Revert "Rollback new routing functionality (#1805)" (#1813)

This reverts commit 9f32ccd453.

util/net/dialer_linux.go

@@ -0,0 +1,12 @@
+//go:build !android
+
+package net
+
+import "syscall"
+
+// init configures the net.Dialer Control function to set the fwmark on the socket
+func (d *Dialer) init() {
+	d.Dialer.Control = func(_, _ string, c syscall.RawConn) error {
+		return SetRawSocketMark(c)
+	}
+}