gnrc_netif: centralize S/TLLAO length to address length function

The function to infer the link-layer address length from the length of
a S/TLLAO is very dependent on the IPv6 over X specification and thus
should be grouped with the other IP over X functions.

sys/include/net/gnrc/netif/internal.h

@@ -495,9 +495,40 @@ static inline int gnrc_netif_ipv6_get_iid(gnrc_netif_t *netif, eui64_t *iid)
     (void)iid;
     return -ENOTSUP;
 }
+
+/**
+ * @brief   Derives the length of the link-layer address in an NDP link-layer
+ *          address option from that option's length field and the given device
+ *          type.
+ *
+ * @note    If an RFC exists that specifies how IPv6 operates over a link-layer,
+ *          this function usually implements the section "Unicast Address
+ *          Mapping".
+ *
+ * @see [RFC 4861, section 4.6.1](https://tools.ietf.org/html/rfc4861#section-4.6.1)
+ *
+ * @pre `netif->flags & GNRC_NETIF_FLAGS_HAS_L2ADDR`
+ *
+ * @attention   When `NDEBUG` is not defined, the node fails with an assertion
+ *              instead of returning `-ENOTSUP`
+ *
+ * @param[in] netif The network interface @p opt was received on within an NDP
+ *                  message.
+ * @param[in] opt   An NDP source/target link-layer address option.
+ *
+ * @return  Length of the link-layer address in @p opt on success
+ * @return  `-ENOTSUP`, when implementation does not know how to derive the
+ *          length of the link-layer address from @p opt's length field based
+ *          on gnrc_netif_t::device_type of @p netif.
+ * @return  `-EINVAL` if `opt->len` was an invalid value for the given
+ *          gnrc_netif_t::device_type of @p netif.
+ */
+int gnrc_netif_ndp_addr_len_from_l2ao(gnrc_netif_t *netif,
+                                      const ndp_opt_t *opt);
 #else   /* defined(MODULE_GNRC_IPV6) || defined(DOXYGEN) */
-#define gnrc_netif_ipv6_iid_from_addr(netif, addr, addr_len, iid) (-ENOTSUP)
-#define gnrc_netif_ipv6_iid_to_addr(netif, iid, addr)         (-ENOTSUP)
+#define gnrc_netif_ipv6_iid_from_addr(netif, addr, addr_len, iid)   (-ENOTSUP)
+#define gnrc_netif_ipv6_iid_to_addr(netif, iid, addr)               (-ENOTSUP)
+#define gnrc_netif_ndp_addr_len_from_l2ao(netif, opt)               (-ENOTSUP)
 #define gnrc_netif_ipv6_get_iid(netif, iid)                         (-ENOTSUP)
 #endif  /* defined(MODULE_GNRC_IPV6) || defined(DOXYGEN) */
 /** @} */

sys/net/gnrc/netif/gnrc_netif_device_type.c

@@ -148,6 +148,56 @@ int gnrc_netif_ipv6_iid_to_addr(const gnrc_netif_t *netif, const eui64_t *iid,
     }
     return -ENOTSUP;
 }
+
+int gnrc_netif_ndp_addr_len_from_l2ao(gnrc_netif_t *netif,
+                                      const ndp_opt_t *opt)
+{
+    assert(netif->flags & GNRC_NETIF_FLAGS_HAS_L2ADDR);
+    switch (netif->device_type) {
+#ifdef MODULE_CC110X
+        case NETDEV_TYPE_CC110X:
+            (void)opt;
+            return sizeof(uint8_t);
+#endif  /* MODULE_CC110X */
+#if defined(MODULE_NETDEV_ETH) || defined(MODULE_ESP_NOW)
+        case NETDEV_TYPE_ETHERNET:
+        case NETDEV_TYPE_ESP_NOW:
+            /* see https://tools.ietf.org/html/rfc2464#section-6*/
+            if (opt->len == 1U) {
+                return ETHERNET_ADDR_LEN;
+            }
+            else {
+                return -EINVAL;
+            }
+#endif  /* defined(MODULE_NETDEV_ETH) || defined(MODULE_ESP_NOW) */
+#ifdef MODULE_NRFMIN
+        case NETDEV_TYPE_NRFMIN:
+            (void)opt;
+            return sizeof(uint16_t);
+#endif  /* MODULE_NRFMIN */
+#if defined(MODULE_NETDEV_IEEE802154) || defined(MODULE_XBEE)
+        case NETDEV_TYPE_IEEE802154:
+            /* see https://tools.ietf.org/html/rfc4944#section-8 */
+            switch (opt->len) {
+                case 1U:
+                    return IEEE802154_SHORT_ADDRESS_LEN;
+                case 2U:
+                    return IEEE802154_LONG_ADDRESS_LEN;
+                default:
+                    return -EINVAL;
+            }
+#endif  /* defined(MODULE_NETDEV_IEEE802154) || defined(MODULE_XBEE) */
+        default:
+            (void)opt;
+#ifdef DEVELHELP
+            LOG_ERROR("gnrc_netif: can't get address length from NDP link-layer "
+                      "address option on interface %u\n", netif->pid);
+#endif
+            assert(false);
+            break;
+    }
+    return -ENOTSUP;
+}
 #endif /* MODULE_GNRC_IPV6 */
 
 /** @} */

sys/net/gnrc/network_layer/ipv6/nib/_nib-arsm.c

@@ -30,18 +30,6 @@
 
 static char addr_str[IPV6_ADDR_MAX_STR_LEN];
 
-/**
- * @brief   Determines supposed link-layer address from interface and option
- *          length
- *
- * @param[in] netif A network interface.
- * @param[in] opt   A SL2AO or TL2AO.
- *
- * @return  The length of the L2 address carried in @p opt.
- */
-static inline unsigned _get_l2addr_len(gnrc_netif_t *netif,
-                                       const ndp_opt_t *opt);
-
 void _snd_ns(const ipv6_addr_t *tgt, gnrc_netif_t *netif,
              const ipv6_addr_t *src, const ipv6_addr_t *dst)
 {
@@ -104,10 +92,10 @@ void _handle_sl2ao(gnrc_netif_t *netif, const ipv6_hdr_t *ipv6,
 {
     assert(netif != NULL);
     _nib_onl_entry_t *nce = _nib_onl_get(&ipv6->src, netif->pid);
-    unsigned l2addr_len;
+    int l2addr_len;
 
-    l2addr_len = _get_l2addr_len(netif, sl2ao);
-    if (l2addr_len == 0U) {
+    l2addr_len = gnrc_netif_ndp_addr_len_from_l2ao(netif, sl2ao);
+    if (l2addr_len < 0) {
         DEBUG("nib: Unexpected SL2AO length. Ignoring SL2AO\n");
         return;
     }
@@ -174,43 +162,6 @@ void _handle_sl2ao(gnrc_netif_t *netif, const ipv6_hdr_t *ipv6,
     }
 }
 
-static inline unsigned _get_l2addr_len(gnrc_netif_t *netif,
-                                       const ndp_opt_t *opt)
-{
-    switch (netif->device_type) {
-#ifdef MODULE_CC110X
-        case NETDEV_TYPE_CC110X:
-            (void)opt;
-            return sizeof(uint8_t);
-#endif  /* MODULE_CC110X */
-#if defined(MODULE_NETDEV_ETH) || defined(MODULE_ESP_NOW)
-        case NETDEV_TYPE_ETHERNET:
-        case NETDEV_TYPE_ESP_NOW:
-            (void)opt;
-            return ETHERNET_ADDR_LEN;
-#endif  /* defined(MODULE_NETDEV_ETH) || defined(MODULE_ESP_NOW) */
-#ifdef MODULE_NRFMIN
-        case NETDEV_TYPE_NRFMIN:
-            (void)opt;
-            return sizeof(uint16_t);
-#endif  /* MODULE_NRFMIN */
-#if defined(MODULE_NETDEV_IEEE802154) || defined(MODULE_XBEE)
-        case NETDEV_TYPE_IEEE802154:
-            switch (opt->len) {
-                case 1U:
-                    return IEEE802154_SHORT_ADDRESS_LEN;
-                case 2U:
-                    return IEEE802154_LONG_ADDRESS_LEN;
-                default:
-                    return 0U;
-            }
-#endif  /* defined(MODULE_NETDEV_IEEE802154) || defined(MODULE_XBEE) */
-        default:
-            (void)opt;
-            return 0U;
-    }
-}
-
 #if GNRC_IPV6_NIB_CONF_ARSM
 /**
  * @brief   Calculates exponential back-off for retransmission timer for
@@ -379,13 +330,13 @@ void _probe_nbr(_nib_onl_entry_t *nbr, bool reset)
 void _handle_adv_l2(gnrc_netif_t *netif, _nib_onl_entry_t *nce,
                     const icmpv6_hdr_t *icmpv6, const ndp_opt_t *tl2ao)
 {
-    unsigned l2addr_len = 0;
+    int l2addr_len = 0;
 
     assert(nce != NULL);
     assert(netif != NULL);
     if (tl2ao != NULL) {
-        l2addr_len = _get_l2addr_len(netif, tl2ao);
-        if (l2addr_len == 0U) {
+        l2addr_len = gnrc_netif_ndp_addr_len_from_l2ao(netif, tl2ao);
+        if (l2addr_len < 0) {
             DEBUG("nib: Unexpected TL2AO length. Ignoring TL2AO\n");
             return;
         }