279 lines
6.6 KiB
C
279 lines
6.6 KiB
C
/* Netfilter messages via netlink socket. Allows for user space
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* protocol helpers and general trouble making from userspace.
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*
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* (C) 2001 by Jay Schulist <jschlst@samba.org>,
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* (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
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* (C) 2005,2007 by Pablo Neira Ayuso <pablo@netfilter.org>
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*
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* Initial netfilter messages via netlink development funded and
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* generally made possible by Network Robots, Inc. (www.networkrobots.com)
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*
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* Further development of this code funded by Astaro AG (http://www.astaro.com)
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*
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* This software may be used and distributed according to the terms
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* of the GNU General Public License, incorporated herein by reference.
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/socket.h>
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#include <linux/kernel.h>
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#include <linux/major.h>
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#include <linux/timer.h>
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#include <linux/string.h>
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#include <linux/sockios.h>
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#include <linux/net.h>
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#include <linux/fcntl.h>
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#include <linux/skbuff.h>
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#include <asm/uaccess.h>
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#include <asm/system.h>
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#include <net/sock.h>
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#include <net/netlink.h>
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#include <linux/init.h>
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#include <linux/netlink.h>
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#include <linux/netfilter/nfnetlink.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
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MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
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static char __initdata nfversion[] = "0.30";
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static struct sock *nfnl = NULL;
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static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
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static DEFINE_MUTEX(nfnl_mutex);
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static void nfnl_lock(void)
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{
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mutex_lock(&nfnl_mutex);
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}
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static int nfnl_trylock(void)
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{
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return !mutex_trylock(&nfnl_mutex);
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}
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static void __nfnl_unlock(void)
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{
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mutex_unlock(&nfnl_mutex);
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}
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static void nfnl_unlock(void)
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{
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mutex_unlock(&nfnl_mutex);
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if (nfnl->sk_receive_queue.qlen)
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nfnl->sk_data_ready(nfnl, 0);
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}
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int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
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{
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nfnl_lock();
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if (subsys_table[n->subsys_id]) {
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nfnl_unlock();
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return -EBUSY;
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}
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subsys_table[n->subsys_id] = n;
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nfnl_unlock();
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return 0;
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}
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EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
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int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
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{
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nfnl_lock();
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subsys_table[n->subsys_id] = NULL;
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nfnl_unlock();
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return 0;
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}
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EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
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static inline struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
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{
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u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
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if (subsys_id >= NFNL_SUBSYS_COUNT)
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return NULL;
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return subsys_table[subsys_id];
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}
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static inline struct nfnl_callback *
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nfnetlink_find_client(u_int16_t type, struct nfnetlink_subsystem *ss)
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{
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u_int8_t cb_id = NFNL_MSG_TYPE(type);
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if (cb_id >= ss->cb_count)
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return NULL;
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return &ss->cb[cb_id];
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}
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void __nfa_fill(struct sk_buff *skb, int attrtype, int attrlen,
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const void *data)
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{
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struct nfattr *nfa;
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int size = NFA_LENGTH(attrlen);
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nfa = (struct nfattr *)skb_put(skb, NFA_ALIGN(size));
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nfa->nfa_type = attrtype;
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nfa->nfa_len = size;
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memcpy(NFA_DATA(nfa), data, attrlen);
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memset(NFA_DATA(nfa) + attrlen, 0, NFA_ALIGN(size) - size);
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}
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EXPORT_SYMBOL_GPL(__nfa_fill);
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void nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
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{
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memset(tb, 0, sizeof(struct nfattr *) * maxattr);
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while (NFA_OK(nfa, len)) {
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unsigned flavor = NFA_TYPE(nfa);
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if (flavor && flavor <= maxattr)
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tb[flavor-1] = nfa;
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nfa = NFA_NEXT(nfa, len);
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}
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}
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EXPORT_SYMBOL_GPL(nfattr_parse);
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/**
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* nfnetlink_check_attributes - check and parse nfnetlink attributes
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*
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* subsys: nfnl subsystem for which this message is to be parsed
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* nlmsghdr: netlink message to be checked/parsed
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* cda: array of pointers, needs to be at least subsys->attr_count big
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*
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*/
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static int
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nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
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struct nlmsghdr *nlh, struct nfattr *cda[])
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{
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int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
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u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
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u_int16_t attr_count = subsys->cb[cb_id].attr_count;
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/* check attribute lengths. */
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if (likely(nlh->nlmsg_len > min_len)) {
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struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
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int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
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nfattr_parse(cda, attr_count, attr, attrlen);
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}
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/* implicit: if nlmsg_len == min_len, we return 0, and an empty
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* (zeroed) cda[] array. The message is valid, but empty. */
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return 0;
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}
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int nfnetlink_has_listeners(unsigned int group)
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{
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return netlink_has_listeners(nfnl, group);
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}
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EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
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int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
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{
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int err = 0;
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NETLINK_CB(skb).dst_group = group;
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if (echo)
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atomic_inc(&skb->users);
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netlink_broadcast(nfnl, skb, pid, group, gfp_any());
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if (echo)
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err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
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return err;
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}
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EXPORT_SYMBOL_GPL(nfnetlink_send);
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int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
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{
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return netlink_unicast(nfnl, skb, pid, flags);
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}
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EXPORT_SYMBOL_GPL(nfnetlink_unicast);
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/* Process one complete nfnetlink message. */
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static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
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{
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struct nfnl_callback *nc;
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struct nfnetlink_subsystem *ss;
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int type, err;
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if (security_netlink_recv(skb, CAP_NET_ADMIN))
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return -EPERM;
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/* All the messages must at least contain nfgenmsg */
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if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg)))
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return 0;
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type = nlh->nlmsg_type;
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ss = nfnetlink_get_subsys(type);
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if (!ss) {
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#ifdef CONFIG_KMOD
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/* don't call nfnl_unlock, since it would reenter
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* with further packet processing */
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__nfnl_unlock();
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request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
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nfnl_lock();
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ss = nfnetlink_get_subsys(type);
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if (!ss)
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#endif
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return -EINVAL;
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}
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nc = nfnetlink_find_client(type, ss);
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if (!nc)
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return -EINVAL;
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{
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u_int16_t attr_count =
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ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count;
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struct nfattr *cda[attr_count];
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memset(cda, 0, sizeof(struct nfattr *) * attr_count);
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err = nfnetlink_check_attributes(ss, nlh, cda);
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if (err < 0)
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return err;
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return nc->call(nfnl, skb, nlh, cda);
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}
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}
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static void nfnetlink_rcv(struct sock *sk, int len)
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{
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unsigned int qlen = 0;
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do {
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if (nfnl_trylock())
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return;
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netlink_run_queue(sk, &qlen, nfnetlink_rcv_msg);
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__nfnl_unlock();
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} while (qlen);
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}
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static void __exit nfnetlink_exit(void)
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{
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printk("Removing netfilter NETLINK layer.\n");
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sock_release(nfnl->sk_socket);
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return;
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}
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static int __init nfnetlink_init(void)
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{
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printk("Netfilter messages via NETLINK v%s.\n", nfversion);
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nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX,
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nfnetlink_rcv, NULL, THIS_MODULE);
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if (!nfnl) {
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printk(KERN_ERR "cannot initialize nfnetlink!\n");
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return -1;
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}
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return 0;
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}
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module_init(nfnetlink_init);
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module_exit(nfnetlink_exit);
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