xref: /freebsd/sys/fs/fuse/fuse_ipc.c (revision 723c7768299a077a93f19b26e8c27b4641751e34)

/*-
 * 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.
 *
 * 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/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/module.h>
#include <sys/systm.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(fuse);
/*
 * Fuse trace probe:
 * arg0: verbosity.  Higher numbers give more verbose messages
 * arg1: Textual message
 */
SDT_PROBE_DEFINE2(fuse, , 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 fiov_clear(struct fuse_iov *fiov);
static void fuse_interrupt_send(struct fuse_ticket *otick);
static struct fuse_ticket *fticket_alloc(struct fuse_data *data);
static void fticket_refresh(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;

SYSCTL_NODE(_vfs, OID_AUTO, fusefs, CTLFLAG_RW, 0, "FUSE tunables");
SYSCTL_STRING(_vfs_fusefs, OID_AUTO, version, CTLFLAG_RD,
    FUSE_FREEBSD_VERSION, 0, "fuse-freebsd version");
static int fuse_ticket_count = 0;

SYSCTL_INT(_vfs_fusefs, OID_AUTO, ticket_count, CTLFLAG_RW,
    &fuse_ticket_count, 0, "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
 *
 * TODO: remove an INTERRUPT request if the daemon responds to the original
 */
static int
fuse_interrupt_callback(struct fuse_ticket *tick, struct uio *uio)
{
	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.
		 */
		struct fuse_interrupt_in *fii;
		struct fuse_data *data;
		struct fuse_ticket *otick, *x_tick;
		bool found = false;

		data = tick->tk_data;
		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) {
			/* Resend */
			fuse_interrupt_send(otick);
		} else {
			/* Original is already complete; nothing to do */
		}
		return 0;
	} else {
		/* Illegal FUSE_INTERRUPT response */
		return EINVAL;
	}
}

void
fuse_interrupt_send(struct fuse_ticket *otick)
{
	struct fuse_dispatcher fdi;
	struct fuse_interrupt_in *fii;
	struct fuse_in_header *ftick_hdr;
	struct fuse_data *data = otick->tk_data;
	struct ucred reused_creds;

	ftick_hdr = fticket_in_header(otick);
	reused_creds.cr_uid = ftick_hdr->uid;
	reused_creds.cr_rgid = 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);

	fuse_insert_message(fdi.tick);
	fdisp_destroy(&fdi);
}

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;
}

/* Clear the fiov's data buffer */
static void
fiov_clear(struct fuse_iov *fiov)
{
	bzero(fiov->base, fiov->len);
}

/* 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;

	if (ftick->tk_unique != 0)
		fticket_refresh(ftick);

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

	refcount_init(&ftick->tk_refcount, 1);
	atomic_add_acq_int(&fuse_ticket_count, 1);

	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);

	atomic_subtract_acq_int(&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));
	ftick->tk_ms_type = FT_M_FIOV;

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

	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);
}

static inline
void
fticket_refresh(struct fuse_ticket *ftick)
{
	FUSE_ASSERT_MS_DONE(ftick);
	FUSE_ASSERT_AW_DONE(ftick);

	fiov_refresh(&ftick->tk_ms_fiov);
	ftick->tk_ms_bufdata = NULL;
	ftick->tk_ms_bufsize = 0;
	ftick->tk_ms_type = FT_M_FIOV;

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

	fiov_refresh(&ftick->tk_aw_fiov);
	ftick->tk_aw_errno = 0;
	ftick->tk_aw_bufdata = NULL;
	ftick->tk_aw_bufsize = 0;
	ftick->tk_aw_type = FT_A_FIOV;

	ftick->tk_flag = 0;
}

/* Prepar the ticket to be reused, but don't clear its data buffers */
static inline void
fticket_reset(struct fuse_ticket *ftick)
{
	FUSE_ASSERT_MS_DONE(ftick);
	FUSE_ASSERT_AW_DONE(ftick);

	ftick->tk_ms_bufdata = NULL;
	ftick->tk_ms_bufsize = 0;
	ftick->tk_ms_type = FT_M_FIOV;

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

	ftick->tk_aw_errno = 0;
	ftick->tk_aw_bufdata = NULL;
	ftick->tk_aw_bufsize = 0;
	ftick->tk_aw_type = FT_A_FIOV;

	ftick->tk_flag = 0;
}

static int
fticket_wait_answer(struct fuse_ticket *ftick)
{
	struct thread *td = curthread;
	sigset_t blockedset, oldset;
	int err = 0;
	struct fuse_data *data;

	fuse_lck_mtx_lock(ftick->tk_aw_mtx);

	SIGEMPTYSET(blockedset);
	kern_sigprocmask(td, SIG_BLOCK, &blockedset, &oldset, 0);
retry:
	if (fticket_answered(ftick)) {
		goto out;
	}
	data = ftick->tk_data;

	if (fdata_get_dead(data)) {
		err = ENOTCONN;
		fticket_set_answered(ftick);
		goto out;
	}
	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(fuse, , ipc, trace, 3,
			"fticket_wait_answer: EWOULDBLOCK");
#ifdef XXXIP				/* die conditionally */
		if (!fdata_get_dead(data)) {
			fdata_set_dead(data);
		}
#endif
		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.
		 */
		int sig;

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

		/* TODO: return, rather than retry, for fatal signals */

		/*
		 * Block the just-delivered signal while we wait for an
		 * interrupt response
		 */
		PROC_LOCK(td->td_proc);
		mtx_lock(&td->td_proc->p_sigacts->ps_mtx);
		sig = cursig(td);
		mtx_unlock(&td->td_proc->p_sigacts->ps_mtx);
		PROC_UNLOCK(td->td_proc);
		SIGADDSET(blockedset, sig);
		kern_sigprocmask(curthread, SIG_BLOCK, &blockedset, NULL, 0);
		goto retry;
	} else if (err) {
		SDT_PROBE2(fuse, , ipc, trace, 6,
			"fticket_wait_answer: other error");
	} else {
		SDT_PROBE2(fuse, , ipc, trace, 7, "fticket_wait_answer: OK");
	}
out:
	if (!(err || fticket_answered(ftick))) {
		SDT_PROBE2(fuse, , ipc, trace, 1,
			"FUSE: requester was woken up but still no answer");
		err = ENXIO;
	}
	fuse_lck_mtx_unlock(ftick->tk_aw_mtx);

	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) {
		switch (ftick->tk_aw_type) {
		case FT_A_FIOV:
			fiov_adjust(fticket_resp(ftick), len);
			err = uiomove(fticket_resp(ftick)->base, len, uio);
			break;

		case FT_A_BUF:
			ftick->tk_aw_bufsize = len;
			err = uiomove(ftick->tk_aw_bufdata, len, uio);
			break;

		default:
			panic("FUSE: unknown answer type for ticket %p", ftick);
		}
	}
	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);
	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;
	sx_init(&data->rename_lock, "fuse rename lock");
	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... */
	mtx_destroy(&data->ms_mtx);
	mtx_destroy(&data->aw_mtx);
	sx_destroy(&data->rename_lock);

	crfree(data->daemoncred);

	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 + 1);
	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 messsage */
		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);
}

void
fuse_insert_message(struct fuse_ticket *ftick)
{
	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);
	fuse_ms_push(ftick);
	wakeup_one(ftick->tk_data);
	selwakeuppri(&ftick->tk_data->ks_rsel, PZERO + 1);
	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_LOOKUP:
		err = (blen == sizeof(struct fuse_entry_out)) ? 0 : EINVAL;
		break;

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

	case FUSE_GETATTR:
		err = (blen == sizeof(struct fuse_attr_out)) ? 0 : EINVAL;
		break;

	case FUSE_SETATTR:
		err = (blen == sizeof(struct fuse_attr_out)) ? 0 : EINVAL;
		break;

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

	case FUSE_SYMLINK:
		err = (blen == sizeof(struct fuse_entry_out)) ? 0 : EINVAL;
		break;

	case FUSE_MKNOD:
		err = (blen == sizeof(struct fuse_entry_out)) ? 0 : EINVAL;
		break;

	case FUSE_MKDIR:
		err = (blen == sizeof(struct fuse_entry_out)) ? 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_LINK:
		err = (blen == sizeof(struct fuse_entry_out)) ? 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 == 8) {
			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:
		err = (blen == sizeof(struct fuse_entry_out) +
		    sizeof(struct fuse_open_out)) ? 0 : EINVAL;
		break;

	case FUSE_DESTROY:
		err = (blen == 0) ? 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_rgid;
}

/*
 * 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);
}

void
fdisp_refresh(struct fuse_dispatcher *fdip)
{
	fticket_refresh(fdip->tick);
}

SDT_PROBE_DEFINE2(fuse, , 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);

	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(fuse, , 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(fuse, , 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) {
		SDT_PROBE2(fuse, , 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(fuse, , 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);
}

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