Share a network between 2 rootless instances

[Youpiiiii]

Hello,

I trying rootless for docker but I can't find solution to share a network between 2 rootless instances.
I have a machine with some users. Each users have a rootless instance. But for HAproxy and Traefik we need a network for the backend.
Is there something I missed or a workaround to bypass this problem?

Thank you

[AkihiroSuda]

vde_plug may cover your usecase?

https://github.com/rd235/vdeplug4
https://github.com/rootless-containers/slirp4netns/blob/v1.2.0/slirp4netns.1.md

(host)$ vde_plug --daemon switch:///tmp/switch null://
(host)$ nsenter -t $(cat /tmp/pid-instance0) -U --preserve-credentials -n
(namespace-instance0)$ vde_plug --daemon vde:///tmp/switch tap://vde
(namespace-instance0)$ ip link set vde up
(namespace-instance0)$ ip addr add 192.168.42.100/24 dev vde
(namespace-instance0)$ exit
(host)$ nsenter -t $(cat /tmp/pid-instance1) -U --preserve-credentials -n
(namespace-instance1)$ vde_plug --daemon vde:///tmp/switch tap://vde
(namespace-instance1)$ ip link set vde up
(namespace-instance1)$ ip addr add 192.168.42.101/24 dev vde
(namespace-instance1)$ ping 192.168.42.100

[Youpiiiii]

As I understand it, I must use docker pid like this:
nsenter -t $(cat /run/user/1001/docker.pid) -U --preserve-credentials -n
If yes, I have this error with "ip link set vde up" :
Cannot find device "vde"

[AkihiroSuda]

Cannot find device "vde"

Please make sure to run vde_plug commands above

[Youpiiiii]

vde_plug --daemon switch:///tmp/switch null:// : create a daemon
but
vde_plug --daemon vde:///tmp/switch tap://vde : doesn't create daemon, He stop immediately without error. I see nothing in the logs.

[Youpiiiii]

I had a little time so I tried again.
I tried vde_plug switch:///tmp/switch null:// without daemon and I have a permission denied.
To set all rights change nothing, always permission denied