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
  82 int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
  83 {
  84         nfnl_lock();
  85         subsys_table[n->subsys_id] = NULL;
  86         nfnl_unlock();
  87
  88         return 0;
  89 }
  90
  91 static inline struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  92 {
  93         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  94
  95         if (subsys_id >= NFNL_SUBSYS_COUNT)
  96                 return NULL;
  97
  98         return subsys_table[subsys_id];
  99 }
 100
 101 static inline struct nfnl_callback *
 102 nfnetlink_find_client(u_int16_t type, struct nfnetlink_subsystem *ss)
 103 {
 104         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 105
 106         if (cb_id >= ss->cb_count)
 107                 return NULL;
 108
 109         return &ss->cb[cb_id];
 110 }
 111
 112 void __nfa_fill(struct sk_buff *skb, int attrtype, int attrlen,
 113                 const void *data)
 114 {
 115         struct nfattr *nfa;
 116         int size = NFA_LENGTH(attrlen);
 117
 118         nfa = (struct nfattr *)skb_put(skb, NFA_ALIGN(size));
 119         nfa->nfa_type = attrtype;
 120         nfa->nfa_len  = size;
 121         memcpy(NFA_DATA(nfa), data, attrlen);
 122         memset(NFA_DATA(nfa) + attrlen, 0, NFA_ALIGN(size) - size);
 123 }
 124
 125 void nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
 126 {
 127         memset(tb, 0, sizeof(struct nfattr *) * maxattr);
 128
 129         while (NFA_OK(nfa, len)) {
 130                 unsigned flavor = NFA_TYPE(nfa);
 131                 if (flavor && flavor <= maxattr)
 132                         tb[flavor-1] = nfa;
 133                 nfa = NFA_NEXT(nfa, len);
 134         }
 135 }
 136
 137 /**
 138  * nfnetlink_check_attributes - check and parse nfnetlink attributes
 139  *
 140  * subsys: nfnl subsystem for which this message is to be parsed
 141  * nlmsghdr: netlink message to be checked/parsed
 142  * cda: array of pointers, needs to be at least subsys->attr_count big
 143  *
 144  */
 145 static int
 146 nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
 147                            struct nlmsghdr *nlh, struct nfattr *cda[])
 148 {
 149         int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 150         u_int16_t attr_count;
 151         u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 152
 153         attr_count = subsys->cb[cb_id].attr_count;
 154         memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 155
 156         /* check attribute lengths. */
 157         if (likely(nlh->nlmsg_len > min_len)) {
 158                 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
 159                 int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 160
 161                 while (NFA_OK(attr, attrlen)) {
 162                         unsigned flavor = NFA_TYPE(attr);
 163                         if (flavor) {
 164                                 if (flavor > attr_count)
 165                                         return -EINVAL;
 166                                 cda[flavor - 1] = attr;
 167                         }
 168                         attr = NFA_NEXT(attr, attrlen);
 169                 }
 170         }
 171
 172         /* implicit: if nlmsg_len == min_len, we return 0, and an empty
 173          * (zeroed) cda[] array. The message is valid, but empty. */
 174
 175         return 0;
 176 }
 177
 178 int nfnetlink_has_listeners(unsigned int group)
 179 {
 180         return netlink_has_listeners(nfnl, group);
 181 }
 182 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 183
 184 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 185 {
 186         int err = 0;
 187
 188         NETLINK_CB(skb).dst_group = group;
 189         if (echo)
 190                 atomic_inc(&skb->users);
 191         netlink_broadcast(nfnl, skb, pid, group, gfp_any());
 192         if (echo)
 193                 err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
 194
 195         return err;
 196 }
 197
 198 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
 199 {
 200         return netlink_unicast(nfnl, skb, pid, flags);
 201 }
 202
 203 /* Process one complete nfnetlink message. */
 204 static int nfnetlink_rcv_msg(struct sk_buff *skb,
 205                                     struct nlmsghdr *nlh, int *errp)
 206 {
 207         struct nfnl_callback *nc;
 208         struct nfnetlink_subsystem *ss;
 209         int type, err = 0;
 210
 211         if (security_netlink_recv(skb, CAP_NET_ADMIN)) {
 212                 *errp = -EPERM;
 213                 return -1;
 214         }
 215
 216         /* Only requests are handled by kernel now. */
 217         if (!(nlh->nlmsg_flags & NLM_F_REQUEST))
 218                 return 0;
 219
 220         /* All the messages must at least contain nfgenmsg */
 221         if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg)))
 222                 return 0;
 223
 224         type = nlh->nlmsg_type;
 225         ss = nfnetlink_get_subsys(type);
 226         if (!ss) {
 227 #ifdef CONFIG_KMOD
 228                 /* don't call nfnl_unlock, since it would reenter
 229                  * with further packet processing */
 230                 __nfnl_unlock();
 231                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 232                 nfnl_lock();
 233                 ss = nfnetlink_get_subsys(type);
 234                 if (!ss)
 235 #endif
 236                         goto err_inval;
 237         }
 238
 239         nc = nfnetlink_find_client(type, ss);
 240         if (!nc)
 241                 goto err_inval;
 242
 243         {
 244                 u_int16_t attr_count =
 245                         ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count;
 246                 struct nfattr *cda[attr_count];
 247
 248                 memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 249
 250                 err = nfnetlink_check_attributes(ss, nlh, cda);
 251                 if (err < 0)
 252                         goto err_inval;
 253
 254                 err = nc->call(nfnl, skb, nlh, cda, errp);
 255                 *errp = err;
 256                 return err;
 257         }
 258
 259 err_inval:
 260         *errp = -EINVAL;
 261         return -1;
 262 }
 263
 264 static void nfnetlink_rcv(struct sock *sk, int len)
 265 {
 266         unsigned int qlen = 0;
 267
 268         do {
 269                 if (nfnl_trylock())
 270                         return;
 271                 netlink_run_queue(sk, &qlen, nfnetlink_rcv_msg);
 272                 __nfnl_unlock();
 273         } while (qlen);
 274 }
 275
 276 static void __exit nfnetlink_exit(void)
 277 {
 278         printk("Removing netfilter NETLINK layer.\n");
 279         sock_release(nfnl->sk_socket);
 280         return;
 281 }
 282
 283 static int __init nfnetlink_init(void)
 284 {
 285         printk("Netfilter messages via NETLINK v%s.\n", nfversion);
 286
 287         nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX,
 288                                      nfnetlink_rcv, THIS_MODULE);
 289         if (!nfnl) {
 290                 printk(KERN_ERR "cannot initialize nfnetlink!\n");
 291                 return -1;
 292         }
 293
 294         return 0;
 295 }
 296
 297 module_init(nfnetlink_init);
 298 module_exit(nfnetlink_exit);
 299
 300 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
 301 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
 302 EXPORT_SYMBOL_GPL(nfnetlink_send);
 303 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 304 EXPORT_SYMBOL_GPL(nfattr_parse);
 305 EXPORT_SYMBOL_GPL(__nfa_fill);