Date: Tue, 2 Jan 2007 00:06:45 -0800 From: steve@Watt.COM (Steve Watt) To: Julian Elischer <julian@elischer.org> Cc: hackers@freebsd.org Subject: Re: Interesting TCP issue Message-ID: <200701020806.l0286jjg034037@wattres.watt.com> In-Reply-To: Julian Elischer <julian@elischer.org> "Re: Interesting TCP issue" (Jan 1, 23:56)
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On Jan 1, 23:56, Julian Elischer wrote: } Subject: Re: Interesting TCP issue } Steve Watt wrote: } > One of my users is having trouble receiving mail from Skype. So, } > after some sniffing, I discovered this: } > } > # tcpdump -vv -s 1500 -i dc0 -X net 213.244.128.0/18 } > tcpdump: lestening on dc0, link-type EN10MB (Ethernet), capture size 1500 bytes } > 13:18:13.607493 IP (tos 0x20, ttl 58, id 12896, offset 0, flags [DF], proto: TCP (6), length: 74) share.skype.net.50406 > wattres.watt.com.smtp: P, cksum 0x9297 (correct), 4072464914:4072464936(22) ack 1248591103 win 46 <nop,nop,timestamp 2511885672 520058954> [ sneck ] } > } > And no responses from my system. } > } > Interesting. I presume it has something to do with the } > idiotically small window the remote server is advertising. So I } > set net.inet.tcp.minmss down to 46, and that resulted in a RST } > being spit back to skype's server when its retransmit happened. } > [...] } } turn off window scaling (I forget the sysctl) and see if that helps } It's broken in some versions of freeBSD at least. Duh, should've mentioned the version: FreeBSD wattres.Watt.COM 6.2-PRERELEASE FreeBSD 6.2-PRERELEASE #6: Tue Dec 26 11:46:36 PST 2006 root@wattres.Watt.COM:/usr/obj/usr/src/sys/WATTRES i386 I did the cvsup just before the build time above. I just turned off net.inet.tcp.rfc1323; we'll see if that helps on the next polling attempt by skype's server. -- Steve Watt KD6GGD PP-ASEL-IA ICBM: 121W 56' 57.5" / 37N 20' 15.3" Internet: steve @ Watt.COM Whois: SW32-ARIN Free time? There's no such thing. It just comes in varying prices...
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