[Networkmanager] Wireguard and IPv6&IPv4 dual stack endpoint with roaming clients from IPv6&IPv4 → IPv4 only networks
thaller at redhat.com
Thu Mar 2 09:14:23 UTC 2023
On Wed, 2023-03-01 at 10:19 +0000, Samuel Le Thiec wrote:
> I'm facing a quite annoying problem with wireguard with
> reading https://blogs.gnome.org/thaller/2019/03/15/wireguard-in-netwo
> > *Dynamically Resolving Endpoints*
> > In WireGuard, peers may have an endpoint configured but also
> > [roaming is built-in]
> > NetworkManager supports peer endpoints specified as DNS names: it
> > will resolve the
> > names before configuring the IP address in kernel. NetworkManager
> > resolves endpoint
> > names every 30 minutes or whenever the DNS configuration of the
> > host changes, in
> > order to pick up changes to the endpoint’s IP address.
> I thought great! This is one good reason to let NetworkManager manage
> instead of using plain wg toolkit.
> My endpoint is a dualstacked IPv6/IPv4 specified by its name, e.g.:
> example.com. 7152 IN A 188.8.131.52
> example.com. 7149 IN AAAA 2606:2800:220:1:248:1893:25c8:1946
> → "Connecting" from a IPv4 only network or a dual stacked network
> works just fine!
> → However, when switching from a IPv4&IPv6 network to a IPv4 only
> network, Network
> Manager does not seem to realize the endpoint is no longer reachable
> via IPv6. I
> suspect this is because there is no DNS change and NM just assumes
> things should
> still be working.
> When checking wg status(sudo wg show wg0), the endpoint is still
> pointing to the IPv6
> $ sudo wg show wg0
> interface: wg0
> public key: SSBrbm93IGkndHMgcHVibGljLCBidXQgaXQncyBhbHNvIGZ1bm55IT8K
> private key: (hidden)
> listening port: 55075
> peer: VGhpcyBpcyBub3Q/IE9rLCBXb24ndCBpdCBkbyBhZ2Fpbgo=
> endpoint: [2606:2800:220:1:248:1893:25c8:1946]:45333
> allowed ips: 10.12.13.0/24, fdba:e3b1:1b22:42::/64
> latest handshake: 1 minute, 40 seconds ago
> transfer: 632 B received, 984 B sent
> As of now, I have to down&up the profile/connection so it starts
> working again.
> Actually, I think the "DNS change" NM is monitoring is a DNS change
> in the client
> configuratoin (like new nameservers, and so on), and not a DNS change
> in the DNS
> Resource Records (example) as I initialy thought it was when reading
> the article.
> And indeed, I am moving between Wifi networks which happened to
> "send" the same DNS
> settings (but one network is dual stacked and the other is not).
> → Can NM detect this on its own? (the unreachability of an IPv6
> Endpoint over an
> IPv4 only network?)
> Many thanks!
Indeed, this should work better. But it seems a difficult problem to
me. Which ultimately is caused by IETF's choice for IPv6 not being
backward compatible and the dual stack solution. But I digress.
NetworkManager probably can easily notice that something relevant might
have changed that warrants a re-evaluation of the endpoint.
But when evaluating which endpoint to use, how would NetworkManager
know which is the working one? Even the initial selection of the
endpoint is rather crude:
Which gets worse, if DNS is resolved via the VPN, and (when the working
IP stack goes down) we might not even be able to re-resolve the DNS
name. The "solution" for that might be to remember the last working DNS
resolution and use that, unless we get a better one. What NM currently
does, is just not switching the endpoint. But the question still
stands, if it wanted to switch, which one would be the preferred one?
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