Added support for handle RPL hop by Hop sender rank 0.

Sender rank zero is possible if originator not set own rank to message.

Author: Juha Heiskanen

CHANGELOG.md

@@ -17,6 +17,7 @@
 * Fixed issues related to channel change failures and bad MAC retransmission timings causing heavily decreasing performance on devices.
 * Corrected memory leak on Border Router key storage that could occur when key storage is allocated on low memory situation
 * Nodes no longer verify BR IID (EAPOL Authenticator EUI-64) from DODAG ID because it causes interworking issues with DODAG IDs which are not generated using EUI-64.
+* Added support for handle RPL hop by Hop sender rank 0. This fixes interoperability issues with other Wi-SUN vendors.
 
 ## Release v12.7.0 (14-12-2020)
 

source/RPL/rpl_data.c

@@ -445,18 +445,20 @@ static buffer_t *rpl_data_exthdr_provider_hbh_2(buffer_t *buf, rpl_instance_t *i
                  * strictly less for Down packets and strictly greater for Up.
                  */
                 sender_rank = common_read_16_bit(opt + 4);
-                rpl_cmp_t cmp = rpl_rank_compare_dagrank_rank(dodag, sender_rank, instance->current_rank);
-                rpl_cmp_t expected_cmp = (opt[2] & RPL_OPT_DOWN) ? RPL_CMP_LESS : RPL_CMP_GREATER;
-                if (cmp != expected_cmp) {
-                    /* Set the Rank-Error bit; if already set, drop */
-                    if (opt[2] & RPL_OPT_RANK_ERROR) {
-                        protocol_stats_update(STATS_RPL_ROUTELOOP, 1);
-                        tr_info("Forwarding inconsistency R");
-                        rpl_instance_inconsistency(instance);
-                        *result = -1;
-                        return buf;
-                    } else {
-                        opt[2] |= RPL_OPT_RANK_ERROR;
+                if (sender_rank != 0) {
+                    rpl_cmp_t cmp = rpl_rank_compare_dagrank_rank(dodag, sender_rank, instance->current_rank);
+                    rpl_cmp_t expected_cmp = (opt[2] & RPL_OPT_DOWN) ? RPL_CMP_LESS : RPL_CMP_GREATER;
+                    if (cmp != expected_cmp) {
+                        /* Set the Rank-Error bit; if already set, drop */
+                        if (opt[2] & RPL_OPT_RANK_ERROR) {
+                            protocol_stats_update(STATS_RPL_ROUTELOOP, 1);
+                            tr_info("Forwarding inconsistency R");
+                            rpl_instance_inconsistency(instance);
+                            *result = -1;
+                            return buf;
+                        } else {
+                            opt[2] |= RPL_OPT_RANK_ERROR;
+                        }
                     }
                 }
             }