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/major.h>
  22 #include <linux/timer.h>
  23 #include <linux/string.h>
  24 #include <linux/sockios.h>
  25 #include <linux/net.h>
  26 #include <linux/fcntl.h>
  27 #include <linux/skbuff.h>
  28 #include <asm/uaccess.h>
  29 #include <asm/system.h>
  30 #include <net/sock.h>
  31 #include <net/netlink.h>
  32 #include <linux/init.h>
  33
  34 #include <linux/netlink.h>
  35 #include <linux/netfilter/nfnetlink.h>
  36
  37 MODULE_LICENSE("GPL");
  38 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  39 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
  40
  41 static char __initdata nfversion[] = "0.30";
  42
  43 static struct sock *nfnl = NULL;
  44 static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
  45 static DEFINE_MUTEX(nfnl_mutex);
  46
  47 static void nfnl_lock(void)
  48 {
  49         mutex_lock(&nfnl_mutex);
  50 }
  51
  52 static int nfnl_trylock(void)
  53 {
  54         return !mutex_trylock(&nfnl_mutex);
  55 }
  56
  57 static void __nfnl_unlock(void)
  58 {
  59         mutex_unlock(&nfnl_mutex);
  60 }
  61
  62 static void nfnl_unlock(void)
  63 {
  64         mutex_unlock(&nfnl_mutex);
  65         if (nfnl->sk_receive_queue.qlen)
  66                 nfnl->sk_data_ready(nfnl, 0);
  67 }
  68
  69 int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
  70 {
  71         nfnl_lock();
  72         if (subsys_table[n->subsys_id]) {
  73                 nfnl_unlock();
  74                 return -EBUSY;
  75         }
  76         subsys_table[n->subsys_id] = n;
  77         nfnl_unlock();
  78
  79         return 0;
  80 }
  81 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  82
  83 int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
  84 {
  85         nfnl_lock();
  86         subsys_table[n->subsys_id] = NULL;
  87         nfnl_unlock();
  88
  89         return 0;
  90 }
  91 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
  92
  93 static inline struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  94 {
  95         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  96
  97         if (subsys_id >= NFNL_SUBSYS_COUNT)
  98                 return NULL;
  99
 100         return subsys_table[subsys_id];
 101 }
 102
 103 static inline struct nfnl_callback *
 104 nfnetlink_find_client(u_int16_t type, struct nfnetlink_subsystem *ss)
 105 {
 106         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 107
 108         if (cb_id >= ss->cb_count)
 109                 return NULL;
 110
 111         return &ss->cb[cb_id];
 112 }
 113
 114 void __nfa_fill(struct sk_buff *skb, int attrtype, int attrlen,
 115                 const void *data)
 116 {
 117         struct nfattr *nfa;
 118         int size = NFA_LENGTH(attrlen);
 119
 120         nfa = (struct nfattr *)skb_put(skb, NFA_ALIGN(size));
 121         nfa->nfa_type = attrtype;
 122         nfa->nfa_len  = size;
 123         memcpy(NFA_DATA(nfa), data, attrlen);
 124         memset(NFA_DATA(nfa) + attrlen, 0, NFA_ALIGN(size) - size);
 125 }
 126 EXPORT_SYMBOL_GPL(__nfa_fill);
 127
 128 void nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
 129 {
 130         memset(tb, 0, sizeof(struct nfattr *) * maxattr);
 131
 132         while (NFA_OK(nfa, len)) {
 133                 unsigned flavor = NFA_TYPE(nfa);
 134                 if (flavor && flavor <= maxattr)
 135                         tb[flavor-1] = nfa;
 136                 nfa = NFA_NEXT(nfa, len);
 137         }
 138 }
 139 EXPORT_SYMBOL_GPL(nfattr_parse);
 140
 141 /**
 142  * nfnetlink_check_attributes - check and parse nfnetlink attributes
 143  *
 144  * subsys: nfnl subsystem for which this message is to be parsed
 145  * nlmsghdr: netlink message to be checked/parsed
 146  * cda: array of pointers, needs to be at least subsys->attr_count big
 147  *
 148  */
 149 static int
 150 nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
 151                            struct nlmsghdr *nlh, struct nfattr *cda[])
 152 {
 153         int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 154         u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 155         u_int16_t attr_count = subsys->cb[cb_id].attr_count;
 156
 157         /* check attribute lengths. */
 158         if (likely(nlh->nlmsg_len > min_len)) {
 159                 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
 160                 int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 161                 nfattr_parse(cda, attr_count, attr, attrlen);
 162         }
 163
 164         /* implicit: if nlmsg_len == min_len, we return 0, and an empty
 165          * (zeroed) cda[] array. The message is valid, but empty. */
 166
 167         return 0;
 168 }
 169
 170 int nfnetlink_has_listeners(unsigned int group)
 171 {
 172         return netlink_has_listeners(nfnl, group);
 173 }
 174 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 175
 176 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 177 {
 178         int err = 0;
 179
 180         NETLINK_CB(skb).dst_group = group;
 181         if (echo)
 182                 atomic_inc(&skb->users);
 183         netlink_broadcast(nfnl, skb, pid, group, gfp_any());
 184         if (echo)
 185                 err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
 186
 187         return err;
 188 }
 189 EXPORT_SYMBOL_GPL(nfnetlink_send);
 190
 191 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
 192 {
 193         return netlink_unicast(nfnl, skb, pid, flags);
 194 }
 195 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 196
 197 /* Process one complete nfnetlink message. */
 198 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 199 {
 200         struct nfnl_callback *nc;
 201         struct nfnetlink_subsystem *ss;
 202         int type, err;
 203
 204         if (security_netlink_recv(skb, CAP_NET_ADMIN))
 205                 return -EPERM;
 206
 207         /* Only requests are handled by kernel now. */
 208         if (!(nlh->nlmsg_flags & NLM_F_REQUEST))
 209                 return 0;
 210
 211         /* All the messages must at least contain nfgenmsg */
 212         if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg)))
 213                 return 0;
 214
 215         type = nlh->nlmsg_type;
 216         ss = nfnetlink_get_subsys(type);
 217         if (!ss) {
 218 #ifdef CONFIG_KMOD
 219                 /* don't call nfnl_unlock, since it would reenter
 220                  * with further packet processing */
 221                 __nfnl_unlock();
 222                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 223                 nfnl_lock();
 224                 ss = nfnetlink_get_subsys(type);
 225                 if (!ss)
 226 #endif
 227                         return -EINVAL;
 228         }
 229
 230         nc = nfnetlink_find_client(type, ss);
 231         if (!nc)
 232                 return -EINVAL;
 233
 234         {
 235                 u_int16_t attr_count =
 236                         ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count;
 237                 struct nfattr *cda[attr_count];
 238
 239                 memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 240
 241                 err = nfnetlink_check_attributes(ss, nlh, cda);
 242                 if (err < 0)
 243                         return err;
 244                 return nc->call(nfnl, skb, nlh, cda);
 245         }
 246 }
 247
 248 static void nfnetlink_rcv(struct sock *sk, int len)
 249 {
 250         unsigned int qlen = 0;
 251
 252         do {
 253                 if (nfnl_trylock())
 254                         return;
 255                 netlink_run_queue(sk, &qlen, nfnetlink_rcv_msg);
 256                 __nfnl_unlock();
 257         } while (qlen);
 258 }
 259
 260 static void __exit nfnetlink_exit(void)
 261 {
 262         printk("Removing netfilter NETLINK layer.\n");
 263         sock_release(nfnl->sk_socket);
 264         return;
 265 }
 266
 267 static int __init nfnetlink_init(void)
 268 {
 269         printk("Netfilter messages via NETLINK v%s.\n", nfversion);
 270
 271         nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX,
 272                                      nfnetlink_rcv, THIS_MODULE);
 273         if (!nfnl) {
 274                 printk(KERN_ERR "cannot initialize nfnetlink!\n");
 275                 return -1;
 276         }
 277
 278         return 0;
 279 }
 280
 281 module_init(nfnetlink_init);
 282 module_exit(nfnetlink_exit);