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
 159         memset(cda, 0, sizeof(struct nfattr *) * subsys->attr_count);
 160
 161         /* check attribute lengths. */
 162         min_len = NLMSG_ALIGN(sizeof(struct nfgenmsg));
 163         if (nlh->nlmsg_len < min_len)
 164                 return -EINVAL;
 165
 166         if (nlh->nlmsg_len > min_len) {
 167                 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
 168                 int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 169
 170                 while (NFA_OK(attr, attrlen)) {
 171                         unsigned flavor = attr->nfa_type;
 172                         if (flavor) {
 173                                 if (flavor > subsys->attr_count)
 174                                         return -EINVAL;
 175                                 cda[flavor - 1] = attr;
 176                         }
 177                         attr = NFA_NEXT(attr, attrlen);
 178                 }
 179         } else
 180                 return -EINVAL;
 181
 182         return 0;
 183 }
 184
 185 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 186 {
 187         int allocation = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
 188         int err = 0;
 189
 190         NETLINK_CB(skb).dst_groups = group;
 191         if (echo)
 192                 atomic_inc(&skb->users);
 193         netlink_broadcast(nfnl, skb, pid, group, allocation);
 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 inline 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         DEBUGP("entered; subsys=%u, msgtype=%u\n",
 214                  NFNL_SUBSYS_ID(nlh->nlmsg_type),
 215                  NFNL_MSG_TYPE(nlh->nlmsg_type));
 216
 217         /* Only requests are handled by kernel now. */
 218         if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
 219                 DEBUGP("received non-request message\n");
 220                 return 0;
 221         }
 222
 223         /* All the messages must at least contain nfgenmsg */
 224         if (nlh->nlmsg_len <
 225                         NLMSG_LENGTH(NLMSG_ALIGN(sizeof(struct nfgenmsg)))) {
 226                 DEBUGP("received message was too short\n");
 227                 return 0;
 228         }
 229
 230         type = nlh->nlmsg_type;
 231         ss = nfnetlink_get_subsys(type);
 232         if (!ss) {
 233 #ifdef CONFIG_KMOD
 234                 /* don't call nfnl_shunlock, since it would reenter
 235                  * with further packet processing */
 236                 up(&nfnl_sem);
 237                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 238                 nfnl_shlock();
 239                 ss = nfnetlink_get_subsys(type);
 240                 if (!ss)
 241 #endif
 242                 goto err_inval;
 243         }
 244
 245         nc = nfnetlink_find_client(type, ss);
 246         if (!nc) {
 247                 DEBUGP("unable to find client for type %d\n", type);
 248                 goto err_inval;
 249         }
 250
 251         if (nc->cap_required &&
 252             !cap_raised(NETLINK_CB(skb).eff_cap, nc->cap_required)) {
 253                 DEBUGP("permission denied for type %d\n", type);
 254                 *errp = -EPERM;
 255                 return -1;
 256         }
 257
 258         {
 259                 struct nfattr *cda[ss->attr_count];
 260
 261                 memset(cda, 0, ss->attr_count*sizeof(struct nfattr *));
 262
 263                 err = nfnetlink_check_attributes(ss, nlh, cda);
 264                 if (err < 0)
 265                         goto err_inval;
 266
 267                 DEBUGP("calling handler\n");
 268                 err = nc->call(nfnl, skb, nlh, cda, errp);
 269                 *errp = err;
 270                 return err;
 271         }
 272
 273 err_inval:
 274         DEBUGP("returning -EINVAL\n");
 275         *errp = -EINVAL;
 276         return -1;
 277 }
 278
 279 /* Process one packet of messages. */
 280 static inline int nfnetlink_rcv_skb(struct sk_buff *skb)
 281 {
 282         int err;
 283         struct nlmsghdr *nlh;
 284
 285         while (skb->len >= NLMSG_SPACE(0)) {
 286                 u32 rlen;
 287
 288                 nlh = (struct nlmsghdr *)skb->data;
 289                 if (nlh->nlmsg_len < sizeof(struct nlmsghdr)
 290                     || skb->len < nlh->nlmsg_len)
 291                         return 0;
 292                 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
 293                 if (rlen > skb->len)
 294                         rlen = skb->len;
 295                 if (nfnetlink_rcv_msg(skb, nlh, &err)) {
 296                         if (!err)
 297                                 return -1;
 298                         netlink_ack(skb, nlh, err);
 299                 } else
 300                         if (nlh->nlmsg_flags & NLM_F_ACK)
 301                                 netlink_ack(skb, nlh, 0);
 302                 skb_pull(skb, rlen);
 303         }
 304
 305         return 0;
 306 }
 307
 308 static void nfnetlink_rcv(struct sock *sk, int len)
 309 {
 310         do {
 311                 struct sk_buff *skb;
 312
 313                 if (nfnl_shlock_nowait())
 314                         return;
 315
 316                 while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
 317                         if (nfnetlink_rcv_skb(skb)) {
 318                                 if (skb->len)
 319                                         skb_queue_head(&sk->sk_receive_queue,
 320                                                        skb);
 321                                 else
 322                                         kfree_skb(skb);
 323                                 break;
 324                         }
 325                         kfree_skb(skb);
 326                 }
 327
 328                 /* don't call nfnl_shunlock, since it would reenter
 329                  * with further packet processing */
 330                 up(&nfnl_sem);
 331         } while(nfnl && nfnl->sk_receive_queue.qlen);
 332 }
 333
 334 void __exit nfnetlink_exit(void)
 335 {
 336         printk("Removing netfilter NETLINK layer.\n");
 337         sock_release(nfnl->sk_socket);
 338         return;
 339 }
 340
 341 int __init nfnetlink_init(void)
 342 {
 343         printk("Netfilter messages via NETLINK v%s.\n", nfversion);
 344
 345         nfnl = netlink_kernel_create(NETLINK_NETFILTER, nfnetlink_rcv,
 346                                      THIS_MODULE);
 347         if (!nfnl) {
 348                 printk(KERN_ERR "cannot initialize nfnetlink!\n");
 349                 return -1;
 350         }
 351
 352         return 0;
 353 }
 354
 355 module_init(nfnetlink_init);
 356 module_exit(nfnetlink_exit);
 357
 358 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
 359 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
 360 EXPORT_SYMBOL_GPL(nfnetlink_send);
 361 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 362 EXPORT_SYMBOL_GPL(nfattr_parse);
 363 EXPORT_SYMBOL_GPL(__nfa_fill);