doctor: add package for running in-depth healthchecks; use in bugreport (#5413)

Change-Id: Iaa4e5b021a545447f319cfe8b3da2bd3e5e5782b
Signed-off-by: Andrew Dunham <andrew@du.nham.ca>

net/routetable/routetable_darwin.go

@@ -0,0 +1,33 @@
+// Copyright (c) 2022 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.
+
+//go:build darwin
+// +build darwin
+
+package routetable
+
+import "golang.org/x/sys/unix"
+
+const (
+	ribType        = unix.NET_RT_DUMP2
+	parseType      = unix.NET_RT_IFLIST2
+	rmExpectedType = unix.RTM_GET2
+
+	// Skip routes that were cloned from a parent
+	skipFlags = unix.RTF_WASCLONED
+)
+
+var flags = map[int]string{
+	unix.RTF_BLACKHOLE: "blackhole",
+	unix.RTF_BROADCAST: "broadcast",
+	unix.RTF_GATEWAY:   "gateway",
+	unix.RTF_GLOBAL:    "global",
+	unix.RTF_HOST:      "host",
+	unix.RTF_IFSCOPE:   "ifscope",
+	unix.RTF_MULTICAST: "multicast",
+	unix.RTF_REJECT:    "reject",
+	unix.RTF_ROUTER:    "router",
+	unix.RTF_STATIC:    "static",
+	unix.RTF_UP:        "up",
+}