[Cake] [PATCH net v2] gso_segment: Reset skb->mac_len after modifying network header

[David Miller]

From: Toke Høiland-Jørgensen <toke at toke.dk>
Date: Thu, 13 Sep 2018 16:43:07 +0200

> When splitting a GSO segment that consists of encapsulated packets, the
> skb->mac_len of the segments can end up being set wrong, causing packet
> drops in particular when using act_mirred and ifb interfaces in
> combination with a qdisc that splits GSO packets.
> 
> This happens because at the time skb_segment() is called, network_header
> will point to the inner header, throwing off the calculation in
> skb_reset_mac_len(). The network_header is subsequently adjust by the
> outer IP gso_segment handlers, but they don't set the mac_len.
> 
> Fix this by adding skb_reset_mac_len() calls to both the IPv4 and IPv6
> gso_segment handlers, after they modify the network_header.
> 
> Many thanks to Eric Dumazet for his help in identifying the cause of
> the bug.
> 
> Acked-by: Dave Taht <dave.taht at gmail.com>
> Reviewed-by: Eric Dumazet <edumazet at google.com>
> Signed-off-by: Toke Høiland-Jørgensen <toke at toke.dk>
> ---
> v2:
>   - Properly credit Eric for his help
>   - Add review and ack tags

Applied and queued up for -stable, thanks.