGTH(sizeof(struct nfgenmsg)))
 137                 return 0;
 138
 139         type = nlh->nlmsg_type;
 140 replay:
 141         rcu_read_lock();
 142         ss = nfnetlink_get_subsys(type);
 143         if (!ss) {
 144 #ifdef CONFIG_MODULES
 145                 rcu_read_unlock();
 146                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 147                 rcu_read_lock();
 148                 ss = nfnetlink_get_subsys(type);
 149                 if (!ss)
 150 #endif
 151                 {
 152                         rcu_read_unlock();
 153                         return -EINVAL;
 154                 }
 155         }
 156
 157         nc = nfnetlink_find_client(type, ss);
 158         if (!nc) {
 159                 rcu_read_unlock();
 160                 return -EINVAL;
 161         }
 162
 163         {
 164                 int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 165                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 166                 struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 167                 struct nlattr *attr = (void *)nlh + min_len;
 168                 int attrlen = nlh->nlmsg_len - min_len;
 169
 170                 err = nla_parse(cda, ss->cb[cb_id].attr_count,
 171                                 attr, attrlen, ss->cb[cb_id].policy);
 172                 if (err < 0)
 173                         return err;
 174
 175                 if (nc->call_rcu) {
 176                         err = nc->call_rcu(net->nfnl, skb, nlh,
 177                                            (const struct nlattr **)cda);
 178                         rcu_read_unlock();
 179                 } else {
 180                         rcu_read_unlock();
 181                         nfnl_lock();
 182                         if (rcu_dereference_protected(
 183                                         subsys_table[NFNL_SUBSYS_ID(type)],
 184                                         lockdep_is_held(&nfnl_mutex)) != ss ||
 185                             nfnetlink_find_client(type, ss) != nc)
 186                                 err = -EAGAIN;
 187                         else
 188                                 err = nc->call(net->nfnl, skb, nlh,
 189                                                    (const struct nlattr **)cda);
 190                         nfnl_unlock();
 191                 }
 192                 if (err == -EAGAIN)
 193                         goto replay;
 194                 return err;
 195         }
 196 }
 197
 198 static void nfnetlink_rcv(struct sk_buff *skb)
 199 {
 200         netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 201 }
 202
 203 static int __net_init nfnetlink_net_init(struct net *net)
 204 {
 205         struct sock *nfnl;
 206
 207         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, NFNLGRP_MAX,
 208                                      nfnetlink_rcv, NULL, THIS_MODULE);
 209         if (!nfnl)
 210                 return -ENOMEM;
 211         net->nfnl_stash = nfnl;
 212         rcu_assign_pointer(net->nfnl, nfnl);
 213         return 0;
 214 }
 215
 216 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 217 {
 218         struct net *net;
 219
 220         list_for_each_entry(net, net_exit_list, exit_list)
 221                 RCU_INIT_POINTER(net->nfnl, NULL);
 222         synchronize_net();
 223         list_for_each_entry(net, net_exit_list, exit_list)
 224                 netlink_kernel_release(net->nfnl_stash);
 225 }
 226
 227 static struct pernet_operations nfnetlink_net_ops = {
 228         .init           = nfnetlink_net_init,
 229         .exit_batch     = nfnetlink_net_exit_batch,
 230 };
 231
 232 static int __init nfnetlink_init(void)
 233 {
 234         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 235         return register_pernet_subsys(&nfnetlink_net_ops);
 236 }
 237
 238 static void __exit nfnetlink_exit(void)
 239 {
 240         pr_info("Removing netfilter NETLINK layer.\n");
 241         unregister_pernet_subsys(&nfnetlink_net_ops);
 242 }
 243 module_init(nfnetlink_init);
 244 module_exit(nfnetlink_exit);