1. 根目录:
2. net
3. netfilter
4. nf_conntrack_proto.c

/* L3/L4 protocol support for nf_conntrack. */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/types.h>
#include <linux/netfilter.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/vmalloc.h>
#include <linux/stddef.h>
#include <linux/err.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/rtnetlink.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_l3proto.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_core.h>

static struct nf_conntrack_l4proto __rcu **nf_ct_protos[PF_MAX] __read_mostly;
struct nf_conntrack_l3proto __rcu *nf_ct_l3protos[AF_MAX] __read_mostly;
EXPORT_SYMBOL_GPL(nf_ct_l3protos);

static DEFINE_MUTEX(nf_ct_proto_mutex);

#ifdef CONFIG_SYSCTL
static int
nf_ct_register_sysctl(struct ctl_table_header **header, struct ctl_path *path,
		      struct ctl_table *table, unsigned int *users)
{
	if (*header == NULL) {
		*header = register_sysctl_paths(path, table);
		if (*header == NULL)
			return -ENOMEM;
	}
	if (users != NULL)
		(*users)++;
	return 0;
}

static void
nf_ct_unregister_sysctl(struct ctl_table_header **header,
			struct ctl_table *table, unsigned int *users)
{
	if (users != NULL && --*users > 0)
		return;

	unregister_sysctl_table(*header);
	*header = NULL;
}
#endif

struct nf_conntrack_l4proto *
__nf_ct_l4proto_find(u_int16_t l3proto, u_int8_t l4proto)
{
	if (unlikely(l3proto >= AF_MAX || nf_ct_protos[l3proto] == NULL))
		return &nf_conntrack_l4proto_generic;

	return rcu_dereference(nf_ct_protos[l3proto][l4proto]);
}
EXPORT_SYMBOL_GPL(__nf_ct_l4proto_find);

/* this is guaranteed to always return a valid protocol helper, since
 * it falls back to generic_protocol */
struct nf_conntrack_l3proto *
nf_ct_l3proto_find_get(u_int16_t l3proto)
{
	struct nf_conntrack_l3proto *p;

	rcu_read_lock();
	p = __nf_ct_l3proto_find(l3proto);
	if (!try_module_get(p->me))
		p = &nf_conntrack_l3proto_generic;
	rcu_read_unlock();

	return p;
}
EXPORT_SYMBOL_GPL(nf_ct_l3proto_find_get);

void nf_ct_l3proto_put(struct nf_conntrack_l3proto *p)
{
	module_put(p->me);
}
EXPORT_SYMBOL_GPL(nf_ct_l3proto_put);

int
nf_ct_l3proto_try_module_get(unsigned short l3proto)
{
	int ret;
	struct nf_conntrack_l3proto *p;

retry:	p = nf_ct_l3proto_find_get(l3proto);
	if (p == &nf_conntrack_l3proto_generic) {
		ret = request_module("nf_conntrack-%d", l3proto);
		if (!ret)
			goto retry;

		return -EPROTOTYPE;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(nf_ct_l3proto_try_module_get);

void nf_ct_l3proto_module_put(unsigned short l3proto)
{
	struct nf_conntrack_l3proto *p;

	/* rcu_read_lock not necessary since the caller holds a reference, but
	 * taken anyways to avoid lockdep warnings in __nf_ct_l3proto_find()
	 */
	rcu_read_lock();
	p = __nf_ct_l3proto_find(l3proto);
	module_put(p->me);
	rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(nf_ct_l3proto_module_put);

static int kill_l3proto(struct nf_conn *i, void *data)
{
	return nf_ct_l3num(i) == ((struct nf_conntrack_l3proto *)data)->l3proto;
}

static int kill_l4proto(struct nf_conn *i, void *data)
{
	struct nf_conntrack_l4proto *l4proto;
	l4proto = (struct nf_conntrack_l4proto *)data;
	return nf_ct_protonum(i) == l4proto->l4proto &&
	       nf_ct_l3num(i) == l4proto->l3proto;
}

static int nf_ct_l3proto_register_sysctl(struct nf_conntrack_l3proto *l3proto)
{
	int err = 0;

#ifdef CONFIG_SYSCTL
	if (l3proto->ctl_table != NULL) {
		err = nf_ct_register_sysctl(&l3proto->ctl_table_header,
					    l3proto->ctl_table_path,
					    l3proto->ctl_table, NULL);
	}
#endif
	return err;
}

static void nf_ct_l3proto_unregister_sysctl(struct nf_conntrack_l3proto *l3proto)
{
#ifdef CONFIG_SYSCTL
	if (l3proto->ctl_table_header != NULL)
		nf_ct_unregister_sysctl(&l3proto->ctl_table_header,
					l3proto->ctl_table, NULL);
#endif
}

int nf_conntrack_l3proto_register(struct nf_conntrack_l3proto *proto)
{
	int ret = 0;
	struct nf_conntrack_l3proto *old;

	if (proto->l3proto >= AF_MAX)
		return -EBUSY;

	if (proto->tuple_to_nlattr && !proto->nlattr_tuple_size)
		return -EINVAL;

	mutex_lock(&nf_ct_proto_mutex);
	old = rcu_dereference_protected(nf_ct_l3protos[proto->l3proto],
					lockdep_is_held(&nf_ct_proto_mutex));
	if (old != &nf_conntrack_l3proto_generic) {
		ret = -EBUSY;
		goto out_unlock;
	}

	ret = nf_ct_l3proto_register_sysctl(proto);
	if (ret < 0)
		goto out_unlock;

	if (proto->nlattr_tuple_size)
		proto->nla_size = 3 * proto->nlattr_tuple_size();

	rcu_assign_pointer(nf_ct_l3protos[proto->l3proto], proto);

out_unlock:
	mutex_unlock(&nf_ct_proto_mutex);
	return ret;
}
EXPORT_SYMBOL_GPL(nf_conntrack_l3proto_register);

void nf_conntrack_l3proto_unregister(struct nf_conntrack_l3proto *proto)
{
	struct net *net;

	BUG_ON(proto->l3proto >= AF_MAX);

	mutex_lock(&nf_ct_proto_mutex);
	BUG_ON(rcu_dereference_protected(nf_ct_l3protos[proto->l3proto],
					 lockdep_is_held(&nf_ct_proto_mutex)
					 ) != proto);
	rcu_assign_pointer(nf_ct_l3protos[proto->l3proto],
			   &nf_conntrack_l3proto_generic);
	nf_ct_l3proto_unregister_sysctl(proto);
	mutex_unlock(&nf_ct_proto_mutex);

	synchronize_rcu();

	/* Remove all contrack entries for this protocol */
	rtnl_lock();
	for_each_net(net)
		nf_ct_iterate_cleanup(net, kill_l3proto, proto);
	rtnl_unlock();
}
EXPORT_SYMBOL_GPL(nf_conntrack_l3proto_unregister);

static int nf_ct_l4proto_register_sysctl(struct nf_conntrack_l4proto *l4proto)
{
	int err = 0;

#ifdef CONFIG_SYSCTL
	if (l4proto->ctl_table != NULL) {
		err = nf_ct_register_sysctl(l4proto->ctl_table_header,
					    nf_net_netfilter_sysctl_path,
					    l4proto->ctl_table,
					    l4proto->ctl_table_users);
		if (err < 0)
			goto out;
	}
#ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
	if (l4proto->ctl_compat_table != NULL) {
		err = nf_ct_register_sysctl(&l4proto->ctl_compat_table_header,
					    nf_net_ipv4_netfilter_sysctl_path,
					    l4proto->ctl_compat_table, NULL);
		if (err == 0)
			goto out;
		nf_ct_unregister_sysctl(l4proto->ctl_table_header,
					l4proto->ctl_table,
					l4proto->ctl_table_users);
	}
#endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
out:
#endif /* CONFIG_SYSCTL */
	return err;
}

static void nf_ct_l4proto_unregister_sysctl(struct nf_conntrack_l4proto *l4proto)
{
#ifdef CONFIG_SYSCTL
	if (l4proto->ctl_table_header != NULL &&
	    *l4proto->ctl_table_header != NULL)
		nf_ct_unregister_sysctl(l4proto->ctl_table_header,
					l4proto->ctl_table,
					l4proto->ctl_table_users);
#ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
	if (l4proto->ctl_compat_table_header != NULL)
		nf_ct_unregister_sysctl(&l4proto->ctl_compat_table_header,
					l4proto->ctl_compat_table, NULL);
#endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
#endif /* CONFIG_SYSCTL */
}

/* FIXME: Allow NULL functions and sub in pointers to generic for
   them. --RR */
int nf_conntrack_l4proto_register(struct nf_conntrack_l4proto *l4proto)
{
	int ret = 0;

	if (l4proto->l3proto >= PF_MAX)
		return -EBUSY;

	if ((l4proto->to_nlattr && !l4proto->nlattr_size)
		|| (l4proto->tuple_to_nlattr && !l4proto->nlattr_tuple_size))
		return -EINVAL;

	mutex_lock(&nf_ct_proto_mutex);
	if (!nf_ct_protos[l4proto->l3proto]) {
		/* l3proto may be loaded latter. */
		struct nf_conntrack_l4proto __rcu **proto_array;
		int i;

		proto_array = kmalloc(MAX_NF_CT_PROTO *
				      sizeof(struct nf_conntrack_l4proto *),
				      GFP_KERNEL);
		if (proto_array == NULL) {
			ret = -ENOMEM;
			goto out_unlock;
		}

		for (i = 0; i < MAX_NF_CT_PROTO; i++)
			RCU_INIT_POINTER(proto_array[i], &nf_conntrack_l4proto_generic);

		/* Before making proto_array visible to lockless readers,
		 * we must make sure its content is committed to memory.
		 */
		smp_wmb();

		nf_ct_protos[l4proto->l3proto] = proto_array;
	} else if (rcu_dereference_protected(
			nf_ct_protos[l4proto->l3proto][l4proto->l4proto],
			lockdep_is_held(&nf_ct_proto_mutex)
			) != &nf_conntrack_l4proto_generic) {
		ret = -EBUSY;
		goto out_unlock;
	}

	ret = nf_ct_l4proto_register_sysctl(l4proto);
	if (ret < 0)
		goto out_unlock;

	l4proto->nla_size = 0;
	if (l4proto->nlattr_size)
		l4proto->nla_size += l4proto->nlattr_size();
	if (l4proto->nlattr_tuple_size)
		l4proto->nla_size += 3 * l4proto->nlattr_tuple_size();

	rcu_assign_pointer(nf_ct_protos[l4proto->l3proto][l4proto->l4proto],
			   l4proto);

out_unlock:
	mutex_unlock(&nf_ct_proto_mutex);
	return ret;
}
EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_register);

void nf_conntrack_l4proto_unregister(struct nf_conntrack_l4proto *l4proto)
{
	struct net *net;

	BUG_ON(l4proto->l3proto >= PF_MAX);

	mutex_lock(&nf_ct_proto_mutex);
	BUG_ON(rcu_dereference_protected(
			nf_ct_protos[l4proto->l3proto][l4proto->l4proto],
			lockdep_is_held(&nf_ct_proto_mutex)
			) != l4proto);
	rcu_assign_pointer(nf_ct_protos[l4proto->l3proto][l4proto->l4proto],
			   &nf_conntrack_l4proto_generic);
	nf_ct_l4proto_unregister_sysctl(l4proto);
	mutex_unlock(&nf_ct_proto_mutex);

	synchronize_rcu();

	/* Remove all contrack entries for this protocol */
	rtnl_lock();
	for_each_net(net)
		nf_ct_iterate_cleanup(net, kill_l4proto, l4proto);
	rtnl_unlock();
}
EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_unregister);

int nf_conntrack_proto_init(void)
{
	unsigned int i;
	int err;

	err = nf_ct_l4proto_register_sysctl(&nf_conntrack_l4proto_generic);
	if (err < 0)
		return err;

	for (i = 0; i < AF_MAX; i++)
		rcu_assign_pointer(nf_ct_l3protos[i],
				   &nf_conntrack_l3proto_generic);
	return 0;
}

void nf_conntrack_proto_fini(void)
{
	unsigned int i;

	nf_ct_l4proto_unregister_sysctl(&nf_conntrack_l4proto_generic);

	/* free l3proto protocol tables */
	for (i = 0; i < PF_MAX; i++)
		kfree(nf_ct_protos[i]);
}