Add support for iif rules.

On real systems, we use this to set up tethering.

Change-Id: I0896191754c81e385a08b325922ad42230980d9e
diff --git a/net/test/iproute.py b/net/test/iproute.py
index f2aba7b..4a81191 100644
--- a/net/test/iproute.py
+++ b/net/test/iproute.py
@@ -475,6 +475,10 @@
     nlattr = self._NlAttrU32(FRA_FWMARK, fwmark)
     return self._Rule(version, is_add, RTN_UNICAST, table, nlattr, priority)
 
+  def IifRule(self, version, is_add, iif, table, priority):
+    nlattr = self._NlAttrInterfaceName(FRA_IIFNAME, iif)
+    return self._Rule(version, is_add, RTN_UNICAST, table, nlattr, priority)
+
   def OifRule(self, version, is_add, oif, table, priority):
     nlattr = self._NlAttrInterfaceName(FRA_OIFNAME, oif)
     return self._Rule(version, is_add, RTN_UNICAST, table, nlattr, priority)
diff --git a/net/test/multinetwork_base.py b/net/test/multinetwork_base.py
index 24b9575..1e00f74 100644
--- a/net/test/multinetwork_base.py
+++ b/net/test/multinetwork_base.py
@@ -128,6 +128,7 @@
   PRIORITY_UID = 100
   PRIORITY_OIF = 200
   PRIORITY_FWMARK = 300
+  PRIORITY_IIF = 400
   PRIORITY_DEFAULT = 999
   PRIORITY_UNREACHABLE = 1000