139 lines
5.0 KiB
Groff
139 lines
5.0 KiB
Groff
.\"
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.\" Copyright (c) 2009 Bruce Simpson.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the project nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd March 9, 2009
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.Dt IGMP 4
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.Os
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.Sh NAME
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.Nm igmp
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.Nd Internet Group Management Protocol
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/socket.h
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.In netinet/in.h
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.In netinet/in_systm.h
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.In netinet/ip.h
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.In netinet/igmp.h
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.Ft int
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.Fn socket AF_INET SOCK_RAW IPPROTO_IGMP
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.Sh DESCRIPTION
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.Tn IGMP
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is a control plane protocol used by IPv4 hosts and routers to
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propagate multicast group membership information.
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Normally this protocol is not used directly, except by the kernel
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itself, in response to multicast membership requests by user
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applications.
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Routing protocols may open a raw socket to directly interact with
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.Nm .
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.Pp
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As of
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.Fx 8.0 ,
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IGMP version 3 is implemented.
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This adds support for Source-Specific Multicast (SSM), whereby
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applications may communicate to upstream multicast routers that
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they are only interested in receiving multicast streams from
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particular sources.
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.\"
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.Sh SYSCTL VARIABLES
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.Bl -tag -width indent
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.\"
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.It net.inet.igmp.stats
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This opaque read-only variable exposes the stack-wide IGMPv3
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protocol statistics to
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.Xr netstat 1 .
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.\"
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.It net.inet.igmp.ifinfo
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This opaque read-only variable exposes the per-link IGMPv3 status to
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.Xr ifmcstat 8 .
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.\"
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.It net.inet.igmp.gsrdelay
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This variable specifies the time threshold, in seconds, for processing
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Group-and-Source Specific Queries (GSR).
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As GSR query processing requires maintaining state on the host,
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it may cause memory to be allocated, and is therefore a potential
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attack point for Denial-of-Service (DoS).
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If more than one GSR query is received within this threshold,
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it will be dropped, to mitigate the potential for DoS.
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.\"
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.It net.inet.igmp.default_version
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This variable controls the default version of IGMP to be used on all links.
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This sysctl is normally set to 3 by default.
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.\"
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.It net.inet.igmp.legacysupp
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If this variable is non-zero, then IGMP v1 and v2 membership reports
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received on a link will be allowed to suppress the IGMP v3 state-change
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reports which would otherwise be issued by this host.
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This sysctl is normally enabled by default.
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.\"
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.It net.inet.igmp.v2enable
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If this variable is non-zero, then IGMP v2 membership queries will be
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processed by this host, and backwards compatibility will be enabled
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until the v2 'Old Querier Present' timer expires.
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This sysctl is normally enabled by default.
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.\"
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.It net.inet.igmp.v1enable
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If this variable is non-zero, then IGMP v1 membership queries will be
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processed by this host, and backwards compatibility will be enabled
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until the v1 'Old Querier Present' timer expires.
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This sysctl is normally enabled by default.
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.\"
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.It net.inet.igmp.sendlocal
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If this variable is non-zero, then IGMP state-changes for groups in
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the 224.0.0.0/24 link-scope prefix will be issued.
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This behaviour is recommended if deploying
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.Fx
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in a network environment with layer 2 devices which snoop IGMP traffic
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to mitigate multicast propagation throughout the network.
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This sysctl is normally enabled by default.
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.\"
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.It net.inet.igmp.sendra
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If this variable is non-zero, then IGMP v2 and v3 reports will contain
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the IP Router Alert option.
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This sysctl is normally enabled by default.
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.\"
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.It net.inet.igmp.recvifkludge
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If this variable is non-zero, then received IGMP reports which contain
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0.0.0.0 as their source will be rewritten to contain the subnet address.
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This is useful when there are hosts on-link which have not yet been
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configured with a primary IPv4 address.
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This sysctl is normally enabled by default.
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.\"
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.El
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.Sh SEE ALSO
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.Xr netstat 1 ,
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.Xr sourcefilter 3 ,
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.Xr inet 4 ,
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.Xr multicast 4 ,
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.Xr ifmcstat 8
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.Sh HISTORY
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The
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.Nm
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manual page re-appeared in
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.Fx 8.0 .
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