all: move wgcfg from wireguard-go

This is mostly code movement from the wireguard-go repo.

Most of the new wgcfg package corresponds to the wireguard-go wgcfg package.

wgengine/wgcfg/device{_test}.go was device/config{_test}.go.
There were substantive but simple changes to device_test.go to remove
internal package device references.

The API of device.Config (now wgcfg.DeviceConfig) grew an error return;
we previously logged the error and threw it away.

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>

wgengine/wgcfg/parser_test.go

@@ -0,0 +1,55 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package wgcfg
+
+import (
+	"reflect"
+	"runtime"
+	"testing"
+)
+
+func noError(t *testing.T, err error) bool {
+	if err == nil {
+		return true
+	}
+	_, fn, line, _ := runtime.Caller(1)
+	t.Errorf("Error at %s:%d: %#v", fn, line, err)
+	return false
+}
+
+func equal(t *testing.T, expected, actual interface{}) bool {
+	if reflect.DeepEqual(expected, actual) {
+		return true
+	}
+	_, fn, line, _ := runtime.Caller(1)
+	t.Errorf("Failed equals at %s:%d\nactual   %#v\nexpected %#v", fn, line, actual, expected)
+	return false
+}
+
+func TestParseEndpoint(t *testing.T) {
+	_, _, err := parseEndpoint("[192.168.42.0:]:51880")
+	if err == nil {
+		t.Error("Error was expected")
+	}
+	host, port, err := parseEndpoint("192.168.42.0:51880")
+	if noError(t, err) {
+		equal(t, "192.168.42.0", host)
+		equal(t, uint16(51880), port)
+	}
+	host, port, err = parseEndpoint("test.wireguard.com:18981")
+	if noError(t, err) {
+		equal(t, "test.wireguard.com", host)
+		equal(t, uint16(18981), port)
+	}
+	host, port, err = parseEndpoint("[2607:5300:60:6b0::c05f:543]:2468")
+	if noError(t, err) {
+		equal(t, "2607:5300:60:6b0::c05f:543", host)
+		equal(t, uint16(2468), port)
+	}
+	_, _, err = parseEndpoint("[::::::invalid:18981")
+	if err == nil {
+		t.Error("Error was expected")
+	}
+}