From b884b1a46f205d56e33c0391c1d04644d846f41e Mon Sep 17 00:00:00 2001 From: Neal Cardwell Date: Thu, 9 Jan 2014 20:47:17 -0500 Subject: [PATCH] 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 Cc: Eric Dumazet Cc: H.K. Jerry Chu Cc: Pravin B Shelar Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- 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 31da9f512583..29512e3e7e7c 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;