pcap_lookupnet(3PCAP) man page

pcap_lookupnet(3PCAP) man page

Updated: 31 January 2025 • View in plain text • Return to Main Contents

NAME

pcap_lookupnet - find the IPv4 network number and netmask for a device

SYNOPSIS

#include <pcap/pcap.h>

char errbuf[PCAP_ERRBUF_SIZE];

int pcap_lookupnet(const char *device, bpf_u_int32 *netp,
    bpf_u_int32 *maskp, char *errbuf);

DESCRIPTION

pcap_lookupnet() is used to determine the IPv4 network number and mask associated with the network device device. Both netp and maskp are bpf_u_int32 pointers, on success both values will be set in network byte order. errbuf is a buffer large enough to hold at least PCAP_ERRBUF_SIZE chars.

This function is not available on Windows. It supports neither IPv6 nor multiple IPv4 addresses per interface, which obviously is not practical in modern networks. See pcap_findalldevs(3PCAP) for a more elaborate solution to the problem.

RETURN VALUE

pcap_lookupnet() returns 0 on success and PCAP_ERROR on failure. If PCAP_ERROR is returned, errbuf is filled in with an appropriate error message.

SEE ALSO

pcap(3PCAP)

COLOPHON

This HTML man page was generated at 15:15:21 GMT, September 13, 2026 from a source man page in “The Tcpdump Group” git repositories using man2html and other tools.