Merge pull request #3295 from authmillenon/ng_udp/doc/fix

ng_udp: fix documentation

sys/include/net/ng_udp.h

@@ -70,9 +70,9 @@ typedef struct __attribute__((packed)) {
  * @param[in] pseudo_hdr    Pointer to the network layer header
  *
  * @return  0 on success
- * @return  -EBADMSG if @p pkt is not of type NG_NETTYPE_UDP
- * @return  -EFAULT if @p pkt or @p pseudo_hdr is NULL
- * @return  -ENOENT if @p pseudo_hdr_type is not known
+ * @return  -EBADMSG if @p hdr is not of type NG_NETTYPE_UDP
+ * @return  -EFAULT if @p hdr or @p pseudo_hdr is NULL
+ * @return  -ENOENT if ng_pktsnip_t::type of @p pseudo_hdr is not known
  */
 int ng_udp_calc_csum(ng_pktsnip_t *hdr, ng_pktsnip_t *pseudo_hdr);
 
@@ -86,7 +86,8 @@ int ng_udp_calc_csum(ng_pktsnip_t *hdr, ng_pktsnip_t *pseudo_hdr);
  * @param[in] dst_len       Length of @p dst, must be 2
  *
  * @return  pointer to the newly created (and allocated) header
- * @return  NULL on error
+ * @return  NULL on `src == NULL`, `dst == NULL`, `src_len != 2`, `dst_len != 2`
+ *          or on allocation error
  */
 ng_pktsnip_t *ng_udp_hdr_build(ng_pktsnip_t *payload,
                                uint8_t *src, size_t src_len,

sys/net/transport_layer/ng_udp/ng_udp.c

@@ -208,7 +208,7 @@ int ng_udp_calc_csum(ng_pktsnip_t *hdr, ng_pktsnip_t *pseudo_hdr)
 {
     uint16_t csum;
 
-    if (hdr == NULL || hdr->next == NULL) {
+    if ((hdr == NULL) || (pseudo_hdr == NULL)) {
         return -EFAULT;
     }
     if (hdr->type != NG_NETTYPE_UDP) {