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 March 9, 2009 31.Dt IGMP 4 32.Os 33.Sh NAME 34.Nm igmp 35.Nd Internet Group Management 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/ip.h 42.In netinet/igmp.h 43.Ft int 44.Fn socket AF_INET SOCK_RAW IPPROTO_IGMP 45.Sh DESCRIPTION 46.Tn IGMP 47is a control plane protocol used by IPv4 hosts and routers to 48propagate multicast group membership information. 49Normally this protocol is not used directly, except by the kernel 50itself, in response to multicast membership requests by user 51applications. 52Routing protocols may open a raw socket to directly interact with 53.Nm . 54.Pp 55As of 56.Fx 8.0 , 57IGMP version 3 is implemented. 58This adds support for Source-Specific Multicast (SSM), whereby 59applications may communicate to upstream multicast routers that 60they are only interested in receiving multicast streams from 61particular sources. 62.\" 63.Sh SYSCTL VARIABLES 64.Pp 65.Bl -tag -width indent 66.\" 67.It net.inet.igmp.stats 68This opaque read-only variable exposes the stack-wide IGMPv3 69protocol statistics to 70.Xr netstat 1 . 71.\" 72.It net.inet.igmp.ifinfo 73This opaque read-only variable exposes the per-link IGMPv3 status to 74.Xr ifmcstat 8 . 75.\" 76.It net.inet.igmp.gsrdelay 77This variable specifies the time threshold, in seconds, for processing 78Group-and-Source Specific Queries (GSR). 79As GSR query processing requires maintaining state on the host, 80it may cause memory to be allocated, and is therefore a potential 81attack point for Denial-of-Service (DoS). 82If more than one GSR query is received within this threshold, 83it will be dropped, to mitigate the potential for DoS. 84.\" 85.It net.inet.igmp.default_version 86This variable controls the default version of IGMP to be used on all links. 87This sysctl is normally set to 3 by default. 88.\" 89.It net.inet.igmp.legacysupp 90If this variable is non-zero, then IGMP v1 and v2 membership reports 91received on a link will be allowed to suppress the IGMP v3 state-change 92reports which would otherwise be issued by this host. 93This sysctl is normally enabled by default. 94.\" 95.It net.inet.igmp.v2enable 96If this variable is non-zero, then IGMP v2 membership queries will be 97processed by this host, and backwards compatibility will be enabled 98until the v2 'Old Querier Present' timer expires. 99This sysctl is normally enabled by default. 100.\" 101.It net.inet.igmp.v1enable 102If this variable is non-zero, then IGMP v1 membership queries will be 103processed by this host, and backwards compatibility will be enabled 104until the v1 'Old Querier Present' timer expires. 105This sysctl is normally enabled by default. 106.\" 107.It net.inet.igmp.sendlocal 108If this variable is non-zero, then IGMP state-changes for groups in 109the 224.0.0.0/24 link-scope prefix will be issued. 110This behaviour is recommended if deploying 111.Fx 112in a network environment with layer 2 devices which snoop IGMP traffic 113to mitigate multicast propagation throughout the network. 114This sysctl is normally enabled by default. 115.\" 116.It net.inet.igmp.sendra 117If this variable is non-zero, then IGMP v2 and v3 reports will contain 118the IP Router Alert option. 119This sysctl is normally enabled by default. 120.\" 121.It net.inet.igmp.recvifkludge 122If this variable is non-zero, then received IGMP reports which contain 1230.0.0.0 as their source will be rewritten to contain the subnet address. 124This is useful when there are hosts on-link which have not yet been 125configured with a primary IPv4 address. 126This sysctl is normally enabled by default. 127.\" 128.El 129.Sh SEE ALSO 130.Xr ifmcstat 8 , 131.Xr inet 4 , 132.Xr multicast 4 , 133.Xr netstat 1 , 134.Xr sourcefilter 3 135.Sh HISTORY 136The 137.Nm 138manual page re-appeared in 139.Fx 8.0 . 140