diff --git a/sys/include/net/gnrc/rpl/structs.h b/sys/include/net/gnrc/rpl/structs.h
index bb56a80f6b..98011b3fa8 100644
--- a/sys/include/net/gnrc/rpl/structs.h
+++ b/sys/include/net/gnrc/rpl/structs.h
@@ -259,8 +259,17 @@ struct gnrc_rpl_parent {
  */
 typedef struct {
     uint16_t ocp;   /**< objective code point */
-    uint16_t (*calc_rank)(gnrc_rpl_parent_t *parent, uint16_t base_rank); /**< calculate the rank */
-    gnrc_rpl_parent_t *(*which_parent)(gnrc_rpl_parent_t *, gnrc_rpl_parent_t *); /**< retrieve the better parent */
+
+    /**
+     * @brief Calculate the rank of this node.
+     *
+     * @param[in]   dodag       RPL DODAG to calculate rank from.
+     * @param[in]   base_rank   BASE_RANK parameter as in rfc6550
+     *
+     * @return      RPL Rank of this node.
+     * @return      GNRC_RPL_INFINITE_RANK, if no rank calculation is possible.
+     */
+    uint16_t (*calc_rank)(gnrc_rpl_dodag_t *dodag, uint16_t base_rank);
 
     /**
      * @brief   Compare two @ref gnrc_rpl_parent_t.
@@ -279,9 +288,21 @@ typedef struct {
      */
     int (*parent_cmp)(gnrc_rpl_parent_t *parent1, gnrc_rpl_parent_t *parent2);
     gnrc_rpl_dodag_t *(*which_dodag)(gnrc_rpl_dodag_t *, gnrc_rpl_dodag_t *); /**< compare for dodags */
-    void (*reset)(gnrc_rpl_dodag_t *);    /**< resets the OF */
+
+    /**
+     * @brief Reset the state of the objective function.
+     *
+     * @param[in]   dodag   RPL dodag object.
+     */
+    void (*reset)(gnrc_rpl_dodag_t *dodag);
     void (*parent_state_callback)(gnrc_rpl_parent_t *, int, int); /**< retrieves the state of a parent*/
-    void (*init)(void);  /**< OF specific init function */
+
+    /**
+     * @brief Initialize the objective function.
+     *
+     * @param[in]   dodag   RPL dodag object.
+     */
+    void (*init)(gnrc_rpl_dodag_t *dodag);
     void (*process_dio)(void);  /**< DIO processing callback (acc. to OF0 spec, chpt 5) */
 } gnrc_rpl_of_t;
 
diff --git a/sys/net/gnrc/routing/rpl/gnrc_rpl_dodag.c b/sys/net/gnrc/routing/rpl/gnrc_rpl_dodag.c
index c32074155a..893f70428d 100644
--- a/sys/net/gnrc/routing/rpl/gnrc_rpl_dodag.c
+++ b/sys/net/gnrc/routing/rpl/gnrc_rpl_dodag.c
@@ -176,7 +176,8 @@ bool gnrc_rpl_dodag_init(gnrc_rpl_instance_t *instance, ipv6_addr_t *dodag_id, k
 
 void gnrc_rpl_dodag_remove_all_parents(gnrc_rpl_dodag_t *dodag)
 {
-    gnrc_rpl_parent_t *elt, *tmp;
+    gnrc_rpl_parent_t *elt = NULL;
+    gnrc_rpl_parent_t *tmp = NULL;
     LL_FOREACH_SAFE(dodag->parents, elt, tmp) {
         gnrc_rpl_parent_remove(elt);
     }
@@ -306,7 +307,8 @@ static gnrc_rpl_parent_t *_gnrc_rpl_find_preferred_parent(gnrc_rpl_dodag_t *doda
     gnrc_rpl_parent_t *old_best = dodag->parents;
     gnrc_rpl_parent_t *new_best = old_best;
     uint16_t old_rank = dodag->my_rank;
-    gnrc_rpl_parent_t *elt, *tmp;
+    gnrc_rpl_parent_t *elt = NULL;
+    gnrc_rpl_parent_t *tmp = NULL;
 
     if (dodag->parents == NULL) {
         return NULL;
@@ -339,7 +341,7 @@ static gnrc_rpl_parent_t *_gnrc_rpl_find_preferred_parent(gnrc_rpl_dodag_t *doda
 
     }
 
-    dodag->my_rank = dodag->instance->of->calc_rank(dodag->parents, 0);
+    dodag->my_rank = dodag->instance->of->calc_rank(dodag, 0);
     if (dodag->my_rank != old_rank) {
         trickle_reset_timer(&dodag->trickle);
     }
diff --git a/sys/net/gnrc/routing/rpl/of0.c b/sys/net/gnrc/routing/rpl/of0.c
index 0fb5e5ddb2..b31018afc2 100644
--- a/sys/net/gnrc/routing/rpl/of0.c
+++ b/sys/net/gnrc/routing/rpl/of0.c
@@ -23,22 +23,20 @@
 #include "net/gnrc/rpl.h"
 #include "net/gnrc/rpl/structs.h"
 
-static uint16_t calc_rank(gnrc_rpl_parent_t *, uint16_t);
-static gnrc_rpl_parent_t *which_parent(gnrc_rpl_parent_t *, gnrc_rpl_parent_t *);
+static uint16_t calc_rank(gnrc_rpl_dodag_t *, uint16_t);
 static int parent_cmp(gnrc_rpl_parent_t *, gnrc_rpl_parent_t *);
 static gnrc_rpl_dodag_t *which_dodag(gnrc_rpl_dodag_t *, gnrc_rpl_dodag_t *);
 static void reset(gnrc_rpl_dodag_t *);
 
 static gnrc_rpl_of_t gnrc_rpl_of0 = {
-    0x0,
-    calc_rank,
-    which_parent,
-    parent_cmp,
-    which_dodag,
-    reset,
-    NULL,
-    NULL,
-    NULL
+    .ocp          = 0x0,
+    .calc_rank    = calc_rank,
+    .parent_cmp   = parent_cmp,
+    .which_dodag  = which_dodag,
+    .reset        = reset,
+    .parent_state_callback = NULL,
+    .init         = NULL,
+    .process_dio  = NULL
 };
 
 gnrc_rpl_of_t *gnrc_rpl_get_of0(void)
@@ -52,20 +50,20 @@ void reset(gnrc_rpl_dodag_t *dodag)
     (void) dodag;
 }
 
-uint16_t calc_rank(gnrc_rpl_parent_t *parent, uint16_t base_rank)
+uint16_t calc_rank(gnrc_rpl_dodag_t *dodag, uint16_t base_rank)
 {
     if (base_rank == 0) {
-        if (parent == NULL) {
+        if (dodag->parents == NULL) {
             return GNRC_RPL_INFINITE_RANK;
         }
 
-        base_rank = parent->rank;
+        base_rank = dodag->parents->rank;
     }
 
     uint16_t add;
 
-    if (parent != NULL) {
-        add = parent->dodag->instance->min_hop_rank_inc;
+    if (dodag->parents != NULL) {
+        add = dodag->instance->min_hop_rank_inc;
     }
     else {
         add = GNRC_RPL_DEFAULT_MIN_HOP_RANK_INCREASE;
@@ -78,15 +76,6 @@ uint16_t calc_rank(gnrc_rpl_parent_t *parent, uint16_t base_rank)
     return base_rank + add;
 }
 
-/* We simply return the Parent with lower rank */
-gnrc_rpl_parent_t *which_parent(gnrc_rpl_parent_t *p1, gnrc_rpl_parent_t *p2)
-{
-    if (parent_cmp(p1, p2) > 0) {
-        return p2;
-    }
-    return p1;
-}
-
 int parent_cmp(gnrc_rpl_parent_t *parent1, gnrc_rpl_parent_t *parent2)
 {
     if (parent1->rank < parent2->rank) {