Comment 39 for bug 1947099

I've tested the package from -proposed and I can confirm it fixes the problem:

Installed from -proposed:

root@ubuntu:~# apt-cache policy klibc-utils
klibc-utils:
  Installed: 2.0.4-9ubuntu2.2
  Candidate: 2.0.4-9ubuntu2.18.04.1
  Version table:
     2.0.4-9ubuntu2.18.04.1 500
        500 http://ppa.launchpad.net/mfo/lp1947099/ubuntu bionic/main amd64 Packages
 *** 2.0.4-9ubuntu2.2 500
        500 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     2.0.4-9ubuntu2.1 500
        500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
     2.0.4-9ubuntu2 500
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages

Working well without timeout:

root@ubuntu:~# ip l set dev ens9 down
root@ubuntu:~# date; /usr/lib/klibc/bin/ipconfig ens9; date
Thu May 12 12:54:48 UTC 2022
IP-Config: ens9 hardware address 52:54:00:f3:4e:0e mtu 1500 DHCP RARP
IP-Config: ens9 complete (dhcp from 192.168.150.2):
 address: 192.168.150.105 broadcast: 192.168.150.255 netmask: 255.255.255.0
 gateway: 192.168.150.1 dns0 : 192.168.150.2 dns1 : 0.0.0.0
 domain : sts.lab
 rootserver: 192.168.150.2 rootpath:
 filename :
Thu May 12 12:55:01 UTC 2022

Timeout being honored:

root@ubuntu:~# ip l set dev ens9 down
root@ubuntu:~# date; /usr/lib/klibc/bin/ipconfig -t 2 ens9; date
Thu May 12 12:55:44 UTC 2022
IP-Config: ens9 hardware address 52:54:00:f3:4e:0e mtu 1500 DHCP RARP
Lowered timeout to match user request = (2 s)
IP-Config: no response after 2 secs - giving up
Thu May 12 12:55:46 UTC 2022

Testing the original issue (timeout being ignored when not receiving any reply from a DHCP Server), which is now also getting honored:

root@ubuntu:~# ip l set dev ens9 down
root@ubuntu:~# date; /usr/lib/klibc/bin/ipconfig -t 2 ens9; date
Thu May 12 12:56:32 UTC 2022
IP-Config: ens9 hardware address 52:54:00:f3:4e:0e mtu 1500 DHCP RARP
Lowered timeout to match user request = (2 s)
IP-Config: no response after 2 secs - giving up
Thu May 12 12:56:34 UTC 2022

root@ubuntu:~# ip l set dev ens9 down
root@ubuntu:~# date; /usr/lib/klibc/bin/ipconfig -t 5 ens9; date
Thu May 12 12:56:43 UTC 2022
IP-Config: ens9 hardware address 52:54:00:f3:4e:0e mtu 1500 DHCP RARP
Lowered timeout to match user request = (5 s)
IP-Config: no response after 5 secs - giving up
Thu May 12 12:56:48 UTC 2022