MLD(4)							   BSD Kernel Interfaces Manual 						    MLD(4)

NAME

     mld -- Multicast Listener Discovery Protocol

SYNOPSIS

     #include <sys/types.h>
     #include <sys/socket.h>
     #include <netinet/in.h>
     #include <netinet/in_systm.h>
     #include <netinet/ip6.h>
     #include <netinet/icmp6.h>
     #include <netinet6/mld6.h>

     int
     socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);

DESCRIPTION

     MLD is a control plane protocol used by IPv6 hosts and routers to propagate multicast group membership information.  Normally this protocol
     is not used directly, except by the kernel itself, in response to multicast membership requests by user applications.  Multicast routing pro-
     tocol daemons may open a raw socket to directly interact with mld and receive membership reports.

     As of FreeBSD 8.0, MLD version 2 is implemented.  This adds support for Source-Specific Multicast (SSM), whereby applications may communicate
     to upstream multicast routers that they are only interested in receiving multicast streams from particular sources.  The retransmission of
     state-change reports adds some robustness to the protocol.

SYSCTL VARIABLES

     net.inet6.mld.stats
	     This opaque read-only variable exposes the stack-wide MLDv2 protocol statistics to netstat(1).

     net.inet6.mld.ifinfo
	     This opaque read-only variable exposes the per-link MLDv2 status to ifmcstat(8).

     net.inet6.mld.gsrdelay
	     This variable specifies the time threshold, in seconds, for processing Group-and-Source Specific Queries (GSR).  As GSR query pro-
	     cessing requires maintaining state on the host, it may cause memory to be allocated, and is therefore a potential attack point for
	     Denial-of-Service (DoS).  If more than one GSR query is received within this threshold, it will be dropped, to mitigate the potential
	     for DoS.

     net.inet6.mld.v1enable
	     If this variable is non-zero, then MLDv1 membership queries (and host reports) will be processed by this host, and backwards compati-
	     bility will be enabled until the v1 'Older Version Querier Present' timer expires.  This sysctl is normally enabled by default.

SEE ALSO

     ifmcstat(8), inet(4), multicast(4), netstat(1), sourcefilter(3)

HISTORY

     The mld manual page appeared in FreeBSD 8.0.

BSD
								   May 27, 2009 							       BSD