Date: Fri, 16 Mar 2018 12:27:20 +0100 (CET) From: sthaug@nethelp.no To: Alexander V. Chernikov <melifaro@ipfw.ru> Cc: freebsd-net@freebsd.org Subject: Re: Does FreeBSD do proactive ARP refresh? Message-ID: <20180316.122720.71152047.sthaug@nethelp.no> In-Reply-To: <20180316.110054.74682026.sthaug@nethelp.no> References: <20180315.210552.74686746.sthaug@nethelp.no> <8530131521193098@web19g.yandex.ru> <20180316.110054.74682026.sthaug@nethelp.no>
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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. And thank you for that suggestion! The packet loss during ARP refresh (of the destination address connected to the output interface) does *not* happen when the box is forwarding! It only happens with locally generated traffic. Steinar Haug, Nethelp consulting, sthaug@nethelp.no
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