ng_inet_csum: add debug output

sys/net/crosslayer/ng_inet_csum/ng_inet_csum.c

@@ -12,13 +12,28 @@
  * @file
  */
 
+#include <inttypes.h>
 #include <stdio.h>
+#include "od.h"
 #include "net/ng_inet_csum.h"
 
+#define ENABLE_DEBUG    (0)
+#include "debug.h"
+
 uint16_t ng_inet_csum(uint16_t sum, const uint8_t *buf, uint16_t len)
 {
     uint32_t csum = sum;
 
+    DEBUG("inet_sum: sum = 0x%04" PRIx16 ", len = %" PRIu16, sum, len);
+#if ENABLE_DEBUG
+#ifdef MODULE_OD
+    DEBUG(", buf:\n");
+    od_hex_dump(buf, len, OD_WIDTH_DEFAULT);
+#else
+    DEBUG(", buf output only with od module\n");
+#endif
+#endif
+
     for (int i = 0; i < (len >> 1); buf += 2, i++) {
         csum += (*buf << 8) + *(buf + 1);   /* group bytes by 16-byte words
                                              * and add them*/
@@ -30,6 +45,8 @@ uint16_t ng_inet_csum(uint16_t sum, const uint8_t *buf, uint16_t len)
 
     csum += csum >> 16;
 
+    DEBUG("inet_sum: new sum = 0x%04" PRIx32 "\n", csum & 0xffff);
+
     return (csum & 0xffff);
 }