dhclient failed to send packet (DHCPRELEASE) on Debian 11

[Darren Ankney]

I would say to take this to a Debian mailing list.  dhclient is being commanded by Debian to send a release.  I think you are probably right about it being a timing issue (ie: sometimes trying to send after the interface is down).  You could probably find a shell script somewhere that is actually performing these actions and maybe even fix it. Then you’d have something to show the Debian developers as well.

> On Jan 21, 2023, at 5:29 AM, vom513 <vom513 at gmail.com> wrote:
> 
> 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 ?
> 
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