net/netfilter/nfnetlink.c - linux - Git at Google

 /* Netfilter messages via netlink socket. Allows for user space
  * protocol helpers and general trouble making from userspace.
  *
  * (C) 2001 by Jay Schulist <jschlst@samba.org>,
  * (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
  * (C) 2005,2007 by Pablo Neira Ayuso <pablo@netfilter.org>
  *
  * Initial netfilter messages via netlink development funded and
  * generally made possible by Network Robots, Inc. (www.networkrobots.com)
  *
  * Further development of this code funded by Astaro AG (http://www.astaro.com)
  *
  * This software may be used and distributed according to the terms
  * of the GNU General Public License, incorporated herein by reference.
  */

 #include <linux/module.h>
 #include <linux/types.h>
 #include <linux/socket.h>
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <linux/sockios.h>
 #include <linux/net.h>
 #include <linux/skbuff.h>
 #include <asm/uaccess.h>
 #include <net/sock.h>
 #include <linux/init.h>

 #include <net/netlink.h>
 #include <linux/netfilter/nfnetlink.h>

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);

 static char __initdata nfversion[] = "0.30";

 static struct {
 	struct mutex				mutex;
 	const struct nfnetlink_subsystem __rcu	*subsys;
 } table[NFNL_SUBSYS_COUNT];

 static const int nfnl_group2type[NFNLGRP_MAX+1] = {
 	[NFNLGRP_CONNTRACK_NEW]		= NFNL_SUBSYS_CTNETLINK,
 	[NFNLGRP_CONNTRACK_UPDATE]	= NFNL_SUBSYS_CTNETLINK,
 	[NFNLGRP_CONNTRACK_DESTROY]	= NFNL_SUBSYS_CTNETLINK,
 	[NFNLGRP_CONNTRACK_EXP_NEW]	= NFNL_SUBSYS_CTNETLINK_EXP,
 	[NFNLGRP_CONNTRACK_EXP_UPDATE]	= NFNL_SUBSYS_CTNETLINK_EXP,
 	[NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
 };

 void nfnl_lock(__u8 subsys_id)
 {
 	mutex_lock(&table[subsys_id].mutex);
 }
 EXPORT_SYMBOL_GPL(nfnl_lock);

 void nfnl_unlock(__u8 subsys_id)
 {
 	mutex_unlock(&table[subsys_id].mutex);
 }
 EXPORT_SYMBOL_GPL(nfnl_unlock);

 #ifdef CONFIG_PROVE_LOCKING
 int lockdep_nfnl_is_held(u8 subsys_id)
 {
 	return lockdep_is_held(&table[subsys_id].mutex);
 }
 EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held);
 #endif

 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
 {
 	nfnl_lock(n->subsys_id);
 	if (table[n->subsys_id].subsys) {
 		nfnl_unlock(n->subsys_id);
 		return -EBUSY;
 	}
 	rcu_assign_pointer(table[n->subsys_id].subsys, n);
 	nfnl_unlock(n->subsys_id);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);

 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
 {
 	nfnl_lock(n->subsys_id);
 	table[n->subsys_id].subsys = NULL;
 	nfnl_unlock(n->subsys_id);
 	synchronize_rcu();
 	return 0;
 }
 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);

 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
 {
 	u_int8_t subsys_id = NFNL_SUBSYS_ID(type);

 	if (subsys_id >= NFNL_SUBSYS_COUNT)
 		return NULL;

 	return rcu_dereference(table[subsys_id].subsys);
 }

 static inline const struct nfnl_callback *
 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
 {
 	u_int8_t cb_id = NFNL_MSG_TYPE(type);

 	if (cb_id >= ss->cb_count)
 		return NULL;

 	return &ss->cb[cb_id];
 }

 int nfnetlink_has_listeners(struct net *net, unsigned int group)
 {
 	return netlink_has_listeners(net->nfnl, group);
 }
 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);

 struct sk_buff *nfnetlink_alloc_skb(struct net *net, unsigned int size,
 				    u32 dst_portid, gfp_t gfp_mask)
 {
 	return netlink_alloc_skb(net->nfnl, size, dst_portid, gfp_mask);
 }
 EXPORT_SYMBOL_GPL(nfnetlink_alloc_skb);

 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
 		   unsigned int group, int echo, gfp_t flags)
 {
 	return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
 }
 EXPORT_SYMBOL_GPL(nfnetlink_send);

 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
 {
 	return netlink_set_err(net->nfnl, portid, group, error);
 }
 EXPORT_SYMBOL_GPL(nfnetlink_set_err);

 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
 		      int flags)
 {
 	return netlink_unicast(net->nfnl, skb, portid, flags);
 }
 EXPORT_SYMBOL_GPL(nfnetlink_unicast);

 /* Process one complete nfnetlink message. */
 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
 	struct net *net = sock_net(skb->sk);
 	const struct nfnl_callback *nc;
 	const struct nfnetlink_subsystem *ss;
 	int type, err;

 	/* All the messages must at least contain nfgenmsg */
 	if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
 		return 0;

 	type = nlh->nlmsg_type;
 replay:
 	rcu_read_lock();
 	ss = nfnetlink_get_subsys(type);
 	if (!ss) {
 #ifdef CONFIG_MODULES
 		rcu_read_unlock();
 		request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 		rcu_read_lock();
 		ss = nfnetlink_get_subsys(type);
 		if (!ss)
 #endif
 		{
 			rcu_read_unlock();
 			return -EINVAL;
 		}
 	}

 	nc = nfnetlink_find_client(type, ss);
 	if (!nc) {
 		rcu_read_unlock();
 		return -EINVAL;
 	}

 	{
 		int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 		u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 		struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 		struct nlattr *attr = (void *)nlh + min_len;
 		int attrlen = nlh->nlmsg_len - min_len;
 		__u8 subsys_id = NFNL_SUBSYS_ID(type);

 		err = nla_parse(cda, ss->cb[cb_id].attr_count,
 				attr, attrlen, ss->cb[cb_id].policy);
 		if (err < 0) {
 			rcu_read_unlock();
 			return err;
 		}

 		if (nc->call_rcu) {
 			err = nc->call_rcu(net->nfnl, skb, nlh,
 					   (const struct nlattr **)cda);
 			rcu_read_unlock();
 		} else {
 			rcu_read_unlock();
 			nfnl_lock(subsys_id);
 			if (rcu_dereference_protected(table[subsys_id].subsys,
 				lockdep_is_held(&table[subsys_id].mutex)) != ss ||
 			    nfnetlink_find_client(type, ss) != nc)
 				err = -EAGAIN;
 			else if (nc->call)
 				err = nc->call(net->nfnl, skb, nlh,
 						   (const struct nlattr **)cda);
 			else
 				err = -EINVAL;
 			nfnl_unlock(subsys_id);
 		}
 		if (err == -EAGAIN)
 			goto replay;
 		return err;
 	}
 }

 struct nfnl_err {
 	struct list_head	head;
 	struct nlmsghdr		*nlh;
 	int			err;
 };

 static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err)
 {
 	struct nfnl_err *nfnl_err;

 	nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL);
 	if (nfnl_err == NULL)
 		return -ENOMEM;

 	nfnl_err->nlh = nlh;
 	nfnl_err->err = err;
 	list_add_tail(&nfnl_err->head, list);

 	return 0;
 }

 static void nfnl_err_del(struct nfnl_err *nfnl_err)
 {
 	list_del(&nfnl_err->head);
 	kfree(nfnl_err);
 }

 static void nfnl_err_reset(struct list_head *err_list)
 {
 	struct nfnl_err *nfnl_err, *next;

 	list_for_each_entry_safe(nfnl_err, next, err_list, head)
 		nfnl_err_del(nfnl_err);
 }

 static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
 {
 	struct nfnl_err *nfnl_err, *next;

 	list_for_each_entry_safe(nfnl_err, next, err_list, head) {
 		netlink_ack(skb, nfnl_err->nlh, nfnl_err->err);
 		nfnl_err_del(nfnl_err);
 	}
 }

 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
 				u_int16_t subsys_id)
 {
 	struct sk_buff *nskb, *oskb = skb;
 	struct net *net = sock_net(skb->sk);
 	const struct nfnetlink_subsystem *ss;
 	const struct nfnl_callback *nc;
 	bool success = true, done = false;
 	static LIST_HEAD(err_list);
 	int err;

 	if (subsys_id >= NFNL_SUBSYS_COUNT)
 		return netlink_ack(skb, nlh, -EINVAL);
 replay:
 	nskb = netlink_skb_clone(oskb, GFP_KERNEL);
 	if (!nskb)
 		return netlink_ack(oskb, nlh, -ENOMEM);

 	nskb->sk = oskb->sk;
 	skb = nskb;

 	nfnl_lock(subsys_id);
 	ss = rcu_dereference_protected(table[subsys_id].subsys,
 				       lockdep_is_held(&table[subsys_id].mutex));
 	if (!ss) {
 #ifdef CONFIG_MODULES
 		nfnl_unlock(subsys_id);
 		request_module("nfnetlink-subsys-%d", subsys_id);
 		nfnl_lock(subsys_id);
 		ss = rcu_dereference_protected(table[subsys_id].subsys,
 					       lockdep_is_held(&table[subsys_id].mutex));
 		if (!ss)
 #endif
 		{
 			nfnl_unlock(subsys_id);
 			netlink_ack(skb, nlh, -EOPNOTSUPP);
 			return kfree_skb(nskb);
 		}
 	}

 	if (!ss->commit || !ss->abort) {
 		nfnl_unlock(subsys_id);
 		netlink_ack(skb, nlh, -EOPNOTSUPP);
 		return kfree_skb(skb);
 	}

 	while (skb->len >= nlmsg_total_size(0)) {
 		int msglen, type;

 		nlh = nlmsg_hdr(skb);
 		err = 0;

 		if (nlh->nlmsg_len < NLMSG_HDRLEN) {
 			err = -EINVAL;
 			goto ack;
 		}

 		/* Only requests are handled by the kernel */
 		if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
 			err = -EINVAL;
 			goto ack;
 		}

 		type = nlh->nlmsg_type;
 		if (type == NFNL_MSG_BATCH_BEGIN) {
 			/* Malformed: Batch begin twice */
 			nfnl_err_reset(&err_list);
 			success = false;
 			goto done;
 		} else if (type == NFNL_MSG_BATCH_END) {
 			done = true;
 			goto done;
 		} else if (type < NLMSG_MIN_TYPE) {
 			err = -EINVAL;
 			goto ack;
 		}

 		/* We only accept a batch with messages for the same
 		 * subsystem.
 		 */
 		if (NFNL_SUBSYS_ID(type) != subsys_id) {
 			err = -EINVAL;
 			goto ack;
 		}

 		nc = nfnetlink_find_client(type, ss);
 		if (!nc) {
 			err = -EINVAL;
 			goto ack;
 		}

 		{
 			int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 			u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 			struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 			struct nlattr *attr = (void *)nlh + min_len;
 			int attrlen = nlh->nlmsg_len - min_len;

 			err = nla_parse(cda, ss->cb[cb_id].attr_count,
 					attr, attrlen, ss->cb[cb_id].policy);
 			if (err < 0)
 				goto ack;

 			if (nc->call_batch) {
 				err = nc->call_batch(net->nfnl, skb, nlh,
 						     (const struct nlattr **)cda);
 			}

 			/* The lock was released to autoload some module, we
 			 * have to abort and start from scratch using the
 			 * original skb.
 			 */
 			if (err == -EAGAIN) {
 				nfnl_err_reset(&err_list);
 				ss->abort(oskb);
 				nfnl_unlock(subsys_id);
 				kfree_skb(nskb);
 				goto replay;
 			}
 		}
 ack:
 		if (nlh->nlmsg_flags & NLM_F_ACK || err) {
 			/* Errors are delivered once the full batch has been
 			 * processed, this avoids that the same error is
 			 * reported several times when replaying the batch.
 			 */
 			if (nfnl_err_add(&err_list, nlh, err) < 0) {
 				/* We failed to enqueue an error, reset the
 				 * list of errors and send OOM to userspace
 				 * pointing to the batch header.
 				 */
 				nfnl_err_reset(&err_list);
 				netlink_ack(skb, nlmsg_hdr(oskb), -ENOMEM);
 				success = false;
 				goto done;
 			}
 			/* We don't stop processing the batch on errors, thus,
 			 * userspace gets all the errors that the batch
 			 * triggers.
 			 */
 			if (err)
 				success = false;
 		}

 		msglen = NLMSG_ALIGN(nlh->nlmsg_len);
 		if (msglen > skb->len)
 			msglen = skb->len;
 		skb_pull(skb, msglen);
 	}
 done:
 	if (success && done)
 		ss->commit(oskb);
 	else
 		ss->abort(oskb);

 	nfnl_err_deliver(&err_list, oskb);
 	nfnl_unlock(subsys_id);
 	kfree_skb(nskb);
 }

 static void nfnetlink_rcv(struct sk_buff *skb)
 {
 	struct nlmsghdr *nlh = nlmsg_hdr(skb);
 	int msglen;

 	if (nlh->nlmsg_len < NLMSG_HDRLEN ||
 	    skb->len < nlh->nlmsg_len)
 		return;

 	if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
 		netlink_ack(skb, nlh, -EPERM);
 		return;
 	}

 	if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN) {
 		struct nfgenmsg *nfgenmsg;

 		msglen = NLMSG_ALIGN(nlh->nlmsg_len);
 		if (msglen > skb->len)
 			msglen = skb->len;

 		if (nlh->nlmsg_len < NLMSG_HDRLEN ||
 		    skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
 			return;

 		nfgenmsg = nlmsg_data(nlh);
 		skb_pull(skb, msglen);
 		nfnetlink_rcv_batch(skb, nlh, nfgenmsg->res_id);
 	} else {
 		netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 	}
 }

 #ifdef CONFIG_MODULES
 static int nfnetlink_bind(int group)
 {
 	const struct nfnetlink_subsystem *ss;
 	int type = nfnl_group2type[group];

 	rcu_read_lock();
 	ss = nfnetlink_get_subsys(type);
 	rcu_read_unlock();
 	if (!ss)
 		request_module("nfnetlink-subsys-%d", type);
 	return 0;
 }
 #endif

 static int __net_init nfnetlink_net_init(struct net *net)
 {
 	struct sock *nfnl;
 	struct netlink_kernel_cfg cfg = {
 		.groups	= NFNLGRP_MAX,
 		.input	= nfnetlink_rcv,
 #ifdef CONFIG_MODULES
 		.bind	= nfnetlink_bind,
 #endif
 	};

 	nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
 	if (!nfnl)
 		return -ENOMEM;
 	net->nfnl_stash = nfnl;
 	rcu_assign_pointer(net->nfnl, nfnl);
 	return 0;
 }

 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 {
 	struct net *net;

 	list_for_each_entry(net, net_exit_list, exit_list)
 		RCU_INIT_POINTER(net->nfnl, NULL);
 	synchronize_net();
 	list_for_each_entry(net, net_exit_list, exit_list)
 		netlink_kernel_release(net->nfnl_stash);
 }

 static struct pernet_operations nfnetlink_net_ops = {
 	.init		= nfnetlink_net_init,
 	.exit_batch	= nfnetlink_net_exit_batch,
 };

 static int __init nfnetlink_init(void)
 {
 	int i;

 	for (i=0; i<NFNL_SUBSYS_COUNT; i++)
 		mutex_init(&table[i].mutex);

 	pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 	return register_pernet_subsys(&nfnetlink_net_ops);
 }

 static void __exit nfnetlink_exit(void)
 {
 	pr_info("Removing netfilter NETLINK layer.\n");
 	unregister_pernet_subsys(&nfnetlink_net_ops);
 }
 module_init(nfnetlink_init);
 module_exit(nfnetlink_exit);
	/* Netfilter messages via netlink socket. Allows for user space
	* protocol helpers and general trouble making from userspace.
	*
	* (C) 2001 by Jay Schulist <jschlst@samba.org>,
	* (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
	* (C) 2005,2007 by Pablo Neira Ayuso <pablo@netfilter.org>
	*
	* Initial netfilter messages via netlink development funded and
	* generally made possible by Network Robots, Inc. (www.networkrobots.com)
	*
	* Further development of this code funded by Astaro AG (http://www.astaro.com)
	*
	* This software may be used and distributed according to the terms
	* of the GNU General Public License, incorporated herein by reference.
	*/

	#include <linux/module.h>
	#include <linux/types.h>
	#include <linux/socket.h>
	#include <linux/kernel.h>
	#include <linux/string.h>
	#include <linux/sockios.h>
	#include <linux/net.h>
	#include <linux/skbuff.h>
	#include <asm/uaccess.h>
	#include <net/sock.h>
	#include <linux/init.h>

	#include <net/netlink.h>
	#include <linux/netfilter/nfnetlink.h>

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
	MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);

	static char __initdata nfversion[] = "0.30";

	static struct {
	struct mutex mutex;
	const struct nfnetlink_subsystem __rcu *subsys;
	} table[NFNL_SUBSYS_COUNT];

	static const int nfnl_group2type[NFNLGRP_MAX+1] = {
	[NFNLGRP_CONNTRACK_NEW] = NFNL_SUBSYS_CTNETLINK,
	[NFNLGRP_CONNTRACK_UPDATE] = NFNL_SUBSYS_CTNETLINK,
	[NFNLGRP_CONNTRACK_DESTROY] = NFNL_SUBSYS_CTNETLINK,
	[NFNLGRP_CONNTRACK_EXP_NEW] = NFNL_SUBSYS_CTNETLINK_EXP,
	[NFNLGRP_CONNTRACK_EXP_UPDATE] = NFNL_SUBSYS_CTNETLINK_EXP,
	[NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
	};

	void nfnl_lock(__u8 subsys_id)
	{
	mutex_lock(&table[subsys_id].mutex);
	}
	EXPORT_SYMBOL_GPL(nfnl_lock);

	void nfnl_unlock(__u8 subsys_id)
	{
	mutex_unlock(&table[subsys_id].mutex);
	}
	EXPORT_SYMBOL_GPL(nfnl_unlock);

	#ifdef CONFIG_PROVE_LOCKING
	int lockdep_nfnl_is_held(u8 subsys_id)
	{
	return lockdep_is_held(&table[subsys_id].mutex);
	}
	EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held);
	#endif

	int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
	{
	nfnl_lock(n->subsys_id);
	if (table[n->subsys_id].subsys) {
	nfnl_unlock(n->subsys_id);
	return -EBUSY;
	}
	rcu_assign_pointer(table[n->subsys_id].subsys, n);
	nfnl_unlock(n->subsys_id);

	return 0;
	}
	EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);

	int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
	{
	nfnl_lock(n->subsys_id);
	table[n->subsys_id].subsys = NULL;
	nfnl_unlock(n->subsys_id);
	synchronize_rcu();
	return 0;
	}
	EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);

	static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
	{
	u_int8_t subsys_id = NFNL_SUBSYS_ID(type);

	if (subsys_id >= NFNL_SUBSYS_COUNT)
	return NULL;

	return rcu_dereference(table[subsys_id].subsys);
	}

	static inline const struct nfnl_callback *
	nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
	{
	u_int8_t cb_id = NFNL_MSG_TYPE(type);

	if (cb_id >= ss->cb_count)
	return NULL;

	return &ss->cb[cb_id];
	}

	int nfnetlink_has_listeners(struct net *net, unsigned int group)
	{
	return netlink_has_listeners(net->nfnl, group);
	}
	EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);

	struct sk_buff nfnetlink_alloc_skb(struct net net, unsigned int size,
	u32 dst_portid, gfp_t gfp_mask)
	{
	return netlink_alloc_skb(net->nfnl, size, dst_portid, gfp_mask);
	}
	EXPORT_SYMBOL_GPL(nfnetlink_alloc_skb);

	int nfnetlink_send(struct sk_buff skb, struct net net, u32 portid,
	unsigned int group, int echo, gfp_t flags)
	{
	return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
	}
	EXPORT_SYMBOL_GPL(nfnetlink_send);

	int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
	{
	return netlink_set_err(net->nfnl, portid, group, error);
	}
	EXPORT_SYMBOL_GPL(nfnetlink_set_err);

	int nfnetlink_unicast(struct sk_buff skb, struct net net, u32 portid,
	int flags)
	{
	return netlink_unicast(net->nfnl, skb, portid, flags);
	}
	EXPORT_SYMBOL_GPL(nfnetlink_unicast);

	/* Process one complete nfnetlink message. */
	static int nfnetlink_rcv_msg(struct sk_buff skb, struct nlmsghdr nlh)
	{
	struct net *net = sock_net(skb->sk);
	const struct nfnl_callback *nc;
	const struct nfnetlink_subsystem *ss;
	int type, err;

	/* All the messages must at least contain nfgenmsg */
	if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
	return 0;

	type = nlh->nlmsg_type;
	replay:
	rcu_read_lock();
	ss = nfnetlink_get_subsys(type);
	if (!ss) {
	#ifdef CONFIG_MODULES
	rcu_read_unlock();
	request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
	rcu_read_lock();
	ss = nfnetlink_get_subsys(type);
	if (!ss)
	#endif
	{
	rcu_read_unlock();
	return -EINVAL;
	}
	}

	nc = nfnetlink_find_client(type, ss);
	if (!nc) {
	rcu_read_unlock();
	return -EINVAL;
	}

	{
	int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
	u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
	struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
	struct nlattr attr = (void )nlh + min_len;
	int attrlen = nlh->nlmsg_len - min_len;
	__u8 subsys_id = NFNL_SUBSYS_ID(type);

	err = nla_parse(cda, ss->cb[cb_id].attr_count,
	attr, attrlen, ss->cb[cb_id].policy);
	if (err < 0) {
	rcu_read_unlock();
	return err;
	}

	if (nc->call_rcu) {
	err = nc->call_rcu(net->nfnl, skb, nlh,
	(const struct nlattr **)cda);
	rcu_read_unlock();
	} else {
	rcu_read_unlock();
	nfnl_lock(subsys_id);
	if (rcu_dereference_protected(table[subsys_id].subsys,
	lockdep_is_held(&table[subsys_id].mutex)) != ss \|\|
	nfnetlink_find_client(type, ss) != nc)
	err = -EAGAIN;
	else if (nc->call)
	err = nc->call(net->nfnl, skb, nlh,
	(const struct nlattr **)cda);
	else
	err = -EINVAL;
	nfnl_unlock(subsys_id);
	}
	if (err == -EAGAIN)
	goto replay;
	return err;
	}
	}

	struct nfnl_err {
	struct list_head head;
	struct nlmsghdr *nlh;
	int err;
	};

	static int nfnl_err_add(struct list_head list, struct nlmsghdr nlh, int err)
	{
	struct nfnl_err *nfnl_err;

	nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL);
	if (nfnl_err == NULL)
	return -ENOMEM;

	nfnl_err->nlh = nlh;
	nfnl_err->err = err;
	list_add_tail(&nfnl_err->head, list);

	return 0;
	}

	static void nfnl_err_del(struct nfnl_err *nfnl_err)
	{
	list_del(&nfnl_err->head);
	kfree(nfnl_err);
	}

	static void nfnl_err_reset(struct list_head *err_list)
	{
	struct nfnl_err nfnl_err, next;

	list_for_each_entry_safe(nfnl_err, next, err_list, head)
	nfnl_err_del(nfnl_err);
	}

	static void nfnl_err_deliver(struct list_head err_list, struct sk_buff skb)
	{
	struct nfnl_err nfnl_err, next;

	list_for_each_entry_safe(nfnl_err, next, err_list, head) {
	netlink_ack(skb, nfnl_err->nlh, nfnl_err->err);
	nfnl_err_del(nfnl_err);
	}
	}

	static void nfnetlink_rcv_batch(struct sk_buff skb, struct nlmsghdr nlh,
	u_int16_t subsys_id)
	{
	struct sk_buff nskb, oskb = skb;
	struct net *net = sock_net(skb->sk);
	const struct nfnetlink_subsystem *ss;
	const struct nfnl_callback *nc;
	bool success = true, done = false;
	static LIST_HEAD(err_list);
	int err;

	if (subsys_id >= NFNL_SUBSYS_COUNT)
	return netlink_ack(skb, nlh, -EINVAL);
	replay:
	nskb = netlink_skb_clone(oskb, GFP_KERNEL);
	if (!nskb)
	return netlink_ack(oskb, nlh, -ENOMEM);

	nskb->sk = oskb->sk;
	skb = nskb;

	nfnl_lock(subsys_id);
	ss = rcu_dereference_protected(table[subsys_id].subsys,
	lockdep_is_held(&table[subsys_id].mutex));
	if (!ss) {
	#ifdef CONFIG_MODULES
	nfnl_unlock(subsys_id);
	request_module("nfnetlink-subsys-%d", subsys_id);
	nfnl_lock(subsys_id);
	ss = rcu_dereference_protected(table[subsys_id].subsys,
	lockdep_is_held(&table[subsys_id].mutex));
	if (!ss)
	#endif
	{
	nfnl_unlock(subsys_id);
	netlink_ack(skb, nlh, -EOPNOTSUPP);
	return kfree_skb(nskb);
	}
	}

	if (!ss->commit \|\| !ss->abort) {
	nfnl_unlock(subsys_id);
	netlink_ack(skb, nlh, -EOPNOTSUPP);
	return kfree_skb(skb);
	}

	while (skb->len >= nlmsg_total_size(0)) {
	int msglen, type;

	nlh = nlmsg_hdr(skb);
	err = 0;

	if (nlh->nlmsg_len < NLMSG_HDRLEN) {
	err = -EINVAL;
	goto ack;
	}

	/* Only requests are handled by the kernel */
	if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
	err = -EINVAL;
	goto ack;
	}

	type = nlh->nlmsg_type;
	if (type == NFNL_MSG_BATCH_BEGIN) {
	/* Malformed: Batch begin twice */
	nfnl_err_reset(&err_list);
	success = false;
	goto done;
	} else if (type == NFNL_MSG_BATCH_END) {
	done = true;
	goto done;
	} else if (type < NLMSG_MIN_TYPE) {
	err = -EINVAL;
	goto ack;
	}

	/* We only accept a batch with messages for the same
	* subsystem.
	*/
	if (NFNL_SUBSYS_ID(type) != subsys_id) {
	err = -EINVAL;
	goto ack;
	}

	nc = nfnetlink_find_client(type, ss);
	if (!nc) {
	err = -EINVAL;
	goto ack;
	}

	{
	int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
	u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
	struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
	struct nlattr attr = (void )nlh + min_len;
	int attrlen = nlh->nlmsg_len - min_len;

	err = nla_parse(cda, ss->cb[cb_id].attr_count,
	attr, attrlen, ss->cb[cb_id].policy);
	if (err < 0)
	goto ack;

	if (nc->call_batch) {
	err = nc->call_batch(net->nfnl, skb, nlh,
	(const struct nlattr **)cda);
	}

	/* The lock was released to autoload some module, we
	* have to abort and start from scratch using the
	* original skb.
	*/
	if (err == -EAGAIN) {
	nfnl_err_reset(&err_list);
	ss->abort(oskb);
	nfnl_unlock(subsys_id);
	kfree_skb(nskb);
	goto replay;
	}
	}
	ack:
	if (nlh->nlmsg_flags & NLM_F_ACK \|\| err) {
	/* Errors are delivered once the full batch has been
	* processed, this avoids that the same error is
	* reported several times when replaying the batch.
	*/
	if (nfnl_err_add(&err_list, nlh, err) < 0) {
	/* We failed to enqueue an error, reset the
	* list of errors and send OOM to userspace
	* pointing to the batch header.
	*/
	nfnl_err_reset(&err_list);
	netlink_ack(skb, nlmsg_hdr(oskb), -ENOMEM);
	success = false;
	goto done;
	}
	/* We don't stop processing the batch on errors, thus,
	* userspace gets all the errors that the batch
	* triggers.
	*/
	if (err)
	success = false;
	}

	msglen = NLMSG_ALIGN(nlh->nlmsg_len);
	if (msglen > skb->len)
	msglen = skb->len;
	skb_pull(skb, msglen);
	}
	done:
	if (success && done)
	ss->commit(oskb);
	else
	ss->abort(oskb);

	nfnl_err_deliver(&err_list, oskb);
	nfnl_unlock(subsys_id);
	kfree_skb(nskb);
	}

	static void nfnetlink_rcv(struct sk_buff *skb)
	{
	struct nlmsghdr *nlh = nlmsg_hdr(skb);
	int msglen;

	if (nlh->nlmsg_len < NLMSG_HDRLEN \|\|
	skb->len < nlh->nlmsg_len)
	return;

	if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
	netlink_ack(skb, nlh, -EPERM);
	return;
	}

	if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN) {
	struct nfgenmsg *nfgenmsg;

	msglen = NLMSG_ALIGN(nlh->nlmsg_len);
	if (msglen > skb->len)
	msglen = skb->len;

	if (nlh->nlmsg_len < NLMSG_HDRLEN \|\|
	skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
	return;

	nfgenmsg = nlmsg_data(nlh);
	skb_pull(skb, msglen);
	nfnetlink_rcv_batch(skb, nlh, nfgenmsg->res_id);
	} else {
	netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
	}
	}

	#ifdef CONFIG_MODULES
	static int nfnetlink_bind(int group)
	{
	const struct nfnetlink_subsystem *ss;
	int type = nfnl_group2type[group];

	rcu_read_lock();
	ss = nfnetlink_get_subsys(type);
	rcu_read_unlock();
	if (!ss)
	request_module("nfnetlink-subsys-%d", type);
	return 0;
	}
	#endif

	static int __net_init nfnetlink_net_init(struct net *net)
	{
	struct sock *nfnl;
	struct netlink_kernel_cfg cfg = {
	.groups = NFNLGRP_MAX,
	.input = nfnetlink_rcv,
	#ifdef CONFIG_MODULES
	.bind = nfnetlink_bind,
	#endif
	};

	nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
	if (!nfnl)
	return -ENOMEM;
	net->nfnl_stash = nfnl;
	rcu_assign_pointer(net->nfnl, nfnl);
	return 0;
	}

	static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
	{
	struct net *net;

	list_for_each_entry(net, net_exit_list, exit_list)
	RCU_INIT_POINTER(net->nfnl, NULL);
	synchronize_net();
	list_for_each_entry(net, net_exit_list, exit_list)
	netlink_kernel_release(net->nfnl_stash);
	}

	static struct pernet_operations nfnetlink_net_ops = {
	.init = nfnetlink_net_init,
	.exit_batch = nfnetlink_net_exit_batch,
	};

	static int __init nfnetlink_init(void)
	{
	int i;

	for (i=0; i<NFNL_SUBSYS_COUNT; i++)
	mutex_init(&table[i].mutex);

	pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
	return register_pernet_subsys(&nfnetlink_net_ops);
	}

	static void __exit nfnetlink_exit(void)
	{
	pr_info("Removing netfilter NETLINK layer.\n");
	unregister_pernet_subsys(&nfnetlink_net_ops);
	}
	module_init(nfnetlink_init);
	module_exit(nfnetlink_exit);