ifconfig: T1793: add delta check on set_flow_control()

The flow control settings should only be changed when they need to. If flow
control is altered, the kernel will disable and re-enable the interface. This
will not only let the switchport flap but it will also reset e.g. BGP
sessions.

In addition - this also reduces the config commit time.

1 files changed, 19 insertions, 0 deletions

diff --git a/python/vyos/ifconfig.py b/python/vyos/ifconfig.py
index 8a4ad6ffc..cc63482de 100644
--- a/python/vyos/ifconfig.py
+++ b/python/vyos/ifconfig.py
@@ -21,6 +21,7 @@ import glob
 import time
 
 import vyos.interfaces
+
 from vyos.validate import *
 from vyos.config import Config
 from vyos import ConfigError
@@ -1085,6 +1086,24 @@ class EthernetIf(VLANIf):
                             .format(self.get_driver_name()))
             return
 
+        # Get current flow control settings:
+        cmd = '/sbin/ethtool --show-pause {0}'.format(self._ifname)
+        tmp = self._cmd(cmd)
+
+        # The above command returns - with tabs:
+        #
+        # Pause parameters for eth0:
+        # Autonegotiate:  on
+        # RX:             off
+        # TX:             off
+        if re.search("Autonegotiate:\ton", tmp):
+            if enable == "on":
+                # flowcontrol is already enabled - no need to re-enable it again
+                # this will prevent the interface from flapping as applying the
+                # flow-control settings will take the interface down and bring
+                # it back up every time.
+                return
+
         # Assemble command executed on system. Unfortunately there is no way
         # to change this setting via sysfs
         cmd = '/sbin/ethtool --pause {0} autoneg {1} tx {1} rx {1}'.format(