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 #include <linux/spinlock.h>
  34
  35 #include <linux/netfilter.h>
  36 #include <linux/netlink.h>
  37 #include <linux/netfilter/nfnetlink.h>
  38
  39 MODULE_LICENSE("GPL");
  40 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  41 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
  42
  43 static char __initdata nfversion[] = "0.30";
  44
  45 static struct sock *nfnl = NULL;
  46 static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
  47 static DEFINE_MUTEX(nfnl_mutex);
  48
  49 static void nfnl_lock(void)
  50 {
  51         mutex_lock(&nfnl_mutex);
  52 }
  53
  54 static int nfnl_trylock(void)
  55 {
  56         return !mutex_trylock(&nfnl_mutex);
  57 }
  58
  59 static void __nfnl_unlock(void)
  60 {
  61         mutex_unlock(&nfnl_mutex);
  62 }
  63
  64 static void nfnl_unlock(void)
  65 {
  66         mutex_unlock(&nfnl_mutex);
  67         if (nfnl->sk_receive_queue.qlen)
  68                 nfnl->sk_data_ready(nfnl, 0);
  69 }
  70
  71 int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
  72 {
  73         nfnl_lock();
  74         if (subsys_table[n->subsys_id]) {
  75                 nfnl_unlock();
  76                 return -EBUSY;
  77         }
  78         subsys_table[n->subsys_id] = n;
  79         nfnl_unlock();
  80
  81         return 0;
  82 }
  83
  84 int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
  85 {
  86         nfnl_lock();
  87         subsys_table[n->subsys_id] = NULL;
  88         nfnl_unlock();
  89
  90         return 0;
  91 }
  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
 127 void nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
 128 {
 129         memset(tb, 0, sizeof(struct nfattr *) * maxattr);
 130
 131         while (NFA_OK(nfa, len)) {
 132                 unsigned flavor = NFA_TYPE(nfa);
 133                 if (flavor && flavor <= maxattr)
 134                         tb[flavor-1] = nfa;
 135                 nfa = NFA_NEXT(nfa, len);
 136         }
 137 }
 138
 139 /**
 140  * nfnetlink_check_attributes - check and parse nfnetlink attributes
 141  *
 142  * subsys: nfnl subsystem for which this message is to be parsed
 143  * nlmsghdr: netlink message to be checked/parsed
 144  * cda: array of pointers, needs to be at least subsys->attr_count big
 145  *
 146  */
 147 static int
 148 nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
 149                            struct nlmsghdr *nlh, struct nfattr *cda[])
 150 {
 151         int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 152         u_int16_t attr_count;
 153         u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 154
 155         attr_count = subsys->cb[cb_id].attr_count;
 156         memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 157
 158         /* check attribute lengths. */
 159         if (likely(nlh->nlmsg_len > min_len)) {
 160                 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
 161                 int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 162
 163                 while (NFA_OK(attr, attrlen)) {
 164                         unsigned flavor = NFA_TYPE(attr);
 165                         if (flavor) {
 166                                 if (flavor > attr_count)
 167                                         return -EINVAL;
 168                                 cda[flavor - 1] = attr;
 169                         }
 170                         attr = NFA_NEXT(attr, attrlen);
 171                 }
 172         }
 173
 174         /* implicit: if nlmsg_len == min_len, we return 0, and an empty
 175          * (zeroed) cda[] array. The message is valid, but empty. */
 176
 177         return 0;
 178 }
 179
 180 int nfnetlink_has_listeners(unsigned int group)
 181 {
 182         return netlink_has_listeners(nfnl, group);
 183 }
 184 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 185
 186 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 187 {
 188         int err = 0;
 189
 190         NETLINK_CB(skb).dst_group = group;
 191         if (echo)
 192                 atomic_inc(&skb->users);
 193         netlink_broadcast(nfnl, skb, pid, group, gfp_any());
 194         if (echo)
 195                 err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
 196
 197         return err;
 198 }
 199
 200 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
 201 {
 202         return netlink_unicast(nfnl, skb, pid, flags);
 203 }
 204
 205 /* Process one complete nfnetlink message. */
 206 static int nfnetlink_rcv_msg(struct sk_buff *skb,
 207                                     struct nlmsghdr *nlh, int *errp)
 208 {
 209         struct nfnl_callback *nc;
 210         struct nfnetlink_subsystem *ss;
 211         int type, err = 0;
 212
 213         if (security_netlink_recv(skb, CAP_NET_ADMIN)) {
 214                 *errp = -EPERM;
 215                 return -1;
 216         }
 217
 218         /* Only requests are handled by kernel now. */
 219         if (!(nlh->nlmsg_flags & NLM_F_REQUEST))
 220                 return 0;
 221
 222         /* All the messages must at least contain nfgenmsg */
 223         if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg)))
 224                 return 0;
 225
 226         type = nlh->nlmsg_type;
 227         ss = nfnetlink_get_subsys(type);
 228         if (!ss) {
 229 #ifdef CONFIG_KMOD
 230                 /* don't call nfnl_unlock, since it would reenter
 231                  * with further packet processing */
 232                 __nfnl_unlock();
 233                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 234                 nfnl_lock();
 235                 ss = nfnetlink_get_subsys(type);
 236                 if (!ss)
 237 #endif
 238                         goto err_inval;
 239         }
 240
 241         nc = nfnetlink_find_client(type, ss);
 242         if (!nc)
 243                 goto err_inval;
 244
 245         {
 246                 u_int16_t attr_count =
 247                         ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count;
 248                 struct nfattr *cda[attr_count];
 249
 250                 memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 251
 252                 err = nfnetlink_check_attributes(ss, nlh, cda);
 253                 if (err < 0)
 254                         goto err_inval;
 255
 256                 err = nc->call(nfnl, skb, nlh, cda, errp);
 257                 *errp = err;
 258                 return err;
 259         }
 260
 261 err_inval:
 262         *errp = -EINVAL;
 263         return -1;
 264 }
 265
 266 static void nfnetlink_rcv(struct sock *sk, int len)
 267 {
 268         unsigned int qlen = 0;
 269
 270         do {
 271                 if (nfnl_trylock())
 272                         return;
 273                 netlink_run_queue(sk, &qlen, nfnetlink_rcv_msg);
 274                 __nfnl_unlock();
 275         } while (qlen);
 276 }
 277
 278 static void __exit nfnetlink_exit(void)
 279 {
 280         printk("Removing netfilter NETLINK layer.\n");
 281         sock_release(nfnl->sk_socket);
 282         return;
 283 }
 284
 285 static int __init nfnetlink_init(void)
 286 {
 287         printk("Netfilter messages via NETLINK v%s.\n", nfversion);
 288
 289         nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX,
 290                                      nfnetlink_rcv, THIS_MODULE);
 291         if (!nfnl) {
 292                 printk(KERN_ERR "cannot initialize nfnetlink!\n");
 293                 return -1;
 294         }
 295
 296         return 0;
 297 }
 298
 299 module_init(nfnetlink_init);
 300 module_exit(nfnetlink_exit);
 301
 302 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
 303 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
 304 EXPORT_SYMBOL_GPL(nfnetlink_send);
 305 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 306 EXPORT_SYMBOL_GPL(nfattr_parse);
 307 EXPORT_SYMBOL_GPL(__nfa_fill);