Subject: [PATCH net] nsh: set mac len based on inner packet

From: Willem de Bruijn <[email-masked]>
Date: Wed, 11 Jul 2018 12:00:44 -0400

From: Willem de Bruijn <[email-masked]>

When pulling the NSH header in nsh_gso_segment, set the mac length
based on the encapsulated packet type.

skb_reset_mac_len computes an offset to the network header, which
here still points to the outer packet:

  >     skb_reset_network_header(skb);
  >     [...]
  >     __skb_pull(skb, nsh_len);
  >     skb_reset_mac_header(skb);    // now mac hdr starts nsh_len == 8B after net hdr
  >     skb_reset_mac_len(skb);       // mac len = net hdr - mac hdr == (u16) -8 == 65528
  >     [..]
  >     skb_mac_gso_segment(skb, ..)

Link: http://lkml.kernel.org/r/CAF=[email-masked]
Reported-by: [email-masked]
Fixes: c411ed854584 ("nsh: add GSO support")
Signed-off-by: Willem de Bruijn <[email-masked]>
---
 net/nsh/nsh.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/nsh/nsh.c b/net/nsh/nsh.c
index 9696ef96b719..1a30e165eeb4 100644
--- a/net/nsh/nsh.c
+++ b/net/nsh/nsh.c
@@ -104,7 +104,7 @@ static struct sk_buff *nsh_gso_segment(struct sk_buff *skb,
 	__skb_pull(skb, nsh_len);
 
 	skb_reset_mac_header(skb);
-	skb_reset_mac_len(skb);
+	skb->mac_len = proto == htons(ETH_P_TEB) ? ETH_HLEN : 0;
 	skb->protocol = proto;
 
 	features &= NETIF_F_SG;
-- 
2.18.0.203.gfac676dfb9-goog