/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2011 NetApp, Inc.
 * 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 NETAPP, INC ``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 NETAPP, INC 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 2018 Joyent, Inc.
 * Copyright 2022 OmniOS Community Edition (OmniOSce) Association.
 */

/*
 * Micro event library for FreeBSD, designed for a single i/o thread
 * using kqueue, and having events be persistent by default.
 */


#include <assert.h>
#ifndef WITHOUT_CAPSICUM
#include <capsicum_helpers.h>
#endif
#include <err.h>
#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>

#include <sys/types.h>
#ifndef WITHOUT_CAPSICUM
#include <sys/capsicum.h>
#endif
#ifdef __FreeBSD__
#include <sys/event.h>
#else
#include <port.h>
#include <sys/poll.h>
#include <sys/siginfo.h>
#include <sys/queue.h>
#include <sys/debug.h>
#include <sys/stat.h>
#endif
#include <sys/time.h>

#include <pthread.h>
#include <pthread_np.h>

#include "mevent.h"

#define MEVENT_MAX      64

#ifndef __FreeBSD__
#define EV_ENABLE       0x01
#define EV_ADD          EV_ENABLE
#define EV_DISABLE      0x02
#define EV_DELETE       0x04

static int mevent_file_poll_interval_ms = 5000;
#endif

static pthread_t mevent_tid;
static pthread_once_t mevent_once = PTHREAD_ONCE_INIT;
#ifdef __FreeBSD__
static int mevent_timid = 43;
#endif
static int mevent_pipefd[2];
static int mfd;
static pthread_mutex_t mevent_lmutex = PTHREAD_MUTEX_INITIALIZER;

struct mevent {
        void    (*me_func)(int, enum ev_type, void *);
#define me_msecs me_fd
        int     me_fd;
#ifdef __FreeBSD__
        int     me_timid;
#else
        timer_t me_timid;
#endif
        enum ev_type me_type;
        void    *me_param;
        int     me_cq;
        int     me_state; /* Desired kevent flags. */
        int     me_closefd;
        int     me_fflags;
#ifndef __FreeBSD__
        port_notify_t   me_notify;
        struct sigevent me_sigev;
        boolean_t       me_auto_requeue;
        struct {
                int     mp_fd;
                off_t   mp_size;
                void    (*mp_func)(int, enum ev_type, void *);
                void    *mp_param;
        } me_poll;
#endif
        LIST_ENTRY(mevent) me_list;
};

static LIST_HEAD(listhead, mevent) global_head, change_head;

static void
mevent_qlock(void)
{
        pthread_mutex_lock(&mevent_lmutex);
}

static void
mevent_qunlock(void)
{
        pthread_mutex_unlock(&mevent_lmutex);
}

static void
mevent_pipe_read(int fd, enum ev_type type __unused, void *param __unused)
{
        char buf[MEVENT_MAX];
        int status;

        /*
         * Drain the pipe read side. The fd is non-blocking so this is
         * safe to do.
         */
        do {
                status = read(fd, buf, sizeof(buf));
        } while (status == MEVENT_MAX);
}

static void
mevent_notify(void)
{
        char c = '\0';

        /*
         * If calling from outside the i/o thread, write a byte on the
         * pipe to force the i/o thread to exit the blocking kevent call.
         */
        if (mevent_pipefd[1] != 0 && pthread_self() != mevent_tid) {
                write(mevent_pipefd[1], &c, 1);
        }
}

static void
mevent_init(void)
{
#ifndef WITHOUT_CAPSICUM
        cap_rights_t rights;
#endif

#ifdef __FreeBSD__
        mfd = kqueue();
#else
        mfd = port_create();
#endif
        assert(mfd > 0);

#ifndef WITHOUT_CAPSICUM
        cap_rights_init(&rights, CAP_KQUEUE);
        if (caph_rights_limit(mfd, &rights) == -1)
                errx(EX_OSERR, "Unable to apply rights for sandbox");
#endif

        LIST_INIT(&change_head);
        LIST_INIT(&global_head);
}


#ifdef __FreeBSD__
static int
mevent_kq_filter(struct mevent *mevp)
{
        int retval;

        retval = 0;

        if (mevp->me_type == EVF_READ)
                retval = EVFILT_READ;

        if (mevp->me_type == EVF_WRITE)
                retval = EVFILT_WRITE;

        if (mevp->me_type == EVF_TIMER)
                retval = EVFILT_TIMER;

        if (mevp->me_type == EVF_SIGNAL)
                retval = EVFILT_SIGNAL;

        if (mevp->me_type == EVF_VNODE)
                retval = EVFILT_VNODE;

        return (retval);
}

static int
mevent_kq_flags(struct mevent *mevp)
{
        int retval;

        retval = mevp->me_state;

        if (mevp->me_type == EVF_VNODE)
                retval |= EV_CLEAR;

        return (retval);
}

static int
mevent_kq_fflags(struct mevent *mevp)
{
        int retval;

        retval = 0;

        switch (mevp->me_type) {
        case EVF_VNODE:
                if ((mevp->me_fflags & EVFF_ATTRIB) != 0)
                        retval |= NOTE_ATTRIB;
                break;
        case EVF_READ:
        case EVF_WRITE:
        case EVF_TIMER:
        case EVF_SIGNAL:
                break;
        }

        return (retval);
}

static void
mevent_populate(struct mevent *mevp, struct kevent *kev)
{
        if (mevp->me_type == EVF_TIMER) {
                kev->ident = mevp->me_timid;
                kev->data = mevp->me_msecs;
        } else {
                kev->ident = mevp->me_fd;
                kev->data = 0;
        }
        kev->filter = mevent_kq_filter(mevp);
        kev->flags = mevent_kq_flags(mevp);
        kev->fflags = mevent_kq_fflags(mevp);
        kev->udata = mevp;
}

static int
mevent_build(struct kevent *kev)
{
        struct mevent *mevp, *tmpp;
        int i;

        i = 0;

        mevent_qlock();

        LIST_FOREACH_SAFE(mevp, &change_head, me_list, tmpp) {
                if (mevp->me_closefd) {
                        /*
                         * A close of the file descriptor will remove the
                         * event
                         */
                        close(mevp->me_fd);
                } else {
                        assert((mevp->me_state & EV_ADD) == 0);
                        mevent_populate(mevp, &kev[i]);
                        i++;
                }

                mevp->me_cq = 0;
                LIST_REMOVE(mevp, me_list);

                if (mevp->me_state & EV_DELETE) {
                        free(mevp);
                } else {
                        LIST_INSERT_HEAD(&global_head, mevp, me_list);
                }

                assert(i < MEVENT_MAX);
        }

        mevent_qunlock();

        return (i);
}

static void
mevent_handle(struct kevent *kev, int numev)
{
        struct mevent *mevp;
        int i;

        for (i = 0; i < numev; i++) {
                mevp = kev[i].udata;

                /* XXX check for EV_ERROR ? */

                (*mevp->me_func)(mevp->me_fd, mevp->me_type, mevp->me_param);
        }
}

#else /* __FreeBSD__ */

static boolean_t
mevent_clarify_state(struct mevent *mevp)
{
        const int state = mevp->me_state;

        if ((state & EV_DELETE) != 0) {
                /* All other intents are overriden by delete. */
                mevp->me_state = EV_DELETE;
                return (B_TRUE);
        }

        /*
         * Without a distinction between EV_ADD and EV_ENABLE in our emulation,
         * handling the add-disabled case means eliding the portfs operation
         * when both flags are present.
         *
         * This is not a concern for subsequent enable/disable operations, as
         * mevent_update() toggles the flags properly so they are not left in
         * conflict.
         */
        if (state == (EV_ENABLE|EV_DISABLE)) {
                mevp->me_state = EV_DISABLE;
                return (B_FALSE);
        }

        return (B_TRUE);
}

static void
mevent_poll_file_attrib(int fd, enum ev_type type, void *param)
{
        struct mevent *mevp = param;
        struct stat st;

        if (fstat(mevp->me_poll.mp_fd, &st) != 0) {
                (void) fprintf(stderr, "%s: fstat(%d) failed: %s\n",
                    __func__, fd, strerror(errno));
                return;
        }

        /*
         * The only current consumer of file attribute monitoring is
         * blockif, which wants to know about size changes.
         */
        if (mevp->me_poll.mp_size != st.st_size) {
                mevp->me_poll.mp_size = st.st_size;

                (*mevp->me_poll.mp_func)(mevp->me_poll.mp_fd, EVF_VNODE,
                    mevp->me_poll.mp_param);
        }
}

static void
mevent_update_one_readwrite(struct mevent *mevp)
{
        int portfd = mevp->me_notify.portnfy_port;

        mevp->me_auto_requeue = B_FALSE;

        switch (mevp->me_state) {
        case EV_ENABLE:
        {
                const int events = (mevp->me_type == EVF_READ) ?
                    POLLIN : POLLOUT;

                if (port_associate(portfd, PORT_SOURCE_FD, mevp->me_fd,
                    events, mevp) != 0) {
                        (void) fprintf(stderr,
                            "port_associate fd %d %p failed: %s\n",
                            mevp->me_fd, mevp, strerror(errno));
                }
                return;
        }
        case EV_DISABLE:
        case EV_DELETE:
                /*
                 * A disable that comes in while an event is being
                 * handled will result in an ENOENT.
                 */
                if (port_dissociate(portfd, PORT_SOURCE_FD,
                    mevp->me_fd) != 0 && errno != ENOENT) {
                        (void) fprintf(stderr, "port_dissociate "
                            "portfd %d fd %d mevp %p failed: %s\n",
                            portfd, mevp->me_fd, mevp, strerror(errno));
                }
                return;
        default:
                (void) fprintf(stderr, "%s: unhandled state %d\n", __func__,
                    mevp->me_state);
                abort();
        }
}

static void
mevent_update_one_timer(struct mevent *mevp)
{
        mevp->me_auto_requeue = B_TRUE;

        switch (mevp->me_state) {
        case EV_ENABLE:
        {
                struct itimerspec it = { 0 };

                mevp->me_sigev.sigev_notify = SIGEV_PORT;
                mevp->me_sigev.sigev_value.sival_ptr = &mevp->me_notify;

                if (timer_create(CLOCK_REALTIME, &mevp->me_sigev,
                    &mevp->me_timid) != 0) {
                        (void) fprintf(stderr, "timer_create failed: %s",
                            strerror(errno));
                        return;
                }

                /* The first timeout */
                it.it_value.tv_sec = mevp->me_msecs / MILLISEC;
                it.it_value.tv_nsec =
                        MSEC2NSEC(mevp->me_msecs % MILLISEC);
                /* Repeat at the same interval */
                it.it_interval = it.it_value;

                if (timer_settime(mevp->me_timid, 0, &it, NULL) != 0) {
                        (void) fprintf(stderr, "timer_settime failed: %s",
                            strerror(errno));
                }
                return;
        }
        case EV_DISABLE:
        case EV_DELETE:
                if (timer_delete(mevp->me_timid) != 0) {
                        (void) fprintf(stderr, "timer_delete failed: %s",
                            strerror(errno));
                }
                mevp->me_timid = -1;
                return;
        default:
                (void) fprintf(stderr, "%s: unhandled state %d\n", __func__,
                    mevp->me_state);
                abort();
        }
}

static void
mevent_update_one_vnode(struct mevent *mevp)
{
        switch (mevp->me_state) {
        case EV_ENABLE:
        {
                struct stat st;
                int events = 0;

                if ((mevp->me_fflags & EVFF_ATTRIB) != 0)
                        events |= FILE_ATTRIB;

                assert(events != 0);

                /*
                 * It is tempting to use the PORT_SOURCE_FILE type for this in
                 * conjunction with the FILE_ATTRIB event type. Unfortunately
                 * this event type triggers on any change to the file's
                 * ctime, and therefore for every write as well as attribute
                 * changes. It also does not work for ZVOLs.
                 *
                 * Convert this to a timer event and poll for the file
                 * attribute changes that we care about.
                 */

                if (fstat(mevp->me_fd, &st) != 0) {
                        (void) fprintf(stderr, "fstat(%d) failed: %s\n",
                            mevp->me_fd, strerror(errno));
                        return;
                }

                mevp->me_poll.mp_fd = mevp->me_fd;
                mevp->me_poll.mp_size = st.st_size;

                mevp->me_poll.mp_func = mevp->me_func;
                mevp->me_poll.mp_param = mevp->me_param;
                mevp->me_func = mevent_poll_file_attrib;
                mevp->me_param = mevp;

                mevp->me_type = EVF_TIMER;
                mevp->me_timid = -1;
                mevp->me_msecs = mevent_file_poll_interval_ms;
                mevent_update_one_timer(mevp);

                return;
        }
        case EV_DISABLE:
        case EV_DELETE:
                /*
                 * These events do not really exist as they are converted to
                 * timers; fall through to abort.
                 */
        default:
                (void) fprintf(stderr, "%s: unhandled state %d\n", __func__,
                    mevp->me_state);
                abort();
        }
}

static void
mevent_update_one(struct mevent *mevp)
{
        switch (mevp->me_type) {
        case EVF_READ:
        case EVF_WRITE:
                mevent_update_one_readwrite(mevp);
                break;
        case EVF_TIMER:
                mevent_update_one_timer(mevp);
                break;
        case EVF_VNODE:
                mevent_update_one_vnode(mevp);
                break;
        case EVF_SIGNAL: /* EVF_SIGNAL not yet implemented. */
        default:
                (void) fprintf(stderr, "%s: unhandled event type %d\n",
                    __func__, mevp->me_type);
                abort();
        }
}

static void
mevent_populate(struct mevent *mevp)
{
        mevp->me_notify.portnfy_port = mfd;
        mevp->me_notify.portnfy_user = mevp;
}

static void
mevent_update_pending()
{
        struct mevent *mevp, *tmpp;

        mevent_qlock();

        LIST_FOREACH_SAFE(mevp, &change_head, me_list, tmpp) {
                mevent_populate(mevp);
                if (mevp->me_closefd) {
                        /*
                         * A close of the file descriptor will remove the
                         * event
                         */
                        (void) close(mevp->me_fd);
                        mevp->me_fd = -1;
                } else {
                        if (mevent_clarify_state(mevp)) {
                                mevent_update_one(mevp);
                        }
                }

                mevp->me_cq = 0;
                LIST_REMOVE(mevp, me_list);

                if (mevp->me_state & EV_DELETE) {
                        free(mevp);
                } else {
                        LIST_INSERT_HEAD(&global_head, mevp, me_list);
                }
        }

        mevent_qunlock();
}

static void
mevent_handle_pe(port_event_t *pe)
{
        struct mevent *mevp = pe->portev_user;

        (*mevp->me_func)(mevp->me_fd, mevp->me_type, mevp->me_param);

        mevent_qlock();
        if (!mevp->me_cq && !mevp->me_auto_requeue) {
                mevent_update_one(mevp);
        }
        mevent_qunlock();
}
#endif

static struct mevent *
mevent_add_state(int tfd, enum ev_type type,
           void (*func)(int, enum ev_type, void *), void *param,
           int state, int fflags)
{
#ifdef __FreeBSD__
        struct kevent kev;
#endif
        struct mevent *lp, *mevp;
#ifdef __FreeBSD__
        int ret;
#endif

        if (tfd < 0 || func == NULL) {
                return (NULL);
        }

        mevp = NULL;

        pthread_once(&mevent_once, mevent_init);

        mevent_qlock();

        /*
         * Verify that the fd/type tuple is not present in any list
         */
        LIST_FOREACH(lp, &global_head, me_list) {
                if (type != EVF_TIMER && lp->me_fd == tfd &&
                    lp->me_type == type) {
                        goto exit;
                }
        }

        LIST_FOREACH(lp, &change_head, me_list) {
                if (type != EVF_TIMER && lp->me_fd == tfd &&
                    lp->me_type == type) {
                        goto exit;
                }
        }

        /*
         * Allocate an entry and populate it.
         */
        mevp = calloc(1, sizeof(struct mevent));
        if (mevp == NULL) {
                goto exit;
        }

        if (type == EVF_TIMER) {
                mevp->me_msecs = tfd;
#ifdef __FreeBSD__
                mevp->me_timid = mevent_timid++;
#else
                mevp->me_timid = -1;
#endif
        } else
                mevp->me_fd = tfd;
        mevp->me_type = type;
        mevp->me_func = func;
        mevp->me_param = param;
        mevp->me_state = state;
        mevp->me_fflags = fflags;

        /*
         * Try to add the event.  If this fails, report the failure to
         * the caller.
         */
#ifdef __FreeBSD__
        mevent_populate(mevp, &kev);
        ret = kevent(mfd, &kev, 1, NULL, 0, NULL);
        if (ret == -1) {
                free(mevp);
                mevp = NULL;
                goto exit;
        }
        mevp->me_state &= ~EV_ADD;
#else
        mevent_populate(mevp);
        if (mevent_clarify_state(mevp))
                mevent_update_one(mevp);
#endif

        LIST_INSERT_HEAD(&global_head, mevp, me_list);

exit:
        mevent_qunlock();

        return (mevp);
}

struct mevent *
mevent_add(int tfd, enum ev_type type,
           void (*func)(int, enum ev_type, void *), void *param)
{

        return (mevent_add_state(tfd, type, func, param, EV_ADD, 0));
}

struct mevent *
mevent_add_flags(int tfd, enum ev_type type, int fflags,
                 void (*func)(int, enum ev_type, void *), void *param)
{

        return (mevent_add_state(tfd, type, func, param, EV_ADD, fflags));
}

struct mevent *
mevent_add_disabled(int tfd, enum ev_type type,
                    void (*func)(int, enum ev_type, void *), void *param)
{

        return (mevent_add_state(tfd, type, func, param, EV_ADD | EV_DISABLE, 0));
}

static int
mevent_update(struct mevent *evp, bool enable)
{
        int newstate;

        mevent_qlock();

        /*
         * It's not possible to enable/disable a deleted event
         */
        assert((evp->me_state & EV_DELETE) == 0);

        newstate = evp->me_state;
        if (enable) {
                newstate |= EV_ENABLE;
                newstate &= ~EV_DISABLE;
        } else {
                newstate |= EV_DISABLE;
                newstate &= ~EV_ENABLE;
        }

        /*
         * No update needed if state isn't changing
         */
        if (evp->me_state != newstate) {
                evp->me_state = newstate;

                /*
                 * Place the entry onto the changed list if not
                 * already there.
                 */
                if (evp->me_cq == 0) {
                        evp->me_cq = 1;
                        LIST_REMOVE(evp, me_list);
                        LIST_INSERT_HEAD(&change_head, evp, me_list);
                        mevent_notify();
                }
        }

        mevent_qunlock();

        return (0);
}

int
mevent_enable(struct mevent *evp)
{

        return (mevent_update(evp, true));
}

int
mevent_disable(struct mevent *evp)
{

        return (mevent_update(evp, false));
}

static int
mevent_delete_event(struct mevent *evp, int closefd)
{
        mevent_qlock();

        /*
         * Place the entry onto the changed list if not already there, and
         * mark as to be deleted.
         */
        if (evp->me_cq == 0) {
                evp->me_cq = 1;
                LIST_REMOVE(evp, me_list);
                LIST_INSERT_HEAD(&change_head, evp, me_list);
                mevent_notify();
        }
        evp->me_state = EV_DELETE;

        if (closefd)
                evp->me_closefd = 1;

        mevent_qunlock();

        return (0);
}

int
mevent_delete(struct mevent *evp)
{

        return (mevent_delete_event(evp, 0));
}

int
mevent_delete_close(struct mevent *evp)
{

        return (mevent_delete_event(evp, 1));
}

static void
mevent_set_name(void)
{

        pthread_set_name_np(mevent_tid, "mevent");
}

void
mevent_dispatch(void)
{
#ifdef __FreeBSD__
        struct kevent changelist[MEVENT_MAX];
        struct kevent eventlist[MEVENT_MAX];
        struct mevent *pipev;
        int numev;
#else
        struct mevent *pipev;
#endif
        int ret;
#ifndef WITHOUT_CAPSICUM
        cap_rights_t rights;
#endif

        mevent_tid = pthread_self();
        mevent_set_name();

        pthread_once(&mevent_once, mevent_init);

        /*
         * Open the pipe that will be used for other threads to force
         * the blocking kqueue call to exit by writing to it. Set the
         * descriptor to non-blocking.
         */
        ret = pipe(mevent_pipefd);
        if (ret < 0) {
                perror("pipe");
                exit(0);
        }

#ifndef WITHOUT_CAPSICUM
        cap_rights_init(&rights, CAP_EVENT, CAP_READ, CAP_WRITE);
        if (caph_rights_limit(mevent_pipefd[0], &rights) == -1)
                errx(EX_OSERR, "Unable to apply rights for sandbox");
        if (caph_rights_limit(mevent_pipefd[1], &rights) == -1)
                errx(EX_OSERR, "Unable to apply rights for sandbox");
#endif

        /*
         * Add internal event handler for the pipe write fd
         */
        pipev = mevent_add(mevent_pipefd[0], EVF_READ, mevent_pipe_read, NULL);
        assert(pipev != NULL);

        for (;;) {
#ifdef __FreeBSD__
                /*
                 * Build changelist if required.
                 * XXX the changelist can be put into the blocking call
                 * to eliminate the extra syscall. Currently better for
                 * debug.
                 */
                numev = mevent_build(changelist);
                if (numev) {
                        ret = kevent(mfd, changelist, numev, NULL, 0, NULL);
                        if (ret == -1) {
                                perror("Error return from kevent change");
                        }
                }

                /*
                 * Block awaiting events
                 */
                ret = kevent(mfd, NULL, 0, eventlist, MEVENT_MAX, NULL);
                if (ret == -1 && errno != EINTR) {
                        perror("Error return from kevent monitor");
                }

                /*
                 * Handle reported events
                 */
                mevent_handle(eventlist, ret);

#else /* __FreeBSD__ */
                port_event_t pev;

                /* Handle any pending updates */
                mevent_update_pending();

                /* Block awaiting events */
                ret = port_get(mfd, &pev, NULL);
                if (ret != 0) {
                        if (errno != EINTR)
                                perror("Error return from port_get");
                        continue;
                }

                /* Handle reported event */
                mevent_handle_pe(&pev);
#endif /* __FreeBSD__ */
        }
}