int pcap_list_datalinks(pcap_t *p, int **dlt_buf);
void pcap_free_datalinks(int *dlt_list);
DESCRIPTIONpcap_list_datalinks() is used to get a list of the supported link-layer header types of the interface associated with the pcap descriptor. pcap_list_datalinks() allocates an array to hold the list and sets *dlt_buf to point to that array.
The caller is responsible for freeing the array with pcap_free_datalinks(), which frees the list of link-layer header types pointed to by dlt_list.
It must not be called on a pcap descriptor created by pcap_create() that has not yet been activated by pcap_activate().