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 static struct mutex *nfnl_get_lock(__u8 subsys_id)
  66 {
  67         return &table[subsys_id].mutex;
  68 }
  69
  70 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
  71 {
  72         nfnl_lock(n->subsys_id);
  73         if (table[n->subsys_id].subsys) {
  74                 nfnl_unlock(n->subsys_id);
  75                 return -EBUSY;
  76         }
  77         rcu_assign_pointer(table[n->subsys_id].subsys, n);
  78         nfnl_unlock(n->subsys_id);
  79
  80         return 0;
  81 }
  82 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  83
  84 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
  85 {
  86         nfnl_lock(n->subsys_id);
  87         table[n->subsys_id].subsys = NULL;
  88         nfnl_unlock(n->subsys_id);
  89         synchronize_rcu();
  90         return 0;
  91 }
  92 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
  93
  94 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  95 {
  96         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  97
  98         if (subsys_id >= NFNL_SUBSYS_COUNT)
  99                 return NULL;
 100
 101         return rcu_dereference(table[subsys_id].subsys);
 102 }
 103
 104 static inline const struct nfnl_callback *
 105 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
 106 {
 107         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 108
 109         if (cb_id >= ss->cb_count)
 110                 return NULL;
 111
 112         return &ss->cb[cb_id];
 113 }
 114
 115 int nfnetlink_has_listeners(struct net *net, unsigned int group)
 116 {
 117         return netlink_has_listeners(net->nfnl, group);
 118 }
 119 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 120
 121 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 pid,
 122                    unsigned int group, int echo, gfp_t flags)
 123 {
 124         return nlmsg_notify(net->nfnl, skb, pid, group, echo, flags);
 125 }
 126 EXPORT_SYMBOL_GPL(nfnetlink_send);
 127
 128 int nfnetlink_set_err(struct net *net, u32 pid, u32 group, int error)
 129 {
 130         return netlink_set_err(net->nfnl, pid, group, error);
 131 }
 132 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
 133
 134 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u_int32_t pid, int flags)
 135 {
 136         return netlink_unicast(net->nfnl, skb, pid, flags);
 137 }
 138 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 139
 140 /* Process one complete nfnetlink message. */
 141 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 142 {
 143         struct net *net = sock_net(skb->sk);
 144         const struct nfnl_callback *nc;
 145         const struct nfnetlink_subsystem *ss;
 146         int type, err;
 147
 148         if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
 149                 return -EPERM;
 150
 151         /* All the messages must at least contain nfgenmsg */
 152         if (nlh->nlmsg_len < NLMSG_LENGTH(sizeof(struct nfgenmsg)))
 153                 return 0;
 154
 155         type = nlh->nlmsg_type;
 156 replay:
 157         rcu_read_lock();
 158         ss = nfnetlink_get_subsys(type);
 159         if (!ss) {
 160 #ifdef CONFIG_MODULES
 161                 rcu_read_unlock();
 162                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 163                 rcu_read_lock();
 164                 ss = nfnetlink_get_subsys(type);
 165                 if (!ss)
 166 #endif
 167                 {
 168                         rcu_read_unlock();
 169                         return -EINVAL;
 170                 }
 171         }
 172
 173         nc = nfnetlink_find_client(type, ss);
 174         if (!nc) {
 175                 rcu_read_unlock();
 176                 return -EINVAL;
 177         }
 178
 179         {
 180                 int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 181                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 182                 struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 183                 struct nlattr *attr = (void *)nlh + min_len;
 184                 int attrlen = nlh->nlmsg_len - min_len;
 185                 __u8 subsys_id = NFNL_SUBSYS_ID(type);
 186
 187                 err = nla_parse(cda, ss->cb[cb_id].attr_count,
 188                                 attr, attrlen, ss->cb[cb_id].policy);
 189                 if (err < 0) {
 190                         rcu_read_unlock();
 191                         return err;
 192                 }
 193
 194                 if (nc->call_rcu) {
 195                         err = nc->call_rcu(net->nfnl, skb, nlh,
 196                                            (const struct nlattr **)cda);
 197                         rcu_read_unlock();
 198                 } else {
 199                         rcu_read_unlock();
 200                         nfnl_lock(subsys_id);
 201                         if (rcu_dereference_protected(table[subsys_id].subsys,
 202                                 lockdep_is_held(nfnl_get_lock(subsys_id))) != ss ||
 203                             nfnetlink_find_client(type, ss) != nc)
 204                                 err = -EAGAIN;
 205                         else if (nc->call)
 206                                 err = nc->call(net->nfnl, skb, nlh,
 207                                                    (const struct nlattr **)cda);
 208                         else
 209                                 err = -EINVAL;
 210                         nfnl_unlock(subsys_id);
 211                 }
 212                 if (err == -EAGAIN)
 213                         goto replay;
 214                 return err;
 215         }
 216 }
 217
 218 static void nfnetlink_rcv(struct sk_buff *skb)
 219 {
 220         netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 221 }
 222
 223 #ifdef CONFIG_MODULES
 224 static void nfnetlink_bind(int group)
 225 {
 226         const struct nfnetlink_subsystem *ss;
 227         int type = nfnl_group2type[group];
 228
 229         rcu_read_lock();
 230         ss = nfnetlink_get_subsys(type);
 231         if (!ss) {
 232                 rcu_read_unlock();
 233                 request_module("nfnetlink-subsys-%d", type);
 234                 return;
 235         }
 236         rcu_read_unlock();
 237 }
 238 #endif
 239
 240 static int __net_init nfnetlink_net_init(struct net *net)
 241 {
 242         struct sock *nfnl;
 243         struct netlink_kernel_cfg cfg = {
 244                 .groups = NFNLGRP_MAX,
 245                 .input  = nfnetlink_rcv,
 246 #ifdef CONFIG_MODULES
 247                 .bind   = nfnetlink_bind,
 248 #endif
 249         };
 250
 251         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
 252         if (!nfnl)
 253                 return -ENOMEM;
 254         net->nfnl_stash = nfnl;
 255         rcu_assign_pointer(net->nfnl, nfnl);
 256         return 0;
 257 }
 258
 259 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 260 {
 261         struct net *net;
 262
 263         list_for_each_entry(net, net_exit_list, exit_list)
 264                 RCU_INIT_POINTER(net->nfnl, NULL);
 265         synchronize_net();
 266         list_for_each_entry(net, net_exit_list, exit_list)
 267                 netlink_kernel_release(net->nfnl_stash);
 268 }
 269
 270 static struct pernet_operations nfnetlink_net_ops = {
 271         .init           = nfnetlink_net_init,
 272         .exit_batch     = nfnetlink_net_exit_batch,
 273 };
 274
 275 static int __init nfnetlink_init(void)
 276 {
 277         int i;
 278
 279         for (i=0; i<NFNL_SUBSYS_COUNT; i++)
 280                 mutex_init(&table[i].mutex);
 281
 282         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 283         return register_pernet_subsys(&nfnetlink_net_ops);
 284 }
 285
 286 static void __exit nfnetlink_exit(void)
 287 {
 288         pr_info("Removing netfilter NETLINK layer.\n");
 289         unregister_pernet_subsys(&nfnetlink_net_ops);
 290 }
 291 module_init(nfnetlink_init);
 292 module_exit(nfnetlink_exit);