Bug 230770 - Mutiple DNS queries use same DNS transaction ID
Mutiple DNS queries use same DNS transaction ID
Product: Red Hat Enterprise Linux 4
Classification: Red Hat
Component: nss_ldap (Show other bugs)
i386 Linux
medium Severity medium
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Assigned To: Nalin Dahyabhai
BaseOS QE Security Team
Depends On:
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Reported: 2007-03-02 14:29 EST by Mike Whitney
Modified: 2012-06-20 12:12 EDT (History)
2 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2012-06-20 12:12:12 EDT
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RHEL 7.3 requirements from Atomic Host:
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Attachments (Terms of Use)
packet capture showing duplicate DNS transaction ID numbers on repeated queries (253.06 KB, application/octet-stream)
2007-03-02 14:29 EST, Mike Whitney
no flags Details

  None (edit)
Description Mike Whitney 2007-03-02 14:29:22 EST
Description of problem:
Redhat clients make multiple DNS requests under the same Transaction ID number.
 This is agains RFCs and our Cisco firewall is stomping on the second request if
the initial query was already responded too. 

Version-Release number of selected component (if applicable):
RHEL4 update 4

How reproducible:
We use PAM and nss_ldap for LDAP based authentication.  If nscd is not running
(we have found it to be unreliable in the past), then the login process triggers
multiple queries for the IP address of our LDAP servers.  These queries use
duplicate transaction IDs, causing them to be dropped by our firewall.  The
duplicate transaction ID bug should be visible without a firewall, but the login
delays and timeouts caused by dropped queries would not.

Steps to Reproduce:
1.Configure client to use PAM and nss_ldap
2.stop nscd
3.start packet capture of DNS traffic
4.log in to client
5.stop packet capture 
Actual results:
(see attache packet capture)
Packet 307 uses a transaction id of 0x5bd4, and packet 308 is the response with
the same transaction id.  Then in packet 361, there is another request with the
same transaction id of 0x5bd4, which the firewall denies since the response was
issued in packet 308.  Once the client times out (~5sec) it repeates the query
to the alternate DNS host.

Expected results:
Subsequent DNS queries should use different transaction IDs.

Additional info:
Comment 1 Mike Whitney 2007-03-02 14:29:22 EST
Created attachment 149140 [details]
packet capture showing duplicate DNS transaction ID numbers on repeated queries
Comment 3 Jiri Pallich 2012-06-20 12:12:12 EDT
Thank you for submitting this issue for consideration in Red Hat Enterprise Linux. The release for which you requested us to review is now End of Life. 
Please See https://access.redhat.com/support/policy/updates/errata/

If you would like Red Hat to re-consider your feature request for an active release, please re-open the request via appropriate support channels and provide additional supporting details about the importance of this issue.

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