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SubjectRe: [PATCH] net: Reset skb to network header in neigh_hh_output
 > 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?



---- 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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