Re: [systemd-devel] accepting dhcp address only from a specific mask

[Andrei Borzenkov]

02.06.2025 18:30, daggs wrote:
Greetings Andrei,
here:
$ ip r
0.0.0.0 dev enp1s0 scope link
default dev enp1s0 scope link

Those two lines are most certainly a problem. If they are installed by 
systemd-networkd, I would call it a bug. Even with IPv4 local addresses 
they are still wrong.

default via 192.168.0.1 dev enp1s0  src 192.168.0.10  metric 1024
169.254.0.0/16 dev enp1s0 scope link  src 169.254.39.180
192.168.0.0/24 dev enp1s0 scope link  src 192.168.0.10  metric 1024
192.168.0.1 dev enp1s0 scope link  src 192.168.0.10  metric 1024


Sent: Monday, June 02, 2025 at 6:16 PM
From: "Andrei Borzenkov" <arvidj...@gmail.com>
To: systemd-devel@lists.freedesktop.org
Subject: Re: [systemd-devel] accepting dhcp address only from a specific mask

02.06.2025 16:07, daggs wrote:
Greetings,

I have a qemu vm which runs a systemd based buildroot image, the vm's nic is 
virtio, if I configure systemd to auto start the nic, I get two ips for the 
only nic on the system, a valid one and in invalid one.
in this case, I can only connect to local lan but not outside of the last,

Show

ip r

Multiple addresses on a interface is not something unusual.

I once were able to get to a situation where only the valid ip is set and 
tested outside connection at it worked.
here is the output of ip a:

$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1000
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
      inet 127.0.0.1/8 scope host lo
         valid_lft forever preferred_lft forever
      inet6 ::1/128 scope host noprefixroute
         valid_lft forever preferred_lft forever
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP8000> mtu 1500 qdisc fq_codel qlen 
1000
      link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
      inet 192.168.0.10/24 brd 192.168.0.255 scope global dynamic enp1s0
         valid_lft 40422sec preferred_lft 40422sec
      inet 169.254.39.180/16 brd 169.254.255.255 scope global enp1s0
         valid_lft forever preferred_lft forever
      inet6 xxxx::xxxx:xx:xxxx:xxxx/64 scope link
         valid_lft forever preferred_lft forever
3: sit0@NONE: <NOARP> mtu 1480 qdisc noop qlen 1000
      link/sit 0.0.0.0 brd 0.0.0.0

$ cat /etc/systemd/network/enp1s0.network
[Match]
Name=enp1s0
[Network]
DHCP=ipv4

I'm no sure this is a systemd bug as I saw it when I tried a non systemd based 
env, so I'd like to try and prevent such allocation so the system will work 
until I can properly solve it.
is it possible?

Thanks

Dagg