Re: Interesting TCP issue
- From: steve@xxxxxxxx (Steve Watt)
- Date: Tue, 2 Jan 2007 00:25:22 -0800
On Jan 2, 0:06, Steve Watt wrote:
} Subject: Re: Interesting TCP issue
} 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@xxxxxxxxxxxxxxxx:/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.
We have a winner -- setting net.inet.tcp.rfc1323=0 let the mail message
come in on the next try.
p0f's guess at the remote machine is that it's a newer Linux 2.6 box;
that doesn't seem like an interoperability problem that should've
slipped through -BETA, given how common those are...
The exchange with rfc1323 looks completely normal, with the remote end
giving windows of 5840. But it ended the conversation in a very Windows
way by sending a couple of RSTs after the FIN exchange. Or has that
brokenness now extended itself to Linux as well?
--
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...
_______________________________________________
freebsd-hackers@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@xxxxxxxxxxx"
- Follow-Ups:
- Re: Interesting TCP issue
- From: Julian Elischer
- Re: Interesting TCP issue
- Prev by Date: Re: Interesting TCP issue
- Next by Date: Re: getgroups and getgrouplist functions
- Previous by thread: Re: Interesting TCP issue
- Next by thread: Re: Interesting TCP issue
- Index(es):
Relevant Pages
|
