From owner-freebsd-net@freebsd.org  Fri Mar 16 10:01:03 2018
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Date: Fri, 16 Mar 2018 11:00:54 +0100 (CET)
Message-Id: <20180316.110054.74682026.sthaug@nethelp.no>
To: melifaro@ipfw.ru
Cc: freebsd-net@freebsd.org
Subject: Re: Does FreeBSD do proactive ARP refresh?
From: sthaug@nethelp.no
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References: <20180315.210552.74686746.sthaug@nethelp.no>
 <8530131521193098@web19g.yandex.ru>
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> > I have a reproducible problem on 11.1-STABLE where, during a longterm
> > iperf3 session, some packets are lost every time ARP is refreshed (every
> > net.link.ether.inet.max_age seconds). Checking with tcpdump, I can
> > indeed see that the packet loss is happening as the hosts are doing
> > ARP request/reply.
> I'll take a look. Indeed, the intended behaviour is to proactively refresh the record.
> Is the situation the same with forwarding and locally-originated traffic?
> With local TCP socket inpcb route caching might come into play. 

My testing is with locally-originated UDP traffic (iperf3 -u). Haven't
tested what happens if the box is forwarding the traffic - however, I
believe TCP socket inpcb route caching should not be relevant for the
UDP traffic? (But there is also a TCP transaction between the iperf3
sender and the iperf3 receiver at the *start* of the iperf3 session.)

In any case, I will also test what happens if the box is forwarding
the traffic.

Steinar Haug, Nethelp consulting, sthaug@nethelp.no