1.\" 2.\" Copyright (c) 2009 Bruce Simpson. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the project nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd April 8, 2013 29.Dt MLD 4 30.Os 31.Sh NAME 32.Nm mld 33.Nd Multicast Listener Discovery Protocol 34.Sh SYNOPSIS 35.In sys/types.h 36.In sys/socket.h 37.In netinet/in.h 38.In netinet/in_systm.h 39.In netinet/ip6.h 40.In netinet/icmp6.h 41.In netinet6/mld6.h 42.Ft int 43.Fn socket AF_INET6 SOCK_RAW IPPROTO_ICMPV6 44.Sh DESCRIPTION 45.Tn MLD 46is a control plane protocol used by IPv6 hosts and routers to 47propagate multicast group membership information. 48Normally this protocol is not used directly, except by the kernel 49itself, in response to multicast membership requests by user 50applications. 51Multicast routing protocol daemons may open a raw socket to directly 52interact with 53.Nm 54and receive membership reports. 55.Pp 56As of 57.Fx 8.0 , 58MLD version 2 is implemented. 59This adds support for Source-Specific Multicast (SSM), whereby 60applications may communicate to upstream multicast routers that 61they are only interested in receiving multicast streams from 62particular sources. 63The retransmission of state-change reports adds some robustness 64to the protocol. 65.\" 66.Sh SYSCTL VARIABLES 67.Bl -tag -width indent 68.\" 69.It net.inet6.mld.ifinfo 70This opaque read-only variable exposes the per-link MLDv2 status to 71.Xr ifmcstat 8 . 72.\" 73.It net.inet6.mld.gsrdelay 74This variable specifies the time threshold, in seconds, for processing 75Group-and-Source Specific Queries (GSR). 76As GSR query processing requires maintaining state on the host, 77it may cause memory to be allocated, and is therefore a potential 78attack point for Denial-of-Service (DoS). 79If more than one GSR query is received within this threshold, 80it will be dropped, to mitigate the potential for DoS. 81.\" 82.It net.inet6.mld.v1enable 83If this variable is non-zero, then MLDv1 membership queries (and host 84reports) will be processed by this host, and backwards compatibility 85will be enabled until the v1 'Older Version Querier Present' timer expires. 86This sysctl is normally enabled by default. 87.\" 88.El 89.Sh SEE ALSO 90.Xr netstat 1 , 91.Xr sourcefilter 3 , 92.Xr icmp6 4 , 93.Xr inet 4 , 94.Xr multicast 4 , 95.Xr ifmcstat 8 96.Sh HISTORY 97The 98.Nm 99manual page appeared in 100.Fx 8.0 . 101