Implement the "sanity checks" described in b/9509040: Incoming packets

net/quic/quic_dispatcher.h

Index: net/quic/quic_dispatcher.h
diff --git a/net/quic/quic_dispatcher.h b/net/quic/quic_dispatcher.h
index c507556e6839555bda0497db52563798cd33cac9..895f946cd271985f3831c0b07ec08c7a3309396f 100644
--- a/net/quic/quic_dispatcher.h
+++ b/net/quic/quic_dispatcher.h
@@ -133,6 +133,17 @@ class QuicDispatcher : public QuicBlockedWriterInterface,
   virtual bool OnUnauthenticatedPublicHeader(
       const QuicPacketPublicHeader& header);
 
+  // Called by OnUnauthenticatedPublicHeader when the packet is not for a
+  // connection that the dispatcher has a record of, but is not handled by
+  // certain simple processing rules.  This method may apply validity checks to
+  // reject stray packets.  If the packet appears to be valid, it calls
+  // CreateQuicSession to create a new session for the packet.  Returns the
+  // QuicSession that was created, or nullptr if the packet failed the validity
+  // checks.
+  virtual QuicSession* AdditionalValidityChecksThenCreateSession(
+      const QuicPacketPublicHeader& header,
+      QuicConnectionId connection_id);
+
   // Create and return the time wait list manager for this dispatcher, which
   // will be owned by the dispatcher as time_wait_list_manager_
   virtual QuicTimeWaitListManager* CreateQuicTimeWaitListManager();