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Date:      13 Aug 2001 14:36:30 +0200
From:      drt@un.bewaff.net (Doobee R. Tzeck)
To:        freebsd-questions@freebsd.org
Subject:   FreeBSD Host which can't communicate with itself.
Message-ID:  <87zo94t9v5.fsf@c0re.rc23.cx>

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I have 4.2 host which can't sucessfully connect to itself via
TCP. ICMP and UDP works.

So I can send and recive data to all local interfaces (lo0 and
xl0) if it is UDP or ICMP. But it I try to establish an TCP
connection, it times out. 

Connectivity to other hosts works great.

Any hints into what I should look to nail the Problem?

drt



Demonstration of the Probelm:

drt@c0re:~> ping -c 1 localhost
PING localhost (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: icmp_seq=0 ttl=255 time=0.194 ms

--- localhost ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.194/0.194/0.194/0.000 ms

[other console]
drt@c0re:~> nc -l -u -p 1234

drt@c0re:~> sudo /usr/local/sbin/lsof -i -n | grep 1234
Password:
nc        52643     drt    3u  IPv4 0xc9e5dd80      0t0    UDP  *:1234

drt@c0re:~> nc -u localhost 1234
hallo
^C punt!

[other console]
hallo

drt@c0re:~> nc -l -p 12345 localhost
[waits forever, or at least several dozend minutes]

[other console]
drt@c0re:~/rt-2-0-4> sudo /usr/local/sbin/lsof -i -n |grep 1234
nc        55873     drt    3u  IPv4 0xca2dbb60      0t0    TCP *:12345 (LISTEN)
nc        55888    root    3u  IPv4 0xca2e20c0      0t0    TCP 127.0.0.1:3158->127.0.0.1:1234 (SYN_SENT)


ktrace of the connecting nc shows:
55888 nc       CALL  connect(0x3,0x807c080,0x10)
55888 nc       RET   connect -1 errno 60 Operation timed out


drt@c0re:~> sudo /sbin/ipfw show
Password:
65535 54044251 5641476290 allow ip from any to any
## Dynamic rules:
00000 0 0 (T 0, # 0) ty 0 ip, 0.0.0.0 0 <-> 0.0.0.0 0



FreeBSD c0re.rc23.cx 4.2-STABLE FreeBSD 4.2-STABLE #0: Fri Feb 23
00:35:37 CET 2001     root@c0re.rc23.cx:/usr/src/sys/compile/C0RE i386

drt@c0re:~> sudo /sbin/sysctl -a |grep net.inet.tcp
net.inet.tcp.rfc1323: 0
net.inet.tcp.rfc1644: 0
net.inet.tcp.mssdflt: 512
net.inet.tcp.keepidle: 7200000
net.inet.tcp.keepintvl: 75000
net.inet.tcp.sendspace: 16384
net.inet.tcp.recvspace: 16384
net.inet.tcp.keepinit: 75000
net.inet.tcp.delacktime: 100
net.inet.tcp.v6mssdflt: 1024
net.inet.tcp.log_in_vain: 1
net.inet.tcp.blackhole: 0
net.inet.tcp.delayed_ack: 1
net.inet.tcp.tcp_lq_overflow: 1
net.inet.tcp.restrict_rst: 1
net.inet.tcp.path_mtu_discovery: 0
net.inet.tcp.slowstart_flightsize: 1
net.inet.tcp.local_slowstart_flightsize: 65535
net.inet.tcp.tcbhashsize: 512
net.inet.tcp.pcbcount: 27
net.inet.tcp.msl: 30000
net.inet.tcp.always_keepalive: 1

-- 
Aber wenn man es genau nimmt, ist UNIX auch nur ein verherrlichtes Telespiel.
Niemand arbeitet auf UNIX-Systemen an ernsthaften Dingen - man schickt kleine
Witzchen ueber das USENET rund um die Welt oder schreibt ein neues Adventure-
Spiel oder Forschungsberichte.                       http://koeln.ccc.de/~drt/

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