GETIFMADDRS(3) Library Functions Manual GETIFMADDRS(3)

getifmaddrs — get multicast group memberships

#include <sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>

int
getifmaddrs(struct ifmaddrs **ifmap);

void
freeifmaddrs(struct ifmaddrs *ifmp);

The () function stores a reference to a linked list of the multicast memberships on the local machine in the memory referenced by ifmap. The list consists of ifmaddrs structures, as defined in the include file <ifaddrs.h>. The ifmaddrs structure contains at least the following entries:

    struct ifmaddrs   *ifma_next;     /* Pointer to next struct */
    struct sockaddr   *ifma_name;     /* Interface name (AF_LINK) */
    struct sockaddr   *ifma_addr;     /* Multicast address */
    struct sockaddr   *ifma_lladdr;   /* Link-layer translation, if any */

The ifma_next field contains a pointer to the next structure on the list. This field is NULL in last structure on the list.

The ifma_name field references an AF_LINK address structure, containing the name of the interface where the membership exists.

The ifma_addr references the address that this membership is for.

The ifma_lladdr field references a link-layer translation for the protocol-level address in ifma_addr, if one is set, otherwise it is NULL.

The data returned by () is dynamically allocated and should be freed using () when no longer needed.

The getifmaddrs() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

The getifmaddrs() may fail and set errno for any of the errors specified for the library routines malloc(3) or sysctl(3).

sysctl(3), networking(4), ifconfig(8)

The getifmaddrs() function first appeared in FreeBSD 5.2.

If both <net/if.h> and <ifaddrs.h> are being included, <net/if.h> be included before <ifaddrs.h>.

November 14, 2003 macOS 15.2