.if false
==================================================================================
   Copyright (c) 2019-2020 Nokia
   Copyright (c) 2018-2020 AT&T Intellectual Property.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
==================================================================================
.fi
.if false
    Mnemonic    rmr_rts_msg_man.xfm
    Abstract    The manual page for the rmr_rts_msg function.
    Author      E. Scott Daniels
    Date        28 January 2019
.fi

.gv e LIB lib
.im &{lib}/man/setup.im

&line_len(6i)

&h1(RMR Library Functions)
&h2(NAME)
    rmr_rts_msg

&h2(SYNOPSIS )
&indent
&ex_start
#include <rmr/rmr.h>

rmr_mbuf_t*  rmr_rts_msg( void* vctx, rmr_mbuf_t* msg );
&ex_end
&uindent

&h2(DESCRIPTION)
The &cw(rmr_rts_msg) function sends a message returning it to the endpoint
which sent the message rather than selecting an endpoint based on the
message type and routing table.
Other than this small difference, the behaviour is exactly the same as
&cw(rmr_send_msg.)

.** pull in common retry text
.im &{lib}/man/retry.im

&h2(PAYLOAD SIZE)
When crafting a response based on a received message, the user application must
take care not to write more bytes to the message payload than the allocated message
has.
In the case of a received message, it is possible that the response needs to be
larger than the payload associated with the inbound message.
In order to use the return to sender function, the source information in the original
message must be present in the response; information which cannot be added to a
message buffer allocated through the standard RMR allocation function.
To allocate a buffer with a larger payload, and which retains the necessary sender
data needed by this function, the &ital(rmr_realloc_payload()) function must be
used to extend the payload to a size suitable for the response.

&h2(RETURN VALUE)
On success, a new message buffer, with an empty payload, is returned for the application
to use for the next send.
The state in this buffer will reflect the overall send operation state and should be
&cw(RMR_OK.)

&space
If the state in the returned buffer is anything other than &cw(RMR_OK,) the user application
may need to attempt a retransmission of the message, or take other action depending on the
setting of &cw(errno) as described below.

&space
In the event of extreme failure, a nil pointer is returned. In this case the value of
&cw(errno) might be of some use, for documentation, but there will be little that the
user application can do other than to move on.

&h2(ERRORS)
The following values may be passed back in the &ital(state) field of the returned message
buffer.

&space
&beg_dlist(.75i : ^&bold_font )
&ditem(RMR_ERR_BADARG) The message buffer pointer did not refer to a valid message.
&ditem(RMR_ERR_NOHDR)  The header in the message buffer was not valid or corrupted.
&ditem(RMR_ERR_NOENDPT)  The message type in the message buffer did not map to a known endpoint.
&ditem(RMR_ERR_SENDFAILED)  The send failed; &cw(errno) has the possible reason.
&end_dlist

&space
The following values may be assigned to &cw(errno) on failure.

&beg_dlist(.75i : ^&bold_font )
&ditem(INVAL) Parameter(s) passed to the function were not valid, or the underlying message processing environment was unable to interpret the message.

&ditem(ENOKEY) The header information in the message buffer was invalid.

&ditem(ENXIO) No known endpoint for the message could be found.

&ditem(EMSGSIZE) The underlying transport refused to accept the message because of a size value issue (message was not attempted to be sent).

&ditem(EFAULT) The message referenced by the message buffer is corrupt (nil pointer or bad internal length).

&ditem(EBADF) Internal RMR error; information provided to the message transport environment was not valid.

&ditem(ENOTSUP) Sending was not supported by the underlying message transport.

&ditem(EFSM) The device is not in a state that can accept the message.

&ditem(EAGAIN) The device is not able to accept a message for sending. The user application should attempt to resend.

&ditem(EINTR) The operation was interrupted by delivery of a signal before the message was sent.

&ditem(ETIMEDOUT) The underlying message environment timed out during the send process.

&ditem(ETERM) The underlying message environment is in a shutdown state.
&end_dlist

&h2(EXAMPLE)

&h2(SEE ALSO )
.ju off
rmr_alloc_msg(3),
rmr_call(3),
rmr_free_msg(3),
rmr_init(3),
rmr_payload_size(3),
rmr_send_msg(3),
rmr_rcv_msg(3),
rmr_rcv_specific(3),
rmr_ready(3),
rmr_fib(3),
rmr_has_str(3),
rmr_set_stimeout(3),
rmr_tokenise(3),
rmr_mk_ring(3),
rmr_ring_free(3)
.ju on