Synopsis

dhcp bug fix and enhancement update

Type/Severity

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 Dynamic Host Configuration Protocol (DHCP) is a protocol that allows
individual devices on an IP network to get their own network configuration
information, including an IP address, a subnet mask, and a broadcast address.
DHCPv6 is the DHCP protocol that supports IPv6 networks.

This update fixes the following bugs:

• 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,
these virtual interfaces for some clients could have been removed over time.
With this update, the dhclient utility uses the Process Identifier (PID) for
seeding the random number generator, which fixes the bug. (BZ#694798)

• If a system was rebooted while a network switch was inoperative, the network

connection would recover successfully. However, it was no longer configured to
use DHCP even if the dhclient utility had been running in persistent mode. With
this update, the dhclient-script file has been modified to refresh the ARP
(Address Resolution Protocol) table and the routing table instead of bringing
the interface down, which fixes the bug. (BZ#694799)

• If the system included network interfaces with no hardware address, the dhcpd

scan could have experienced a segmentation fault when scanning such an
interface. As a consequence, the dhcpd daemon unexpectedly terminated. To
prevent this issue, dhcpd now tests a pointer which represents the hardware
address of the interface for the NULL value. The dhcp daemon no longer crashes.
(BZ#731990)

• Previously, all source files were compiled with the "-fpie" or "fPIE" flag. As

a consequence, the libraries used by dhcp could not have been used to build Perl
modules. To fix this problem, all respective dhcp Makefiles have been modified
to compile libraries with the "-fpic" or "-fPIC" flag. The libraries used by
dhcp are now built without the previous restrictions. (BZ#736999)

• Previously, both dhcp and dhclient packages included the dhcp-options(5) and

dhcp-eval(5) man pages. As a consequence, a conflict could have occurred when
any of these man pages were updated, because dhcp and dhclient packages could
have been upgraded separately. To prevent the problem from occurring in future
updates, shared files of dhcp and dhclient packages have been moved to the
dhcp-common package that is required by both dhcp and dhclient as a dependency.
(BZ#736194)

This update also provides the following enhancements:

• A feature has been backported from dhcp version 4.2.0. This feature allows the

DHCPv6 server to be configured to identify DHCPv6 clients in accordance with
their link-layer address and their network hardware type. With this update, it
is now possible to define a static IPv6 address for the DHCPv6 client with a
known link-layer address. (BZ#706974)

• Previously, the dhcpd daemon ran as root. With this update, new "-user" and

"-group" options can be used with dhcpd. These options allow dhcpd to change the
effective user and group ID after it starts. The dhcpd and dhcpd6 services now
run the dhcpd daemon with the "-user dhcpd -group dhcpd" parameters, which means
that the dhcpd daemon runs as the dhcpd user and group instead root. (BZ#693381)

Users are advised to upgrade to these updated dhcp packages, which fixes 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/kb/docs/DOC-11259

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 Server - Extended Life Cycle Support 6 i386
• 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 (for IBM z Systems) 6 s390x

Fixes

• BZ - 693381 - dhcpd running as root
• BZ - 694798 - Multiple dhclients can steal each others' DHCPOFFERs
• BZ - 694799 - No IP connectivity with DHCP when Link was down on boot
• BZ - 731990 - dhcpd can segfault when scanning TUN interface during start
• BZ - 736194 - Upgrading dhcp, dhclient separately causes rpm file conflicts
• BZ - 736999 - dhcp's libdhcpctl libdst libomapi libraries need rebuilding with -fPIC

CVEs

(none)

References

(none)