Get multicast group memberships.

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

int
getifmaddrs();

void
freeifmaddrs();

Description

The getifmaddrs() 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 */

ifma_next

Contains a pointer to the next structure on the list. This field is NULL in last structure on the list.

ifma_name

References an AF_LINK address structure, containing the name of the interface where the membership exists.

ifma_addr

References the address that this membership is for.

ifma_lladdr

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 getifmaddrs() is dynamically allocated and should be freed using freeifmaddrs() when no longer needed.

Bugs

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

Return Values

The getifmaddrs() function returns the value 0 if successful; otherwisethe 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 or sysctl.

Requirements