fixestailscale/corp#31299
Fixes two issues:
getInterfaceIndex would occasionally race with netmon's state, returning
the cached default interface index after it had be changed by NWNetworkMonitor.
This had the potential to cause connections to bind to the prior default. The fix
here is to preferentially use the interface index provided by NWNetworkMonitor
preferentially.
When no interfaces are available, macOS will set the tunnel as the default
interface when an exit node is enabled, potentially causing getInterfaceIndex
to return utun's index. We now guard against this when taking the
defaultIdx path.
Signed-off-by: Jonathan Nobels <jonathan@tailscale.com>
Updates tailscale/corp#18960
Tests in corp called us using the wrong logging calls. Removed.
This is logged downstream anyway.
Signed-off-by: Jonathan Nobels <jonathan@tailscale.com>
Updates tailscale/corp#18960
iOS uses Apple's NetworkMonitor to track the default interface and
there's no reason we shouldn't also use this on macOS, for the same
reasons noted in the comments for why this change was made on iOS.
This eliminates the need to load and parse the routing table when
querying the defaultRouter() in almost all cases.
A slight modification here (on both platforms) to fallback to the default
BSD logic in the unhappy-path rather than making assumptions that
may not hold. If netmon is eventually parsing AF_ROUTE and able
to give a consistently correct answer for the default interface index,
we can fall back to that and eliminate the Swift dependency.
Signed-off-by: Jonathan Nobels <jonathan@tailscale.com>
