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 static const int nfnl_group2type[NFNLGRP_MAX+1] = {
  43         [NFNLGRP_CONNTRACK_NEW]         = NFNL_SUBSYS_CTNETLINK,
  44         [NFNLGRP_CONNTRACK_UPDATE]      = NFNL_SUBSYS_CTNETLINK,
  45         [NFNLGRP_CONNTRACK_DESTROY]     = NFNL_SUBSYS_CTNETLINK,
  46         [NFNLGRP_CONNTRACK_EXP_NEW]     = NFNL_SUBSYS_CTNETLINK_EXP,
  47         [NFNLGRP_CONNTRACK_EXP_UPDATE]  = NFNL_SUBSYS_CTNETLINK_EXP,
  48         [NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
  49 };
  50
  51 void nfnl_lock(void)
  52 {
  53         mutex_lock(&nfnl_mutex);
  54 }
  55 EXPORT_SYMBOL_GPL(nfnl_lock);
  56
  57 void nfnl_unlock(void)
  58 {
  59         mutex_unlock(&nfnl_mutex);
  60 }
  61 EXPORT_SYMBOL_GPL(nfnl_unlock);
  62
  63 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
  64 {
  65         nfnl_lock();
  66         if (subsys_table[n->subsys_id]) {
  67                 nfnl_unlock();
  68                 return -EBUSY;
  69         }
  70         rcu_assign_pointer(subsys_table[n->subsys_id], n);
  71         nfnl_unlock();
  72
  73         return 0;
  74 }
  75 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  76
  77 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
  78 {
  79         nfnl_lock();
  80         subsys_table[n->subsys_id] = NULL;
  81         nfnl_unlock();
  82         synchronize_rcu();
  83         return 0;
  84 }
  85 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
  86
  87 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  88 {
  89         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  90
  91         if (subsys_id >= NFNL_SUBSYS_COUNT)
  92                 return NULL;
  93
  94         return rcu_dereference(subsys_table[subsys_id]);
  95 }
  96
  97 static inline const struct nfnl_callback *
  98 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
  99 {
 100         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 101
 102         if (cb_id >= ss->cb_count)
 103                 return NULL;
 104
 105         return &ss->cb[cb_id];
 106 }
 107
 108 int nfnetlink_has_listeners(struct net *net, unsigned int group)
 109 {
 110         return netlink_has_listeners(net->nfnl, group);
 111 }
 112 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 113
 114 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 pid,
 115                    unsigned int group, int echo, gfp_t flags)
 116 {
 117         return nlmsg_notify(net->nfnl, skb, pid, group, echo, flags);
 118 }
 119 EXPORT_SYMBOL_GPL(nfnetlink_send);
 120
 121 int nfnetlink_set_err(struct net *net, u32 pid, u32 group, int error)
 122 {
 123         return netlink_set_err(net->nfnl, pid, group, error);
 124 }
 125 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
 126
 127 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u_int32_t pid, int flags)
 128 {
 129         return netlink_unicast(net->nfnl, skb, pid, flags);
 130 }
 131 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 132
 133 /* Process one complete nfnetlink message. */
 134 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 135 {
 136         struct net *net = sock_net(skb->sk);
 137         const struct nfnl_callback *nc;
 138         const struct nfnetlink_subsystem *ss;
 139         int type, err;
 140
 141         if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
 142                 return -EPERM;
 143
 144         /* All the messages must at least contain nfgenmsg */
 145         if (nlh->nlmsg_len < NLMSG_LENGTH(sizeof(struct nfgenmsg)))
 146                 return 0;
 147
 148         type = nlh->nlmsg_type;
 149 replay:
 150         rcu_read_lock();
 151         ss = nfnetlink_get_subsys(type);
 152         if (!ss) {
 153 #ifdef CONFIG_MODULES
 154                 rcu_read_unlock();
 155                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 156                 rcu_read_lock();
 157                 ss = nfnetlink_get_subsys(type);
 158                 if (!ss)
 159 #endif
 160                 {
 161                         rcu_read_unlock();
 162                         return -EINVAL;
 163                 }
 164         }
 165
 166         nc = nfnetlink_find_client(type, ss);
 167         if (!nc) {
 168                 rcu_read_unlock();
 169                 return -EINVAL;
 170         }
 171
 172         {
 173                 int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 174                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 175                 struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 176                 struct nlattr *attr = (void *)nlh + min_len;
 177                 int attrlen = nlh->nlmsg_len - min_len;
 178
 179                 err = nla_parse(cda, ss->cb[cb_id].attr_count,
 180                                 attr, attrlen, ss->cb[cb_id].policy);
 181                 if (err < 0) {
 182                         rcu_read_unlock();
 183                         return err;
 184                 }
 185
 186                 if (nc->call_rcu) {
 187                         err = nc->call_rcu(net->nfnl, skb, nlh,
 188                                            (const struct nlattr **)cda);
 189                         rcu_read_unlock();
 190                 } else {
 191                         rcu_read_unlock();
 192                         nfnl_lock();
 193                         if (rcu_dereference_protected(
 194                                         subsys_table[NFNL_SUBSYS_ID(type)],
 195                                         lockdep_is_held(&nfnl_mutex)) != ss ||
 196                             nfnetlink_find_client(type, ss) != nc)
 197                                 err = -EAGAIN;
 198                         else if (nc->call)
 199                                 err = nc->call(net->nfnl, skb, nlh,
 200                                                    (const struct nlattr **)cda);
 201                         else
 202                                 err = -EINVAL;
 203                         nfnl_unlock();
 204                 }
 205                 if (err == -EAGAIN)
 206                         goto replay;
 207                 return err;
 208         }
 209 }
 210
 211 static void nfnetlink_rcv(struct sk_buff *skb)
 212 {
 213         netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 214 }
 215
 216 #ifdef CONFIG_MODULES
 217 static void nfnetlink_bind(int group)
 218 {
 219         const struct nfnetlink_subsystem *ss;
 220         int type = nfnl_group2type[group];
 221
 222         rcu_read_lock();
 223         ss = nfnetlink_get_subsys(type);
 224         if (!ss) {
 225                 rcu_read_unlock();
 226                 request_module("nfnetlink-subsys-%d", type);
 227                 return;
 228         }
 229         rcu_read_unlock();
 230 }
 231 #endif
 232
 233 static int __net_init nfnetlink_net_init(struct net *net)
 234 {
 235         struct sock *nfnl;
 236         struct netlink_kernel_cfg cfg = {
 237                 .groups = NFNLGRP_MAX,
 238                 .input  = nfnetlink_rcv,
 239 #ifdef CONFIG_MODULES
 240                 .bind   = nfnetlink_bind,
 241 #endif
 242         };
 243
 244         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
 245         if (!nfnl)
 246                 return -ENOMEM;
 247         net->nfnl_stash = nfnl;
 248         rcu_assign_pointer(net->nfnl, nfnl);
 249         return 0;
 250 }
 251
 252 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 253 {
 254         struct net *net;
 255
 256         list_for_each_entry(net, net_exit_list, exit_list)
 257                 RCU_INIT_POINTER(net->nfnl, NULL);
 258         synchronize_net();
 259         list_for_each_entry(net, net_exit_list, exit_list)
 260                 netlink_kernel_release(net->nfnl_stash);
 261 }
 262
 263 static struct pernet_operations nfnetlink_net_ops = {
 264         .init           = nfnetlink_net_init,
 265         .exit_batch     = nfnetlink_net_exit_batch,
 266 };
 267
 268 static int __init nfnetlink_init(void)
 269 {
 270         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 271         return register_pernet_subsys(&nfnetlink_net_ops);
 272 }
 273
 274 static void __exit nfnetlink_exit(void)
 275 {
 276         pr_info("Removing netfilter NETLINK layer.\n");
 277         unregister_pernet_subsys(&nfnetlink_net_ops);
 278 }
 279 module_init(nfnetlink_init);
 280 module_exit(nfnetlink_exit);