1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
202 lines
5.6 KiB
Groff
202 lines
5.6 KiB
Groff
.\"
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.\" Copyright 1996 Massachusetts Institute of Technology
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.\"
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.\" Permission to use, copy, modify, and distribute this software and
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.\" its documentation for any purpose and without fee is hereby
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.\" granted, provided that both the above copyright notice and this
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.\" permission notice appear in all copies, that both the above
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.\" copyright notice and this permission notice appear in all
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.\" supporting documentation, and that the name of M.I.T. not be used
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.\" in advertising or publicity pertaining to distribution of the
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.\" software without specific, written prior permission. M.I.T. makes
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.\" no representations about the suitability of this software for any
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.\" purpose. It is provided "as is" without express or implied
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.\" warranty.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS
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.\" ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
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.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
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.\" SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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.\" 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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.Dd October 8, 1996
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.Os
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.Dt RTALLOC 9
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.Sh NAME
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.Nm rtalloc ,
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.Nm rtalloc_ign ,
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.Nm rtalloc1
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.Nd look up a route in the kernel routing table
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.Sh SYNOPSIS
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.Fd #include <sys/socket.h>
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.Fd #include <net/route.h>
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.Ft void
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.Fn rtalloc "struct route *ro"
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.Ft void
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.Fn rtalloc_ign "struct route *ro" "u_long flags"
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.Ft "struct rtentry *"
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.Fn rtalloc1 "struct sockaddr *sa" "int report" "u_long flags"
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.Sh DESCRIPTION
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The kernel uses a radix tree structure to manage routes for the
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networking subsystem. The
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.Fn rtalloc
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family of routines is used by protocols to query this structure for a
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route corresponding to a particular end-node address, and to cause
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certain protocol\- and interface-specific actions to take place.
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.\" XXX - -mdoc should contain a standard request for getting em and
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\" en dashes.
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.Pp
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When a route with the flag
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.Dv RTF_CLONING
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or
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.Dv RTF_PRCLONING
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is retrieved, and the action of those flags is not masked, the
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.Nm rtalloc
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facility automatically generates a new route using information in the
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old route as a template, and in the case of
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.Dv RTF_CLONING ,
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sends an
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.Dv RTM_RESOLVE
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message to the appropriate interface-address route-management routine
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.Pq Fn ifa->ifa_rtrequest .
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.Dv RTF_PRCLONING
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routes are assumed to be managed by the protocol family and no
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resolution requests are made, but all routes generated by the cloning
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process retain a reference to the route from which they were
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generated.
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If the
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.Dv RTF_XRESOLVE
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flag is set, then the
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.Dv RTM_RESOLVE
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message is sent instead on the
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.Xr route 4
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socket interface, requesting that an external program resolve the
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address in question and modify the route appropriately.
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.Pp
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The default interface is
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.Fn rtalloc .
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Its only argument is
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.Ar ro ,
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a pointer to a
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.Dq Li "struct route" ,
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which is defined as follows:
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.Bd -literal -offset indent
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struct route {
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struct sockaddr ro_dst;
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struct rtentry *ro_rt;
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};
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.Ed
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Thus, this function can only be used for address families which are
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smaller than the default
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.Dq Li "struct sockaddr" .
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Before calling
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.Fn rtalloc
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for the first time, callers should ensure that unused bits of the
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structure are set to zero. On subsequent calls,
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.Fn rtalloc
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returns without performing a lookup if
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.Ar ro->ro_rt
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is non-null and the
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.Dv RTF_UP
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flag is set in the route's
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.Li rt_flags
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field.
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.Pp
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The
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.Fn rtalloc_ign
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interface can be used when the default actions of
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.Fn rtalloc
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in the presence of the
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.Dv RTF_CLONING
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and
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.Dv RTF_PRCLONING
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flags are undesired. The
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.Ar ro
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argument is the same as
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.Fn rtalloc ,
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but there is additionally a
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.Ar flags
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argument, which lists the flags in the route which are to be
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.Em ignored
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(ordinarily, one or both of
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.Dv RTF_CLONING
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or
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.Dv RTF_PRCLONING ) .
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.Pp
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The
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.Fn rtalloc1
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function is the most general form of
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.Fn rtalloc
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(and both of the other forms are implemented as calls to rtalloc1).
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It does not use the
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.Dq Li "struct route" ,
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and is therefore suitable for address families which require more
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space than is in a traditional
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.Dq Li "struct sockaddr" .
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Instead, it takes a
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.Dq Li "struct sockaddr *"
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directly as the
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.Ar sa
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argument. The second argument,
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.Ar report ,
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controls whether
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.Dv RTM_RESOLVE
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requests are sent to the lower layers when an
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.Dv RTF_CLONING
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or
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.Dv RTF_PRCLONING
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route is cloned. Ordinarily a value of one should be passed, except
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in the processing of those lower layers which use the cloning
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facility.
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The third argument,
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.Ar flags ,
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is a set of flags to ignore, as in
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.Fn rtalloc_ign .
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.Sh RETURN VALUES
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The
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.Fn rtalloc
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and
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.Fn rtalloc_ign
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functions do not return a value. The
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.Fn rtalloc1
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function returns a pointer to a routing-table entry if it succeeds,
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otherwise a null pointer. Lack of a route should in most cases be
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translated to the
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.Xr errno 2
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value
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.Er EHOSTUNREACH .
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.Sh SEE ALSO
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.Xr route 4 ,
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.Xr rtentry 9
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.Sh HISTORY
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The
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.Nm rtalloc
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facility first appeared in
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.Bx 4.2 ,
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although with much different internals. The
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.Fn rtalloc_ign
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function and the
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.Ar flags
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argument to
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.Fn rtalloc1
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first appeared in
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.Fx 2.0 .
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.Sh AUTHOR
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This manual page was written by Garrett Wollman, as were the changes
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to implement
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.Dv RTF_PRCLONING
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and the
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.Fn rtalloc_ign
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function and the
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.Ar flags
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argument to
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.Fn rtalloc1 .
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