Add a vmtest that brings up a Tailscale client, an Ubuntu VM acting
as a Mullvad-style plain-WireGuard exit node, and a non-Tailscale
webserver, each on its own NAT'd vnet network with a distinct WAN
IP. The test exercises Tailscale's IsWireGuardOnly peer code path:
the way the control plane wires Mullvad exit nodes into a client's
netmap, including the per-client SelfNodeV4MasqAddrForThisPeer
source-IP rewrite that lets a Tailscale CGNAT IP egress through a
plain-WireGuard tunnel that has no idea what Tailscale is.
The mullvad VM doesn't run wireguard-tools or kernel WireGuard;
instead, a new TTA endpoint /wg-server-up creates a real Linux TUN
named wg0, drives it with wireguard-go (already vendored), and
configures the kernel side (ip addr/up, ip_forward, iptables NAT
MASQUERADE) so decrypted traffic from the peer egresses with the
mullvad VM's WAN IP. Userspace vs kernel WireGuard makes no
difference on the wire — what's being tested is Tailscale's
plain-WireGuard exit-node code path, not the kernel module — and
this lets the test avoid downloading and installing .deb packages
inside the VM.
Adds Env.BringUpMullvadWGServer (calls /wg-server-up, returns the
generated WG public key as a key.NodePublic), Env.SetExitNodeIP
(EditPrefs ExitNodeIP directly, for exit nodes whose IPs aren't
discoverable via TTA), Env.ControlServer (exposes the underlying
testcontrol.Server so tests can UpdateNode / SetMasqueradeAddresses
to inject custom peers), and Env.Status (fetches a node's tailscale
status, used to read the client's pubkey so we can pin it as the
WG server's only allowed peer).
The test verifies that the webserver's echoed source IP is the
client's WAN with no exit node selected, the mullvad VM's WAN with
the WG-only peer selected as exit, and the client's WAN again after
clearing.
Updates #13038
Change-Id: I5bac4e0d832f05929f12cb77fa9946d7f5fb5ef1
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
