pcap_lookupnet(3PCAP) man page

Updated: 13 March 2024 • View in plain textReturn to Main Contents

This man page documents libpcap version 1.11.0-PRE-GIT (see also: 1.10.4, 1.10.2, 1.10.1, 1.10.0, 1.9.1, 1.8.1, 1.7.4, 1.6.2, 1.5.3).

Your system may have a different version installed, possibly with some local modifications. To achieve the best results, please make sure this version of this man page suits your needs. If necessary, try to look for a different version on this web site or in the man pages available in your installation.


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


#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);


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. 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.


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.




This HTML man page was generated at 13:30:15 GMT, March 13, 2024 from a source man page in "The Tcpdump Group" git repositories using man2html and other tools.