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/config.h>
  18 #include <linux/module.h>
  19 #include <linux/types.h>
  20 #include <linux/socket.h>
  21 #include <linux/kernel.h>
  22 #include <linux/major.h>
  23 #include <linux/sched.h>
  24 #include <linux/timer.h>
  25 #include <linux/string.h>
  26 #include <linux/sockios.h>
  27 #include <linux/net.h>
  28 #include <linux/fcntl.h>
  29 #include <linux/skbuff.h>
  30 #include <asm/uaccess.h>
  31 #include <asm/system.h>
  32 #include <net/sock.h>
  33 #include <linux/init.h>
  34 #include <linux/spinlock.h>
  35
  36 #include <linux/netfilter.h>
  37 #include <linux/netlink.h>
  38 #include <linux/netfilter/nfnetlink.h>
  39
  40 MODULE_LICENSE("GPL");
  41 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  42 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
  43
  44 static char __initdata nfversion[] = "0.30";
  45
  46 #if 0
  47 #define DEBUGP(format, args...) \
  48                 printk(KERN_DEBUG "%s(%d):%s(): " format, __FILE__, \
  49                         __LINE__, __FUNCTION__, ## args)
  50 #else
  51 #define DEBUGP(format, args...)
  52 #endif
  53
  54 static struct sock *nfnl = NULL;
  55 static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
  56 DECLARE_MUTEX(nfnl_sem);
  57
  58 void nfnl_lock(void)
  59 {
  60         nfnl_shlock();
  61 }
  62
  63 void nfnl_unlock(void)
  64 {
  65         nfnl_shunlock();
  66 }
  67
  68 int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
  69 {
  70         DEBUGP("registering subsystem ID %u\n", n->subsys_id);
  71
  72         nfnl_lock();
  73         if (subsys_table[n->subsys_id]) {
  74                 nfnl_unlock();
  75                 return -EBUSY;
  76         }
  77         subsys_table[n->subsys_id] = n;
  78         nfnl_unlock();
  79
  80         return 0;
  81 }
  82
  83 int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
  84 {
  85         DEBUGP("unregistering subsystem ID %u\n", n->subsys_id);
  86
  87         nfnl_lock();
  88         subsys_table[n->subsys_id] = NULL;
  89         nfnl_unlock();
  90
  91         return 0;
  92 }
  93
  94 static inline struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  95 {
  96         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  97
  98         if (subsys_id >= NFNL_SUBSYS_COUNT
  99             || subsys_table[subsys_id] == NULL)
 100                 return NULL;
 101
 102         return subsys_table[subsys_id];
 103 }
 104
 105 static inline struct nfnl_callback *
 106 nfnetlink_find_client(u_int16_t type, struct nfnetlink_subsystem *ss)
 107 {
 108         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 109
 110         if (cb_id >= ss->cb_count) {
 111                 DEBUGP("msgtype %u >= %u, returning\n", type, ss->cb_count);
 112                 return NULL;
 113         }
 114
 115         return &ss->cb[cb_id];
 116 }
 117
 118 void __nfa_fill(struct sk_buff *skb, int attrtype, int attrlen,
 119                 const void *data)
 120 {
 121         struct nfattr *nfa;
 122         int size = NFA_LENGTH(attrlen);
 123
 124         nfa = (struct nfattr *)skb_put(skb, NFA_ALIGN(size));
 125         nfa->nfa_type = attrtype;
 126         nfa->nfa_len  = size;
 127         memcpy(NFA_DATA(nfa), data, attrlen);
 128         memset(NFA_DATA(nfa) + attrlen, 0, NFA_ALIGN(size) - size);
 129 }
 130
 131 int nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
 132 {
 133         memset(tb, 0, sizeof(struct nfattr *) * maxattr);
 134
 135         while (NFA_OK(nfa, len)) {
 136                 unsigned flavor = nfa->nfa_type;
 137                 if (flavor && flavor <= maxattr)
 138                         tb[flavor-1] = nfa;
 139                 nfa = NFA_NEXT(nfa, len);
 140         }
 141
 142         return 0;
 143 }
 144
 145 /**
 146  * nfnetlink_check_attributes - check and parse nfnetlink attributes
 147  *
 148  * subsys: nfnl subsystem for which this message is to be parsed
 149  * nlmsghdr: netlink message to be checked/parsed
 150  * cda: array of pointers, needs to be at least subsys->attr_count big
 151  *
 152  */
 153 static int
 154 nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
 155                            struct nlmsghdr *nlh, struct nfattr *cda[])
 156 {
 157         int min_len;
 158         u_int16_t attr_count;
 159         u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 160
 161         if (unlikely(cb_id >= subsys->cb_count)) {
 162                 DEBUGP("msgtype %u >= %u, returning\n",
 163                         cb_id, subsys->cb_count);
 164                 return -EINVAL;
 165         }
 166
 167         min_len = NLMSG_ALIGN(sizeof(struct nfgenmsg));
 168         if (unlikely(nlh->nlmsg_len < min_len))
 169                 return -EINVAL;
 170
 171         attr_count = subsys->cb[cb_id].attr_count;
 172         memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 173
 174         /* check attribute lengths. */
 175         if (likely(nlh->nlmsg_len > min_len)) {
 176                 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
 177                 int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 178
 179                 while (NFA_OK(attr, attrlen)) {
 180                         unsigned flavor = attr->nfa_type;
 181                         if (flavor) {
 182                                 if (flavor > attr_count)
 183                                         return -EINVAL;
 184                                 cda[flavor - 1] = attr;
 185                         }
 186                         attr = NFA_NEXT(attr, attrlen);
 187                 }
 188         }
 189
 190         /* implicit: if nlmsg_len == min_len, we return 0, and an empty
 191          * (zeroed) cda[] array. The message is valid, but empty. */
 192
 193         return 0;
 194 }
 195
 196 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 197 {
 198         int allocation = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
 199         int err = 0;
 200
 201         NETLINK_CB(skb).dst_group = group;
 202         if (echo)
 203                 atomic_inc(&skb->users);
 204         netlink_broadcast(nfnl, skb, pid, group, allocation);
 205         if (echo)
 206                 err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
 207
 208         return err;
 209 }
 210
 211 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
 212 {
 213         return netlink_unicast(nfnl, skb, pid, flags);
 214 }
 215
 216 /* Process one complete nfnetlink message. */
 217 static inline int nfnetlink_rcv_msg(struct sk_buff *skb,
 218                                     struct nlmsghdr *nlh, int *errp)
 219 {
 220         struct nfnl_callback *nc;
 221         struct nfnetlink_subsystem *ss;
 222         int type, err = 0;
 223
 224         DEBUGP("entered; subsys=%u, msgtype=%u\n",
 225                  NFNL_SUBSYS_ID(nlh->nlmsg_type),
 226                  NFNL_MSG_TYPE(nlh->nlmsg_type));
 227
 228         /* Only requests are handled by kernel now. */
 229         if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
 230                 DEBUGP("received non-request message\n");
 231                 return 0;
 232         }
 233
 234         /* All the messages must at least contain nfgenmsg */
 235         if (nlh->nlmsg_len <
 236                         NLMSG_LENGTH(NLMSG_ALIGN(sizeof(struct nfgenmsg)))) {
 237                 DEBUGP("received message was too short\n");
 238                 return 0;
 239         }
 240
 241         type = nlh->nlmsg_type;
 242         ss = nfnetlink_get_subsys(type);
 243         if (!ss) {
 244 #ifdef CONFIG_KMOD
 245                 /* don't call nfnl_shunlock, since it would reenter
 246                  * with further packet processing */
 247                 up(&nfnl_sem);
 248                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 249                 nfnl_shlock();
 250                 ss = nfnetlink_get_subsys(type);
 251                 if (!ss)
 252 #endif
 253                 goto err_inval;
 254         }
 255
 256         nc = nfnetlink_find_client(type, ss);
 257         if (!nc) {
 258                 DEBUGP("unable to find client for type %d\n", type);
 259                 goto err_inval;
 260         }
 261
 262         if (nc->cap_required &&
 263             !cap_raised(NETLINK_CB(skb).eff_cap, nc->cap_required)) {
 264                 DEBUGP("permission denied for type %d\n", type);
 265                 *errp = -EPERM;
 266                 return -1;
 267         }
 268
 269         {
 270                 u_int16_t attr_count =
 271                         ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count;
 272                 struct nfattr *cda[attr_count];
 273
 274                 memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 275
 276                 err = nfnetlink_check_attributes(ss, nlh, cda);
 277                 if (err < 0)
 278                         goto err_inval;
 279
 280                 DEBUGP("calling handler\n");
 281                 err = nc->call(nfnl, skb, nlh, cda, errp);
 282                 *errp = err;
 283                 return err;
 284         }
 285
 286 err_inval:
 287         DEBUGP("returning -EINVAL\n");
 288         *errp = -EINVAL;
 289         return -1;
 290 }
 291
 292 /* Process one packet of messages. */
 293 static inline int nfnetlink_rcv_skb(struct sk_buff *skb)
 294 {
 295         int err;
 296         struct nlmsghdr *nlh;
 297
 298         while (skb->len >= NLMSG_SPACE(0)) {
 299                 u32 rlen;
 300
 301                 nlh = (struct nlmsghdr *)skb->data;
 302                 if (nlh->nlmsg_len < sizeof(struct nlmsghdr)
 303                     || skb->len < nlh->nlmsg_len)
 304                         return 0;
 305                 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
 306                 if (rlen > skb->len)
 307                         rlen = skb->len;
 308                 if (nfnetlink_rcv_msg(skb, nlh, &err)) {
 309                         if (!err)
 310                                 return -1;
 311                         netlink_ack(skb, nlh, err);
 312                 } else
 313                         if (nlh->nlmsg_flags & NLM_F_ACK)
 314                                 netlink_ack(skb, nlh, 0);
 315                 skb_pull(skb, rlen);
 316         }
 317
 318         return 0;
 319 }
 320
 321 static void nfnetlink_rcv(struct sock *sk, int len)
 322 {
 323         do {
 324                 struct sk_buff *skb;
 325
 326                 if (nfnl_shlock_nowait())
 327                         return;
 328
 329                 while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
 330                         if (nfnetlink_rcv_skb(skb)) {
 331                                 if (skb->len)
 332                                         skb_queue_head(&sk->sk_receive_queue,
 333                                                        skb);
 334                                 else
 335                                         kfree_skb(skb);
 336                                 break;
 337                         }
 338                         kfree_skb(skb);
 339                 }
 340
 341                 /* don't call nfnl_shunlock, since it would reenter
 342                  * with further packet processing */
 343                 up(&nfnl_sem);
 344         } while(nfnl && nfnl->sk_receive_queue.qlen);
 345 }
 346
 347 void __exit nfnetlink_exit(void)
 348 {
 349         printk("Removing netfilter NETLINK layer.\n");
 350         sock_release(nfnl->sk_socket);
 351         return;
 352 }
 353
 354 int __init nfnetlink_init(void)
 355 {
 356         printk("Netfilter messages via NETLINK v%s.\n", nfversion);
 357
 358         nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX,
 359                                      nfnetlink_rcv, THIS_MODULE);
 360         if (!nfnl) {
 361                 printk(KERN_ERR "cannot initialize nfnetlink!\n");
 362                 return -1;
 363         }
 364
 365         return 0;
 366 }
 367
 368 module_init(nfnetlink_init);
 369 module_exit(nfnetlink_exit);
 370
 371 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
 372 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
 373 EXPORT_SYMBOL_GPL(nfnetlink_send);
 374 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 375 EXPORT_SYMBOL_GPL(nfattr_parse);
 376 EXPORT_SYMBOL_GPL(__nfa_fill);