[INET]: Introduce tunnel4/tunnel6

Basically this patch moves the generic tunnel protocol stuff out of
xfrm4_tunnel/xfrm6_tunnel and moves it into the new files of tunnel4.c
and tunnel6 respectively.

The reason for this is that the problem that Hugo uncovered is only
the tip of the iceberg.  The real problem is that when we removed the
dependency of ipip on xfrm4_tunnel we didn't really consider the module
case at all.

For instance, as it is it's possible to build both ipip and xfrm4_tunnel
as modules and if the latter is loaded then ipip simply won't load.

After considering the alternatives I've decided that the best way out of
this is to restore the dependency of ipip on the non-xfrm-specific part
of xfrm4_tunnel.  This is acceptable IMHO because the intention of the
removal was really to be able to use ipip without the xfrm subsystem.
This is still preserved by this patch.

So now both ipip/xfrm4_tunnel depend on the new tunnel4.c which handles
the arbitration between the two.  The order of processing is determined
by a simple integer which ensures that ipip gets processed before
xfrm4_tunnel.

The situation for ICMP handling is a little bit more complicated since
we may not have enough information to determine who it's for.  It's not
a big deal at the moment since the xfrm ICMP handlers are basically
no-ops.  In future we can deal with this when we look at ICMP caching
in general.

The user-visible change to this is the removal of the TUNNEL Kconfig
prompts.  This makes sense because it can only be used through IPCOMP
as it stands.

The addition of the new modules shouldn't introduce any problems since
module dependency will cause them to be loaded.

Oh and I also turned some unnecessary pskb's in IPv6 related to this
patch to skb's.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 66 deletions

diff --git a/net/ipv4/xfrm4_tunnel.c b/net/ipv4/xfrm4_tunnel.c
index b08d56b117f8..2d670935c2b5 100644
--- a/net/ipv4/xfrm4_tunnel.c
+++ b/net/ipv4/xfrm4_tunnel.c
@@ -26,64 +26,6 @@ static int ipip_xfrm_rcv(struct xfrm_state *x, struct xfrm_decap_state *decap, s
 	return 0;
 }
 
-static struct xfrm_tunnel *ipip_handler;
-static DEFINE_MUTEX(xfrm4_tunnel_mutex);
-
-int xfrm4_tunnel_register(struct xfrm_tunnel *handler)
-{
-	int ret;
-
-	mutex_lock(&xfrm4_tunnel_mutex);
-	ret = 0;
-	if (ipip_handler != NULL)
-		ret = -EINVAL;
-	if (!ret)
-		ipip_handler = handler;
-	mutex_unlock(&xfrm4_tunnel_mutex);
-
-	return ret;
-}
-
-EXPORT_SYMBOL(xfrm4_tunnel_register);
-
-int xfrm4_tunnel_deregister(struct xfrm_tunnel *handler)
-{
-	int ret;
-
-	mutex_lock(&xfrm4_tunnel_mutex);
-	ret = 0;
-	if (ipip_handler != handler)
-		ret = -EINVAL;
-	if (!ret)
-		ipip_handler = NULL;
-	mutex_unlock(&xfrm4_tunnel_mutex);
-
-	synchronize_net();
-
-	return ret;
-}
-
-EXPORT_SYMBOL(xfrm4_tunnel_deregister);
-
-static int ipip_rcv(struct sk_buff *skb)
-{
-	struct xfrm_tunnel *handler = ipip_handler;
-
-	/* Tunnel devices take precedence.  */
-	if (handler && handler->handler(skb) == 0)
-		return 0;
-
-	return xfrm4_rcv(skb);
-}
-
-static void ipip_err(struct sk_buff *skb, u32 info)
-{
-	struct xfrm_tunnel *handler = ipip_handler;
-
-	if (handler)
-		handler->err_handler(skb, info);
-}
-
 static int ipip_init_state(struct xfrm_state *x)
 {
 	if (!x->props.mode)
@@ -111,10 +53,15 @@ static struct xfrm_type ipip_type = {
 	.output		= ipip_output
 };
 
-static struct net_protocol ipip_protocol = {
-	.handler	=	ipip_rcv,
-	.err_handler	=	ipip_err,
-	.no_policy	=	1,
+static int xfrm_tunnel_err(struct sk_buff *skb, u32 info)
+{
+	return -ENOENT;
+}
+
+static struct xfrm_tunnel xfrm_tunnel_handler = {
+	.handler	=	xfrm4_rcv,
+	.err_handler	=	xfrm_tunnel_err,
+	.priority	=	2,
 };
 
 static int __init ipip_init(void)
@@ -123,8 +70,8 @@ static int __init ipip_init(void)
 		printk(KERN_INFO "ipip init: can't add xfrm type\n");
 		return -EAGAIN;
 	}
-	if (inet_add_protocol(&ipip_protocol, IPPROTO_IPIP) < 0) {
-		printk(KERN_INFO "ipip init: can't add protocol\n");
+	if (xfrm4_tunnel_register(&xfrm_tunnel_handler)) {
+		printk(KERN_INFO "ipip init: can't add xfrm handler\n");
 		xfrm_unregister_type(&ipip_type, AF_INET);
 		return -EAGAIN;
 	}
@@ -133,8 +80,8 @@ static int __init ipip_init(void)
 
 static void __exit ipip_fini(void)
 {
-	if (inet_del_protocol(&ipip_protocol, IPPROTO_IPIP) < 0)
-		printk(KERN_INFO "ipip close: can't remove protocol\n");
+	if (xfrm4_tunnel_deregister(&xfrm_tunnel_handler))
+		printk(KERN_INFO "ipip close: can't remove xfrm handler\n");
 	if (xfrm_unregister_type(&ipip_type, AF_INET) < 0)
 		printk(KERN_INFO "ipip close: can't remove xfrm type\n");
 }