[thci] wait for netdata to stabilize if `BORDER_ROUTING` is enabled (#7798)

A BR with `BORDER_ROUTING` feature may add OMR prefix and external
routes to the network data when Thread is started.  The network data
changes may incur additional Thread communications that may interfere
with certification traffic.

This commit enhances THCI to wait for the network data to stabilize
after the BR is started.

tools/harness-thci/OpenThread.py

@@ -1145,6 +1145,10 @@ class OpenThreadTHCI(object):
                         self, timeout * 2))
                 else:
                     return False
+
+        if self.IsBorderRouter:
+            self._waitBorderRoutingStabilize()
+
         return True
 
     @API
@@ -1609,6 +1613,30 @@ class OpenThreadTHCI(object):
         else:
             return False
 
+    @watched
+    def getNetworkData(self):
+        lines = self.__executeCommand('netdata show')
+        prefixes, routes, services = [], [], []
+        classify = None
+
+        for line in lines:
+            if line == 'Prefixes:':
+                classify = prefixes
+            elif line == 'Routes:':
+                classify = routes
+            elif line == 'Services:':
+                classify = services
+            elif line == 'Done':
+                classify = None
+            else:
+                classify.append(line)
+
+        return {
+            'Prefixes': prefixes,
+            'Routes': routes,
+            'Services': services,
+        }
+
     @API
     def setNetworkIDTimeout(self, iNwkIDTimeOut):
         """set networkid timeout for Thread device
@@ -3112,6 +3140,14 @@ class OpenThreadTHCI(object):
     def setLeaderWeight(self, iWeight=72):
         self.__executeCommand('leaderweight %d' % iWeight)
 
+    @watched
+    def isBorderRoutingEnabled(self):
+        try:
+            self.__executeCommand('br omrprefix')
+            return True
+        except CommandError:
+            return False
+
     def __detectZephyr(self):
         """Detect if the device is running Zephyr and adapt in that case"""
 

tools/harness-thci/OpenThread_BR.py

@@ -695,3 +695,30 @@ class OpenThread_BR(OpenThreadTHCI, IThci):
         """
         self.externalCommissioner.MLR([sAddr], 0)
         return True
+
+    @watched
+    def _waitBorderRoutingStabilize(self):
+        """
+        Wait for Network Data to stabilize if BORDER_ROUTING is enabled.
+        """
+        if not self.isBorderRoutingEnabled():
+            return
+
+        MAX_TIMEOUT = 30
+        MIN_TIMEOUT = 15
+        CHECK_INTERVAL = 3
+
+        time.sleep(MIN_TIMEOUT)
+
+        lastNetData = self.getNetworkData()
+        for i in range((MAX_TIMEOUT - MIN_TIMEOUT) // CHECK_INTERVAL):
+            time.sleep(CHECK_INTERVAL)
+            curNetData = self.getNetworkData()
+
+            # Wait until the Network Data is not changing, and there is OMR Prefix and External Routes available
+            if curNetData == lastNetData and len(curNetData['Prefixes']) > 0 and len(curNetData['Routes']) > 0:
+                break
+
+            lastNetData = curNetData
+
+        return lastNetData