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SubjectRe: [PATCH] net: Reset skb to network header in neigh_hh_output
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On Wed, 2016-10-26 at 01:57 +0200, Abdelrhman Ahmed wrote:
> > What is the issue you want to fix exactly ?
> > Please describe the use case.
>
> When netfilter hook uses skb_push to add a specific header between network
> header and hardware header.
> For the first time(s) before caching hardware header, this header will be
> removed / overwritten by hardware header due to resetting to network header.
> After using the cached hardware header, this header will be kept as we do not
> reset. I think this behavior is inconsistent, so we need to reset in both cases.
>
> > Otherwise, your fix is in fact adding a critical bug.
>
> Could you explain more as it's not clear to me?
>

Maybe my wording was not good here.

What I intended to say is that the
__skb_pull(skb, skb_network_offset(skb)) might not be at the right
place.

Look at commit e1f165032c8bade3a6bdf546f8faf61fda4dd01c to find the
reason.


>
>
> ---- On Fri, 07 Oct 2016 23:10:56 +0200 Eric Dumazet <eric.dumazet@gmail.com> wrote ----
> > On Fri, 2016-10-07 at 16:14 +0200, Abdelrhman Ahmed wrote:
> > > When hardware header is added without using cached one, neigh_resolve_output
> > > and neigh_connected_output reset skb to network header before adding it.
> > > When cached one is used, neigh_hh_output does not reset the skb to network
> > > header.
> > >
> > > The fix is to reset skb to network header before adding cached hardware header
> > > to keep the behavior consistent in all cases.
> >
> > What is the issue you want to fix exactly ?
> >
> > Please describe the use case.
> >
> > I highly suggest you take a look at commit
> >
> > e1f165032c8bade3a6bdf546f8faf61fda4dd01c
> > ("net: Fix skb_under_panic oops in neigh_resolve_output")
> >
> > Otherwise, your fix is in fact adding a critical bug.
> >
> >
> >
>


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