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Date: Sun, 16 Aug 2020 15:29:37 -0700 (PDT) From: David Miller <davem@...emloft.net> To: Jason@...c4.com Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, brouer@...hat.com Subject: Re: [PATCH net] net: xdp: pull ethernet header off packet after computing skb->protocol From: "Jason A. Donenfeld" <Jason@...c4.com> Date: Sat, 15 Aug 2020 09:29:30 +0200 > When an XDP program changes the ethernet header protocol field, > eth_type_trans is used to recalculate skb->protocol. In order for > eth_type_trans to work correctly, the ethernet header must actually be > part of the skb data segment, so the code first pushes that onto the > head of the skb. However, it subsequently forgets to pull it back off, > making the behavior of the passed-on packet inconsistent between the > protocol modifying case and the static protocol case. This patch fixes > the issue by simply pulling the ethernet header back off of the skb > head. > > Fixes: 297249569932 ("net: fix generic XDP to handle if eth header was mangled") > Cc: Jesper Dangaard Brouer <brouer@...hat.com> > Cc: David S. Miller <davem@...emloft.net> > Signed-off-by: Jason A. Donenfeld <Jason@...c4.com> Applied and queued up for -stable, thanks. Jesper, I wonder how your original patch was tested because it pushes a packet with skb->data pointing at the ethernet header into the stack. That should be popped at this point as per this fix here. Thanks.
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