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<table class="head">
<tr>
<td class="head-ltitle">IGMP(4)</td>
<td class="head-vol">Device Drivers Manual</td>
<td class="head-rtitle">IGMP(4)</td>
</tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">igmp</code> — <span class="Nd">Internet
Group Management Protocol</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp"><code class="In">#include
<<a class="In">sys/types.h</a>></code>
<br/>
<code class="In">#include <<a class="In">sys/socket.h</a>></code>
<br/>
<code class="In">#include <<a class="In">netinet/in.h</a>></code>
<br/>
<code class="In">#include <<a class="In">netinet/in_systm.h</a>></code>
<br/>
<code class="In">#include <<a class="In">netinet/ip.h</a>></code>
<br/>
<code class="In">#include <<a class="In">netinet/igmp.h</a>></code></p>
<p class="Pp"><var class="Ft">int</var>
<br/>
<code class="Fn">socket</code>(<var class="Fa" style="white-space: nowrap;">AF_INET</var>,
<var class="Fa" style="white-space: nowrap;">SOCK_RAW</var>,
<var class="Fa" style="white-space: nowrap;">IPPROTO_IGMP</var>);</p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">IGMP is a control plane protocol used by IPv4 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. Routing protocols may open a raw
socket to directly interact with <code class="Nm">igmp</code>.</p>
<p class="Pp">As of <span class="Ux">FreeBSD 8.0</span>, IGMP version 3 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.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYSCTL_VARIABLES"><a class="permalink" href="#SYSCTL_VARIABLES">SYSCTL
VARIABLES</a></h1>
<dl class="Bl-tag">
<dt>net.inet.igmp.stats</dt>
<dd>This opaque read-only variable exposes the stack-wide IGMPv3 protocol
statistics to <a class="Xr">netstat(1)</a>.</dd>
<dt>net.inet.igmp.ifinfo</dt>
<dd>This opaque read-only variable exposes the per-link IGMPv3 status to
<a class="Xr">ifmcstat(8)</a>.</dd>
<dt>net.inet.igmp.gsrdelay</dt>
<dd>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.</dd>
<dt>net.inet.igmp.default_version</dt>
<dd>This variable controls the default version of IGMP to be used on all
links. This sysctl is normally set to 3 by default.</dd>
<dt>net.inet.igmp.legacysupp</dt>
<dd>If this variable is non-zero, then IGMP v1 and v2 membership reports
received on a link will be allowed to suppress the IGMP v3 state-change
reports which would otherwise be issued by this host. This sysctl is
normally enabled by default.</dd>
<dt>net.inet.igmp.v2enable</dt>
<dd>If this variable is non-zero, then IGMP v2 membership queries will be
processed by this host, and backwards compatibility will be enabled until
the v2 'Old Querier Present' timer expires. This sysctl is normally
enabled by default.</dd>
<dt>net.inet.igmp.v1enable</dt>
<dd>If this variable is non-zero, then IGMP v1 membership queries will be
processed by this host, and backwards compatibility will be enabled until
the v1 'Old Querier Present' timer expires. This sysctl is normally
enabled by default.</dd>
<dt>net.inet.igmp.sendlocal</dt>
<dd>If this variable is non-zero, then IGMP state-changes for groups in the
224.0.0.0/24 link-scope prefix will be issued. This behaviour is
recommended if deploying <span class="Ux">FreeBSD</span> in a network
environment with layer 2 devices which snoop IGMP traffic to mitigate
multicast propagation throughout the network. This sysctl is normally
enabled by default.</dd>
<dt>net.inet.igmp.sendra</dt>
<dd>If this variable is non-zero, then IGMP v2 and v3 reports will contain the
IP Router Alert option. This sysctl is normally enabled by default.</dd>
<dt>net.inet.igmp.recvifkludge</dt>
<dd>If this variable is non-zero, then received IGMP reports which contain
0.0.0.0 as their source will be rewritten to contain the subnet address.
This is useful when there are hosts on-link which have not yet been
configured with a primary IPv4 address. This sysctl is normally enabled by
default.</dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
ALSO</a></h1>
<p class="Pp"><a class="Xr">netstat(1)</a>, <a class="Xr">sourcefilter(3)</a>,
<a class="Xr">inet(4)</a>, <a class="Xr">multicast(4)</a>,
<a class="Xr">ifmcstat(8)</a></p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">The <code class="Nm">igmp</code> manual page re-appeared in
<span class="Ux">FreeBSD 8.0</span>.</p>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">March 9, 2009</td>
<td class="foot-os">FreeBSD 15.0</td>
</tr>
</table>
|
