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) 2005,2007 by Pablo Neira Ayuso <pablo@netfilter.org> 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 <net/netlink.h> 32 #include <linux/init.h> 33 34 #include <linux/netlink.h> 35 #include <linux/netfilter/nfnetlink.h> 36 37 MODULE_LICENSE("GPL"); 38 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 39 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER); 40 41 static char __initdata nfversion[] = "0.30"; 42 43 static struct sock *nfnl = NULL; 44 static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT]; 45 static DEFINE_MUTEX(nfnl_mutex); 46 47 static void nfnl_lock(void) 48 { 49 mutex_lock(&nfnl_mutex); 50 } 51 52 static int nfnl_trylock(void) 53 { 54 return !mutex_trylock(&nfnl_mutex); 55 } 56 57 static void __nfnl_unlock(void) 58 { 59 mutex_unlock(&nfnl_mutex); 60 } 61 62 static void nfnl_unlock(void) 63 { 64 mutex_unlock(&nfnl_mutex); 65 if (nfnl->sk_receive_queue.qlen) 66 nfnl->sk_data_ready(nfnl, 0); 67 } 68 69 int nfnetlink_subsys_register(struct nfnetlink_subsystem *n) 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 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register); 82 83 int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n) 84 { 85 nfnl_lock(); 86 subsys_table[n->subsys_id] = NULL; 87 nfnl_unlock(); 88 89 return 0; 90 } 91 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister); 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 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 return NULL; 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 EXPORT_SYMBOL_GPL(__nfa_fill); 127 128 void nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len) 129 { 130 memset(tb, 0, sizeof(struct nfattr *) * maxattr); 131 132 while (NFA_OK(nfa, len)) { 133 unsigned flavor = NFA_TYPE(nfa); 134 if (flavor && flavor <= maxattr) 135 tb[flavor-1] = nfa; 136 nfa = NFA_NEXT(nfa, len); 137 } 138 } 139 EXPORT_SYMBOL_GPL(nfattr_parse); 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 = NLMSG_SPACE(sizeof(struct nfgenmsg)); 154 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type); 155 u_int16_t attr_count = subsys->cb[cb_id].attr_count; 156 157 /* check attribute lengths. */ 158 if (likely(nlh->nlmsg_len > min_len)) { 159 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh)); 160 int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len); 161 nfattr_parse(cda, attr_count, attr, attrlen); 162 } 163 164 /* implicit: if nlmsg_len == min_len, we return 0, and an empty 165 * (zeroed) cda[] array. The message is valid, but empty. */ 166 167 return 0; 168 } 169 170 int nfnetlink_has_listeners(unsigned int group) 171 { 172 return netlink_has_listeners(nfnl, group); 173 } 174 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners); 175 176 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo) 177 { 178 int err = 0; 179 180 NETLINK_CB(skb).dst_group = group; 181 if (echo) 182 atomic_inc(&skb->users); 183 netlink_broadcast(nfnl, skb, pid, group, gfp_any()); 184 if (echo) 185 err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT); 186 187 return err; 188 } 189 EXPORT_SYMBOL_GPL(nfnetlink_send); 190 191 int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags) 192 { 193 return netlink_unicast(nfnl, skb, pid, flags); 194 } 195 EXPORT_SYMBOL_GPL(nfnetlink_unicast); 196 197 /* Process one complete nfnetlink message. */ 198 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh) 199 { 200 struct nfnl_callback *nc; 201 struct nfnetlink_subsystem *ss; 202 int type, err; 203 204 if (security_netlink_recv(skb, CAP_NET_ADMIN)) 205 return -EPERM; 206 207 /* All the messages must at least contain nfgenmsg */ 208 if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg))) 209 return 0; 210 211 type = nlh->nlmsg_type; 212 ss = nfnetlink_get_subsys(type); 213 if (!ss) { 214 #ifdef CONFIG_KMOD 215 /* don't call nfnl_unlock, since it would reenter 216 * with further packet processing */ 217 __nfnl_unlock(); 218 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type)); 219 nfnl_lock(); 220 ss = nfnetlink_get_subsys(type); 221 if (!ss) 222 #endif 223 return -EINVAL; 224 } 225 226 nc = nfnetlink_find_client(type, ss); 227 if (!nc) 228 return -EINVAL; 229 230 { 231 u_int16_t attr_count = 232 ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count; 233 struct nfattr *cda[attr_count]; 234 235 memset(cda, 0, sizeof(struct nfattr *) * attr_count); 236 237 err = nfnetlink_check_attributes(ss, nlh, cda); 238 if (err < 0) 239 return err; 240 return nc->call(nfnl, skb, nlh, cda); 241 } 242 } 243 244 static void nfnetlink_rcv(struct sock *sk, int len) 245 { 246 unsigned int qlen = 0; 247 248 do { 249 if (nfnl_trylock()) 250 return; 251 netlink_run_queue(sk, &qlen, nfnetlink_rcv_msg); 252 __nfnl_unlock(); 253 } while (qlen); 254 } 255 256 static void __exit nfnetlink_exit(void) 257 { 258 printk("Removing netfilter NETLINK layer.\n"); 259 sock_release(nfnl->sk_socket); 260 return; 261 } 262 263 static int __init nfnetlink_init(void) 264 { 265 printk("Netfilter messages via NETLINK v%s.\n", nfversion); 266 267 nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX, 268 nfnetlink_rcv, NULL, THIS_MODULE); 269 if (!nfnl) { 270 printk(KERN_ERR "cannot initialize nfnetlink!\n"); 271 return -1; 272 } 273 274 return 0; 275 } 276 277 module_init(nfnetlink_init); 278 module_exit(nfnetlink_exit); 279