Updated: 2025/Nov/16

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PCAP_LOOKUPNET(3)          Library Functions Manual          PCAP_LOOKUPNET(3)

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.  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(3) 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(3)

                                 13 March 2024               PCAP_LOOKUPNET(3)