[IPSEC]: Move IP length/checksum setting out of transforms

This patch moves the setting of the IP length and checksum fields out of
the transforms and into the xfrmX_output functions.  This would help future
efforts in merging the transforms themselves.

It also adds an optimisation to ipcomp due to the fact that the transport
offset is guaranteed to be zero.

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

1 files changed, 6 insertions, 13 deletions

diff --git a/net/ipv6/ipcomp6.c b/net/ipv6/ipcomp6.c
index 8f3f32faaf4c..28fc8edfdc3a 100644
--- a/net/ipv6/ipcomp6.c
+++ b/net/ipv6/ipcomp6.c
@@ -119,20 +119,15 @@ out:
 static int ipcomp6_output(struct xfrm_state *x, struct sk_buff *skb)
 {
         int err;
-        struct ipv6hdr *top_iph;
         struct ip_comp_hdr *ipch;
         struct ipcomp_data *ipcd = x->data;
         int plen, dlen;
         u8 *start, *scratch;
         struct crypto_comp *tfm;
         int cpu;
-        int hdr_len;
-
-        skb_push(skb, -skb_network_offset(skb));
-        hdr_len = skb_transport_offset(skb);
 
         /* check whether datagram len is larger than threshold */
-        if ((skb->len - hdr_len) < ipcd->threshold) {
+        if (skb->len < ipcd->threshold) {
                 goto out_ok;
         }
 
@@ -140,9 +135,9 @@ static int ipcomp6_output(struct xfrm_state *x, struct sk_buff *skb)
                 goto out_ok;
 
         /* compression */
-        plen = skb->len - hdr_len;
+        plen = skb->len;
         dlen = IPCOMP_SCRATCH_SIZE;
-        start = skb_transport_header(skb);
+        start = skb->data;
 
         cpu = get_cpu();
         scratch = *per_cpu_ptr(ipcomp6_scratches, cpu);
@@ -155,13 +150,9 @@ static int ipcomp6_output(struct xfrm_state *x, struct sk_buff *skb)
         }
         memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
         put_cpu();
-        pskb_trim(skb, hdr_len + dlen + sizeof(struct ip_comp_hdr));
+        pskb_trim(skb, dlen + sizeof(struct ip_comp_hdr));
 
         /* insert ipcomp header and replace datagram */
-        top_iph = ipv6_hdr(skb);
-
-        top_iph->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
-
         ipch = ip_comp_hdr(skb);
         ipch->nexthdr = *skb_mac_header(skb);
         ipch->flags = 0;
@@ -169,6 +160,8 @@ static int ipcomp6_output(struct xfrm_state *x, struct sk_buff *skb)
         *skb_mac_header(skb) = IPPROTO_COMP;
 
 out_ok:
+        skb_push(skb, -skb_network_offset(skb));
+
         return 0;
 }