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<table class="head">
<tr>
<td class="head-ltitle">RTENTRY(9)</td>
<td class="head-vol">Kernel Developer's Manual</td>
<td class="head-rtitle">RTENTRY(9)</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">rtentry</code> —
<span class="Nd">structure of an entry in the kernel routing
table</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">net/route.h</a>></code></p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">The kernel provides a common mechanism by which all protocols can
store and retrieve entries from a central table of routes. Parts of this
mechanism are also used to interact with user-level processes by means of a
socket in the <a class="Xr">route(4)</a> pseudo-protocol family. The
<code class="In"><<a class="In">net/route.h</a>></code> header file
defines the structures and manifest constants used in this facility.</p>
<p class="Pp">The basic structure of a route is defined by
<var class="Vt">struct rtentry</var>, which includes the following
fields:</p>
<div class="Bd-indent">
<dl class="Bl-tag">
<dt id="rt_key"><var class="Vt">struct radix_node rt_nodes[2]</var>;</dt>
<dd>Glue used by the radix-tree routines. These members also include in their
substructure the key (i.e., destination address) and mask used when the
route was created. The
<a class="permalink" href="#rt_key"><code class="Fn">rt_key</code></a>(<var class="Fa">rt</var>)
and
<a class="permalink" href="#rt_mask"><code class="Fn" id="rt_mask">rt_mask</code></a>(<var class="Fa">rt</var>)
macros can be used to extract this information (in the form of a
<var class="Vt">struct sockaddr *</var>) given a <var class="Vt">struct
rtentry *</var>.</dd>
<dt><var class="Vt">struct sockaddr *rt_gateway</var>;</dt>
<dd>The “target” of the route, which can either represent a
destination in its own right (some protocols will put a link-layer address
here), or some intermediate stop on the way to that destination (if the
<code class="Dv">RTF_GATEWAY</code> flag is set).</dd>
<dt id="rtfree"><var class="Vt">int rt_flags</var>;</dt>
<dd>See below. If the <code class="Dv">RTF_UP</code> flag is not present, the
<a class="permalink" href="#rtfree"><code class="Fn">rtfree</code></a>()
function will delete the route from the radix tree when the last reference
drops.</dd>
<dt><var class="Vt">int rt_refcnt</var>;</dt>
<dd>Route entries are reference-counted; this field indicates the number of
external (to the radix tree) references.</dd>
<dt><var class="Vt">struct ifnet *rt_ifp</var>;</dt>
<dd style="width: auto;"> </dd>
<dt><var class="Vt">struct ifaddr *rt_ifa</var>;</dt>
<dd>These two fields represent the “answer”, as it were, to the
question posed by a route lookup; that is, they name the interface and
interface address to be used in sending a packet to the destination or set
of destinations which this route represents.</dd>
<dt><var class="Vt">u_long rt_mtu</var>;</dt>
<dd>See description of rmx_mtu below.</dd>
<dt><var class="Vt">u_long rt_weight</var>;</dt>
<dd>See description of rmx_weight below.</dd>
<dt><var class="Vt">u_long rt_expire</var>;</dt>
<dd>See description of rmx_expire below.</dd>
<dt><var class="Vt">counter64_t rt_pksent</var>;</dt>
<dd>See description of rmx_pksent below.</dd>
<dt><var class="Vt">struct rtentry *rt_gwroute</var>;</dt>
<dd>This member is a reference to a route whose destination is
<var class="Va">rt_gateway</var>. It is only used for
<code class="Dv">RTF_GATEWAY</code> routes.</dd>
<dt><var class="Vt">struct mtx rt_mtx</var>;</dt>
<dd>Mutex to lock this routing entry.</dd>
</dl>
</div>
<p class="Pp">The following flag bits are defined:</p>
<div class="Bd-indent">
<dl class="Bl-tag Bl-compact">
<dt id="RTF_UP"><a class="permalink" href="#RTF_UP"><code class="Dv">RTF_UP</code></a></dt>
<dd>The route is not deleted.</dd>
<dt id="RTF_GATEWAY"><a class="permalink" href="#RTF_GATEWAY"><code class="Dv">RTF_GATEWAY</code></a></dt>
<dd>The route points to an intermediate destination and not the ultimate
recipient; the <var class="Va">rt_gateway</var> and
<var class="Va">rt_gwroute</var> fields name that destination.</dd>
<dt id="RTF_HOST"><a class="permalink" href="#RTF_HOST"><code class="Dv">RTF_HOST</code></a></dt>
<dd>This is a host route.</dd>
<dt id="RTF_REJECT"><a class="permalink" href="#RTF_REJECT"><code class="Dv">RTF_REJECT</code></a></dt>
<dd>The destination is presently unreachable. This should result in an
<code class="Er">EHOSTUNREACH</code> error from output routines.</dd>
<dt id="RTF_DYNAMIC"><a class="permalink" href="#RTF_DYNAMIC"><code class="Dv">RTF_DYNAMIC</code></a></dt>
<dd>This route was created dynamically by
<a class="permalink" href="#rtredirect"><code class="Fn" id="rtredirect">rtredirect</code></a>().</dd>
<dt id="RTF_MODIFIED"><a class="permalink" href="#RTF_MODIFIED"><code class="Dv">RTF_MODIFIED</code></a></dt>
<dd>This route was modified by <code class="Fn">rtredirect</code>().</dd>
<dt id="RTF_DONE"><a class="permalink" href="#RTF_DONE"><code class="Dv">RTF_DONE</code></a></dt>
<dd>Used only in the <a class="Xr">route(4)</a> protocol, indicating that the
request was executed.</dd>
<dt id="RTF_XRESOLVE"><a class="permalink" href="#RTF_XRESOLVE"><code class="Dv">RTF_XRESOLVE</code></a></dt>
<dd>When this route is returned as a result of a lookup, send a report on the
<a class="Xr">route(4)</a> interface requesting that an external process
perform resolution for this route.</dd>
<dt id="RTF_STATIC"><a class="permalink" href="#RTF_STATIC"><code class="Dv">RTF_STATIC</code></a></dt>
<dd>Indicates that this route was manually added by means of the
<a class="Xr">route(8)</a> command.</dd>
<dt id="RTF_BLACKHOLE"><a class="permalink" href="#RTF_BLACKHOLE"><code class="Dv">RTF_BLACKHOLE</code></a></dt>
<dd>Requests that output sent via this route be discarded.</dd>
<dt id="RTF_PROTO1"><a class="permalink" href="#RTF_PROTO1"><code class="Dv">RTF_PROTO1</code></a></dt>
<dd style="width: auto;"> </dd>
<dt id="RTF_PROTO2"><a class="permalink" href="#RTF_PROTO2"><code class="Dv">RTF_PROTO2</code></a></dt>
<dd style="width: auto;"> </dd>
<dt id="RTF_PROTO3"><a class="permalink" href="#RTF_PROTO3"><code class="Dv">RTF_PROTO3</code></a></dt>
<dd>Protocol-specific.</dd>
<dt id="RTF_PINNED"><a class="permalink" href="#RTF_PINNED"><code class="Dv">RTF_PINNED</code></a></dt>
<dd>Indicates that this route is immutable to a routing protocol.</dd>
<dt id="RTF_LOCAL"><a class="permalink" href="#RTF_LOCAL"><code class="Dv">RTF_LOCAL</code></a></dt>
<dd>Indicates that the destination of this route is an address configured as
belonging to this system.</dd>
<dt id="RTF_BROADCAST"><a class="permalink" href="#RTF_BROADCAST"><code class="Dv">RTF_BROADCAST</code></a></dt>
<dd>Indicates that the destination is a broadcast address.</dd>
<dt id="RTF_MULTICAST"><a class="permalink" href="#RTF_MULTICAST"><code class="Dv">RTF_MULTICAST</code></a></dt>
<dd>Indicates that the destination is a multicast address.</dd>
</dl>
</div>
<p class="Pp">Several metrics are supplied in <var class="Vt">struct
rt_metrics</var> passed with routing control messages via
<a class="Xr">route(4)</a> API. Currently only
<var class="Vt">rmx_mtu</var>, <var class="Vt">rmx_expire</var>, and
<var class="Vt">rmx_pksent</var> metrics are supplied. All others are
ignored.</p>
<p class="Pp">The following metrics are defined by <var class="Vt">struct
rt_metrics</var>:</p>
<div class="Bd-indent">
<dl class="Bl-tag">
<dt><var class="Vt">u_long rmx_locks</var>;</dt>
<dd>Flag bits indicating which metrics the kernel is not permitted to
dynamically modify.</dd>
<dt><var class="Vt">u_long rmx_mtu</var>;</dt>
<dd>MTU for this path.</dd>
<dt><var class="Vt">u_long rmx_hopcount</var>;</dt>
<dd>Number of intermediate systems on the path to this destination.</dd>
<dt><var class="Vt">u_long rmx_expire</var>;</dt>
<dd>The time (a la <a class="Xr">time(3)</a>) at which this route should
expire, or zero if it should never expire. It is the responsibility of
individual protocol suites to ensure that routes are actually deleted once
they expire.</dd>
<dt id="from"><var class="Vt">u_long rmx_recvpipe</var>;</dt>
<dd>Nominally, the bandwidth-delay product for the path
<a class="permalink" href="#from"><i class="Em">from</i></a> the
destination
<a class="permalink" href="#to"><i class="Em" id="to">to</i></a> this
system. In practice, this value is used to set the size of the receive
buffer (and thus the window in sliding-window protocols like TCP).</dd>
<dt><var class="Vt">u_long rmx_sendpipe</var>;</dt>
<dd>As before, but in the opposite direction.</dd>
<dt><var class="Vt">u_long rmx_ssthresh</var>;</dt>
<dd>The slow-start threshold used in TCP congestion-avoidance.</dd>
<dt><var class="Vt">u_long rmx_rtt</var>;</dt>
<dd>The round-trip time to this destination, in units of
<code class="Dv">RMX_RTTUNIT</code> per second.</dd>
<dt><var class="Vt">u_long rmx_rttvar</var>;</dt>
<dd>The average deviation of the round-trip time to this destination, in units
of <code class="Dv">RMX_RTTUNIT</code> per second.</dd>
<dt><var class="Vt">u_long rmx_pksent</var>;</dt>
<dd>A count of packets successfully sent via this route.</dd>
<dt><var class="Vt">u_long rmx_filler[4]</var>;</dt>
<dd>Empty space available for protocol-specific information.</dd>
</dl>
</div>
</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">route(4)</a>, <a class="Xr">route(8)</a></p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">The <var class="Vt">rtentry</var> structure first appeared in
<span class="Ux">4.2BSD</span>. The radix-tree representation of the routing
table and the <var class="Vt">rt_metrics</var> structure first appeared in
<span class="Ux">4.3BSD-Reno</span>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1>
<p class="Pp">This manual page was written by <span class="An">Garrett
Wollman</span>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="BUGS"><a class="permalink" href="#BUGS">BUGS</a></h1>
<p class="Pp">There are a number of historical relics remaining in this
interface. The <var class="Va">rt_gateway</var> and
<var class="Va">rmx_filler</var> fields could be named better.</p>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">March 5, 2014</td>
<td class="foot-os">FreeBSD 15.0</td>
</tr>
</table>
|
