Created attachment 438631 [details] example dhclient.conf Description of problem: when multiple dhclients are launched at the same time to handle multiple virtual interface on the same NIC they use the same seed to choose when "randomly" renew the lease. This may lead to one dhclient pick up a DHCPOFFER that was meant for another dhclient. In a configuration where dhcpd assigns static addresses (based for example on a certain dhcp-client-identifier) this leads to NAKs when the stealing dhclient tries to renew the "wrong" lease it picked up. After a while it gives up and the virtual interface is deconfigured. Version-Release number of selected component (if applicable): verified in 3.0.5, currently existing in all versions (no patch applied upstream by ISC) How reproducible: it's a matter of timing, but it happens fairly often Steps to Reproduce: 1. set up a dhclient.conf with multiple virtual interfaces defining different dhcp-client-identifier (example attached) 2. configure dhcpd to send static ips based on dhcp-client-identifier (example attached). using a short lease time helps reproduce the issue. 3. launch multiple dhclients on client pointing them at the various interfaces ( eth0:1, eth0:2, etc) 4. look out for NAKs in dhcpd logs and eventually to virtual interfaces disappareance on the client. Actual results: client's virtual interface disappears over time Expected results: client virtual interfaces do not disappear over time and no NAK is seen in dhcp logs Additional info: Patch for 3.0.5-Redhat is attached. Credits should go to Jeremiah Jinno <jeremiah.jinno_at_gmail.com> who discovered the root cause and proposed a patch: https://lists.isc.org/mailman/htdig/dhcp-users/2010-June/011521.html
Created attachment 438632 [details] extract from example dhcpd.conf
Created attachment 438634 [details] Patch to use PID for seeding the random number generator
This request was evaluated by Red Hat Product Management for inclusion in the current release of Red Hat Enterprise Linux. Because the affected component is not scheduled to be updated in the current release, Red Hat is unfortunately unable to address this request at this time. Red Hat invites you to ask your support representative to propose this request, if appropriate and relevant, in the next release of Red Hat Enterprise Linux.
This request was erroneously denied for the current release of Red Hat Enterprise Linux. The error has been fixed and this request has been re-proposed for the current release.
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: Previously, when multiple DHCP clients were launched at the same time to handle multiple virtual interfaces on the same network interface card (NIC), the clients used the same seed to choose when to renew their leases. Consequently, virtual interfaces for some clients could have been deconfigured over time. With this update, the dhclient utility uses the PID (Process Identifier) for seeding the random number generator, which fixes the bug.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHBA-2011-1038.html