From 2d0e86aa45c17e850727ff3eb2c76fb4e45cd63b Mon Sep 17 00:00:00 2001
From: Simon Duquennoy <simon.duquennoy@gmail.com>
Date: Thu, 29 Jun 2017 16:08:06 +0200
Subject: [PATCH] rpl-lite: less aggressive probing function: only probe
 non-fresh neighbors. Default period set to 90s"

---
 core/net/rpl-lite/rpl-conf.h                  |  2 +-
 core/net/rpl-lite/rpl-timers.c                | 38 +++++++++++--------
 .../14-rpl-lite/09-rpl-probing.csc            |  2 +-
 regression-tests/15-rpl/09-rpl-probing.csc    |  2 +-
 4 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/core/net/rpl-lite/rpl-conf.h b/core/net/rpl-lite/rpl-conf.h
index 0f955ed31..82759b543 100644
--- a/core/net/rpl-lite/rpl-conf.h
+++ b/core/net/rpl-lite/rpl-conf.h
@@ -270,7 +270,7 @@
 #ifdef RPL_CONF_PROBING_INTERVAL
 #define RPL_PROBING_INTERVAL RPL_CONF_PROBING_INTERVAL
 #else
-#define RPL_PROBING_INTERVAL (60 * CLOCK_SECOND)
+#define RPL_PROBING_INTERVAL (90 * CLOCK_SECOND)
 #endif
 
 /*
diff --git a/core/net/rpl-lite/rpl-timers.c b/core/net/rpl-lite/rpl-timers.c
index 7482b015e..36a5b6267 100644
--- a/core/net/rpl-lite/rpl-timers.c
+++ b/core/net/rpl-lite/rpl-timers.c
@@ -380,33 +380,37 @@ get_probing_target(void)
     return curr_instance.dag.preferred_parent;
   }
 
-  /* With 50% probability: probe best non-fresh neighbor */
-  if(random_rand() % 2 == 0) {
+  /* Now consider probing other non-fresh neighbors. With 2/3 proabability,
+  pick the best non-fresh. Otherwise, pick the lest recently updated non-fresh. */
+
+  if(random_rand() % 3 != 0) {
+    /* Look for best non-fresh */
     nbr = nbr_table_head(rpl_neighbors);
     while(nbr != NULL) {
       if(!rpl_neighbor_is_fresh(nbr)) {
-        /* p is in our dag and needs probing */
-        rpl_rank_t p_rank = rpl_neighbor_rank_via_nbr(nbr);
+        /* nbr needs probing */
+        rpl_rank_t nbr_rank = rpl_neighbor_rank_via_nbr(nbr);
         if(probing_target == NULL
-            || p_rank < probing_target_rank) {
+            || nbr_rank < probing_target_rank) {
           probing_target = nbr;
-          probing_target_rank = p_rank;
+          probing_target_rank = nbr_rank;
         }
       }
       nbr = nbr_table_next(rpl_neighbors, nbr);
     }
-  }
-
-  /* If we still do not have a probing target: pick the least recently updated neighbor */
-  if(probing_target == NULL) {
+  } else {
+    /* Look for least recently updated non-fresh */
     nbr = nbr_table_head(rpl_neighbors);
     while(nbr != NULL) {
-      const struct link_stats *stats =rpl_neighbor_get_link_stats(nbr);
-      if(stats != NULL) {
-        if(probing_target == NULL
-            || clock_now - stats->last_tx_time > probing_target_age) {
-          probing_target = nbr;
-          probing_target_age = clock_now - stats->last_tx_time;
+      if(!rpl_neighbor_is_fresh(nbr)) {
+        /* nbr needs probing */
+        const struct link_stats *stats = rpl_neighbor_get_link_stats(nbr);
+        if(stats != NULL) {
+          if(probing_target == NULL
+              || clock_now - stats->last_tx_time > probing_target_age) {
+            probing_target = nbr;
+            probing_target_age = clock_now - stats->last_tx_time;
+          }
         }
       }
       nbr = nbr_table_next(rpl_neighbors, nbr);
@@ -436,6 +440,8 @@ handle_probing_timer(void *ptr)
     /* Send probe, e.g. unicast DIO or DIS */
     RPL_PROBING_SEND_FUNC(target_ipaddr);
     curr_instance.dag.urgent_probing_target = NULL;
+  } else {
+    LOG_INFO("no neighbor needs probing\n");
   }
 
   /* Schedule next probing */
diff --git a/regression-tests/14-rpl-lite/09-rpl-probing.csc b/regression-tests/14-rpl-lite/09-rpl-probing.csc
index f7d9c0290..7e5ef727a 100644
--- a/regression-tests/14-rpl-lite/09-rpl-probing.csc
+++ b/regression-tests/14-rpl-lite/09-rpl-probing.csc
@@ -204,7 +204,7 @@ GENERATE_MSG(1500000, "moving root back");&#xD;
 &#xD;
 lostMsgs = 0;&#xD;
 &#xD;
-TIMEOUT(6000000, if(lastMsg != -1 &amp;&amp; lastMsgHops == 1 &amp;&amp; lostMsgs &lt;= 2  &amp;&amp; num &gt; 20) { log.testOK(); } );&#xD;
+TIMEOUT(10000000, if(lastMsg != -1 &amp;&amp; lastMsgHops == 1 &amp;&amp; lostMsgs &lt;= 2  &amp;&amp; num &gt; 20) { log.testOK(); } );&#xD;
 &#xD;
 lastMsg = -1;&#xD;
 packets = "_________";&#xD;
diff --git a/regression-tests/15-rpl/09-rpl-probing.csc b/regression-tests/15-rpl/09-rpl-probing.csc
index f7d9c0290..7e5ef727a 100644
--- a/regression-tests/15-rpl/09-rpl-probing.csc
+++ b/regression-tests/15-rpl/09-rpl-probing.csc
@@ -204,7 +204,7 @@ GENERATE_MSG(1500000, "moving root back");&#xD;
 &#xD;
 lostMsgs = 0;&#xD;
 &#xD;
-TIMEOUT(6000000, if(lastMsg != -1 &amp;&amp; lastMsgHops == 1 &amp;&amp; lostMsgs &lt;= 2  &amp;&amp; num &gt; 20) { log.testOK(); } );&#xD;
+TIMEOUT(10000000, if(lastMsg != -1 &amp;&amp; lastMsgHops == 1 &amp;&amp; lostMsgs &lt;= 2  &amp;&amp; num &gt; 20) { log.testOK(); } );&#xD;
 &#xD;
 lastMsg = -1;&#xD;
 packets = "_________";&#xD;