vyos.ethtool: T3163: purify code to read and change flow-control settings

It makes no sense to have a parser for the ethtool values in ethtool.py
and ethernet.py - one instance ios more then enough!

(cherry picked from commit 0229645c8248decb5664056df8aa5cd5dff41802)

2 files changed, 12 insertions, 0 deletions

diff --git a/src/conf_mode/interfaces-ethernet.py b/src/conf_mode/interfaces-ethernet.py
index f3f3fede8..6e0d8c4e8 100755
--- a/src/conf_mode/interfaces-ethernet.py
+++ b/src/conf_mode/interfaces-ethernet.py
@@ -78,6 +78,10 @@ def verify(ethernet):
             raise ConfigError(f'Adapter does not support changing speed and duplex '\
                               f'settings to: {speed}/{duplex}!')
 
+    if 'disable_flow_control' in ethernet:
+        if not ethtool.check_flow_control():
+            raise ConfigError('Adapter does not support changing flow-control settings!')
+
     if 'ring_buffer' in ethernet:
         max_rx = ethtool.get_ring_buffer_max('rx')
         if not max_rx:
diff --git a/src/migration-scripts/interfaces/20-to-21 b/src/migration-scripts/interfaces/20-to-21
index bd89dcdb4..0bd858760 100755
--- a/src/migration-scripts/interfaces/20-to-21
+++ b/src/migration-scripts/interfaces/20-to-21
@@ -104,6 +104,14 @@ for ifname in config.list_nodes(base):
                 config.delete(speed_path)
                 config.delete(duplex_path)
 
+    # Also while processing the interface configuration, not all adapters support
+    # changing disabling flow-control - or change this setting. If disabling
+    # flow-control is not supported by the NIC, we remove the setting from CLI
+    flow_control_path = base + [ifname, 'disable-flow-control']
+    if config.exists(flow_control_path):
+        if not eth.check_flow_control():
+            config.delete(flow_control_path)
+
 try:
     with open(file_name, 'w') as f:
         f.write(config.to_string())