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|
/* Helper handling for netfilter. */
/* (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>
* (C) 2006-2012 Patrick McHardy <kaber@trash.net>
*
* 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/skbuff.h>
#include <linux/vmalloc.h>
#include <linux/stddef.h>
#include <linux/random.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/rculist.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_helper.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_extend.h>
#include <net/netfilter/nf_log.h>
static DEFINE_MUTEX(nf_ct_helper_mutex);
struct hlist_head *nf_ct_helper_hash __read_mostly;
EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
unsigned int nf_ct_helper_hsize __read_mostly;
EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
static unsigned int nf_ct_helper_count __read_mostly;
static bool nf_ct_auto_assign_helper __read_mostly = false;
module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
MODULE_PARM_DESC(nf_conntrack_helper,
"Enable automatic conntrack helper assignment (default 0)");
#ifdef CONFIG_SYSCTL
static struct ctl_table helper_sysctl_table[] = {
{
.procname = "nf_conntrack_helper",
.data = &init_net.ct.sysctl_auto_assign_helper,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{}
};
static int nf_conntrack_helper_init_sysctl(struct net *net)
{
struct ctl_table *table;
table = kmemdup(helper_sysctl_table, sizeof(helper_sysctl_table),
GFP_KERNEL);
if (!table)
goto out;
table[0].data = &net->ct.sysctl_auto_assign_helper;
/* Don't export sysctls to unprivileged users */
if (net->user_ns != &init_user_ns)
table[0].procname = NULL;
net->ct.helper_sysctl_header =
register_net_sysctl(net, "net/netfilter", table);
if (!net->ct.helper_sysctl_header) {
pr_err("nf_conntrack_helper: can't register to sysctl.\n");
goto out_register;
}
return 0;
out_register:
kfree(table);
out:
return -ENOMEM;
}
static void nf_conntrack_helper_fini_sysctl(struct net *net)
{
struct ctl_table *table;
table = net->ct.helper_sysctl_header->ctl_table_arg;
unregister_net_sysctl_table(net->ct.helper_sysctl_header);
kfree(table);
}
#else
static int nf_conntrack_helper_init_sysctl(struct net *net)
{
return 0;
}
static void nf_conntrack_helper_fini_sysctl(struct net *net)
{
}
#endif /* CONFIG_SYSCTL */
/* Stupid hash, but collision free for the default registrations of the
* helpers currently in the kernel. */
static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
{
return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
(__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
}
static struct nf_conntrack_helper *
__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
{
struct nf_conntrack_helper *helper;
struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
unsigned int h;
if (!nf_ct_helper_count)
return NULL;
h = helper_hash(tuple);
hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
return helper;
}
return NULL;
}
struct nf_conntrack_helper *
__nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
{
struct nf_conntrack_helper *h;
unsigned int i;
for (i = 0; i < nf_ct_helper_hsize; i++) {
hlist_for_each_entry_rcu(h, &nf_ct_helper_hash[i], hnode) {
if (strcmp(h->name, name))
continue;
if (h->tuple.src.l3num != NFPROTO_UNSPEC &&
h->tuple.src.l3num != l3num)
continue;
if (h->tuple.dst.protonum == protonum)
return h;
}
}
return NULL;
}
EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
struct nf_conntrack_helper *
nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
{
struct nf_conntrack_helper *h;
rcu_read_lock();
h = __nf_conntrack_helper_find(name, l3num, protonum);
#ifdef CONFIG_MODULES
if (h == NULL) {
rcu_read_unlock();
if (request_module("nfct-helper-%s", name) == 0) {
rcu_read_lock();
h = __nf_conntrack_helper_find(name, l3num, protonum);
} else {
return h;
}
}
#endif
if (h != NULL && !try_module_get(h->me))
h = NULL;
if (h != NULL && !refcount_inc_not_zero(&h->refcnt)) {
module_put(h->me);
h = NULL;
}
rcu_read_unlock();
return h;
}
EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
void nf_conntrack_helper_put(struct nf_conntrack_helper *helper)
{
refcount_dec(&helper->refcnt);
module_put(helper->me);
}
EXPORT_SYMBOL_GPL(nf_conntrack_helper_put);
struct nf_conn_help *
nf_ct_helper_ext_add(struct nf_conn *ct,
struct nf_conntrack_helper *helper, gfp_t gfp)
{
struct nf_conn_help *help;
help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
if (help)
INIT_HLIST_HEAD(&help->expectations);
else
pr_debug("failed to add helper extension area");
return help;
}
EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
static struct nf_conntrack_helper *
nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
{
if (!net->ct.sysctl_auto_assign_helper) {
if (net->ct.auto_assign_helper_warned)
return NULL;
if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
return NULL;
pr_info("nf_conntrack: default automatic helper assignment "
"has been turned off for security reasons and CT-based "
" firewall rule not found. Use the iptables CT target "
"to attach helpers instead.\n");
net->ct.auto_assign_helper_warned = 1;
return NULL;
}
return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
}
int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
gfp_t flags)
{
struct nf_conntrack_helper *helper = NULL;
struct nf_conn_help *help;
struct net *net = nf_ct_net(ct);
/* We already got a helper explicitly attached. The function
* nf_conntrack_alter_reply - in case NAT is in use - asks for looking
* the helper up again. Since now the user is in full control of
* making consistent helper configurations, skip this automatic
* re-lookup, otherwise we'll lose the helper.
*/
|