[IPSEC]: Get rid of ipv6_{auth,esp,comp}_hdr

This patch removes the duplicate ipv6_{auth,esp,comp}_hdr structures since
they're identical to the IPv4 versions.  Duplicating them would only create
problems for ourselves later when we need to add things like extended
sequence numbers.

I've also added transport header type conversion headers for these types
which are now used by the transforms.

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

include/net/ipcomp.h

@@ -1,14 +1,23 @@
 #ifndef _NET_IPCOMP_H
 #define _NET_IPCOMP_H
 
-#include <linux/crypto.h>
 #include <linux/types.h>
 
 #define IPCOMP_SCRATCH_SIZE     65400
 
+struct crypto_comp;
+
 struct ipcomp_data {
 	u16 threshold;
 	struct crypto_comp **tfms;
 };
 
+struct ip_comp_hdr;
+struct sk_buff;
+
+static inline struct ip_comp_hdr *ip_comp_hdr(const struct sk_buff *skb)
+{
+	return (struct ip_comp_hdr *)skb_transport_header(skb);
+}
+
 #endif