path: root/net/ipv4/gre_offload.c
diff options
authorAlexander Duyck <>2016-04-05 09:13:39 -0700
committerDavid S. Miller <>2016-04-07 16:56:33 -0400
commita0ca153f98db8cf25298565a09e11fe9d82846ad (patch)
tree5f7773cd6e2dbf30f3af97194a8b7d04b99fd1a0 /net/ipv4/gre_offload.c
parent0a1a37b6d62e6864a77a82e925217c720f91f963 (diff)
GRE: Disable segmentation offloads w/ CSUM and we are encapsulated via FOU
This patch fixes an issue I found in which we were dropping frames if we had enabled checksums on GRE headers that were encapsulated by either FOU or GUE. Without this patch I was barely able to get 1 Gb/s of throughput. With this patch applied I am now at least getting around 6 Gb/s. The issue is due to the fact that with FOU or GUE applied we do not provide a transport offset pointing to the GRE header, nor do we offload it in software as the GRE header is completely skipped by GSO and treated like a VXLAN or GENEVE type header. As such we need to prevent the stack from generating it and also prevent GRE from generating it via any interface we create. Fixes: c3483384ee511 ("gro: Allow tunnel stacking in the case of FOU/GUE") Signed-off-by: Alexander Duyck <> Signed-off-by: David S. Miller <>
Diffstat (limited to 'net/ipv4/gre_offload.c')
1 files changed, 8 insertions, 0 deletions
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index c47539d04b88..6a5bd4317866 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -150,6 +150,14 @@ static struct sk_buff **gre_gro_receive(struct sk_buff **head,
if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
goto out;
+ /* We can only support GRE_CSUM if we can track the location of
+ * the GRE header. In the case of FOU/GUE we cannot because the
+ * outer UDP header displaces the GRE header leaving us in a state
+ * of limbo.
+ */
+ if ((greh->flags & GRE_CSUM) && NAPI_GRO_CB(skb)->is_fou)
+ goto out;
type = greh->protocol;