Ignore unexpected ICMPv6 Neighbor Discovery - Neighbor Solicitation packets

We need to adapt all functional traffic scripts related to functional
IPv6 tests to ingore receiving of unexpected ICMPv6ND_NS
(ICMPv6 Neighbor Discovery - Neighbor Solicitation) packets that are
sent automatically and we cannot avoid to receive them.

The reason is to prevent false negative test results in case of csit
functional tests that could block creation of new operational branch
(csit weekly jobs), usage of new vpp builds (csit semiweekly jobs)
and merging patches - csit as well as vpp.

Change-Id: I43c90e7c766762fa769a81661338759a11b401a1
Signed-off-by: Jan Gelety <jgelety@cisco.com>

1 files changed, 28 insertions, 18 deletions

diff --git a/resources/traffic_scripts/check_ra_packet.py b/resources/traffic_scripts/check_ra_packet.py
index 231e07da11..9717c7db95 100755
--- a/resources/traffic_scripts/check_ra_packet.py
+++ b/resources/traffic_scripts/check_ra_packet.py
@@ -17,6 +17,8 @@
 import sys
 import ipaddress
 
+from scapy.layers.inet6 import IPv6, ICMPv6ND_RA, ICMPv6ND_NS
+
 from resources.libraries.python.PacketVerifier import RxQueue
 from resources.libraries.python.TrafficScriptArg import TrafficScriptArg
 
@@ -56,15 +58,23 @@ def main():
     interval = int(args.get_arg('interval'))
     rxq = RxQueue(rx_if)
 
-    ether = rxq.recv(max(5, interval))
+    # receive ICMPv6ND_RA packet
+    while True:
+        ether = rxq.recv(max(5, interval))
+        if ether is None:
+            raise RuntimeError('ICMP echo Rx timeout')
 
-    # Check whether received packet contains layer RA and check other values
-    if ether is None:
-        raise RuntimeError('ICMP echo Rx timeout')
+        if ether.haslayer(ICMPv6ND_NS):
+            # read another packet in the queue if the current one is ICMPv6ND_NS
+            continue
+        else:
+            # otherwise process the current packet
+            break
 
-    if not ether.haslayer('ICMPv6ND_RA'):
-        raise RuntimeError('Not an RA packet received {0}'
-                           .format(ether.__repr__()))
+    # Check if received packet contains layer RA and check other values
+    if not ether.haslayer(ICMPv6ND_RA):
+        raise RuntimeError('Not an RA packet received {0}'.
+                           format(ether.__repr__()))
 
     src_address = ipaddress.IPv6Address(unicode(ether['IPv6'].src))
     dst_address = ipaddress.IPv6Address(unicode(ether['IPv6'].dst))
@@ -72,22 +82,22 @@ def main():
     all_nodes_multicast = ipaddress.IPv6Address(u'ff02::1')
 
     if src_address != link_local:
-        raise RuntimeError(
-            'Source address ({0}) not matching link local address({1})'.format(
-                src_address, link_local))
+        raise RuntimeError('Source address ({0}) not matching link local '
+                           'address ({1})'.format(src_address, link_local))
     if dst_address != all_nodes_multicast:
-        raise RuntimeError('Packet destination address ({0}) is not the all '
-                           'nodes multicast address ({1}).'.format(
-                            dst_address, all_nodes_multicast))
-    if ether['IPv6'].hlim != 255:
-        raise RuntimeError('Hop limit not correct: {0}!=255'.format(
-            ether['IPv6'].hlim))
-
-    ra_code = ether['ICMPv6 Neighbor Discovery - Router Advertisement'].code
+        raise RuntimeError('Packet destination address ({0}) is not the all'
+                           ' nodes multicast address ({1}).'.
+                           format(dst_address, all_nodes_multicast))
+    if ether[IPv6].hlim != 255:
+        raise RuntimeError('Hop limit not correct: {0}!=255'.
+                           format(ether[IPv6].hlim))
+
+    ra_code = ether[ICMPv6ND_RA].code
     if ra_code != 0:
         raise RuntimeError('ICMP code: {0} not correct. '.format(ra_code))
 
     sys.exit(0)
 
+
 if __name__ == "__main__":
     main()