pcap_create.3pcap man page
pcap_create — create a live capture handle
#include <pcap/pcap.h> char errbuf[PCAP_ERRBUF_SIZE]; pcap_t *pcap_create(const char *source, char *errbuf);
pcap_create() is used to create a packet capture handle to look at packets on the network. source is a string that specifies the network device to open; on Linux systems with 2.2 or later kernels, a source argument of "any" or NULL can be used to capture packets from all interfaces.
The returned handle must be activated with pcap_activate() before packets can be captured with it; options for the capture, such as promiscuous mode, can be set on the handle before activating it.
pcap_create() returns a pcap_t * on success and NULL on failure. If NULL is returned, errbuf is filled in with an appropriate error message. errbuf is assumed to be able to hold at least PCAP_ERRBUF_SIZE chars.