Fix accept_filter for GNU/Linux

[Poul-Henning Kamp]

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In message <CAJV_h0agSG7HfqsmHoWVuvzcstQtSpM89HPWw6PteUES_PNxLQ at mail.gmail.com>
, Federico Schwindt writes:

>For a chance to get this included in 4.1 (although it'd be off by default)
>can you test the attached patch with real traffic and report back?
>
>Please note this patch has the accept_filter feature enabled so there is no
>need to do anything besides ensuring it works as expected.

Let me clarify my stance:

I have no objection to adding this as "default disabled" in 4.1-R, as
long as we have tangible evidence that enabling it actually works on
at least some Linux distros.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.