X-Git-Url: https://gerrit.o-ran-sc.org/r/gitweb?a=blobdiff_plain;f=docs%2Frmr_send_msg.3.rst;h=9d214fefc89c3bade9a588c83de8552c657ec7f5;hb=refs%2Fheads%2Fdawn;hp=e347189f24a49d87ad620689aaed2af09bea5aaa;hpb=117030c67f7a3722e64f1ecc3305a5862b3b7ce9;p=ric-plt%2Flib%2Frmr.git diff --git a/docs/rmr_send_msg.3.rst b/docs/rmr_send_msg.3.rst index e347189..9d214fe 100644 --- a/docs/rmr_send_msg.3.rst +++ b/docs/rmr_send_msg.3.rst @@ -1,282 +1,281 @@ - - -.. This work is licensed under a Creative Commons Attribution 4.0 International License. -.. SPDX-License-Identifier: CC-BY-4.0 -.. CAUTION: this document is generated from source in doc/src/rtd. -.. To make changes edit the source and recompile the document. -.. Do NOT make changes directly to .rst or .md files. - - -============================================================================================ -Man Page: rmr_send_msg -============================================================================================ - -RMR Library Functions -============================================================================================ - - -NAME --------------------------------------------------------------------------------------------- - -rmr_send_msg - -SYNOPSIS --------------------------------------------------------------------------------------------- - - -:: - - #include - rmr_mbuf_t* rmr_send_msg( void* vctx, rmr_mbuf_t* msg ); - - - -DESCRIPTION --------------------------------------------------------------------------------------------- - -The rmr_send_msg function accepts a message buffer from the -user application and attempts to send it. The destination of -the message is selected based on the message type specified -in the message buffer, and the matching information in the -routing tables which are currently in use by the RMR library. -This may actually result in the sending of the message to -multiple destinations which could degrade expected overall -performance of the user application. (Limiting excessive -sending of messages is the responsibility of the -application(s) responsible for building the routing table -used by the RMR library, and not the responsibility of the -library.) - -Retries -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -The send operations in RMR will retry *soft* send failures -until one of three conditions occurs: - - - -1. - - The message is sent without error - - -2. - - The underlying transport reports a *hard* failure - - -3. - - The maximum number of retry loops has been attempted - - -A retry loop consists of approximately 1000 send attempts -**without** any intervening calls to *sleep()* or *usleep().* -The number of retry loops defaults to 1, thus a maximum of -1000 send attempts is performed before returning to the user -application. This value can be set at any point after RMr -initialisation using the *rmr_set_stimeout()* function -allowing the user application to completely disable retires -(set to 0), or to increase the number of retry loops. - -Transport Level Blocking -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -The underlying transport mechanism used to send messages is -configured in *non-blocking* mode. This means that if a -message cannot be sent immediately the transport mechanism -will **not** pause with the assumption that the inability to -send will clear quickly (within a few milliseconds). This -means that when the retry loop is completely disabled (set to -0), that the failure to accept a message for sending by the -underlying mechanisms (software or hardware) will be reported -immediately to the user application. - -It should be noted that depending on the underlying transport -mechanism being used, it is extremely likely that retry -conditions will happen during normal operations. These are -completely out of RMR's control, and there is nothing that -RMR can do to avoid or mitigate these other than by allowing -RMR to retry the send operation, and even then it is possible -(e.g., during connection reattempts), that a single retry -loop is not enough to guarantee a successful send. - -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 will be RMR_OK when the send was successful. - -When the message cannot be successfully sent this function -will return the unsent (original) message buffer with the -state set to indicate the reason for failure. The value of -*errno* may also be set to reflect a more detailed failure -reason if it is known. - -In the event of extreme failure, a nil pointer is returned. -In this case the value of errno might be of some use, for -documentation, but there will be little that the user -application can do other than to move on. - -**CAUTION:** In some cases it is extremely likely that the -message returned by the send function does **not** reference -the same memory structure. Thus is important for the user -programme to capture the new pointer for future use or to be -passed to rmr_free(). If you are experiencing either double -free errors or segment faults in either rmr_free() or -rmr_send_msg(), ensure that the return value from this -function is being captured and used. - -ERRORS --------------------------------------------------------------------------------------------- - -The following values may be passed back in the *state* field -of the returned message buffer. - - - -RMR_RETRY - - The message could not be sent, but the underlying - transport mechanism indicates that the failure is - temporary. If the send operation is tried again it might - be successful. - -RMR_SEND_FAILED - - The send operation was not successful and the underlying - transport mechanism indicates a permanent (hard) failure; - retrying the send is not possible. - -RMR_ERR_BADARG - - The message buffer pointer did not refer to a valid - message. - -RMR_ERR_NOHDR - - The header in the message buffer was not valid or - corrupted. - -RMR_ERR_NOENDPT - - The message type in the message buffer did not map to a - known endpoint. - - -The following values may be assigned to errno on failure. - - -INVAL - - Parameter(s) passed to the function were not valid, or the - underlying message processing environment was unable to - interpret the message. - - -ENOKEY - - The header information in the message buffer was invalid. - - -ENXIO - - No known endpoint for the message could be found. - - -EMSGSIZE - - The underlying transport refused to accept the message - because of a size value issue (message was not attempted - to be sent). - - -EFAULT - - The message referenced by the message buffer is corrupt - (nil pointer or bad internal length). - - -EBADF - - Internal RMR error; information provided to the message - transport environment was not valid. - - -ENOTSUP - - Sending was not supported by the underlying message - transport. - - -EFSM - - The device is not in a state that can accept the message. - - -EAGAIN - - The device is not able to accept a message for sending. - The user application should attempt to resend. - - -EINTR - - The operation was interrupted by delivery of a signal - before the message was sent. - - -ETIMEDOUT - - The underlying message environment timed out during the - send process. - - -ETERM - - The underlying message environment is in a shutdown state. - - -EXAMPLE --------------------------------------------------------------------------------------------- - -The following is a simple example of how the rmr_send_msg -function is called. In this example, the send message buffer -is saved between calls and reused eliminating alloc/free -cycles. - - -:: - - static rmr_mbuf_t* send_msg = NULL; // message to send; reused on each call - msg_t* send_pm; // payload for send - msg_t* pm; // our message format in the received payload - if( send_msg == NULL ) { - send_msg = rmr_alloc_msg( mr, MAX_SIZE ); // new buffer to send - } - // reference payload and fill in message type - pm = (msg_t*) send_msg->payload; - send_msg->mtype = MT_ANSWER; - msg->len = generate_data( pm ); // something that fills the payload in - msg = rmr_send_msg( mr, send_msg ); // ensure new pointer used after send - if( ! msg ) { - return ERROR; - } else { - if( msg->state != RMR_OK ) { - // check for RMR_ERR_RETRY, and resend if needed - // else return error - } - } - return OK; - - - -SEE ALSO --------------------------------------------------------------------------------------------- - -rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), -rmr_payload_size(3), rmr_rcv_msg(3), rmr_rcv_specific(3), -rmr_rts_msg(3), rmr_ready(3), rmr_mk_ring(3), -rmr_ring_free(3), rmr_torcv_rcv(3), rmr_wh_send_msg(3) +.. This work is licensed under a Creative Commons Attribution 4.0 International License. +.. SPDX-License-Identifier: CC-BY-4.0 +.. CAUTION: this document is generated from source in doc/src/rtd. +.. To make changes edit the source and recompile the document. +.. Do NOT make changes directly to .rst or .md files. + +============================================================================================ +Man Page: rmr_send_msg +============================================================================================ + + + + +RMR LIBRARY FUNCTIONS +===================== + + + +NAME +---- + +rmr_send_msg + + +SYNOPSIS +-------- + + +:: + + #include + + rmr_mbuf_t* rmr_send_msg( void* vctx, rmr_mbuf_t* msg ); + + + +DESCRIPTION +----------- + +The ``rmr_send_msg`` function accepts a message buffer from +the user application and attempts to send it. The destination +of the message is selected based on the message type +specified in the message buffer, and the matching information +in the routing tables which are currently in use by the RMR +library. This may actually result in the sending of the +message to multiple destinations which could degrade expected +overall performance of the user application. (Limiting +excessive sending of messages is the responsibility of the +application(s) responsible for building the routing table +used by the RMR library, and not the responsibility of the +library.) + + +Retries +------- + +The send operations in RMR will retry *soft* send failures +until one of three conditions occurs: + + +* The message is sent without error + +* The underlying transport reports a *hard* failure + +* The maximum number of retry loops has been attempted + + +A retry loop consists of approximately 1000 send attempts +**without** any intervening calls to *sleep()* or *usleep().* +The number of retry loops defaults to 1, thus a maximum of +1000 send attempts is performed before returning to the user +application. This value can be set at any point after RMR +initialisation using the *rmr_set_stimeout()* function +allowing the user application to completely disable retires +(set to 0), or to increase the number of retry loops. + + +Transport Level Blocking +------------------------ + +The underlying transport mechanism used to send messages is +configured in *non-blocking* mode. This means that if a +message cannot be sent immediately the transport mechanism +will **not** pause with the assumption that the inability to +send will clear quickly (within a few milliseconds). This +means that when the retry loop is completely disabled (set to +0), that the failure to accept a message for sending by the +underlying mechanisms (software or hardware) will be reported +immediately to the user application. + +It should be noted that depending on the underlying transport +mechanism being used, it is extremely likely that retry +conditions will happen during normal operations. These are +completely out of RMR's control, and there is nothing that +RMR can do to avoid or mitigate these other than by allowing +RMR to retry the send operation, and even then it is possible +(e.g., during connection reattempts), that a single retry +loop is not enough to guarantee a successful send. + + +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 will be ``RMR_OK`` when the send was successful. + +When the message cannot be successfully sent this function +will return the unsent (original) message buffer with the +state set to indicate the reason for failure. The value of +*errno* may also be set to reflect a more detailed failure +reason if it is known. + +In the event of extreme failure, a nil pointer is returned. +In this case the value of ``errno`` might be of some use, for +documentation, but there will be little that the user +application can do other than to move on. + +**CAUTION:** In some cases it is extremely likely that the +message returned by the send function does **not** reference +the same memory structure. Thus is important for the user +programme to capture the new pointer for future use or to be +passed to ``rmr_free().`` If you are experiencing either +double free errors or segment faults in either +``rmr_free()`` or ``rmr_send_msg(),`` ensure that the return +value from this function is being captured and used. + + +ERRORS +------ + +The following values may be passed back in the *state* field +of the returned message buffer. + + + .. list-table:: + :widths: auto + :header-rows: 0 + :class: borderless + + * - **RMR_RETRY** + - + The message could not be sent, but the underlying transport + mechanism indicates that the failure is temporary. If the + send operation is tried again it might be successful. + + * - **RMR_SEND_FAILED** + - + The send operation was not successful and the underlying + transport mechanism indicates a permanent (hard) failure; + retrying the send is not possible. + + * - **RMR_ERR_BADARG** + - + The message buffer pointer did not refer to a valid message. + + * - **RMR_ERR_NOHDR** + - + The header in the message buffer was not valid or corrupted. + + * - **RMR_ERR_NOENDPT** + - + The message type in the message buffer did not map to a known + endpoint. + + + +The following values may be assigned to ``errno`` on failure. + + .. list-table:: + :widths: auto + :header-rows: 0 + :class: borderless + + * - **INVAL** + - + Parameter(s) passed to the function were not valid, or the + underlying message processing environment was unable to + interpret the message. + + * - **ENOKEY** + - + The header information in the message buffer was invalid. + + * - **ENXIO** + - + No known endpoint for the message could be found. + + * - **EMSGSIZE** + - + The underlying transport refused to accept the message + because of a size value issue (message was not attempted to + be sent). + + * - **EFAULT** + - + The message referenced by the message buffer is corrupt (nil + pointer or bad internal length). + + * - **EBADF** + - + Internal RMR error; information provided to the message + transport environment was not valid. + + * - **ENOTSUP** + - + Sending was not supported by the underlying message + transport. + + * - **EFSM** + - + The device is not in a state that can accept the message. + + * - **EAGAIN** + - + The device is not able to accept a message for sending. The + user application should attempt to resend. + + * - **EINTR** + - + The operation was interrupted by delivery of a signal before + the message was sent. + + * - **ETIMEDOUT** + - + The underlying message environment timed out during the send + process. + + * - **ETERM** + - + The underlying message environment is in a shutdown state. + + + + +EXAMPLE +------- + +The following is a simple example of how the +``rmr_send_msg`` function is called. In this example, the +send message buffer is saved between calls and reused +eliminating alloc/free cycles. + + +:: + + static rmr_mbuf_t* send_msg = NULL; // message to send; reused on each call + msg_t* send_pm; // payload for send + msg_t* pm; // our message format in the received payload + + if( send_msg == NULL ) { + send_msg = rmr_alloc_msg( mr, MAX_SIZE ); // new buffer to send + } + + // reference payload and fill in message type + pm = (msg_t*) send_msg->payload; + send_msg->mtype = MT_ANSWER; + + msg->len = generate_data( pm ); // something that fills the payload in + msg = rmr_send_msg( mr, send_msg ); // ensure new pointer used after send + if( ! msg ) { + return ERROR; + } else { + if( msg->state != RMR_OK ) { + // check for RMR_ERR_RETRY, and resend if needed + // else return error + } + } + return OK; + + + + +SEE ALSO +-------- + +rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_init(3), +rmr_payload_size(3), rmr_rcv_msg(3), rmr_rcv_specific(3), +rmr_rts_msg(3), rmr_ready(3), rmr_mk_ring(3), +rmr_ring_free(3), rmr_torcv_rcv(3), rmr_wh_send_msg(3)