[thread-cert] support to get link-local address of the infra interface (#10603)

This commit targets to support getting infra link-local address of a
OtbrNode in docker test, which is usefully for future test cases.

The test_multi_ail.py is also updated to test the new method added.

tests/scripts/thread-cert/border_router/test_multi_ail.py

@@ -33,6 +33,8 @@ import ipaddress
 import config
 import thread_cert
 
+from node import OtbrNode
+
 IPV4_CIDR_ADDR_CMD = f'ip addr show {config.BACKBONE_IFNAME} | grep -w inet | grep -Eo "[0-9.]+/[0-9]+"'
 
 
@@ -70,8 +72,8 @@ class TwoBorderRoutersOnTwoInfrastructures(thread_cert.TestCase):
     }
 
     def test(self):
-        br1 = self.nodes[self.BR1]
-        br2 = self.nodes[self.BR2]
+        br1: OtbrNode = self.nodes[self.BR1]
+        br2: OtbrNode = self.nodes[self.BR2]
 
         # start nodes
         br1.start()
@@ -92,9 +94,19 @@ class TwoBorderRoutersOnTwoInfrastructures(thread_cert.TestCase):
         self.assertNotEqual(ipaddress.ip_network(br1_infra_ip_addr[0].strip(), strict=False),
                             ipaddress.ip_network(br2_infra_ip_addr[0].strip(), strict=False))
 
-        # ping each other
-        self.assertTrue(br1.ping(br2.get_ip6_address(config.ADDRESS_TYPE.ML_EID)))
-        self.assertTrue(br2.ping(br1.get_ip6_address(config.ADDRESS_TYPE.ML_EID)))
+        # Ping test
+        br1_thread_link_local = br1.get_ip6_address(config.ADDRESS_TYPE.LINK_LOCAL)
+        br2_thread_link_local = br2.get_ip6_address(config.ADDRESS_TYPE.LINK_LOCAL)
+        br1_infra_link_local = br1.get_ip6_address(config.ADDRESS_TYPE.BACKBONE_LINK_LOCAL)
+        br2_infra_link_local = br2.get_ip6_address(config.ADDRESS_TYPE.BACKBONE_LINK_LOCAL)
+
+        # ping each other using Thread link-local address
+        self.assertTrue(br1.ping(br2_thread_link_local))
+        self.assertTrue(br2.ping(br1_thread_link_local))
+
+        # ping each other using Infra link-local address
+        self.assertFalse(br1.ping(br2_infra_link_local, interface=br1_infra_link_local))
+        self.assertFalse(br2.ping(br1_infra_link_local, interface=br2_infra_link_local))
 
 
 if __name__ == '__main__':

tests/scripts/thread-cert/config.py

@@ -106,13 +106,14 @@ DEFAULT_NETWORK_KEY = bytearray([
 
 
 class ADDRESS_TYPE(Enum):
-    LINK_LOCAL = 'LINK_LOCAL'
+    LINK_LOCAL = 'LINK_LOCAL'  # For Thread interface link-local only
     GLOBAL = 'GLOBAL'
     RLOC = 'RLOC'
     ALOC = 'ALOC'
     ML_EID = 'ML_EID'
     DUA = 'DUA'
     BACKBONE_GUA = 'BACKBONE_GUA'
+    BACKBONE_LINK_LOCAL = 'BACKBONE_LINK_LOCAL'
     OMR = 'OMR'
     ONLINK_ULA = 'ONLINK_ULA'
     ONLINK_GUA = 'ONLINK_GUA'

tests/scripts/thread-cert/node.py

@@ -3804,6 +3804,8 @@ class LinuxHost():
         """
         if address_type == config.ADDRESS_TYPE.BACKBONE_GUA:
             return self._getBackboneGua()
+        elif address_type == config.ADDRESS_TYPE.BACKBONE_LINK_LOCAL:
+            return self._getInfraLinkLocalAddress()
         elif address_type == config.ADDRESS_TYPE.ONLINK_ULA:
             return self._getInfraUla()
         elif address_type == config.ADDRESS_TYPE.ONLINK_GUA:
@@ -3835,6 +3837,15 @@ class LinuxHost():
         gua_prefix = config.ONLINK_GUA_PREFIX.split('::/')[0]
         return [addr for addr in self.get_ether_addrs() if addr.startswith(gua_prefix)]
 
+    def _getInfraLinkLocalAddress(self) -> Optional[str]:
+        """ Returns the link-local address autoconfigured on the infra link, which is started with "fe80".
+        """
+        for addr in self.get_ether_addrs():
+            if re.match(config.LINK_LOCAL_REGEX_PATTERN, addr, re.I):
+                return addr
+
+        return None
+
     def ping(self, *args, **kwargs):
         backbone = kwargs.pop('backbone', False)
         if backbone: