[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>
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 93153d1..66eb496 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -60,7 +60,7 @@
 
 	skb_push(skb, -skb_network_offset(skb));
 	top_iph = ip_hdr(skb);
-	esph = (struct ip_esp_hdr *)skb_transport_header(skb);
+	esph = ip_esp_hdr(skb);
 	top_iph->tot_len = htons(skb->len + alen);
 	*(skb_tail_pointer(trailer) - 1) = *skb_mac_header(skb);
 	*skb_mac_header(skb) = IPPROTO_ESP;
@@ -157,7 +157,7 @@
 	struct sk_buff *trailer;
 	int blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
 	int alen = esp->auth.icv_trunc_len;
-	int elen = skb->len - sizeof(struct ip_esp_hdr) - esp->conf.ivlen - alen;
+	int elen = skb->len - sizeof(*esph) - esp->conf.ivlen - alen;
 	int nfrags;
 	int ihl;
 	u8 nexthdr[2];
@@ -165,7 +165,7 @@
 	int padlen;
 	int err;
 
-	if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
+	if (!pskb_may_pull(skb, sizeof(*esph)))
 		goto out;
 
 	if (elen <= 0 || (elen & (blksize-1)))
@@ -193,7 +193,7 @@
 
 	skb->ip_summed = CHECKSUM_NONE;
 
-	esph = (struct ip_esp_hdr*)skb->data;
+	esph = (struct ip_esp_hdr *)skb->data;
 
 	/* Get ivec. This can be wrong, check against another impls. */
 	if (esp->conf.ivlen)
@@ -206,7 +206,7 @@
 		if (!sg)
 			goto out;
 	}
-	skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
+	skb_to_sgvec(skb, sg, sizeof(*esph) + esp->conf.ivlen, elen);
 	err = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
 	if (unlikely(sg != &esp->sgbuf[0]))
 		kfree(sg);