Fix SI95 transport header length bug

[ric-plt/lib/rmr.git] / src / rmr / si / src / sr_si_static.c

// vim: ts=4 sw=4 noet :
/*
==================================================================================
        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.
==================================================================================
*/

/*
        Mnemonic:       sr_si_static.c
        Abstract:       These are static send/receive primatives which (sadly)
                                differ based on the underlying protocol (nng vs SI95).
                                Split from rmr_nng.c  for easier wormhole support.

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

#ifndef _sr_si_static_c
#define _sr_si_static_c

static void dump_n( char *p, char* label, int n ) {
        int i;
        int j;
        int t = 0;
        int     rows;


        if( label ) {
                fprintf( stderr, "[DUMP] %s p=%p %d bytes\n", label, p, n );
        }

        rows = (n/16) + ((n % 16) ? 1 : 0);

        for( j = 0; j < rows; j++ ) {
                fprintf( stderr, "[DUMP] %04x: ", j * 16 );

                for( i = 0; t < n && i < 16; i++, t++ ) {
                        fprintf( stderr, "%02x ", (unsigned char) *p );
                        p++;
                }
                fprintf( stderr, "\n" );
        }
}

/*
        backwards compatability.
*/
static void dump_40( char *p, char* label ) {
        dump_n( p, label, 40 );
}

/*
        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_si_state( int state, int def_state ) {

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

                default:
                        state = def_state;
                        errno = EAGAIN;
                        break;

                case SI_ERR_QUEUED:
                case SI_ERR_TPORT:
                case SI_ERR_UPORT:
                case SI_ERR_FORK:
                case SI_ERR_HANDLE:
                case SI_ERR_SESSID:
                case SI_ERR_TP:
                case SI_ERR_SHUTD:
                case SI_ERR_NOFDS:
                case SI_ERR_SIGUSR1:
                case SI_ERR_SIGUSR2:
                case SI_ERR_DISC:
                case SI_ERR_TIMEOUT:
                case SI_ERR_ORDREL:
                case SI_ERR_SIGALRM:
                case SI_ERR_NOMEM:
                case SI_ERR_ADDR:
                        errno  = ENOTSUP;
                        state = def_state;
                        break;
        }

        return state;
}

/*
        Given a message size and a buffer (assumed to be TP_SZFIELD_LEN or larger)
        this will put in the size such that it is compatable with old versions
        of RMR (that expect the message size to not be in network byte order)
        and with new versions that do. See extract function in mt_call_si_static.c
        for details on what ends up in the buffer.
*/
static inline void insert_mlen( uint32_t len, char* buf ) {
        uint32_t* blen;                                                 // pointer into buffer where we'll add the len

        blen = (uint32_t *) buf;                                // old systems expect an unconverted integer
        *blen = len;

        blen++;
        *blen = htonl( len );                                   // new systems want a converted integer

        memset( &buf[TP_SZFIELD_LEN], 0, 4 );   // clear to prevent future conversion issues
        buf[TP_SZFIELD_LEN-1] = TP_SZ_MARKER;   // marker to flag this is generated by a new message
}

/*
        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 = -1;                      // size of the transport buffer that we'll allocate
        uta_mhdr_t*     hdr;                    // convenience pointer
        int                     tr_len;                 // trace data len (default or override)
        int*            alen;                   // convenience pointer to set allocated len

        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
        mlen = sizeof( char ) * (mlen + TP_HDR_LEN);                                            // finally add the transport header len

        if( msg == NULL && (msg = (rmr_mbuf_t *) uta_ring_extract( ctx->zcb_mring )) == NULL ) {
                msg = (rmr_mbuf_t *) malloc( sizeof *msg );
                if( msg == NULL ) {
                        rmr_vlog( RMR_VL_CRIT, "rmr_alloc_zc: cannot get memory for message\n" );
                        return NULL;                                                            // we used to exit -- that seems wrong
                }
                memset( msg, 0, sizeof( *msg ) );       // tp_buffer will be allocated below
        } else {                                                                // user message or message from the ring
                if( mlen > msg->alloc_len ) {           // current allocation is too small
                        msg->alloc_len = 0;                             // force tp_buffer realloc below
                        if( msg->tp_buf ) {
                                free( msg->tp_buf );
                                msg->tp_buf = NULL;
                        }
                } else {
                        mlen = msg->alloc_len;                                                  // msg given, allocate the same size as before
                }
        }

        msg->rts_fd = -1;                                       // must force to be invalid; not a received message that can be returned

        if( !msg->alloc_len && (msg->tp_buf = (void *) malloc( mlen )) == NULL ) {
                rmr_vlog( RMR_VL_CRIT, "rmr_alloc_zc: cannot get memory for zero copy buffer: %d bytes\n", (int) mlen );
                abort( );                                                                                       // toss out a core file for this
        }

        if( DEBUG ) {
                // for speed we don't do this in production; for testing valgrind will complain about uninitialised use if not set
                memset( msg->tp_buf, 0, mlen );
                memcpy( msg->tp_buf, "@@!!@@!!@@!!@@!!@@!!@@!!@@!!@@!!==", 34 );                // do NOT use a $ in this string!
        }

        insert_mlen( (uint32_t) mlen, msg->tp_buf );                    // this will likely be overwriten on send to shirnk

        msg->header = ((char *) msg->tp_buf) + TP_HDR_LEN;
        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->cookie = 0x4942;
        msg->alloc_len = mlen;                                                                  // length of allocated transport buffer (caller size + rmr header)
        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
        msg->ring = ctx->zcb_mring;                                                             // original msg_free() api doesn't get context so must dup on eaach :(
        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 ) rmr_vlog( RMR_VL_DEBUG, "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
        transport receive should 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;

        if( (msg = (rmr_mbuf_t *) uta_ring_extract( ctx->zcb_mring )) != NULL ) {
                if( msg->tp_buf ) {
                        free( msg->tp_buf );            // caller doesn't want it -- future put this on an accumulation ring
                }
        } else {
                if( (msg = (rmr_mbuf_t *) malloc( sizeof *msg )) == NULL ) {
                        rmr_vlog( RMR_VL_CRIT, "rmr_alloc_mbuf: cannot get memory for message\n" );
                        return NULL;                                                    // this used to exit, but that seems wrong
                }
        }

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

        msg->cookie = 0x4942;
        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 = 0;
        msg->payload = NULL;
        msg->xaction = NULL;
        msg->state = state;
        msg->flags = 0;
        msg->ring = ctx->zcb_mring;                                                     // original msg_free() api doesn't get context so must dup on eaach :(

        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 si receive and the actual alloc len might be larger, but we
        can only assume this is the total usable space. Because we are managing a transport
        header in the first n bytes of the real msg, we must adjust this length down by the
        size of the tp header (for testing 50 bytes, but this should change to a struct if
        we adopt this interface).

        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 = ((char *) msg->tp_buf) + TP_HDR_LEN;

        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 ) {
                rmr_vlog( RMR_VL_CRIT, "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( (nm->tp_buf = (void *) malloc( sizeof( char ) * (mlen + TP_HDR_LEN) )) == NULL ) {
                rmr_vlog( RMR_VL_CRIT, "rmr_si_clone: cannot get memory for zero copy buffer: %d\n", (int) mlen );
                abort();
        }

        nm->header = ((char *) nm->tp_buf) + TP_HDR_LEN;
        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[0];                                                             // 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
        int*    alen;                   // convenience pointer to set toal xmit len FIX ME!
        int             tpb_len;                // total transmit buffer len (user space, rmr header and tp header)

        nm = (rmr_mbuf_t *) malloc( sizeof *nm );
        if( nm == NULL ) {
                rmr_vlog( RMR_VL_CRIT, "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 ) rmr_vlog( RMR_VL_DEBUG, "tr_realloc old size=%d new size=%d new tr_len=%d\n", (int) old_msg->alloc_len, (int) mlen, (int) tr_len );

        tpb_len = mlen + TP_HDR_LEN;
        if( (nm->tp_buf = (void *) malloc( tpb_len)) == NULL ) {
                rmr_vlog( RMR_VL_CRIT, "rmr_clone: cannot get memory for zero copy buffer: %d\n", ENOMEM );
                exit( 1 );
        }
        if( DEBUG ) {
                memset( nm->tp_buf, 0, tpb_len );
                memcpy( nm->tp_buf, "@@!!@@!!@@!!@@!!@@!!@@!!@@!!@@!!==", 34 );         // DEBUGGING do NOT use $ in this string!!
        }

        insert_mlen( (uint32_t) tpb_len, nm->tp_buf );                  // this len will likely be reset on send to shrink

        nm->header = ((char *) nm->tp_buf) + TP_HDR_LEN;

        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[0];                                                             // 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;
}

/*
        Realloc the message such that the payload is at least payload_len bytes.
        The clone and copy options affect what portion of the original payload is copied to
        the reallocated message, and whether or not the original payload is lost after the
        reallocation process has finished.

                copy == true
                The entire payload from the original message will be coppied to the reallocated
                payload.

                copy == false
                Only the header (preserving return to sender information, message type, etc)
                is preserved after reallocation; the payload used lengrh is set to 0 and the
                payload is NOT initialised/cleared.

                clone == true
                The orignal message is preserved and a completely new message buffer and payload
                are allocated (even if the size given is the same). A pointer to the new message
                buffer is returned and it is the user application's responsibility to manage the
                old buffer (e.g. free when not needed).

                clone == false
                The old payload will be lost after reallocation. The message buffer pointer which
                is returned will likely reference the same structure (don't depend on that).


        CAUTION:
        If the message is not a message which was received, the mtype, sub-id, length values in the
        RMR header in the allocated transport buffer will NOT be accurate and will cause the resulting
        mbuffer information for mtype and subid to be reset even when copy is true. To avoid silently
        resetting information in the mbuffer, this funciton will reset the mbuf values from the current
        settings and NOT from the copied RMR header in transport buffer.
*/
static inline rmr_mbuf_t* realloc_payload( rmr_mbuf_t* old_msg, int payload_len, int copy, int clone ) {
        rmr_mbuf_t* nm = NULL;  // new message buffer when cloning
        size_t  mlen;
        uta_mhdr_t* omhdr;              // old message header
        int             tr_old_len;             // tr size in new buffer
        int             old_psize = 0;  // size of payload in the message passed in (alloc size - tp header and rmr header lengths)
        int             hdr_len = 0;    // length of RMR and transport headers in old msg
        void*   old_tp_buf;             // pointer to the old tp buffer
        int             free_tp = 1;    // free the transport buffer (old) when done (when not cloning)
        int             old_mt;                 // msg type and sub-id from the message passed in
        int             old_sid;
        int             old_len;
        int             old_rfd;                // rts file descriptor from old message

        if( old_msg == NULL || payload_len <= 0 ) {
                errno = EINVAL;
                return NULL;
        }

        old_mt = old_msg->mtype;                        // preserve mbuf info
        old_sid = old_msg->sub_id;
        old_len = old_msg->len;
        old_rfd = old_msg->rts_fd;

        old_psize = old_msg->alloc_len - (RMR_HDR_LEN( old_msg->header ) + TP_HDR_LEN);         // user payload size in orig message

        if( !clone  && payload_len <= old_psize ) {                                                                             // not cloning and old is large enough; nothing to do
                if( DEBUG ) rmr_vlog( RMR_VL_DEBUG, "rmr_realloc_payload: old msg payload larger than requested: cur=%d need=%d\n", old_psize, payload_len );
                return old_msg;
        }

        hdr_len = RMR_HDR_LEN( old_msg->header ) + TP_HDR_LEN;                          // with SI we manage the transport header; must include in len
        old_tp_buf = old_msg->tp_buf;

        if( clone ) {
                if( DEBUG ) rmr_vlog( RMR_VL_DEBUG, "rmr_realloc_payload: cloning message\n" );
                free_tp = 0;

                nm = (rmr_mbuf_t *) malloc( sizeof( *nm ) );
                if( nm == NULL ) {
                        rmr_vlog( RMR_VL_CRIT, "rmr_realloc_payload: cannot get memory for message buffer. bytes requested: %d\n", (int) sizeof(*nm) );
                        return NULL;
                }
                memset( nm, 0, sizeof( *nm ) );
                nm->rts_fd = old_rfd;                           // this is managed only in the mbuf; dup now
        } else {
                nm = old_msg;
        }

        omhdr = old_msg->header;
        mlen = hdr_len + (payload_len > old_psize ? payload_len : old_psize);           // must have larger in case copy is true

        if( DEBUG ) rmr_vlog( RMR_VL_DEBUG, "reallocate for payload increase. new message size: %d\n", (int) mlen );
        if( (nm->tp_buf = (char *) malloc( sizeof( char ) * mlen )) == NULL ) {
                rmr_vlog( RMR_VL_CRIT, "rmr_realloc_payload: cannot get memory for zero copy buffer. bytes requested: %d\n", (int) mlen );
                free( nm );
                return NULL;
        }

        nm->header = ((char *) nm->tp_buf) + TP_HDR_LEN;                        // point at the new header and copy from old
        SET_HDR_LEN( nm->header );

        if( copy ) {                                                                                                                            // if we need to copy the old payload too
                if( DEBUG ) rmr_vlog( RMR_VL_DEBUG, "rmr_realloc_payload: copy payload into new message: %d bytes\n", old_psize );
                memcpy( nm->header, omhdr, sizeof( char ) * (old_psize + RMR_HDR_LEN( omhdr )) );
        } else {                                                                                                                                        // just need to copy header
                if( DEBUG ) rmr_vlog( RMR_VL_DEBUG, "rmr_realloc_payload: copy only header into new message: %d bytes\n", RMR_HDR_LEN( nm->header ) );
                memcpy( nm->header, omhdr, sizeof( char ) * RMR_HDR_LEN( omhdr ) );
        }

        ref_tpbuf( nm, mlen );                  // set payload and other pointers in the message to the new tp buffer

        if( !copy ) {
                nm->mtype = -1;                                         // didn't copy payload, so mtype, sub-id, and rts fd are invalid
                nm->sub_id = -1;
                nm->len = 0;                                            // and len is 0
        } else {
                nm->len = old_len;                                      // we must force these to avoid losing info if msg wasn't a received message
                nm->mtype = old_mt;
                nm->sub_id = old_sid;
        }

        if( free_tp ) {
                free( old_tp_buf );                             // we did not clone, so free b/c no references
        }

        return nm;
}

/*
        For SI95 based transport all receives are driven through the threaded
        ring and thus this function should NOT be called. If it is we will panic
        and abort straight away.
*/
static rmr_mbuf_t* rcv_msg( uta_ctx_t* ctx, rmr_mbuf_t* old_msg ) {

fprintf( stderr, "\n\n>>> rcv_msg: bad things just happened!\n\n>>>>>> abort!  rcv_msg called and it shouldn't be\n" );
exit( 1 );

        return NULL;
}

/*
        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, int nn_sock, int retries ) {
        int state;
        uta_mhdr_t*     hdr;
        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 sizes
        int tot_len;                                                    // total send length (hdr + user data + tp header)

        // 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 );
        }

        if( retries == 0 ) {
                spin_retries = 100;
                retries++;
        }

        errno = 0;
        msg->state = RMR_OK;
        do {
                tot_len = msg->len + PAYLOAD_OFFSET( hdr ) + TP_HDR_LEN;                        // we only send what was used + header lengths
                if( tot_len > msg->alloc_len ) {
                        tot_len = msg->alloc_len;                                                                       // likely bad length from user :(
                }
                insert_mlen( tot_len, msg->tp_buf );    // shrink to fit

                if( DEBUG > 1 ) rmr_vlog( RMR_VL_DEBUG, "send_msg: ending %d (%x) bytes  usr_len=%d alloc=%d retries=%d\n", tot_len, tot_len, msg->len, msg->alloc_len, retries );
                if( DEBUG > 2 ) dump_40( msg->tp_buf, "sending" );

                if( (state = SIsendt( ctx->si_ctx, nn_sock, msg->tp_buf, tot_len )) != SI_OK ) {
                        if( DEBUG > 1 ) rmr_vlog( RMR_VL_DEBUG, "send_msg:  error!! sent state=%d\n", state );
                        msg->state = state;
                        if( retries > 0 && state == SI_ERR_BLOCKED ) {
                                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
                        }
                } else {
                        if( DEBUG > 2 ) rmr_vlog( RMR_VL_DEBUG, "sent OK state=%d\n", state );
                        state = 0;
                        msg->state = RMR_OK;
                        hdr = NULL;
                }
        } while( state && retries > 0 );

        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 == 98 ) {                // FIX ME: this is just broken, but needs SI changes to work correctly for us
                        errno = EAGAIN;
                        msg->state = RMR_ERR_RETRY;                                     // errno will have nano reason
                } else {
                        msg->state = RMR_ERR_SENDFAILED;
                }

                if( DEBUG ) rmr_vlog( RMR_VL_DEBUG, "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 ) {
        endpoint_t*     ep;                                     // end point that we're attempting to send to
        rtable_ent_t*   rte;                    // the route table entry which matches the message key
        int     nn_sock;                                        // endpoint socket (fd in si case) 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_mtosend_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
                rmr_vlog( RMR_VL_WARN, "no route table entry 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 ) {
                if( rte->nrrgroups > 0 ) {                                                      // this is a round robin entry if groups are listed
                        sock_ok = uta_epsock_rr( ctx, rte, group, &send_again, &nn_sock, &ep );         // select endpt from rr group and set again if more groups
                } else {
                        sock_ok = epsock_meid( ctx, ctx->rtable, msg, &nn_sock, &ep );
                        send_again = 0;
                }

                if( DEBUG ) rmr_vlog( RMR_VL_DEBUG, "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;
                                        rmr_vlog( RMR_VL_WARN, "unable to clone message for multiple rr-group send\n" );
                                        return msg;
                                }

                                if( DEBUG ) rmr_vlog( RMR_VL_DEBUG, "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
                                        msg->state = RMR_OK;
                                }
                        } 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 ) {
                                                rmr_vlog( RMR_VL_DEBUG, "mtosend_msg:  send returned nil message!\n" );
                                        }
                                }
                        }

                        if( ep != NULL && msg != NULL ) {
                                switch( msg->state ) {
                                        case RMR_OK:
                                                ep->scounts[EPSC_GOOD]++;
                                                break;
        
                                        case RMR_ERR_RETRY:
                                                ep->scounts[EPSC_TRANS]++;
                                                break;

                                        default:
                                                ep->scounts[EPSC_FAIL]++;
                                                uta_ep_failed( ep );                                                            // sending to ep failed; set up to reconnect
                                                break;
                                }
                        }
                } else {
                        if( DEBUG ) rmr_vlog( RMR_VL_DEBUG, "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 ) rmr_vlog( RMR_VL_DEBUG, "final send stats: ok=%d group=%d state=%d\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