[IPCOMP6]: Exclude IPCOMP header from props.header_len

Now that the IPv4 encap stuff is out of the way, I'll be sending you
the IPv6 versions.

Here is the one to remove the unnecessary extra space reserved for
IPCOMP.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Yoshifuji Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@redhat.com>

net/ipv6/ipcomp6.c

@@ -123,7 +123,7 @@ static int ipcomp6_output(struct sk_buff **pskb)
 	int err;
 	struct dst_entry *dst = (*pskb)->dst;
 	struct xfrm_state *x = dst->xfrm;
-	struct ipv6hdr *tmp_iph = NULL, *iph, *top_iph;
+	struct ipv6hdr *iph, *top_iph;
 	int hdr_len = 0;
 	struct ipv6_comp_hdr *ipch;
 	struct ipcomp_data *ipcd = x->data;
@@ -193,19 +193,11 @@ static int ipcomp6_output(struct sk_buff **pskb)
 	if ((dlen + sizeof(struct ipv6_comp_hdr)) >= plen) {
 		goto out_ok;
 	}
-	memcpy(start, scratch, dlen);
-	pskb_trim(*pskb, hdr_len+dlen);
+	memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
+	pskb_trim(*pskb, hdr_len + dlen + sizeof(struct ip_comp_hdr));
 
 	/* insert ipcomp header and replace datagram */
-	tmp_iph = kmalloc(hdr_len, GFP_ATOMIC);
-	if (!tmp_iph) {
-		err = -ENOMEM;
-		goto error;
-	}
-	memcpy(tmp_iph, (*pskb)->nh.raw, hdr_len);
-	top_iph = (struct ipv6hdr*)skb_push(*pskb, sizeof(struct ipv6_comp_hdr));
-	memcpy(top_iph, tmp_iph, hdr_len);
-	kfree(tmp_iph);
+	top_iph = (*pskb)->nh.ipv6h;
 
 	if (x->props.mode && (x->props.flags & XFRM_STATE_NOECN))
 		IP6_ECN_clear(top_iph);
@@ -358,7 +350,7 @@ static int ipcomp6_init_state(struct xfrm_state *x, void *args)
 		goto error;
 
 	memset(ipcd, 0, sizeof(*ipcd));
-	x->props.header_len = sizeof(struct ipv6_comp_hdr);
+	x->props.header_len = 0;
 	if (x->props.mode)
 		x->props.header_len += sizeof(struct ipv6hdr);