Date: Sat, 14 May 2011 17:52:25 +0300 From: Mikolaj Golub <trociny@freebsd.org> To: Chuck Swiger <cswiger@mac.com> Cc: freebsd-net@freebsd.org, Ivan Voras <ivoras@freebsd.org>, John Baldwin <jhb@FreeBSD.org> Subject: Re: Spurious ACKs, ICMP unreachable? Message-ID: <86zkmpl4gm.fsf@kopusha.home.net> In-Reply-To: <5BD73B66-9A84-4640-A43F-4970BDC584BA@mac.com> (Chuck Swiger's message of "Fri, 13 May 2011 14:38:34 -0700") References: <iqk323$f8e$1@dough.gmane.org> <5BD73B66-9A84-4640-A43F-4970BDC584BA@mac.com>
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On Fri, 13 May 2011 14:38:34 -0700 Chuck Swiger wrote: CS> On May 13, 2011, at 1:07 PM, Ivan Voras wrote: >> I'm seeing an an unusual problem at a remote machine; this machine is >> the FreeBSD server, and the client is a probably Windows machine (but I >> don't know the details yet). Something happens which causes FreeBSD to >> send ACKs to the client, and the client to send ICMP unreachable >> messages to the server. It is most likely a configuration error at the >> remote site but I have no idea how to verify this. CS> Let's look at just one connection: CS> 18:56:02.711942 IP server.http > client.4732: Flags [.], ack 2110905191, win 0, length 0 CS> 18:56:02.713155 IP server.http > client.4732: Flags [.], ack 1, win 65535, length 0 CS> The packet is FreeBSD webserver sending ACKs with zero window size; CS> that's a sign of congestion that the client should not be sending more CS> data and instead doing periodic window probes until the local box opens CS> the window again. The next packet on the same connection then ACK's CS> something outside of the window with a 64K window size. That's wrong; CS> the other side probably sends an RST and the ICMP error. If you have TSO CS> enabled, try turning it off. Might be this the thing that jhb@ was fixing in r221346? -- Mikolaj Golub
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