Arch Linux

slashvar

Member

Registered: 2016-06-03

Posts: 3

dhcpcd 6.11.0-2 loop forever trying to acquire lease

This issue has already been reported to dhcpcd (ticket 05a4883e1e) and fixed in trunk.

Symptom (striped output from journalctl):

Jun 03 11:39:20 uberwald dhcpcd[8796]: enp10s4f0: soliciting a DHCP lease
Jun 03 11:39:20 uberwald dhcpcd[8796]: enp10s4f0: offered 192.168.X.Y from 192.168.Z.W
Jun 03 11:39:20 uberwald dhcpcd[8796]: enp10s4f0: probing address 192.168.X.Y/24
Jun 03 11:39:20 uberwald dhcpcd[8796]: enp10s4f0: hardware address aa:bb:cc:dd:ee:ff claims 0.0.0.0

The same repeating for ever. We were able to reproduce the problem on several updated machine using dhcpcd 6.11.0-2.

The problem seems to appear only if you got more than one machine doing a dhcp query at the same time. From the ticket it seems that the issue is solved in trunk.

Note that this isn't related to truncated packet issue.

battlepanic

Member

Registered: 2009-08-22

Posts: 76

Re: dhcpcd 6.11.0-2 loop forever trying to acquire lease

I am also hitting this issue after upgrading from dhcpcd 6.10.3-1 to 6.11.0-2.  I also tested the June release of the the Arch ISO in a virtual machine and ran into the same problem.

The output I received from journalctl was more or less identical to what you've described.  I wasn't able to understand the line:

hardware address aa:bb:cc:dd:ee:ff claims 0.0.0.0

where aa:bb:cc:dd:ee:ff is actually the MAC address of another device on my network.

slashvar

Member

Registered: 2016-06-03

Posts: 3

Re: dhcpcd 6.11.0-2 loop forever trying to acquire lease

This is the symptom of the problem. From what I've understand, there's a race condition when dhcpcd sees another dhcp request during address probing: there's a code where it can test a variable that has not been set yet (thus the 0.0.0.0) which makes the probing test to fail. And this where everything goes wrong: your client re-emit a query, triggering the bug in other clients increasing the probability of the race condition to trigger exponentially …

It seems that the bug can be reproduced with only two box requesting IP at the same time.

pli

Member

From: Mountain View, CA

Registered: 2012-03-07

Posts: 4

Re: dhcpcd 6.11.0-2 loop forever trying to acquire lease

Does anyone happen to know (or would care to estimate) when the applied fix will make it into Arch repos?

In the meantime, should users (like me ) who unwittingly upgraded just downgrade to 6.10.3-1?

EDIT: Downgrading has at least restored network connectivity for me, and it didn't seem like there were any dependencies on 6.11.0-2 that I had to resolve.

Last edited by pli (2016-06-08 05:15:10)

slashvar

Member

Registered: 2016-06-03

Posts: 3

Re: dhcpcd 6.11.0-2 loop forever trying to acquire lease

According to the discussion on the ticket (see my first message for an url) the problem is solved in trunk, thus you can try the trunk version using the aur/dhcpcd-trunk that rebuilds dhcpcd from the repo (with all the risk of using a dev branch … )