netdev - Re: TPACKET_V3 timeout bug?

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Date:   Sat, 15 Apr 2017 19:41:46 -0700
From:   Guy Harris <guy@...m.mit.edu>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Sowmini Varadhan <sowmini.varadhan@...cle.com>,
        netdev <netdev@...r.kernel.org>,
        tcpdump-workers@...ts.tcpdump.org
Subject: Re: TPACKET_V3 timeout bug?

On Apr 15, 2017, at 7:10 PM, Andrew Lunn <andrew@...n.ch> wrote:

> Do you think this is a kernel problem, libpcap problem, or an
> application problem?

An application problem.  See my response on netdev; the timeout (which is provided by the kernel's capture mechanism, in most cases) is to make sure packets don't stay stuck in the kernel's packet buffer for an indefinite period of time, it's *not* to make sure a thread capturing packets doesn't stay blocked for an indefinite period of time.  Whether the timer goes off even if no packets have arrived is platform-dependent; code capturing packets should neither depend on it doing so or on it not doing so.