[ric-plt/lib/rmr.git] / src / rmr / nng / src / sr_nng_static.c

// : vi ts=4 sw=4 noet 2
/*
==================================================================================
        Copyright (c) 2019 Nokia
        Copyright (c) 2018-2019 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.
==================================================================================
*/

/*
        Mnemonic:       sr_nng_static.c
        Abstract:       These are static send/receive primatives which (sadly)
                                differ based on the underlying protocol (nng vs nanomsg).
                                Split from rmr_nng.c  for easier wormhole support.

        Author:         E. Scott Daniels
        Date:           13 February 2019
*/

#ifndef _sr_nng_static_c
#define _sr_nng_static_c

#include <nng/nng.h>
#include <nng/protocol/pubsub0/pub.h>
#include <nng/protocol/pubsub0/sub.h>
#include <nng/protocol/pipeline0/push.h>
#include <nng/protocol/pipeline0/pull.h>

/*
        Translates the nng state passed in to one of ours that is suitable to put
        into the message, and sets errno to something that might be useful.
        If we don't have a specific RMr state, then we return the default (e.g.
        receive failed).

        The addition of the connection shut error code to the switch requires
        that the NNG version at commit e618abf8f3db2a94269a (or after) be
        used for compiling RMR. 
*/
static inline int xlate_nng_state( int state, int def_state ) {

        switch( state ) {
                case 0:
                        errno = 0;
                        state = RMR_OK;
                        break;

                case NNG_EAGAIN:                                // soft errors get retry as the RMr error
                        state = RMR_ERR_RETRY;
                        errno = EAGAIN;
                        break;

                case NNG_ETIMEDOUT:
                        state = RMR_ERR_RETRY;
                        errno = EAGAIN;
                        break;

                case NNG_ENOTSUP:
                        errno  = ENOTSUP;
                        state = def_state;
                        break;

                case NNG_EINVAL:
                        errno  = EINVAL;
                        state = def_state;
                        break;

                case NNG_ENOMEM:
                        errno  = ENOMEM;
                        state = def_state;
                        break;

                case NNG_ESTATE:
                        errno  = EBADFD;                                // file des not in a good state for the operation
                        state = def_state;
                        break;

                case NNG_ECONNSHUT:                                     // new error with nng commit e618abf8f3db2a94269a79c8901a51148d48fcc2 (Sept 2019)
                case NNG_ECLOSED:
                        errno  = EBADFD;                                // file des not in a good state for the operation
                        state = def_state;
                        break;

                default:
                        errno = EBADE;
                        state = def_state;
                        break;
        }

        return state;
}

/*
        Alloc a new nano zero copy buffer and put into msg. If msg is nil, then we will alloc
        a new message struct as well. Size is the size of the zc buffer to allocate (not
        including our header). If size is 0, then the buffer allocated is the size previously
        allocated (if msg is !nil) or the default size given at initialisation).

        The trlo (trace data lengh override) is used for trace length if >0. If <= 0, then
        the context value is used.

        NOTE:  while accurate, the nng doc implies that both the msg buffer and data buffer
                are zero copy, however ONLY the message is zero copy. We now allocate and use
                nng messages.
*/
static rmr_mbuf_t* alloc_zcmsg( uta_ctx_t* ctx, rmr_mbuf_t* msg, int size, int state, int trlo ) {
        size_t          mlen;                   // size of the transport buffer that we'll allocate
        uta_mhdr_t*     hdr;                    // convenience pointer
        int                     tr_len;                 // trace data len (default or override)

        tr_len = trlo > 0 ? trlo : ctx->trace_data_len;

        mlen = sizeof( uta_mhdr_t ) + tr_len + ctx->d1_len + ctx->d2_len;       // start with header and trace/data lengths
        mlen += (size > 0 ? size  : ctx->max_plen);                                                     // add user requested size or size set during init

        if( msg == NULL ) {
                msg = (rmr_mbuf_t *) malloc( sizeof *msg );
                if( msg == NULL ) {
                        fprintf( stderr, "[CRI] rmr_alloc_zc: cannot get memory for message\n" );
                        exit( 1 );
                }
        } else {
                mlen = msg->alloc_len;                                                  // msg given, allocate the same size as before
        }

        memset( msg, 0, sizeof( *msg ) );

        if( (state = nng_msg_alloc( (nng_msg **) &msg->tp_buf, mlen )) != 0 ) {
                fprintf( stderr, "[CRI] rmr_alloc_zc: cannot get memory for zero copy buffer: %d\n", ENOMEM );
                abort( );                                                                                       // toss out a core file for this
        }

        msg->header = nng_msg_body( msg->tp_buf );
        memset( msg->header, 0, sizeof( uta_mhdr_t ) );                         // ensure no junk in the header area
        if( (hdr = (uta_mhdr_t *) msg->header) != NULL ) {
                hdr->rmr_ver = htonl( RMR_MSG_VER );                                    // set current version
                hdr->sub_id = htonl( UNSET_SUBID );
                SET_HDR_LEN( hdr );                                                                             // ensure these are converted to net byte order
                SET_HDR_TR_LEN( hdr, ctx->trace_data_len );
                SET_HDR_D1_LEN( hdr, ctx->d1_len );
                //SET_HDR_D2_LEN( hdr, ctx->d2_len );                           // future
        }
        msg->len = 0;                                                                                   // length of data in the payload
        msg->alloc_len = mlen;                                                                  // length of allocated transport buffer
        msg->sub_id = UNSET_SUBID;
        msg->mtype = UNSET_MSGTYPE;
        msg->payload = PAYLOAD_ADDR( hdr );                                             // point to payload (past all header junk)
        msg->xaction = ((uta_mhdr_t *)msg->header)->xid;                // point at transaction id in header area
        msg->state = state;                                                                             // fill in caller's state (likely the state of the last operation)
        msg->flags |= MFL_ZEROCOPY;                                                             // this is a zerocopy sendable message
        strncpy( (char *) ((uta_mhdr_t *)msg->header)->src, ctx->my_name, RMR_MAX_SRC );
        strncpy( (char *) ((uta_mhdr_t *)msg->header)->srcip, ctx->my_ip, RMR_MAX_SRC );

        if( DEBUG > 1 ) fprintf( stderr, "[DBUG] alloc_zcmsg mlen=%ld size=%d mpl=%d flags=%02x\n", (long) mlen, size, ctx->max_plen, msg->flags );

        return msg;
}

/*
        Allocates only the mbuf and does NOT allocate an underlying transport buffer since
        NNG receive must allocate that on its own.
*/
static rmr_mbuf_t* alloc_mbuf( uta_ctx_t* ctx, int state ) {
        size_t  mlen;
        uta_mhdr_t* hdr;                        // convenience pointer
        rmr_mbuf_t* msg;

        msg = (rmr_mbuf_t *) malloc( sizeof *msg );
        if( msg == NULL ) {
                fprintf( stderr, "[CRI] rmr_alloc_zc: cannot get memory for message\n" );
                exit( 1 );
        }

        memset( msg, 0, sizeof( *msg ) );

        msg->sub_id = UNSET_SUBID;
        msg->mtype = UNSET_MSGTYPE;
        msg->tp_buf = NULL;
        msg->header = NULL;
        msg->len = -1;                                                                                  // no payload; invalid len
        msg->alloc_len = -1;
        msg->payload = NULL;
        msg->xaction = NULL;
        msg->state = RMR_ERR_UNSET;
        msg->flags = 0;

        return msg;
}

/*
        This accepts a message with the assumption that only the tp_buf pointer is valid. It
        sets all of the various header/payload/xaction pointers in the mbuf to the proper
        spot in the transport layer buffer.  The len in the header is assumed to be the
        allocated len (a receive buffer that nng created);

        The alen parm is the assumed allocated length; assumed because it's a value likely
        to have come from nng receive and the actual alloc len might be larger, but we
        can only assume this is the total usable space.

        This function returns the message with an error state set if it detects that the
        received message might have been truncated.  Check is done here as the calculation
        is somewhat based on header version.
*/
static void ref_tpbuf( rmr_mbuf_t* msg, size_t alen )  {
        uta_mhdr_t* hdr = NULL;                 // current header
        uta_v1mhdr_t* v1hdr;                    // version 1 header
        int ver;
        int     hlen;                                           // header len to use for a truncation check

        msg->header = nng_msg_body( msg->tp_buf );                              // header is the start of the transport buffer
        v1hdr = (uta_v1mhdr_t *) msg->header;                                   // v1 will always allow us to suss out the version

        if( v1hdr->rmr_ver == 1 ) {                     // bug in verion 1 didn't encode the version in network byte order
                ver = 1;
                v1hdr->rmr_ver = htonl( 1 );            // save it correctly in case we clone the message
        } else {
                ver = ntohl( v1hdr->rmr_ver );
        }

        switch( ver ) {
                case 1:
                        msg->len = ntohl( v1hdr->plen );                                                // length sender says is in the payload (received length could be larger)
                        msg->alloc_len = alen;                                                                  // length of whole tp buffer (including header, trace and data bits)
                        msg->payload = msg->header + sizeof( uta_v1mhdr_t );    // point past header to payload (single buffer allocation above)

                        msg->xaction = &v1hdr->xid[0];                                                  // point at transaction id in header area
                        msg->flags |= MFL_ZEROCOPY;                                                             // this is a zerocopy sendable message
                        msg->mtype = ntohl( v1hdr->mtype );                                             // capture and convert from network order to local order
                        msg->sub_id = UNSET_SUBID;                                                              // type 1 messages didn't have this
                        msg->state = RMR_OK;
                        hlen = sizeof( uta_v1mhdr_t );
                        break;

                default:                                                                                                        // current version always lands here
                        hdr = (uta_mhdr_t *) msg->header;
                        msg->len = ntohl( hdr->plen );                                                  // length sender says is in the payload (received length could be larger)
                        msg->alloc_len = alen;                                                                  // length of whole tp buffer (including header, trace and data bits)

                        msg->payload = PAYLOAD_ADDR( hdr );                                             // at user payload
                        msg->xaction = &hdr->xid[0];                                                    // point at transaction id in header area
                        msg->flags |= MFL_ZEROCOPY;                                                             // this is a zerocopy sendable message
                        msg->mtype = ntohl( hdr->mtype );                                               // capture and convert from network order to local order
                        msg->sub_id = ntohl( hdr->sub_id );
                        hlen = RMR_HDR_LEN( hdr );                                                              // len to use for truncated check later
                        break;
        }

        if( msg->len > (msg->alloc_len - hlen ) ) {
                msg->state = RMR_ERR_TRUNC;
                msg->len = msg->alloc_len -  hlen;                                                      // adjust len down so user app doesn't overrun
        } else {
                msg->state = RMR_OK;
        }
}

/*
        This will clone a message into a new zero copy buffer and return the cloned message.
*/
static inline rmr_mbuf_t* clone_msg( rmr_mbuf_t* old_msg  ) {
        rmr_mbuf_t* nm;                 // new message buffer
        size_t  mlen;
        int state;
        uta_mhdr_t* hdr;
        uta_v1mhdr_t* v1hdr;

        nm = (rmr_mbuf_t *) malloc( sizeof *nm );
        if( nm == NULL ) {
                fprintf( stderr, "[CRI] rmr_clone: cannot get memory for message buffer\n" );
                exit( 1 );
        }
        memset( nm, 0, sizeof( *nm ) );

        mlen = old_msg->alloc_len;                                                                              // length allocated before
        if( (state = nng_msg_alloc( (nng_msg **) &nm->tp_buf, mlen )) != 0 ) {
                fprintf( stderr, "[CRI] rmr_clone: cannot get memory for zero copy buffer: %d\n", ENOMEM );
                exit( 1 );
        }

        nm->header = nng_msg_body( nm->tp_buf );                                // set and copy the header from old message
        v1hdr = (uta_v1mhdr_t *) old_msg->header;               // v1 will work to dig header out of any version
        switch( ntohl( v1hdr->rmr_ver ) ) {
                case 1:
                        memcpy( v1hdr, old_msg->header, sizeof( *v1hdr ) );             // copy complete header
                        nm->payload = (void *) v1hdr + sizeof( *v1hdr );
                        break;

                default:                                                                                        // current message always caught  here
                        hdr = nm->header;
                        memcpy( hdr, old_msg->header, RMR_HDR_LEN( old_msg->header ) + RMR_TR_LEN( old_msg->header ) + RMR_D1_LEN( old_msg->header ) + RMR_D2_LEN( old_msg->header ));  // copy complete header, trace and other data
                        nm->payload = PAYLOAD_ADDR( hdr );                              // at user payload
                        break;
        }

        // --- these are all version agnostic -----------------------------------
        nm->mtype = old_msg->mtype;
        nm->sub_id = old_msg->sub_id;
        nm->len = old_msg->len;                                                                 // length of data in the payload
        nm->alloc_len = mlen;                                                                   // length of allocated payload

        nm->xaction = hdr->xid;                                                                 // reference xaction
        nm->state = old_msg->state;                                                             // fill in caller's state (likely the state of the last operation)
        nm->flags = old_msg->flags | MFL_ZEROCOPY;                              // this is a zerocopy sendable message
        memcpy( nm->payload, old_msg->payload, old_msg->len );

        return nm;
}

/*
        This will clone a message with a change to the trace area in the header such that
        it will be tr_len passed in. The trace area in the cloned message will be uninitialised.
        The orignal message will be left unchanged, and a pointer to the new message is returned.
        It is not possible to realloc buffers and change the data sizes.
*/
static inline rmr_mbuf_t* realloc_msg( rmr_mbuf_t* old_msg, int tr_len  ) {
        rmr_mbuf_t* nm;                 // new message buffer
        size_t  mlen;
        int state;
        uta_mhdr_t* hdr;
        uta_v1mhdr_t* v1hdr;
        int     tr_old_len;                     // tr size in new buffer

        nm = (rmr_mbuf_t *) malloc( sizeof *nm );
        if( nm == NULL ) {
                fprintf( stderr, "[CRI] rmr_clone: cannot get memory for message buffer\n" );
                exit( 1 );
        }
        memset( nm, 0, sizeof( *nm ) );

        hdr = old_msg->header;
        tr_old_len = RMR_TR_LEN( hdr );                         // bytes in old header for trace

        mlen = old_msg->alloc_len + (tr_len - tr_old_len);                                                      // new length with trace adjustment
        if( DEBUG ) fprintf( stderr, "[DBUG] tr_realloc old size=%d new size=%d new tr_len=%d\n", (int) old_msg->alloc_len, (int) mlen, (int) tr_len );
        if( (state = nng_msg_alloc( (nng_msg **) &nm->tp_buf, mlen )) != 0 ) {
                fprintf( stderr, "[CRI] rmr_clone: cannot get memory for zero copy buffer: %d\n", ENOMEM );
                exit( 1 );
        }

        nm->header = nng_msg_body( nm->tp_buf );                                // set and copy the header from old message
        v1hdr = (uta_v1mhdr_t *) old_msg->header;                               // v1 will work to dig header out of any version
        switch( ntohl( v1hdr->rmr_ver ) ) {
                case 1:
                        memcpy( v1hdr, old_msg->header, sizeof( *v1hdr ) );             // copy complete header
                        nm->payload = (void *) v1hdr + sizeof( *v1hdr );
                        break;

                default:                                                                                        // current message version always caught  here
                        hdr = nm->header;
                        memcpy( hdr, old_msg->header, sizeof( uta_mhdr_t ) );           // ONLY copy the header portion; trace and data offsets might have changed
                        SET_HDR_TR_LEN( hdr, tr_len );                                                          // must adjust trace len in new message before copy

                        if( RMR_D1_LEN( hdr )  ) {
                                memcpy( DATA1_ADDR( hdr ), DATA1_ADDR( old_msg->header), RMR_D1_LEN( hdr ) );           // copy data1 and data2 if necessary
                        }
                        if( RMR_D2_LEN( hdr )  ) {
                                memcpy( DATA2_ADDR( hdr ), DATA2_ADDR( old_msg->header), RMR_D2_LEN( hdr ) );
                        }

                        nm->payload = PAYLOAD_ADDR( hdr );                                                                      // directly at the payload
                        break;
        }

        // --- these are all version agnostic -----------------------------------
        nm->mtype = old_msg->mtype;
        nm->sub_id = old_msg->sub_id;
        nm->len = old_msg->len;                                                                 // length of data in the payload
        nm->alloc_len = mlen;                                                                   // length of allocated payload

        nm->xaction = hdr->xid;                                                                 // reference xaction
        nm->state = old_msg->state;                                                             // fill in caller's state (likely the state of the last operation)
        nm->flags = old_msg->flags | MFL_ZEROCOPY;                              // this is a zerocopy sendable message
        memcpy( nm->payload, old_msg->payload, old_msg->len );

        return nm;
}

/*
        This is the receive work horse used by the outer layer receive functions.
        It waits for a message to be received on our listen socket. If old msg
        is passed in, the we assume we can use it instead of allocating a new
        one, else a new block of memory is allocated.

        This allocates a zero copy message so that if the user wishes to call
        rmr_rts_msg() the send is zero copy.

        The nng timeout on send is at the ms level which is a tad too long for
        our needs.  So, if NNG returns eagain or timedout (we don't set one)
        we will loop up to 5 times with a 10 microsecond delay between each
        attempt.  If at the end of this set of retries NNG is still saying
        eagain/timeout we'll return to the caller with that set in errno.
        Right now this is only for zero-copy buffers (they should all be zc
        buffers now).


        In the NNG msg world it must allocate the receive buffer rather
        than accepting one that we allocated from their space and could
        reuse.  They have their reasons I guess.  Thus, we will free
        the old transport buffer if user passes the message in; at least
        our mbuf will be reused.

        When msg->state is not ok, this function must set tp_state in the message as some API 
        fucntions return the message directly and do not propigate errno into the message.
*/
static rmr_mbuf_t* rcv_msg( uta_ctx_t* ctx, rmr_mbuf_t* old_msg ) {
        int state;
        rmr_mbuf_t*     msg = NULL;             // msg received
        uta_mhdr_t* hdr;
        size_t  rsize;                          // nng needs to write back the size received... grrr

        if( old_msg ) {
                msg = old_msg;
                if( msg->tp_buf != NULL ) {
                        nng_msg_free( msg->tp_buf );
                }

                msg->tp_buf = NULL;
        } else {
                msg = alloc_mbuf( ctx, RMR_OK );                                // msg without a transport buffer
        }

        msg->alloc_len = 0;
        msg->len = 0;
        msg->payload = NULL;
        msg->xaction = NULL;
        msg->tp_buf = NULL;

        msg->state = nng_recvmsg( ctx->nn_sock, (nng_msg **) &msg->tp_buf, NO_FLAGS );                  // blocks hard until received
        if( (msg->state = xlate_nng_state( msg->state, RMR_ERR_RCVFAILED )) != RMR_OK ) {
                msg->tp_state = errno;
                return msg;
        }

        msg->tp_state = 0;
        if( msg->tp_buf == NULL ) {             // if state is good this _should_ not be nil, but parninoia says check anyway
                msg->state = RMR_ERR_EMPTY;
                msg->tp_state = 0;
                return msg;
        }

        rsize = nng_msg_len( msg->tp_buf );
        if( rsize >= sizeof( uta_v1mhdr_t ) ) {                 // we need at least a full type 1 (smallest) header here
                ref_tpbuf( msg, rsize );                                        // point payload, header etc to the data and set trunc error if needed
                hdr = (uta_mhdr_t *) msg->header;
                msg->flags |= MFL_ADDSRC;                                       // turn on so if user app tries to send this buffer we reset src

                if( DEBUG > 1 ) fprintf( stderr, "[DBUG] rcv_msg: got something: type=%d state=%d len=%d diff=%ld\n",
                                msg->mtype, msg->state, msg->len,  msg->payload - (unsigned char *) msg->header );
        } else {
                msg->state = RMR_ERR_EMPTY;
                msg->tp_state = 0;
                msg->len = 0;
                msg->alloc_len = rsize;
                msg->payload = NULL;
                msg->xaction = NULL;
                msg->flags |= MFL_ZEROCOPY;                                                                     // this is a zerocopy sendable message
                msg->mtype = UNSET_MSGTYPE;
                msg->sub_id = UNSET_SUBID;
        }

        return msg;
}

/*
        Receives a 'raw' message from a non-RMr sender (no header expected). The returned
        message buffer cannot be used to send, and the length information may or may
        not be correct (it is set to the length received which might be more than the
        bytes actually in the payload).

        Mostly this supports the route table collector, but could be extended with an
        API external function.
*/
static void* rcv_payload( uta_ctx_t* ctx, rmr_mbuf_t* old_msg ) {
        int state;
        rmr_mbuf_t*     msg = NULL;             // msg received
        size_t  rsize;                          // nng needs to write back the size received... grrr

        if( old_msg ) {
                msg = old_msg;
        } else {
                msg = alloc_zcmsg( ctx, NULL, RMR_MAX_RCV_BYTES, RMR_OK, DEF_TR_LEN );                  // will abort on failure, no need to check
        }

        msg->state = nng_recvmsg( ctx->nn_sock, (nng_msg **) &msg->tp_buf, NO_FLAGS );                  // blocks hard until received
        if( (msg->state = xlate_nng_state( msg->state, RMR_ERR_RCVFAILED )) != RMR_OK ) {
                return msg;
        }
        rsize = nng_msg_len( msg->tp_buf );

        // do NOT use ref_tpbuf() here! Must fill these in manually.
        msg->header = nng_msg_body( msg->tp_buf );
        msg->len = rsize;                                                       // len is the number of bytes received
        msg->alloc_len = rsize;
        msg->mtype = UNSET_MSGTYPE;                                     // raw message has no type
        msg->sub_id = UNSET_SUBID;                                      // nor a subscription id
        msg->state = RMR_OK;
        msg->flags = MFL_RAW;
        msg->payload = msg->header;                                     // payload is the whole thing; no header
        msg->xaction = NULL;

        if( DEBUG > 1 ) fprintf( stderr, "[DBUG] rcv_payload: got something: type=%d state=%d len=%d\n", msg->mtype, msg->state, msg->len );

        return msg;
}

/*
        This does the hard work of actually sending the message to the given socket. On success,
        a new message struct is returned. On error, the original msg is returned with the state
        set to a reasonable value. If the message being sent as MFL_NOALLOC set, then a new
        buffer will not be allocated and returned (mostly for call() interal processing since
        the return message from call() is a received buffer, not a new one).

        Called by rmr_send_msg() and rmr_rts_msg(), etc. and thus we assume that all pointer
        validation has been done prior.

        When msg->state is not ok, this function must set tp_state in the message as some API 
        fucntions return the message directly and do not propigate errno into the message.
*/
static rmr_mbuf_t* send_msg( uta_ctx_t* ctx, rmr_mbuf_t* msg, nng_socket nn_sock, int retries ) {
        int state;
        uta_mhdr_t*     hdr;
        int nng_flags = NNG_FLAG_NONBLOCK;              // if we need to set any nng flags (zc buffer) add it to this
        int spin_retries = 1000;                                // if eagain/timeout we'll spin, at max, this many times before giving up the CPU
        int     tr_len;                                                         // trace len in sending message so we alloc new message with same trace size

        // future: ensure that application did not overrun the XID buffer; last byte must be 0

        hdr = (uta_mhdr_t *) msg->header;
        hdr->mtype = htonl( msg->mtype );                                                               // stash type/len/sub_id in network byte order for transport
        hdr->sub_id = htonl( msg->sub_id );
        hdr->plen = htonl( msg->len );
        tr_len = RMR_TR_LEN( hdr );                                                                             // snarf trace len before sending as hdr is invalid after send

        if( msg->flags & MFL_ADDSRC ) {                                                                 // buffer was allocated as a receive buffer; must add our source
                strncpy( (char *) ((uta_mhdr_t *)msg->header)->src, ctx->my_name, RMR_MAX_SRC );                                        // must overlay the source to be ours
                strncpy( (char *) ((uta_mhdr_t *)msg->header)->srcip, ctx->my_ip, RMR_MAX_SRC );
        }

        errno = 0;
        msg->state = RMR_OK;
        if( msg->flags & MFL_ZEROCOPY ) {                                                                       // faster sending with zcopy buffer
                do {
                        if( (state = nng_sendmsg( nn_sock, (nng_msg *) msg->tp_buf, nng_flags )) != 0 ) {               // must check and retry some if transient failure
                                msg->state = state;
                                if( retries > 0 && (state == NNG_EAGAIN || state == NNG_ETIMEDOUT) ) {
                                        if( --spin_retries <= 0 ) {                     // don't give up the processor if we don't have to
                                                retries--;
                                                if( retries > 0 ) {                                     // only if we'll loop through again
                                                        usleep( 1 );                                    // sigh, give up the cpu and hope it's just 1 miscrosec
                                                }
                                                spin_retries = 1000;
                                        }
                                } else {
                                        state = 0;                      // don't loop
                                        //if( DEBUG ) fprintf( stderr, ">>>>> send failed: %s\n", nng_strerror( state ) );
                                }
                        } else {
                                state = 0;
                                msg->state = RMR_OK;
                                msg->header = NULL;                                                                                     // nano frees; don't risk accessing later by mistake
                                msg->tp_buf = NULL;
                                hdr = NULL;
                        }
                } while( state && retries > 0 );
        } else {
                // future: this should not happen as all buffers we deal with are zc buffers; might make sense to remove the test and else
                msg->state = RMR_ERR_SENDFAILED;
                errno = ENOTSUP;
                msg->tp_state = errno;
                return msg;
                /*
                NOT SUPPORTED
                if( (state = nng_send( nn_sock, msg->header, sizeof( uta_mhdr_t ) + msg->len, nng_flags )) != 0 ) {
                        msg->state = state;
                        //if( DEBUG ) fprintf( stderr, ">>>>> copy buffer send failed: %s\n", nng_strerror( state ) );
                }
                */
        }

        if( msg->state == RMR_OK ) {                                                                    // successful send
                if( !(msg->flags & MFL_NOALLOC) ) {                                                     // allocate another sendable zc buffer unless told otherwise
                        return alloc_zcmsg( ctx, msg, 0, RMR_OK, tr_len );              // preallocate a zero-copy buffer and return msg
                } else {
                        rmr_free_msg( msg );                                            // not wanting a meessage back, trash this one
                        return NULL;
                }
        } else {                                                                                        // send failed -- return original message
                if( msg->state == NNG_EAGAIN || msg->state == NNG_ETIMEDOUT ) {
                        errno = EAGAIN;
                        msg->state = RMR_ERR_RETRY;                                     // errno will have nano reason
                } else {
                        msg->state = xlate_nng_state( msg->state, RMR_ERR_SENDFAILED );         // xlate to our state and set errno
                }

                if( DEBUG ) fprintf( stderr, "[DBUG] send failed: %d %s\n", (int) msg->state, strerror( msg->state ) );
        }

        return msg;
}

/*
        send message with maximum timeout.
        Accept a message and send it to an endpoint based on message type.
        If NNG reports that the send attempt timed out, or should be retried,
        RMr will retry for approximately max_to microseconds; rounded to the next
        higher value of 10.

        Allocates a new message buffer for the next send. If a message type has
        more than one group of endpoints defined, then the message will be sent
        in round robin fashion to one endpoint in each group.

        An endpoint will be looked up in the route table using the message type and
        the subscription id. If the subscription id is "UNSET_SUBID", then only the
        message type is used.  If the initial lookup, with a subid, fails, then a
        second lookup using just the mtype is tried.

        When msg->state is not OK, this function must set tp_state in the message as 
        some API fucntions return the message directly and do not propigate errno into 
        the message.

        CAUTION: this is a non-blocking send.  If the message cannot be sent, then
                it will return with an error and errno set to eagain. If the send is
                a limited fanout, then the returned status is the status of the last
                send attempt.

*/
static  rmr_mbuf_t* mtosend_msg( void* vctx, rmr_mbuf_t* msg, int max_to ) {
        rtable_ent_t*   rte;                    // the route table entry which matches the message key
        nng_socket      nn_sock;                        // endpoint socket for send
        uta_ctx_t*      ctx;
        int                     group;                          // selected group to get socket for
        int                     send_again;                     // true if the message must be sent again
        rmr_mbuf_t*     clone_m;                        // cloned message for an nth send
        int                     sock_ok;                        // got a valid socket from round robin select
        char*           d1;
        int                     ok_sends = 0;           // track number of ok sends

        if( (ctx = (uta_ctx_t *) vctx) == NULL || msg == NULL ) {               // bad stuff, bail fast
                errno = EINVAL;                                                                                         // if msg is null, this is their clue
                if( msg != NULL ) {
                        msg->state = RMR_ERR_BADARG;
                        errno = EINVAL;                                                                                 // must ensure it's not eagain
                        msg->tp_state = errno;
                }
                return msg;
        }

        errno = 0;                                                                                                      // clear; nano might set, but ensure it's not left over if it doesn't
        if( msg->header == NULL ) {
                fprintf( stderr, "rmr_send_msg: ERROR: message had no header\n" );
                msg->state = RMR_ERR_NOHDR;
                errno = EBADMSG;                                                                                        // must ensure it's not eagain
                msg->tp_state = errno;
                return msg;
        }

        if( max_to < 0 ) {
                max_to = ctx->send_retries;             // convert to retries
        }

        if( (rte = uta_get_rte( ctx->rtable, msg->sub_id, msg->mtype, TRUE )) == NULL ) {               // find the entry which matches subid/type allow fallback to type only key
                if( ctx->flags & CTXFL_WARN ) {
                        fprintf( stderr, "[WARN] no endpoint for mtype=%d sub_id=%d\n", msg->mtype, msg->sub_id );
                }
                msg->state = RMR_ERR_NOENDPT;
                errno = ENXIO;                                                                          // must ensure it's not eagain
                msg->tp_state = errno;
                return msg;                                                                                     // caller can resend (maybe) or free
        }

        send_again = 1;                                                                                 // force loop entry
        group = 0;                                                                                              // always start with group 0
        while( send_again ) {
                sock_ok = uta_epsock_rr( rte, group, &send_again, &nn_sock );                                                           // select endpt from rr group and set again if more groups

                if( DEBUG ) fprintf( stderr, "[DBUG] mtosend_msg: flgs=0x%04x type=%d again=%d group=%d len=%d sock_ok=%d\n",
                                msg->flags, msg->mtype, send_again, group, msg->len, sock_ok );

                group++;

                if( sock_ok ) {                                                                                                 // with an rte we _should_ always have a socket, but don't bet on it
                        if( send_again ) {
                                clone_m = clone_msg( msg );                                                             // must make a copy as once we send this message is not available
                                if( clone_m == NULL ) {
                                        msg->state = RMR_ERR_SENDFAILED;
                                        errno = ENOMEM;
                                        msg->tp_state = errno;
                                        if( ctx->flags & CTXFL_WARN ) {
                                                fprintf( stderr, "[WARN] unable to clone message for multiple rr-group send\n" );
                                        }
                                        return msg;
                                }

                                if( DEBUG ) fprintf( stderr, "[DBUG] msg cloned: type=%d len=%d\n", msg->mtype, msg->len );
                                msg->flags |= MFL_NOALLOC;                                                              // keep send from allocating a new message; we have a clone to use
                                msg = send_msg( ctx, msg, nn_sock, max_to );                    // do the hard work, msg should be nil on success
        
                                if( msg != NULL ) {                                                                             // returned message indicates send error of some sort
                                        rmr_free_msg( msg );                                                            // must ditchone; pick msg so we don't have to unfiddle flags
                                        msg = clone_m;
                                } else {
                                        ok_sends++;
                                        msg = clone_m;                                                                          // clone will be the next to send
                                }
                        } else {
                                msg = send_msg( ctx, msg, nn_sock, max_to );                    // send the last, and allocate a new buffer; drops the clone if it was
                                if( DEBUG ) {
                                        if( msg == NULL ) {
                                                fprintf( stderr, "[DBUG] mtosend_msg:  send returned nil message!\n" );         
                                        }
                                }
                        }
                } else {
                        if( ctx->flags & CTXFL_WARN ) {
                                fprintf( stderr, "[WARN] invalid socket for rte, setting no endpoint err: mtype=%d sub_id=%d\n", msg->mtype, msg->sub_id );
                        }
                        msg->state = RMR_ERR_NOENDPT;
                        errno = ENXIO;
                }
        }

        if( msg ) {                                                     // call functions don't get a buffer back, so a nil check is required
                msg->flags &= ~MFL_NOALLOC;             // must return with this flag off
                if( ok_sends ) {                                // multiple rr-groups and one was successful; report ok
                        msg->state = RMR_OK;
                }
        
                if( DEBUG ) fprintf( stderr, "[DBUG] final send stats: ok=%d group=%d state=%d\n\n", ok_sends, group, msg->state );
        
                msg->tp_state = errno;
        }

        return msg;                                                                     // last message caries the status of last/only send attempt
}


/*
        A generic wrapper to the real send to keep wormhole stuff agnostic.
        We assume the wormhole function vetted the buffer so we don't have to.
*/
static rmr_mbuf_t* send2ep( uta_ctx_t* ctx, endpoint_t* ep, rmr_mbuf_t* msg ) {
        return send_msg( ctx, msg, ep->nn_sock, -1 );
}

#endif