Update inet6.py for Destination Option

Extension Headers can show weird behavious. Linux's sk_buff considers the IPv6 Payload to be either TCP, UDP or ICMP. It does not consider Extension Headers to be the payload.

Following similar architecture, This small modification let's packet flow with Destination Option on both, request and response packets be captured as well.

Author: arnavdas88

scapy/layers/inet6.py

@@ -481,7 +481,20 @@ def answers(self, other):
         elif other.nh == 43 and isinstance(other.payload, IPv6ExtHdrSegmentRouting):  # noqa: E501
             return self.payload.answers(other.payload.payload)  # Buggy if self.payload is a IPv6ExtHdrRouting  # noqa: E501
         elif other.nh == 60 and isinstance(other.payload, IPv6ExtHdrDestOpt):
-            return self.payload.answers(other.payload.payload)
+            # Extension Headers can show weird behavious.
+            # Linux's sk_buff considers the IPv6 Payload
+            # to be either TCP, UDP or ICMP. It does not
+            # consider Extension Headers to be the payload.
+            # Following similar architecture, This small 
+            # modification let's packet flow with Destination
+            # Option on both, request and response packets
+            # be captured as well.
+            if UDP in self and UDP in other:
+                return self[UDP].answers(other[UDP])
+            elif TCP in self and TCP in other:
+                return self[TCP].answers(other[TCP]) 
+            else:
+                return self.payload.answers(other.payload.payload) # Previous Implementation
         elif self.nh == 60 and isinstance(self.payload, IPv6ExtHdrDestOpt):  # BU in reply to BRR, for instance  # noqa: E501
             return self.payload.payload.answers(other.payload)
         else: