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

[Andrei Borzenkov]

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 at 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