Date: Wed, 21 Jul 2004 10:20:24 -0700 (PDT) From: Don Lewis <truckman@FreeBSD.org> To: dmp@bitfreak.org Cc: rwatson@FreeBSD.org Subject: Re: fetch hangs, part 2 Message-ID: <200407211720.i6LHKOxE045205@gw.catspoiler.org> In-Reply-To: <000001c46f11$1f53a880$132a15ac@spud>
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On 21 Jul, Darren Pilgrim wrote: >> From: Robert Watson [mailto:rwatson@freebsd.org] >> >> >> On Tue, 20 Jul 2004, Darren Pilgrim wrote: >> >> > I've been having the same (or a similar problem). Fetching the distfile >> > for a port will hang. I poked some more at this and found that all the >> > sites fetch is hanging on successfully negotiate the TCP connection then >> > go dead without closing the connection. My workaround has been to edit >> > the Makefile and remove the offending site from MASTER_SITES or manually >> > fetch from ftp.freebsd.org. >> >> Could you try disabling TCP SACK > > Set net.inet.tcp.delayed_ack=0? > >> and see if things "get better"? It's one >> of the things that has changed in the TCP code recently. This could well >> be a user space fetch issue, but it would be worth trying it to see, if >> only to rule it out. > > It didn't change. The connections still hung. Smells somewhat like a broken path MTU discovery problem. There might be a hop in the path with a smaller than expected MTU and something between there and the server that is filtering ICMP. An interesting experiment would be to see what happens if a smaller than normal MSS is requested. This would probably be easiest for someone with a PPP connection.
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