rpl: remove global variable indicating the root node

sys/net/routing/rpl/rpl_control_messages.c

@@ -35,9 +35,6 @@ static char addr_str[IPV6_MAX_ADDR_STR_LEN];
 #endif
 #include "debug.h"
 
-/* Identification variables */
-static char i_am_root;
-
 /* in send buffer we need space for LL_HDR */
 static uint8_t rpl_send_buffer[BUFFER_SIZE];
 
@@ -244,17 +241,25 @@ void rpl_init_root(rpl_options_t *rpl_opts)
         return;
     }
 
-    i_am_root = 1;
     trickle_start(rpl_process_pid, &dodag->trickle, RPL_MSG_TYPE_TRICKLE_INTERVAL,
                   RPL_MSG_TYPE_TRICKLE_CALLBACK, (1 << dodag->dio_min), dodag->dio_interval_doubling,
                   dodag->dio_redundancy);
     DEBUGF("ROOT INIT FINISHED\n");
 
 }
 
+/* TODO: this function is used by the ip layer for source routing (non-storing mode)
+ * to determine if the node is root and change the dodag direction (upwards -> downwards).
+ * This is a hack and needs to be refactored when the new network stack is ready.
+ */
 uint8_t rpl_is_root(void)
 {
-    return i_am_root;
+    for (uint8_t i = 0; i < RPL_MAX_DODAGS; i++) {
+        if (rpl_dodags[i].node_status == ROOT_NODE) {
+            return 1;
+        }
+    }
+    return 0;
 }
 
 void rpl_send_DIO(rpl_dodag_t *mydodag, ipv6_addr_t *destination)
@@ -342,12 +347,12 @@ void rpl_send_DAO(rpl_dodag_t *my_dodag, ipv6_addr_t *destination, uint8_t lifet
 
 #endif
 
-    if (i_am_root) {
+    if (my_dodag == NULL) {
+        DEBUGF("send_DAO: I have no my_dodag\n");
         return;
     }
 
-    if (my_dodag == NULL) {
-        DEBUGF("send_DAO: I have no my_dodag\n");
+    if (my_dodag->node_status == ROOT_NODE) {
         return;
     }
 
@@ -777,13 +782,9 @@ void rpl_recv_DAO(void)
     }
 
 #if RPL_DEFAULT_MOP == RPL_MOP_NON_STORING_MODE
-
-    if (!i_am_root) {
-        DEBUGF("[Error] something went wrong - got a DAO.\n");
-        return;
-    }
-
-#endif
+    DEBUGF("[Error] something went wrong - got a DAO.\n");
+    return;
+#else
     ipv6_buf = get_rpl_ipv6_buf();
     rpl_dao_buf = get_rpl_dao_buf();
     DEBUG("instance %04X ", rpl_dao_buf->rpl_instanceid);
@@ -870,6 +871,7 @@ void rpl_recv_DAO(void)
         RPL_COUNTER_INCREMENT(my_dodag->dao_seq);
         rpl_delay_dao(my_dodag);
     }
+#endif
 }
 
 void rpl_recv_DIS(void)