netdev - Re: [net v1 PATCH 4/4] net: fix bpf_xdp_adjust

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Date:   Thu, 1 Aug 2019 17:44:06 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        xdp-newbies@...r.kernel.org,
        Daniel Borkmann <borkmann@...earbox.net>,
        brandon.cazander@...tapplied.net,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: Re: [net v1 PATCH 4/4] net: fix bpf_xdp_adjust_head regression for
 generic-XDP

On Thu, 01 Aug 2019 20:00:31 +0200, Jesper Dangaard Brouer wrote:
> When generic-XDP was moved to a later processing step by commit
> 458bf2f224f0 ("net: core: support XDP generic on stacked devices.")
> a regression was introduced when using bpf_xdp_adjust_head.
> 
> The issue is that after this commit the skb->network_header is now
> changed prior to calling generic XDP and not after. Thus, if the header
> is changed by XDP (via bpf_xdp_adjust_head), then skb->network_header
> also need to be updated again.  Fix by calling skb_reset_network_header().
> 
> Fixes: 458bf2f224f0 ("net: core: support XDP generic on stacked devices.")
> Reported-by: Brandon Cazander <brandon.cazander@...tapplied.net>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>

Out of curiosity what was your conclusion regarding resetting the
transport header as well?