[PATCH] Add set_mtu and get_mtu API methods

[Jiri Prochazka]

This patch adds two new methods to our API - set_mtu and get_mtu. Names are
self-explanatory,
the only drawback these methods have, is that setting MTU to a certain value is
persistent
on non-virtual devices. Workaround for this is to store mtu values before the test run
and set them back after the test finished.
I will try to implement persistency toggling in the future.

Signed-off-by: Jiri Prochazka <jprochaz(a)redhat.com&gt;
---
 lnst/Controller/Machine.py |  6 ++++++
 lnst/Controller/Task.py    |  6 ++++++
 lnst/Slave/NetTestSlave.py | 12 ++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/lnst/Controller/Machine.py b/lnst/Controller/Machine.py
index e303c1a..fd4f004 100644
--- a/lnst/Controller/Machine.py
+++ b/lnst/Controller/Machine.py
@@ -696,6 +696,12 @@ class Interface(object):
             self._machine._rpc_call("deconfigure_interface", self.get_id())
         self._configured = False
 
+    def set_mtu(self, mtu):
+        self._machine._rpc_call("set_mtu", self.get_id(), mtu)
+
+    def get_mtu(self):
+        return self._machine._rpc_call("get_mtu", self.get_id())
+
 class StaticInterface(Interface):
     """ Static interface
 
diff --git a/lnst/Controller/Task.py b/lnst/Controller/Task.py
index be6b5cc..ee0d468 100644
--- a/lnst/Controller/Task.py
+++ b/lnst/Controller/Task.py
@@ -346,6 +346,12 @@ class InterfaceAPI(object):
     def get_ip_prefix(self, ip_index):
         return VolatileValue(self._if.get_prefix, ip_index)
 
+    def set_mtu(self, mtu):
+        self._if.set_mtu(mtu)
+
+    def get_mtu(self):
+        return VolatileValue(self._if.get_mtu)
+
 class ModuleAPI(object):
     """ An API class representing a module. """
 
diff --git a/lnst/Slave/NetTestSlave.py b/lnst/Slave/NetTestSlave.py
index 8eb1f99..65601a8 100644
--- a/lnst/Slave/NetTestSlave.py
+++ b/lnst/Slave/NetTestSlave.py
@@ -609,6 +609,18 @@ class SlaveMethods:
             device.set_netns(None)
             return True
 
+    def set_mtu(self, if_id, mtu):
+        device = self._if_manager.get_mapped_device(if_id)
+        dev_name = device.get_name()
+        exec_cmd("ip link set dev %s mtu %s" % (dev_name, mtu))
+        return True
+
+    def get_mtu(self, if_id):
+        device = self._if_manager.get_mapped_device(if_id)
+        dev_name = device.get_name()
+        mtu, _ =  exec_cmd("cat /sys/class/net/%s/mtu" % dev_name,
log_outputs=False)
+        return mtu
+
 class ServerHandler(ConnectionHandler):
     def __init__(self, addr):
         super(ServerHandler, self).__init__()
-- 
2.1.0