util/cloudenv: add support for DigitalOcean

Updates #4984

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: Ib229eb40af36a80e6b0fd1dd0cabb07f0d50a7d1

util/cloudenv/cloudenv_test.go

@@ -0,0 +1,29 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package cloudenv
+
+import (
+	"flag"
+	"net/netip"
+	"testing"
+)
+
+var extNetwork = flag.Bool("use-external-network", false, "use the external network in tests")
+
+// Informational only since we can run tests in a variety of places.
+func TestGetCloud(t *testing.T) {
+	if !*extNetwork {
+		t.Skip("skipping test without --use-external-network")
+	}
+
+	cloud := getCloud()
+	t.Logf("Cloud: %q", cloud)
+	t.Logf("Cloud.HasInternalTLD: %v", cloud.HasInternalTLD())
+	t.Logf("Cloud.ResolverIP: %q", cloud.ResolverIP())
+}
+
+func TestGetDigitalOceanResolver(t *testing.T) {
+	addr := netip.MustParseAddr(getDigitalOceanResolver())
+	t.Logf("got: %v", addr)
+}