[systemd-devel] Run a separate instance of systemd-networkd in a namespace?

[Dmitrii Sutiagin]

Hi everyone,

I'm trying to set up a VPN in a namespace, so I could use my base 
network connection as usual and at the same time spawn console or 
browser in that namespace where VPN is running. So far I've sorted out 
everything except DNS resolution. Inside namespace there is no 
systemd-networkd, so if my /etc/resolv.conf does not contain a valid 
external DNS server then DNS inside the namespace does not work. And 
since VPN tries to dynamically update /etc/resolv.conf (and with latest 
vpnc-script updates - actually communicates with systemd-resolved via 
busctl), I should not hardcode values in there. Openconnect inside a 
namespace is able to (somehow) talk with root namespace's 
systemd-networkd via busctl but systemd-resolved reports that "link X is 
not known", which is probably expected - this link is inside the 
namespace. So my ask is - can I somehow use systemd-resolved with such 
setup? I tried starting a separate process of systemd-resolved inside 
namespace directly and got:

-------------------------------------
...
Failed to register name: File exists
Could not create manager: File exists
-------------------------------------

Can I somehow change the dbus name used by resolved, and this way I 
could edit vpnc-script to use the modified name..? Looks like it's not 
possible but maybe I overlooked something.

Please share your thoughts!