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Bug 1177351 - dhclient: Unicast requests sent on "wrong" interface
Summary: dhclient: Unicast requests sent on "wrong" interface
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: dhcp
Version: 7.0
Hardware: All
OS: Linux
medium
medium
Target Milestone: rc
: ---
Assignee: Jiri Popelka
QA Contact: Release Test Team
URL:
Whiteboard:
: 1186727 (view as bug list)
Depends On:
Blocks: 1035038 1082754 1112660
TreeView+ depends on / blocked
 
Reported: 2014-12-26 13:26 UTC by Patrick Laimbock
Modified: 2015-11-19 08:56 UTC (History)
7 users (show)

Fixed In Version: dhcp-4.2.5-38.el7
Doc Type: Bug Fix
Doc Text:
Previously, when using the "dhclient" DHCP protocol client on a host with two network interfaces connected to the same subnet, "DHCPREQUEST" packets were only being sent to one of the interfaces. Consequently, the IP address lease of the other interface was not being renewed. With this update, "dhclient" sends "DHCPREQUEST" and "DHCPRELEASE" packets to both interfaces, even if they are on the same subnetwork.
Clone Of:
: 1297445 (view as bug list)
Environment:
Last Closed: 2015-11-19 08:56:04 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
Patch to dhclient: Unicast requests sent on "wrong" interface (2.05 KB, patch)
2014-12-26 13:26 UTC, Patrick Laimbock 		no flags Details | Diff
send unicast request/release via correct interface (2.19 KB, patch)
2015-02-03 11:51 UTC, Jiri Popelka 		no flags Details | Diff
Show Obsolete (1) View All


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHEA-2015:2251 0 normal SHIPPED_LIVE dhcp bug fix and enhancement update 2015-11-19 09:10:43 UTC

Description Patrick Laimbock 2014-12-26 13:26:43 UTC 
Created attachment 973198 [details]
Patch to dhclient: Unicast requests sent on "wrong" interface

Description of problem:
dhclient fails to renew IP addresses from the same subnet on a VM with 2 nics (eth0, eth1) configured for dhcp via network-service. The DHCPDISCOVERY stage works fine and both eth0 and eth1 will get an IP address. But while in renewing state and with similar routes on each interface, eth1 seems to send its DHCPREQUEST through the eth0 interface and renewal for eth1 fails while renewal for eth0 succeeds.

Version-Release number of selected component (if applicable):
CentOS 7 (up-to-date)
dhcp-4.2.5-27.el7.centos.2

How reproducible:
Add VM with EL7 and at least 2 nics, disable NetworkManager, enable network-service, configure nics for dhcp in ifcfg-eth{1,2}, configure dhcp server to assign an IP address to both nics from the same subnet, start VM, see initial DHCPDISCOVERY succeed for eth0 and eth1, see all subsequent renewals via DHCPREQUEST fail for eth1 (and still succeed for eth0).

Steps to Reproduce:
1. add VM with 2 nics, enable network-service + dhcp, start VM
2. after initially succesfully obtaining 2 leases wait for renewal 
3. renewal fails for eth1, succeeds for eth0

Actual results:
Renewal fails for eth1

Expected results:
Renewal succeeds for eth1

Additional info:
The problem was reported several times on the dhcp mailing list but no response from ISC (examples: https://lists.isc.org/pipermail/dhcp-users/2013-February/016398.html and https://lists.isc.org/pipermail/dhcp-users/2014-April/017835.html).

A patch to fix this issue by Guillaume Nault is referenced here:
https://community.ubnt.com/t5/EdgeMAX/WAN-dropped-DHCP-renew-fixes-it/m-p/783774

I contacted Guillaume, received the latest version of his patch and rebased it on the 4.2.5 release, added it as the latest patch in the dhcp spec file, rebuilt it, tested the new dhclient on current CentOS 7 and renewal now also succeeds for eth1.

Please let me know if you need more information.
Comment 2 Patrick Laimbock 2014-12-30 19:05:08 UTC 
The thread on the dhcp-hackers mailinglist where this issue was most recently reported: https://lists.isc.org/pipermail/dhcp-hackers/2014-December/002103.html

Nexy to Guillaume's patch, Ben Greear also has a number of patches available at: https://github.com/greearb/dhcp-ct/commits/master

Best wishes for 2015.
Comment 3 Jiri Popelka 2015-02-02 17:52:43 UTC 
*** Bug 1186727 has been marked as a duplicate of this bug. ***
Comment 4 Jiri Popelka 2015-02-03 11:51:30 UTC 
Created attachment 987511 [details]
send unicast request/release via correct interface

Slightly amended
https://community.ubnt.com/ubnt/attachments/ubnt/EdgeMAX/29126/1/bind_fb_iface_4.2.4-P2_1.patch
Comment 8 Michal Kovarik 2015-09-08 11:52:41 UTC 
Reproduced with dhclient-4.2.5-36.el7. Verified on dhcp-4.2.5-40.el7. Renewal succeeds for second NIC immediately.
Comment 10 errata-xmlrpc 2015-11-19 08:56:04 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHEA-2015-2251.html
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