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 <linux/init.h>
  28
  29 #include <net/netlink.h>
  30 #include <linux/netfilter/nfnetlink.h>
  31
  32 MODULE_LICENSE("GPL");
  33 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  34 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
  35
  36 static char __initdata nfversion[] = "0.30";
  37
  38 static struct {
  39         struct mutex                            mutex;
  40         const struct nfnetlink_subsystem __rcu  *subsys;
  41 } table[NFNL_SUBSYS_COUNT];
  42
  43 static const int nfnl_group2type[NFNLGRP_MAX+1] = {
  44         [NFNLGRP_CONNTRACK_NEW]         = NFNL_SUBSYS_CTNETLINK,
  45         [NFNLGRP_CONNTRACK_UPDATE]      = NFNL_SUBSYS_CTNETLINK,
  46         [NFNLGRP_CONNTRACK_DESTROY]     = NFNL_SUBSYS_CTNETLINK,
  47         [NFNLGRP_CONNTRACK_EXP_NEW]     = NFNL_SUBSYS_CTNETLINK_EXP,
  48         [NFNLGRP_CONNTRACK_EXP_UPDATE]  = NFNL_SUBSYS_CTNETLINK_EXP,
  49         [NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
  50 };
  51
  52 void nfnl_lock(__u8 subsys_id)
  53 {
  54         mutex_lock(&table[subsys_id].mutex);
  55 }
  56 EXPORT_SYMBOL_GPL(nfnl_lock);
  57
  58 void nfnl_unlock(__u8 subsys_id)
  59 {
  60         mutex_unlock(&table[subsys_id].mutex);
  61 }
  62 EXPORT_SYMBOL_GPL(nfnl_unlock);
  63
  64 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
  65 {
  66         nfnl_lock(n->subsys_id);
  67         if (table[n->subsys_id].subsys) {
  68                 nfnl_unlock(n->subsys_id);
  69                 return -EBUSY;
  70         }
  71         rcu_assign_pointer(table[n->subsys_id].subsys, n);
  72         nfnl_unlock(n->subsys_id);
  73
  74         return 0;
  75 }
  76 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  77
  78 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
  79 {
  80         nfnl_lock(n->subsys_id);
  81         table[n->subsys_id].subsys = NULL;
  82         nfnl_unlock(n->subsys_id);
  83         synchronize_rcu();
  84         return 0;
  85 }
  86 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
  87
  88 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  89 {
  90         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  91
  92         if (subsys_id >= NFNL_SUBSYS_COUNT)
  93                 return NULL;
  94
  95         return rcu_dereference(table[subsys_id].subsys);
  96 }
  97
  98 static inline const struct nfnl_callback *
  99 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
 100 {
 101         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 102
 103         if (cb_id >= ss->cb_count)
 104                 return NULL;
 105
 106         return &ss->cb[cb_id];
 107 }
 108
 109 int nfnetlink_has_listeners(struct net *net, unsigned int group)
 110 {
 111         return netlink_has_listeners(net->nfnl, group);
 112 }
 113 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 114
 115 struct sk_buff *nfnetlink_alloc_skb(struct net *net, unsigned int size,
 116                                     u32 dst_portid, gfp_t gfp_mask)
 117 {
 118         return netlink_alloc_skb(net->nfnl, size, dst_portid, gfp_mask);
 119 }
 120 EXPORT_SYMBOL_GPL(nfnetlink_alloc_skb);
 121
 122 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
 123                    unsigned int group, int echo, gfp_t flags)
 124 {
 125         return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
 126 }
 127 EXPORT_SYMBOL_GPL(nfnetlink_send);
 128
 129 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
 130 {
 131         return netlink_set_err(net->nfnl, portid, group, error);
 132 }
 133 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
 134
 135 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
 136                       int flags)
 137 {
 138         return netlink_unicast(net->nfnl, skb, portid, flags);
 139 }
 140 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 141
 142 /* Process one complete nfnetlink message. */
 143 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 144 {
 145         struct net *net = sock_net(skb->sk);
 146         const struct nfnl_callback *nc;
 147         const struct nfnetlink_subsystem *ss;
 148         int type, err;
 149
 150         if (!netlink_net_capable(skb, CAP_NET_ADMIN))
 151                 return -EPERM;
 152
 153         /* All the messages must at least contain nfgenmsg */
 154         if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
 155                 return 0;
 156
 157         type = nlh->nlmsg_type;
 158 replay:
 159         rcu_read_lock();
 160         ss = nfnetlink_get_subsys(type);
 161         if (!ss) {
 162 #ifdef CONFIG_MODULES
 163                 rcu_read_unlock();
 164                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 165                 rcu_read_lock();
 166                 ss = nfnetlink_get_subsys(type);
 167                 if (!ss)
 168 #endif
 169                 {
 170                         rcu_read_unlock();
 171                         return -EINVAL;
 172                 }
 173         }
 174
 175         nc = nfnetlink_find_client(type, ss);
 176         if (!nc) {
 177                 rcu_read_unlock();
 178                 return -EINVAL;
 179         }
 180
 181         {
 182                 int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 183                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 184                 struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 185                 struct nlattr *attr = (void *)nlh + min_len;
 186                 int attrlen = nlh->nlmsg_len - min_len;
 187                 __u8 subsys_id = NFNL_SUBSYS_ID(type);
 188
 189                 err = nla_parse(cda, ss->cb[cb_id].attr_count,
 190                                 attr, attrlen, ss->cb[cb_id].policy);
 191                 if (err < 0) {
 192                         rcu_read_unlock();
 193                         return err;
 194                 }
 195
 196                 if (nc->call_rcu) {
 197                         err = nc->call_rcu(net->nfnl, skb, nlh,
 198                                            (const struct nlattr **)cda);
 199                         rcu_read_unlock();
 200                 } else {
 201                         rcu_read_unlock();
 202                         nfnl_lock(subsys_id);
 203                         if (rcu_dereference_protected(table[subsys_id].subsys,
 204                                 lockdep_is_held(&table[subsys_id].mutex)) != ss ||
 205                             nfnetlink_find_client(type, ss) != nc)
 206                                 err = -EAGAIN;
 207                         else if (nc->call)
 208                                 err = nc->call(net->nfnl, skb, nlh,
 209                                                    (const struct nlattr **)cda);
 210                         else
 211                                 err = -EINVAL;
 212                         nfnl_unlock(subsys_id);
 213                 }
 214                 if (err == -EAGAIN)
 215                         goto replay;
 216                 return err;
 217         }
 218 }
 219
 220 static void nfnetlink_rcv(struct sk_buff *skb)
 221 {
 222         netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 223 }
 224
 225 #ifdef CONFIG_MODULES
 226 static void nfnetlink_bind(int group)
 227 {
 228         const struct nfnetlink_subsystem *ss;
 229         int type = nfnl_group2type[group];
 230
 231         rcu_read_lock();
 232         ss = nfnetlink_get_subsys(type);
 233         if (!ss) {
 234                 rcu_read_unlock();
 235                 request_module("nfnetlink-subsys-%d", type);
 236                 return;
 237         }
 238         rcu_read_unlock();
 239 }
 240 #endif
 241
 242 static int __net_init nfnetlink_net_init(struct net *net)
 243 {
 244         struct sock *nfnl;
 245         struct netlink_kernel_cfg cfg = {
 246                 .groups = NFNLGRP_MAX,
 247                 .input  = nfnetlink_rcv,
 248 #ifdef CONFIG_MODULES
 249                 .bind   = nfnetlink_bind,
 250 #endif
 251         };
 252
 253         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
 254         if (!nfnl)
 255                 return -ENOMEM;
 256         net->nfnl_stash = nfnl;
 257         rcu_assign_pointer(net->nfnl, nfnl);
 258         return 0;
 259 }
 260
 261 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 262 {
 263         struct net *net;
 264
 265         list_for_each_entry(net, net_exit_list, exit_list)
 266                 RCU_INIT_POINTER(net->nfnl, NULL);
 267         synchronize_net();
 268         list_for_each_entry(net, net_exit_list, exit_list)
 269                 netlink_kernel_release(net->nfnl_stash);
 270 }
 271
 272 static struct pernet_operations nfnetlink_net_ops = {
 273         .init           = nfnetlink_net_init,
 274         .exit_batch     = nfnetlink_net_exit_batch,
 275 };
 276
 277 static int __init nfnetlink_init(void)
 278 {
 279         int i;
 280
 281         for (i=0; i<NFNL_SUBSYS_COUNT; i++)
 282                 mutex_init(&table[i].mutex);
 283
 284         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 285         return register_pernet_subsys(&nfnetlink_net_ops);
 286 }
 287
 288 static void __exit nfnetlink_exit(void)
 289 {
 290         pr_info("Removing netfilter NETLINK layer.\n");
 291         unregister_pernet_subsys(&nfnetlink_net_ops);
 292 }
 293 module_init(nfnetlink_init);
 294 module_exit(nfnetlink_exit);