Bug 718996

Summary: ssh tries only the first nameserver in resolv.conf
Product: Red Hat Enterprise Linux 6 Reporter: Marko Myllynen <myllynen>
Component: glibcAssignee: Andreas Schwab <schwab>
Status: CLOSED NOTABUG QA Contact: qe-baseos-tools-bugs
Severity: low Docs Contact:
Priority: low    
Version: 6.1CC: fweimer, mfranc
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
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Clone Of: Environment:
Last Closed: 2011-07-13 06:47:18 UTC Type: ---
Regression: --- Mount Type: ---
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Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:

Description Marko Myllynen 2011-07-05 11:55:29 UTC 
Description of problem:
ssh(1) seems to try only the first nameserver in /etc/resolv.conf:

localhost:~> rpm -V openssh-clients
localhost:~> host target.example.com
target.example.com has address 192.168.1.1
localhost:~> ssh -vvv target.example.com
OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
ssh: Could not resolve hostname target.example.com: Name or service not known
localhost:~> cat /etc/resolv.conf
nameserver 192.168.168.254
nameserver 192.168.1.254
localhost:~> sudo vi /etc/resolv.conf
localhost:~> cat /etc/resolv.conf
nameserver 192.168.1.254
nameserver 192.168.168.254
localhost:~> host target.example.com
target.example.com has address 192.168.1.1
localhost:~> ssh -vvv target.example.com
OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to target.example.com [192.168.1.1] port 22.
...

Version-Release number of selected component (if applicable):
openssh-clients-5.3p1-52.el6_1.2.x86_64
Comment 2 Jan F. Chadima 2011-07-11 10:48:34 UTC 
This bug may be caused by the compatible implementation of getrrsetbyname. I will investigate it.
Comment 3 Jan F. Chadima 2011-07-12 21:58:27 UTC 
cannot reproduce with "dead" 1.st nameserver. There may be problem when 1.st nameserver responds that host do not exist. But this is resolver issue.
Can you verify (by tcpdump, wireshark or some similar tool) the DNS responses please.
Comment 4 Marko Myllynen 2011-07-13 05:19:49 UTC 
Yes, in my testing the first nameserver was not dead but the target system was unknown to it (the second nameserver had been set up for a test network while the first one was an organization wide nameserver).
Comment 5 Jan F. Chadima 2011-07-13 05:21:44 UTC 
redirecting to glibc
Comment 6 Andreas Schwab 2011-07-13 06:47:18 UTC 
This is the correct behaviour.
Comment 7 Marko Myllynen 2011-07-13 08:27:22 UTC 
Right, but since ssh and host commands behaved differently I was assuming an issue.