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 @@
{
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 @@
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;