Date: Mon, 29 Dec 2008 22:20:40 +0000 (GMT) From: Robert Watson <rwatson@FreeBSD.org> To: Yony Yossef <yonyossef.lists@gmail.com> Cc: eitans@mellanox.co.il, freebsd-net@freebsd.org, Yehonatan Yossef <yoniy@mellanox.co.il>, liranl@mellanox.co.il, yevgenyp@mellanox.co.il Subject: Re: net.inet.udp.blackhole issue Message-ID: <alpine.BSF.1.10.0812292217040.9438@fledge.watson.org> In-Reply-To: <20def4870812240600n6edbcad7k2100a0ccbe49f0dd@mail.gmail.com> References: <20def4870812240600n6edbcad7k2100a0ccbe49f0dd@mail.gmail.com>
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On Wed, 24 Dec 2008, Yony Yossef wrote:
> I'm facing lots of UDP "Connection refused" errors while running multistream
> iperf test. Analyzing it with wireshark showed several "ICMP Port
> Unreachable" problems.
>
> I've overriden it with "sysctl net.inet.udp.blackhole=1", but I'm not sure
> this is the correct thing to do, I feel like I've sweeped the problem under
> the carpet.
>
> PS - I see similar failures with TCP bidirectional iperf test, it can also
> be overriden by "sysctl net.inet.tcp.blackhole=1".
>
> My question is - can it be a NIC problem? If so, how can a driver problem
> cause an iperf UDP socket to be in a "non listening state"?
Hi Yony:
This is fairly unlikely to be a NIC problem, although anything is possible in
software. I'm not familiar with iperf, but generally speaking ICMP port
unreachable is a result of packets arriving at a closed socket;
net.inet.udp.blackhole suppresses that ICMP:
if (udp_blackhole)
goto badheadlocked;
if (badport_bandlim(BANDLIM_ICMP_UNREACH) < 0)
goto badheadlocked;
*ip = save_ip;
ip->ip_len += iphlen;
icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_PORT, 0, 0);
I think I'd suspect an application bug/feature, in which socket gets closed
and opened during execution and once in a while a datagram is delivered in
that window. Perhaps packets are being delivered with a non-trivial delay
causing them to arrive after the application has timed out waiting for it?
Robert N M Watson
Computer Laboratory
University of Cambridge
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