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.\" $FreeBSD$ 29.\" 30.Dd May 27, 2009 31.Dt MLD 4 32.Os 33.Sh NAME 34.Nm mld 35.Nd Multicast Listener Discovery Protocol 36.Sh SYNOPSIS 37.In sys/types.h 38.In sys/socket.h 39.In netinet/in.h 40.In netinet/in_systm.h 41.In netinet/ip6.h 42.In netinet/icmp6.h 43.In netinet6/mld6.h 44.Ft int 45.Fn socket AF_INET6 SOCK_RAW IPPROTO_ICMPV6 46.Sh DESCRIPTION 47.Tn MLD 48is a control plane protocol used by IPv6 hosts and routers to 49propagate multicast group membership information. 50Normally this protocol is not used directly, except by the kernel 51itself, in response to multicast membership requests by user 52applications. 53Multicast routing protocol daemons may open a raw socket to directly 54interact with 55.Nm 56and receive membership reports. 57.Pp 58As of 59.Fx 8.0 , 60MLD version 2 is implemented. 61This adds support for Source-Specific Multicast (SSM), whereby 62applications may communicate to upstream multicast routers that 63they are only interested in receiving multicast streams from 64particular sources. 65The retransmission of state-change reports adds some robustness 66to the protocol. 67.\" 68.Sh SYSCTL VARIABLES 69.Pp 70.Bl -tag -width indent 71.\" 72.It net.inet6.mld.stats 73This opaque read-only variable exposes the stack-wide MLDv2 74protocol statistics to 75.Xr netstat 1 . 76.\" 77.It net.inet6.mld.ifinfo 78This opaque read-only variable exposes the per-link MLDv2 status to 79.Xr ifmcstat 8 . 80.\" 81.It net.inet6.mld.gsrdelay 82This variable specifies the time threshold, in seconds, for processing 83Group-and-Source Specific Queries (GSR). 84As GSR query processing requires maintaining state on the host, 85it may cause memory to be allocated, and is therefore a potential 86attack point for Denial-of-Service (DoS). 87If more than one GSR query is received within this threshold, 88it will be dropped, to mitigate the potential for DoS. 89.\" 90.It net.inet6.mld.v1enable 91If this variable is non-zero, then MLDv1 membership queries (and host 92reports) will be processed by this host, and backwards compatibility 93will be enabled until the v1 'Older Version Querier Present' timer expires. 94This sysctl is normally enabled by default. 95.\" 96.El 97.Sh SEE ALSO 98.Xr ifmcstat 8 , 99.Xr inet 4 , 100.Xr multicast 4 , 101.Xr netstat 1 , 102.Xr sourcefilter 3 103.Sh HISTORY 104The 105.Nm 106manual page appeared in 107.Fx 8.0 . 108