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Date: Thu, 14 Oct 2004 17:44:57 +0400
From: Grigory Klyuchnikov <grn@ispras.ru>
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cc: freebsd-net@freebsd.org
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Subject: Get multicast addresses from interface
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Hello,

How can a user process get IPv6 multicast addresses of ethernet
interfaces? I have FreeBSD 5.2.1 and get interface addresses
via ioctl(SIOCGIFCONF) or sysctl(witch NET_RT_IFLIST),
but all returned addresses are unicast.

In net/if.h there is a struct ifma_msghdr:

/*
  * Message format for use in obtaining information about multicast addresses
  * from the routing socket
  */
struct ifma_msghdr {
	u_short	ifmam_msglen;	/* to skip over non-understood messages */
	u_char	ifmam_version;	/* future binary compatibility */
	u_char	ifmam_type;	/* message type */
	int	ifmam_addrs;	/* like rtm_addrs */
	int	ifmam_flags;	/* value of ifa_flags */
	u_short	ifmam_index;	/* index for associated ifp */
};


How it may be used?

Regards,
Grigory Klyuchnikov.