From: Neal Cardwell <ncardwell@google.com>
Date: Fri, 10 Jan 2014 01:47:17 +0000 (-0500)
Subject: gre_offload: simplify GRE header length calculation in gre_gso_segment()
X-Git-Tag: v3.14-rc1~94^2~218
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b884b1a46f205d56e33c0391c1d04644d846f41e;p=profile%2Fcommon%2Fkernel-common.git

gre_offload: simplify GRE header length calculation in gre_gso_segment()

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index 31da9f5..29512e3 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;