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 gfp_t allocation = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL; 201 int err = 0; 202 203 NETLINK_CB(skb).dst_group = group; 204 if (echo) 205 atomic_inc(&skb->users); 206 netlink_broadcast(nfnl, skb, pid, group, allocation); 207 if (echo) 208 err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT); 209 210 return err; 211 } 212 213 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags) 214 { 215 return netlink_unicast(nfnl, skb, pid, flags); 216 } 217 218 /* Process one complete nfnetlink message. */ 219 static int nfnetlink_rcv_msg(struct sk_buff *skb, 220 struct nlmsghdr *nlh, int *errp) 221 { 222 struct nfnl_callback *nc; 223 struct nfnetlink_subsystem *ss; 224 int type, err = 0; 225 226 DEBUGP("entered; subsys=%u, msgtype=%u\n", 227 NFNL_SUBSYS_ID(nlh->nlmsg_type), 228 NFNL_MSG_TYPE(nlh->nlmsg_type)); 229 230 if (security_netlink_recv(skb, CAP_NET_ADMIN)) { 231 DEBUGP("missing CAP_NET_ADMIN\n"); 232 *errp = -EPERM; 233 return -1; 234 } 235 236 /* Only requests are handled by kernel now. */ 237 if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) { 238 DEBUGP("received non-request message\n"); 239 return 0; 240 } 241 242 /* All the messages must at least contain nfgenmsg */ 243 if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg))) { 244 DEBUGP("received message was too short\n"); 245 return 0; 246 } 247 248 type = nlh->nlmsg_type; 249 ss = nfnetlink_get_subsys(type); 250 if (!ss) { 251 #ifdef CONFIG_KMOD 252 /* don't call nfnl_shunlock, since it would reenter 253 * with further packet processing */ 254 up(&nfnl_sem); 255 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type)); 256 nfnl_shlock(); 257 ss = nfnetlink_get_subsys(type); 258 if (!ss) 259 #endif 260 goto err_inval; 261 } 262 263 nc = nfnetlink_find_client(type, ss); 264 if (!nc) { 265 DEBUGP("unable to find client for type %d\n", type); 266 goto err_inval; 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 static void __exit nfnetlink_exit(void) 348 { 349 printk("Removing netfilter NETLINK layer.\n"); 350 sock_release(nfnl->sk_socket); 351 return; 352 } 353 354 static 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); 377