pcap_datalink_val_to_name, pcap_datalink_val_to_description - get a name or
  description for a link-layer header type value
#include <pcap.h>
const char *pcap_datalink_val_to_name(int dlt);
const char *pcap_datalink_val_to_description(int dlt);
pcap_datalink_val_to_name() translates a link-layer header type value to
  the corresponding link-layer header type name, which is the DLT_ name
  for the link-layer header type value with the DLT_ removed. NULL
  is returned if the type value does not correspond to a known DLT_
  value.
pcap_datalink_val_to_description() translates a link-layer
    header type value to a short description of that link-layer header type.
    NULL is returned if the type value does not correspond to a known
    DLT_ value.