[PATCH net v2 2/2] udp_offload: Set encapsulation before inner completes.

From: Jarno Rajahalme
Date: Mon May 02 2016 - 16:41:00 EST

UDP tunnel segmentation code relies on the inner offsets being set for
an UDP tunnel GSO packet, but the inner *_complete() functions will
set the inner offsets only if 'encapsulation' is set before calling
them. Currently, udp_gro_complete() sets 'encapsulation' only after
the inner *_complete() functions are done. This causes the inner
offsets having invalid values after udp_gro_complete() returns, which
in turn will make it impossible to properly segment the packet in case
it needs to be forwarded, which would be visible to the user either as
invalid packets being sent or as packet loss.

This patch fixes this by setting skb's 'encapsulation' before calling
into the inner complete functions, and by removing the setting of the
inner_mac_header in udp_gro_complete(). The inner complete now
functions set the inner_mac_header, so it need not be done here.
Furthermore, it was wrongly set to the beginning of the UDP tunnel
header rather than the inner MAC header.

Signed-off-by: Jarno Rajahalme <jarno@xxxxxxx>
net/ipv4/udp_offload.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 0ed2daf..e330c0e 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -399,6 +399,11 @@ int udp_gro_complete(struct sk_buff *skb, int nhoff)

uh->len = newlen;

+ /* Set encapsulation before calling into inner gro_complete() functions
+ * to make them set up the inner offsets.
+ */
+ skb->encapsulation = 1;

uo_priv = rcu_dereference(udp_offload_base);
@@ -421,9 +426,6 @@ int udp_gro_complete(struct sk_buff *skb, int nhoff)
if (skb->remcsum_offload)
skb_shinfo(skb)->gso_type |= SKB_GSO_TUNNEL_REMCSUM;

- skb->encapsulation = 1;
- skb_set_inner_mac_header(skb, nhoff + sizeof(struct udphdr));
return err;