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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.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
             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

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

HISTORY

     The mld manual page appeared in FreeBSD 8.0.