Add a route backwards from the DUT to the test host

server/site_host_route.py

Index: server/site_host_route.py
diff --git a/server/site_host_route.py b/server/site_host_route.py
new file mode 100644
index 0000000000000000000000000000000000000000..78ea0b854d3f4f1700d7ba06f793c81d7c596389
--- /dev/null
+++ b/server/site_host_route.py
@@ -0,0 +1,62 @@
+# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import re, socket, subprocess
+from autotest_lib.client.common_lib import error
+
+class HostRoute(object):
+    """
+    Host Route: A utility for retrieving information about our route to a host
+
+    """
+
+    def __init__(self, host):
+        self.host = host    # Remote host
+        self.calculate()
+
+    def calculate(self):
+        output = self.run_command(["ip", "route", "get", self.host])
+        # This converts "172.22.18.53 via 10.0.0.1 dev eth0 src 10.0.0.200 \n.."
+        # into ("via", "10.0.0.1", "dev", "eth0", "src", "10.0.0.200")
+        route_info = re.split("\s*", output.split("\n")[0].rstrip(' '))[1:]
+
+        # Further, convert the list into a dict {"via": "10.0.0.1", ...}
+        self.route_info = dict(tuple(route_info[i:i+2])
+                               for i in range(0, len(route_info), 2))
+
+        if 'src' not in self.route_info:
+            raise error.TestFail('Cannot find route to host %s' % self.host)
+
+class LocalHostRoute(HostRoute):
+    """
+    Self Host Route: Retrieve host route for the test-host machine
+
+    """
+    def __init__(self, host):
+        # TODO(pstew): If we could depend on the host having the "ip" command
+        # we would just be able to do this:
+        #
+        #     HostRoute.__init__(self, host)
+        #
+        # but alas, we can't depend on this, so we fake it by creating a
+        # socket and figuring out what local address we bound to if we
+        # connected to the client
+        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        sock.connect((host, 22)) # NB: Port doesn't matter
+        self.route_info = { 'src': sock.getsockname()[0] }
+
+    def run_command(self, args):
+        return subprocess.Popen(args, stdout=subprocess.PIPE).communicate()[0]
+
+class RemoteHostRoute(HostRoute):
+    """
+    Remote Host Route: Retrieve host route for a remote (DUT, server) machine
+
+    """
+    def __init__(self, remote, host):
+        self.remote = remote
+        HostRoute.__init__(self, host)
+
+    def run_command(self, args):
+        return self.remote.run(' '.join(args)).stdout