dhclient failed to send packet (DHCPRELEASE) on Debian 11

[vom513]

Hello all,

So this seems to have been covered multiple times on the list and other various places.  However, I don’t see a solution (assuming that there is one).  Most of the google hits I get are folks with extremely strict firewall rules that end up blocking this outbound packet.  That doesn’t apply to me - I run nftables and I don’t have an “output” policy doing anything.

This is a Debian 11 (bullseye) machine - it’s my firewall.  dhclient is from the isc-dhcp-client package with version 4.4.1-2.3+deb11u1, and kernel is 5.10.0.

So while this doesn’t actually *break* anything per se - it certainly drives me crazy not knowing what’s happening and how to fix it.

It seems like perhaps a race condition ?  Could it be that the interface is “down” and then dhclient tries to send the RELEASE ?  I see this essentially when I do an “ifdown”.  However - I don’t see it 100% of the time :/

--
Jan 21 04:17:30 ice dhclient[303659]: DHCPRELEASE of 1.1.1.1 on enp1s0f4 to 2.2.2.2 port 67
Jan 21 04:17:30 ice dhclient[303659]: send_packet: Invalid argument
Jan 21 04:17:30 ice dhclient[303659]: dhclient.c:2879: Failed to send 300 byte long packet over fallback interface.
—

I even added logging to my input “clean up” rule in nftables - I recreated this issue and I saw nothing in logs to indicate any packets were dropped/denied.

Thanks in advance for any info.

PS: I know this message is very Debian heavy.  I’m certainly willing to jump on a Debian mailing list/forum/bugtracker etc. if need be.  I just figured I would start here.  I also figured that if this were a Debian bug - surely this would have been addressed long ago ?