manually dhclient ethx，dns nameserver in the /etc/resolve.conf will be written duplicate

[Liyuan]

systemd version the issue has been seen with
249

Used distribution
ubuntu22

Linux kernel version used
5.15.0-72-generic

CPU architectures issue was seen on
None

Component
systemd-resolved

Unexpected behaviour you saw

https://github.com/systemd/systemd/issues/28055

not this problem when I was on ubuntu20. The version of systemd is 245

this problem when I was on ubuntu22. The systemd version is 249

I compared the codes and suspected that v248 commit cbf23f3
caused by

I saw this issuse about netplan on ubuntu
https://superuser.com/questions/1721017/remove-redundant-dns-servers-in-ubuntu-22-04

But it doesn't work for dhclient (why I use dhclient, because I found it out of curiosity)

Steps to reproduce the problem
1: Start a virtual machine on the cloud
2: Insert multiple network cards (auxiliary network card)
3: Manually use dhclient to start ethx (except eth0) dhclient -v -d eth1
4: View /etc/resolve.conf

[Liyuan (zhangrocker)]

https://superuser.com/questions/1721017/remove-redundant-dns-servers-in-ubuntu-22-04 ->
https://answers.launchpad.net/ubuntu/+source/systemd/+question/707048 -> this here ,A ha

[Nick Rosbrook (enr0n)]

dhclient is not part of the systemd package, so I will re-assign this bug.