Log if Same IP is being used or not

[faern]

Desktop+Android equivalent of #5228. Logs when the known Same IP IPs are being used for a WireGuard tunnel. Should aid in debugging any issues that might arise during the rollout of Same IP.

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This change is 

[linear]

DES-386 Log when Same IP is being used

According to the latest plans with how we roll out Same IP, the app will not know about it at all. The API will just start handing out Same IP IPs to apps. But since there is substantial risk of bugs and issues with it (tricky kernel changes server side) we need good ways of debugging this.

Currently if the app sends a problem report, it's not possible/easy to figure out if the user has been assigned Same IP or not. The logs do not contain account or device identifiers, nor IPs. It would be much easier for us to debug Same IP issues if app logs could reveal whether or not Same IP was used.

Solution

Hardcode the currently known Same IP IPs. And if the device has those IPs assigned to it, log on each connection attempt that Same IP is being used.

if device.ips.contains(SAME_IP_IP) {
    log::debug!("Same IP is being used");
}

This will likely be removed a while after the Same IP rollout reaches 100% and that should be noted in the code.

[dlon]

Reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @faern)

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mullvad-daemon/src/tunnel.rs line 33 at r2 (raw file):

/// peer.
static SAME_IP_V4: Lazy<IpAddr> =
    Lazy::new(|| Ipv4Addr::from_str("10.127.255.254").unwrap().into());

Nit: Might be a bit nicer to just use Ipv{4,6}Addr::new here since they're const.