icmpv6_error: doc: provide better references to error codes

sys/include/net/gnrc/icmpv6/error.h

@@ -38,7 +38,7 @@ extern "C" {
  *
  * @pre @p orig_pkt contains a packet snip of type @ref GNRC_NETTYPE_IPV6
  *
- * @param[in] code      The code for the message @see net/icmpv6.h.
+ * @param[in] code      The [code for the message](@ref net_icmpv6_error_dst_unr_codes).
  * @param[in] orig_pkt  The invoking packet.
  */
 void gnrc_icmpv6_error_dst_unr_send(uint8_t code, const gnrc_pktsnip_t *orig_pkt);
@@ -59,7 +59,7 @@ void gnrc_icmpv6_error_pkt_too_big_send(uint32_t mtu,
  *
  * @pre @p orig_pkt contains a packet snip of type @ref GNRC_NETTYPE_IPV6
  *
- * @param[in] code      The code for the message @see net/icmpv6.h.
+ * @param[in] code      The [code for the message](@ref net_icmpv6_error_time_exc_codes).
  * @param[in] orig_pkt  The invoking packet.
  */
 void gnrc_icmpv6_error_time_exc_send(uint8_t code,
@@ -71,7 +71,8 @@ void gnrc_icmpv6_error_time_exc_send(uint8_t code,
  * @pre @p orig_pkt is in receive order.
  * @pre @p orig_pkt contains a packet snip of type @ref GNRC_NETTYPE_IPV6
  *
- * @param[in] code      The code for the message @see net/icmpv6.h.
+ *
+ * @param[in] code      The [code for the message](@ref net_icmpv6_error_param_prob_codes).
  * @param[in] ptr       Pointer to the errorneous octet in @p orig_pkt.
  * @param[in] orig_pkt  The invoking packet.
  */

sys/include/net/icmpv6.h

@@ -75,6 +75,7 @@ extern "C" {
  * @{
  * @name Codes for destination unreachable messages
  *
+ * @anchor net_icmpv6_error_dst_unr_codes
  * @see <a href="https://tools.ietf.org/html/rfc4443#section-3.1">
  *          RFC 4443, section 3.1
  *      </a>
@@ -97,6 +98,7 @@ extern "C" {
  * @{
  * @name Codes for time exceeded messages
  *
+ * @anchor net_icmpv6_error_time_exc_codes
  * @see <a href="https://tools.ietf.org/html/rfc4443#section-3.3">
  *          RFC 4443, section 3.3
  *      </a>
@@ -111,6 +113,7 @@ extern "C" {
  * @{
  * @name Codes for parameter problem messages
  *
+ * @anchor net_icmpv6_error_param_prob_codes
  * @see <a href="https://tools.ietf.org/html/rfc4443#section-3.4">
  *          RFC 4443, section 3.4
  *      </a>