Date: Sat, 16 Nov 2002 21:53:31 +0100 From: Stephan Eckner <stephan-freebsd-questions@eckner.org> To: freebsd-questions@freebsd.org Subject: sshd and reverse lookups Message-ID: <20021116205331.GB2815@knuth.codeblau.de>
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Hi,
being new to Freebsd, I'm having a problem with sshd on 4.7-RELEASE:
Although my DNS-Setup is configured correctly, I get a very long delay
when connecting to the FreeBSD machine.
Here are the details:
I'm using the OpenSSH-Version that came with 4.7-RELEAS:
freebsd# ssh -V
OpenSSH_3.4p1 FreeBSD-20020702, SSH protocols 1.5/2.0, OpenSSL 0x0090607f
The machine is called freebsd.local and has the IP-Address 192.168.1.99:
freebsd# ifconfig fxp1
fxp1: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500
inet 192.168.1.99 netmask 0xffffff00 broadcast 192.168.1.255
I tried to tell sshd not to reverse-lookup IP-Adresses:
freebsd# ps afux | grep sshd
root 92 0.0 2.2 2336 1352 ?? Is 8:06PM 0:00.01 /usr/sbin/sshd -u0
freebsd# grep Reverse /etc/ssh/sshd_config
VerifyReverseMapping no
I told the resolver to use my DNS-Server on 192.168.1.1:
freebsd# cat /etc/resolv.conf
search local
nameserver 192.168.1.1
freebsd# cat /etc/host.conf
# $FreeBSD: src/etc/host.conf,v 1.6 1999/08/27 23:23:41 peter Exp $
# First try the /etc/hosts file
hosts
# Now try the nameserver next.
bind
# If you have YP/NIS configured, uncomment the next line
# nis
... which is actually working:
freebsd# nslookup 192.168.2.66
Server: mutter.local
Address: 192.168.1.1
Name: laura.wlan
Address: 192.168.2.66
Now, when I connect from laura.wlan, the ssh-connection hangs, because sshd
on freebsd.local tries to contact a nameserver ... on _freebsd.local_:
freebsd# tcpdump -n -i lo0
tcpdump: listening on lo0
20:42:31.233449 192.168.1.99.1066 > 192.168.1.99.53: 13026+ PTR? 66.2.168.192.in-addr.arpa. (43)
freebsd# lsof -n
<--snip-->
sshd 692 sshd 4u IPv4 0xc6263600 0t0 TCP 192.168.1.99:ssh->192.168.2.66:36540 (ESTABLISHED)
sshd 692 sshd 5u 0xc0b79500 file struct, ty=0x5, op=0xc0264dac
sshd 692 sshd 6u PIPE 0xc67e4ca0 16384 ->0xc67e4b60
sshd 692 sshd 7u IPv4 0xc6201ec0 0t0 UDP 192.168.1.99:instl_boots->192.168.1.99:domain
Of course there is no response, because there is no nameserver on freebsd.local.
Why is sshd doing these reverse-lookups and where does it get the idea from to
ask a nameserver on the local machine?
Stephan
PS: After upgrading my ports tree I installed first openssh-3.5 (same problem)
and then openssh-portable-3.5p1 (no problem).
--
Stephan Eckner http://www.eckner.org/
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