New DHCP For Linux?

A new DHCP (define) client for Linux is set to take advantage of an expected new feature in a future Linux kernel.

The new DHCP client is being proposed by kernel developer Stefan Rompf and
will (when completed) automatically recognize when a Linux user has
disconnected from a particular DHCP server and look for a new

But the effort is not without its detractors who feel that a
new DHCP client is not necessary for Linux.

DHCP (define) is a cornerstone of Internet connectivity
assigning dynamic IP addresses to user connections.

According to Rompf,
current DHCP clients on Linux do not recognize temporary disconnections.
Such disconnections are common for notebook users that travel between
different networks or that roam different hotspots and WLANs.

Rompf argues that the disconnection
is not necessarily a limitation of the current 2.6 Linux kernel, as the
kernel itself will notify userspace of a disconnection/reconnection event.

However, a feature that is expected to debut in the 2.6.17 Linux kernel will
make it even easier to deal with disconnection/reconnection events. The most
current Linux kernel release is 2.6.15 with 2.6.16 currently at the release candidate 4 stage.

Rompf said the 2.6.17 kernel will allow userspace to influence
connection event signaling, so that a DHCP client could be notified that a
connection has terminated and the client should attempt to obtain a new IP

The problem, though, is that in order to take advantage of the new
feature, you need software that will support it, and that’s where
Rompf’s new DHCP client comes into play.

“The DHCP client is a userspace program to obtain IP configuration when
connected to a local network,” Rompf told “It won’t be
part of the kernel, but I hope for distributions to pick it up.

“There are already DHCP client packages, but they were all missing one
feature that is important for my personal work: They do not automatically
renew the configuration when I connect to a different network.”

Not everyone agrees with Rompf’s assessment.

Jean Tourrilhes, HP’s Linux Wireless Extension and the Wireless Tools
project leader, is known in the Linux community for his wireless Linux

Tourrilhes noted that Wireless Extension has supported the
Wireless Events providing users with precise information about connection
status since the 2.4.20 kernel release.

A new DHCP may also come with its own particular shortcomings.

“The traditional DHCP client has a lot of scripting features and API
features that are in use, and that will take time to duplicate in the new
client if ever they chose to do it,” Tourrilhes told
“Personally, I think that fixing the traditional client would have been a
better project.

“But, Stefan has the right to have his own opinion and motivation, and this
is always progress.”

The ISC, the group that is the lead sponsor of ISC DHCP (a popular reference
implementation of DHCP), also disagrees with the assessment that a new DHCP
client is needed for Linux.

“We don’t think it needs to be done again from scratch, and it is something
we are interested in including in future releases of DHCP,” ISC spokesperson
Laura Hendriksen said. “The one change we would like to make as we move
forward with this is changing from a polling mode to an event-driven mode.”

So far, Rompf’s effort is in the alpha stage and is in active development.

“I hope to have it in good shape when Linux kernel 2.6.17 is released,
because this kernel will allow interaction between the DHCP client and an
802.1x supplicant, so that authentication runs first, and after the success of the
IP setup,” Rompf said.

“This will increase usability quite a bit.”

Article courtesy of

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