1 files changed, 502 insertions, 0 deletions
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
new file mode 100644
index 000000000..bd9d31537
--- /dev/null
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -0,0 +1,502 @@
+/* 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 = 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) };
+	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) &&
+			    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);
+
+/* appropriate ct lock protecting must be taken by caller */
+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_raw(help->helper) == 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_expect_lock);
+	list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
+	spin_unlock_bh(&nf_conntrack_expect_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_expect_lock);
+	list_del_rcu(&n->head);
+	spin_unlock_bh(&nf_conntrack_expect_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_net(ct), 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;
+	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, &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 *next;
+	const struct hlist_nulls_node *nn;
+	unsigned int i;
+	int cpu;
+
+	/* Get rid of expectations */
+	spin_lock_bh(&nf_conntrack_expect_lock);
+	for (i = 0; i < nf_ct_expect_hsize; i++) {
+		hlist_for_each_entry_safe(exp, 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_expect_lock)
+					) == me || exp->helper == me) &&
+			    del_timer(&exp->timeout)) {
+				nf_ct_unlink_expect(exp);
+				nf_ct_expect_put(exp);
+			}
+		}
+	}
+	spin_unlock_bh(&nf_conntrack_expect_lock);
+
+	/* Get rid of expecteds, set helpers to NULL. */
+	for_each_possible_cpu(cpu) {
+		struct ct_pcpu *pcpu = per_cpu_ptr(net->ct.pcpu_lists, cpu);
+
+		spin_lock_bh(&pcpu->lock);
+		hlist_nulls_for_each_entry(h, nn, &pcpu->unconfirmed, hnnode)
+			unhelp(h, me);
+		spin_unlock_bh(&pcpu->lock);
+	}
+	local_bh_disable();
+	for (i = 0; i < net->ct.htable_size; i++) {
+		spin_lock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
+		if (i < net->ct.htable_size) {
+			hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
+				unhelp(h, me);
+		}
+		spin_unlock(&nf_conntrack_locks[i % CONNTRACK_LOCKS]);
+	}
+	local_bh_enable();
+}
+
+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();
+	for_each_net(net)
+		__nf_conntrack_helper_unregister(me, net);
+	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);
+}