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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>
*
* 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 = true;
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 1)");
#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) };
struct hlist_node *n;
unsigned int h;
if (!nf_ct_helper_count)
return NULL;
h = helper_hash(tuple);
hlist_for_each_entry_rcu(helper, n, &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;
struct hlist_node *n;
unsigned int i;
for (i = 0; i < nf_ct_helper_hsize; i++) {
hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
if (!strcmp(h->name, name) &&
h->tuple.src.l3num == l3num &&
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;
h = __nf_conntrack_helper_find(name, l3num, protonum);
#ifdef CONFIG_MODULES
if (h == NULL) {
if (request_module("nfct-helper-%s", name) == 0)
h = __nf_conntrack_helper_find(name, l3num, protonum);
}
#endif
if (h != NULL && !try_module_get(h->me))
h = NULL;
return h;
}
EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
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_length(ct, NF_CT_EXT_HELPER,
helper->data_len, 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);
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);
int ret = 0;
/* 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.
*/
if (test_bit(IPS_HELPER_BIT, &ct->status))
return 0;
if (tmpl != NULL) {
help = nfct_help(tmpl);
if (help != NULL) {
helper = help->helper;
set_bit(IPS_HELPER_BIT, &ct->status);
}
}
help = nfct_help(ct);
if (net->ct.sysctl_auto_assign_helper && helper == NULL) {
helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
if (unlikely(!net->ct.auto_assign_helper_warned && helper)) {
pr_info("nf_conntrack: automatic helper "
"assignment is deprecated and it will "
"be removed soon. Use the iptables CT target "
"to attach helpers instead.\n");
net->ct.auto_assign_helper_warned = true;
}
}
if (helper == NULL) {
if (help)
RCU_INIT_POINTER(help->helper, NULL);
goto out;
}
if (help == NULL) {
help = nf_ct_helper_ext_add(ct, helper, flags);
if (help == NULL) {
ret = -ENOMEM;
goto out;
}
} else {
/* We only allow helper re-assignment of the same sort since
* we cannot reallocate the helper extension area.
*/
struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
if (tmp && tmp->help != helper->help) {
RCU_INIT_POINTER(help->helper, NULL);
goto out;
}
}
rcu_assign_pointer(help->helper, helper);
out:
return ret;
}
EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
static inline int unhelp(struct nf_conntrack_tuple_hash *i,
const struct nf_conntrack_helper *me)
{
struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
struct nf_conn_help *help = nfct_help(ct);
if (help && rcu_dereference_protected(
help->helper,
lockdep_is_held(&nf_conntrack_lock)
) == me) {
nf_conntrack_event(IPCT_HELPER, ct);
RCU_INIT_POINTER(help->helper, NULL);
}
return 0;
}
void nf_ct_helper_destroy(struct nf_conn *ct)
{
struct nf_conn_help *help = nfct_help(ct);
struct nf_conntrack_helper *helper;
if (help) {
rcu_read_lock();
helper = rcu_dereference(help->helper);
if (helper && helper->destroy)
helper->destroy(ct);
rcu_read_unlock();
}
}
static LIST_HEAD(nf_ct_helper_expectfn_list);
void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
{
spin_lock_bh(&nf_conntrack_lock);
list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
spin_unlock_bh(&nf_conntrack_lock);
}
EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
{
spin_lock_bh(&nf_conntrack_lock);
list_del_rcu(&n->head);
spin_unlock_bh(&nf_conntrack_lock);
}
EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
struct nf_ct_helper_expectfn *
nf_ct_helper_expectfn_find_by_name(const char *name)
{
struct nf_ct_helper_expectfn *cur;
bool found = false;
rcu_read_lock();
list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
if (!strcmp(cur->name, name)) {
found = true;
break;
}
}
rcu_read_unlock();
return found ? cur : NULL;
}
EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
struct nf_ct_helper_expectfn *
nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
{
struct nf_ct_helper_expectfn *cur;
bool found = false;
rcu_read_lock();
list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
if (cur->expectfn == symbol) {
found = true;
break;
}
}
rcu_read_unlock();
return found ? cur : NULL;
}
EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
__printf(3, 4)
void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
const char *fmt, ...)
{
const struct nf_conn_help *help;
const struct nf_conntrack_helper *helper;
struct va_format vaf;
va_list args;
va_start(args, fmt);
vaf.fmt = fmt;
vaf.va = &args;
/* Called from the helper function, this call never fails */
help = nfct_help(ct);
/* rcu_read_lock()ed by nf_hook_slow */
helper = rcu_dereference(help->helper);
nf_log_packet(nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
"nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
va_end(args);
}
EXPORT_SYMBOL_GPL(nf_ct_helper_log);
int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
{
int ret = 0;
struct nf_conntrack_helper *cur;
struct hlist_node *n;
unsigned int h = helper_hash(&me->tuple);
BUG_ON(me->expect_policy == NULL);
BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
mutex_lock(&nf_ct_helper_mutex);
hlist_for_each_entry(cur, n, &nf_ct_helper_hash[h], hnode) {
if (strncmp(cur->name, me->name, NF_CT_HELPER_NAME_LEN) == 0 &&
cur->tuple.src.l3num == me->tuple.src.l3num &&
cur->tuple.dst.protonum == me->tuple.dst.protonum) {
ret = -EEXIST;
goto out;
}
}
hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
nf_ct_helper_count++;
out:
mutex_unlock(&nf_ct_helper_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
struct net *net)
{
struct nf_conntrack_tuple_hash *h;
struct nf_conntrack_expect *exp;
const struct hlist_node *n, *next;
const struct hlist_nulls_node *nn;
unsigned int i;
/* Get rid of expectations */
for (i = 0; i < nf_ct_expect_hsize; i++) {
hlist_for_each_entry_safe(exp, n, next,
&net->ct.expect_hash[i], hnode) {
struct nf_conn_help *help = nfct_help(exp->master);
if ((rcu_dereference_protected(
help->helper,
lockdep_is_held(&nf_conntrack_lock)
) == me || exp->helper == me) &&
del_timer(&exp->timeout)) {
nf_ct_unlink_expect(exp);
nf_ct_expect_put(exp);
}
}
}
/* Get rid of expecteds, set helpers to NULL. */
hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
unhelp(h, me);
for (i = 0; i < net->ct.htable_size; i++) {
hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
unhelp(h, me);
}
}
void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
{
struct net *net;
mutex_lock(&nf_ct_helper_mutex);
hlist_del_rcu(&me->hnode);
nf_ct_helper_count--;
mutex_unlock(&nf_ct_helper_mutex);
/* Make sure every nothing is still using the helper unless its a
* connection in the hash.
*/
synchronize_rcu();
rtnl_lock();
spin_lock_bh(&nf_conntrack_lock);
for_each_net(net)
__nf_conntrack_helper_unregister(me, net);
spin_unlock_bh(&nf_conntrack_lock);
rtnl_unlock();
}
EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
static struct nf_ct_ext_type helper_extend __read_mostly = {
.len = sizeof(struct nf_conn_help),
.align = __alignof__(struct nf_conn_help),
.id = NF_CT_EXT_HELPER,
};
int nf_conntrack_helper_pernet_init(struct net *net)
{
net->ct.auto_assign_helper_warned = false;
net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
return nf_conntrack_helper_init_sysctl(net);
}
void nf_conntrack_helper_pernet_fini(struct net *net)
{
nf_conntrack_helper_fini_sysctl(net);
}
int nf_conntrack_helper_init(void)
{
int ret;
nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
nf_ct_helper_hash =
nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
if (!nf_ct_helper_hash)
return -ENOMEM;
ret = nf_ct_extend_register(&helper_extend);
if (ret < 0) {
pr_err("nf_ct_helper: Unable to register helper extension.\n");
goto out_extend;
}
return 0;
out_extend:
nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
return ret;
}
void nf_conntrack_helper_fini(void)
{
nf_ct_extend_unregister(&helper_extend);
nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
}
|