netdev - Re: Kernel UDP behavior with missing destinations

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Message-ID: <CABUuw67crf5yb0G_KRR94WLBP8YYLgABBgv1SFW0SvKB_ntK4w@mail.gmail.com>
Date:   Thu, 16 May 2019 12:32:35 -0400
From:   Adam Urban <adam.urban@...leguru.org>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: Kernel UDP behavior with missing destinations

Eric, thanks. Increasing wmem_default from 229376 to 2293760 indeed
makes the issue go away on my test bench. What's a good way to
determine the optimal value here? I assume this is in bytes and needs
to be large enough so that the SO_SNDBUF doesn't fill up before the
kernel drops the packets. How often does that happen?

On Thu, May 16, 2019 at 12:14 PM Eric Dumazet <eric.dumazet@...il.com> wrote:
>
>
>
> On 5/16/19 9:05 AM, Eric Dumazet wrote:
>
> > We probably should add a ttl on arp queues.
> >
> > neigh_probe() could do that quite easily.
> >
>
> Adam, all you need to do is to increase UDP socket sndbuf.
>
> Either by increasing /proc/sys/net/core/wmem_default
>
> or using setsockopt( ... SO_SNDBUF ... )
>