.\" Copyright (c) 2003 Bruce M. Simpson. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\"
.\" THIS SOFTWARE IS PROVIDED BY Bruce M. Simpson ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL Bruce M. Simpson BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd May 21, 2013
.Dt GETIFMADDRS 3
.Os
.Sh NAME
.Nm getifmaddrs
.Nd get multicast group memberships
.Sh SYNOPSIS
.In ifaddrs.h
.Ft int
.Fn getifmaddrs "struct ifmaddrs **ifmap"
.Ft void
.Fn freeifmaddrs "struct ifmaddrs *ifmp"
.Sh DESCRIPTION
The
.Fn getifmaddrs
function stores a reference to a linked list of the multicast memberships
on the local machine in the memory referenced by
.Fa ifmap .
The list consists of
.Vt ifmaddrs
structures, as defined in the include file
.In ifaddrs.h .
The
.Vt ifmaddrs
structure contains at least the following entries:
.Bd -literal
    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 */
.Ed
.Pp
The
.Va ifma_next
field contains a pointer to the next structure on the list.
This field is
.Dv NULL
in last structure on the list.
.Pp
The
.Va ifma_name
field references an
.Dv AF_LINK
address structure, containing the name of the
interface where the membership exists.
.Pp
The
.Va ifma_addr
references the address that this membership is for.
.Pp
The
.Va ifma_lladdr
field references a link-layer translation for the protocol-level address in
.Va ifma_addr ,
if one is set, otherwise it is
.Dv NULL .
.Pp
The data returned by
.Fn getifmaddrs
is dynamically allocated and should be freed using
.Fn freeifmaddrs
when no longer needed.
.Sh RETURN VALUES
.Rv -std getifmaddrs
.Sh ERRORS
The
.Fn getifmaddrs
may fail and set
.Va errno
for any of the errors specified for the library routines
.Xr malloc 3
or
.Xr sysctl 3 .
.Sh SEE ALSO
.Xr sysctl 3 ,
.Xr networking 4 ,
.Xr ifconfig 8
.Sh HISTORY
The
.Fn getifmaddrs
function first appeared in
.Fx 5.2 .
.Sh BUGS
If both
.In net/if.h
and
.In ifaddrs.h
are being included,
.In net/if.h
.Em must
be included before
.In ifaddrs.h .