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 struct {
  40         struct mutex                            mutex;
  41         const struct nfnetlink_subsystem __rcu  *subsys;
  42 } table[NFNL_SUBSYS_COUNT];
  43
  44 static const int nfnl_group2type[NFNLGRP_MAX+1] = {
  45         [NFNLGRP_CONNTRACK_NEW]         = NFNL_SUBSYS_CTNETLINK,
  46         [NFNLGRP_CONNTRACK_UPDATE]      = NFNL_SUBSYS_CTNETLINK,
  47         [NFNLGRP_CONNTRACK_DESTROY]     = NFNL_SUBSYS_CTNETLINK,
  48         [NFNLGRP_CONNTRACK_EXP_NEW]     = NFNL_SUBSYS_CTNETLINK_EXP,
  49         [NFNLGRP_CONNTRACK_EXP_UPDATE]  = NFNL_SUBSYS_CTNETLINK_EXP,
  50         [NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
  51 };
  52
  53 void nfnl_lock(__u8 subsys_id)
  54 {
  55         mutex_lock(&table[subsys_id].mutex);
  56 }
  57 EXPORT_SYMBOL_GPL(nfnl_lock);
  58
  59 void nfnl_unlock(__u8 subsys_id)
  60 {
  61         mutex_unlock(&table[subsys_id].mutex);
  62 }
  63 EXPORT_SYMBOL_GPL(nfnl_unlock);
  64
  65 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
  66 {
  67         nfnl_lock(n->subsys_id);
  68         if (table[n->subsys_id].subsys) {
  69                 nfnl_unlock(n->subsys_id);
  70                 return -EBUSY;
  71         }
  72         rcu_assign_pointer(table[n->subsys_id].subsys, n);
  73         nfnl_unlock(n->subsys_id);
  74
  75         return 0;
  76 }
  77 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  78
  79 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
  80 {
  81         nfnl_lock(n->subsys_id);
  82         table[n->subsys_id].subsys = NULL;
  83         nfnl_unlock(n->subsys_id);
  84         synchronize_rcu();
  85         return 0;
  86 }
  87 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
  88
  89 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  90 {
  91         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  92
  93         if (subsys_id >= NFNL_SUBSYS_COUNT)
  94                 return NULL;
  95
  96         return rcu_dereference(table[subsys_id].subsys);
  97 }
  98
  99 static inline const struct nfnl_callback *
 100 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
 101 {
 102         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 103
 104         if (cb_id >= ss->cb_count)
 105                 return NULL;
 106
 107         return &ss->cb[cb_id];
 108 }
 109
 110 int nfnetlink_has_listeners(struct net *net, unsigned int group)
 111 {
 112         return netlink_has_listeners(net->nfnl, group);
 113 }
 114 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 115
 116 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 pid,
 117                    unsigned int group, int echo, gfp_t flags)
 118 {
 119         return nlmsg_notify(net->nfnl, skb, pid, group, echo, flags);
 120 }
 121 EXPORT_SYMBOL_GPL(nfnetlink_send);
 122
 123 int nfnetlink_set_err(struct net *net, u32 pid, u32 group, int error)
 124 {
 125         return netlink_set_err(net->nfnl, pid, group, error);
 126 }
 127 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
 128
 129 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u_int32_t pid, int flags)
 130 {
 131         return netlink_unicast(net->nfnl, skb, pid, flags);
 132 }
 133 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 134
 135 /* Process one complete nfnetlink message. */
 136 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 137 {
 138         struct net *net = sock_net(skb->sk);
 139         const struct nfnl_callback *nc;
 140         const struct nfnetlink_subsystem *ss;
 141         int type, err;
 142
 143         if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
 144                 return -EPERM;
 145
 146         /* All the messages must at least contain nfgenmsg */
 147         if (nlh->nlmsg_len < NLMSG_LENGTH(sizeof(struct nfgenmsg)))
 148                 return 0;
 149
 150         type = nlh->nlmsg_type;
 151 replay:
 152         rcu_read_lock();
 153         ss = nfnetlink_get_subsys(type);
 154         if (!ss) {
 155 #ifdef CONFIG_MODULES
 156                 rcu_read_unlock();
 157                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 158                 rcu_read_lock();
 159                 ss = nfnetlink_get_subsys(type);
 160                 if (!ss)
 161 #endif
 162                 {
 163                         rcu_read_unlock();
 164                         return -EINVAL;
 165                 }
 166         }
 167
 168         nc = nfnetlink_find_client(type, ss);
 169         if (!nc) {
 170                 rcu_read_unlock();
 171                 return -EINVAL;
 172         }
 173
 174         {
 175                 int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 176                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 177                 struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 178                 struct nlattr *attr = (void *)nlh + min_len;
 179                 int attrlen = nlh->nlmsg_len - min_len;
 180                 __u8 subsys_id = NFNL_SUBSYS_ID(type);
 181
 182                 err = nla_parse(cda, ss->cb[cb_id].attr_count,
 183                                 attr, attrlen, ss->cb[cb_id].policy);
 184                 if (err < 0) {
 185                         rcu_read_unlock();
 186                         return err;
 187                 }
 188
 189                 if (nc->call_rcu) {
 190                         err = nc->call_rcu(net->nfnl, skb, nlh,
 191                                            (const struct nlattr **)cda);
 192                         rcu_read_unlock();
 193                 } else {
 194                         rcu_read_unlock();
 195                         nfnl_lock(subsys_id);
 196                         if (rcu_dereference_protected(table[subsys_id].subsys,
 197                                 lockdep_is_held(&table[subsys_id].mutex)) != ss ||
 198                             nfnetlink_find_client(type, ss) != nc)
 199                                 err = -EAGAIN;
 200                         else if (nc->call)
 201                                 err = nc->call(net->nfnl, skb, nlh,
 202                                                    (const struct nlattr **)cda);
 203                         else
 204                                 err = -EINVAL;
 205                         nfnl_unlock(subsys_id);
 206                 }
 207                 if (err == -EAGAIN)
 208                         goto replay;
 209                 return err;
 210         }
 211 }
 212
 213 static void nfnetlink_rcv(struct sk_buff *skb)
 214 {
 215         netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 216 }
 217
 218 #ifdef CONFIG_MODULES
 219 static void nfnetlink_bind(int group)
 220 {
 221         const struct nfnetlink_subsystem *ss;
 222         int type = nfnl_group2type[group];
 223
 224         rcu_read_lock();
 225         ss = nfnetlink_get_subsys(type);
 226         if (!ss) {
 227                 rcu_read_unlock();
 228                 request_module("nfnetlink-subsys-%d", type);
 229                 return;
 230         }
 231         rcu_read_unlock();
 232 }
 233 #endif
 234
 235 static int __net_init nfnetlink_net_init(struct net *net)
 236 {
 237         struct sock *nfnl;
 238         struct netlink_kernel_cfg cfg = {
 239                 .groups = NFNLGRP_MAX,
 240                 .input  = nfnetlink_rcv,
 241 #ifdef CONFIG_MODULES
 242                 .bind   = nfnetlink_bind,
 243 #endif
 244         };
 245
 246         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
 247         if (!nfnl)
 248                 return -ENOMEM;
 249         net->nfnl_stash = nfnl;
 250         rcu_assign_pointer(net->nfnl, nfnl);
 251         return 0;
 252 }
 253
 254 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 255 {
 256         struct net *net;
 257
 258         list_for_each_entry(net, net_exit_list, exit_list)
 259                 RCU_INIT_POINTER(net->nfnl, NULL);
 260         synchronize_net();
 261         list_for_each_entry(net, net_exit_list, exit_list)
 262                 netlink_kernel_release(net->nfnl_stash);
 263 }
 264
 265 static struct pernet_operations nfnetlink_net_ops = {
 266         .init           = nfnetlink_net_init,
 267         .exit_batch     = nfnetlink_net_exit_batch,
 268 };
 269
 270 static int __init nfnetlink_init(void)
 271 {
 272         int i;
 273
 274         for (i=0; i<NFNL_SUBSYS_COUNT; i++)
 275                 mutex_init(&table[i].mutex);
 276
 277         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 278         return register_pernet_subsys(&nfnetlink_net_ops);
 279 }
 280
 281 static void __exit nfnetlink_exit(void)
 282 {
 283         pr_info("Removing netfilter NETLINK layer.\n");
 284         unregister_pernet_subsys(&nfnetlink_net_ops);
 285 }
 286 module_init(nfnetlink_init);
 287 module_exit(nfnetlink_exit);