Date: Wed, 29 Mar 2000 21:20:09 -0500 (EST) From: Wes Morgan <morganw@engr.sc.edu> To: freebsd-net@freebsd.org Subject: 5.0 tcp weirdness Message-ID: <Pine.BSF.4.21.0003292107360.447-100000@volatile.by-tor.tacorp.net>
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In 5.0 since sometime last weekend, I have been experiencing some very
strange TCP problems. Complete inability to connect to some machines, poor
throughput, etc. I first noticed that my nameserver was having trouble
talking to some other nameservers, and at first thought @home was using
some very weird filtering, or maybe had set up something to require some
sort of DHCP validation (I don't bother with DHCP since my IP is virtually
static). After running dhclient, the nameserver lookups seemed to improve,
but there were still a few sites I could not connect to. Here is some data
I gathered:
tcpdump of conversation with an "unconnectable" site:
[root@volatile:/usr/home/by-tor#]: tcpdump src or dst port 110
tcpdump: listening on ed0
21:16:37.066637 ci391991-a.grnvle1.sc.home.com.1027 > mailbox.engr.sc.edu.pop3: S 1003018417:1003018417(0) win 16384 <mss 1460> (DF)
21:16:40.066444 ci391991-a.grnvle1.sc.home.com.1027 > mailbox.engr.sc.edu.pop3: S 1003018417:1003018417(0) win 16384 <mss 1460> (DF)
21:16:46.066497 ci391991-a.grnvle1.sc.home.com.1027 > mailbox.engr.sc.edu.pop3: S 1003018417:1003018417(0) win 16384 <mss 1460> (DF)
21:16:58.066660 ci391991-a.grnvle1.sc.home.com.1027 > mailbox.engr.sc.edu.pop3: S 1003018417:1003018417(0) win 16384 <mss 1460> (DF)
21:17:22.066970 ci391991-a.grnvle1.sc.home.com.1027 > mailbox.engr.sc.edu.pop3: S 1003018417:1003018417(0) win 16384 <mss 1460> (DF)
nmap "TCP SYN stealth" scan _will_ successfully communicate with the
machine (according to tcpdump). The "Stealth FIN, Xmas, or Null" scans
report that the port is filtered, and the regular connect() scan doesnt
work at all.
Booting to 4.0 solves ALL the problems.
**this is no complaint, but an offer to help find the problem**
My kernel config has INET and INET6 enabled, network card is an ed0
(Realtek 8029). Any other info is gladly provided!
--
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