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
  42 static char __initdata nfversion[] = "0.30";
  43
  44 #if 0
  45 #define DEBUGP printk
  46 #else
  47 #define DEBUGP(format, args...)
  48 #endif
  49
  50 static struct sock *nfnl = NULL;
  51 static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
  52 DECLARE_MUTEX(nfnl_sem);
  53
  54 void nfnl_lock(void)
  55 {
  56         nfnl_shlock();
  57 }
  58
  59 void nfnl_unlock(void)
  60 {
  61         nfnl_shunlock();
  62 }
  63
  64 int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
  65 {
  66         DEBUGP("registering subsystem ID %u\n", n->subsys_id);
  67
  68         /* If the netlink socket wasn't created, then fail */
  69         if (!nfnl)
  70                 return -1;
  71
  72         nfnl_lock();
  73         subsys_table[n->subsys_id] = n;
  74         nfnl_unlock();
  75
  76         return 0;
  77 }
  78
  79 int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
  80 {
  81         DEBUGP("unregistering subsystem ID %u\n", n->subsys_id);
  82
  83         nfnl_lock();
  84         subsys_table[n->subsys_id] = NULL;
  85         nfnl_unlock();
  86
  87         return 0;
  88 }
  89
  90 static inline struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  91 {
  92         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
  93
  94         if (subsys_id >= NFNL_SUBSYS_COUNT
  95             || subsys_table[subsys_id] == NULL)
  96                 return NULL;
  97
  98         return subsys_table[subsys_id];
  99 }
 100
 101 static inline struct nfnl_callback *
 102 nfnetlink_find_client(u_int16_t type, struct nfnetlink_subsystem *ss)
 103 {
 104         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 105
 106         if (cb_id >= ss->cb_count) {
 107                 DEBUGP("msgtype %u >= %u, returning\n", type, ss->cb_count);
 108                 return NULL;
 109         }
 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 int 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->nfa_type;
 133                 if (flavor && flavor <= maxattr)
 134                         tb[flavor-1] = nfa;
 135                 nfa = NFA_NEXT(nfa, len);
 136         }
 137
 138         return 0;
 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
 155         memset(cda, 0, sizeof(struct nfattr *) * subsys->attr_count);
 156
 157         /* check attribute lengths. */
 158         min_len = NLMSG_ALIGN(sizeof(struct nfgenmsg));
 159         if (nlh->nlmsg_len < min_len)
 160                 return -EINVAL;
 161
 162         if (nlh->nlmsg_len > min_len) {
 163                 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
 164                 int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 165
 166                 while (NFA_OK(attr, attrlen)) {
 167                         unsigned flavor = attr->nfa_type;
 168                         if (flavor) {
 169                                 if (flavor > subsys->attr_count)
 170                                         return -EINVAL;
 171                                 cda[flavor - 1] = attr;
 172                         }
 173                         attr = NFA_NEXT(attr, attrlen);
 174                 }
 175         } else
 176                 return -EINVAL;
 177
 178         return 0;
 179 }
 180
 181 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 182 {
 183         int allocation = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
 184         int err = 0;
 185
 186         NETLINK_CB(skb).dst_groups = group;
 187         if (echo)
 188                 atomic_inc(&skb->users);
 189         netlink_broadcast(nfnl, skb, pid, group, allocation);
 190         if (echo)
 191                 err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
 192
 193         return err;
 194 }
 195
 196 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
 197 {
 198         return netlink_unicast(nfnl, skb, pid, flags);
 199 }
 200
 201 /* Process one complete nfnetlink message. */
 202 static inline int nfnetlink_rcv_msg(struct sk_buff *skb,
 203                                     struct nlmsghdr *nlh, int *errp)
 204 {
 205         struct nfnl_callback *nc;
 206         struct nfnetlink_subsystem *ss;
 207         int type, err = 0;
 208
 209         DEBUGP("entered; subsys=%u, msgtype=%u\n",
 210                  NFNL_SUBSYS_ID(nlh->nlmsg_type),
 211                  NFNL_MSG_TYPE(nlh->nlmsg_type));
 212
 213         /* Only requests are handled by kernel now. */
 214         if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
 215                 DEBUGP("received non-request message\n");
 216                 return 0;
 217         }
 218
 219         /* All the messages must at least contain nfgenmsg */
 220         if (nlh->nlmsg_len <
 221                         NLMSG_LENGTH(NLMSG_ALIGN(sizeof(struct nfgenmsg)))) {
 222                 DEBUGP("received message was too short\n");
 223                 return 0;
 224         }
 225
 226         type = nlh->nlmsg_type;
 227         ss = nfnetlink_get_subsys(type);
 228         if (!ss)
 229                 goto err_inval;
 230
 231         nc = nfnetlink_find_client(type, ss);
 232         if (!nc) {
 233                 DEBUGP("unable to find client for type %d\n", type);
 234                 goto err_inval;
 235         }
 236
 237         if (nc->cap_required &&
 238             !cap_raised(NETLINK_CB(skb).eff_cap, nc->cap_required)) {
 239                 DEBUGP("permission denied for type %d\n", type);
 240                 *errp = -EPERM;
 241                 return -1;
 242         }
 243
 244         {
 245                 struct nfattr *cda[ss->attr_count];
 246
 247                 memset(cda, 0, ss->attr_count*sizeof(struct nfattr *));
 248
 249                 err = nfnetlink_check_attributes(ss, nlh, cda);
 250                 if (err < 0)
 251                         goto err_inval;
 252
 253                 err = nc->call(nfnl, skb, nlh, cda, errp);
 254                 *errp = err;
 255                 return err;
 256         }
 257
 258 err_inval:
 259         *errp = -EINVAL;
 260         return -1;
 261 }
 262
 263 /* Process one packet of messages. */
 264 static inline int nfnetlink_rcv_skb(struct sk_buff *skb)
 265 {
 266         int err;
 267         struct nlmsghdr *nlh;
 268
 269         while (skb->len >= NLMSG_SPACE(0)) {
 270                 u32 rlen;
 271
 272                 nlh = (struct nlmsghdr *)skb->data;
 273                 if (nlh->nlmsg_len < sizeof(struct nlmsghdr)
 274                     || skb->len < nlh->nlmsg_len)
 275                         return 0;
 276                 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
 277                 if (rlen > skb->len)
 278                         rlen = skb->len;
 279                 if (nfnetlink_rcv_msg(skb, nlh, &err)) {
 280                         if (!err)
 281                                 return -1;
 282                         netlink_ack(skb, nlh, err);
 283                 } else
 284                         if (nlh->nlmsg_flags & NLM_F_ACK)
 285                                 netlink_ack(skb, nlh, 0);
 286                 skb_pull(skb, rlen);
 287         }
 288
 289         return 0;
 290 }
 291
 292 static void nfnetlink_rcv(struct sock *sk, int len)
 293 {
 294         do {
 295                 struct sk_buff *skb;
 296
 297                 if (nfnl_shlock_nowait())
 298                         return;
 299
 300                 while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
 301                         if (nfnetlink_rcv_skb(skb)) {
 302                                 if (skb->len)
 303                                         skb_queue_head(&sk->sk_receive_queue,
 304                                                        skb);
 305                                 else
 306                                         kfree_skb(skb);
 307                                 break;
 308                         }
 309                         kfree_skb(skb);
 310                 }
 311
 312                 up(&nfnl_sem);
 313         } while(nfnl && nfnl->sk_receive_queue.qlen);
 314 }
 315
 316 void __exit nfnetlink_exit(void)
 317 {
 318         printk("Removing netfilter NETLINK layer.\n");
 319         sock_release(nfnl->sk_socket);
 320         return;
 321 }
 322
 323 int __init nfnetlink_init(void)
 324 {
 325         printk("Netfilter messages via NETLINK v%s.\n", nfversion);
 326
 327         nfnl = netlink_kernel_create(NETLINK_NETFILTER, nfnetlink_rcv);
 328         if (!nfnl) {
 329                 printk(KERN_ERR "cannot initialize nfnetlink!\n");
 330                 return -1;
 331         }
 332
 333         return 0;
 334 }
 335
 336 module_init(nfnetlink_init);
 337 module_exit(nfnetlink_exit);
 338
 339 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
 340 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
 341 EXPORT_SYMBOL_GPL(nfnetlink_send);
 342 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 343 EXPORT_SYMBOL_GPL(nfattr_parse);
 344 EXPORT_SYMBOL_GPL(__nfa_fill);