[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, 131 insertions, 0 deletions

diff --git a/net/ipv6/tunnel6.c b/net/ipv6/tunnel6.c
new file mode 100644
index 00000000000..5659b52284b
--- /dev/null
+++ b/net/ipv6/tunnel6.c
@@ -0,0 +1,131 @@
+/*
+ * Copyright (C)2003,2004 USAGI/WIDE Project
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Authors	Mitsuru KANDA  <mk@linux-ipv6.org>
+ * 		YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <net/protocol.h>
+#include <net/xfrm.h>
+
+static struct xfrm6_tunnel *tunnel6_handlers;
+static DEFINE_MUTEX(tunnel6_mutex);
+
+int xfrm6_tunnel_register(struct xfrm6_tunnel *handler)
+{
+	struct xfrm6_tunnel **pprev;
+	int ret = -EEXIST;
+	int priority = handler->priority;
+
+	mutex_lock(&tunnel6_mutex);
+
+	for (pprev = &tunnel6_handlers; *pprev; pprev = &(*pprev)->next) {
+		if ((*pprev)->priority > priority)
+			break;
+		if ((*pprev)->priority == priority)
+			goto err;
+	}
+
+	handler->next = *pprev;
+	*pprev = handler;
+
+	ret = 0;
+
+err:
+	mutex_unlock(&tunnel6_mutex);
+
+	return ret;
+}
+
+EXPORT_SYMBOL(xfrm6_tunnel_register);
+
+int xfrm6_tunnel_deregister(struct xfrm6_tunnel *handler)
+{
+	struct xfrm6_tunnel **pprev;
+	int ret = -ENOENT;
+
+	mutex_lock(&tunnel6_mutex);
+
+	for (pprev = &tunnel6_handlers; *pprev; pprev = &(*pprev)->next) {
+		if (*pprev == handler) {
+			*pprev = handler->next;
+			ret = 0;
+			break;
+		}
+	}
+
+	mutex_unlock(&tunnel6_mutex);
+
+	synchronize_net();
+
+	return ret;
+}
+
+EXPORT_SYMBOL(xfrm6_tunnel_deregister);
+
+static int tunnel6_rcv(struct sk_buff **pskb)
+{
+	struct sk_buff *skb = *pskb;
+	struct xfrm6_tunnel *handler;
+
+	for (handler = tunnel6_handlers; handler; handler = handler->next)
+		if (!handler->handler(skb))
+			return 0;
+
+	kfree_skb(skb);
+	return 0;
+}
+
+static void tunnel6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
+			int type, int code, int offset, __u32 info)
+{
+	struct xfrm6_tunnel *handler;
+
+	for (handler = tunnel6_handlers; handler; handler = handler->next)
+		if (!handler->err_handler(skb, opt, type, code, offset, info))
+			break;
+}
+
+static struct inet6_protocol tunnel6_protocol = {
+	.handler	= tunnel6_rcv,
+	.err_handler	= tunnel6_err,
+	.flags          = INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
+};
+
+static int __init tunnel6_init(void)
+{
+	if (inet6_add_protocol(&tunnel6_protocol, IPPROTO_IPV6)) {
+		printk(KERN_ERR "tunnel6 init(): can't add protocol\n");
+		return -EAGAIN;
+	}
+	return 0;
+}
+
+static void __exit tunnel6_fini(void)
+{
+	if (inet6_del_protocol(&tunnel6_protocol, IPPROTO_IPV6))
+		printk(KERN_ERR "tunnel6 close: can't remove protocol\n");
+}
+
+module_init(tunnel6_init);
+module_exit(tunnel6_fini);
+MODULE_LICENSE("GPL");