6lowpan nd: check right NCE in AR handling

When checking the address registration option, the address has to be passed in order to check the correct neighbor cache entry.

sys/include/net/gnrc/sixlowpan/nd.h

@@ -195,6 +195,7 @@ gnrc_pktsnip_t *gnrc_sixlowpan_nd_opt_ar_build(uint8_t status, uint16_t ltime, e
  * @param[in] ipv6          The IPv6 header the ARO was received in.
  * @param[in] icmpv6_type   Message type of the ICMPv6 message that contained.
  *                          this message.
+ * @param[in] addr          The IPv6 address to register.
  * @param[in] ar_opt        The address registration option.
  * @param[in] sl2a          The link-layer source address contained in SL2A accompanying this
  *                          option. May be NULL for icmpv6_type == ICMPV6_NBR_ADV.
@@ -203,7 +204,8 @@ gnrc_pktsnip_t *gnrc_sixlowpan_nd_opt_ar_build(uint8_t status, uint16_t ltime, e
  * @return  Status for the ARO in the replying NA (always 0 if icmpv6_type == ICMPV6_NBR_ADV).
  */
 uint8_t gnrc_sixlowpan_nd_opt_ar_handle(kernel_pid_t iface, ipv6_hdr_t *ipv6,
-                                        uint8_t icmpv6_type, sixlowpan_nd_opt_ar_t *ar_opt,
+                                        uint8_t icmpv6_type, ipv6_addr_t *addr,
+                                        sixlowpan_nd_opt_ar_t *ar_opt,
                                         uint8_t *sl2a, size_t sl2a_len);
 
 /**

sys/net/gnrc/network_layer/ndp/gnrc_ndp.c

@@ -167,7 +167,9 @@ void gnrc_ndp_nbr_sol_handle(kernel_pid_t iface, gnrc_pktsnip_t *pkt,
     if ((sl2a_opt != NULL) && (ar_opt != NULL) &&
         (ipv6_iface->flags & GNRC_IPV6_NETIF_FLAGS_SIXLOWPAN) &&
         (ipv6_iface->flags & GNRC_IPV6_NETIF_FLAGS_ROUTER)) {
-        uint8_t status = gnrc_sixlowpan_nd_opt_ar_handle(iface, ipv6, nbr_sol->type, ar_opt,
+        uint8_t status = gnrc_sixlowpan_nd_opt_ar_handle(iface, ipv6,
+                                                         nbr_sol->type,
+                                                         &ipv6->src, ar_opt,
                                                          l2src, l2src_len);
         /* check for multihop DAD return */
         nbr_adv_opts = gnrc_sixlowpan_nd_opt_ar_build(status, GNRC_SIXLOWPAN_ND_AR_LTIME,
@@ -253,7 +255,9 @@ void gnrc_ndp_nbr_adv_handle(kernel_pid_t iface, gnrc_pktsnip_t *pkt,
             case NDP_OPT_AR:
                 /* address registration option is always ignored when invalid */
                 gnrc_sixlowpan_nd_opt_ar_handle(iface, ipv6, nbr_adv->type,
-                                                (sixlowpan_nd_opt_ar_t *)opt, NULL, 0);
+                                                &nbr_adv->tgt,
+                                                (sixlowpan_nd_opt_ar_t *)opt,
+                                                NULL, 0);
                 break;
 #endif
             default:

sys/net/gnrc/network_layer/sixlowpan/nd/gnrc_sixlowpan_nd.c

@@ -242,9 +242,10 @@ gnrc_pktsnip_t *gnrc_sixlowpan_nd_opt_ar_build(uint8_t status, uint16_t ltime, e
     return pkt;
 }
 
-uint8_t gnrc_sixlowpan_nd_opt_ar_handle(kernel_pid_t iface, ipv6_hdr_t *ipv6, uint8_t icmpv6_type,
-                                        sixlowpan_nd_opt_ar_t *ar_opt, uint8_t *sl2a,
-                                        size_t sl2a_len)
+uint8_t gnrc_sixlowpan_nd_opt_ar_handle(kernel_pid_t iface, ipv6_hdr_t *ipv6,
+                                        uint8_t icmpv6_type, ipv6_addr_t *addr,
+                                        sixlowpan_nd_opt_ar_t *ar_opt,
+                                        uint8_t *sl2a, size_t sl2a_len)
 {
     eui64_t eui64;
     gnrc_ipv6_netif_t *ipv6_iface;
@@ -262,7 +263,7 @@ uint8_t gnrc_sixlowpan_nd_opt_ar_handle(kernel_pid_t iface, ipv6_hdr_t *ipv6, ui
         return 0;
     }
     ipv6_iface = gnrc_ipv6_netif_get(iface);
-    nc_entry = gnrc_ipv6_nc_get(iface, &ipv6->src);
+    nc_entry = gnrc_ipv6_nc_get(iface, addr);
     switch (icmpv6_type) {
         case ICMPV6_NBR_ADV:
             if (!(ipv6_iface->flags & GNRC_IPV6_NETIF_FLAGS_SIXLOWPAN)) {
@@ -273,6 +274,12 @@ uint8_t gnrc_sixlowpan_nd_opt_ar_handle(kernel_pid_t iface, ipv6_hdr_t *ipv6, ui
                 /* discard silently: see https://tools.ietf.org/html/rfc6775#section-5.5.2 */
                 return 0;
             }
+            /* we expect the sender to be already in neighbor cache, if not we
+             * ignore it */
+            if (nc_entry == NULL) {
+                DEBUG("6lo nd: sending router not in neighbor cache\n");
+                return 0;
+            }
             switch (ar_opt->status) {
                 case SIXLOWPAN_ND_STATUS_SUCCESS:
                     DEBUG("6lo nd: address registration successful\n");