Squashed commit of the following:

The MLD implementation did not follow the RFC correctly when it is the Querier.  The Querier should use a general query and get query messages from all members of all groups.  This would be driven by a single timer per sub-nset since all groups are queried at once. Instead, the design used a Multicast Address Specific Query with one timer per group and ignores groups that we are not members of.

    Similary, the MLDv1 compatibility timer should be a single, separate timer, not a per-group timer.

    net/mld: Group may be NULL when sending a general query

include/nuttx/net/mld.h

@@ -51,7 +51,9 @@
 
 #include <nuttx/config.h>
 #include <stdint.h>
+#include <queue.h>
 
+#include <nuttx/wdog.h>
 #include <nuttx/net/ip.h>
 #include <nuttx/net/icmpv6.h>
 
@@ -370,6 +372,22 @@ struct mld_mcast_listen_done_s
   net_ipv6addr_t mcastaddr;  /* Multicast address */
 };
 
+/* This structure represents the overall MLD state for a single network.
+ * This structure in included withing the net_driver_s structure.
+ *
+ * There will be a group for the all systems group address but this
+ * will not run the state machine as it is used to kick off reports
+ * from all the other groups
+ */
+
+struct mld_netdev_s
+{
+  sq_queue_t grplist;                /* MLD group list */
+  WDOG_ID gendog;                    /* General query timer */
+  WDOG_ID v1dog;                     /* MLDv1 compatibility timer */
+  uint8_t flags;                     /* See MLD_ flags definitions */
+};
+
 #ifdef CONFIG_NET_STATISTICS
 /* MLD statistic counters */
 

include/nuttx/net/netdev.h

@@ -346,7 +346,7 @@ struct net_driver_s
   sq_queue_t d_igmp_grplist;    /* IGMP group list */
 #endif
 #ifdef CONFIG_NET_MLD
-  sq_queue_t d_mld_grplist;     /* MLD group list */
+  struct mld_netdev_s d_mld;    /* MLD state information */
 #endif
 
 #ifdef CONFIG_NETDEV_STATISTICS