1 files changed, 520 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..bf09a1e06
--- /dev/null
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -0,0 +1,520 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* 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>
+ */
+
+#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_core.h>
+#include <net/netfilter/nf_conntrack_ecache.h>
+#include <net/netfilter/nf_conntrack_extend.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_l4proto.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 DEFINE_MUTEX(nf_ct_nat_helpers_mutex);
+static struct list_head nf_ct_nat_helpers __read_mostly;
+
+/* 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;
+}
+
+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);
+
+static struct nf_conntrack_nat_helper *
+nf_conntrack_nat_helper_find(const char *mod_name)
+{
+	struct nf_conntrack_nat_helper *cur;
+	bool found = false;
+
+	list_for_each_entry_rcu(cur, &nf_ct_nat_helpers, list) {
+		if (!strcmp(cur->mod_name, mod_name)) {
+			found = true;
+			break;
+		}
+	}
+	return found ? cur : NULL;
+}
+
+int
+nf_nat_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
+{
+	struct nf_conntrack_helper *h;
+	struct nf_conntrack_nat_helper *nat;
+	char mod_name[NF_CT_HELPER_NAME_LEN];
+	int ret = 0;
+
+	rcu_read_lock();
+	h = __nf_conntrack_helper_find(name, l3num, protonum);
+	if (!h) {
+		rcu_read_unlock();
+		return -ENOENT;
+	}
+
+	nat = nf_conntrack_nat_helper_find(h->nat_mod_name);
+	if (!nat) {
+		snprintf(mod_name, sizeof(mod_name), "%s", h->nat_mod_name);
+		rcu_read_unlock();
+		request_module("%s", mod_name);
+
+		rcu_read_lock();
+		nat = nf_conntrack_nat_helper_find(mod_name);
+		if (!nat) {
+			rcu_read_unlock();
+			return -ENOENT;
+		}
+	}
+
+	if (!try_module_get(nat->module))
+		ret = -ENOENT;
+
+	rcu_read_unlock();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nf_nat_helper_try_module_get);
+
+void nf_nat_helper_put(struct nf_conntrack_helper *helper)
+{
+	struct nf_conntrack_nat_helper *nat;
+
+	nat = nf_conntrack_nat_helper_find(helper->nat_mod_name);
+	if (WARN_ON_ONCE(!nat))
+		return;
+
+	module_put(nat->module);
+}
+EXPORT_SYMBOL_GPL(nf_nat_helper_put);
+
+struct nf_conn_help *
+nf_ct_helper_ext_add(struct nf_conn *ct, 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);
+
+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;
+
+	/* 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 (WARN_ON_ONCE(!tmpl))
+		return 0;
+
+	help = nfct_help(tmpl);
+	if (help != NULL) {
+		helper = rcu_dereference(help->helper);
+		set_bit(IPS_HELPER_BIT, &ct->status);
+	}
+
+	help = nfct_help(ct);
+
+	if (helper == NULL) {
+		if (help)
+			RCU_INIT_POINTER(help->helper, NULL);
+		return 0;
+	}
+
+	if (help == NULL) {
+		help = nf_ct_helper_ext_add(ct, flags);
+		if (help == NULL)
+			return -ENOMEM;
+	} 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);
+			return 0;
+		}
+	}
+
+	rcu_assign_pointer(help->helper, helper);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
+
+/* appropriate ct lock protecting must be taken by caller */
+static int unhelp(struct nf_conn *ct, void *me)
+{
+	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);
+	}
+
+	/* We are not intended to delete this conntrack. */
+	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);
+
+/* Caller should hold the rcu lock */
+struct nf_ct_helper_expectfn *
+nf_ct_helper_expectfn_find_by_name(const char *name)
+{
+	struct nf_ct_helper_expectfn *cur;
+	bool found = false;
+
+	list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
+		if (!strcmp(cur->name, name)) {
+			found = true;
+			break;
+		}
+	}
+	return found ? cur : NULL;
+}
+EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
+
+/* Caller should hold the rcu lock */
+struct nf_ct_helper_expectfn *
+nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
+{
+	struct nf_ct_helper_expectfn *cur;
+	bool found = false;
+
+	list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
+		if (cur->expectfn == symbol) {
+			found = true;
+			break;
+		}
+	}
+	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_thresh */
+	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)
+{
+	struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
+	unsigned int h = helper_hash(&me->tuple);
+	struct nf_conntrack_helper *cur;
+	int ret = 0, i;
+
+	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);
+
+	if (!nf_ct_helper_hash)
+		return -ENOENT;
+
+	if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
+		return -EINVAL;
+
+	mutex_lock(&nf_ct_helper_mutex);
+	for (i = 0; i < nf_ct_helper_hsize; i++) {
+		hlist_for_each_entry(cur, &nf_ct_helper_hash[i], hnode) {
+			if (!strcmp(cur->name, me->name) &&
+			    (cur->tuple.src.l3num == NFPROTO_UNSPEC ||
+			     cur->tuple.src.l3num == me->tuple.src.l3num) &&
+			    cur->tuple.dst.protonum == me->tuple.dst.protonum) {
+				ret = -EEXIST;
+				goto out;
+			}
+		}
+	}
+
+	/* avoid unpredictable behaviour for auto_assign_helper */
+	if (!(me->flags & NF_CT_HELPER_F_USERSPACE)) {
+		hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
+			if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple,
+						     &mask)) {
+				ret = -EEXIST;
+				goto out;
+			}
+		}
+	}
+	refcount_set(&me->refcnt, 1);
+	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 bool expect_iter_me(struct nf_conntrack_expect *exp, void *data)
+{
+	struct nf_conn_help *help = nfct_help(exp->master);
+	const struct nf_conntrack_helper *me = data;
+	const struct nf_conntrack_helper *this;
+
+	if (exp->helper == me)
+		return true;
+
+	this = rcu_dereference_protected(help->helper,
+					 lockdep_is_held(&nf_conntrack_expect_lock));
+	return this == me;
+}
+
+void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
+{
+	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();
+
+	nf_ct_expect_iterate_destroy(expect_iter_me, NULL);
+	nf_ct_iterate_destroy(unhelp, me);
+}
+EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
+
+void nf_ct_helper_init(struct nf_conntrack_helper *helper,
+		       u16 l3num, u16 protonum, const char *name,
+		       u16 default_port, u16 spec_port, u32 id,
+		       const struct nf_conntrack_expect_policy *exp_pol,
+		       u32 expect_class_max,
+		       int (*help)(struct sk_buff *skb, unsigned int protoff,
+				   struct nf_conn *ct,
+				   enum ip_conntrack_info ctinfo),
+		       int (*from_nlattr)(struct nlattr *attr,
+					  struct nf_conn *ct),
+		       struct module *module)
+{
+	helper->tuple.src.l3num = l3num;
+	helper->tuple.dst.protonum = protonum;
+	helper->tuple.src.u.all = htons(spec_port);
+	helper->expect_policy = exp_pol;
+	helper->expect_class_max = expect_class_max;
+	helper->help = help;
+	helper->from_nlattr = from_nlattr;
+	helper->me = module;
+	snprintf(helper->nat_mod_name, sizeof(helper->nat_mod_name),
+		 NF_NAT_HELPER_PREFIX "%s", name);
+
+	if (spec_port == default_port)
+		snprintf(helper->name, sizeof(helper->name), "%s", name);
+	else
+		snprintf(helper->name, sizeof(helper->name), "%s-%u", name, id);
+}
+EXPORT_SYMBOL_GPL(nf_ct_helper_init);
+
+int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
+				  unsigned int n)
+{
+	unsigned int i;
+	int err = 0;
+
+	for (i = 0; i < n; i++) {
+		err = nf_conntrack_helper_register(&helper[i]);
+		if (err < 0)
+			goto err;
+	}
+
+	return err;
+err:
+	if (i > 0)
+		nf_conntrack_helpers_unregister(helper, i);
+	return err;
+}
+EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
+
+void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
+				unsigned int n)
+{
+	while (n-- > 0)
+		nf_conntrack_helper_unregister(&helper[n]);
+}
+EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
+
+void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat)
+{
+	mutex_lock(&nf_ct_nat_helpers_mutex);
+	list_add_rcu(&nat->list, &nf_ct_nat_helpers);
+	mutex_unlock(&nf_ct_nat_helpers_mutex);
+}
+EXPORT_SYMBOL_GPL(nf_nat_helper_register);
+
+void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat)
+{
+	mutex_lock(&nf_ct_nat_helpers_mutex);
+	list_del_rcu(&nat->list);
+	mutex_unlock(&nf_ct_nat_helpers_mutex);
+}
+EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
+
+int nf_conntrack_helper_init(void)
+{
+	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;
+
+	INIT_LIST_HEAD(&nf_ct_nat_helpers);
+	return 0;
+}
+
+void nf_conntrack_helper_fini(void)
+{
+	kvfree(nf_ct_helper_hash);
+	nf_ct_helper_hash = NULL;
+}