lib/libcs/css.c

	css.c revision 3f54fd611f536639ec30dd53c48e5ec1897cc7d9
/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*          Copyright (c) 1990-2012 AT&T Intellectual Property          *
*                      and is licensed under the                       *
*                 Eclipse Public License, Version 1.0                  *
*                    by AT&T Intellectual Property                     *
*                                                                      *
*                A copy of the License is available at                 *
*          http://www.eclipse.org/org/documents/epl-v10.html           *
*         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *
*                                                                      *
*              Information and Software Systems Research               *
*                            AT&T Research                             *
*                           Florham Park NJ                            *
*                                                                      *
*                 Glenn Fowler <gsf@research.att.com>                  *
*                                                                      *
***********************************************************************/
#pragma prototyped

/*
 * Glenn Fowler
 * AT&T Research
 *
 * connect stream server support
 */

#include "csslib.h"

#include <dirent.h>

#define OPEN_MIN    20

#if !defined(O_NONBLOCK) && defined(FNDELAY)
#define O_NONBLOCK  FNDELAY
#endif

static Common_t     state;

static int  signals[] =     /* caught by interrupt()    */
{
    SIGINT,
    SIGQUIT,
    SIGALRM,
    SIGTERM,
#ifdef SIGCHLD
    SIGCHLD,
#endif
};

/*
 * catch interrupts
 */

static void
interrupt(int sig)
{
#if defined(SIGCHLD) && !_WINIX
    if (sig != SIGCHLD)
#endif
    signal(sig, interrupt);
#ifdef SIGCHLD
    if (cs.interrupt != SIGCHLD)
#endif
    cs.interrupt = sig;
}

/*
 * called on exit
 */

static void
done(void)
{
    cssclose(NiL);
}

/*
 * drop fd ip
 */

static void
drop(Css_t* css, register Cspoll_t* pp)
{
    register Cssfd_t*   ip;
    register int        fd;
    register int        user;

    if (!css)
        css = state.main;
    fd = pp->fd;
    ip = &state.fdinfo[fd];
    if (ip->css == css)
    {
        user = (ip->events & CS_POLL_USER) != 0;
        ip->events = 0;
        if (css->auth)
            state.auth[fd].seq = 0;
        if (ip->actionf)
        {
            ip->status = CS_POLL_CLOSE;
            if ((*ip->actionf)(css, ip, css->disc) > 0)
                fd = -1;
        }
        if (state.fdpolling > 0)
        {
            state.fdpolling--;
            *pp = state.fdpoll[state.fdpolling];
        }
        css->fdpolling--;
        if (ip->events & CS_POLL_CONNECT)
            css->fdlistening--;
        if (user)
            css->fduser--;
        else if (fd >= 0)
            close(fd);
    }
}

/*
 * open the service
 */

Css_t*
cssopen(const char* path, Cssdisc_t* disc)
{
    register Css_t*     css;
    int         type;
    int         n;
    char*           s;
    char*           t;
    struct stat     st;

    if (!state.servers)
    {
        csprotect(&cs);
        if ((n = (int)strtol(astconf("OPEN_MAX", NiL, NiL), NiL, 0)) < OPEN_MIN)
            n = OPEN_MIN;
        if (!(s = newof(0, char, n * (sizeof(Cssfd_t) + sizeof(Cspoll_t) + sizeof(Auth_t)), 0)))
            return 0;
        state.fdpoll = (Cspoll_t*)(s);
        state.fdinfo = (Cssfd_t*)(state.fdpoll + n);
        state.auth = (Auth_t*)(state.fdinfo + n);
        state.fdmax = n;
        state.fdnext = -1;
        state.pid = getpid();
        if (!(css = newof(0, Css_t, 1, sizeof(Cssdisc_t))))
            return 0;
        css->id = cs.id;
        css->disc = (Cssdisc_t*)(css + 1);
        css->disc->version = CSS_VERSION;
        state.servers = state.main = css;
        atexit(done);
    }
    if (!path || (n = strlen(path) + 2) < 2 * CS_NAME_MAX)
        n = 2 * CS_NAME_MAX;
    if (!(css = newof(0, Css_t, 1, n)))
        return 0;
    n = n / 2 + 1;
    css->next = state.servers;
    state.servers = css;
    if (!(css->state = csalloc(NiL)))
        goto bad;
    css->service = (char*)(css + 1);
    css->path = css->service + n;
    css->id = state.main->id;
    css->disc = disc;
    css->fdmax = state.fdmax;
    if (path && strchr(path, '/'))
    {
        strcpy(css->path, path);
        if (tokscan(css->path, NiL, "/dev/%s/%s/%s", &s, NiL, &t) != 3)
        {
            if (css->disc->errorf)
                (*css->disc->errorf)(css, css->disc, 3, "%s: invalid connect stream path", path);
            goto bad;
        }
        type = *s;
        if (s = strchr(t, '/'))
            *s = 0;
        strncpy(css->service, t, n);
        errno = EBADF;
        if ((css->fd = csopen(css->state, path, CS_OPEN_CREATE)) < 0)
        {
            if (css->disc->errorf)
            {
                if (errno == EEXIST)
                    (*css->disc->errorf)(css, css->disc, 3, "%s: server already running", path);
                else
                    (*css->disc->errorf)(css, css->disc, ERROR_SYSTEM|3, "%s: cannot create connect stream", path);
            }
            goto bad;
        }
        css->disc->flags &= ~CSS_AUTHENTICATE;
    }
    else
    {
        sfsprintf(css->service, n, "/dev/fdp/local/%s", path);
        path = (char*)cspath(css->state, 0, 0);
        type = strmatch(path, "/dev/??p/*/*") ? path[5] : 'f';
        css->perm = S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH;
        if ((css->disc->flags & CSS_AUTHENTICATE) && csopen(css->state, css->service, CS_OPEN_CREATE|CS_OPEN_MOUNT))
        {
            if (css->disc->errorf)
                (*css->disc->errorf)(css, css->disc, ERROR_SYSTEM|3, "%s: cannot create authentication directory", css->service);
            goto bad;
        }
    }
    strcpy(css->path, path);
    if ((css->disc->flags & CSS_DAEMON) && csdaemon(css->state, (css->disc->flags & CSS_PRESERVE) ? ~0L : ((1<<css->fd)|(1<<2))))
    {
        if (css->disc->errorf)
            (*css->disc->errorf)(css, css->disc, 3, "cannot dive into background");
        goto bad;
    }
    if (css->state->control)
    {
        strcpy(css->mount, css->state->mount);
        css->control = strrchr(css->mount, '/') + 1;
        strcpy(css->control + 1, CS_MNT_TAIL);
        s = css->control - 1;
        *s = 0;
        if (stat(css->mount, &st))
        {
            if (css->disc->errorf)
                (*css->disc->errorf)(css, css->disc, 3, "%s: cannot stat service directory", css->mount);
            goto bad;
        }
        if ((css->disc->flags & CSS_DAEMON) && chdir(css->mount))
        {
            if (css->disc->errorf)
                (*css->disc->errorf)(css, css->disc, 3, "%s: cannot set service directory", css->mount);
            goto bad;
        }
        *s = '/';

        /*
         * get the fid for the global and local authentication dirs
         * authentication files can only be in these dirs and
         * must not be symlinks -- symlinks can point to untrusted
         * places and other dirs may get untrusted filesystems
         * mounted via the automounter
         */

        n = 0;
        while (s > css->mount)
            if (*--s == '/' && ++n >= 3)
                break;
        if (n != 3)
        {
            if (css->disc->errorf)
                (*css->disc->errorf)(css, css->disc, 3, "%s: invalid mount directory", css->mount);
            goto bad;
        }
        *s = 0;
        if (lstat(css->mount, &st))
        {
            if (css->disc->errorf)
                (*css->disc->errorf)(css, css->disc, 3, "%s: invalid global authentication directory", css->mount);
            goto bad;
        }
        *s = '/';
        css->fid[0].dev = st.st_dev;
        css->fid[0].ino = st.st_ino;
        s = csvar(css->state, CS_VAR_LOCAL, 0);
        if (lstat(s, &st) && (mkdir(s, S_IRWXU|S_IRWXG|S_IRWXO) || chmod(s, S_ISVTX|S_IRWXU|S_IRWXG|S_IRWXO) || lstat(s, &st)))
        {
            if (css->disc->errorf)
                (*css->disc->errorf)(css, css->disc, 3, "%s: invalid local authentication directory", s);
            goto bad;
        }
        css->fid[1].dev = st.st_dev;
        css->fid[1].ino = st.st_ino;
        css->uid = st.st_uid;
        css->gid = st.st_gid;
        if (type == 't' && *(css->control - 2) != CS_MNT_OTHER && *(css->control - 2) != '.' && *(css->control - 2) != '*')
        {
            css->auth = 1;
            state.nauth++;
            CSTIME();
            state.expire = cs.time + KEYEXPIRE;
            css->conkey = state.pid + getppid() + css->uid + st.st_ino;
            TOSS(css->conkey);
            *css->control = CS_MNT_AUTH;
            remove(css->mount);
            css->newkey = css->conkey & KEYMASK;
            if (close(open(css->mount, O_WRONLY|O_CREAT|O_TRUNC, st.st_mode & (S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH))) ||
                chmod(css->mount, st.st_mode & (S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH)) ||
                cschallenge(css->state, css->mount, NiL, &css->newkey))
            {
                if (css->disc->errorf)
                    (*css->disc->errorf)(css, css->disc, 3, "%s: cannot create service authentication file", css->mount);
                goto bad;
            }
            chown(css->mount, -1, css->gid);
            css->oldkey = css->newkey;
            for (n = 0; n < (css->newkey & 0xff); n++)
                CSTOSS(css->conkey, n);
            css->challenge = (st.st_mode & S_IXOTH) ? 2 : 0;
        }
        *css->control = CS_MNT_PROCESS;
        remove(css->mount);
        s = css->buf;
        if (type != 'f') s += sfsprintf(s, sizeof(css->buf) - (s - css->buf), "/n/%s", csname(css->state, 0));
        sfsprintf(s, sizeof(css->buf) - (s - css->buf), "/proc/%d", getpid());
        pathsetlink(css->buf, css->mount);
        if (css->disc->flags & CSS_LOG)
        {
            *css->control = CS_MNT_OLDLOG;
            strcpy(css->buf, css->mount);
            *css->control = CS_MNT_LOG;
            rename(css->mount, css->buf);
            close(2);
            open(css->mount, O_WRONLY|O_CREAT|O_TRUNC, S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
        }
        *css->control = CS_MNT_AUTH;
        css->perm = st.st_mode & (S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
        if (css->disc->flags & CSS_DAEMON)
            umask(~css->perm & (S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH));
    }
    if ((css->disc->flags & CSS_INTERRUPT) && !(state.flags & CSS_INTERRUPT))
    {
        state.flags |= CSS_INTERRUPT;
        for (n = 0; n < elementsof(signals); n++)
            if (signal(signals[n], SIG_IGN) != SIG_IGN)
                signal(signals[n], interrupt);
    }
    cssfd(css, css->fd, type == 'u' ? CS_POLL_READ : (CS_POLL_AUTH|CS_POLL_CONNECT|CS_POLL_READ));
    CSTIME();
    return css;
 bad:
    cssclose(css);
    return 0;
}

/*
 * close the service
 */

int
cssclose(register Css_t* css)
{
    register Css_t*     pss;
    register Css_t*     xss;
    register Css_t*     oss;
    register int        i;
    register int        k;

    static char     mnt[] =
    {
        CS_MNT_AUTH,
        CS_MNT_LOCK,
        CS_MNT_PROCESS,
        CS_MNT_STREAM
    };

    pss = 0;
    xss = state.servers;
    while (xss)
    {
        if (xss == css || !css)
        {
            if (xss->disc->exceptf && (xss->disc->flags & CSS_CLOSE))
                (*xss->disc->exceptf)(css, CSS_CLOSE, 0, xss->disc);
            if (state.fdinfo)
            {
                for (i = k = 0; i < state.fdpolling;)
                {
                    if (state.fdinfo[state.fdpoll[i].fd].css == xss)
                        drop(xss, &state.fdpoll[i]);
                    else
                        state.fdpoll[k++] = state.fdpoll[i++];
                }
                state.fdpolling = k;
            }
            if (state.pid == getpid() && xss->control)
                for (i = 0; i < elementsof(mnt); i++)
                {
                    *xss->control = mnt[i];
                    remove(xss->control);
                }
            if (xss->auth)
                state.nauth--;
            oss = xss;
            xss = xss->next;
            if (pss)
                pss->next = oss->next;
            else
                state.servers = oss->next;
            if (oss->state)
                csfree(oss->state);
            free(oss);
            if (css)
                return 0;
        }
        else
        {
            pss = xss;
            xss = xss->next;
        }
    }
    if (css)
        return -1;
    if (!state.servers && state.fdpoll)
    {
        free(state.fdpoll);
        state.fdpoll = 0;
    }
    return 0;
}

/*
 * file descriptor manipulation
 *
 *  CS_POLL_DUP(n)  move fd to n
 *  CS_POLL_MOVE(n) move fd to n
 *  CS_POLL_PRI(n)  set fd priority (not yet)
 *  CS_POLL_CLOSE   close+delete fd from table
 *  CS_POLL_AUTH|*  authenticate then poll
 *  CS_POLL_*   poll
 *  CS_POLL_USER|   don't close unless CS_POLL_CLOSE
 */

Cssfd_t*
cssfd(register Css_t* css, register int fd, unsigned long op)
{
    register Cssfd_t*   ip;
    register Cspoll_t*  pp;
    register int        n;
    register int        nfd;
    register int        cmd;
    int         flags;
#if DEBUG
    int         ofd = fd;
    unsigned long       oop = op;
#endif

    if (!css)
        css = state.main;
 again:
    if (fd < 0 || fd >= state.fdmax)
        return 0;
    ip = state.fdinfo + fd;
    if (op == 0)
        return ip->events ? ip : (Cssfd_t*)0;
    if (op & CS_POLL_ARG)
    {
        cmd = op & CS_POLL_MASK;
        nfd = (op >> CS_POLL_SHIFT) & CS_POLL_MASK;
        op = nfd == CS_POLL_MASK ? CS_POLL_CLOSE : 0;
    }
    else
        cmd = 0;
    if (op != CS_POLL_CLOSE)
    {
        if (op & CS_POLL_AUTH)
        {
            if (!css->auth)
                op &= ~CS_POLL_AUTH;
        }
        if (op & CS_POLL_CONNECT)
        {
            op &= ~(CS_POLL_CONTROL|CS_POLL_WRITE);
            op |= CS_POLL_READ;
        }
        for (n = 0;; n++)
        {
            if (n >= state.fdpolling)
            {
                if (!(op & CS_POLL_AUTH|CS_POLL_CONNECT|CS_POLL_READ|CS_POLL_WRITE))
                    return 0;
                if (fcntl(fd, F_SETFD, FD_CLOEXEC) && errno == EBADF)
                    return 0;
                if ((op & (CS_POLL_AUTH|CS_POLL_CONNECT)) == CS_POLL_AUTH)
                {
                    state.auth[fd].seq = 1;
                    state.auth[fd].expire = cs.time + EXPIRE;
                }
                pp = state.fdpoll + state.fdpolling++;
                pp->fd = fd;
                pp->events = op;
                pp->status = 0;
                ip->css = css;
                ip->fd = fd;
                ip->actionf = css->disc->actionf;
                ip->data = 0;
                ip->events = op;
                ip->set = 0;
                css->fdpolling++;
                if (ip->events & CS_POLL_BEFORE)
                    state.fdbefore++;
                if (ip->events & CS_POLL_CONNECT)
                    css->fdlistening++;
                if (ip->events & CS_POLL_USER)
                    css->fduser++;
#if DEBUG
                goto show;
#else
                return ip;
#endif
            }
            if (state.fdpoll[n].fd == fd)
            {
                switch (cmd)
                {
                case 0:
                    if (ip->css != css)
                        return 0;
                    if (css->fd != fd)
                    {
                        if (ip->events & CS_POLL_BEFORE)
                            state.fdbefore--;
                        if (ip->events & CS_POLL_CONNECT)
                            css->fdlistening--;
                        if (ip->events & CS_POLL_USER)
                            css->fduser--;
                        state.fdpoll[n].events = ip->events = op;
                        if (ip->events & CS_POLL_BEFORE)
                            state.fdbefore++;
                        if (ip->events & CS_POLL_CONNECT)
                            css->fdlistening++;
                        if (ip->events & CS_POLL_USER)
                            css->fduser++;
                        if (op & CS_POLL_WRITE)
                        {
#ifdef O_NONBLOCK
                            if (!(ip->set & CS_POLL_WRITE))
                            {
                                ip->set |= CS_POLL_WRITE;
                                if ((flags = fcntl(fd, F_GETFL, 0)) >= 0)
                                {
                                    flags |= O_NONBLOCK;
                                    fcntl(fd, F_SETFL, flags);
                                    messagef((state.main->id, NiL, -4, "cssfd: %d O_NONBLOCK", fd));
                                }
                            }
#endif
                            messagef((state.main->id, NiL, -4, "cssfd: %d CS_POLL_WRITE", fd));
                        }
                    }
                    break;
                case CS_POLL_DUP:
                    /*ip->actionf = 0;*/
                    css = ip->css;
                    fd = nfd;
                    op = state.fdpoll[n].events;
                    goto again;
                case CS_POLL_MOVE:
                    if (fcntl(nfd, F_SETFD, FD_CLOEXEC) && errno == EBADF)
                        return 0;
                    state.fdpoll[n].fd = nfd;
                    if (fd == css->fd)
                        css->fd = nfd;
                    state.fdinfo[nfd] = *ip;
                    ip = state.fdinfo + nfd;
                    ip->fd = nfd;
                    break;
                case CS_POLL_PRI:
                    break;
                }
#if DEBUG
 show:
                if (error_info.trace <= -9)
                {
                    errorf(state.main->id, NiL, -9, "cssfd: pending=%d polling=%d next=%d fd=%d op=0x%08lx", state.fdpending, state.fdpolling, state.fdnext, ofd, oop);
                    for (n = 0; n < state.fdpolling; n++)
                        errorf(state.main->id, NiL, -9, "cssfd: index=%d fd=%d events=%06o actionf=%p", n, state.fdpoll[n].fd, state.fdpoll[n].events, state.fdinfo[state.fdpoll[n].fd].actionf);
                }
#endif
                return ip;
            }
        }
    }
    else if (css->fd != fd)
    {
        for (n = 0; n < state.fdpolling; n++)
            if (state.fdpoll[n].fd == fd)
            {
                drop(state.fdinfo[fd].css, &state.fdpoll[n]);
                break;
            }
        if (n >= state.fdpolling)
            close(fd);
#if DEBUG
        ip = 0;
        goto show;
#endif
    }
    return 0;
}

/*
 * poll for the next fd event
 * some events may be pending from the last call
 */

Cssfd_t*
csspoll(unsigned long ms, unsigned long flags)
{
    register Css_t*     css;
    register Cspoll_t*  pp;
    register Cssfd_t*   ip;
    register Auth_t*    ap;
    register int        fd;
    char*           s;
    char*           t;
    int         n;
    int         fdnew;
    int         status;
    int         to;
    int         oerrno;
    int         err;
    int         clrerr;
    int         sig;
    int         clrsig;
    unsigned long       key;
    unsigned long       z;
    unsigned long       timeout;
    Csid_t          id;
    struct stat     st;
    char**          vp;
    char*           va[8];

    if (state.polling && !(flags & CSS_RECURSIVE))
    {
        errno = EBUSY;
        return 0;
    }
    state.polling++;
    if (ms == CS_NEVER)
        timeout = 0;
    else
        timeout = CSTIME() + ((ms + 999) / 1000);
    oerrno = errno;
    for (;;)
    {
        while (state.fdpending <= 0)
        {
            CSTIME();
            if (timeout && timeout >= cs.time)
            {
                errno = oerrno;
                return 0;
            }
            if (state.nauth && cs.time > state.expire)
            {
                state.expire = cs.time + KEYEXPIRE;
                for (css = state.servers; css; css = css->next)
                    if (css->auth)
                    {
                        css->oldkey = css->newkey;
                        n = cs.time & 077;
                        do TOSS(css->newkey); while (n--);
                        css->newkey &= KEYMASK;
                        *css->control = CS_MNT_AUTH;
                        if (cschallenge(css->state, css->mount, NiL, &css->newkey))
                            css->newkey = css->oldkey;
                    }
                for (pp = state.fdpoll; pp < state.fdpoll + state.fdpolling;)
                {
                    ap = state.auth + pp->fd;
                    if (ap->seq && cs.time > ap->expire)
                        drop(state.fdinfo[pp->fd].css, pp);
                    else
                        pp++;
                }
            }
            to = ms;
            for (css = state.servers; css; css = css->next)
            {
                css->fdpending = 0;
                if (css->disc->timeout)
                {
                    if (css->timeout_last != css->disc->timeout)
                        css->timeout_last = css->timeout_remain = css->disc->timeout;
                    if (to > css->timeout_remain)
                        to = css->timeout_remain;
                }
                if (css->disc->wakeup)
                {
                    if (css->wakeup_last != css->disc->wakeup)
                        css->wakeup_last = css->wakeup_remain = css->disc->wakeup;
                    if (to > css->wakeup_remain)
                        to = css->wakeup_remain;
                }
            }
            if (state.fdbefore)
                for (pp = state.fdpoll; pp < state.fdpoll + state.fdpolling;)
                {
                    if (pp->events & CS_POLL_BEFORE)
                    {
                        ip = state.fdinfo + pp->fd;
                        ip->status = CS_POLL_BEFORE;
                        if (ip->actionf && (*ip->actionf)(ip->css, ip, ip->css->disc) < 0)
                        {
                            drop(ip->css, pp);
                            continue;
                        }
                    }
                    pp++;
                }
            z = cs.time;
            if ((state.fdpending = cspoll(&cs, state.fdpoll, state.fdpolling, to)) < 0)
            {
                err = errno;
                sig = (err == EINTR) ? cs.interrupt : 0;
                clrsig = 0;
                clrerr = 0;
            }
            else
            {
                err = 0;
                sig = 0;
            }
            state.fdloop = 1;
            CSTIME();
            if (state.fdpending)
                z = (cs.time - z) * 1000;
            else
                z = to;
            if (ms != CS_NEVER)
            {
                if (ms > z)
                    ms -= z;
                else
                    timeout = cs.time;
            }
            if (state.fdpending > 0)
                for (pp = state.fdpoll; pp < state.fdpoll + state.fdpolling; pp++)
                    if (pp->status & (CS_POLL_READ|CS_POLL_WRITE))
                        state.fdinfo[pp->fd].css->fdpending++;
            for (css = state.servers; css; css = css->next)
                if (css->disc->exceptf)
                {
                    if (css->disc->timeout)
                    {
                        if (css->fdpending)
                            css->timeout_remain = css->disc->timeout;
                        else if (css->timeout_remain <= z)
                        {
                            if ((css->disc->flags & CSS_DORMANT) && css->fdpolling <= (css->fdlistening + css->fduser))
                                (*css->disc->exceptf)(css, CSS_DORMANT, 0, css->disc);
                            else if (css->disc->flags & CSS_TIMEOUT)
                                (*css->disc->exceptf)(css, CSS_TIMEOUT, 0, css->disc);
                            css->timeout_last = css->timeout_remain = css->disc->timeout;
                        }
                        else
                            css->timeout_remain -= z;
                    }
                    if (css->disc->wakeup)
                    {
                        messagef((state.main->id, NiL, -4, "csspoll: pending=%d polling=%d z=%I*d wakeup=%I*d remain=%I*d", state.fdpending, state.fdpolling, sizeof(z), z, sizeof(css->disc->wakeup), css->disc->wakeup, sizeof(css->wakeup_remain), css->wakeup_remain));
                        if (css->wakeup_remain <= z)
                        {
                            (*css->disc->exceptf)(css, CSS_WAKEUP, 0, css->disc);
                            css->wakeup_last = css->wakeup_remain = css->disc->wakeup;
                        }
                        else
                            css->wakeup_remain -= z;
                    }
                    if (err)
                    {
                        if ((css->disc->flags & CSS_INTERRUPT) && (sig || err == EINTR))
                        {
                            if (!sig)
                                clrerr = 1;
                            else if ((*css->disc->exceptf)(css, CSS_INTERRUPT, sig, css->disc) >= 0)
                                clrsig = 1;
                        }
                        else if (css->disc->flags & CSS_ERROR)
                        {
                            if ((*css->disc->exceptf)(css, CSS_ERROR, err, css->disc) >= 0)
                                clrerr = 1;
                        }
                    }
                }
            if (err && (ms != CS_NEVER || (flags & CSS_INTERRUPT) && (sig || err == EINTR) && !clrsig || (flags & CSS_ERROR) && !sig && err != EINTR && !clrerr))
            {
                errno = err;
                state.polling--;
                return 0;
            }
        }
        do
        {
            if (++state.fdnext >= state.fdpolling)
            {
                if (state.fdloop-- < 0)
                    break;
                state.fdnext = 0;
            }
            pp = state.fdpoll + state.fdnext;
            fd = pp->fd;
            messagef((state.main->id, NiL, -9, "csspoll: pending=%d polling=%d next=%d fd=%d status=%06o", state.fdpending, state.fdpolling, state.fdnext, fd, pp->status));
            ip = state.fdinfo + fd;
            css = ip->css;
            status = pp->status & ~(CS_POLL_BEFORE|CS_POLL_USER);
            pp->status = 0;
            switch (status)
            {
            case CS_POLL_AUTH|CS_POLL_CONNECT|CS_POLL_READ:
                if (css->auth)
                {
                    if (csrecv(css->state, fd, &id, &fdnew, 1) == 1)
                    {
                        state.auth[fdnew].id = id;
                        cssfd(css, fdnew, CS_POLL_AUTH|CS_POLL_READ);
                    }
                    break;
                }
                /*FALLTHROUGH*/
            case CS_POLL_CONNECT|CS_POLL_READ:
                if (csrecv(css->state, fd, &id, &fdnew, 1) == 1 &&
                    (ip = cssfd(css, fdnew, CS_POLL_READ)) &&
                    css->disc->acceptf &&
                    (fdnew = (*css->disc->acceptf)(css, ip, &id, NiL, css->disc)) != ip->fd)
                        cssfd(css, ip->fd, fdnew >= 0 ? CS_POLL_CMD(fdnew, CS_POLL_MOVE) : CS_POLL_CLOSE);
                break;
            case CS_POLL_AUTH|CS_POLL_READ:
                switch ((ap = state.auth + fd)->seq)
                {
                case 1:
                    if ((n = csread(css->state, fd, css->buf, sizeof(css->buf), CS_LINE)) <= 0)
                        goto reject;
                    css->buf[n - 1] = 0;
                    if (tokscan(css->buf, &t, "%lu", &key) != 1)
                        goto reject;
                    switch (key)
                    {
                    case CS_KEY_SEND:
                        n = sfsprintf(css->tmp, sizeof(css->tmp), "%s\n", css->mount);
                        if (cswrite(css->state, fd, css->tmp, n) != n)
                            goto reject;
                        break;
                    default:
                        if (key <= CS_KEY_MAX || key != css->newkey && key != css->oldkey || tokscan(t, NiL, "%ld", &ap->id.pid) != 1)
                            goto reject;
                        if (!(ap->seq = css->challenge))
                        {
                            st.st_uid = css->uid;
                            st.st_gid = css->gid;
                            goto ok;
                        }
                        css->conkey ^= cs.time ^ ap->id.pid;
                        n = cs.time & 017;
                        do TOSS(css->conkey); while (n--);
                        ap->atime = css->conkey & KEYMASK;
                        n = cs.time & 07;
                        do TOSS(css->conkey); while (n--);
                        ap->mtime = css->conkey & KEYMASK;
                        n = sfsprintf(css->tmp, sizeof(css->tmp), "%lu %lu\n", (unsigned long)ap->atime, (unsigned long)ap->mtime);
                        if (cswrite(css->state, fd, css->tmp, n) != n)
                            goto reject;
                        ap->expire = cs.time + EXPIRE;
                        break;
                    }
                    break;
                case 2:
                    ap->seq = 0;
                    if (cs.time > ap->expire || (n = csread(css->state, fd, css->buf, sizeof(css->buf), CS_LINE)) <= 1)
                        goto reject;
                    css->buf[n - 1] = 0;
                    if (t = strchr(css->buf, ' '))
                        *t++ = 0;
                    if (!(s = strrchr(css->buf, '/')))
                        goto reject;
                    *s = 0;
                    if (lstat(css->buf, &st))
                        goto reject;
                    *s = '/';
                    for (n = 0; n < elementsof(css->fid); n++)
#if _UWIN
                        if (css->fid[n].dev == st.st_dev)
#else
                        if (css->fid[n].dev == st.st_dev && css->fid[n].ino == st.st_ino)
#endif
                            break;
                    if (n >= elementsof(css->fid))
                        goto reject;
                    if (lstat(css->buf, &st))
                    {
                        /*
                         * kick the NonFS cache
                         */

                        if (!(s = strrchr(css->buf, '.')))
                            goto reject;
                        *s = 0;
                        close(open(css->buf, O_WRONLY|O_CREAT|O_TRUNC, 0));
                        remove(css->buf);
                        *s = '.';
                        if (lstat(css->buf, &st))
                            goto reject;
                    }
                    if ((st.st_mode & CS_AUTH_MODE) != CS_AUTH_MODE ||
                        ap->atime != st.st_atime ||
                        ap->mtime != st.st_mtime)
                            goto reject;
                ok:
                    if (cswrite(css->state, fd, "\n", 1) != 1)
                        goto reject;
                    pp->events &= ~CS_POLL_AUTH;
                    if (css->disc->acceptf)
                    {
                        ip = state.fdinfo + pp->fd;
                        ap->id.uid = st.st_uid;
                        ap->id.gid = st.st_gid;
                        vp = va;
                        while ((vp < &va[elementsof(va) - 1]) &&
                            (*vp++ = t) && (t = strchr(t, ' ')))
                                *t++ = 0;
                        *vp = 0;
                        if ((fdnew = (*css->disc->acceptf)(css, ip, &ap->id, *va ? va : (char**)0, css->disc)) != ip->fd)
                            cssfd(css, ip->fd, fdnew >= 0 ? CS_POLL_CMD(fdnew, CS_POLL_MOVE) : CS_POLL_CLOSE);
                    }
                    break;
                default:
                    goto reject;
                }
                break;
            case CS_POLL_READ|CS_POLL_WRITE:
            case CS_POLL_WRITE:
                pp->events &= ~CS_POLL_WRITE;
                /*FALLTHROUGH*/
            case CS_POLL_READ:
                ip->status = status;
                messagef((state.main->id, NiL, -9, "csspoll: status=%06o fd=%d actionf=%p", status, fd, ip->actionf));
                if (!ip->actionf || (n = (*ip->actionf)(css, ip, css->disc)) == 0)
                {
                    state.fdpending--;
                    state.polling--;
                    return ip;
                }
                if (n < 0)
                    goto reject;
                break;
            case CS_POLL_AUTH:
            case CS_POLL_AUTH|CS_POLL_CONNECT:
            case CS_POLL_CONNECT:
                break;
            case 0:
                continue;
            default:
            reject:
                drop(css, pp);
                state.fdnext--;
                break;
            }
            state.fdpending--;
        } while (state.fdpending);
    }
}