How to refresh DNS lookup?

Ami · March 13, 2023, 4:55pm

When we connect to a VPN while using Snap Slack, a new DNS is set up. However, Snap Slack did not automatically update to the new DNS and instead continue to use the old DNS settings. This can lead to lookup errors such as ERR_NAME_NOT_RESOLVED because the old DNS is no longer reachable.

Is there a way I can add to snapcraft.yaml to access an updated DNS, such as accessing /etc/resolv.conf?"

I also tried with adding plugs like - system-observe - process-control - network-observe - mount-observe - shared-memory - network-manager - network-setup-observe - avahi-control - avahi-observe

and they did not work out for me

Thanks!

sergiusens · March 16, 2023, 1:09pm

Is this a Slack issue or a snap issue? I don’t think I ever had this issue. @pedronis do you think you see a possibility for the snap confinement to interfere here?

ogra · March 17, 2023, 12:13pm

the various network*interfaces all provide access to /run/systemd/resolve/stub-resolv.conf (which nowadays /etc/resolv.conf links to) like:

github.com

snapcore/snapd/blob/master/interfaces/builtin/network.go#L35


  network:
    allow-installation:
      slot-snap-type:
        - core
`
// http://bazaar.launchpad.net/~ubuntu-security/ubuntu-core-security/trunk/view/head:/data/apparmor/policygroups/ubuntu-core/16.04/network
const networkConnectedPlugAppArmor = `
# Description: Can access the network as a client.
#include <abstractions/nameservice>
/run/systemd/resolve/stub-resolv.conf rk,
/etc/mdns.allow r,     # not yet included in the mdns abstraction
network netlink dgram, # not yet included in the nameservice abstraction
# systemd-resolved (not yet included in nameservice abstraction)
#
# Allow access to the safe members of the systemd-resolved D-Bus API:
#
#   https://www.freedesktop.org/wiki/Software/systemd/resolved/
#
# This API may be used directly over the D-Bus system bus or it may be used

i wonder if the host machine VPN setup is not properly integrated with systemd-resolved and instead applies a hack to /etc/resolv.conf directly ?

Ami · March 22, 2023, 11:35pm

I believe I have figured out that it was caused by a one of the settings from Snapcraft.yaml. Thank you!!