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 by Pablo Neira Ayuso <pablo@eurodev.net>
   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 <linux/init.h>
  32 #include <linux/spinlock.h>
  33
  34 #include <linux/netfilter.h>
  35 #include <linux/netlink.h>
  36 #include <linux/netfilter/nfnetlink.h>
  37
  38 MODULE_LICENSE("GPL");
  39 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  40 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
  41
  42 static char __initdata nfversion[] = "0.30";
  43
  44 #if 0
  45 #define DEBUGP(format, args...) \
  46                 printk(KERN_DEBUG "%s(%d):%s(): " format, __FILE__, \
  47                         __LINE__, __FUNCTION__, ## args)
  48 #else
  49 #define DEBUGP(format, args...)
  50 #endif
  51
  52 static struct sock *nfnl = NULL;
  53 static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
  54 DECLARE_MUTEX(nfnl_sem);
  55
  56 void nfnl_lock(void)
  57 {
  58         nfnl_shlock();
  59 }
  60
  61 void nfnl_unlock(void)
  62 {
  63         nfnl_shunlock();
  64 }
  65
  66 int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
  67 {
  68         DEBUGP("registering subsystem ID %u\n", n->subsys_id);
  69
  70         nfnl_lock();
  71         if (subsys_table[n->subsys_id]) {
  72                 nfnl_unlock();
  73                 return -EBUSY;
  74         }
  75         subsys_table[n->subsys_id] = n;
  76         nfnl_unlock();
  77
  78         return 0;
  79 }
  80
  81 int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
  82 {
  83         DEBUGP("unregistering subsystem ID %u\n", n->subsys_id);
  84
  85         nfnl_lock();
  86         subsys_table[n->subsys_id] = NULL;
  87         nfnl_unlock();
  88
  89         return 0;
  90 }
  91
  92 static inline struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  93 {
  94         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  95
  96         if (subsys_id >= NFNL_SUBSYS_COUNT
  97             || subsys_table[subsys_id] == NULL)
  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                 DEBUGP("msgtype %u >= %u, returning\n", type, ss->cb_count);
 110                 return NULL;
 111         }
 112
 113         return &ss->cb[cb_id];
 114 }
 115
 116 void __nfa_fill(struct sk_buff *skb, int attrtype, int attrlen,
 117                 const void *data)
 118 {
 119         struct nfattr *nfa;
 120         int size = NFA_LENGTH(attrlen);
 121
 122         nfa = (struct nfattr *)skb_put(skb, NFA_ALIGN(size));
 123         nfa->nfa_type = attrtype;
 124         nfa->nfa_len  = size;
 125         memcpy(NFA_DATA(nfa), data, attrlen);
 126         memset(NFA_DATA(nfa) + attrlen, 0, NFA_ALIGN(size) - size);
 127 }
 128
 129 void nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
 130 {
 131         memset(tb, 0, sizeof(struct nfattr *) * maxattr);
 132
 133         while (NFA_OK(nfa, len)) {
 134                 unsigned flavor = NFA_TYPE(nfa);
 135                 if (flavor && flavor <= maxattr)
 136                         tb[flavor-1] = nfa;
 137                 nfa = NFA_NEXT(nfa, len);
 138         }
 139 }
 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;
 154         u_int16_t attr_count;
 155         u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 156
 157         if (unlikely(cb_id >= subsys->cb_count)) {
 158                 DEBUGP("msgtype %u >= %u, returning\n",
 159                         cb_id, subsys->cb_count);
 160                 return -EINVAL;
 161         }
 162
 163         min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 164         if (unlikely(nlh->nlmsg_len < min_len))
 165                 return -EINVAL;
 166
 167         attr_count = subsys->cb[cb_id].attr_count;
 168         memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 169
 170         /* check attribute lengths. */
 171         if (likely(nlh->nlmsg_len > min_len)) {
 172                 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
 173                 int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 174
 175                 while (NFA_OK(attr, attrlen)) {
 176                         unsigned flavor = NFA_TYPE(attr);
 177                         if (flavor) {
 178                                 if (flavor > attr_count)
 179                                         return -EINVAL;
 180                                 cda[flavor - 1] = attr;
 181                         }
 182                         attr = NFA_NEXT(attr, attrlen);
 183                 }
 184         }
 185
 186         /* implicit: if nlmsg_len == min_len, we return 0, and an empty
 187          * (zeroed) cda[] array. The message is valid, but empty. */
 188
 189         return 0;
 190 }
 191
 192 int nfnetlink_has_listeners(unsigned int group)
 193 {
 194         return netlink_has_listeners(nfnl, group);
 195 }
 196 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 197
 198 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 199 {
 200         int err = 0;
 201
 202         NETLINK_CB(skb).dst_group = group;
 203         if (echo)
 204                 atomic_inc(&skb->users);
 205         netlink_broadcast(nfnl, skb, pid, group, gfp_any());
 206         if (echo)
 207                 err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
 208
 209         return err;
 210 }
 211
 212 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
 213 {
 214         return netlink_unicast(nfnl, skb, pid, flags);
 215 }
 216
 217 /* Process one complete nfnetlink message. */
 218 static int nfnetlink_rcv_msg(struct sk_buff *skb,
 219                                     struct nlmsghdr *nlh, int *errp)
 220 {
 221         struct nfnl_callback *nc;
 222         struct nfnetlink_subsystem *ss;
 223         int type, err = 0;
 224
 225         DEBUGP("entered; subsys=%u, msgtype=%u\n",
 226                  NFNL_SUBSYS_ID(nlh->nlmsg_type),
 227                  NFNL_MSG_TYPE(nlh->nlmsg_type));
 228
 229         if (security_netlink_recv(skb, CAP_NET_ADMIN)) {
 230                 DEBUGP("missing CAP_NET_ADMIN\n");
 231                 *errp = -EPERM;
 232                 return -1;
 233         }
 234
 235         /* Only requests are handled by kernel now. */
 236         if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
 237                 DEBUGP("received non-request message\n");
 238                 return 0;
 239         }
 240
 241         /* All the messages must at least contain nfgenmsg */
 242         if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg))) {
 243                 DEBUGP("received message was too short\n");
 244                 return 0;
 245         }
 246
 247         type = nlh->nlmsg_type;
 248         ss = nfnetlink_get_subsys(type);
 249         if (!ss) {
 250 #ifdef CONFIG_KMOD
 251                 /* don't call nfnl_shunlock, since it would reenter
 252                  * with further packet processing */
 253                 up(&nfnl_sem);
 254                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 255                 nfnl_shlock();
 256                 ss = nfnetlink_get_subsys(type);
 257                 if (!ss)
 258 #endif
 259                         goto err_inval;
 260         }
 261
 262         nc = nfnetlink_find_client(type, ss);
 263         if (!nc) {
 264                 DEBUGP("unable to find client for type %d\n", type);
 265                 goto err_inval;
 266         }
 267
 268         {
 269                 u_int16_t attr_count =
 270                         ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count;
 271                 struct nfattr *cda[attr_count];
 272
 273                 memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 274
 275                 err = nfnetlink_check_attributes(ss, nlh, cda);
 276                 if (err < 0)
 277                         goto err_inval;
 278
 279                 DEBUGP("calling handler\n");
 280                 err = nc->call(nfnl, skb, nlh, cda, errp);
 281                 *errp = err;
 282                 return err;
 283         }
 284
 285 err_inval:
 286         DEBUGP("returning -EINVAL\n");
 287         *errp = -EINVAL;
 288         return -1;
 289 }
 290
 291 /* Process one packet of messages. */
 292 static inline int nfnetlink_rcv_skb(struct sk_buff *skb)
 293 {
 294         int err;
 295         struct nlmsghdr *nlh;
 296
 297         while (skb->len >= NLMSG_SPACE(0)) {
 298                 u32 rlen;
 299
 300                 nlh = (struct nlmsghdr *)skb->data;
 301                 if (nlh->nlmsg_len < sizeof(struct nlmsghdr)
 302                     || skb->len < nlh->nlmsg_len)
 303                         return 0;
 304                 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
 305                 if (rlen > skb->len)
 306                         rlen = skb->len;
 307                 if (nfnetlink_rcv_msg(skb, nlh, &err)) {
 308                         if (!err)
 309                                 return -1;
 310                         netlink_ack(skb, nlh, err);
 311                 } else
 312                         if (nlh->nlmsg_flags & NLM_F_ACK)
 313                                 netlink_ack(skb, nlh, 0);
 314                 skb_pull(skb, rlen);
 315         }
 316
 317         return 0;
 318 }
 319
 320 static void nfnetlink_rcv(struct sock *sk, int len)
 321 {
 322         do {
 323                 struct sk_buff *skb;
 324
 325                 if (nfnl_shlock_nowait())
 326                         return;
 327
 328                 while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
 329                         if (nfnetlink_rcv_skb(skb)) {
 330                                 if (skb->len)
 331                                         skb_queue_head(&sk->sk_receive_queue,
 332                                                        skb);
 333                                 else
 334                                         kfree_skb(skb);
 335                                 break;
 336                         }
 337                         kfree_skb(skb);
 338                 }
 339
 340                 /* don't call nfnl_shunlock, since it would reenter
 341                  * with further packet processing */
 342                 up(&nfnl_sem);
 343         } while(nfnl && nfnl->sk_receive_queue.qlen);
 344 }
 345
 346 static void __exit nfnetlink_exit(void)
 347 {
 348         printk("Removing netfilter NETLINK layer.\n");
 349         sock_release(nfnl->sk_socket);
 350         return;
 351 }
 352
 353 static int __init nfnetlink_init(void)
 354 {
 355         printk("Netfilter messages via NETLINK v%s.\n", nfversion);
 356
 357         nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX,
 358                                      nfnetlink_rcv, THIS_MODULE);
 359         if (!nfnl) {
 360                 printk(KERN_ERR "cannot initialize nfnetlink!\n");
 361                 return -1;
 362         }
 363
 364         return 0;
 365 }
 366
 367 module_init(nfnetlink_init);
 368 module_exit(nfnetlink_exit);
 369
 370 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
 371 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
 372 EXPORT_SYMBOL_GPL(nfnetlink_send);
 373 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 374 EXPORT_SYMBOL_GPL(nfattr_parse);
 375 EXPORT_SYMBOL_GPL(__nfa_fill);