[systemd-devel] Cannot acquire DHCP lease

Tom Gundersen teg at jklm.no
Wed Mar 4 01:56:44 PST 2015

On Thu, Feb 26, 2015 at 7:31 PM, Jan Janssen <medhefgo at web.de> wrote:
> Hi,
> since commit commit 5bac5235934fabe5a3e6a9d47f4812f81034c427, networkd
> cannot acquire DHCP leases on my router if I dual boot with windows.
> It seems to be that my router is borked since I do get leases after
> resetting it to factory defaults, but once booting into the other OS, DHCP
> doesn't work anymore (whichever OS acquired the lease first wins and can
> still get leases after reboots).
> I never used to have this issue until I switched to a new computer with a
> different network card (RTL-8110SC/8169SC). dhclient/dhcpcd also have this
> issue for me, but afaik they can change the clientid method to be used,
> though I never got to use it myself because networkd's implementation just
> worked for me, until it broke :(
> The debug logs don't show anything interesting; it's just stuck in an DHCP
> discover loop.

This sounds weird. Like the server is doing some verification of the
client identity and just ignoring the request if it finds
inconsistencies. At any rate, making this configurable makes sense so
people can get the same lease across several OSs or several dhcp
client implementations, so the patch you sent makes sense!

> 5bac5235934fabe5a3e6a9d47f4812f81034c427 is the first bad commit
> commit 5bac5235934fabe5a3e6a9d47f4812f81034c427
> Author: Tom Gundersen <teg at jklm.no>
> Date:   Thu Jan 22 00:53:16 2015 +0100
>     sd-dhcp-client: use RFC4361-complient ClientID by default
>     In addition to the benefits listed in the RFC, this allows DHCP to work
> also in
>     case several interfaces share the same MAC address on the same link
>     Note that this will make the ClientID (so probably the assigned IP
> address)
>     change on upgrades. If it is desired to avoid that we would have to
> remember and
>     write back the ID (which the library supports, but networkd currently
> does not).
> :040000 040000 0f27d5041b1050e580a329c8c23fd12e1e2c552b
> f1cf96e838f0f4d91c774c3d82346b2ad94465ac M      src
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