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doupod

Member

Registered: 2012-09-06

Posts: 75

Incorrect DNS resolvers post-suspend (Wireguard + NetworkManager)

Hi,

I am using NetworkManager to handle both my wired/wireless network connections as well as my Wireguard VPN. I noticed a weird behavior when going into suspend:

1/ Connect to wired/wireless and then use NetworkManager to connect to Wireguard. DNS are correctly set and only use the DNS provided by Wireguard interface.
2/ Go to suspend, while leaving everything connected as is.
3/ Restore from suspend. NetworkManager will restore the wired/wireless connection as well as the Wireguard tunnel. DNS will be incorrect and /etc/resolv.conf will contain both the DNS resolver provided by the direct uplink (wired/wireless) as well as the DNS from the Wireguard tunnel. Then, I have DNS leaks.

It only happens when going across suspend and back online. I could not find any specific configuration to fix it, including in the wiki.

Would you know how to properly fix this?

Thanks!

-thc

Member

Registered: 2017-03-15

Posts: 1,059

Re: Incorrect DNS resolvers post-suspend (Wireguard + NetworkManager)

This sounds like an oversight (on NetworkManagers part) when using NM/WireGuard as default route/DNS via NM. I suspect NM renews the Wired/WiFi DHCP lease and sets the DNS server again - but that's just my guess.

I use NM/WireGuard as default route/systemd-resolved and this combo doesn't show that behavior.

doupod

Member

Registered: 2012-09-06

Posts: 75

Re: Incorrect DNS resolvers post-suspend (Wireguard + NetworkManager)

Should I report this upstream to NetworkManager then? Or is there any hope for a special configuration to solve this race condition?

I use NM/WireGuard as default route/systemd-resolved and this combo doesn't show that behavior.

But this is a permanent setup, right? Not something you quickly enable/disable on the fly?

seth

Member

From: Don't DM me only for attention

Registered: 2012-09-03

Posts: 70,981

Re: Incorrect DNS resolvers post-suspend (Wireguard + NetworkManager)

We should probably first eliminate the guesswork about what's going on.
Cause the problem and then please post your complete system journal for the boot:

sudo journalctl -b | curl -F 'file=@-' 0x0.st

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GeneArch

Member

Registered: 2013-07-28

Posts: 104

Re: Incorrect DNS resolvers post-suspend (Wireguard + NetworkManager)

I have seen quite a few problems with DNS being replaced while wireguard is running.

When I built my wg-client application (it makes starting / stopping wireguard simple for any user ), it monitors /etc/resolv.conf using inotify. When it detects DNS resolv.conf has changed underneath it, it restores the correct resolv.conf appropriate while wireguard is running. On exit it restores the non-vpn resolv.conf.

In case it's helpful wg-client is in the AUR  and pdf docs are available on Github.

It might  help solve your issue.