[PATCH net-next] gre_offload: simplify GRE header length calculation in gre_gso_segment()

[PATCH net-next] gre_offload: simplify GRE header length calculation in gre_gso_segment()

[Neal Cardwell]

Simplify the GRE header length calculation in gre_gso_segment().
Switch to an approach that is simpler, faster, and more general. The
new approach will continue to be correct even if we add support for
the optional variable-length routing info that may be present in a GRE
header.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: H.K. Jerry Chu <hkchu@google.com>
Cc: Pravin B Shelar <pshelar@nicira.com>
---
 net/ipv4/gre_offload.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index 746a7b1..f6604b6 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -26,7 +26,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 {
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	netdev_features_t enc_features;
-	int ghl = GRE_HEADER_SECTION;
+	int ghl;
 	struct gre_base_hdr *greh;
 	u16 mac_offset = skb->mac_header;
 	int mac_len = skb->mac_len;
@@ -49,15 +49,11 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 
 	greh = (struct gre_base_hdr *)skb_transport_header(skb);
 
-	if (greh->flags & GRE_KEY)
-		ghl += GRE_HEADER_SECTION;
-	if (greh->flags & GRE_SEQ)
-		ghl += GRE_HEADER_SECTION;
-	if (greh->flags & GRE_CSUM) {
-		ghl += GRE_HEADER_SECTION;
-		csum = true;
-	} else
-		csum = false;
+	ghl = skb_inner_network_header(skb) - skb_transport_header(skb);
+	if (unlikely(ghl < sizeof(*greh)))
+		goto out;
+
+	csum = !!(greh->flags & GRE_CSUM);
 
 	if (unlikely(!pskb_may_pull(skb, ghl)))
 		goto out;
-- 
1.8.5.1

Re: [PATCH net-next] gre_offload: simplify GRE header length calculation in gre_gso_segment()

[Eric Dumazet]

On Thu, 2014-01-09 at 20:47 -0500, Neal Cardwell wrote:
> Simplify the GRE header length calculation in gre_gso_segment().
> Switch to an approach that is simpler, faster, and more general. The
> new approach will continue to be correct even if we add support for
> the optional variable-length routing info that may be present in a GRE
> header.
> 
> Signed-off-by: Neal Cardwell <ncardwell@google.com>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: H.K. Jerry Chu <hkchu@google.com>
> Cc: Pravin B Shelar <pshelar@nicira.com>
> ---

Acked-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH net-next] gre_offload: simplify GRE header length calculation in gre_gso_segment()

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 09 Jan 2014 18:09:18 -0800

> On Thu, 2014-01-09 at 20:47 -0500, Neal Cardwell wrote:
>> Simplify the GRE header length calculation in gre_gso_segment().
>> Switch to an approach that is simpler, faster, and more general. The
>> new approach will continue to be correct even if we add support for
>> the optional variable-length routing info that may be present in a GRE
>> header.
>> 
>> Signed-off-by: Neal Cardwell <ncardwell@google.com>
>> Cc: Eric Dumazet <edumazet@google.com>
>> Cc: H.K. Jerry Chu <hkchu@google.com>
>> Cc: Pravin B Shelar <pshelar@nicira.com>
>> ---
> 
> Acked-by: Eric Dumazet <edumazet@google.com>

Applied, thank you.