REED advertisement handling (Thread spec 5.16.3): (ARMmbed#1535)

Whenever a REED receives an MLE Advertisement from a
REED in a neighboring Partition with a higher-priority
than its current Thread Network Partition,
it attempts to attach to a Parent in that
higher-priority Thread Network Partition.

Author: deepakvenugopal

source/6LoWPAN/Thread/thread_mle_message_handler.c

@@ -45,6 +45,7 @@
 #include "6LoWPAN/Thread/thread_leader_service.h"
 #include "6LoWPAN/Thread/thread_tmfcop_lib.h"
 #include "6LoWPAN/Thread/thread_host_bootstrap.h"
+#include "6LoWPAN/Thread/thread_extension.h"
 #include "6LoWPAN/Thread/thread_router_bootstrap.h"
 #include "6LoWPAN/Thread/thread_network_synch.h"
 #include "6LoWPAN/MAC/mac_helper.h"
@@ -238,6 +239,29 @@ static bool thread_router_leader_data_process(protocol_interface_info_entry_t *c
     return true;
 }
 
+static bool thread_reed_partitions_merge(protocol_interface_info_entry_t *cur, uint16_t shortAddress, thread_leader_data_t heard_partition_leader_data)
+{
+    if (thread_is_router_addr(shortAddress)) {
+        return false;
+    }
+    if (thread_extension_version_check(thread_info(cur)->version)) {
+        // lower weighting heard
+        if (thread_info(cur)->thread_leader_data->weighting > heard_partition_leader_data.weighting) {
+            return false;
+        }
+        // lower/same partition id heard
+        if (thread_info(cur)->thread_leader_data->weighting == heard_partition_leader_data.weighting &&
+                thread_info(cur)->thread_leader_data->partitionId >= heard_partition_leader_data.partitionId ) {
+            return false;
+        }
+    } else if (thread_info(cur)->thread_leader_data->partitionId >= heard_partition_leader_data.partitionId){
+        return false;
+    }
+    // can merge to a higher weighting/partition id
+    thread_bootstrap_connection_error(cur->id, CON_ERROR_PARTITION_MERGE, NULL);
+    return true;
+}
+
 static bool thread_router_advertiment_tlv_analyze(uint8_t *ptr, uint16_t data_length, thread_leader_data_t *leaderData, uint16_t *shortAddress, mle_tlv_info_t *routeTlv)
 {
     //Read Leader Data and verify connectivity
@@ -347,7 +371,7 @@ static void thread_parse_advertisement(protocol_interface_info_entry_t *cur, mle
             // REED and FED
             if (!entry_temp && thread_bootstrap_link_create_check(cur, shortAddress) && thread_bootstrap_link_create_allowed(cur, shortAddress, mle_msg->packet_src_address)) {
                 if ((thread_info(cur)->thread_leader_data->partitionId == leaderData.partitionId) &&
-                    (thread_info(cur)->thread_leader_data->weighting == leaderData.weighting)) {
+                        (thread_info(cur)->thread_leader_data->weighting == leaderData.weighting)) {
                     // Create link to new neighbor no other processing allowed
                     thread_link_request_start(cur, mle_msg->packet_src_address);
                     return;
@@ -357,6 +381,10 @@ static void thread_parse_advertisement(protocol_interface_info_entry_t *cur, mle
                     return;
                 }
             }
+            // process REED advertisement from higher partition
+            if (thread_reed_partitions_merge(cur, shortAddress, leaderData)) {
+                return;
+            }
         } else {
             //Router
             if (!thread_router_leader_data_process(cur, mle_msg->packet_src_address, &leaderData, &routeTlv, entry_temp) ) {