RHBA-2012:0793 - Bug Fix Advisory

Topic

Updated dhcp packages that fix several bugs and add two enhancements are now
available for Red Hat Enterprise Linux 6.

Description

The dhcp package provides software to support the Dynamic Host Configuration
Protocol (DHCP) and DHCPv6 protocol. The Dynamic Host Configuration Protocol
(DHCP) is a protocol that allows individual devices on an IP network to obtain
their own network configuration information, including an IP address, a subnet
mask, and a broadcast address.

This update fixes the following bugs:

• Previously, when dhclient was unsuccessful in obtaining or renewing an

address, it restored the resolv.conf file from backup even when there were other
dhclient processes running. Consequently, network traffic could be unnecessarily
interrupted. The bug in dhclient-script has been fixed and dhclient now restores
resolv.conf from backup only if there are no other dhclient processes running.
(BZ#656339)

• A bug caused an infinite loop in a dhcpd process when dhcpd tried to parse the

slp-service-scope option in dhcpd.conf. As a consequence, dhcpd entered an
infinite loop on startup consuming 100% of the CPU cycles. This update improves
the code and the problem no longer occurs. (BZ#747017)

• Previously, the DHCPv4 client did not check whether the address received in a

DHCPACK message was already in use. As a consequence, it was possible that after
a reboot two clients could have the same, conflicting, IP address. With this
update, the bug has been fixed and DHCPv4 client now performs duplicate address
detection (DAD) and sends a DHCPDECLINE message if the address received in
DHCPACK is already in use, as per RFC 2131. (BZ#752116)

• When dhclient is invoked with the "-1" command-line option, it should try to

get a lease once and on failure exit with status code 2. Previously, when
dhclient was invoked with the "-1" command-line option, and then issued a
DHCPDECLINE message, it continued in trying to obtain a lease. With this update,
the dhclient code has been fixed. As a result, dhclient stops trying to obtain a
lease and exits after sending DHCPDECLINE when started with the "-1" option.
(BZ#756759)

• Previously, dhclient kept sending DHCPDISCOVER messages in an infinite loop

when started with the "-timeout" option having a value of 3 or less (seconds).
With this update, the problem has been fixed and the "-timeout" option works as
expected with all values. (BZ#789719)

This update also provides the following enhancements:

• The DHCP server daemon now uses portreserve for reserving ports 647 and 847 to

prevent other programs from occupying them. (BZ#790686)

• All DHCPv6 options defined in RFC5970, except for the Boot File Parameters

Option, were implemented. This allows the DHCPv6 server to pass boot file URLs
back to IPv6-based netbooting clients (UEFI) based on the system's architecture.
(BZ#798735)

Users are advised to upgrade to these updated dhcp packages, which fix these
bugs and add these enhancements.

Solution

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
https://access.redhat.com/knowledge/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension (for IBM z Systems) 6 s390x

Fixes

• BZ - 752116 - dhclient and dhclient-script do not send arping before sending DHCPACK reply to dhcp server
• BZ - 756759 - dhclient retries on DHCPDECLINE despite -1 option
• BZ - 789719 - When the -timeout option is less than or equal to 3, dhclient will stuck in a infinite loop doing DHCP Discover
• BZ - 790686 - dhcp should be using portreserve
• BZ - 798735 - RFE: backport RFC5970 support to dhcp

CVEs

(none)

References

(none)