xfrm6: Add IPsec protocol multiplexer

This patch adds an IPsec protocol multiplexer for ipv6. With
this it is possible to add alternative protocol handlers, as
needed for IPsec virtual tunnel interfaces.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

3 files changed, 278 insertions, 1 deletions

diff --git a/net/ipv6/Makefile b/net/ipv6/Makefile
index 17bb830872db..2fe68364bb20 100644
--- a/net/ipv6/Makefile
+++ b/net/ipv6/Makefile
@@ -16,7 +16,7 @@ ipv6-$(CONFIG_SYSCTL) = sysctl_net_ipv6.o
 ipv6-$(CONFIG_IPV6_MROUTE) += ip6mr.o
 
 ipv6-$(CONFIG_XFRM) += xfrm6_policy.o xfrm6_state.o xfrm6_input.o \
-	xfrm6_output.o
+	xfrm6_output.o xfrm6_protocol.o
 ipv6-$(CONFIG_NETFILTER) += netfilter.o
 ipv6-$(CONFIG_IPV6_MULTIPLE_TABLES) += fib6_rules.o
 ipv6-$(CONFIG_PROC_FS) += proc.o
diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c
index 5f8e128c512d..2a0bbda2c76a 100644
--- a/net/ipv6/xfrm6_policy.c
+++ b/net/ipv6/xfrm6_policy.c
@@ -389,11 +389,17 @@ int __init xfrm6_init(void)
 	if (ret)
 		goto out_policy;
 
+	ret = xfrm6_protocol_init();
+	if (ret)
+		goto out_state;
+
 #ifdef CONFIG_SYSCTL
 	register_pernet_subsys(&xfrm6_net_ops);
 #endif
 out:
 	return ret;
+out_state:
+	xfrm6_state_fini();
 out_policy:
 	xfrm6_policy_fini();
 	goto out;
@@ -404,6 +410,7 @@ void xfrm6_fini(void)
 #ifdef CONFIG_SYSCTL
 	unregister_pernet_subsys(&xfrm6_net_ops);
 #endif
+	xfrm6_protocol_fini();
 	xfrm6_policy_fini();
 	xfrm6_state_fini();
 	dst_entries_destroy(&xfrm6_dst_ops);
diff --git a/net/ipv6/xfrm6_protocol.c b/net/ipv6/xfrm6_protocol.c
new file mode 100644
index 000000000000..6ab989c486f7
--- /dev/null
+++ b/net/ipv6/xfrm6_protocol.c
@@ -0,0 +1,270 @@
+/* xfrm6_protocol.c - Generic xfrm protocol multiplexer for ipv6.
+ *
+ * Copyright (C) 2013 secunet Security Networks AG
+ *
+ * Author:
+ * Steffen Klassert <steffen.klassert@secunet.com>
+ *
+ * Based on:
+ * net/ipv4/xfrm4_protocol.c
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/init.h>
+#include <linux/mutex.h>
+#include <linux/skbuff.h>
+#include <linux/icmpv6.h>
+#include <net/ipv6.h>
+#include <net/protocol.h>
+#include <net/xfrm.h>
+
+static struct xfrm6_protocol __rcu *esp6_handlers __read_mostly;
+static struct xfrm6_protocol __rcu *ah6_handlers __read_mostly;
+static struct xfrm6_protocol __rcu *ipcomp6_handlers __read_mostly;
+static DEFINE_MUTEX(xfrm6_protocol_mutex);
+
+static inline struct xfrm6_protocol __rcu **proto_handlers(u8 protocol)
+{
+	switch (protocol) {
+	case IPPROTO_ESP:
+		return &esp6_handlers;
+	case IPPROTO_AH:
+		return &ah6_handlers;
+	case IPPROTO_COMP:
+		return &ipcomp6_handlers;
+	}
+
+	return NULL;
+}
+
+#define for_each_protocol_rcu(head, handler)		\
+	for (handler = rcu_dereference(head);		\
+	     handler != NULL;				\
+	     handler = rcu_dereference(handler->next))	\
+
+int xfrm6_rcv_cb(struct sk_buff *skb, u8 protocol, int err)
+{
+	int ret;
+	struct xfrm6_protocol *handler;
+
+	for_each_protocol_rcu(*proto_handlers(protocol), handler)
+		if ((ret = handler->cb_handler(skb, err)) <= 0)
+			return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(xfrm6_rcv_cb);
+
+static int xfrm6_esp_rcv(struct sk_buff *skb)
+{
+	int ret;
+	struct xfrm6_protocol *handler;
+
+	XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip6 = NULL;
+
+	for_each_protocol_rcu(esp6_handlers, handler)
+		if ((ret = handler->handler(skb)) != -EINVAL)
+			return ret;
+
+	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
+
+	kfree_skb(skb);
+	return 0;
+}
+
+static void xfrm6_esp_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
+			  u8 type, u8 code, int offset, __be32 info)
+{
+	struct xfrm6_protocol *handler;
+
+	for_each_protocol_rcu(esp6_handlers, handler)
+		if (!handler->err_handler(skb, opt, type, code, offset, info))
+			break;
+}
+
+static int xfrm6_ah_rcv(struct sk_buff *skb)
+{
+	int ret;
+	struct xfrm6_protocol *handler;
+
+	XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip6 = NULL;
+
+	for_each_protocol_rcu(ah6_handlers, handler)
+		if ((ret = handler->handler(skb)) != -EINVAL)
+			return ret;
+
+	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
+
+	kfree_skb(skb);
+	return 0;
+}
+
+static void xfrm6_ah_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
+			 u8 type, u8 code, int offset, __be32 info)
+{
+	struct xfrm6_protocol *handler;
+
+	for_each_protocol_rcu(ah6_handlers, handler)
+		if (!handler->err_handler(skb, opt, type, code, offset, info))
+			break;
+}
+
+static int xfrm6_ipcomp_rcv(struct sk_buff *skb)
+{
+	int ret;
+	struct xfrm6_protocol *handler;
+
+	XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip6 = NULL;
+
+	for_each_protocol_rcu(ipcomp6_handlers, handler)
+		if ((ret = handler->handler(skb)) != -EINVAL)
+			return ret;
+
+	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
+
+	kfree_skb(skb);
+	return 0;
+}
+
+static void xfrm6_ipcomp_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
+			     u8 type, u8 code, int offset, __be32 info)
+{
+	struct xfrm6_protocol *handler;
+
+	for_each_protocol_rcu(ipcomp6_handlers, handler)
+		if (!handler->err_handler(skb, opt, type, code, offset, info))
+			break;
+}
+
+static const struct inet6_protocol esp6_protocol = {
+	.handler	=	xfrm6_esp_rcv,
+	.err_handler	=	xfrm6_esp_err,
+	.flags		=	INET6_PROTO_NOPOLICY,
+};
+
+static const struct inet6_protocol ah6_protocol = {
+	.handler	=	xfrm6_ah_rcv,
+	.err_handler	=	xfrm6_ah_err,
+	.flags		=	INET6_PROTO_NOPOLICY,
+};
+
+static const struct inet6_protocol ipcomp6_protocol = {
+	.handler	=	xfrm6_ipcomp_rcv,
+	.err_handler	=	xfrm6_ipcomp_err,
+	.flags		=	INET6_PROTO_NOPOLICY,
+};
+
+static struct xfrm_input_afinfo xfrm6_input_afinfo = {
+	.family		=	AF_INET6,
+	.owner		=	THIS_MODULE,
+	.callback	=	xfrm6_rcv_cb,
+};
+
+static inline const struct inet6_protocol *netproto(unsigned char protocol)
+{
+	switch (protocol) {
+	case IPPROTO_ESP:
+		return &esp6_protocol;
+	case IPPROTO_AH:
+		return &ah6_protocol;
+	case IPPROTO_COMP:
+		return &ipcomp6_protocol;
+	}
+
+	return NULL;
+}
+
+int xfrm6_protocol_register(struct xfrm6_protocol *handler,
+			    unsigned char protocol)
+{
+	struct xfrm6_protocol __rcu **pprev;
+	struct xfrm6_protocol *t;
+	bool add_netproto = false;
+
+	int ret = -EEXIST;
+	int priority = handler->priority;
+
+	mutex_lock(&xfrm6_protocol_mutex);
+
+	if (!rcu_dereference_protected(*proto_handlers(protocol),
+				       lockdep_is_held(&xfrm6_protocol_mutex)))
+		add_netproto = true;
+
+	for (pprev = proto_handlers(protocol);
+	     (t = rcu_dereference_protected(*pprev,
+			lockdep_is_held(&xfrm6_protocol_mutex))) != NULL;
+	     pprev = &t->next) {
+		if (t->priority < priority)
+			break;
+		if (t->priority == priority)
+			goto err;
+	}
+
+	handler->next = *pprev;
+	rcu_assign_pointer(*pprev, handler);
+
+	ret = 0;
+
+err:
+	mutex_unlock(&xfrm6_protocol_mutex);
+
+	if (add_netproto) {
+		if (inet6_add_protocol(netproto(protocol), protocol)) {
+			pr_err("%s: can't add protocol\n", __func__);
+			ret = -EAGAIN;
+		}
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(xfrm6_protocol_register);
+
+int xfrm6_protocol_deregister(struct xfrm6_protocol *handler,
+			      unsigned char protocol)
+{
+	struct xfrm6_protocol __rcu **pprev;
+	struct xfrm6_protocol *t;
+	int ret = -ENOENT;
+
+	mutex_lock(&xfrm6_protocol_mutex);
+
+	for (pprev = proto_handlers(protocol);
+	     (t = rcu_dereference_protected(*pprev,
+			lockdep_is_held(&xfrm6_protocol_mutex))) != NULL;
+	     pprev = &t->next) {
+		if (t == handler) {
+			*pprev = handler->next;
+			ret = 0;
+			break;
+		}
+	}
+
+	if (!rcu_dereference_protected(*proto_handlers(protocol),
+				       lockdep_is_held(&xfrm6_protocol_mutex))) {
+		if (inet6_del_protocol(netproto(protocol), protocol) < 0) {
+			pr_err("%s: can't remove protocol\n", __func__);
+			ret = -EAGAIN;
+		}
+	}
+
+	mutex_unlock(&xfrm6_protocol_mutex);
+
+	synchronize_net();
+
+	return ret;
+}
+EXPORT_SYMBOL(xfrm6_protocol_deregister);
+
+int __init xfrm6_protocol_init(void)
+{
+	return xfrm_input_register_afinfo(&xfrm6_input_afinfo);
+}
+
+void xfrm6_protocol_fini(void)
+{
+	xfrm_input_unregister_afinfo(&xfrm6_input_afinfo);
+}