/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2007-2009 Google Inc. and Amit Singh
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * 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.
 * * Neither the name of Google Inc. 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
 * OWNER 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.
 *
 * Copyright (C) 2005 Csaba Henk.
 * All rights reserved.
 *
 * Copyright (c) 2019 The FreeBSD Foundation
 *
 * Portions of this software were developed by BFF Storage Systems, LLC under
 * sponsorship from the FreeBSD Foundation.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY AUTHOR 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 AUTHOR 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 <sys/param.h>
#include <sys/module.h>
#include <sys/systm.h>
#include <sys/counter.h>
#include <sys/errno.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/uio.h>
#include <sys/malloc.h>
#include <sys/queue.h>
#include <sys/lock.h>
#include <sys/sx.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/sdt.h>
#include <sys/vnode.h>
#include <sys/signalvar.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <vm/uma.h>

#include "fuse.h"
#include "fuse_node.h"
#include "fuse_ipc.h"
#include "fuse_internal.h"

SDT_PROVIDER_DECLARE(fusefs);
/* 
 * Fuse trace probe:
 * arg0: verbosity.  Higher numbers give more verbose messages
 * arg1: Textual message
 */
SDT_PROBE_DEFINE2(fusefs, , ipc, trace, "int", "char*");

static void fdisp_make_pid(struct fuse_dispatcher *fdip, enum fuse_opcode op,
    struct fuse_data *data, uint64_t nid, pid_t pid, struct ucred *cred);
static void fuse_interrupt_send(struct fuse_ticket *otick, int err);
static struct fuse_ticket *fticket_alloc(struct fuse_data *data);
static void fticket_refresh(struct fuse_ticket *ftick);
static inline void fticket_reset(struct fuse_ticket *ftick);
static void fticket_destroy(struct fuse_ticket *ftick);
static int fticket_wait_answer(struct fuse_ticket *ftick);
static inline int 
fticket_aw_pull_uio(struct fuse_ticket *ftick,
    struct uio *uio);

static int fuse_body_audit(struct fuse_ticket *ftick, size_t blen);

static fuse_handler_t fuse_standard_handler;

static counter_u64_t fuse_ticket_count;
SYSCTL_COUNTER_U64(_vfs_fusefs_stats, OID_AUTO, ticket_count, CTLFLAG_RD,
    &fuse_ticket_count, "Number of allocated tickets");

static long fuse_iov_permanent_bufsize = 1 << 19;

SYSCTL_LONG(_vfs_fusefs, OID_AUTO, iov_permanent_bufsize, CTLFLAG_RW,
    &fuse_iov_permanent_bufsize, 0,
    "limit for permanently stored buffer size for fuse_iovs");
static int fuse_iov_credit = 16;

SYSCTL_INT(_vfs_fusefs, OID_AUTO, iov_credit, CTLFLAG_RW,
    &fuse_iov_credit, 0,
    "how many times is an oversized fuse_iov tolerated");

MALLOC_DEFINE(M_FUSEMSG, "fuse_msgbuf", "fuse message buffer");
static uma_zone_t ticket_zone;

/* 
 * TODO: figure out how to timeout INTERRUPT requests, because the daemon may
 * leagally never respond
 */
static int
fuse_interrupt_callback(struct fuse_ticket *tick, struct uio *uio)
{
        struct fuse_ticket *otick, *x_tick;
        struct fuse_interrupt_in *fii;
        struct fuse_data *data = tick->tk_data;
        bool found = false;

        fii = (struct fuse_interrupt_in*)((char*)tick->tk_ms_fiov.base +
                sizeof(struct fuse_in_header));

        fuse_lck_mtx_lock(data->aw_mtx);
        TAILQ_FOREACH_SAFE(otick, &data->aw_head, tk_aw_link, x_tick) {
                if (otick->tk_unique == fii->unique) {
                        found = true;
                        break;
                }
        }
        fuse_lck_mtx_unlock(data->aw_mtx);

        if (!found) {
                /* Original is already complete.  Just return */
                return 0;
        }

        /* Clear the original ticket's interrupt association */
        otick->irq_unique = 0;

        if (tick->tk_aw_ohead.error == ENOSYS) {
                fsess_set_notimpl(data->mp, FUSE_INTERRUPT);
                return 0;
        } else if (tick->tk_aw_ohead.error == EAGAIN) {
                /* 
                 * There are two reasons we might get this:
                 * 1) the daemon received the INTERRUPT request before the
                 *    original, or
                 * 2) the daemon received the INTERRUPT request after it
                 *    completed the original request.
                 * In the first case we should re-send the INTERRUPT.  In the
                 * second, we should ignore it.
                 */
                /* Resend */
                fuse_interrupt_send(otick, EINTR);
                return 0;
        } else {
                /* Illegal FUSE_INTERRUPT response */
                return EINVAL;
        }
}

/* Interrupt the operation otick.  Return err as its error code */
void
fuse_interrupt_send(struct fuse_ticket *otick, int err)
{
        struct fuse_dispatcher fdi;
        struct fuse_interrupt_in *fii;
        struct fuse_in_header *ftick_hdr;
        struct fuse_data *data = otick->tk_data;
        struct fuse_ticket *tick, *xtick;
        struct ucred reused_creds;

        if (otick->irq_unique == 0) {
                /* 
                 * If the daemon hasn't yet received otick, then we can answer
                 * it ourselves and return.
                 */
                fuse_lck_mtx_lock(data->ms_mtx);
                STAILQ_FOREACH_SAFE(tick, &otick->tk_data->ms_head, tk_ms_link,
                        xtick) {
                        if (tick == otick) {
                                STAILQ_REMOVE(&otick->tk_data->ms_head, tick,
                                        fuse_ticket, tk_ms_link);
                                otick->tk_data->ms_count--;
                                otick->tk_ms_link.stqe_next = NULL;
                                fuse_lck_mtx_unlock(data->ms_mtx);

                                fuse_lck_mtx_lock(otick->tk_aw_mtx);
                                if (!fticket_answered(otick)) {
                                        fticket_set_answered(otick);
                                        otick->tk_aw_errno = err;
                                        wakeup(otick);
                                }
                                fuse_lck_mtx_unlock(otick->tk_aw_mtx);

                                fuse_ticket_drop(tick);
                                return;
                        }
                }
                fuse_lck_mtx_unlock(data->ms_mtx);

                /*
                 * If the fuse daemon doesn't support interrupts, then there's
                 * nothing more that we can do
                 */
                if (fsess_not_impl(data->mp, FUSE_INTERRUPT))
                        return;

                /* 
                 * If the fuse daemon has already received otick, then we must
                 * send FUSE_INTERRUPT.
                 */
                ftick_hdr = fticket_in_header(otick);
                reused_creds.cr_uid = ftick_hdr->uid;
                reused_creds.cr_gid = ftick_hdr->gid;
                fdisp_init(&fdi, sizeof(*fii));
                fdisp_make_pid(&fdi, FUSE_INTERRUPT, data, ftick_hdr->nodeid,
                        ftick_hdr->pid, &reused_creds);

                fii = fdi.indata;
                fii->unique = otick->tk_unique;
                fuse_insert_callback(fdi.tick, fuse_interrupt_callback);

                otick->irq_unique = fdi.tick->tk_unique;
                /* Interrupt ops should be delivered ASAP */
                fuse_insert_message(fdi.tick, true);
                fdisp_destroy(&fdi);
        } else {
                /* This ticket has already been interrupted */
        }
}

void
fiov_init(struct fuse_iov *fiov, size_t size)
{
        uint32_t msize = FU_AT_LEAST(size);

        fiov->len = 0;

        fiov->base = malloc(msize, M_FUSEMSG, M_WAITOK | M_ZERO);

        fiov->allocated_size = msize;
        fiov->credit = fuse_iov_credit;
}

void
fiov_teardown(struct fuse_iov *fiov)
{
        MPASS(fiov->base != NULL);
        free(fiov->base, M_FUSEMSG);
}

void
fiov_adjust(struct fuse_iov *fiov, size_t size)
{
        if (fiov->allocated_size < size ||
            (fuse_iov_permanent_bufsize >= 0 &&
            fiov->allocated_size - size > fuse_iov_permanent_bufsize &&
            --fiov->credit < 0)) {
                fiov->base = realloc(fiov->base, FU_AT_LEAST(size), M_FUSEMSG,
                    M_WAITOK | M_ZERO);
                if (!fiov->base) {
                        panic("FUSE: realloc failed");
                }
                fiov->allocated_size = FU_AT_LEAST(size);
                fiov->credit = fuse_iov_credit;
                /* Clear data buffer after reallocation */
                bzero(fiov->base, size);
        } else if (size > fiov->len) {
                /* Clear newly extended portion of data buffer */
                bzero((char*)fiov->base + fiov->len, size - fiov->len);
        }
        fiov->len = size;
}

/* Resize the fiov if needed, and clear it's buffer */
void
fiov_refresh(struct fuse_iov *fiov)
{
        fiov_adjust(fiov, 0);
}

static int
fticket_ctor(void *mem, int size, void *arg, int flags)
{
        struct fuse_ticket *ftick = mem;
        struct fuse_data *data = arg;

        FUSE_ASSERT_MS_DONE(ftick);
        FUSE_ASSERT_AW_DONE(ftick);

        ftick->tk_data = data;
        ftick->irq_unique = 0;
        refcount_init(&ftick->tk_refcount, 1);
        counter_u64_add(fuse_ticket_count, 1);

        fticket_refresh(ftick);

        return 0;
}

static void
fticket_dtor(void *mem, int size, void *arg)
{
#ifdef INVARIANTS
        struct fuse_ticket *ftick = mem;
#endif

        FUSE_ASSERT_MS_DONE(ftick);
        FUSE_ASSERT_AW_DONE(ftick);

        counter_u64_add(fuse_ticket_count, -1);
}

static int
fticket_init(void *mem, int size, int flags)
{
        struct fuse_ticket *ftick = mem;

        bzero(ftick, sizeof(struct fuse_ticket));

        fiov_init(&ftick->tk_ms_fiov, sizeof(struct fuse_in_header));

        mtx_init(&ftick->tk_aw_mtx, "fuse answer delivery mutex", NULL, MTX_DEF);
        fiov_init(&ftick->tk_aw_fiov, 0);

        return 0;
}

static void
fticket_fini(void *mem, int size)
{
        struct fuse_ticket *ftick = mem;

        fiov_teardown(&ftick->tk_ms_fiov);
        fiov_teardown(&ftick->tk_aw_fiov);
        mtx_destroy(&ftick->tk_aw_mtx);
}

static inline struct fuse_ticket *
fticket_alloc(struct fuse_data *data)
{
        return uma_zalloc_arg(ticket_zone, data, M_WAITOK);
}

static inline void
fticket_destroy(struct fuse_ticket *ftick)
{
        return uma_zfree(ticket_zone, ftick);
}

/* Prepare the ticket to be reused and clear its data buffers */
static inline void
fticket_refresh(struct fuse_ticket *ftick)
{
        fticket_reset(ftick);

        fiov_refresh(&ftick->tk_ms_fiov);
        fiov_refresh(&ftick->tk_aw_fiov);
}

/* Prepare the ticket to be reused, but don't clear its data buffers */
static inline void
fticket_reset(struct fuse_ticket *ftick)
{
        struct fuse_data *data = ftick->tk_data;

        FUSE_ASSERT_MS_DONE(ftick);
        FUSE_ASSERT_AW_DONE(ftick);

        bzero(&ftick->tk_aw_ohead, sizeof(struct fuse_out_header));

        ftick->tk_aw_errno = 0;
        ftick->tk_flag = 0;

        /* May be truncated to 32 bits on LP32 arches */
        ftick->tk_unique = atomic_fetchadd_long(&data->ticketer, 1);
        if (ftick->tk_unique == 0)
                ftick->tk_unique = atomic_fetchadd_long(&data->ticketer, 1);
}

static int
fticket_wait_answer(struct fuse_ticket *ftick)
{
        struct thread *td = curthread;
        sigset_t blockedset, oldset;
        int err = 0, stops_deferred;
        struct fuse_data *data = ftick->tk_data;
        bool interrupted = false;

        if (fsess_maybe_impl(ftick->tk_data->mp, FUSE_INTERRUPT) &&
            data->dataflags & FSESS_INTR) {
                SIGEMPTYSET(blockedset);
        } else {
                /* Block all signals except (implicitly) SIGKILL */
                SIGFILLSET(blockedset);
        }
        stops_deferred = sigdeferstop(SIGDEFERSTOP_SILENT);
        kern_sigprocmask(td, SIG_BLOCK, NULL, &oldset, 0);

        fuse_lck_mtx_lock(ftick->tk_aw_mtx);

retry:
        if (fticket_answered(ftick)) {
                goto out;
        }

        if (fdata_get_dead(data)) {
                err = ENOTCONN;
                fticket_set_answered(ftick);
                goto out;
        }
        kern_sigprocmask(td, SIG_BLOCK, &blockedset, NULL, 0);
        err = msleep(ftick, &ftick->tk_aw_mtx, PCATCH, "fu_ans",
            data->daemon_timeout * hz);
        kern_sigprocmask(td, SIG_SETMASK, &oldset, NULL, 0);
        if (err == EWOULDBLOCK) {
                SDT_PROBE2(fusefs, , ipc, trace, 3,
                        "fticket_wait_answer: EWOULDBLOCK");
                err = ETIMEDOUT;
                fticket_set_answered(ftick);
        } else if ((err == EINTR || err == ERESTART)) {
                /*
                 * Whether we get EINTR or ERESTART depends on whether
                 * SA_RESTART was set by sigaction(2).
                 *
                 * Try to interrupt the operation and wait for an EINTR response
                 * to the original operation.  If the file system does not
                 * support FUSE_INTERRUPT, then we'll just wait for it to
                 * complete like normal.  If it does support FUSE_INTERRUPT,
                 * then it will either respond EINTR to the original operation,
                 * or EAGAIN to the interrupt.
                 */
                sigset_t tmpset;

                SDT_PROBE2(fusefs, , ipc, trace, 4,
                        "fticket_wait_answer: interrupt");
                fuse_lck_mtx_unlock(ftick->tk_aw_mtx);
                fuse_interrupt_send(ftick, err);

                PROC_LOCK(td->td_proc);
                mtx_lock(&td->td_proc->p_sigacts->ps_mtx);
                tmpset = td->td_proc->p_siglist;
                SIGSETOR(tmpset, td->td_siglist);
                mtx_unlock(&td->td_proc->p_sigacts->ps_mtx);
                PROC_UNLOCK(td->td_proc);

                fuse_lck_mtx_lock(ftick->tk_aw_mtx);
                if (!interrupted && !SIGISMEMBER(tmpset, SIGKILL)) { 
                        /* 
                         * Block all signals while we wait for an interrupt
                         * response.  The protocol doesn't discriminate between
                         * different signals.
                         */
                        SIGFILLSET(blockedset);
                        interrupted = true;
                        goto retry;
                } else {
                        /*
                         * Return immediately for fatal signals, or if this is
                         * the second interruption.  We should only be
                         * interrupted twice if the thread is stopped, for
                         * example during sigexit.
                         */
                }
        } else if (err) {
                SDT_PROBE2(fusefs, , ipc, trace, 6,
                        "fticket_wait_answer: other error");
        } else {
                SDT_PROBE2(fusefs, , ipc, trace, 7, "fticket_wait_answer: OK");
        }
out:
        if (!(err || fticket_answered(ftick))) {
                SDT_PROBE2(fusefs, , ipc, trace, 1,
                        "FUSE: requester was woken up but still no answer");
                err = ENXIO;
        }
        fuse_lck_mtx_unlock(ftick->tk_aw_mtx);
        sigallowstop(stops_deferred);

        return err;
}

static  inline
int
fticket_aw_pull_uio(struct fuse_ticket *ftick, struct uio *uio)
{
        int err = 0;
        size_t len = uio_resid(uio);

        if (len) {
                fiov_adjust(fticket_resp(ftick), len);
                err = uiomove(fticket_resp(ftick)->base, len, uio);
        }
        return err;
}

int
fticket_pull(struct fuse_ticket *ftick, struct uio *uio)
{
        int err = 0;

        if (ftick->tk_aw_ohead.error) {
                return 0;
        }
        err = fuse_body_audit(ftick, uio_resid(uio));
        if (!err) {
                err = fticket_aw_pull_uio(ftick, uio);
        }
        return err;
}

struct fuse_data *
fdata_alloc(struct cdev *fdev, struct ucred *cred)
{
        struct fuse_data *data;

        data = malloc(sizeof(struct fuse_data), M_FUSEMSG, M_WAITOK | M_ZERO);

        data->fdev = fdev;
        mtx_init(&data->ms_mtx, "fuse message list mutex", NULL, MTX_DEF);
        STAILQ_INIT(&data->ms_head);
        data->ms_count = 0;
        knlist_init_mtx(&data->ks_rsel.si_note, &data->ms_mtx);
        mtx_init(&data->aw_mtx, "fuse answer list mutex", NULL, MTX_DEF);
        TAILQ_INIT(&data->aw_head);
        data->daemoncred = crhold(cred);
        data->daemon_timeout = FUSE_DEFAULT_DAEMON_TIMEOUT;
        data->ref = 1;

        return data;
}

void
fdata_trydestroy(struct fuse_data *data)
{
        data->ref--;
        MPASS(data->ref >= 0);
        if (data->ref != 0)
                return;

        /* Driving off stage all that stuff thrown at device... */
        crfree(data->daemoncred);
        mtx_destroy(&data->aw_mtx);
        knlist_delete(&data->ks_rsel.si_note, curthread, 0);
        knlist_destroy(&data->ks_rsel.si_note);
        mtx_destroy(&data->ms_mtx);

        free(data, M_FUSEMSG);
}

void
fdata_set_dead(struct fuse_data *data)
{
        FUSE_LOCK();
        if (fdata_get_dead(data)) {
                FUSE_UNLOCK();
                return;
        }
        fuse_lck_mtx_lock(data->ms_mtx);
        data->dataflags |= FSESS_DEAD;
        wakeup_one(data);
        selwakeuppri(&data->ks_rsel, PZERO);
        wakeup(&data->ticketer);
        fuse_lck_mtx_unlock(data->ms_mtx);
        FUSE_UNLOCK();
}

struct fuse_ticket *
fuse_ticket_fetch(struct fuse_data *data)
{
        int err = 0;
        struct fuse_ticket *ftick;

        ftick = fticket_alloc(data);

        if (!(data->dataflags & FSESS_INITED)) {
                /* Sleep until get answer for INIT message */
                FUSE_LOCK();
                if (!(data->dataflags & FSESS_INITED) && data->ticketer > 2) {
                        err = msleep(&data->ticketer, &fuse_mtx, PCATCH | PDROP,
                            "fu_ini", 0);
                        if (err)
                                fdata_set_dead(data);
                } else
                        FUSE_UNLOCK();
        }
        return ftick;
}

int
fuse_ticket_drop(struct fuse_ticket *ftick)
{
        int die;

        die = refcount_release(&ftick->tk_refcount);
        if (die)
                fticket_destroy(ftick);

        return die;
}

void
fuse_insert_callback(struct fuse_ticket *ftick, fuse_handler_t * handler)
{
        if (fdata_get_dead(ftick->tk_data)) {
                return;
        }
        ftick->tk_aw_handler = handler;

        fuse_lck_mtx_lock(ftick->tk_data->aw_mtx);
        fuse_aw_push(ftick);
        fuse_lck_mtx_unlock(ftick->tk_data->aw_mtx);
}

/*
 * Insert a new upgoing ticket into the message queue
 *
 * If urgent is true, insert at the front of the queue.  Otherwise, insert in
 * FIFO order.
 */
void
fuse_insert_message(struct fuse_ticket *ftick, bool urgent)
{
        if (ftick->tk_flag & FT_DIRTY) {
                panic("FUSE: ticket reused without being refreshed");
        }
        ftick->tk_flag |= FT_DIRTY;

        if (fdata_get_dead(ftick->tk_data)) {
                return;
        }
        fuse_lck_mtx_lock(ftick->tk_data->ms_mtx);
        if (urgent)
                fuse_ms_push_head(ftick);
        else
                fuse_ms_push(ftick);
        wakeup_one(ftick->tk_data);
        selwakeuppri(&ftick->tk_data->ks_rsel, PZERO);
        KNOTE_LOCKED(&ftick->tk_data->ks_rsel.si_note, 0);
        fuse_lck_mtx_unlock(ftick->tk_data->ms_mtx);
}

static int
fuse_body_audit(struct fuse_ticket *ftick, size_t blen)
{
        int err = 0;
        enum fuse_opcode opcode;

        opcode = fticket_opcode(ftick);

        switch (opcode) {
        case FUSE_BMAP:
                err = (blen == sizeof(struct fuse_bmap_out)) ? 0 : EINVAL;
                break;

        case FUSE_LINK:
        case FUSE_LOOKUP:
        case FUSE_MKDIR:
        case FUSE_MKNOD:
        case FUSE_SYMLINK:
                if (fuse_libabi_geq(ftick->tk_data, 7, 9)) {
                        err = (blen == sizeof(struct fuse_entry_out)) ?
                                0 : EINVAL;
                } else {
                        err = (blen == FUSE_COMPAT_ENTRY_OUT_SIZE) ? 0 : EINVAL;
                }
                break;

        case FUSE_FORGET:
                panic("FUSE: a handler has been installed for FUSE_FORGET");
                break;

        case FUSE_GETATTR:
        case FUSE_SETATTR:
                if (fuse_libabi_geq(ftick->tk_data, 7, 9)) {
                        err = (blen == sizeof(struct fuse_attr_out)) ? 
                          0 : EINVAL;
                } else {
                        err = (blen == FUSE_COMPAT_ATTR_OUT_SIZE) ? 0 : EINVAL;
                }
                break;

        case FUSE_READLINK:
                err = (PAGE_SIZE >= blen) ? 0 : EINVAL;
                break;

        case FUSE_UNLINK:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_RMDIR:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_RENAME:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_OPEN:
                err = (blen == sizeof(struct fuse_open_out)) ? 0 : EINVAL;
                break;

        case FUSE_READ:
                err = (((struct fuse_read_in *)(
                    (char *)ftick->tk_ms_fiov.base +
                    sizeof(struct fuse_in_header)
                    ))->size >= blen) ? 0 : EINVAL;
                break;

        case FUSE_WRITE:
                err = (blen == sizeof(struct fuse_write_out)) ? 0 : EINVAL;
                break;

        case FUSE_STATFS:
                if (fuse_libabi_geq(ftick->tk_data, 7, 4)) {
                        err = (blen == sizeof(struct fuse_statfs_out)) ? 
                          0 : EINVAL;
                } else {
                        err = (blen == FUSE_COMPAT_STATFS_SIZE) ? 0 : EINVAL;
                }
                break;

        case FUSE_RELEASE:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_FSYNC:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_SETXATTR:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_GETXATTR:
        case FUSE_LISTXATTR:
                /*
                 * These can have varying response lengths, and 0 length
                 * isn't necessarily invalid.
                 */
                err = 0;
                break;

        case FUSE_REMOVEXATTR:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_FLUSH:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_INIT:
                if (blen == sizeof(struct fuse_init_out) ||
                    blen == FUSE_COMPAT_INIT_OUT_SIZE ||
                    blen == FUSE_COMPAT_22_INIT_OUT_SIZE) {
                        err = 0;
                } else {
                        err = EINVAL;
                }
                break;

        case FUSE_OPENDIR:
                err = (blen == sizeof(struct fuse_open_out)) ? 0 : EINVAL;
                break;

        case FUSE_READDIR:
                err = (((struct fuse_read_in *)(
                    (char *)ftick->tk_ms_fiov.base +
                    sizeof(struct fuse_in_header)
                    ))->size >= blen) ? 0 : EINVAL;
                break;

        case FUSE_RELEASEDIR:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_FSYNCDIR:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_GETLK:
                err = (blen == sizeof(struct fuse_lk_out)) ? 0 : EINVAL;
                break;

        case FUSE_SETLK:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_SETLKW:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_ACCESS:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_CREATE:
                if (fuse_libabi_geq(ftick->tk_data, 7, 9)) {
                        err = (blen == sizeof(struct fuse_entry_out) +
                            sizeof(struct fuse_open_out)) ? 0 : EINVAL;
                } else {
                        err = (blen == FUSE_COMPAT_ENTRY_OUT_SIZE +
                            sizeof(struct fuse_open_out)) ? 0 : EINVAL;
                }
                break;

        case FUSE_DESTROY:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_IOCTL:
                err = (blen >= sizeof(struct fuse_ioctl_out)) ? 0 : EINVAL;
                break;

        case FUSE_FALLOCATE:
                err = (blen == 0) ? 0 : EINVAL;
                break;

        case FUSE_LSEEK:
                err = (blen == sizeof(struct fuse_lseek_out)) ? 0 : EINVAL;
                break;

        case FUSE_COPY_FILE_RANGE:
                err = (blen == sizeof(struct fuse_write_out)) ? 0 : EINVAL;
                break;

        default:
                panic("FUSE: opcodes out of sync (%d)\n", opcode);
        }

        return err;
}

static inline void
fuse_setup_ihead(struct fuse_in_header *ihead, struct fuse_ticket *ftick,
    uint64_t nid, enum fuse_opcode op, size_t blen, pid_t pid,
    struct ucred *cred)
{
        ihead->len = sizeof(*ihead) + blen;
        ihead->unique = ftick->tk_unique;
        ihead->nodeid = nid;
        ihead->opcode = op;

        ihead->pid = pid;
        ihead->uid = cred->cr_uid;
        ihead->gid = cred->cr_gid;
}

/*
 * fuse_standard_handler just pulls indata and wakes up pretender.
 * Doesn't try to interpret data, that's left for the pretender.
 * Though might do a basic size verification before the pull-in takes place
 */

static int
fuse_standard_handler(struct fuse_ticket *ftick, struct uio *uio)
{
        int err = 0;

        err = fticket_pull(ftick, uio);

        fuse_lck_mtx_lock(ftick->tk_aw_mtx);

        if (!fticket_answered(ftick)) {
                fticket_set_answered(ftick);
                ftick->tk_aw_errno = err;
                wakeup(ftick);
        }
        fuse_lck_mtx_unlock(ftick->tk_aw_mtx);

        return err;
}

/*
 * Reinitialize a dispatcher from a pid and node id, without resizing or
 * clearing its data buffers
 */
static void
fdisp_refresh_pid(struct fuse_dispatcher *fdip, enum fuse_opcode op,
    struct mount *mp, uint64_t nid, pid_t pid, struct ucred *cred)
{
        MPASS(fdip->tick);
        MPASS2(sizeof(fdip->finh) + fdip->iosize <= fdip->tick->tk_ms_fiov.len,
                "Must use fdisp_make_pid to increase the size of the fiov");
        fticket_reset(fdip->tick);

        FUSE_DIMALLOC(&fdip->tick->tk_ms_fiov, fdip->finh,
            fdip->indata, fdip->iosize);

        fuse_setup_ihead(fdip->finh, fdip->tick, nid, op, fdip->iosize, pid,
                cred);
}

/* Initialize a dispatcher from a pid and node id */
static void
fdisp_make_pid(struct fuse_dispatcher *fdip, enum fuse_opcode op,
    struct fuse_data *data, uint64_t nid, pid_t pid, struct ucred *cred)
{
        if (fdip->tick) {
                fticket_refresh(fdip->tick);
        } else {
                fdip->tick = fuse_ticket_fetch(data);
        }

        /* FUSE_DIMALLOC will bzero the fiovs when it enlarges them */
        FUSE_DIMALLOC(&fdip->tick->tk_ms_fiov, fdip->finh,
            fdip->indata, fdip->iosize);

        fuse_setup_ihead(fdip->finh, fdip->tick, nid, op, fdip->iosize, pid, cred);
}

void
fdisp_make(struct fuse_dispatcher *fdip, enum fuse_opcode op, struct mount *mp,
    uint64_t nid, struct thread *td, struct ucred *cred)
{
        struct fuse_data *data = fuse_get_mpdata(mp);
        RECTIFY_TDCR(td, cred);

        return fdisp_make_pid(fdip, op, data, nid, td->td_proc->p_pid, cred);
}

void
fdisp_make_vp(struct fuse_dispatcher *fdip, enum fuse_opcode op,
    struct vnode *vp, struct thread *td, struct ucred *cred)
{
        struct mount *mp = vnode_mount(vp);
        struct fuse_data *data = fuse_get_mpdata(mp);

        RECTIFY_TDCR(td, cred);
        return fdisp_make_pid(fdip, op, data, VTOI(vp),
            td->td_proc->p_pid, cred);
}

/* Refresh a fuse_dispatcher so it can be reused, but don't zero its data */
void
fdisp_refresh_vp(struct fuse_dispatcher *fdip, enum fuse_opcode op,
    struct vnode *vp, struct thread *td, struct ucred *cred)
{
        RECTIFY_TDCR(td, cred);
        return fdisp_refresh_pid(fdip, op, vnode_mount(vp), VTOI(vp),
            td->td_proc->p_pid, cred);
}

SDT_PROBE_DEFINE2(fusefs, , ipc, fdisp_wait_answ_error, "char*", "int");

int
fdisp_wait_answ(struct fuse_dispatcher *fdip)
{
        int err = 0;

        fdip->answ_stat = 0;
        fuse_insert_callback(fdip->tick, fuse_standard_handler);
        fuse_insert_message(fdip->tick, false);

        if ((err = fticket_wait_answer(fdip->tick))) {
                fuse_lck_mtx_lock(fdip->tick->tk_aw_mtx);

                if (fticket_answered(fdip->tick)) {
                        /*
                         * Just between noticing the interrupt and getting here,
                         * the standard handler has completed his job.
                         * So we drop the ticket and exit as usual.
                         */
                        SDT_PROBE2(fusefs, , ipc, fdisp_wait_answ_error,
                                "IPC: interrupted, already answered", err);
                        fuse_lck_mtx_unlock(fdip->tick->tk_aw_mtx);
                        goto out;
                } else {
                        /*
                         * So we were faster than the standard handler.
                         * Then by setting the answered flag we get *him*
                         * to drop the ticket.
                         */
                        SDT_PROBE2(fusefs, , ipc, fdisp_wait_answ_error,
                                "IPC: interrupted, setting to answered", err);
                        fticket_set_answered(fdip->tick);
                        fuse_lck_mtx_unlock(fdip->tick->tk_aw_mtx);
                        return err;
                }
        }

        if (fdip->tick->tk_aw_errno == ENOTCONN) {
                /* The daemon died while we were waiting for a response */
                err = ENOTCONN;
                goto out;
        } else if (fdip->tick->tk_aw_errno) {
                /* 
                 * There was some sort of communication error with the daemon
                 * that the client wouldn't understand.
                 */
                SDT_PROBE2(fusefs, , ipc, fdisp_wait_answ_error,
                        "IPC: explicit EIO-ing", fdip->tick->tk_aw_errno);
                err = EIO;
                goto out;
        }
        if ((err = fdip->tick->tk_aw_ohead.error)) {
                SDT_PROBE2(fusefs, , ipc, fdisp_wait_answ_error,
                        "IPC: setting status", fdip->tick->tk_aw_ohead.error);
                /*
                 * This means a "proper" fuse syscall error.
                 * We record this value so the caller will
                 * be able to know it's not a boring messaging
                 * failure, if she wishes so (and if not, she can
                 * just simply propagate the return value of this routine).
                 * [XXX Maybe a bitflag would do the job too,
                 * if other flags needed, this will be converted thusly.]
                 */
                fdip->answ_stat = err;
                goto out;
        }
        fdip->answ = fticket_resp(fdip->tick)->base;
        fdip->iosize = fticket_resp(fdip->tick)->len;

        return 0;

out:
        return err;
}

void
fuse_ipc_init(void)
{
        ticket_zone = uma_zcreate("fuse_ticket", sizeof(struct fuse_ticket),
            fticket_ctor, fticket_dtor, fticket_init, fticket_fini,
            UMA_ALIGN_PTR, 0);
        fuse_ticket_count = counter_u64_alloc(M_WAITOK);
}

void
fuse_ipc_destroy(void)
{
        counter_u64_free(fuse_ticket_count);
        uma_zdestroy(ticket_zone);
}

SDT_PROBE_DEFINE3(fusefs,, ipc, warn, "struct fuse_data*", "unsigned", "char*");
void
fuse_warn(struct fuse_data *data, unsigned flag, const char *msg)
{
        SDT_PROBE3(fusefs, , ipc, warn, data, flag, msg);
        if (!(data->dataflags & flag)) {
                printf("WARNING: FUSE protocol violation for server mounted at "
                    "%s: %s  "
                    "This warning will not be repeated.\n",
                    data->mp->mnt_stat.f_mntonname, msg);
                data->dataflags |= flag;
        }
}