| GETIFADDRS(3) | Library Functions Manual | GETIFADDRS(3) | 
getifaddrs, freeifaddrs —
#include <sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>
int
  
  getifaddrs(struct
    ifaddrs **ifap);
void
  
  freeifaddrs(struct
    ifaddrs *ifp);
getifaddrs() function stores a reference to a linked
  list of the network interfaces on the local machine in the memory referenced
  by ifap. The list consists of
  ifaddrs structures, as defined in the include file
  <ifaddrs.h>. The
  ifaddrs structure contains at least the following
  entries:
    struct ifaddrs   *ifa_next;         /* Pointer to next struct */
    char             *ifa_name;         /* Interface name */
    unsigned int      ifa_flags;        /* Interface flags */
    struct sockaddr  *ifa_addr;         /* Interface address */
    struct sockaddr  *ifa_netmask;      /* Interface netmask */
    struct sockaddr  *ifa_broadaddr;    /* Interface broadcast address */
    struct sockaddr  *ifa_dstaddr;      /* P2P interface destination */
    void             *ifa_data;		/* Address specific data */
    unsigned int      ifa_addrflags;    /* Address flags */
The ifa_next field contains a pointer to
    the next structure on the list. This field is NULL
    in last structure on the list.
The ifa_name field contains the interface
    name.
The ifa_flags field contains the interface
    flags, as set by ifconfig(8)
    utility.
The ifa_addr field references either the
    address of the interface or the link level address of the interface, if one
    exists, otherwise it is NULL. (The
    sa_family field of the
    ifa_addr field should be consulted to determine the
    format of the ifa_addr address.)
The ifa_netmask field references the
    netmask associated with ifa_addr, if one is set,
    otherwise it is NULL.
The ifa_broadaddr field, which should only
    be referenced for non-P2P interfaces, references the broadcast address
    associated with ifa_addr, if one exists, otherwise
    it is NULL.
The ifa_dstaddr field references the
    destination address on a P2P interface, if one exists, otherwise it is
    NULL.
The ifa_data field references address
    family specific data. For AF_LINK addresses it
    contains a pointer to the struct if_data (as defined
    in include file ⟨net/if.h⟩) which
    contains various interface attributes and statistics. For all other address
    families, it is NULL.
The ifa_addrflags field contains the
    address flags, which are specific to the address family.
The data returned by getifaddrs() is
    dynamically allocated and should be freed using
    freeifaddrs() when no longer needed.
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <ifaddrs.h>
#include <util.h>
#include <err.h>
#include <stdlib.h>
int
main(int argc, char *argv[])
{
	struct ifaddrs *ifa, *a;
	if (getifaddrs(&ifa) == -1)
		err(EXIT_FAILURE, "getifaddrs");
	for (a = ifa; a; a = a->ifa_next) {
		char buf[1024];
		sockaddr_snprintf(buf, sizeof(buf), "%f %a",
		    a->ifa_addr);
		printf("%s %x %s\n", a->ifa_name, a->ifa_flags, buf);
	}
	freeifaddrs(ifa);
	return EXIT_SUCCESS;
}
getifaddrs() may fail and set
  errno for any of the errors specified for the library
  routines ioctl(2),
  socket(2),
  malloc(3) or
  sysctl(3).
getifaddrs implementation first appeared in
  BSD/OS.
ifa_addrflags was added in
    NetBSD 8.0.
<net/if.h> and
  <ifaddrs.h> are being
  included, <net/if.h>
  must be included before
  <ifaddrs.h>.
| September 15, 2016 | NetBSD 10.0 |