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New DHCP For Linux?

A new DHCP 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 connection.

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

DHCP 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 address.

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 internetnews.com. "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 efforts.

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 internetnews.com. "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."