Yes. Looks like they are accounted in their own network namespace, it
is quite reasonable. But they are still can be accessed via the file
system from another namespaces. I can confirm that it works too. An
example with the bird control socket:

localhost:~/run# birdc -s retn/bird.ctl show status
BIRD 2.0.4 ready.
BIRD 2.0.4
Router ID is 87.245.192.0
Current server time is 2019-06-07 20:47:32.479
Last reboot on 2019-06-07 20:45:17.425
Last reconfiguration on 2019-06-07 20:45:17.425
Daemon is up and running
localhost:~/run# ip netns exec retn birdc -s retn/bird.ctl show status
BIRD 2.0.4 ready.
BIRD 2.0.4
Router ID is 87.245.192.0
Current server time is 2019-06-07 20:47:49.452
Last reboot on 2019-06-07 20:45:17.425
Last reconfiguration on 2019-06-07 20:45:17.425
Daemon is up and running


On Fri, Jun 7, 2019 at 10:41 PM Maria Matejka <jan.matejka@nic.cz> wrote:
>
> > On 6/7/19 12:14 PM, Maria Jan Matějka wrote:
> >> Thinking once more about it, with respect to the interfaces and so,
> >> the BGP transported over Unix socket seems to be quite simple feature
> >> to do.
> >
> > I thought, and my initial tests support, that Unix sockets are network
> > namespace specific.
> >
> > # netstat -aFunix
> > Kernel Interface table
> > Iface      MTU    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP
> > TX-OVR Flg
> > eno1      1500 77564888      0    614 0      66111123      0      0 0 BMRU
> > lo       65536 68143909      0      0 0      68143909      0      0 0 LRU
> > # ip netns add test
> > # ip netns exec test /bin/netstat -aFunix
> > Kernel Interface table
> > Iface      MTU    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP
> > TX-OVR Flg
> > lo       65536        0      0      0 0             0      0      0
> > 0 L
> > # ip netns del test
> >
> > So, I'm not sure if that's going to work the way that you want.
>
> It will work the same way as the BIRD control socket works.
> You can try it by the attached script (run by root) which uses socat for
> demonstration.
>
> Maria