Date: Mon, 01 Jan 2007 20:21:00 -0500 From: "David S. Madole" <david@madole.net> To: 'Steve Watt' <steve@Watt.COM>, "'hackers@freebsd.org'" <hackers@freebsd.org> Subject: RE: Interesting TCP issue Message-ID: <20070102013337.26CA513C44B@mx1.freebsd.org>
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> From Steve Watt on Monday, January 01, 2007 4:37 PM >=20 > # 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 4= 6 > <nop,nop,timestamp 2511885672 520058954> > 0x0000: 4520 004a 3260 4000 3a06 c609 d5f4 aa50 E..J2`@.:......= P > 0x0010: 425d 8582 c4e6 0019 f2bc e212 4a6b fcff B]..........Jk.= . > 0x0020: 8018 002e 9297 0000 0101 080a 95b8 5568 ..............U= h > 0x0030: 1eff 784a 4548 4c4f 2073 6861 7265 2e73 ..xJEHLO.share.= s > 0x0040: 6b79 7065 2e6e 6574 0d0a kype.net.. >=20 > 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. Are you sure the window is really that small and that window scaling was no= t negotiated at the start of the connection? The initial packets are not ca= ptured here so I can't tell. Is it possible to get a really complete capture of a session including the = initial handshake? David
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