[icmp responder]: Allow hardcoding of ICMP responder MAC (#2970)

ICMP responder needs to reply to linkmgrd heartbeats using VLAN MAC as the destination MAC. Linkmgrd sends the heartbeat with the interface MAC instead of the VLAN MAC, and ICMP responder simply re-uses the interface MAC.

This change allows ICMP responder to always reply with the VLAN MAC.

tests/common/fixtures/ptfhost_utils.py

@@ -177,7 +177,11 @@ def run_icmp_responder(duthost, ptfhost, tbinfo):
     templ = Template(open(os.path.join(TEMPLATES_DIR, ICMP_RESPONDER_CONF_TEMPL)).read())
     ptf_indices = duthost.get_extended_minigraph_facts(tbinfo)["minigraph_ptf_indices"]
     vlan_intfs = duthost.get_vlan_intfs()
+    vlan_table = duthost.get_running_config_facts()['VLAN']
+    vlan_name = list(vlan_table.keys())[0]
+    vlan_mac = vlan_table[vlan_name]['mac']
     icmp_responder_args = " ".join("-i eth%s" % ptf_indices[_] for _ in vlan_intfs)
+    icmp_responder_args += " " + "-m {}".format(vlan_mac)
     ptfhost.copy(
         content=templ.render(icmp_responder_args=icmp_responder_args),
         dest=os.path.join(SUPERVISOR_CONFIG_DIR, "icmp_responder.conf")

tests/scripts/icmp_responder.py

@@ -6,15 +6,21 @@
 from select import select
 
 
-def respond_to_icmp_request(socket, request):
+def respond_to_icmp_request(socket, request, dst_mac=None):
     """Respond to ICMP request."""
     reply = request.copy()
     reply[ICMP].type = 0
     # Force re-generation of the checksum
     reply[ICMP].chksum = None
     reply[IP].src, reply[IP].dst = request[IP].dst, request[IP].src
     reply[IP].chksum = None
-    reply[Ether].src, reply[Ether].dst = request[Ether].dst, request[Ether].src
+
+    if dst_mac is None:
+        icmp_reply_dst_mac = request[Ether].src
+    else:
+        icmp_reply_dst_mac = dst_mac
+
+    reply[Ether].src, reply[Ether].dst = request[Ether].dst, icmp_reply_dst_mac
     socket.send(reply)
 
 
@@ -23,7 +29,7 @@ class ICMPSniffer(object):
 
     TYPE_ECHO_REQUEST = 8
 
-    def __init__(self, ifaces, request_handler=None):
+    def __init__(self, ifaces, request_handler=None, dst_mac=None):
         """
         Init ICMP sniffer.
 
@@ -37,6 +43,7 @@ def __init__(self, ifaces, request_handler=None):
             self.sniff_sockets.append(conf.L2socket(type=ETH_P_IP, iface=iface, filter="icmp"))
             self.iface_hwaddr[iface] = get_if_hwaddr(iface)
         self.request_handler = request_handler
+        self.dst_mac = dst_mac
 
     def __call__(self):
         try:
@@ -46,7 +53,7 @@ def __call__(self):
                     packet = s.recv()
                     if packet is not None:
                         if packet[ICMP].type == self.TYPE_ECHO_REQUEST and self.request_handler:
-                            self.request_handler(s, packet)
+                            self.request_handler(s, packet, self.dst_mac)
         finally:
             for s in self.sniff_sockets:
                 s.close()
@@ -55,8 +62,10 @@ def __call__(self):
 if __name__ == "__main__":
     parser = argparse.ArgumentParser(description="ICMP responder")
     parser.add_argument("--intf", "-i", dest="ifaces", required=True, action="append", help="interface to listen for ICMP request")
+    parser.add_argument("--dst_mac", "-m", dest="dst_mac", required=False, action="store", help="The destination MAC to use for ICMP echo replies")
     args = parser.parse_args()
     ifaces = args.ifaces
+    dst_mac = args.dst_mac
 
-    icmp_sniffer = ICMPSniffer(ifaces, request_handler=respond_to_icmp_request)
+    icmp_sniffer = ICMPSniffer(ifaces, request_handler=respond_to_icmp_request, dst_mac=dst_mac)
     icmp_sniffer()