net/netns: move SOCKS dialing to netns for now

This lets control & logs also use SOCKS dials.

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

net/netns/socks.go

@@ -0,0 +1,20 @@
+// Copyright (c) 2020 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.
+
+// +build !ios
+
+package netns
+
+import "golang.org/x/net/proxy"
+
+func init() {
+	wrapDialer = wrapSocks
+}
+
+func wrapSocks(d Dialer) Dialer {
+	if cd, ok := proxy.FromEnvironmentUsing(d).(Dialer); ok {
+		return cd
+	}
+	return d
+}