From c26aed5565eed273f6715be7fd9b88c77e6c6f4f Mon Sep 17 00:00:00 2001
From: Laurent Deru <laurent.deru@cetic.be>
Date: Mon, 11 Dec 2017 11:09:37 +0100
Subject: [PATCH] Always select a global address within the DODAG

---
 os/net/rpl-classic/rpl-icmp6.c | 18 +++++++++++++-----
 os/net/rpl-lite/rpl.c          | 10 +++++++++-
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/os/net/rpl-classic/rpl-icmp6.c b/os/net/rpl-classic/rpl-icmp6.c
index c5114fd14..6d9a2bca3 100644
--- a/os/net/rpl-classic/rpl-icmp6.c
+++ b/os/net/rpl-classic/rpl-icmp6.c
@@ -141,15 +141,23 @@ get_global_addr(uip_ipaddr_t *addr)
 {
   int i;
   int state;
+  uip_ipaddr_t *prefix = NULL;
+  uint8_t prefix_length = 0;
+  rpl_dag_t *dag = rpl_get_any_dag();
+
+  if(dag != NULL && dag->prefix_info.length != 0) {
+    prefix = &dag->prefix_info.prefix;
+    prefix_length = dag->prefix_info.length;
+  }
 
   for(i = 0; i < UIP_DS6_ADDR_NB; i++) {
     state = uip_ds6_if.addr_list[i].state;
     if(uip_ds6_if.addr_list[i].isused &&
-       (state == ADDR_TENTATIVE || state == ADDR_PREFERRED)) {
-      if(!uip_is_addr_linklocal(&uip_ds6_if.addr_list[i].ipaddr)) {
-        memcpy(addr, &uip_ds6_if.addr_list[i].ipaddr, sizeof(uip_ipaddr_t));
-        return 1;
-      }
+       state == ADDR_PREFERRED &&
+       !uip_is_addr_linklocal(&uip_ds6_if.addr_list[i].ipaddr) &&
+       (prefix == NULL || uip_ipaddr_prefixcmp(prefix, &uip_ds6_if.addr_list[i].ipaddr, prefix_length))) {
+      memcpy(addr, &uip_ds6_if.addr_list[i].ipaddr, sizeof(uip_ipaddr_t));
+      return 1;
     }
   }
   return 0;
diff --git a/os/net/rpl-lite/rpl.c b/os/net/rpl-lite/rpl.c
index 76d49d562..29eca52b0 100644
--- a/os/net/rpl-lite/rpl.c
+++ b/os/net/rpl-lite/rpl.c
@@ -71,12 +71,20 @@ rpl_get_global_address(void)
   int i;
   uint8_t state;
   uip_ipaddr_t *ipaddr = NULL;
+  uip_ipaddr_t *prefix = NULL;
+  uint8_t prefix_length = 0;
+
+  if(curr_instance.used && curr_instance.dag.prefix_info.length != 0) {
+    prefix = &curr_instance.dag.prefix_info.prefix;
+    prefix_length = curr_instance.dag.prefix_info.length;
+  }
 
   for(i = 0; i < UIP_DS6_ADDR_NB; i++) {
     state = uip_ds6_if.addr_list[i].state;
     if(uip_ds6_if.addr_list[i].isused &&
        state == ADDR_PREFERRED &&
-       !uip_is_addr_linklocal(&uip_ds6_if.addr_list[i].ipaddr)) {
+       !uip_is_addr_linklocal(&uip_ds6_if.addr_list[i].ipaddr) &&
+       (prefix == NULL || uip_ipaddr_prefixcmp(prefix, &uip_ds6_if.addr_list[i].ipaddr, prefix_length))) {
       ipaddr = &uip_ds6_if.addr_list[i].ipaddr;
     }
   }