/*
 * Copyright (c) 2011-2015 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@dragonflybsd.org>
 * by Venkatesh Srinivas <vsrinivas@dragonflybsd.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "dmsg_local.h"

#define DMSG_BLOCK_DEBUG

int DMsgDebugOpt;
static unsigned int dmsg_state_count;
#ifdef DMSG_BLOCK_DEBUG
static unsigned int biocount;
#endif

static int dmsg_state_msgrx(dmsg_msg_t *msg, int mstate);
static void dmsg_state_cleanuptx(dmsg_iocom_t *iocom, dmsg_msg_t *msg);
static void dmsg_msg_free_locked(dmsg_msg_t *msg);
static void dmsg_state_free(dmsg_state_t *state);
static void dmsg_subq_delete(dmsg_state_t *state);
static void dmsg_simulate_failure(dmsg_state_t *state, int meto, int error);
static void dmsg_state_abort(dmsg_state_t *state);
static void dmsg_state_dying(dmsg_state_t *state);

RB_GENERATE(dmsg_state_tree, dmsg_state, rbnode, dmsg_state_cmp);

/*
 * STATE TREE - Represents open transactions which are indexed by their
 *              { msgid } relative to the governing iocom.
 */
int
dmsg_state_cmp(dmsg_state_t *state1, dmsg_state_t *state2)
{
        if (state1->msgid < state2->msgid)
                return(-1);
        if (state1->msgid > state2->msgid)
                return(1);
        return(0);
}

/*
 * Initialize a low-level ioq
 */
void
dmsg_ioq_init(dmsg_iocom_t *iocom __unused, dmsg_ioq_t *ioq)
{
        bzero(ioq, sizeof(*ioq));
        ioq->state = DMSG_MSGQ_STATE_HEADER1;
        TAILQ_INIT(&ioq->msgq);
}

/*
 * Cleanup queue.
 *
 * caller holds iocom->mtx.
 */
void
dmsg_ioq_done(dmsg_iocom_t *iocom __unused, dmsg_ioq_t *ioq)
{
        dmsg_msg_t *msg;

        while ((msg = TAILQ_FIRST(&ioq->msgq)) != NULL) {
                assert(0);      /* shouldn't happen */
                TAILQ_REMOVE(&ioq->msgq, msg, qentry);
                dmsg_msg_free(msg);
        }
        if ((msg = ioq->msg) != NULL) {
                ioq->msg = NULL;
                dmsg_msg_free(msg);
        }
}

/*
 * Initialize a low-level communications channel.
 *
 * NOTE: The signal_func() is called at least once from the loop and can be
 *       re-armed via dmsg_iocom_restate().
 */
void
dmsg_iocom_init(dmsg_iocom_t *iocom, int sock_fd, int alt_fd,
                   void (*signal_func)(dmsg_iocom_t *iocom),
                   void (*rcvmsg_func)(dmsg_msg_t *msg),
                   void (*usrmsg_func)(dmsg_msg_t *msg, int unmanaged),
                   void (*altmsg_func)(dmsg_iocom_t *iocom))
{
        struct stat st;

        bzero(iocom, sizeof(*iocom));

        asprintf(&iocom->label, "iocom-%p", iocom);
        iocom->signal_callback = signal_func;
        iocom->rcvmsg_callback = rcvmsg_func;
        iocom->altmsg_callback = altmsg_func;
        iocom->usrmsg_callback = usrmsg_func;

        pthread_mutex_init(&iocom->mtx, NULL);
        RB_INIT(&iocom->staterd_tree);
        RB_INIT(&iocom->statewr_tree);
        TAILQ_INIT(&iocom->txmsgq);
        iocom->sock_fd = sock_fd;
        iocom->alt_fd = alt_fd;
        iocom->flags = DMSG_IOCOMF_RREQ | DMSG_IOCOMF_CLOSEALT;
        if (signal_func)
                iocom->flags |= DMSG_IOCOMF_SWORK;
        dmsg_ioq_init(iocom, &iocom->ioq_rx);
        dmsg_ioq_init(iocom, &iocom->ioq_tx);
        iocom->state0.refs = 1;         /* should never trigger a free */
        iocom->state0.iocom = iocom;
        iocom->state0.parent = &iocom->state0;
        iocom->state0.flags = DMSG_STATE_ROOT;
        TAILQ_INIT(&iocom->state0.subq);

        if (pipe(iocom->wakeupfds) < 0)
                assert(0);
        fcntl(iocom->wakeupfds[0], F_SETFL, O_NONBLOCK);
        fcntl(iocom->wakeupfds[1], F_SETFL, O_NONBLOCK);

        /*
         * Negotiate session crypto synchronously.  This will mark the
         * connection as error'd if it fails.  If this is a pipe it's
         * a linkage that we set up ourselves to the filesystem and there
         * is no crypto.
         */
        if (fstat(sock_fd, &st) < 0)
                assert(0);
        if (S_ISSOCK(st.st_mode))
                dmsg_crypto_negotiate(iocom);

        /*
         * Make sure our fds are set to non-blocking for the iocom core.
         */
        if (sock_fd >= 0)
                fcntl(sock_fd, F_SETFL, O_NONBLOCK);
#if 0
        /* if line buffered our single fgets() should be fine */
        if (alt_fd >= 0)
                fcntl(alt_fd, F_SETFL, O_NONBLOCK);
#endif
}

void
dmsg_iocom_label(dmsg_iocom_t *iocom, const char *ctl, ...)
{
        va_list va;
        char *optr;

        va_start(va, ctl);
        optr = iocom->label;
        vasprintf(&iocom->label, ctl, va);
        va_end(va);
        if (optr)
                free(optr);
}

/*
 * May only be called from a callback from iocom_core.
 *
 * Adjust state machine functions, set flags to guarantee that both
 * the recevmsg_func and the sendmsg_func is called at least once.
 */
void
dmsg_iocom_restate(dmsg_iocom_t *iocom,
                   void (*signal_func)(dmsg_iocom_t *),
                   void (*rcvmsg_func)(dmsg_msg_t *msg))
{
        pthread_mutex_lock(&iocom->mtx);
        iocom->signal_callback = signal_func;
        iocom->rcvmsg_callback = rcvmsg_func;
        if (signal_func)
                atomic_set_int(&iocom->flags, DMSG_IOCOMF_SWORK);
        else
                atomic_clear_int(&iocom->flags, DMSG_IOCOMF_SWORK);
        pthread_mutex_unlock(&iocom->mtx);
}

void
dmsg_iocom_signal(dmsg_iocom_t *iocom)
{
        pthread_mutex_lock(&iocom->mtx);
        if (iocom->signal_callback)
                atomic_set_int(&iocom->flags, DMSG_IOCOMF_SWORK);
        pthread_mutex_unlock(&iocom->mtx);
}

/*
 * Cleanup a terminating iocom.
 *
 * Caller should not hold iocom->mtx.  The iocom has already been disconnected
 * from all possible references to it.
 */
void
dmsg_iocom_done(dmsg_iocom_t *iocom)
{
        dmsg_crypto_terminate(iocom);
        if (iocom->sock_fd >= 0) {
                close(iocom->sock_fd);
                iocom->sock_fd = -1;
        }
        if (iocom->alt_fd >= 0 && (iocom->flags & DMSG_IOCOMF_CLOSEALT)) {
                close(iocom->alt_fd);
                iocom->alt_fd = -1;
        }
        dmsg_ioq_done(iocom, &iocom->ioq_rx);
        dmsg_ioq_done(iocom, &iocom->ioq_tx);
        if (iocom->wakeupfds[0] >= 0) {
                close(iocom->wakeupfds[0]);
                iocom->wakeupfds[0] = -1;
        }
        if (iocom->wakeupfds[1] >= 0) {
                close(iocom->wakeupfds[1]);
                iocom->wakeupfds[1] = -1;
        }
        pthread_mutex_destroy(&iocom->mtx);
}

/*
 * Allocate a new message using the specified transaction state.
 *
 * If CREATE is set a new transaction is allocated relative to the passed-in
 * transaction (the 'state' argument becomes pstate).
 *
 * If CREATE is not set the message is associated with the passed-in
 * transaction.
 */
dmsg_msg_t *
dmsg_msg_alloc(dmsg_state_t *state,
               size_t aux_size, uint32_t cmd,
               void (*func)(dmsg_msg_t *), void *data)
{
        dmsg_iocom_t *iocom = state->iocom;
        dmsg_msg_t *msg;

        pthread_mutex_lock(&iocom->mtx);
        msg = dmsg_msg_alloc_locked(state, aux_size, cmd, func, data);
        pthread_mutex_unlock(&iocom->mtx);

        return msg;
}

dmsg_msg_t *
dmsg_msg_alloc_locked(dmsg_state_t *state,
               size_t aux_size, uint32_t cmd,
               void (*func)(dmsg_msg_t *), void *data)
{
        dmsg_iocom_t *iocom = state->iocom;
        dmsg_state_t *pstate;
        dmsg_msg_t *msg;
        int hbytes;
        size_t aligned_size;

        aligned_size = DMSG_DOALIGN(aux_size);
        if ((cmd & (DMSGF_CREATE | DMSGF_REPLY)) == DMSGF_CREATE) {
                /*
                 * When CREATE is set without REPLY the caller is
                 * initiating a new transaction stacked under the specified
                 * circuit.
                 *
                 * It is possible to race a circuit failure, inherit the
                 * parent's STATE_DYING flag to trigger an abort sequence
                 * in the transmit path.  By not inheriting ABORTING the
                 * abort sequence can recurse.
                 *
                 * NOTE: CREATE in txcmd handled by dmsg_msg_write()
                 * NOTE: DELETE in txcmd handled by dmsg_state_cleanuptx()
                 */
                pstate = state;
                state = malloc(sizeof(*state));
                bzero(state, sizeof(*state));
                atomic_add_int(&dmsg_state_count, 1);

                TAILQ_INIT(&state->subq);
                state->parent = pstate;
                state->iocom = iocom;
                state->flags = DMSG_STATE_DYNAMIC;
                state->msgid = (uint64_t)(uintptr_t)state;
                state->txcmd = cmd & ~(DMSGF_CREATE | DMSGF_DELETE);
                state->rxcmd = DMSGF_REPLY;
                state->icmd = state->txcmd & DMSGF_BASECMDMASK;
                state->func = func;
                state->any.any = data;

                state->flags |= DMSG_STATE_SUBINSERTED |
                                DMSG_STATE_RBINSERTED;
                state->flags |= pstate->flags & DMSG_STATE_DYING;
                if (TAILQ_EMPTY(&pstate->subq))
                        dmsg_state_hold(pstate);
                RB_INSERT(dmsg_state_tree, &iocom->statewr_tree, state);
                TAILQ_INSERT_TAIL(&pstate->subq, state, entry);
                dmsg_state_hold(state);         /* state on pstate->subq */
                dmsg_state_hold(state);         /* state on rbtree */
                dmsg_state_hold(state);         /* msg->state */
        } else {
                /*
                 * Otherwise the message is transmitted over the existing
                 * open transaction.
                 */
                pstate = state->parent;
                dmsg_state_hold(state);         /* msg->state */
        }

        /* XXX SMP race for state */
        hbytes = (cmd & DMSGF_SIZE) * DMSG_ALIGN;
        assert((size_t)hbytes >= sizeof(struct dmsg_hdr));
        msg = malloc(offsetof(struct dmsg_msg, any.head) + hbytes);
        bzero(msg, offsetof(struct dmsg_msg, any.head));

        /*
         * [re]allocate the auxillary data buffer.  The caller knows that
         * a size-aligned buffer will be allocated but we do not want to
         * force the caller to zero any tail piece, so we do that ourself.
         */
        if (msg->aux_size != aux_size) {
                if (msg->aux_data) {
                        free(msg->aux_data);
                        msg->aux_data = NULL;
                        msg->aux_size = 0;
                }
                if (aux_size) {
                        msg->aux_data = malloc(aligned_size);
                        msg->aux_size = aux_size;
                        if (aux_size != aligned_size) {
                                bzero(msg->aux_data + aux_size,
                                      aligned_size - aux_size);
                        }
                }
        }

        /*
         * Set REVTRANS if the transaction was remotely initiated
         * Set REVCIRC if the circuit was remotely initiated
         */
        if (state->flags & DMSG_STATE_OPPOSITE)
                cmd |= DMSGF_REVTRANS;
        if (pstate->flags & DMSG_STATE_OPPOSITE)
                cmd |= DMSGF_REVCIRC;

        /*
         * Finish filling out the header.
         */
        bzero(&msg->any.head, hbytes);
        msg->hdr_size = hbytes;
        msg->any.head.magic = DMSG_HDR_MAGIC;
        msg->any.head.cmd = cmd;
        msg->any.head.aux_descr = 0;
        msg->any.head.aux_crc = 0;
        msg->any.head.msgid = state->msgid;
        msg->any.head.circuit = pstate->msgid;
        msg->state = state;

        return (msg);
}

/*
 * Free a message so it can be reused afresh.
 *
 * NOTE: aux_size can be 0 with a non-NULL aux_data.
 */
static
void
dmsg_msg_free_locked(dmsg_msg_t *msg)
{
        dmsg_state_t *state;

        if ((state = msg->state) != NULL) {
                dmsg_state_drop(state);
                msg->state = NULL;      /* safety */
        }
        if (msg->aux_data) {
                free(msg->aux_data);
                msg->aux_data = NULL;   /* safety */
        }
        msg->aux_size = 0;
        free (msg);
}

void
dmsg_msg_free(dmsg_msg_t *msg)
{
        dmsg_iocom_t *iocom = msg->state->iocom;

        pthread_mutex_lock(&iocom->mtx);
        dmsg_msg_free_locked(msg);
        pthread_mutex_unlock(&iocom->mtx);
}

/*
 * I/O core loop for an iocom.
 *
 * Thread localized, iocom->mtx not held.
 */
void
dmsg_iocom_core(dmsg_iocom_t *iocom)
{
        struct pollfd fds[3];
        char dummybuf[256];
        dmsg_msg_t *msg;
        int timeout;
        int count;
        int wi; /* wakeup pipe */
        int si; /* socket */
        int ai; /* alt bulk path socket */

        while ((iocom->flags & DMSG_IOCOMF_EOF) == 0) {
                /*
                 * These iocom->flags are only manipulated within the
                 * context of the current thread.  However, modifications
                 * still require atomic ops.
                 */
                dmio_printf(iocom, 5, "iocom %p %08x\n",
                            iocom, iocom->flags);
                if ((iocom->flags & (DMSG_IOCOMF_RWORK |
                                     DMSG_IOCOMF_WWORK |
                                     DMSG_IOCOMF_PWORK |
                                     DMSG_IOCOMF_SWORK |
                                     DMSG_IOCOMF_ARWORK |
                                     DMSG_IOCOMF_AWWORK)) == 0) {
                        /*
                         * Only poll if no immediate work is pending.
                         * Otherwise we are just wasting our time calling
                         * poll.
                         */
                        timeout = 5000;

                        count = 0;
                        wi = -1;
                        si = -1;
                        ai = -1;

                        /*
                         * Always check the inter-thread pipe, e.g.
                         * for iocom->txmsgq work.
                         */
                        wi = count++;
                        fds[wi].fd = iocom->wakeupfds[0];
                        fds[wi].events = POLLIN;
                        fds[wi].revents = 0;

                        /*
                         * Check the socket input/output direction as
                         * requested
                         */
                        if (iocom->flags & (DMSG_IOCOMF_RREQ |
                                            DMSG_IOCOMF_WREQ)) {
                                si = count++;
                                fds[si].fd = iocom->sock_fd;
                                fds[si].events = 0;
                                fds[si].revents = 0;

                                if (iocom->flags & DMSG_IOCOMF_RREQ)
                                        fds[si].events |= POLLIN;
                                if (iocom->flags & DMSG_IOCOMF_WREQ)
                                        fds[si].events |= POLLOUT;
                        }

                        /*
                         * Check the alternative fd for work.
                         */
                        if (iocom->alt_fd >= 0) {
                                ai = count++;
                                fds[ai].fd = iocom->alt_fd;
                                fds[ai].events = POLLIN;
                                fds[ai].revents = 0;
                        }
                        poll(fds, count, timeout);

                        if (wi >= 0 && (fds[wi].revents & POLLIN))
                                atomic_set_int(&iocom->flags,
                                               DMSG_IOCOMF_PWORK);
                        if (si >= 0 && (fds[si].revents & POLLIN))
                                atomic_set_int(&iocom->flags,
                                               DMSG_IOCOMF_RWORK);
                        if (si >= 0 && (fds[si].revents & POLLOUT))
                                atomic_set_int(&iocom->flags,
                                               DMSG_IOCOMF_WWORK);
                        if (wi >= 0 && (fds[wi].revents & POLLOUT))
                                atomic_set_int(&iocom->flags,
                                               DMSG_IOCOMF_WWORK);
                        if (ai >= 0 && (fds[ai].revents & POLLIN))
                                atomic_set_int(&iocom->flags,
                                               DMSG_IOCOMF_ARWORK);
                } else {
                        /*
                         * Always check the pipe
                         */
                        atomic_set_int(&iocom->flags, DMSG_IOCOMF_PWORK);
                }

                if (iocom->flags & DMSG_IOCOMF_SWORK) {
                        atomic_clear_int(&iocom->flags, DMSG_IOCOMF_SWORK);
                        iocom->signal_callback(iocom);
                }

                /*
                 * Pending message queues from other threads wake us up
                 * with a write to the wakeupfds[] pipe.  We have to clear
                 * the pipe with a dummy read.
                 */
                if (iocom->flags & DMSG_IOCOMF_PWORK) {
                        atomic_clear_int(&iocom->flags, DMSG_IOCOMF_PWORK);
                        read(iocom->wakeupfds[0], dummybuf, sizeof(dummybuf));
                        atomic_set_int(&iocom->flags, DMSG_IOCOMF_RWORK);
                        atomic_set_int(&iocom->flags, DMSG_IOCOMF_WWORK);
                }

                /*
                 * Message write sequencing
                 */
                if (iocom->flags & DMSG_IOCOMF_WWORK)
                        dmsg_iocom_flush1(iocom);

                /*
                 * Message read sequencing.  Run this after the write
                 * sequencing in case the write sequencing allowed another
                 * auto-DELETE to occur on the read side.
                 */
                if (iocom->flags & DMSG_IOCOMF_RWORK) {
                        while ((iocom->flags & DMSG_IOCOMF_EOF) == 0 &&
                               (msg = dmsg_ioq_read(iocom)) != NULL) {
                                dmio_printf(iocom, 4, "receive %s\n",
                                            dmsg_msg_str(msg));
                                iocom->rcvmsg_callback(msg);
                                pthread_mutex_lock(&iocom->mtx);
                                dmsg_state_cleanuprx(iocom, msg);
                                pthread_mutex_unlock(&iocom->mtx);
                        }
                }

                if (iocom->flags & DMSG_IOCOMF_ARWORK) {
                        atomic_clear_int(&iocom->flags, DMSG_IOCOMF_ARWORK);
                        iocom->altmsg_callback(iocom);
                }
        }
}

/*
 * Make sure there's enough room in the FIFO to hold the
 * needed data.
 *
 * Assume worst case encrypted form is 2x the size of the
 * plaintext equivalent.
 */
static
size_t
dmsg_ioq_makeroom(dmsg_ioq_t *ioq, size_t needed)
{
        size_t bytes;
        size_t nmax;

        bytes = ioq->fifo_cdx - ioq->fifo_beg;
        nmax = sizeof(ioq->buf) - ioq->fifo_end;
        if (bytes + nmax / 2 < needed) {
                if (bytes) {
                        bcopy(ioq->buf + ioq->fifo_beg,
                              ioq->buf,
                              bytes);
                }
                ioq->fifo_cdx -= ioq->fifo_beg;
                ioq->fifo_beg = 0;
                if (ioq->fifo_cdn < ioq->fifo_end) {
                        bcopy(ioq->buf + ioq->fifo_cdn,
                              ioq->buf + ioq->fifo_cdx,
                              ioq->fifo_end - ioq->fifo_cdn);
                }
                ioq->fifo_end -= ioq->fifo_cdn - ioq->fifo_cdx;
                ioq->fifo_cdn = ioq->fifo_cdx;
                nmax = sizeof(ioq->buf) - ioq->fifo_end;
        }
        return(nmax);
}

/*
 * Read the next ready message from the ioq, issuing I/O if needed.
 * Caller should retry on a read-event when NULL is returned.
 *
 * If an error occurs during reception a DMSG_LNK_ERROR msg will
 * be returned for each open transaction, then the ioq and iocom
 * will be errored out and a non-transactional DMSG_LNK_ERROR
 * msg will be returned as the final message.  The caller should not call
 * us again after the final message is returned.
 *
 * Thread localized, iocom->mtx not held.
 */
dmsg_msg_t *
dmsg_ioq_read(dmsg_iocom_t *iocom)
{
        dmsg_ioq_t *ioq = &iocom->ioq_rx;
        dmsg_msg_t *msg;
        dmsg_hdr_t *head;
        ssize_t n;
        size_t bytes;
        size_t nmax;
        uint32_t aux_size;
        uint32_t xcrc32;
        int error;

again:
        /*
         * If a message is already pending we can just remove and
         * return it.  Message state has already been processed.
         * (currently not implemented)
         */
        if ((msg = TAILQ_FIRST(&ioq->msgq)) != NULL) {
                TAILQ_REMOVE(&ioq->msgq, msg, qentry);

                if (msg->state == &iocom->state0) {
                        atomic_set_int(&iocom->flags, DMSG_IOCOMF_EOF);
                        dmio_printf(iocom, 1,
                                    "EOF ON SOCKET %d\n",
                                    iocom->sock_fd);
                }
                return (msg);
        }
        atomic_clear_int(&iocom->flags, DMSG_IOCOMF_RREQ | DMSG_IOCOMF_RWORK);

        /*
         * If the stream is errored out we stop processing it.
         */
        if (ioq->error)
                goto skip;

        /*
         * Message read in-progress (msg is NULL at the moment).  We don't
         * allocate a msg until we have its core header.
         */
        nmax = sizeof(ioq->buf) - ioq->fifo_end;
        bytes = ioq->fifo_cdx - ioq->fifo_beg;          /* already decrypted */
        msg = ioq->msg;

        switch(ioq->state) {
        case DMSG_MSGQ_STATE_HEADER1:
                /*
                 * Load the primary header, fail on any non-trivial read
                 * error or on EOF.  Since the primary header is the same
                 * size is the message alignment it will never straddle
                 * the end of the buffer.
                 */
                nmax = dmsg_ioq_makeroom(ioq, sizeof(msg->any.head));
                if (bytes < sizeof(msg->any.head)) {
                        n = read(iocom->sock_fd,
                                 ioq->buf + ioq->fifo_end,
                                 nmax);
                        if (n <= 0) {
                                if (n == 0) {
                                        ioq->error = DMSG_IOQ_ERROR_EOF;
                                        break;
                                }
                                if (errno != EINTR &&
                                    errno != EINPROGRESS &&
                                    errno != EAGAIN) {
                                        ioq->error = DMSG_IOQ_ERROR_SOCK;
                                        break;
                                }
                                n = 0;
                                /* fall through */
                        }
                        ioq->fifo_end += (size_t)n;
                        nmax -= (size_t)n;
                }

                /*
                 * Decrypt data received so far.  Data will be decrypted
                 * in-place but might create gaps in the FIFO.  Partial
                 * blocks are not immediately decrypted.
                 *
                 * WARNING!  The header might be in the wrong endian, we
                 *           do not fix it up until we get the entire
                 *           extended header.
                 */
                if (iocom->flags & DMSG_IOCOMF_CRYPTED) {
                        dmsg_crypto_decrypt(iocom, ioq);
                } else {
                        ioq->fifo_cdx = ioq->fifo_end;
                        ioq->fifo_cdn = ioq->fifo_end;
                }
                bytes = ioq->fifo_cdx - ioq->fifo_beg;

                /*
                 * Insufficient data accumulated (msg is NULL, caller will
                 * retry on event).
                 */
                assert(msg == NULL);
                if (bytes < sizeof(msg->any.head))
                        break;

                /*
                 * Check and fixup the core header.  Note that the icrc
                 * has to be calculated before any fixups, but the crc
                 * fields in the msg may have to be swapped like everything
                 * else.
                 */
                head = (void *)(ioq->buf + ioq->fifo_beg);
                if (head->magic != DMSG_HDR_MAGIC &&
                    head->magic != DMSG_HDR_MAGIC_REV) {
                        dmio_printf(iocom, 1,
                                    "%s: head->magic is bad %02x\n",
                                    iocom->label, head->magic);
                        if (iocom->flags & DMSG_IOCOMF_CRYPTED)
                                dmio_printf(iocom, 1, "%s\n",
                                            "(on encrypted link)");
                        ioq->error = DMSG_IOQ_ERROR_SYNC;
                        break;
                }

                /*
                 * Calculate the full header size and aux data size
                 */
                if (head->magic == DMSG_HDR_MAGIC_REV) {
                        ioq->hbytes = (bswap32(head->cmd) & DMSGF_SIZE) *
                                      DMSG_ALIGN;
                        aux_size = bswap32(head->aux_bytes);
                } else {
                        ioq->hbytes = (head->cmd & DMSGF_SIZE) *
                                      DMSG_ALIGN;
                        aux_size = head->aux_bytes;
                }
                ioq->abytes = DMSG_DOALIGN(aux_size);
                ioq->unaligned_aux_size = aux_size;
                if (ioq->hbytes < sizeof(msg->any.head) ||
                    ioq->hbytes > sizeof(msg->any) ||
                    ioq->abytes > DMSG_AUX_MAX) {
                        ioq->error = DMSG_IOQ_ERROR_FIELD;
                        break;
                }

                /*
                 * Allocate the message, the next state will fill it in.
                 *
                 * NOTE: The aux_data buffer will be sized to an aligned
                 *       value and the aligned remainder zero'd for
                 *       convenience.
                 *
                 * NOTE: Supply dummy state and a degenerate cmd without
                 *       CREATE set.  The message will temporarily be
                 *       associated with state0 until later post-processing.
                 */
                msg = dmsg_msg_alloc(&iocom->state0, aux_size,
                                     ioq->hbytes / DMSG_ALIGN,
                                     NULL, NULL);
                ioq->msg = msg;

                /*
                 * Fall through to the next state.  Make sure that the
                 * extended header does not straddle the end of the buffer.
                 * We still want to issue larger reads into our buffer,
                 * book-keeping is easier if we don't bcopy() yet.
                 *
                 * Make sure there is enough room for bloated encrypt data.
                 */
                nmax = dmsg_ioq_makeroom(ioq, ioq->hbytes);
                ioq->state = DMSG_MSGQ_STATE_HEADER2;
                /* fall through */
        case DMSG_MSGQ_STATE_HEADER2:
                /*
                 * Fill out the extended header.
                 */
                assert(msg != NULL);
                if (bytes < ioq->hbytes) {
                        assert(nmax > 0);
                        n = read(iocom->sock_fd,
                                 ioq->buf + ioq->fifo_end,
                                 nmax);
                        if (n <= 0) {
                                if (n == 0) {
                                        ioq->error = DMSG_IOQ_ERROR_EOF;
                                        break;
                                }
                                if (errno != EINTR &&
                                    errno != EINPROGRESS &&
                                    errno != EAGAIN) {
                                        ioq->error = DMSG_IOQ_ERROR_SOCK;
                                        break;
                                }
                                n = 0;
                                /* fall through */
                        }
                        ioq->fifo_end += (size_t)n;
                        nmax -= (size_t)n;
                }

                if (iocom->flags & DMSG_IOCOMF_CRYPTED) {
                        dmsg_crypto_decrypt(iocom, ioq);
                } else {
                        ioq->fifo_cdx = ioq->fifo_end;
                        ioq->fifo_cdn = ioq->fifo_end;
                }
                bytes = ioq->fifo_cdx - ioq->fifo_beg;

                /*
                 * Insufficient data accumulated (set msg NULL so caller will
                 * retry on event).
                 */
                if (bytes < ioq->hbytes) {
                        msg = NULL;
                        break;
                }

                /*
                 * Calculate the extended header, decrypt data received
                 * so far.  Handle endian-conversion for the entire extended
                 * header.
                 */
                head = (void *)(ioq->buf + ioq->fifo_beg);

                /*
                 * Check the CRC.
                 */
                if (head->magic == DMSG_HDR_MAGIC_REV)
                        xcrc32 = bswap32(head->hdr_crc);
                else
                        xcrc32 = head->hdr_crc;
                head->hdr_crc = 0;
                if (dmsg_icrc32(head, ioq->hbytes) != xcrc32) {
                        ioq->error = DMSG_IOQ_ERROR_XCRC;
                        dmio_printf(iocom, 1, "BAD-XCRC(%08x,%08x) %s\n",
                                    xcrc32, dmsg_icrc32(head, ioq->hbytes),
                                    dmsg_msg_str(msg));
                        assert(0);
                        break;
                }
                head->hdr_crc = xcrc32;

                if (head->magic == DMSG_HDR_MAGIC_REV) {
                        dmsg_bswap_head(head);
                }

                /*
                 * Copy the extended header into the msg and adjust the
                 * FIFO.
                 */
                bcopy(head, &msg->any, ioq->hbytes);

                /*
                 * We are either done or we fall-through.
                 */
                if (ioq->abytes == 0) {
                        ioq->fifo_beg += ioq->hbytes;
                        break;
                }

                /*
                 * Must adjust bytes (and the state) when falling through.
                 * nmax doesn't change.
                 */
                ioq->fifo_beg += ioq->hbytes;
                bytes -= ioq->hbytes;
                ioq->state = DMSG_MSGQ_STATE_AUXDATA1;
                /* fall through */
        case DMSG_MSGQ_STATE_AUXDATA1:
                /*
                 * Copy the partial or complete [decrypted] payload from
                 * remaining bytes in the FIFO in order to optimize the
                 * makeroom call in the AUXDATA2 state.  We have to
                 * fall-through either way so we can check the crc.
                 *
                 * msg->aux_size tracks our aux data.
                 *
                 * (Lets not complicate matters if the data is encrypted,
                 *  since the data in-stream is not the same size as the
                 *  data decrypted).
                 */
                if (bytes >= ioq->abytes) {
                        bcopy(ioq->buf + ioq->fifo_beg, msg->aux_data,
                              ioq->abytes);
                        msg->aux_size = ioq->abytes;
                        ioq->fifo_beg += ioq->abytes;
                        assert(ioq->fifo_beg <= ioq->fifo_cdx);
                        assert(ioq->fifo_cdx <= ioq->fifo_cdn);
                        bytes -= ioq->abytes;
                } else if (bytes) {
                        bcopy(ioq->buf + ioq->fifo_beg, msg->aux_data,
                              bytes);
                        msg->aux_size = bytes;
                        ioq->fifo_beg += bytes;
                        if (ioq->fifo_cdx < ioq->fifo_beg)
                                ioq->fifo_cdx = ioq->fifo_beg;
                        assert(ioq->fifo_beg <= ioq->fifo_cdx);
                        assert(ioq->fifo_cdx <= ioq->fifo_cdn);
                        bytes = 0;
                } else {
                        msg->aux_size = 0;
                }
                ioq->state = DMSG_MSGQ_STATE_AUXDATA2;
                /* fall through */
        case DMSG_MSGQ_STATE_AUXDATA2:
                /*
                 * Make sure there is enough room for more data.
                 */
                assert(msg);
                nmax = dmsg_ioq_makeroom(ioq, ioq->abytes - msg->aux_size);

                /*
                 * Read and decrypt more of the payload.
                 */
                if (msg->aux_size < ioq->abytes) {
                        assert(nmax > 0);
                        assert(bytes == 0);
                        n = read(iocom->sock_fd,
                                 ioq->buf + ioq->fifo_end,
                                 nmax);
                        if (n <= 0) {
                                if (n == 0) {
                                        ioq->error = DMSG_IOQ_ERROR_EOF;
                                        break;
                                }
                                if (errno != EINTR &&
                                    errno != EINPROGRESS &&
                                    errno != EAGAIN) {
                                        ioq->error = DMSG_IOQ_ERROR_SOCK;
                                        break;
                                }
                                n = 0;
                                /* fall through */
                        }
                        ioq->fifo_end += (size_t)n;
                        nmax -= (size_t)n;
                }

                if (iocom->flags & DMSG_IOCOMF_CRYPTED) {
                        dmsg_crypto_decrypt(iocom, ioq);
                } else {
                        ioq->fifo_cdx = ioq->fifo_end;
                        ioq->fifo_cdn = ioq->fifo_end;
                }
                bytes = ioq->fifo_cdx - ioq->fifo_beg;

                if (bytes > ioq->abytes - msg->aux_size)
                        bytes = ioq->abytes - msg->aux_size;

                if (bytes) {
                        bcopy(ioq->buf + ioq->fifo_beg,
                              msg->aux_data + msg->aux_size,
                              bytes);
                        msg->aux_size += bytes;
                        ioq->fifo_beg += bytes;
                }

                /*
                 * Insufficient data accumulated (set msg NULL so caller will
                 * retry on event).
                 *
                 * Assert the auxillary data size is correct, then record the
                 * original unaligned size from the message header.
                 */
                if (msg->aux_size < ioq->abytes) {
                        msg = NULL;
                        break;
                }
                assert(msg->aux_size == ioq->abytes);
                msg->aux_size = ioq->unaligned_aux_size;

                /*
                 * Check aux_crc, then we are done.  Note that the crc
                 * is calculated over the aligned size, not the actual
                 * size.
                 */
                xcrc32 = dmsg_icrc32(msg->aux_data, ioq->abytes);
                if (xcrc32 != msg->any.head.aux_crc) {
                        ioq->error = DMSG_IOQ_ERROR_ACRC;
                        dmio_printf(iocom, 1,
                                    "iocom: ACRC error %08x vs %08x "
                                    "msgid %016jx msgcmd %08x auxsize %d\n",
                                    xcrc32,
                                    msg->any.head.aux_crc,
                                    (intmax_t)msg->any.head.msgid,
                                    msg->any.head.cmd,
                                    msg->any.head.aux_bytes);
                        break;
                }
                break;
        case DMSG_MSGQ_STATE_ERROR:
                /*
                 * Continued calls to drain recorded transactions (returning
                 * a LNK_ERROR for each one), before we return the final
                 * LNK_ERROR.
                 */
                assert(msg == NULL);
                break;
        default:
                /*
                 * We don't double-return errors, the caller should not
                 * have called us again after getting an error msg.
                 */
                assert(0);
                break;
        }

        /*
         * Check the message sequence.  The iv[] should prevent any
         * possibility of a replay but we add this check anyway.
         */
        if (msg && ioq->error == 0) {
                if ((msg->any.head.salt & 255) != (ioq->seq & 255)) {
                        ioq->error = DMSG_IOQ_ERROR_MSGSEQ;
                } else {
                        ++ioq->seq;
                }
        }

        /*
         * Handle error, RREQ, or completion
         *
         * NOTE: nmax and bytes are invalid at this point, we don't bother
         *       to update them when breaking out.
         */
        if (ioq->error) {
skip:
                /*
                 * An unrecoverable error causes all active receive
                 * transactions to be terminated with a LNK_ERROR message.
                 *
                 * Once all active transactions are exhausted we set the
                 * iocom ERROR flag and return a non-transactional LNK_ERROR
                 * message, which should cause master processing loops to
                 * terminate.
                 */
                dmio_printf(iocom, 1, "IOQ ERROR %d\n", ioq->error);
                assert(ioq->msg == msg);
                if (msg) {
                        dmsg_msg_free(msg);
                        ioq->msg = NULL;
                        msg = NULL;
                }

                /*
                 * No more I/O read processing
                 */
                ioq->state = DMSG_MSGQ_STATE_ERROR;

                /*
                 * Simulate a remote LNK_ERROR DELETE msg for any open
                 * transactions, ending with a final non-transactional
                 * LNK_ERROR (that the session can detect) when no
                 * transactions remain.
                 *
                 * NOTE: Temporarily supply state0 and a degenerate cmd
                 *       without CREATE set.  The real state will be
                 *       assigned in the loop.
                 *
                 * NOTE: We are simulating a received message using our
                 *       side of the state, so the DMSGF_REV* bits have
                 *       to be reversed.
                 */
                pthread_mutex_lock(&iocom->mtx);
                dmsg_iocom_drain(iocom);
                dmsg_simulate_failure(&iocom->state0, 0, ioq->error);
                pthread_mutex_unlock(&iocom->mtx);
                if (TAILQ_FIRST(&ioq->msgq))
                        goto again;

#if 0
                /*
                 * For the iocom error case we want to set RWORK to indicate
                 * that more messages might be pending.
                 *
                 * It is possible to return NULL when there is more work to
                 * do because each message has to be DELETEd in both
                 * directions before we continue on with the next (though
                 * this could be optimized).  The transmit direction will
                 * re-set RWORK.
                 */
                if (msg)
                        atomic_set_int(&iocom->flags, DMSG_IOCOMF_RWORK);
#endif
        } else if (msg == NULL) {
                /*
                 * Insufficient data received to finish building the message,
                 * set RREQ and return NULL.
                 *
                 * Leave ioq->msg intact.
                 * Leave the FIFO intact.
                 */
                atomic_set_int(&iocom->flags, DMSG_IOCOMF_RREQ);
        } else {
                /*
                 * Continue processing msg.
                 *
                 * The fifo has already been advanced past the message.
                 * Trivially reset the FIFO indices if possible.
                 *
                 * clear the FIFO if it is now empty and set RREQ to wait
                 * for more from the socket.  If the FIFO is not empty set
                 * TWORK to bypass the poll so we loop immediately.
                 */
                if (ioq->fifo_beg == ioq->fifo_cdx &&
                    ioq->fifo_cdn == ioq->fifo_end) {
                        atomic_set_int(&iocom->flags, DMSG_IOCOMF_RREQ);
                        ioq->fifo_cdx = 0;
                        ioq->fifo_cdn = 0;
                        ioq->fifo_beg = 0;
                        ioq->fifo_end = 0;
                } else {
                        atomic_set_int(&iocom->flags, DMSG_IOCOMF_RWORK);
                }
                ioq->state = DMSG_MSGQ_STATE_HEADER1;
                ioq->msg = NULL;

                /*
                 * Handle message routing.  Validates non-zero sources
                 * and routes message.  Error will be 0 if the message is
                 * destined for us.
                 *
                 * State processing only occurs for messages destined for us.
                 */
                dmio_printf(iocom, 5,
                            "rxmsg cmd=%08x circ=%016jx\n",
                            msg->any.head.cmd,
                            (intmax_t)msg->any.head.circuit);

                error = dmsg_state_msgrx(msg, 0);

                if (error) {
                        /*
                         * Abort-after-closure, throw message away and
                         * start reading another.
                         */
                        if (error == DMSG_IOQ_ERROR_EALREADY) {
                                dmsg_msg_free(msg);
                                goto again;
                        }

                        /*
                         * Process real error and throw away message.
                         */
                        ioq->error = error;
                        goto skip;
                }

                /*
                 * No error and not routed
                 */
                /* no error, not routed.  Fall through and return msg */
        }
        return (msg);
}

/*
 * Calculate the header and data crc's and write a low-level message to
 * the connection.  If aux_crc is non-zero the aux_data crc is already
 * assumed to have been set.
 *
 * A non-NULL msg is added to the queue but not necessarily flushed.
 * Calling this function with msg == NULL will get a flush going.
 *
 * (called from iocom_core only)
 */
void
dmsg_iocom_flush1(dmsg_iocom_t *iocom)
{
        dmsg_ioq_t *ioq = &iocom->ioq_tx;
        dmsg_msg_t *msg;
        uint32_t xcrc32;
        size_t hbytes;
        size_t abytes;
        dmsg_msg_queue_t tmpq;

        atomic_clear_int(&iocom->flags, DMSG_IOCOMF_WREQ | DMSG_IOCOMF_WWORK);
        TAILQ_INIT(&tmpq);
        pthread_mutex_lock(&iocom->mtx);
        while ((msg = TAILQ_FIRST(&iocom->txmsgq)) != NULL) {
                TAILQ_REMOVE(&iocom->txmsgq, msg, qentry);
                TAILQ_INSERT_TAIL(&tmpq, msg, qentry);
        }
        pthread_mutex_unlock(&iocom->mtx);

        /*
         * Flush queue, doing all required encryption and CRC generation,
         * with the mutex unlocked.
         */
        while ((msg = TAILQ_FIRST(&tmpq)) != NULL) {
                /*
                 * Process terminal connection errors.
                 */
                TAILQ_REMOVE(&tmpq, msg, qentry);
                if (ioq->error) {
                        TAILQ_INSERT_TAIL(&ioq->msgq, msg, qentry);
                        ++ioq->msgcount;
                        continue;
                }

                /*
                 * Finish populating the msg fields.  The salt ensures that
                 * the iv[] array is ridiculously randomized and we also
                 * re-seed our PRNG every 32768 messages just to be sure.
                 */
                msg->any.head.magic = DMSG_HDR_MAGIC;
                msg->any.head.salt = (random() << 8) | (ioq->seq & 255);
                ++ioq->seq;
                if ((ioq->seq & 32767) == 0) {
                        pthread_mutex_lock(&iocom->mtx);
                        srandomdev();
                        pthread_mutex_unlock(&iocom->mtx);
                }

                /*
                 * Calculate aux_crc if 0, then calculate hdr_crc.
                 */
                if (msg->aux_size && msg->any.head.aux_crc == 0) {
                        abytes = DMSG_DOALIGN(msg->aux_size);
                        xcrc32 = dmsg_icrc32(msg->aux_data, abytes);
                        msg->any.head.aux_crc = xcrc32;
                }
                msg->any.head.aux_bytes = msg->aux_size;

                hbytes = (msg->any.head.cmd & DMSGF_SIZE) *
                         DMSG_ALIGN;
                msg->any.head.hdr_crc = 0;
                msg->any.head.hdr_crc = dmsg_icrc32(&msg->any.head, hbytes);

                /*
                 * Enqueue the message (the flush codes handles stream
                 * encryption).
                 */
                TAILQ_INSERT_TAIL(&ioq->msgq, msg, qentry);
                ++ioq->msgcount;
        }
        dmsg_iocom_flush2(iocom);
}

/*
 * Thread localized, iocom->mtx not held by caller.
 *
 * (called from iocom_core via iocom_flush1 only)
 */
void
dmsg_iocom_flush2(dmsg_iocom_t *iocom)
{
        dmsg_ioq_t *ioq = &iocom->ioq_tx;
        dmsg_msg_t *msg;
        ssize_t n;
        struct iovec iov[DMSG_IOQ_MAXIOVEC];
        size_t nact;
        size_t hbytes;
        size_t abytes;
        size_t hoff;
        size_t aoff;
        int iovcnt;
        int save_errno;

        if (ioq->error) {
                dmsg_iocom_drain(iocom);
                return;
        }

        /*
         * Pump messages out the connection by building an iovec.
         *
         * ioq->hbytes/ioq->abytes tracks how much of the first message
         * in the queue has been successfully written out, so we can
         * resume writing.
         */
        iovcnt = 0;
        nact = 0;
        hoff = ioq->hbytes;
        aoff = ioq->abytes;

        TAILQ_FOREACH(msg, &ioq->msgq, qentry) {
                hbytes = (msg->any.head.cmd & DMSGF_SIZE) *
                         DMSG_ALIGN;
                abytes = DMSG_DOALIGN(msg->aux_size);
                assert(hoff <= hbytes && aoff <= abytes);

                if (hoff < hbytes) {
                        size_t maxlen = hbytes - hoff;
                        if (maxlen > sizeof(ioq->buf) / 2)
                                maxlen = sizeof(ioq->buf) / 2;
                        iov[iovcnt].iov_base = (char *)&msg->any.head + hoff;
                        iov[iovcnt].iov_len = maxlen;
                        nact += maxlen;
                        ++iovcnt;
                        if (iovcnt == DMSG_IOQ_MAXIOVEC ||
                            maxlen != hbytes - hoff) {
                                break;
                        }
                }
                if (aoff < abytes) {
                        size_t maxlen = abytes - aoff;
                        if (maxlen > sizeof(ioq->buf) / 2)
                                maxlen = sizeof(ioq->buf) / 2;

                        assert(msg->aux_data != NULL);
                        iov[iovcnt].iov_base = (char *)msg->aux_data + aoff;
                        iov[iovcnt].iov_len = maxlen;
                        nact += maxlen;
                        ++iovcnt;
                        if (iovcnt == DMSG_IOQ_MAXIOVEC ||
                            maxlen != abytes - aoff) {
                                break;
                        }
                }
                hoff = 0;
                aoff = 0;
        }

        /*
         * Shortcut if no work to do.  Be sure to check for old work still
         * pending in the FIFO.
         */
        if (iovcnt == 0 && ioq->fifo_beg == ioq->fifo_cdx)
                return;

        /*
         * Encrypt and write the data.  The crypto code will move the
         * data into the fifo and adjust the iov as necessary.  If
         * encryption is disabled the iov is left alone.
         *
         * May return a smaller iov (thus a smaller n), with aggregated
         * chunks.  May reduce nmax to what fits in the FIFO.
         *
         * This function sets nact to the number of original bytes now
         * encrypted, adding to the FIFO some number of bytes that might
         * be greater depending on the crypto mechanic.  iov[] is adjusted
         * to point at the FIFO if necessary.
         *
         * NOTE: nact is the number of bytes eaten from the message.  For
         *       encrypted data this is the number of bytes processed for
         *       encryption and not necessarily the number of bytes writable.
         *       The return value from the writev() is the post-encrypted
         *       byte count which might be larger.
         *
         * NOTE: For direct writes, nact is the return value from the writev().
         */
        if (iocom->flags & DMSG_IOCOMF_CRYPTED) {
                /*
                 * Make sure the FIFO has a reasonable amount of space
                 * left (if not completely full).
                 *
                 * In this situation we are staging the encrypted message
                 * data in the FIFO.  (nact) represents how much plaintext
                 * has been staged, (n) represents how much encrypted data
                 * has been flushed.  The two are independent of each other.
                 */
                if (ioq->fifo_beg > sizeof(ioq->buf) / 2 &&
                    sizeof(ioq->buf) - ioq->fifo_end < DMSG_ALIGN * 2) {
                        bcopy(ioq->buf + ioq->fifo_beg, ioq->buf,
                              ioq->fifo_end - ioq->fifo_beg);
                        ioq->fifo_cdx -= ioq->fifo_beg;
                        ioq->fifo_cdn -= ioq->fifo_beg;
                        ioq->fifo_end -= ioq->fifo_beg;
                        ioq->fifo_beg = 0;
                }

                /* 
                 * beg .... cdx ............ cdn ............. end
                 * [WRITABLE] [PARTIALENCRYPT] [NOTYETENCRYPTED]
                 *
                 * Advance fifo_beg on a successful write.
                 */
                iovcnt = dmsg_crypto_encrypt(iocom, ioq, iov, iovcnt, &nact);
                n = writev(iocom->sock_fd, iov, iovcnt);
                save_errno = errno;
                if (n > 0) {
                        ioq->fifo_beg += n;
                        if (ioq->fifo_beg == ioq->fifo_end) {
                                ioq->fifo_beg = 0;
                                ioq->fifo_cdn = 0;
                                ioq->fifo_cdx = 0;
                                ioq->fifo_end = 0;
                        }
                }

                /*
                 * We don't mess with the nact returned by the crypto_encrypt
                 * call, which represents the filling of the FIFO.  (n) tells
                 * us how much we were able to write from the FIFO.  The two
                 * are different beasts when encrypting.
                 */
        } else {
                /*
                 * In this situation we are not staging the messages to the
                 * FIFO but instead writing them directly from the msg
                 * structure(s) unencrypted, so (nact) is basically (n).
                 */
                n = writev(iocom->sock_fd, iov, iovcnt);
                save_errno = errno;
                if (n > 0)
                        nact = n;
                else
                        nact = 0;
        }

        /*
         * Clean out the transmit queue based on what we successfully
         * encrypted (nact is the plaintext count) and is now in the FIFO.
         * ioq->hbytes/abytes represents the portion of the first message
         * previously sent.
         */
        while ((msg = TAILQ_FIRST(&ioq->msgq)) != NULL) {
                hbytes = (msg->any.head.cmd & DMSGF_SIZE) *
                         DMSG_ALIGN;
                abytes = DMSG_DOALIGN(msg->aux_size);

                if ((size_t)nact < hbytes - ioq->hbytes) {
                        ioq->hbytes += nact;
                        nact = 0;
                        break;
                }
                nact -= hbytes - ioq->hbytes;
                ioq->hbytes = hbytes;
                if ((size_t)nact < abytes - ioq->abytes) {
                        ioq->abytes += nact;
                        nact = 0;
                        break;
                }
                nact -= abytes - ioq->abytes;
                /* ioq->abytes = abytes; optimized out */

                dmio_printf(iocom, 5,
                            "txmsg cmd=%08x circ=%016jx\n",
                            msg->any.head.cmd,
                            (intmax_t)msg->any.head.circuit);

#ifdef DMSG_BLOCK_DEBUG
                uint32_t tcmd;

                if (msg->any.head.cmd & (DMSGF_CREATE | DMSGF_DELETE)) {
                        if ((msg->state->flags & DMSG_STATE_ROOT) == 0) {
                                tcmd = (msg->state->icmd & DMSGF_BASECMDMASK) |
                                            (msg->any.head.cmd & (DMSGF_CREATE |
                                                                  DMSGF_DELETE |
                                                                  DMSGF_REPLY));
                        } else {
                                tcmd = 0;
                        }
                } else {
                        tcmd = msg->any.head.cmd & DMSGF_CMDSWMASK;
                }

                switch (tcmd) {
                case DMSG_BLK_READ | DMSGF_CREATE | DMSGF_DELETE:
                case DMSG_BLK_WRITE | DMSGF_CREATE | DMSGF_DELETE:
                        dmio_printf(iocom, 4,
                                    "write BIO %-3d %016jx %d@%016jx\n",
                                    biocount, msg->any.head.msgid,
                                    msg->any.blk_read.bytes,
                                    msg->any.blk_read.offset);
                        break;
                case DMSG_BLK_READ | DMSGF_CREATE | DMSGF_DELETE | DMSGF_REPLY:
                case DMSG_BLK_WRITE | DMSGF_CREATE | DMSGF_DELETE | DMSGF_REPLY:
                        dmio_printf(iocom, 4,
                                    "wretr BIO %-3d %016jx %d@%016jx\n",
                                    biocount, msg->any.head.msgid,
                                    msg->any.blk_read.bytes,
                                    msg->any.blk_read.offset);
                        break;
                default:
                        break;
                }
#endif

                TAILQ_REMOVE(&ioq->msgq, msg, qentry);
                --ioq->msgcount;
                ioq->hbytes = 0;
                ioq->abytes = 0;
                dmsg_msg_free(msg);
        }
        assert(nact == 0);

        /*
         * Process the return value from the write w/regards to blocking.
         */
        if (n < 0) {
                if (save_errno != EINTR &&
                    save_errno != EINPROGRESS &&
                    save_errno != EAGAIN) {
                        /*
                         * Fatal write error
                         */
                        ioq->error = DMSG_IOQ_ERROR_SOCK;
                        dmsg_iocom_drain(iocom);
                } else {
                        /*
                         * Wait for socket buffer space, do not try to
                         * process more packets for transmit until space
                         * is available.
                         */
                        atomic_set_int(&iocom->flags, DMSG_IOCOMF_WREQ);
                }
        } else if (TAILQ_FIRST(&ioq->msgq) ||
                   TAILQ_FIRST(&iocom->txmsgq) ||
                   ioq->fifo_beg != ioq->fifo_cdx) {
                /*
                 * If the write succeeded and more messages are pending
                 * in either msgq, or the FIFO WWORK must remain set.
                 */
                atomic_set_int(&iocom->flags, DMSG_IOCOMF_WWORK);
        }
        /* else no transmit-side work remains */

        if (ioq->error) {
                dmsg_iocom_drain(iocom);
        }
}

/*
 * Kill pending msgs on ioq_tx and adjust the flags such that no more
 * write events will occur.  We don't kill read msgs because we want
 * the caller to pull off our contrived terminal error msg to detect
 * the connection failure.
 *
 * Localized to iocom_core thread, iocom->mtx not held by caller.
 */
void
dmsg_iocom_drain(dmsg_iocom_t *iocom)
{
        dmsg_ioq_t *ioq = &iocom->ioq_tx;
        dmsg_msg_t *msg;

        atomic_clear_int(&iocom->flags, DMSG_IOCOMF_WREQ | DMSG_IOCOMF_WWORK);
        ioq->hbytes = 0;
        ioq->abytes = 0;

        while ((msg = TAILQ_FIRST(&ioq->msgq)) != NULL) {
                TAILQ_REMOVE(&ioq->msgq, msg, qentry);
                --ioq->msgcount;
                dmsg_msg_free(msg);
        }
}

/*
 * Write a message to an iocom, with additional state processing.
 */
void
dmsg_msg_write(dmsg_msg_t *msg)
{
        dmsg_iocom_t *iocom = msg->state->iocom;
        dmsg_state_t *state;
        char dummy;

        pthread_mutex_lock(&iocom->mtx);
        state = msg->state;

        dmio_printf(iocom, 5,
                    "msgtx: cmd=%08x msgid=%016jx "
                    "state %p(%08x) error=%d\n",
                    msg->any.head.cmd, msg->any.head.msgid,
                    state, (state ? state->icmd : 0),
                    msg->any.head.error);


#if 0
        /*
         * Make sure the parent transaction is still open in the transmit
         * direction.  If it isn't the message is dead and we have to
         * potentially simulate a rxmsg terminating the transaction.
         */
        if ((state->parent->txcmd & DMSGF_DELETE) ||
            (state->parent->rxcmd & DMSGF_DELETE)) {
                dmio_printf(iocom, 4, "dmsg_msg_write: EARLY TERMINATION\n");
                dmsg_simulate_failure(state, DMSG_ERR_LOSTLINK);
                dmsg_state_cleanuptx(iocom, msg);
                dmsg_msg_free(msg);
                pthread_mutex_unlock(&iocom->mtx);
                return;
        }
#endif
        /*
         * Process state data into the message as needed, then update the
         * state based on the message.
         */
        if ((state->flags & DMSG_STATE_ROOT) == 0) {
                /*
                 * Existing transaction (could be reply).  It is also
                 * possible for this to be the first reply (CREATE is set),
                 * in which case we populate state->txcmd.
                 *
                 * state->txcmd is adjusted to hold the final message cmd,
                 * and we also be sure to set the CREATE bit here.  We did
                 * not set it in dmsg_msg_alloc() because that would have
                 * not been serialized (state could have gotten ripped out
                 * from under the message prior to it being transmitted).
                 */
                if ((msg->any.head.cmd & (DMSGF_CREATE | DMSGF_REPLY)) ==
                    DMSGF_CREATE) {
                        state->txcmd = msg->any.head.cmd & ~DMSGF_DELETE;
                        state->icmd = state->txcmd & DMSGF_BASECMDMASK;
                        state->flags &= ~DMSG_STATE_NEW;
                }
                msg->any.head.msgid = state->msgid;

                if (msg->any.head.cmd & DMSGF_CREATE) {
                        state->txcmd = msg->any.head.cmd & ~DMSGF_DELETE;
                }
        }

        /*
         * Discard messages sent to transactions which are already dead.
         */
        if (state && (state->txcmd & DMSGF_DELETE)) {
                dmio_printf(iocom, 4,
                            "dmsg_msg_write: drop msg %08x to dead "
                            "circuit state=%p\n",
                            msg->any.head.cmd, state);
                dmsg_msg_free(msg);
                return;
        }

        /*
         * Normally we queue the msg for output.  However, if the circuit is
         * dead or dying we must simulate a failure in the return direction
         * and throw the message away.  The other end is not expecting any
         * further messages from us on this state.
         *
         * Note that the I/O thread is responsible for generating the CRCs
         * and encryption.
         */
        if (state->flags & DMSG_STATE_DYING) {
#if 0
        if ((state->parent->txcmd & DMSGF_DELETE) ||
            (state->parent->flags & DMSG_STATE_DYING) ||
            (state->flags & DMSG_STATE_DYING)) {
#endif
                /* 
                 * Illegal message, kill state and related sub-state.
                 * Cannot transmit if state is already dying.
                 */
                dmio_printf(iocom, 4,
                            "dmsg_msg_write: Write to dying circuit "
                            "ptxcmd=%08x prxcmd=%08x flags=%08x\n",
                            state->parent->rxcmd,
                            state->parent->txcmd,
                            state->parent->flags);
                dmsg_state_hold(state);
                dmsg_state_cleanuptx(iocom, msg);
                if ((state->flags & DMSG_STATE_ABORTING) == 0) {
                        dmsg_simulate_failure(state, 1, DMSG_ERR_LOSTLINK);
                }
                dmsg_state_drop(state);
                dmsg_msg_free(msg);
        } else {
                /*
                 * Queue the message, clean up transmit state prior to queueing
                 * to avoid SMP races.
                 */
                dmio_printf(iocom, 5,
                            "dmsg_msg_write: commit msg state=%p to txkmsgq\n",
                            state);
                dmsg_state_cleanuptx(iocom, msg);
                TAILQ_INSERT_TAIL(&iocom->txmsgq, msg, qentry);
                dummy = 0;
                write(iocom->wakeupfds[1], &dummy, 1);  /* XXX optimize me */
        }
        pthread_mutex_unlock(&iocom->mtx);
}

/*
 * Remove state from its parent's subq.  This can wind up recursively
 * dropping the parent upward.
 *
 * NOTE: iocom must be locked.
 *
 * NOTE: Once we drop the parent, our pstate pointer may become invalid.
 */
static
void
dmsg_subq_delete(dmsg_state_t *state)
{
        dmsg_state_t *pstate;

        if (state->flags & DMSG_STATE_SUBINSERTED) {
                pstate = state->parent;
                assert(pstate);
                if (pstate->scan == state)
                        pstate->scan = NULL;
                TAILQ_REMOVE(&pstate->subq, state, entry);
                state->flags &= ~DMSG_STATE_SUBINSERTED;
                state->parent = NULL;
                if (TAILQ_EMPTY(&pstate->subq))
                        dmsg_state_drop(pstate);/* pstate->subq */
                pstate = NULL;                  /* safety */
                dmsg_state_drop(state);         /* pstate->subq */
        } else {
                assert(state->parent == NULL);
        }
}

/*
 * Simulate reception of a transaction DELETE message when the link goes
 * bad.  This routine must recurse through state->subq and generate messages
 * and callbacks bottom-up.
 *
 * iocom->mtx must be held by caller.
 */
static
void
dmsg_simulate_failure(dmsg_state_t *state, int meto, int error)
{
        dmsg_state_t *substate;

        dmsg_state_hold(state);
        if (meto)
                dmsg_state_abort(state);

        /*
         * Recurse through sub-states.
         */
again:
        TAILQ_FOREACH(substate, &state->subq, entry) {
                if (substate->flags & DMSG_STATE_ABORTING)
                        continue;
                state->scan = substate;
                dmsg_simulate_failure(substate, 1, error);
                if (state->scan != substate)
                        goto again;
        }

        dmsg_state_drop(state);
}

static
void
dmsg_state_abort(dmsg_state_t *state)
{
        dmsg_iocom_t *iocom;
        dmsg_msg_t *msg;

        /*
         * Set ABORTING and DYING, return if already set.  If the state was
         * just allocated we defer the abort operation until the related
         * message is processed.
         */
        if (state->flags & DMSG_STATE_ABORTING)
                return;
        state->flags |= DMSG_STATE_ABORTING;
        dmsg_state_dying(state);
        if (state->flags & DMSG_STATE_NEW) {
                dmio_printf(iocom, 4,
                            "dmsg_state_abort(0): state %p rxcmd %08x "
                            "txcmd %08x flags %08x - in NEW state\n",
                            state, state->rxcmd,
                            state->txcmd, state->flags);
                return;
        }

        /*
         * Simulate parent state failure before child states.  Device
         * drivers need to understand this and flag the situation but might
         * have asynchronous operations in progress that they cannot stop.
         * To make things easier, parent states will not actually disappear
         * until the children are all gone.
         */
        if ((state->rxcmd & DMSGF_DELETE) == 0) {
                dmio_printf(iocom, 5,
                            "dmsg_state_abort() on state %p\n",
                            state);
                msg = dmsg_msg_alloc_locked(state, 0, DMSG_LNK_ERROR,
                                            NULL, NULL);
                if ((state->rxcmd & DMSGF_CREATE) == 0)
                        msg->any.head.cmd |= DMSGF_CREATE;
                msg->any.head.cmd |= DMSGF_DELETE |
                                     (state->rxcmd & DMSGF_REPLY);
                msg->any.head.cmd ^= (DMSGF_REVTRANS | DMSGF_REVCIRC);
                msg->any.head.error = DMSG_ERR_LOSTLINK;
                msg->any.head.cmd |= DMSGF_ABORT;

                /*
                 * Issue callback synchronously even though this isn't
                 * the receiver thread.  We need to issue the callback
                 * before removing state from the subq in order to allow
                 * the callback to reply.
                 */
                iocom = state->iocom;
                dmsg_state_msgrx(msg, 1);
                pthread_mutex_unlock(&iocom->mtx);
                iocom->rcvmsg_callback(msg);
                pthread_mutex_lock(&iocom->mtx);
                dmsg_state_cleanuprx(iocom, msg);
#if 0
                TAILQ_INSERT_TAIL(&iocom->ioq_rx.msgq, msg, qentry);
                atomic_set_int(&iocom->flags, DMSG_IOCOMF_RWORK);
#endif
        }
}


/*
 * Recursively sets DMSG_STATE_DYING on state and all sub-states, preventing
 * the transmission of any new messages on these states.  This is done
 * atomically when parent state is terminating, whereas setting ABORTING is
 * not atomic and can leak races.
 */
static
void
dmsg_state_dying(dmsg_state_t *state)
{
        dmsg_state_t *scan;

        if ((state->flags & DMSG_STATE_DYING) == 0) {
                state->flags |= DMSG_STATE_DYING;
                TAILQ_FOREACH(scan, &state->subq, entry)
                        dmsg_state_dying(scan);
        }
}

/*
 * This is a shortcut to formulate a reply to msg with a simple error code,
 * It can reply to and terminate a transaction, or it can reply to a one-way
 * messages.  A DMSG_LNK_ERROR command code is utilized to encode
 * the error code (which can be 0).  Not all transactions are terminated
 * with DMSG_LNK_ERROR status (the low level only cares about the
 * MSGF_DELETE flag), but most are.
 *
 * Replies to one-way messages are a bit of an oxymoron but the feature
 * is used by the debug (DBG) protocol.
 *
 * The reply contains no extended data.
 */
void
dmsg_msg_reply(dmsg_msg_t *msg, uint32_t error)
{
        dmsg_state_t *state = msg->state;
        dmsg_msg_t *nmsg;
        uint32_t cmd;

        /*
         * Reply with a simple error code and terminate the transaction.
         */
        cmd = DMSG_LNK_ERROR;

        /*
         * Check if our direction has even been initiated yet, set CREATE.
         *
         * Check what direction this is (command or reply direction).  Note
         * that txcmd might not have been initiated yet.
         *
         * If our direction has already been closed we just return without
         * doing anything.
         */
        if ((state->flags & DMSG_STATE_ROOT) == 0) {
                if (state->txcmd & DMSGF_DELETE)
                        return;
                if (state->txcmd & DMSGF_REPLY)
                        cmd |= DMSGF_REPLY;
                cmd |= DMSGF_DELETE;
        } else {
                if ((msg->any.head.cmd & DMSGF_REPLY) == 0)
                        cmd |= DMSGF_REPLY;
        }

        /*
         * Allocate the message and associate it with the existing state.
         * We cannot pass DMSGF_CREATE to msg_alloc() because that may
         * allocate new state.  We have our state already.
         */
        nmsg = dmsg_msg_alloc(state, 0, cmd, NULL, NULL);
        if ((state->flags & DMSG_STATE_ROOT) == 0) {
                if ((state->txcmd & DMSGF_CREATE) == 0)
                        nmsg->any.head.cmd |= DMSGF_CREATE;
        }
        nmsg->any.head.error = error;

        dmsg_msg_write(nmsg);
}

/*
 * Similar to dmsg_msg_reply() but leave the transaction open.  That is,
 * we are generating a streaming reply or an intermediate acknowledgement
 * of some sort as part of the higher level protocol, with more to come
 * later.
 */
void
dmsg_msg_result(dmsg_msg_t *msg, uint32_t error)
{
        dmsg_state_t *state = msg->state;
        dmsg_msg_t *nmsg;
        uint32_t cmd;


        /*
         * Reply with a simple error code and terminate the transaction.
         */
        cmd = DMSG_LNK_ERROR;

        /*
         * Check if our direction has even been initiated yet, set CREATE.
         *
         * Check what direction this is (command or reply direction).  Note
         * that txcmd might not have been initiated yet.
         *
         * If our direction has already been closed we just return without
         * doing anything.
         */
        if ((state->flags & DMSG_STATE_ROOT) == 0) {
                if (state->txcmd & DMSGF_DELETE)
                        return;
                if (state->txcmd & DMSGF_REPLY)
                        cmd |= DMSGF_REPLY;
                /* continuing transaction, do not set MSGF_DELETE */
        } else {
                if ((msg->any.head.cmd & DMSGF_REPLY) == 0)
                        cmd |= DMSGF_REPLY;
        }
        nmsg = dmsg_msg_alloc(state, 0, cmd, NULL, NULL);
        if ((state->flags & DMSG_STATE_ROOT) == 0) {
                if ((state->txcmd & DMSGF_CREATE) == 0)
                        nmsg->any.head.cmd |= DMSGF_CREATE;
        }
        nmsg->any.head.error = error;

        dmsg_msg_write(nmsg);
}

/*
 * Terminate a transaction given a state structure by issuing a DELETE.
 * (the state structure must not be &iocom->state0)
 */
void
dmsg_state_reply(dmsg_state_t *state, uint32_t error)
{
        dmsg_msg_t *nmsg;
        uint32_t cmd = DMSG_LNK_ERROR | DMSGF_DELETE;

        /*
         * Nothing to do if we already transmitted a delete
         */
        if (state->txcmd & DMSGF_DELETE)
                return;

        /*
         * Set REPLY if the other end initiated the command.  Otherwise
         * we are the command direction.
         */
        if (state->txcmd & DMSGF_REPLY)
                cmd |= DMSGF_REPLY;

        nmsg = dmsg_msg_alloc(state, 0, cmd, NULL, NULL);
        if ((state->flags & DMSG_STATE_ROOT) == 0) {
                if ((state->txcmd & DMSGF_CREATE) == 0)
                        nmsg->any.head.cmd |= DMSGF_CREATE;
        }
        nmsg->any.head.error = error;
        dmsg_msg_write(nmsg);
}

/*
 * Terminate a transaction given a state structure by issuing a DELETE.
 * (the state structure must not be &iocom->state0)
 */
void
dmsg_state_result(dmsg_state_t *state, uint32_t error)
{
        dmsg_msg_t *nmsg;
        uint32_t cmd = DMSG_LNK_ERROR;

        /*
         * Nothing to do if we already transmitted a delete
         */
        if (state->txcmd & DMSGF_DELETE)
                return;

        /*
         * Set REPLY if the other end initiated the command.  Otherwise
         * we are the command direction.
         */
        if (state->txcmd & DMSGF_REPLY)
                cmd |= DMSGF_REPLY;

        nmsg = dmsg_msg_alloc(state, 0, cmd, NULL, NULL);
        if ((state->flags & DMSG_STATE_ROOT) == 0) {
                if ((state->txcmd & DMSGF_CREATE) == 0)
                        nmsg->any.head.cmd |= DMSGF_CREATE;
        }
        nmsg->any.head.error = error;
        dmsg_msg_write(nmsg);
}

/************************************************************************
 *                      TRANSACTION STATE HANDLING                      *
 ************************************************************************
 *
 */

/*
 * Process state tracking for a message after reception, prior to execution.
 * Possibly route the message (consuming it).
 *
 * Called with msglk held and the msg dequeued.
 *
 * All messages are called with dummy state and return actual state.
 * (One-off messages often just return the same dummy state).
 *
 * May request that caller discard the message by setting *discardp to 1.
 * The returned state is not used in this case and is allowed to be NULL.
 *
 * --
 *
 * These routines handle persistent and command/reply message state via the
 * CREATE and DELETE flags.  The first message in a command or reply sequence
 * sets CREATE, the last message in a command or reply sequence sets DELETE.
 *
 * There can be any number of intermediate messages belonging to the same
 * sequence sent inbetween the CREATE message and the DELETE message,
 * which set neither flag.  This represents a streaming command or reply.
 *
 * Any command message received with CREATE set expects a reply sequence to
 * be returned.  Reply sequences work the same as command sequences except the
 * REPLY bit is also sent.  Both the command side and reply side can
 * degenerate into a single message with both CREATE and DELETE set.  Note
 * that one side can be streaming and the other side not, or neither, or both.
 *
 * The msgid is unique for the initiator.  That is, two sides sending a new
 * message can use the same msgid without colliding.
 *
 * --
 *
 * The message may be running over a circuit.  If the circuit is half-deleted
 * The message is typically racing against a link failure and must be thrown
 * out.  As the circuit deletion propagates the library will automatically
 * generate terminations for sub states.
 *
 * --
 *
 * ABORT sequences work by setting the ABORT flag along with normal message
 * state.  However, ABORTs can also be sent on half-closed messages, that is
 * even if the command or reply side has already sent a DELETE, as long as
 * the message has not been fully closed it can still send an ABORT+DELETE
 * to terminate the half-closed message state.
 *
 * Since ABORT+DELETEs can race we silently discard ABORT's for message
 * state which has already been fully closed.  REPLY+ABORT+DELETEs can
 * also race, and in this situation the other side might have already
 * initiated a new unrelated command with the same message id.  Since
 * the abort has not set the CREATE flag the situation can be detected
 * and the message will also be discarded.
 *
 * Non-blocking requests can be initiated with ABORT+CREATE[+DELETE].
 * The ABORT request is essentially integrated into the command instead
 * of being sent later on.  In this situation the command implementation
 * detects that CREATE and ABORT are both set (vs ABORT alone) and can
 * special-case non-blocking operation for the command.
 *
 * NOTE!  Messages with ABORT set without CREATE or DELETE are considered
 *        to be mid-stream aborts for command/reply sequences.  ABORTs on
 *        one-way messages are not supported.
 *
 * NOTE!  If a command sequence does not support aborts the ABORT flag is
 *        simply ignored.
 *
 * --
 *
 * One-off messages (no reply expected) are sent without an established
 * transaction.  CREATE and DELETE are left clear and the msgid is usually 0.
 * For one-off messages sent over circuits msgid generally MUST be 0.
 *
 * One-off messages cannot be aborted and typically aren't processed
 * by these routines.  Order is still guaranteed for messages sent over
 * the same circuit.  The REPLY bit can be used to distinguish whether
 * a one-off message is a command or reply.  For example, one-off replies
 * will typically just contain status updates.
 */
static int
dmsg_state_msgrx(dmsg_msg_t *msg, int mstate)
{
        dmsg_iocom_t *iocom = msg->state->iocom;
        dmsg_state_t *state;
        dmsg_state_t *pstate;
        dmsg_state_t sdummy;
        int error;

        pthread_mutex_lock(&iocom->mtx);

        if (DMsgDebugOpt) {
                dmio_printf(iocom, 5,
                            "msgrx: cmd=%08x msgid=%016jx "
                            "circuit=%016jx error=%d\n",
                            msg->any.head.cmd,
                            msg->any.head.msgid,
                            msg->any.head.circuit,
                            msg->any.head.error);
        }

        /*
         * Lookup the circuit (pstate).  The circuit will be an open
         * transaction.  The REVCIRC bit in the message tells us which side
         * initiated it.
         *
         * If mstate is non-zero the state has already been incorporated
         * into the message as part of a simulated abort.  Note that in this
         * situation the parent state may have already been removed from
         * the RBTREE.
         */
        if (mstate) {
                pstate = msg->state->parent;
        } else if (msg->any.head.circuit) {
                sdummy.msgid = msg->any.head.circuit;

                if (msg->any.head.cmd & DMSGF_REVCIRC) {
                        pstate = RB_FIND(dmsg_state_tree,
                                         &iocom->statewr_tree,
                                         &sdummy);
                } else {
                        pstate = RB_FIND(dmsg_state_tree,
                                         &iocom->staterd_tree,
                                         &sdummy);
                }

                /*
                 * If we cannot find the circuit throw the message away.
                 * The state will have already been taken care of by
                 * the simulated failure code.  This case can occur due
                 * to a failure propagating in one direction crossing a
                 * request on the failed circuit propagating in the other
                 * direction.
                 */
                if (pstate == NULL) {
                        dmio_printf(iocom, 4,
                                    "missing parent in stacked trans %s\n",
                                    dmsg_msg_str(msg));
                        pthread_mutex_unlock(&iocom->mtx);
                        error = DMSG_IOQ_ERROR_EALREADY;

                        return error;
                }
        } else {
                pstate = &iocom->state0;
        }
        /* WARNING: pstate not (yet) refd */

        /*
         * Lookup the msgid.
         *
         * If mstate is non-zero the state has already been incorporated
         * into the message as part of a simulated abort.  Note that in this
         * situation the state may have already been removed from the RBTREE.
         *
         * If received msg is a command state is on staterd_tree.
         * If received msg is a reply state is on statewr_tree.
         * Otherwise there is no state (retain &iocom->state0)
         */
        if (mstate) {
                state = msg->state;
        } else {
                sdummy.msgid = msg->any.head.msgid;
                if (msg->any.head.cmd & DMSGF_REVTRANS) {
                        state = RB_FIND(dmsg_state_tree,
                                        &iocom->statewr_tree, &sdummy);
                } else {
                        state = RB_FIND(dmsg_state_tree,
                                        &iocom->staterd_tree, &sdummy);
                }
        }

        if (DMsgDebugOpt) {
                dmio_printf(iocom, 5, "msgrx:\tstate %p(%08x)",
                            state, (state ? state->icmd : 0));
                if (pstate != &iocom->state0) {
                        dmio_printf(iocom, 5,
                                    " pstate %p(%08x)",
                                    pstate, pstate->icmd);
                }
                dmio_printf(iocom, 5, "%s\n", "");
        }

        if (mstate) {
                /* state already assigned to msg */
        } else if (state) {
                /*
                 * Message over an existing transaction (CREATE should not
                 * be set).
                 */
                dmsg_state_drop(msg->state);
                dmsg_state_hold(state);
                msg->state = state;
                assert(pstate == state->parent);
        } else {
                /*
                 * Either a new transaction (if CREATE set) or a one-off.
                 */
                state = pstate;
        }

        /*
         * Switch on CREATE, DELETE, REPLY, and also handle ABORT from
         * inside the case statements.
         *
         * Construct new state as necessary.
         */
        switch(msg->any.head.cmd & (DMSGF_CREATE | DMSGF_DELETE |
                                    DMSGF_REPLY)) {
        case DMSGF_CREATE:
        case DMSGF_CREATE | DMSGF_DELETE:
                /*
                 * Create new sub-transaction under pstate.
                 * (any DELETE is handled in post-processing of msg).
                 *
                 * (During routing the msgid was made unique for this
                 * direction over the comlink, so our RB trees can be
                 * iocom-based instead of state-based).
                 */
                if (state != pstate) {
                        dmio_printf(iocom, 2,
                                    "duplicate transaction %s\n",
                                    dmsg_msg_str(msg));
                        error = DMSG_IOQ_ERROR_TRANS;
                        assert(0);
                        break;
                }

                /*
                 * Allocate the new state.
                 */
                state = malloc(sizeof(*state));
                bzero(state, sizeof(*state));
                atomic_add_int(&dmsg_state_count, 1);

                TAILQ_INIT(&state->subq);
                dmsg_state_hold(pstate);
                state->parent = pstate;
                state->iocom = iocom;
                state->flags = DMSG_STATE_DYNAMIC |
                               DMSG_STATE_OPPOSITE;
                state->msgid = msg->any.head.msgid;
                state->txcmd = DMSGF_REPLY;
                state->rxcmd = msg->any.head.cmd & ~DMSGF_DELETE;
                state->icmd = state->rxcmd & DMSGF_BASECMDMASK;
                state->flags &= ~DMSG_STATE_NEW;
                msg->state = state;

                RB_INSERT(dmsg_state_tree, &iocom->staterd_tree, state);
                if (TAILQ_EMPTY(&pstate->subq))
                        dmsg_state_hold(pstate);/* pstate->subq */
                TAILQ_INSERT_TAIL(&pstate->subq, state, entry);
                state->flags |= DMSG_STATE_SUBINSERTED |
                                DMSG_STATE_RBINSERTED;
                dmsg_state_hold(state);         /* pstate->subq */
                dmsg_state_hold(state);         /* state on rbtree */
                dmsg_state_hold(state);         /* msg->state */

                /*
                 * If the parent is a relay set up the state handler to
                 * automatically route the message.  Local processing will
                 * not occur if set.
                 *
                 * (state relays are seeded by SPAN processing)
                 */
                if (pstate->relay)
                        state->func = dmsg_state_relay;
                error = 0;
                break;
        case DMSGF_DELETE:
                /*
                 * Persistent state is expected but might not exist if an
                 * ABORT+DELETE races the close.
                 *
                 * (any DELETE is handled in post-processing of msg).
                 */
                if (state == pstate) {
                        if (msg->any.head.cmd & DMSGF_ABORT) {
                                error = DMSG_IOQ_ERROR_EALREADY;
                        } else {
                                dmio_printf(iocom, 2,
                                            "missing-state %s\n",
                                            dmsg_msg_str(msg));
                                error = DMSG_IOQ_ERROR_TRANS;
                                assert(0);
                        }
                        break;
                }

                /*
                 * Handle another ABORT+DELETE case if the msgid has already
                 * been reused.
                 */
                if ((state->rxcmd & DMSGF_CREATE) == 0) {
                        if (msg->any.head.cmd & DMSGF_ABORT) {
                                error = DMSG_IOQ_ERROR_EALREADY;
                        } else {
                                dmio_printf(iocom, 2,
                                            "reused-state %s\n",
                                            dmsg_msg_str(msg));
                                error = DMSG_IOQ_ERROR_TRANS;
                                assert(0);
                        }
                        break;
                }
                error = 0;
                break;
        default:
                /*
                 * Check for mid-stream ABORT command received, otherwise
                 * allow.
                 */
                if (msg->any.head.cmd & DMSGF_ABORT) {
                        if ((state == pstate) ||
                            (state->rxcmd & DMSGF_CREATE) == 0) {
                                error = DMSG_IOQ_ERROR_EALREADY;
                                break;
                        }
                }
                error = 0;
                break;
        case DMSGF_REPLY | DMSGF_CREATE:
        case DMSGF_REPLY | DMSGF_CREATE | DMSGF_DELETE:
                /*
                 * When receiving a reply with CREATE set the original
                 * persistent state message should already exist.
                 */
                if (state == pstate) {
                        dmio_printf(iocom, 2, "no-state(r) %s\n",
                                    dmsg_msg_str(msg));
                        error = DMSG_IOQ_ERROR_TRANS;
                        assert(0);
                        break;
                }
                assert(((state->rxcmd ^ msg->any.head.cmd) & DMSGF_REPLY) == 0);
                state->rxcmd = msg->any.head.cmd & ~DMSGF_DELETE;
                error = 0;
                break;
        case DMSGF_REPLY | DMSGF_DELETE:
                /*
                 * Received REPLY+ABORT+DELETE in case where msgid has
                 * already been fully closed, ignore the message.
                 */
                if (state == pstate) {
                        if (msg->any.head.cmd & DMSGF_ABORT) {
                                error = DMSG_IOQ_ERROR_EALREADY;
                        } else {
                                dmio_printf(iocom, 2,
                                            "no-state(r,d) %s\n",
                                            dmsg_msg_str(msg));
                                error = DMSG_IOQ_ERROR_TRANS;
                                assert(0);
                        }
                        break;
                }

                /*
                 * Received REPLY+ABORT+DELETE in case where msgid has
                 * already been reused for an unrelated message,
                 * ignore the message.
                 */
                if ((state->rxcmd & DMSGF_CREATE) == 0) {
                        if (msg->any.head.cmd & DMSGF_ABORT) {
                                error = DMSG_IOQ_ERROR_EALREADY;
                        } else {
                                dmio_printf(iocom, 2,
                                            "reused-state(r,d) %s\n",
                                            dmsg_msg_str(msg));
                                error = DMSG_IOQ_ERROR_TRANS;
                                assert(0);
                        }
                        break;
                }
                error = 0;
                break;
        case DMSGF_REPLY:
                /*
                 * Check for mid-stream ABORT reply received to sent command.
                 */
                if (msg->any.head.cmd & DMSGF_ABORT) {
                        if (state == pstate ||
                            (state->rxcmd & DMSGF_CREATE) == 0) {
                                error = DMSG_IOQ_ERROR_EALREADY;
                                break;
                        }
                }
                error = 0;
                break;
        }

        /*
         * Calculate the easy-switch() transactional command.  Represents
         * the outer-transaction command for any transaction-create or
         * transaction-delete, and the inner message command for any
         * non-transaction or inside-transaction command.  tcmd will be
         * set to 0 for any messaging error condition.
         *
         * The two can be told apart because outer-transaction commands
         * always have a DMSGF_CREATE and/or DMSGF_DELETE flag.
         */
        if (msg->any.head.cmd & (DMSGF_CREATE | DMSGF_DELETE)) {
                if ((msg->state->flags & DMSG_STATE_ROOT) == 0) {
                        msg->tcmd = (state->icmd & DMSGF_BASECMDMASK) |
                                    (msg->any.head.cmd & (DMSGF_CREATE |
                                                          DMSGF_DELETE |
                                                          DMSGF_REPLY));
                } else {
                        msg->tcmd = 0;
                }
        } else {
                msg->tcmd = msg->any.head.cmd & DMSGF_CMDSWMASK;
        }

#ifdef DMSG_BLOCK_DEBUG
        switch (msg->tcmd) {
        case DMSG_BLK_READ | DMSGF_CREATE | DMSGF_DELETE:
        case DMSG_BLK_WRITE | DMSGF_CREATE | DMSGF_DELETE:
                dmio_printf(iocom, 4,
                            "read  BIO %-3d %016jx %d@%016jx\n",
                            biocount, msg->any.head.msgid,
                            msg->any.blk_read.bytes,
                            msg->any.blk_read.offset);
                break;
        case DMSG_BLK_READ | DMSGF_CREATE | DMSGF_DELETE | DMSGF_REPLY:
        case DMSG_BLK_WRITE | DMSGF_CREATE | DMSGF_DELETE | DMSGF_REPLY:
                dmio_printf(iocom, 4,
                            "rread BIO %-3d %016jx %d@%016jx\n",
                            biocount, msg->any.head.msgid,
                            msg->any.blk_read.bytes,
                            msg->any.blk_read.offset);
                break;
        default:
                break;
        }
#endif

        /*
         * Adjust state, mark receive side as DELETED if appropriate and
         * adjust RB tree if both sides are DELETED.  cleanuprx handles
         * the rest after the state callback returns.
         */
        assert(msg->state->iocom == iocom);
        assert(msg->state == state);

        if (state->flags & DMSG_STATE_ROOT) {
                /*
                 * Nothing to do for non-transactional messages.
                 */
        } else if (msg->any.head.cmd & DMSGF_DELETE) {
                /*
                 * Message terminating transaction, remove the state from
                 * the RB tree if the full transaction is now complete.
                 * The related state, subq, and parent link is retained
                 * until after the state callback is complete.
                 */
                assert((state->rxcmd & DMSGF_DELETE) == 0);
                state->rxcmd |= DMSGF_DELETE;
                if (state->txcmd & DMSGF_DELETE) {
                        assert(state->flags & DMSG_STATE_RBINSERTED);
                        if (state->rxcmd & DMSGF_REPLY) {
                                assert(msg->any.head.cmd & DMSGF_REPLY);
                                RB_REMOVE(dmsg_state_tree,
                                          &iocom->statewr_tree, state);
                        } else {
                                assert((msg->any.head.cmd & DMSGF_REPLY) == 0);
                                RB_REMOVE(dmsg_state_tree,
                                          &iocom->staterd_tree, state);
                        }
                        state->flags &= ~DMSG_STATE_RBINSERTED;
                        dmsg_state_drop(state);
                }
        }

        pthread_mutex_unlock(&iocom->mtx);

        if (DMsgDebugOpt && error)
                dmio_printf(iocom, 1, "msgrx: error %d\n", error);

        return (error);
}

/*
 * Route the message and handle pair-state processing.
 */
void
dmsg_state_relay(dmsg_msg_t *lmsg)
{
        dmsg_state_t *lpstate;
        dmsg_state_t *rpstate;
        dmsg_state_t *lstate;
        dmsg_state_t *rstate;
        dmsg_msg_t *rmsg;

#ifdef DMSG_BLOCK_DEBUG
        switch (lmsg->tcmd) {
        case DMSG_BLK_OPEN | DMSGF_CREATE:
                dmio_printf(iocom, 4, "%s\n",
                            "relay BIO_OPEN (CREATE)");
                break;
        case DMSG_BLK_OPEN | DMSGF_DELETE:
                dmio_printf(iocom, 4, "%s\n",
                            "relay BIO_OPEN (DELETE)");
                break;
        case DMSG_BLK_READ | DMSGF_CREATE | DMSGF_DELETE:
        case DMSG_BLK_WRITE | DMSGF_CREATE | DMSGF_DELETE:
                atomic_add_int(&biocount, 1);
                dmio_printf(iocom, 4,
                            "relay BIO %-3d %016jx %d@%016jx\n",
                            biocount, lmsg->any.head.msgid,
                            lmsg->any.blk_read.bytes,
                            lmsg->any.blk_read.offset);
                break;
        case DMSG_BLK_READ | DMSGF_CREATE | DMSGF_DELETE | DMSGF_REPLY:
        case DMSG_BLK_WRITE | DMSGF_CREATE | DMSGF_DELETE | DMSGF_REPLY:
                dmio_printf(iocom, 4,
                            "retrn BIO %-3d %016jx %d@%016jx\n",
                            biocount, lmsg->any.head.msgid,
                            lmsg->any.blk_read.bytes,
                            lmsg->any.blk_read.offset);
                atomic_add_int(&biocount, -1);
                break;
        default:
                break;
        }
#endif

        if ((lmsg->any.head.cmd & (DMSGF_CREATE | DMSGF_REPLY)) ==
            DMSGF_CREATE) {
                /*
                 * New sub-transaction, establish new state and relay.
                 */
                lstate = lmsg->state;
                lpstate = lstate->parent;
                rpstate = lpstate->relay;
                assert(lstate->relay == NULL);
                assert(rpstate != NULL);

                rmsg = dmsg_msg_alloc(rpstate, 0,
                                      lmsg->any.head.cmd,
                                      dmsg_state_relay, NULL);
                rstate = rmsg->state;
                rstate->relay = lstate;
                lstate->relay = rstate;
                dmsg_state_hold(lstate);
                dmsg_state_hold(rstate);
        } else {
                /*
                 * State & relay already established
                 */
                lstate = lmsg->state;
                rstate = lstate->relay;
                assert(rstate != NULL);

                assert((rstate->txcmd & DMSGF_DELETE) == 0);

#if 0
                if (lstate->flags & DMSG_STATE_ABORTING) {
                        dmio_printf(iocom, 4,
                                    "relay: relay lost link l=%p r=%p\n",
                                    lstate, rstate);
                        dmsg_simulate_failure(rstate, 0, DMSG_ERR_LOSTLINK);
                }
#endif

                rmsg = dmsg_msg_alloc(rstate, 0,
                                      lmsg->any.head.cmd,
                                      dmsg_state_relay, NULL);
        }
        if (lmsg->hdr_size > sizeof(lmsg->any.head)) {
                bcopy(&lmsg->any.head + 1, &rmsg->any.head + 1,
                      lmsg->hdr_size - sizeof(lmsg->any.head));
        }
        rmsg->any.head.error = lmsg->any.head.error;
        rmsg->any.head.reserved02 = lmsg->any.head.reserved02;
        rmsg->any.head.link_verifier = lmsg->any.head.link_verifier;
        rmsg->aux_size = lmsg->aux_size;
        rmsg->aux_data = lmsg->aux_data;
        lmsg->aux_data = NULL;

        dmsg_msg_write(rmsg);
}

/*
 * Cleanup and retire msg after issuing the state callback.  The state
 * has already been removed from the RB tree.  The subq and msg must be
 * cleaned up.
 *
 * Called with the iocom mutex held (to handle subq disconnection).
 */
void
dmsg_state_cleanuprx(dmsg_iocom_t *iocom, dmsg_msg_t *msg)
{
        dmsg_state_t *state;

        assert(msg->state->iocom == iocom);
        state = msg->state;
        if (state->flags & DMSG_STATE_ROOT) {
                /*
                 * Free a non-transactional message, there is no state
                 * to worry about.
                 */
                dmsg_msg_free(msg);
        } else if ((state->flags & DMSG_STATE_SUBINSERTED) &&
                   (state->rxcmd & DMSGF_DELETE) &&
                   (state->txcmd & DMSGF_DELETE)) {
                /*
                 * Must disconnect from parent and drop relay.
                 */
                dmsg_subq_delete(state);
                if (state->relay) {
                        dmsg_state_drop(state->relay);
                        state->relay = NULL;
                }
                dmsg_msg_free(msg);
        } else {
                /*
                 * Message not terminating transaction, leave state intact
                 * and free message if it isn't the CREATE message.
                 */
                dmsg_msg_free(msg);
        }
}

/*
 * Clean up the state after pulling out needed fields and queueing the
 * message for transmission.   This occurs in dmsg_msg_write().
 *
 * Called with the mutex locked.
 */
static void
dmsg_state_cleanuptx(dmsg_iocom_t *iocom, dmsg_msg_t *msg)
{
        dmsg_state_t *state;

        assert(iocom == msg->state->iocom);
        state = msg->state;

        dmsg_state_hold(state);

        if (state->flags & DMSG_STATE_ROOT) {
                ;
        } else if (msg->any.head.cmd & DMSGF_DELETE) {
                /*
                 * Message terminating transaction, destroy the related
                 * state, the original message, and this message (if it
                 * isn't the original message due to a CREATE|DELETE).
                 *
                 * It's possible for governing state to terminate while
                 * sub-transactions still exist.  This is allowed but
                 * will cause sub-transactions to recursively fail.
                 * Further reception of sub-transaction messages will be
                 * impossible because the circuit will no longer exist.
                 * (XXX need code to make sure that happens properly).
                 *
                 * NOTE: It is possible for a fafilure to terminate the
                 *       state after we have written the message but before
                 *       we are able to call cleanuptx, so txcmd might already
                 *       have DMSGF_DELETE set.
                 */
                if ((state->txcmd & DMSGF_DELETE) == 0 &&
                    (state->rxcmd & DMSGF_DELETE)) {
                        state->txcmd |= DMSGF_DELETE;
                        assert(state->flags & DMSG_STATE_RBINSERTED);
                        if (state->txcmd & DMSGF_REPLY) {
                                assert(msg->any.head.cmd & DMSGF_REPLY);
                                RB_REMOVE(dmsg_state_tree,
                                          &iocom->staterd_tree, state);
                        } else {
                                assert((msg->any.head.cmd & DMSGF_REPLY) == 0);
                                RB_REMOVE(dmsg_state_tree,
                                          &iocom->statewr_tree, state);
                        }
                        state->flags &= ~DMSG_STATE_RBINSERTED;
                        dmsg_subq_delete(state);

                        if (state->relay) {
                                dmsg_state_drop(state->relay);
                                state->relay = NULL;
                        }
                        dmsg_state_drop(state); /* state->rbtree */
                } else if ((state->txcmd & DMSGF_DELETE) == 0) {
                        state->txcmd |= DMSGF_DELETE;
                }
        }

        /*
         * Deferred abort after transmission.
         */
        if ((state->flags & (DMSG_STATE_ABORTING | DMSG_STATE_DYING)) &&
            (state->rxcmd & DMSGF_DELETE) == 0) {
                dmio_printf(iocom, 4,
                            "cleanuptx: state=%p "
                            "executing deferred abort\n",
                            state);
                state->flags &= ~DMSG_STATE_ABORTING;
                dmsg_simulate_failure(state, 1, DMSG_ERR_LOSTLINK);
        }

        dmsg_state_drop(state);
}

/*
 * Called with or without locks
 */
void
dmsg_state_hold(dmsg_state_t *state)
{
        atomic_add_int(&state->refs, 1);
}

void
dmsg_state_drop(dmsg_state_t *state)
{
        assert(state->refs > 0);
        if (atomic_fetchadd_int(&state->refs, -1) == 1)
                dmsg_state_free(state);
}

/*
 * Called with iocom locked
 */
static void
dmsg_state_free(dmsg_state_t *state)
{
        atomic_add_int(&dmsg_state_count, -1);
        dmio_printf(state->iocom, 5, "terminate state %p\n", state);
        assert((state->flags & (DMSG_STATE_ROOT |
                                DMSG_STATE_SUBINSERTED |
                                DMSG_STATE_RBINSERTED)) == 0);
        assert(TAILQ_EMPTY(&state->subq));
        assert(state->refs == 0);
        if (state->any.any != NULL)   /* XXX avoid deadlock w/exit & kernel */
                closefrom(3);
        assert(state->any.any == NULL);
        free(state);
}

/*
 * This swaps endian for a hammer2_msg_hdr.  Note that the extended
 * header is not adjusted, just the core header.
 */
void
dmsg_bswap_head(dmsg_hdr_t *head)
{
        head->magic     = bswap16(head->magic);
        head->reserved02 = bswap16(head->reserved02);
        head->salt      = bswap32(head->salt);

        head->msgid     = bswap64(head->msgid);
        head->circuit   = bswap64(head->circuit);
        head->link_verifier= bswap64(head->link_verifier);

        head->cmd       = bswap32(head->cmd);
        head->aux_crc   = bswap32(head->aux_crc);
        head->aux_bytes = bswap32(head->aux_bytes);
        head->error     = bswap32(head->error);
        head->aux_descr = bswap64(head->aux_descr);
        head->reserved38= bswap32(head->reserved38);
        head->hdr_crc   = bswap32(head->hdr_crc);
}