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 protocol 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.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 processing 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 compatibility will be enabled until the v1
             'Older Version Querier Present' timer expires.  This sysctl is normally enabled by
             default.

SEE ALSO

     netstat(1), sourcefilter(3), icmp6(4), inet(4), multicast(4), ifmcstat(8)

HISTORY

     The mld manual page appeared in FreeBSD 8.0.