hammer2 - more dmsg/separation work

[dragonfly.git] / sys / kern / kern_dmsg.c

/*-
 * Copyright (c) 2012 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 *
 * 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.
 */
/*
 * TODO: txcmd CREATE state is deferred by txmsgq, need to calculate
 *       a streaming response.  See subr_diskiocom()'s diskiodone().
 */
#include <sys/param.h>
#include <sys/types.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/systm.h>
#include <sys/queue.h>
#include <sys/tree.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/socket.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/proc.h>
#include <sys/priv.h>
#include <sys/thread.h>
#include <sys/globaldata.h>
#include <sys/limits.h>

#include <sys/dmsg.h>

RB_GENERATE(kdmsg_state_tree, kdmsg_state, rbnode, kdmsg_state_cmp);
RB_GENERATE(kdmsg_circuit_tree, kdmsg_circuit, rbnode, kdmsg_circuit_cmp);

static int kdmsg_msg_receive_handling(kdmsg_msg_t *msg);
static int kdmsg_circ_msgrx(kdmsg_msg_t *msg);
static int kdmsg_state_msgrx(kdmsg_msg_t *msg);
static int kdmsg_state_msgtx(kdmsg_msg_t *msg);
static void kdmsg_state_cleanuprx(kdmsg_msg_t *msg);
static void kdmsg_state_cleanuptx(kdmsg_msg_t *msg);
static void kdmsg_state_abort(kdmsg_state_t *state);
static void kdmsg_state_free(kdmsg_state_t *state);

static void kdmsg_iocom_thread_rd(void *arg);
static void kdmsg_iocom_thread_wr(void *arg);
static int kdmsg_autorxmsg(kdmsg_msg_t *msg);
static void kdmsg_autocirc(kdmsg_msg_t *msg);
static int kdmsg_autocirc_reply(kdmsg_state_t *state, kdmsg_msg_t *msg);

static struct lwkt_token kdmsg_token = LWKT_TOKEN_INITIALIZER(kdmsg_token);

void
kdmsg_circ_hold(kdmsg_circuit_t *circ)
{
        atomic_add_int(&circ->refs, 1);
}

void
kdmsg_circ_drop(kdmsg_circuit_t *circ)
{
        kdmsg_iocom_t *iocom;

        if (atomic_fetchadd_int(&circ->refs, -1) == 1) {
                KKASSERT(circ->span_state == NULL &&
                         circ->circ_state == NULL &&
                         circ->rcirc_state == NULL &&
                         circ->recorded == 0);
                iocom = circ->iocom;
                circ->iocom = NULL;
                kfree(circ, iocom->mmsg);
        }
}


/*
 * Initialize the roll-up communications structure for a network
 * messaging session.  This function does not install the socket.
 */
void
kdmsg_iocom_init(kdmsg_iocom_t *iocom, void *handle, uint32_t flags,
                 struct malloc_type *mmsg,
                 int (*rcvmsg)(kdmsg_msg_t *msg))
{
        bzero(iocom, sizeof(*iocom));
        iocom->handle = handle;
        iocom->mmsg = mmsg;
        iocom->rcvmsg = rcvmsg;
        iocom->flags = flags;
        lockinit(&iocom->msglk, "h2msg", 0, 0);
        TAILQ_INIT(&iocom->msgq);
        RB_INIT(&iocom->circ_tree);
        RB_INIT(&iocom->staterd_tree);
        RB_INIT(&iocom->statewr_tree);
}

/*
 * [Re]connect using the passed file pointer.  The caller must ref the
 * fp for us.  We own that ref now.
 */
void
kdmsg_iocom_reconnect(kdmsg_iocom_t *iocom, struct file *fp,
                      const char *subsysname)
{
        /*
         * Destroy the current connection
         */
        lockmgr(&iocom->msglk, LK_EXCLUSIVE);
        atomic_set_int(&iocom->msg_ctl, KDMSG_CLUSTERCTL_KILL);
        while (iocom->msgrd_td || iocom->msgwr_td) {
                wakeup(&iocom->msg_ctl);
                lksleep(iocom, &iocom->msglk, 0, "clstrkl", hz);
        }

        /*
         * Drop communications descriptor
         */
        if (iocom->msg_fp) {
                fdrop(iocom->msg_fp);
                iocom->msg_fp = NULL;
        }

        /*
         * Setup new communications descriptor
         */
        iocom->msg_ctl = 0;
        iocom->msg_fp = fp;
        iocom->msg_seq = 0;
        iocom->flags &= ~KDMSG_IOCOMF_EXITNOACC;

        lwkt_create(kdmsg_iocom_thread_rd, iocom, &iocom->msgrd_td,
                    NULL, 0, -1, "%s-msgrd", subsysname);
        lwkt_create(kdmsg_iocom_thread_wr, iocom, &iocom->msgwr_td,
                    NULL, 0, -1, "%s-msgwr", subsysname);
        lockmgr(&iocom->msglk, LK_RELEASE);
}

/*
 * Caller sets up iocom->auto_lnk_conn and iocom->auto_lnk_span, then calls
 * this function to handle the state machine for LNK_CONN and LNK_SPAN.
 *
 * NOTE: Caller typically also sets the IOCOMF_AUTOCONN, IOCOMF_AUTORXSPAN,
 *       and IOCOMF_AUTORXCIRC in the kdmsg_iocom_init() call.  Clients
 *       typically set IOCOMF_AUTOTXCIRC to automatically forged circuits
 *       for received SPANs.
 */
static int kdmsg_lnk_conn_reply(kdmsg_state_t *state, kdmsg_msg_t *msg);
static int kdmsg_lnk_span_reply(kdmsg_state_t *state, kdmsg_msg_t *msg);

void
kdmsg_iocom_autoinitiate(kdmsg_iocom_t *iocom,
                         void (*auto_callback)(kdmsg_msg_t *msg))
{
        kdmsg_msg_t *msg;

        iocom->auto_callback = auto_callback;

        msg = kdmsg_msg_alloc(iocom, NULL,
                              DMSG_LNK_CONN | DMSGF_CREATE,
                              kdmsg_lnk_conn_reply, NULL);
        iocom->auto_lnk_conn.head = msg->any.head;
        msg->any.lnk_conn = iocom->auto_lnk_conn;
        iocom->conn_state = msg->state;
        kdmsg_msg_write(msg);
}

static
int
kdmsg_lnk_conn_reply(kdmsg_state_t *state, kdmsg_msg_t *msg)
{
        kdmsg_iocom_t *iocom = state->iocom;
        kdmsg_msg_t *rmsg;

        /*
         * Upon receipt of the LNK_CONN acknowledgement initiate an
         * automatic SPAN if we were asked to.  Used by e.g. xdisk, but
         * not used by HAMMER2 which must manage more than one transmitted
         * SPAN.
         */
        if ((msg->any.head.cmd & DMSGF_CREATE) &&
            (iocom->flags & KDMSG_IOCOMF_AUTOTXSPAN)) {
                rmsg = kdmsg_msg_alloc(iocom, NULL,
                                       DMSG_LNK_SPAN | DMSGF_CREATE,
                                       kdmsg_lnk_span_reply, NULL);
                iocom->auto_lnk_span.head = rmsg->any.head;
                rmsg->any.lnk_span = iocom->auto_lnk_span;
                kdmsg_msg_write(rmsg);
        }

        /*
         * Process shim after the CONN is acknowledged and before the CONN
         * transaction is deleted.  For deletions this gives device drivers
         * the ability to interlock new operations on the circuit before
         * it becomes illegal and panics.
         */
        if (iocom->auto_callback)
                iocom->auto_callback(msg);

        if ((state->txcmd & DMSGF_DELETE) == 0 &&
            (msg->any.head.cmd & DMSGF_DELETE)) {
                iocom->conn_state = NULL;
                kdmsg_msg_reply(msg, 0);
        }

        return (0);
}

static
int
kdmsg_lnk_span_reply(kdmsg_state_t *state, kdmsg_msg_t *msg)
{
        /*
         * Be sure to process shim before terminating the SPAN
         * transaction.  Gives device drivers the ability to
         * interlock new operations on the circuit before it
         * becomes illegal and panics.
         */
        if (state->iocom->auto_callback)
                state->iocom->auto_callback(msg);

        if ((state->txcmd & DMSGF_DELETE) == 0 &&
            (msg->any.head.cmd & DMSGF_DELETE)) {
                kdmsg_msg_reply(msg, 0);
        }
        return (0);
}

/*
 * Disconnect and clean up
 */
void
kdmsg_iocom_uninit(kdmsg_iocom_t *iocom)
{
        kdmsg_state_t *state;

        /*
         * Ask the cluster controller to go away
         */
        lockmgr(&iocom->msglk, LK_EXCLUSIVE);
        atomic_set_int(&iocom->msg_ctl, KDMSG_CLUSTERCTL_KILL);

        while (iocom->msgrd_td || iocom->msgwr_td) {
                wakeup(&iocom->msg_ctl);
                lksleep(iocom, &iocom->msglk, 0, "clstrkl", hz);
        }

        /*
         * Cleanup caches
         */
        if ((state = iocom->freerd_state) != NULL) {
                iocom->freerd_state = NULL;
                kdmsg_state_free(state);
        }

        if ((state = iocom->freewr_state) != NULL) {
                iocom->freewr_state = NULL;
                kdmsg_state_free(state);
        }

        /*
         * Drop communications descriptor
         */
        if (iocom->msg_fp) {
                fdrop(iocom->msg_fp);
                iocom->msg_fp = NULL;
        }
        lockmgr(&iocom->msglk, LK_RELEASE);
}

/*
 * Cluster controller thread.  Perform messaging functions.  We have one
 * thread for the reader and one for the writer.  The writer handles
 * shutdown requests (which should break the reader thread).
 */
static
void
kdmsg_iocom_thread_rd(void *arg)
{
        kdmsg_iocom_t *iocom = arg;
        dmsg_hdr_t hdr;
        kdmsg_msg_t *msg = NULL;
        size_t hbytes;
        size_t abytes;
        int error = 0;

        while ((iocom->msg_ctl & KDMSG_CLUSTERCTL_KILL) == 0) {
                /*
                 * Retrieve the message from the pipe or socket.
                 */
                error = fp_read(iocom->msg_fp, &hdr, sizeof(hdr),
                                NULL, 1, UIO_SYSSPACE);
                if (error)
                        break;
                if (hdr.magic != DMSG_HDR_MAGIC) {
                        kprintf("kdmsg: bad magic: %04x\n", hdr.magic);
                        error = EINVAL;
                        break;
                }
                hbytes = (hdr.cmd & DMSGF_SIZE) * DMSG_ALIGN;
                if (hbytes < sizeof(hdr) || hbytes > DMSG_AUX_MAX) {
                        kprintf("kdmsg: bad header size %zd\n", hbytes);
                        error = EINVAL;
                        break;
                }
                /* XXX messy: mask cmd to avoid allocating state */
                msg = kdmsg_msg_alloc(iocom, NULL,
                                      hdr.cmd & DMSGF_BASECMDMASK,
                                      NULL, NULL);
                msg->any.head = hdr;
                msg->hdr_size = hbytes;
                if (hbytes > sizeof(hdr)) {
                        error = fp_read(iocom->msg_fp, &msg->any.head + 1,
                                        hbytes - sizeof(hdr),
                                        NULL, 1, UIO_SYSSPACE);
                        if (error) {
                                kprintf("kdmsg: short msg received\n");
                                error = EINVAL;
                                break;
                        }
                }
                msg->aux_size = hdr.aux_bytes;
                if (msg->aux_size > DMSG_AUX_MAX) {
                        kprintf("kdmsg: illegal msg payload size %zd\n",
                                msg->aux_size);
                        error = EINVAL;
                        break;
                }
                if (msg->aux_size) {
                        abytes = DMSG_DOALIGN(msg->aux_size);
                        msg->aux_data = kmalloc(abytes, iocom->mmsg, M_WAITOK);
                        msg->flags |= KDMSG_FLAG_AUXALLOC;
                        error = fp_read(iocom->msg_fp, msg->aux_data,
                                        abytes, NULL, 1, UIO_SYSSPACE);
                        if (error) {
                                kprintf("kdmsg: short msg payload received\n");
                                break;
                        }
                }

                (void)kdmsg_circ_msgrx(msg);
                error = kdmsg_msg_receive_handling(msg);
                msg = NULL;
        }

        if (error)
                kprintf("kdmsg: read failed error %d\n", error);

        lockmgr(&iocom->msglk, LK_EXCLUSIVE);
        if (msg)
                kdmsg_msg_free(msg);

        /*
         * Shutdown the socket before waiting for the transmit side.
         *
         * If we are dying due to e.g. a socket disconnect verses being
         * killed explicity we have to set KILL in order to kick the tx
         * side when it might not have any other work to do.  KILL might
         * already be set if we are in an unmount or reconnect.
         */
        fp_shutdown(iocom->msg_fp, SHUT_RDWR);

        atomic_set_int(&iocom->msg_ctl, KDMSG_CLUSTERCTL_KILL);
        wakeup(&iocom->msg_ctl);

        /*
         * Wait for the transmit side to drain remaining messages
         * before cleaning up the rx state.  The transmit side will
         * set KILLTX and wait for the rx side to completely finish
         * (set msgrd_td to NULL) before cleaning up any remaining
         * tx states.
         */
        lockmgr(&iocom->msglk, LK_RELEASE);
        atomic_set_int(&iocom->msg_ctl, KDMSG_CLUSTERCTL_KILLRX);
        wakeup(&iocom->msg_ctl);
        while ((iocom->msg_ctl & KDMSG_CLUSTERCTL_KILLTX) == 0) {
                wakeup(&iocom->msg_ctl);
                tsleep(iocom, 0, "clstrkw", hz);
        }

        iocom->msgrd_td = NULL;

        /*
         * iocom can be ripped out from under us at this point but
         * wakeup() is safe.
         */
        wakeup(iocom);
        lwkt_exit();
}

static
void
kdmsg_iocom_thread_wr(void *arg)
{
        kdmsg_iocom_t *iocom = arg;
        kdmsg_msg_t *msg;
        kdmsg_state_t *state;
        ssize_t res;
        size_t abytes;
        int error = 0;
        int retries = 20;

        /*
         * Transmit loop
         */
        msg = NULL;
        lockmgr(&iocom->msglk, LK_EXCLUSIVE);

        while ((iocom->msg_ctl & KDMSG_CLUSTERCTL_KILL) == 0 && error == 0) {
                /*
                 * Sleep if no messages pending.  Interlock with flag while
                 * holding msglk.
                 */
                if (TAILQ_EMPTY(&iocom->msgq)) {
                        atomic_set_int(&iocom->msg_ctl,
                                       KDMSG_CLUSTERCTL_SLEEPING);
                        lksleep(&iocom->msg_ctl, &iocom->msglk, 0, "msgwr", hz);
                        atomic_clear_int(&iocom->msg_ctl,
                                         KDMSG_CLUSTERCTL_SLEEPING);
                }

                while ((msg = TAILQ_FIRST(&iocom->msgq)) != NULL) {
                        /*
                         * Remove msg from the transmit queue and do
                         * persist and half-closed state handling.
                         */
                        TAILQ_REMOVE(&iocom->msgq, msg, qentry);
                        lockmgr(&iocom->msglk, LK_RELEASE);

                        error = kdmsg_state_msgtx(msg);
                        if (error == EALREADY) {
                                error = 0;
                                kdmsg_msg_free(msg);
                                lockmgr(&iocom->msglk, LK_EXCLUSIVE);
                                continue;
                        }
                        if (error) {
                                kdmsg_msg_free(msg);
                                lockmgr(&iocom->msglk, LK_EXCLUSIVE);
                                break;
                        }

                        /*
                         * Dump the message to the pipe or socket.
                         *
                         * We have to clean up the message as if the transmit
                         * succeeded even if it failed.
                         */
                        error = fp_write(iocom->msg_fp, &msg->any,
                                         msg->hdr_size, &res, UIO_SYSSPACE);
                        if (error || res != msg->hdr_size) {
                                if (error == 0)
                                        error = EINVAL;
                                kdmsg_state_cleanuptx(msg);
                                lockmgr(&iocom->msglk, LK_EXCLUSIVE);
                                break;
                        }
                        if (msg->aux_size) {
                                abytes = DMSG_DOALIGN(msg->aux_size);
                                error = fp_write(iocom->msg_fp,
                                                 msg->aux_data, abytes,
                                                 &res, UIO_SYSSPACE);
                                if (error || res != abytes) {
                                        if (error == 0)
                                                error = EINVAL;
                                        kdmsg_state_cleanuptx(msg);
                                        lockmgr(&iocom->msglk, LK_EXCLUSIVE);
                                        break;
                                }
                        }
                        kdmsg_state_cleanuptx(msg);
                        lockmgr(&iocom->msglk, LK_EXCLUSIVE);
                }
        }

        /*
         * Cleanup messages pending transmission and release msgq lock.
         */
        if (error)
                kprintf("kdmsg: write failed error %d\n", error);
        kprintf("thread_wr: Terminating iocom\n");

        /*
         * Shutdown the socket.  This will cause the rx thread to get an
         * EOF and ensure that both threads get to a termination state.
         */
        fp_shutdown(iocom->msg_fp, SHUT_RDWR);

        /*
         * Set KILLTX (which the rx side waits for), then wait for the RX
         * side to completely finish before we clean out any remaining
         * command states.
         */
        lockmgr(&iocom->msglk, LK_RELEASE);
        atomic_set_int(&iocom->msg_ctl, KDMSG_CLUSTERCTL_KILLTX);
        wakeup(&iocom->msg_ctl);
        while (iocom->msgrd_td) {
                wakeup(&iocom->msg_ctl);
                tsleep(iocom, 0, "clstrkw", hz);
        }
        lockmgr(&iocom->msglk, LK_EXCLUSIVE);

        /*
         * Simulate received MSGF_DELETE's for any remaining states.
         * (For remote masters).
         *
         * Drain the message queue to handle any device initiated writes
         * due to state callbacks.
         */
cleanuprd:
        kdmsg_drain_msgq(iocom);
        RB_FOREACH(state, kdmsg_state_tree, &iocom->staterd_tree) {
                if ((state->rxcmd & DMSGF_DELETE) == 0) {
                        lockmgr(&iocom->msglk, LK_RELEASE);
                        kdmsg_state_abort(state);
                        lockmgr(&iocom->msglk, LK_EXCLUSIVE);
                        goto cleanuprd;
                }
        }

        /*
         * Simulate received MSGF_DELETE's for any remaining states.
         * (For local masters).
         */
cleanupwr:
        kdmsg_drain_msgq(iocom);
        RB_FOREACH(state, kdmsg_state_tree, &iocom->statewr_tree) {
                if ((state->rxcmd & DMSGF_DELETE) == 0) {
                        lockmgr(&iocom->msglk, LK_RELEASE);
                        kdmsg_state_abort(state);
                        lockmgr(&iocom->msglk, LK_EXCLUSIVE);
                        goto cleanupwr;
                }
        }

        /*
         * Retry until all work is done
         */
        if (--retries == 0)
                panic("kdmsg: comm thread shutdown couldn't drain");
        if (TAILQ_FIRST(&iocom->msgq) ||
            RB_ROOT(&iocom->staterd_tree) ||
            RB_ROOT(&iocom->statewr_tree)) {
                goto cleanuprd;
        }
        iocom->flags |= KDMSG_IOCOMF_EXITNOACC;

        lockmgr(&iocom->msglk, LK_RELEASE);

        /*
         * The state trees had better be empty now
         */
        KKASSERT(RB_EMPTY(&iocom->staterd_tree));
        KKASSERT(RB_EMPTY(&iocom->statewr_tree));
        KKASSERT(iocom->conn_state == NULL);

        if (iocom->exit_func) {
                /*
                 * iocom is invalid after we call the exit function.
                 */
                iocom->msgwr_td = NULL;
                iocom->exit_func(iocom);
        } else {
                /*
                 * iocom can be ripped out from under us once msgwr_td is
                 * set to NULL.  The wakeup is safe.
                 */
                iocom->msgwr_td = NULL;
                wakeup(iocom);
        }
        lwkt_exit();
}

/*
 * This cleans out the pending transmit message queue, adjusting any
 * persistent states properly in the process.
 *
 * Caller must hold pmp->iocom.msglk
 */
void
kdmsg_drain_msgq(kdmsg_iocom_t *iocom)
{
        kdmsg_msg_t *msg;

        /*
         * Clean out our pending transmit queue, executing the
         * appropriate state adjustments.  If this tries to open
         * any new outgoing transactions we have to loop up and
         * clean them out.
         */
        while ((msg = TAILQ_FIRST(&iocom->msgq)) != NULL) {
                TAILQ_REMOVE(&iocom->msgq, msg, qentry);
                lockmgr(&iocom->msglk, LK_RELEASE);
                if (kdmsg_state_msgtx(msg))
                        kdmsg_msg_free(msg);
                else
                        kdmsg_state_cleanuptx(msg);
                lockmgr(&iocom->msglk, LK_EXCLUSIVE);
        }
}

/*
 * Do all processing required to handle a freshly received message
 * after its low level header has been validated.
 */
static
int
kdmsg_msg_receive_handling(kdmsg_msg_t *msg)
{
        kdmsg_iocom_t *iocom = msg->iocom;
        int error;

        /*
         * State machine tracking, state assignment for msg,
         * returns error and discard status.  Errors are fatal
         * to the connection except for EALREADY which forces
         * a discard without execution.
         */
        error = kdmsg_state_msgrx(msg);
        if (error) {
                /*
                 * Raw protocol or connection error
                 */
                kdmsg_msg_free(msg);
                if (error == EALREADY)
                        error = 0;
        } else if (msg->state && msg->state->func) {
                /*
                 * Message related to state which already has a
                 * handling function installed for it.
                 */
                error = msg->state->func(msg->state, msg);
                kdmsg_state_cleanuprx(msg);
        } else if (iocom->flags & KDMSG_IOCOMF_AUTOANY) {
                error = kdmsg_autorxmsg(msg);
                kdmsg_state_cleanuprx(msg);
        } else {
                error = iocom->rcvmsg(msg);
                kdmsg_state_cleanuprx(msg);
        }
        return error;
}

/*
 * Process circuit tracking (NEEDS WORK)
 */
static
int
kdmsg_circ_msgrx(kdmsg_msg_t *msg)
{
        kdmsg_circuit_t dummy;
        kdmsg_circuit_t *circ;
        int error = 0;

        if (msg->any.head.circuit) {
                dummy.msgid = msg->any.head.circuit;
                lwkt_gettoken(&kdmsg_token);
                circ = RB_FIND(kdmsg_circuit_tree, &msg->iocom->circ_tree,
                               &dummy);
                if (circ) {
                        msg->circ = circ;
                        kdmsg_circ_hold(circ);
                }
                if (circ == NULL) {
                        kprintf("KDMSG_CIRC_MSGRX CMD %08x: IOCOM %p "
                                "Bad circuit %016jx\n",
                                msg->any.head.cmd,
                                msg->iocom,
                                (intmax_t)msg->any.head.circuit);
                        kprintf("KDMSG_CIRC_MSGRX: Avail circuits: ");
                        RB_FOREACH(circ, kdmsg_circuit_tree,
                                   &msg->iocom->circ_tree) {
                                kprintf(" %016jx", (intmax_t)circ->msgid);
                        }
                        kprintf("\n");
                        error = EINVAL;
                }
                lwkt_reltoken(&kdmsg_token);
        }
        return (error);
}

/*
 * Process state tracking for a message after reception, prior to
 * execution.
 *
 * 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.
 *
 * --
 *
 * 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 with neither CREATE or DELETE
 * set.  One-off messages cannot be aborted and typically aren't processed
 * by these routines.  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
kdmsg_state_msgrx(kdmsg_msg_t *msg)
{
        kdmsg_iocom_t *iocom = msg->iocom;
        kdmsg_state_t *state;
        int error;

        /*
         * Make sure a state structure is ready to go in case we need a new
         * one.  This is the only routine which uses freerd_state so no
         * races are possible.
         */
        if ((state = iocom->freerd_state) == NULL) {
                state = kmalloc(sizeof(*state), iocom->mmsg, M_WAITOK | M_ZERO);
                state->flags = KDMSG_STATE_DYNAMIC;
                iocom->freerd_state = state;
        }

        /*
         * Lock RB tree and locate existing persistent state, if any.
         *
         * If received msg is a command state is on staterd_tree.
         * If received msg is a reply state is on statewr_tree.
         */
        lockmgr(&iocom->msglk, LK_EXCLUSIVE);

        state->msgid = msg->any.head.msgid;
        state->circ = msg->circ;
        state->iocom = iocom;
        if (msg->any.head.cmd & DMSGF_REPLY)
                state = RB_FIND(kdmsg_state_tree, &iocom->statewr_tree, state);
        else
                state = RB_FIND(kdmsg_state_tree, &iocom->staterd_tree, state);
        msg->state = state;

        /*
         * Short-cut one-off or mid-stream messages (state may be NULL).
         */
        if ((msg->any.head.cmd & (DMSGF_CREATE | DMSGF_DELETE |
                                  DMSGF_ABORT)) == 0) {
                goto done;
        }

        /*
         * Switch on CREATE, DELETE, REPLY, and also handle ABORT from
         * inside the case statements.
         */
        switch(msg->any.head.cmd & (DMSGF_CREATE|DMSGF_DELETE|DMSGF_REPLY)) {
        case DMSGF_CREATE:
        case DMSGF_CREATE | DMSGF_DELETE:
                /*
                 * New persistant command received.
                 */
                if (state) {
                        kprintf("kdmsg_state_msgrx: duplicate transaction\n");
                        error = EINVAL;
                        break;
                }
                state = iocom->freerd_state;
                iocom->freerd_state = NULL;
                msg->state = state;
                state->msg = msg;
                state->icmd = msg->any.head.cmd & DMSGF_BASECMDMASK;
                state->rxcmd = msg->any.head.cmd & ~DMSGF_DELETE;
                state->txcmd = DMSGF_REPLY;
                state->msgid = msg->any.head.msgid;
                if ((state->circ = msg->circ) != NULL)
                        kdmsg_circ_hold(state->circ);
                RB_INSERT(kdmsg_state_tree, &iocom->staterd_tree, state);
                state->flags |= KDMSG_STATE_INSERTED;
                error = 0;
                break;
        case DMSGF_DELETE:
                /*
                 * Persistent state is expected but might not exist if an
                 * ABORT+DELETE races the close.
                 */
                if (state == NULL) {
                        if (msg->any.head.cmd & DMSGF_ABORT) {
                                error = EALREADY;
                        } else {
                                kprintf("kdmsg_state_msgrx: "
                                        "no state for DELETE\n");
                                error = EINVAL;
                        }
                        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 = EALREADY;
                        } else {
                                kprintf("kdmsg_state_msgrx: "
                                        "state reused for DELETE\n");
                                error = EINVAL;
                        }
                        break;
                }
                error = 0;
                break;
        default:
                /*
                 * Check for mid-stream ABORT command received, otherwise
                 * allow.
                 */
                if (msg->any.head.cmd & DMSGF_ABORT) {
                        if (state == NULL ||
                            (state->rxcmd & DMSGF_CREATE) == 0) {
                                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 == NULL) {
                        kprintf("kdmsg_state_msgrx: no state match for "
                                "REPLY cmd=%08x msgid=%016jx\n",
                                msg->any.head.cmd,
                                (intmax_t)msg->any.head.msgid);
                        error = EINVAL;
                        break;
                }
                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 == NULL) {
                        if (msg->any.head.cmd & DMSGF_ABORT) {
                                error = EALREADY;
                        } else {
                                kprintf("kdmsg_state_msgrx: no state match "
                                        "for REPLY|DELETE\n");
                                error = EINVAL;
                        }
                        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 = EALREADY;
                        } else {
                                kprintf("kdmsg_state_msgrx: state reused "
                                        "for REPLY|DELETE\n");
                                error = EINVAL;
                        }
                        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 == NULL ||
                            (state->rxcmd & DMSGF_CREATE) == 0) {
                                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.
         */
done:
        lockmgr(&iocom->msglk, LK_RELEASE);

        if (msg->any.head.cmd & (DMSGF_CREATE | DMSGF_DELETE)) {
                if (state) {
                        msg->tcmd = (msg->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;
        }
        return (error);
}

/*
 * Called instead of iocom->rcvmsg() if any of the AUTO flags are set.
 * This routine must call iocom->rcvmsg() for anything not automatically
 * handled.
 */
static int
kdmsg_autorxmsg(kdmsg_msg_t *msg)
{
        kdmsg_iocom_t *iocom = msg->iocom;
        kdmsg_circuit_t *circ;
        int error = 0;
        uint32_t cmd;

        /*
         * Main switch processes transaction create/delete sequences only.
         * Use icmd (DELETEs use DMSG_LNK_ERROR
         *
         * NOTE: If processing in-transaction messages you generally want
         *       an inner switch on msg->any.head.cmd.
         */
        if (msg->state) {
                cmd = (msg->state->icmd & DMSGF_BASECMDMASK) |
                      (msg->any.head.cmd & (DMSGF_CREATE |
                                            DMSGF_DELETE |
                                            DMSGF_REPLY));
        } else {
                cmd = 0;
        }

        switch(cmd) {
        case DMSG_LNK_CONN | DMSGF_CREATE:
        case DMSG_LNK_CONN | DMSGF_CREATE | DMSGF_DELETE:
                /*
                 * Received LNK_CONN transaction.  Transmit response and
                 * leave transaction open, which allows the other end to
                 * start to the SPAN protocol.
                 *
                 * Handle shim after acknowledging the CONN.
                 */
                if ((msg->any.head.cmd & DMSGF_DELETE) == 0) {
                        if (iocom->flags & KDMSG_IOCOMF_AUTOCONN) {
                                kdmsg_msg_result(msg, 0);
                                if (iocom->auto_callback)
                                        iocom->auto_callback(msg);
                        } else {
                                error = iocom->rcvmsg(msg);
                        }
                        break;
                }
                /* fall through */
        case DMSG_LNK_CONN | DMSGF_DELETE:
                /*
                 * This message is usually simulated after a link is lost
                 * to clean up the transaction.
                 */
                if (iocom->flags & KDMSG_IOCOMF_AUTOCONN) {
                        if (iocom->auto_callback)
                                iocom->auto_callback(msg);
                        kdmsg_msg_reply(msg, 0);
                } else {
                        error = iocom->rcvmsg(msg);
                }
                break;
        case DMSG_LNK_SPAN | DMSGF_CREATE:
        case DMSG_LNK_SPAN | DMSGF_CREATE | DMSGF_DELETE:
                /*
                 * Received LNK_SPAN transaction.  We do not have to respond
                 * but we must leave the transaction open.
                 *
                 * If AUTOTXCIRC is set automatically initiate a virtual
                 * circuit to the received span.  This will attach a
                 * kdmsg_circuit to the SPAN state.  The circuit is lost
                 * when the span is lost.
                 *
                 * Handle shim after acknowledging the SPAN.
                 */
                if (iocom->flags & KDMSG_IOCOMF_AUTORXSPAN) {
                        if ((msg->any.head.cmd & DMSGF_DELETE) == 0) {
                                if (iocom->flags & KDMSG_IOCOMF_AUTOTXCIRC)
                                        kdmsg_autocirc(msg);
                                if (iocom->auto_callback)
                                        iocom->auto_callback(msg);
                                break;
                        }
                        /* fall through */
                } else {
                        error = iocom->rcvmsg(msg);
                        break;
                }
                /* fall through */
        case DMSG_LNK_SPAN | DMSGF_DELETE:
                /*
                 * Process shims (auto_callback) before cleaning up the
                 * circuit structure and closing the transactions.  Device
                 * driver should ensure that the circuit is not used after
                 * the auto_callback() returns.
                 *
                 * Handle shim before closing the SPAN transaction.
                 */
                if (iocom->flags & KDMSG_IOCOMF_AUTORXSPAN) {
                        if (iocom->auto_callback)
                                iocom->auto_callback(msg);
                        if (iocom->flags & KDMSG_IOCOMF_AUTOTXCIRC)
                                kdmsg_autocirc(msg);
                        kdmsg_msg_reply(msg, 0);
                } else {
                        error = iocom->rcvmsg(msg);
                }
                break;
        case DMSG_LNK_CIRC | DMSGF_CREATE:
        case DMSG_LNK_CIRC | DMSGF_CREATE | DMSGF_DELETE:
                /*
                 * Received LNK_CIRC transaction.  We must respond and should
                 * leave the transaction open, allowing the circuit.  The
                 * remote can start issuing commands to us over the circuit
                 * even before we respond.
                 */
                if (iocom->flags & KDMSG_IOCOMF_AUTORXCIRC) {
                        if ((msg->any.head.cmd & DMSGF_DELETE) == 0) {
                                circ = kmalloc(sizeof(*circ), iocom->mmsg,
                                               M_WAITOK | M_ZERO);
                                lwkt_gettoken(&kdmsg_token);
                                msg->state->any.circ = circ;
                                circ->iocom = iocom;
                                circ->rcirc_state = msg->state;
                                kdmsg_circ_hold(circ);  /* for rcirc_state */
                                circ->weight = 0;
                                circ->msgid = circ->rcirc_state->msgid;
                                /* XXX no span link for received circuits */
                                kdmsg_circ_hold(circ);  /* for circ_state */

                                if (RB_INSERT(kdmsg_circuit_tree,
                                              &iocom->circ_tree, circ)) {
                                        panic("duplicate circuitid allocated");
                                }
                                lwkt_reltoken(&kdmsg_token);
                                kdmsg_msg_result(msg, 0);

                                /*
                                 * Handle shim after adding the circuit and
                                 * after acknowledging the CIRC.
                                 */
                                if (iocom->auto_callback)
                                        iocom->auto_callback(msg);
                                break;
                        }
                        /* fall through */
                } else {
                        error = iocom->rcvmsg(msg);
                        break;
                }
                /* fall through */
        case DMSG_LNK_CIRC | DMSGF_DELETE:
                if (iocom->flags & KDMSG_IOCOMF_AUTORXCIRC) {
                        circ = msg->state->any.circ;
                        if (circ == NULL)
                                break;

                        /*
                         * Handle shim before terminating the circuit.
                         */
#if 0
                        kprintf("KDMSG VC: RECEIVE CIRC DELETE "
                                "IOCOM %p MSGID %016jx\n",
                                msg->iocom, circ->msgid);
#endif
                        if (iocom->auto_callback)
                                iocom->auto_callback(msg);

                        KKASSERT(circ->rcirc_state == msg->state);
                        lwkt_gettoken(&kdmsg_token);
                        circ->rcirc_state = NULL;
                        msg->state->any.circ = NULL;
                        RB_REMOVE(kdmsg_circuit_tree, &iocom->circ_tree, circ);
                        lwkt_reltoken(&kdmsg_token);
                        kdmsg_circ_drop(circ);  /* for rcirc_state */
                        kdmsg_msg_reply(msg, 0);
                } else {
                        error = iocom->rcvmsg(msg);
                }
                break;
        default:
                /*
                 * Anything unhandled goes into rcvmsg.
                 *
                 * NOTE: Replies to link-level messages initiated by our side
                 *       are handled by the state callback, they are NOT
                 *       handled here.
                 */
                error = iocom->rcvmsg(msg);
                break;
        }
        return (error);
}

/*
 * Handle automatic forging of virtual circuits based on received SPANs.
 * (AUTOTXCIRC).  Note that other code handles tracking received circuit
 * transactions (AUTORXCIRC).
 *
 * We can ignore non-transactions here.  Use trans->icmd to test the
 * transactional command (once past the CREATE the individual message
 * commands are not usually the icmd).
 *
 * XXX locks
 */
static
void
kdmsg_autocirc(kdmsg_msg_t *msg)
{
        kdmsg_iocom_t *iocom = msg->iocom;
        kdmsg_circuit_t *circ;
        kdmsg_msg_t *xmsg;      /* CIRC */

        if (msg->state == NULL)
                return;

        /*
         * Gaining the SPAN, automatically forge a circuit to the target.
         *
         * NOTE!! The shim is not executed until we receive an acknowlegement
         *        to our forged LNK_CIRC (see kdmsg_autocirc_reply()).
         */
        if (msg->state->icmd == DMSG_LNK_SPAN &&
            (msg->any.head.cmd & DMSGF_CREATE)) {
                circ = kmalloc(sizeof(*circ), iocom->mmsg, M_WAITOK | M_ZERO);
                lwkt_gettoken(&kdmsg_token);
                msg->state->any.circ = circ;
                circ->iocom = iocom;
                circ->span_state = msg->state;
                kdmsg_circ_hold(circ);  /* for span_state */
                xmsg = kdmsg_msg_alloc(iocom, NULL,
                                       DMSG_LNK_CIRC | DMSGF_CREATE,
                                       kdmsg_autocirc_reply, circ);
                circ->circ_state = xmsg->state;
                circ->weight = msg->any.lnk_span.dist;
                circ->msgid = circ->circ_state->msgid;
                kdmsg_circ_hold(circ);  /* for circ_state */
#if 0
                kprintf("KDMSG VC: CREATE SPAN->CIRC IOCOM %p MSGID %016jx\n",
                        msg->iocom, circ->msgid);
#endif

                if (RB_INSERT(kdmsg_circuit_tree, &iocom->circ_tree, circ))
                        panic("duplicate circuitid allocated");
                lwkt_reltoken(&kdmsg_token);

                xmsg->any.lnk_circ.target = msg->any.head.msgid;
                kdmsg_msg_write(xmsg);
        }

        /*
         * Losing the SPAN
         *
         * NOTE: When losing a SPAN, any circuits using the span should be
         *       deleted by the remote end first.  XXX might not be ordered
         *       on actual loss of connection.
         */
        if (msg->state->icmd == DMSG_LNK_SPAN &&
            (msg->any.head.cmd & DMSGF_DELETE) &&
            msg->state->any.circ) {
                circ = msg->state->any.circ;
                lwkt_gettoken(&kdmsg_token);
                circ->span_state = NULL;
                msg->state->any.circ = NULL;
                RB_REMOVE(kdmsg_circuit_tree, &iocom->circ_tree, circ);
#if 0
                kprintf("KDMSG VC: DELETE SPAN->CIRC IOCOM %p MSGID %016jx\n",
                        msg->iocom, (intmax_t)circ->msgid);
#endif
                kdmsg_circ_drop(circ);  /* for span_state */
                lwkt_reltoken(&kdmsg_token);
        }
}

static
int
kdmsg_autocirc_reply(kdmsg_state_t *state, kdmsg_msg_t *msg)
{
        kdmsg_iocom_t *iocom = state->iocom;
        kdmsg_circuit_t *circ = state->any.circ;

        /*
         * Call shim after receiving an acknowlegement to our forged
         * circuit and before processing a received termination.
         */
        if (iocom->auto_callback)
                iocom->auto_callback(msg);

        /*
         * If the remote is terminating the VC we terminate our side
         */
        if ((state->txcmd & DMSGF_DELETE) == 0 &&
            (msg->any.head.cmd & DMSGF_DELETE)) {
#if 0
                kprintf("KDMSG VC: DELETE CIRC FROM REMOTE\n");
#endif
                lwkt_gettoken(&kdmsg_token);
                circ->circ_state = NULL;
                state->any.circ = NULL;
                kdmsg_circ_drop(circ);          /* for circ_state */
                lwkt_reltoken(&kdmsg_token);
                kdmsg_msg_reply(msg, 0);
        }
        return (0);
}

/*
 * Post-receive-handling message and state cleanup.  This routine is called
 * after the state function handling/callback to properly dispose of the
 * message and update or dispose of the state.
 */
static
void
kdmsg_state_cleanuprx(kdmsg_msg_t *msg)
{
        kdmsg_iocom_t *iocom = msg->iocom;
        kdmsg_state_t *state;

        if ((state = msg->state) == NULL) {
                kdmsg_msg_free(msg);
        } else if (msg->any.head.cmd & DMSGF_DELETE) {
                lockmgr(&iocom->msglk, LK_EXCLUSIVE);
                KKASSERT((state->rxcmd & DMSGF_DELETE) == 0);
                state->rxcmd |= DMSGF_DELETE;
                if (state->txcmd & DMSGF_DELETE) {
                        KKASSERT(state->flags & KDMSG_STATE_INSERTED);
                        if (state->rxcmd & DMSGF_REPLY) {
                                KKASSERT(msg->any.head.cmd &
                                         DMSGF_REPLY);
                                RB_REMOVE(kdmsg_state_tree,
                                          &iocom->statewr_tree, state);
                        } else {
                                KKASSERT((msg->any.head.cmd &
                                          DMSGF_REPLY) == 0);
                                RB_REMOVE(kdmsg_state_tree,
                                          &iocom->staterd_tree, state);
                        }
                        state->flags &= ~KDMSG_STATE_INSERTED;
                        if (msg != state->msg)
                                kdmsg_msg_free(msg);
                        lockmgr(&iocom->msglk, LK_RELEASE);
                        kdmsg_state_free(state);
                } else {
                        if (msg != state->msg)
                                kdmsg_msg_free(msg);
                        lockmgr(&iocom->msglk, LK_RELEASE);
                }
        } else if (msg != state->msg) {
                kdmsg_msg_free(msg);
        }
}

/*
 * Simulate receiving a message which terminates an active transaction
 * state.  Our simulated received message must set DELETE and may also
 * have to set CREATE.  It must also ensure that all fields are set such
 * that the receive handling code can find the state (kdmsg_state_msgrx())
 * or an endless loop will ensue.
 *
 * This is used when the other end of the link or virtual circuit is dead
 * so the device driver gets a completed transaction for all pending states.
 */
static
void
kdmsg_state_abort(kdmsg_state_t *state)
{
        kdmsg_iocom_t *iocom = state->iocom;
        kdmsg_msg_t *msg;

        /*
         * Prevent recursive aborts which could otherwise occur if the
         * simulated message reception runs state->func which then turns
         * around and tries to reply to a broken circuit when then calls
         * the state abort code again.
         */
        if (state->flags & KDMSG_STATE_ABORTING)
                return;
        state->flags |= KDMSG_STATE_ABORTING;

        /*
         * Simulatem essage reception
         */
        msg = kdmsg_msg_alloc(iocom, state->circ,
                              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.error = DMSG_ERR_LOSTLINK;
        msg->any.head.msgid = state->msgid;
        msg->state = state;
        kdmsg_msg_receive_handling(msg);
}

/*
 * Process state tracking for a message prior to transmission.
 *
 * Called with msglk held and the msg dequeued.  Returns non-zero if
 * the message is bad and should be deleted by the caller.
 *
 * One-off messages are usually with dummy state and msg->state may be NULL
 * in this situation.
 *
 * New transactions (when CREATE is set) will insert the state.
 *
 * May request that caller discard the message by setting *discardp to 1.
 * A NULL state may be returned in this case.
 */
static
int
kdmsg_state_msgtx(kdmsg_msg_t *msg)
{
        kdmsg_iocom_t *iocom = msg->iocom;
        kdmsg_state_t *state;
        int error;

        /*
         * Make sure a state structure is ready to go in case we need a new
         * one.  This is the only routine which uses freewr_state so no
         * races are possible.
         */
        if ((state = iocom->freewr_state) == NULL) {
                state = kmalloc(sizeof(*state), iocom->mmsg, M_WAITOK | M_ZERO);
                state->flags = KDMSG_STATE_DYNAMIC;
                state->iocom = iocom;
                iocom->freewr_state = state;
        }

        /*
         * Lock RB tree.  If persistent state is present it will have already
         * been assigned to msg.
         */
        lockmgr(&iocom->msglk, LK_EXCLUSIVE);
        state = msg->state;

        /*
         * Short-cut one-off or mid-stream messages (state may be NULL).
         */
        if ((msg->any.head.cmd & (DMSGF_CREATE | DMSGF_DELETE |
                                  DMSGF_ABORT)) == 0) {
                lockmgr(&iocom->msglk, LK_RELEASE);
                return(0);
        }


        /*
         * Switch on CREATE, DELETE, REPLY, and also handle ABORT from
         * inside the case statements.
         */
        switch(msg->any.head.cmd & (DMSGF_CREATE | DMSGF_DELETE |
                                    DMSGF_REPLY)) {
        case DMSGF_CREATE:
        case DMSGF_CREATE | DMSGF_DELETE:
                /*
                 * Insert the new persistent message state and mark
                 * half-closed if DELETE is set.  Since this is a new
                 * message it isn't possible to transition into the fully
                 * closed state here.
                 *
                 * XXX state must be assigned and inserted by
                 *     kdmsg_msg_write().  txcmd is assigned by us
                 *     on-transmit.
                 */
                KKASSERT(state != NULL);
                state->icmd = msg->any.head.cmd & DMSGF_BASECMDMASK;
                state->txcmd = msg->any.head.cmd & ~DMSGF_DELETE;
                state->rxcmd = DMSGF_REPLY;
                error = 0;
                break;
        case DMSGF_DELETE:
                /*
                 * Sent ABORT+DELETE in case where msgid has already
                 * been fully closed, ignore the message.
                 */
                if (state == NULL) {
                        if (msg->any.head.cmd & DMSGF_ABORT) {
                                error = EALREADY;
                        } else {
                                kprintf("kdmsg_state_msgtx: no state match "
                                        "for DELETE cmd=%08x msgid=%016jx\n",
                                        msg->any.head.cmd,
                                        (intmax_t)msg->any.head.msgid);
                                error = EINVAL;
                        }
                        break;
                }

                /*
                 * Sent ABORT+DELETE in case where msgid has
                 * already been reused for an unrelated message,
                 * ignore the message.
                 */
                if ((state->txcmd & DMSGF_CREATE) == 0) {
                        if (msg->any.head.cmd & DMSGF_ABORT) {
                                error = EALREADY;
                        } else {
                                kprintf("kdmsg_state_msgtx: state reused "
                                        "for DELETE\n");
                                error = EINVAL;
                        }
                        break;
                }
                error = 0;
                break;
        default:
                /*
                 * Check for mid-stream ABORT command sent
                 */
                if (msg->any.head.cmd & DMSGF_ABORT) {
                        if (state == NULL ||
                            (state->txcmd & DMSGF_CREATE) == 0) {
                                error = EALREADY;
                                break;
                        }
                }
                error = 0;
                break;
        case DMSGF_REPLY | DMSGF_CREATE:
        case DMSGF_REPLY | DMSGF_CREATE | DMSGF_DELETE:
                /*
                 * When transmitting a reply with CREATE set the original
                 * persistent state message should already exist.
                 */
                if (state == NULL) {
                        kprintf("kdmsg_state_msgtx: no state match "
                                "for REPLY | CREATE\n");
                        error = EINVAL;
                        break;
                }
                state->txcmd = msg->any.head.cmd & ~DMSGF_DELETE;
                error = 0;
                break;
        case DMSGF_REPLY | DMSGF_DELETE:
                /*
                 * When transmitting a reply with DELETE set the original
                 * persistent state message should already exist.
                 *
                 * This is very similar to the REPLY|CREATE|* case except
                 * txcmd is already stored, so we just add the DELETE flag.
                 *
                 * Sent REPLY+ABORT+DELETE in case where msgid has
                 * already been fully closed, ignore the message.
                 */
                if (state == NULL) {
                        if (msg->any.head.cmd & DMSGF_ABORT) {
                                error = EALREADY;
                        } else {
                                kprintf("kdmsg_state_msgtx: no state match "
                                        "for REPLY | DELETE\n");
                                error = EINVAL;
                        }
                        break;
                }

                /*
                 * Sent REPLY+ABORT+DELETE in case where msgid has already
                 * been reused for an unrelated message, ignore the message.
                 */
                if ((state->txcmd & DMSGF_CREATE) == 0) {
                        if (msg->any.head.cmd & DMSGF_ABORT) {
                                error = EALREADY;
                        } else {
                                kprintf("kdmsg_state_msgtx: state reused "
                                        "for REPLY | DELETE\n");
                                error = EINVAL;
                        }
                        break;
                }
                error = 0;
                break;
        case DMSGF_REPLY:
                /*
                 * Check for mid-stream ABORT reply sent.
                 *
                 * One-off REPLY messages are allowed for e.g. status updates.
                 */
                if (msg->any.head.cmd & DMSGF_ABORT) {
                        if (state == NULL ||
                            (state->txcmd & DMSGF_CREATE) == 0) {
                                error = EALREADY;
                                break;
                        }
                }
                error = 0;
                break;
        }
        lockmgr(&iocom->msglk, LK_RELEASE);
        return (error);
}

static
void
kdmsg_state_cleanuptx(kdmsg_msg_t *msg)
{
        kdmsg_iocom_t *iocom = msg->iocom;
        kdmsg_state_t *state;

        if ((state = msg->state) == NULL) {
                kdmsg_msg_free(msg);
        } else if (msg->any.head.cmd & DMSGF_DELETE) {
                lockmgr(&iocom->msglk, LK_EXCLUSIVE);
                KKASSERT((state->txcmd & DMSGF_DELETE) == 0);
                state->txcmd |= DMSGF_DELETE;
                if (state->rxcmd & DMSGF_DELETE) {
                        KKASSERT(state->flags & KDMSG_STATE_INSERTED);
                        if (state->txcmd & DMSGF_REPLY) {
                                KKASSERT(msg->any.head.cmd &
                                         DMSGF_REPLY);
                                RB_REMOVE(kdmsg_state_tree,
                                          &iocom->staterd_tree, state);
                        } else {
                                KKASSERT((msg->any.head.cmd &
                                          DMSGF_REPLY) == 0);
                                RB_REMOVE(kdmsg_state_tree,
                                          &iocom->statewr_tree, state);
                        }
                        state->flags &= ~KDMSG_STATE_INSERTED;
                        if (msg != state->msg)
                                kdmsg_msg_free(msg);
                        lockmgr(&iocom->msglk, LK_RELEASE);
                        kdmsg_state_free(state);
                } else {
                        if (msg != state->msg)
                                kdmsg_msg_free(msg);
                        lockmgr(&iocom->msglk, LK_RELEASE);
                }
        } else if (msg != state->msg) {
                kdmsg_msg_free(msg);
        }
}

static
void
kdmsg_state_free(kdmsg_state_t *state)
{
        kdmsg_iocom_t *iocom = state->iocom;
        kdmsg_msg_t *msg;

        KKASSERT((state->flags & KDMSG_STATE_INSERTED) == 0);
        msg = state->msg;
        state->msg = NULL;
        kfree(state, iocom->mmsg);
        if (msg) {
                msg->state = NULL;
                kdmsg_msg_free(msg);
        }
}

kdmsg_msg_t *
kdmsg_msg_alloc(kdmsg_iocom_t *iocom, kdmsg_circuit_t *circ, uint32_t cmd,
                int (*func)(kdmsg_state_t *, kdmsg_msg_t *), void *data)
{
        kdmsg_msg_t *msg;
        kdmsg_state_t *state;
        size_t hbytes;

        KKASSERT(iocom != NULL);
        hbytes = (cmd & DMSGF_SIZE) * DMSG_ALIGN;
        msg = kmalloc(offsetof(struct kdmsg_msg, any) + hbytes,
                      iocom->mmsg, M_WAITOK | M_ZERO);
        msg->hdr_size = hbytes;
        msg->iocom = iocom;
        msg->any.head.magic = DMSG_HDR_MAGIC;
        msg->any.head.cmd = cmd;
        if (circ) {
                kdmsg_circ_hold(circ);
                msg->circ = circ;
                msg->any.head.circuit = circ->msgid;
        }

        if (cmd & DMSGF_CREATE) {
                /*
                 * New transaction, requires tracking state and a unique
                 * msgid to be allocated.
                 */
                KKASSERT(msg->state == NULL);
                state = kmalloc(sizeof(*state), iocom->mmsg, M_WAITOK | M_ZERO);
                state->flags = KDMSG_STATE_DYNAMIC;
                state->func = func;
                state->any.any = data;
                state->msg = msg;
                state->msgid = (uint64_t)(uintptr_t)state;
                state->circ = circ;
                state->iocom = iocom;
                msg->state = state;
                if (circ)
                        kdmsg_circ_hold(circ);
                /*msg->any.head.msgid = state->msgid;XXX*/

                lockmgr(&iocom->msglk, LK_EXCLUSIVE);
                if (RB_INSERT(kdmsg_state_tree, &iocom->statewr_tree, state))
                        panic("duplicate msgid allocated");
                state->flags |= KDMSG_STATE_INSERTED;
                msg->any.head.msgid = state->msgid;
                lockmgr(&iocom->msglk, LK_RELEASE);
        }
        return (msg);
}

kdmsg_msg_t *
kdmsg_msg_alloc_state(kdmsg_state_t *state, uint32_t cmd,
                      int (*func)(kdmsg_state_t *, kdmsg_msg_t *), void *data)
{
        kdmsg_iocom_t *iocom = state->iocom;
        kdmsg_msg_t *msg;
        size_t hbytes;

        KKASSERT(iocom != NULL);
        hbytes = (cmd & DMSGF_SIZE) * DMSG_ALIGN;
        msg = kmalloc(offsetof(struct kdmsg_msg, any) + hbytes,
                      iocom->mmsg, M_WAITOK | M_ZERO);
        msg->hdr_size = hbytes;
        msg->iocom = iocom;
        msg->any.head.magic = DMSG_HDR_MAGIC;
        msg->any.head.cmd = cmd;
        msg->state = state;
        if (state->circ) {
                kdmsg_circ_hold(state->circ);
                msg->circ = state->circ;
                msg->any.head.circuit = state->circ->msgid;
        }
        return(msg);
}

void
kdmsg_msg_free(kdmsg_msg_t *msg)
{
        kdmsg_iocom_t *iocom = msg->iocom;

        if ((msg->flags & KDMSG_FLAG_AUXALLOC) &&
            msg->aux_data && msg->aux_size) {
                kfree(msg->aux_data, iocom->mmsg);
                msg->flags &= ~KDMSG_FLAG_AUXALLOC;
        }
        if (msg->circ) {
                kdmsg_circ_drop(msg->circ);
                msg->circ = NULL;
        }
        if (msg->state) {
                if (msg->state->msg == msg)
                        msg->state->msg = NULL;
                msg->state = NULL;
        }
        msg->aux_data = NULL;
        msg->aux_size = 0;
        msg->iocom = NULL;
        kfree(msg, iocom->mmsg);
}

/*
 * Circuits are tracked in a red-black tree by their circuit id (msgid).
 */
int
kdmsg_circuit_cmp(kdmsg_circuit_t *circ1, kdmsg_circuit_t *circ2)
{
        if (circ1->msgid < circ2->msgid)
                return(-1);
        if (circ1->msgid > circ2->msgid)
                return(1);
        return (0);
}

/*
 * Indexed messages are stored in a red-black tree indexed by their
 * msgid.  Only persistent messages are indexed.
 */
int
kdmsg_state_cmp(kdmsg_state_t *state1, kdmsg_state_t *state2)
{
        if (state1->iocom < state2->iocom)
                return(-1);
        if (state1->iocom > state2->iocom)
                return(1);
        if (state1->circ < state2->circ)
                return(-1);
        if (state1->circ > state2->circ)
                return(1);
        if (state1->msgid < state2->msgid)
                return(-1);
        if (state1->msgid > state2->msgid)
                return(1);
        return(0);
}

/*
 * Write a message.  All requisit command flags have been set.
 *
 * If msg->state is non-NULL the message is written to the existing
 * transaction.  msgid will be set accordingly.
 *
 * If msg->state is NULL and CREATE is set new state is allocated and
 * (func, data) is installed.  A msgid is assigned.
 *
 * If msg->state is NULL and CREATE is not set the message is assumed
 * to be a one-way message.  The originator must assign the msgid
 * (or leave it 0, which is typical.
 *
 * This function merely queues the message to the management thread, it
 * does not write to the message socket/pipe.
 */
void
kdmsg_msg_write(kdmsg_msg_t *msg)
{
        kdmsg_iocom_t *iocom = msg->iocom;
        kdmsg_state_t *state;

        if (msg->state) {
                /*
                 * Continuance or termination of existing transaction.
                 * The transaction could have been initiated by either end.
                 *
                 * (Function callback and aux data for the receive side can
                 * be replaced or left alone).
                 */
                state = msg->state;
                msg->any.head.msgid = state->msgid;
                lockmgr(&iocom->msglk, LK_EXCLUSIVE);
        } else {
                /*
                 * One-off message (always uses msgid 0 to distinguish
                 * between a possibly lost in-transaction message due to
                 * competing aborts and a real one-off message?)
                 */
                state = NULL;
                msg->any.head.msgid = 0;
                lockmgr(&iocom->msglk, LK_EXCLUSIVE);
        }

        /*
         * With AUTORXCIRC and AUTOTXCIRC it is possible for the circuit to
         * get ripped out in the rxthread while some other thread is
         * holding a ref on it inbetween allocating and sending a dmsg.
         */
        if (msg->circ && msg->circ->rcirc_state == NULL &&
            (msg->circ->span_state == NULL || msg->circ->circ_state == NULL)) {
                kprintf("kdmsg_msg_write: Attempt to write message to "
                        "terminated circuit: msg %08x\n", msg->any.head.cmd);
                lockmgr(&iocom->msglk, LK_RELEASE);
                if (kdmsg_state_msgtx(msg)) {
                        if (state == NULL || msg != state->msg)
                                kdmsg_msg_free(msg);
                } else if ((msg->state->rxcmd & DMSGF_DELETE) == 0) {
                        /* XXX SMP races simulating a response here */
                        kdmsg_state_t *state = msg->state;
                        kdmsg_state_cleanuptx(msg);
                        kdmsg_state_abort(state);
                } else {
                        kdmsg_state_cleanuptx(msg);
                }
                return;
        }

        /*
         * This flag is not set until after the tx thread has drained
         * the txmsgq and simulated responses.  After that point the
         * txthread is dead and can no longer simulate responses.
         *
         * Device drivers should never try to send a message once this
         * flag is set.  They should have detected (through the state
         * closures) that the link is in trouble.
         */
        if (iocom->flags & KDMSG_IOCOMF_EXITNOACC) {
                lockmgr(&iocom->msglk, LK_RELEASE);
                panic("kdmsg_msg_write: Attempt to write message to "
                      "terminated iocom\n");
        }

        /*
         * Finish up the msg fields.  Note that msg->aux_size and the
         * aux_bytes stored in the message header represent the unaligned
         * (actual) bytes of data, but the buffer is sized to an aligned
         * size and the CRC is generated over the aligned length.
         */
        msg->any.head.salt = /* (random << 8) | */ (iocom->msg_seq & 255);
        ++iocom->msg_seq;

        if (msg->aux_data && msg->aux_size) {
                uint32_t abytes = DMSG_DOALIGN(msg->aux_size);

                msg->any.head.aux_bytes = msg->aux_size;
                msg->any.head.aux_crc = iscsi_crc32(msg->aux_data, abytes);
        }
        msg->any.head.hdr_crc = 0;
        msg->any.head.hdr_crc = iscsi_crc32(msg->any.buf, msg->hdr_size);

        TAILQ_INSERT_TAIL(&iocom->msgq, msg, qentry);

        if (iocom->msg_ctl & KDMSG_CLUSTERCTL_SLEEPING) {
                atomic_clear_int(&iocom->msg_ctl,
                                 KDMSG_CLUSTERCTL_SLEEPING);
                wakeup(&iocom->msg_ctl);
        }

        lockmgr(&iocom->msglk, LK_RELEASE);
}

/*
 * Reply to a message and terminate our side of the transaction.
 *
 * If msg->state is non-NULL we are replying to a one-way message.
 */
void
kdmsg_msg_reply(kdmsg_msg_t *msg, uint32_t error)
{
        kdmsg_state_t *state = msg->state;
        kdmsg_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) {
                if (state->txcmd & DMSGF_DELETE)
                        return;
                if ((state->txcmd & DMSGF_CREATE) == 0)
                        cmd |= DMSGF_CREATE;
                if (state->txcmd & DMSGF_REPLY)
                        cmd |= DMSGF_REPLY;
                cmd |= DMSGF_DELETE;
        } else {
                if ((msg->any.head.cmd & DMSGF_REPLY) == 0)
                        cmd |= DMSGF_REPLY;
        }

        /* XXX messy mask cmd to avoid allocating state */
        nmsg = kdmsg_msg_alloc_state(state, cmd, NULL, NULL);
        nmsg->any.head.error = error;
        kdmsg_msg_write(nmsg);
}

/*
 * Reply to a message and continue our side of the transaction.
 *
 * If msg->state is non-NULL we are replying to a one-way message and this
 * function degenerates into the same as kdmsg_msg_reply().
 */
void
kdmsg_msg_result(kdmsg_msg_t *msg, uint32_t error)
{
        kdmsg_state_t *state = msg->state;
        kdmsg_msg_t *nmsg;
        uint32_t cmd;

        /*
         * Return a simple result code, do NOT 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) {
                if (state->txcmd & DMSGF_DELETE)
                        return;
                if ((state->txcmd & DMSGF_CREATE) == 0)
                        cmd |= DMSGF_CREATE;
                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;
        }

        /* XXX messy mask cmd to avoid allocating state */
        nmsg = kdmsg_msg_alloc_state(state, cmd, NULL, NULL);
        nmsg->any.head.error = error;
        kdmsg_msg_write(nmsg);
}

/*
 * Reply to a message and terminate our side of the transaction.
 *
 * If msg->state is non-NULL we are replying to a one-way message.
 */
void
kdmsg_state_reply(kdmsg_state_t *state, uint32_t error)
{
        kdmsg_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.
         */
        KKASSERT(state);
        if (state->txcmd & DMSGF_DELETE)
                return;
        if ((state->txcmd & DMSGF_CREATE) == 0)
                cmd |= DMSGF_CREATE;
        if (state->txcmd & DMSGF_REPLY)
                cmd |= DMSGF_REPLY;
        cmd |= DMSGF_DELETE;

        /* XXX messy mask cmd to avoid allocating state */
        nmsg = kdmsg_msg_alloc_state(state, cmd, NULL, NULL);
        nmsg->any.head.error = error;
        kdmsg_msg_write(nmsg);
}

/*
 * Reply to a message and continue our side of the transaction.
 *
 * If msg->state is non-NULL we are replying to a one-way message and this
 * function degenerates into the same as kdmsg_msg_reply().
 */
void
kdmsg_state_result(kdmsg_state_t *state, uint32_t error)
{
        kdmsg_msg_t *nmsg;
        uint32_t cmd;

        /*
         * Return a simple result code, do NOT 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.
         */
        KKASSERT(state);
        if (state->txcmd & DMSGF_DELETE)
                return;
        if ((state->txcmd & DMSGF_CREATE) == 0)
                cmd |= DMSGF_CREATE;
        if (state->txcmd & DMSGF_REPLY)
                cmd |= DMSGF_REPLY;
        /* continuing transaction, do not set MSGF_DELETE */

        /* XXX messy mask cmd to avoid allocating state */
        nmsg = kdmsg_msg_alloc_state(state, cmd, NULL, NULL);
        nmsg->any.head.error = error;
        kdmsg_msg_write(nmsg);
}