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

[daggs]

Greetings Andrei,

here:
$ ip r
0.0.0.0 dev enp1s0 scope link 
default dev enp1s0 scope link 
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" <arvidjaar at gmail.com>
> To: systemd-devel at 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 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
> 
>