T6802: Fix QoS Policy Round-Robin with Default Configuration (#4177)

- Resolved unhandled exception occurring with default round-robin policy config.
- Added default filter to ensure proper round-robin policy.

1 files changed, 12 insertions, 1 deletions

diff --git a/python/vyos/qos/roundrobin.py b/python/vyos/qos/roundrobin.py
index 80814ddfb..509c4069f 100644
--- a/python/vyos/qos/roundrobin.py
+++ b/python/vyos/qos/roundrobin.py
@@ -15,6 +15,7 @@
 
 from vyos.qos.base import QoSBase
 
+
 class RoundRobin(QoSBase):
     _parent = 1
 
@@ -34,11 +35,21 @@ class RoundRobin(QoSBase):
 
         if 'default' in config:
             class_id_max = self._get_class_max_id(config)
-            default_cls_id = int(class_id_max) +1
+            default_cls_id = int(class_id_max) + 1 if class_id_max else 1
 
             # class ID via CLI is in range 1-4095, thus 1000 hex = 4096
             tmp = f'tc class replace dev {self._interface} parent 1:1 classid 1:{default_cls_id:x} drr'
             self._cmd(tmp)
 
+            # You need to add at least one filter to classify packets
+            # otherwise, all packets will be dropped.
+            filter_cmd = (
+                f'tc filter replace dev {self._interface} '
+                f'parent {self._parent:x}: prio {default_cls_id} protocol all '
+                'u32 match u32 0 0 '
+                f'flowid {self._parent}:{default_cls_id}'
+            )
+            self._cmd(filter_cmd)
+
         # call base class
         super().update(config, direction, priority=True)