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/sched.h>
  23 #include <linux/timer.h>
  24 #include <linux/string.h>
  25 #include <linux/sockios.h>
  26 #include <linux/net.h>
  27 #include <linux/fcntl.h>
  28 #include <linux/skbuff.h>
  29 #include <asm/uaccess.h>
  30 #include <asm/system.h>
  31 #include <net/sock.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 #if 0
  46 #define DEBUGP(format, args...) \
  47                 printk(KERN_DEBUG "%s(%d):%s(): " format, __FILE__, \
  48                         __LINE__, __FUNCTION__, ## args)
  49 #else
  50 #define DEBUGP(format, args...)
  51 #endif
  52
  53 static struct sock *nfnl = NULL;
  54 static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
  55 DECLARE_MUTEX(nfnl_sem);
  56
  57 void nfnl_lock(void)
  58 {
  59         nfnl_shlock();
  60 }
  61
  62 void nfnl_unlock(void)
  63 {
  64         nfnl_shunlock();
  65 }
  66
  67 int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
  68 {
  69         DEBUGP("registering subsystem ID %u\n", n->subsys_id);
  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         DEBUGP("unregistering subsystem ID %u\n", n->subsys_id);
  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             || subsys_table[subsys_id] == NULL)
  99                 return NULL;
 100
 101         return subsys_table[subsys_id];
 102 }
 103
 104 static inline struct nfnl_callback *
 105 nfnetlink_find_client(u_int16_t type, struct nfnetlink_subsystem *ss)
 106 {
 107         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 108
 109         if (cb_id >= ss->cb_count) {
 110                 DEBUGP("msgtype %u >= %u, returning\n", type, ss->cb_count);
 111                 return NULL;
 112         }
 113
 114         return &ss->cb[cb_id];
 115 }
 116
 117 void __nfa_fill(struct sk_buff *skb, int attrtype, int attrlen,
 118                 const void *data)
 119 {
 120         struct nfattr *nfa;
 121         int size = NFA_LENGTH(attrlen);
 122
 123         nfa = (struct nfattr *)skb_put(skb, NFA_ALIGN(size));
 124         nfa->nfa_type = attrtype;
 125         nfa->nfa_len  = size;
 126         memcpy(NFA_DATA(nfa), data, attrlen);
 127         memset(NFA_DATA(nfa) + attrlen, 0, NFA_ALIGN(size) - size);
 128 }
 129
 130 void nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
 131 {
 132         memset(tb, 0, sizeof(struct nfattr *) * maxattr);
 133
 134         while (NFA_OK(nfa, len)) {
 135                 unsigned flavor = NFA_TYPE(nfa);
 136                 if (flavor && flavor <= maxattr)
 137                         tb[flavor-1] = nfa;
 138                 nfa = NFA_NEXT(nfa, len);
 139         }
 140 }
 141
 142 /**
 143  * nfnetlink_check_attributes - check and parse nfnetlink attributes
 144  *
 145  * subsys: nfnl subsystem for which this message is to be parsed
 146  * nlmsghdr: netlink message to be checked/parsed
 147  * cda: array of pointers, needs to be at least subsys->attr_count big
 148  *
 149  */
 150 static int
 151 nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
 152                            struct nlmsghdr *nlh, struct nfattr *cda[])
 153 {
 154         int min_len;
 155         u_int16_t attr_count;
 156         u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 157
 158         if (unlikely(cb_id >= subsys->cb_count)) {
 159                 DEBUGP("msgtype %u >= %u, returning\n",
 160                         cb_id, subsys->cb_count);
 161                 return -EINVAL;
 162         }
 163
 164         min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
 165         if (unlikely(nlh->nlmsg_len < min_len))
 166                 return -EINVAL;
 167
 168         attr_count = subsys->cb[cb_id].attr_count;
 169         memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 170
 171         /* check attribute lengths. */
 172         if (likely(nlh->nlmsg_len > min_len)) {
 173                 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
 174                 int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 175
 176                 while (NFA_OK(attr, attrlen)) {
 177                         unsigned flavor = NFA_TYPE(attr);
 178                         if (flavor) {
 179                                 if (flavor > attr_count)
 180                                         return -EINVAL;
 181                                 cda[flavor - 1] = attr;
 182                         }
 183                         attr = NFA_NEXT(attr, attrlen);
 184                 }
 185         }
 186
 187         /* implicit: if nlmsg_len == min_len, we return 0, and an empty
 188          * (zeroed) cda[] array. The message is valid, but empty. */
 189
 190         return 0;
 191 }
 192
 193 int nfnetlink_has_listeners(unsigned int group)
 194 {
 195         return netlink_has_listeners(nfnl, group);
 196 }
 197 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 198
 199 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 200 {
 201         gfp_t allocation = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
 202         int err = 0;
 203
 204         NETLINK_CB(skb).dst_group = group;
 205         if (echo)
 206                 atomic_inc(&skb->users);
 207         netlink_broadcast(nfnl, skb, pid, group, allocation);
 208         if (echo)
 209                 err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
 210
 211         return err;
 212 }
 213
 214 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
 215 {
 216         return netlink_unicast(nfnl, skb, pid, flags);
 217 }
 218
 219 /* Process one complete nfnetlink message. */
 220 static int nfnetlink_rcv_msg(struct sk_buff *skb,
 221                                     struct nlmsghdr *nlh, int *errp)
 222 {
 223         struct nfnl_callback *nc;
 224         struct nfnetlink_subsystem *ss;
 225         int type, err = 0;
 226
 227         DEBUGP("entered; subsys=%u, msgtype=%u\n",
 228                  NFNL_SUBSYS_ID(nlh->nlmsg_type),
 229                  NFNL_MSG_TYPE(nlh->nlmsg_type));
 230
 231         if (security_netlink_recv(skb, CAP_NET_ADMIN)) {
 232                 DEBUGP("missing CAP_NET_ADMIN\n");
 233                 *errp = -EPERM;
 234                 return -1;
 235         }
 236
 237         /* Only requests are handled by kernel now. */
 238         if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
 239                 DEBUGP("received non-request message\n");
 240                 return 0;
 241         }
 242
 243         /* All the messages must at least contain nfgenmsg */
 244         if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg))) {
 245                 DEBUGP("received message was too short\n");
 246                 return 0;
 247         }
 248
 249         type = nlh->nlmsg_type;
 250         ss = nfnetlink_get_subsys(type);
 251         if (!ss) {
 252 #ifdef CONFIG_KMOD
 253                 /* don't call nfnl_shunlock, since it would reenter
 254                  * with further packet processing */
 255                 up(&nfnl_sem);
 256                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 257                 nfnl_shlock();
 258                 ss = nfnetlink_get_subsys(type);
 259                 if (!ss)
 260 #endif
 261                         goto err_inval;
 262         }
 263
 264         nc = nfnetlink_find_client(type, ss);
 265         if (!nc) {
 266                 DEBUGP("unable to find client for type %d\n", type);
 267                 goto err_inval;
 268         }
 269
 270         {
 271                 u_int16_t attr_count =
 272                         ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count;
 273                 struct nfattr *cda[attr_count];
 274
 275                 memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 276
 277                 err = nfnetlink_check_attributes(ss, nlh, cda);
 278                 if (err < 0)
 279                         goto err_inval;
 280
 281                 DEBUGP("calling handler\n");
 282                 err = nc->call(nfnl, skb, nlh, cda, errp);
 283                 *errp = err;
 284                 return err;
 285         }
 286
 287 err_inval:
 288         DEBUGP("returning -EINVAL\n");
 289         *errp = -EINVAL;
 290         return -1;
 291 }
 292
 293 /* Process one packet of messages. */
 294 static inline int nfnetlink_rcv_skb(struct sk_buff *skb)
 295 {
 296         int err;
 297         struct nlmsghdr *nlh;
 298
 299         while (skb->len >= NLMSG_SPACE(0)) {
 300                 u32 rlen;
 301
 302                 nlh = (struct nlmsghdr *)skb->data;
 303                 if (nlh->nlmsg_len < sizeof(struct nlmsghdr)
 304                     || skb->len < nlh->nlmsg_len)
 305                         return 0;
 306                 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
 307                 if (rlen > skb->len)
 308                         rlen = skb->len;
 309                 if (nfnetlink_rcv_msg(skb, nlh, &err)) {
 310                         if (!err)
 311                                 return -1;
 312                         netlink_ack(skb, nlh, err);
 313                 } else
 314                         if (nlh->nlmsg_flags & NLM_F_ACK)
 315                                 netlink_ack(skb, nlh, 0);
 316                 skb_pull(skb, rlen);
 317         }
 318
 319         return 0;
 320 }
 321
 322 static void nfnetlink_rcv(struct sock *sk, int len)
 323 {
 324         do {
 325                 struct sk_buff *skb;
 326
 327                 if (nfnl_shlock_nowait())
 328                         return;
 329
 330                 while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
 331                         if (nfnetlink_rcv_skb(skb)) {
 332                                 if (skb->len)
 333                                         skb_queue_head(&sk->sk_receive_queue,
 334                                                        skb);
 335                                 else
 336                                         kfree_skb(skb);
 337                                 break;
 338                         }
 339                         kfree_skb(skb);
 340                 }
 341
 342                 /* don't call nfnl_shunlock, since it would reenter
 343                  * with further packet processing */
 344                 up(&nfnl_sem);
 345         } while(nfnl && nfnl->sk_receive_queue.qlen);
 346 }
 347
 348 static void __exit nfnetlink_exit(void)
 349 {
 350         printk("Removing netfilter NETLINK layer.\n");
 351         sock_release(nfnl->sk_socket);
 352         return;
 353 }
 354
 355 static int __init nfnetlink_init(void)
 356 {
 357         printk("Netfilter messages via NETLINK v%s.\n", nfversion);
 358
 359         nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX,
 360                                      nfnetlink_rcv, THIS_MODULE);
 361         if (!nfnl) {
 362                 printk(KERN_ERR "cannot initialize nfnetlink!\n");
 363                 return -1;
 364         }
 365
 366         return 0;
 367 }
 368
 369 module_init(nfnetlink_init);
 370 module_exit(nfnetlink_exit);
 371
 372 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
 373 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
 374 EXPORT_SYMBOL_GPL(nfnetlink_send);
 375 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 376 EXPORT_SYMBOL_GPL(nfattr_parse);
 377 EXPORT_SYMBOL_GPL(__nfa_fill);