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IABSD.fr/xenocara/xserver/os/connection.c

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  • Author : matthieu
    Date : 2026-05-08 11:12:08
    Hash : f0e0a48c
    Message : Update to xserver 21.1.22. The security fixes were already committed.

  • xserver/os/connection.c
  • /***********************************************************
    
    Copyright 1987, 1989, 1998  The Open Group
    
    Permission to use, copy, modify, distribute, and sell this software and its
    documentation for any purpose is hereby granted without fee, provided that
    the above copyright notice appear in all copies and that both that
    copyright notice and this permission notice appear in supporting
    documentation.
    
    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.
    
    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
    AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
    CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    
    Except as contained in this notice, the name of The Open Group shall not be
    used in advertising or otherwise to promote the sale, use or other dealings
    in this Software without prior written authorization from The Open Group.
    
    Copyright 1987, 1989 by Digital Equipment Corporation, Maynard, Massachusetts.
    
                            All Rights Reserved
    
    Permission to use, copy, modify, and distribute this software and its
    documentation for any purpose and without fee is hereby granted,
    provided that the above copyright notice appear in all copies and that
    both that copyright notice and this permission notice appear in
    supporting documentation, and that the name of Digital not be
    used in advertising or publicity pertaining to distribution of the
    software without specific, written prior permission.
    
    DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
    ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
    DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
    ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
    WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
    ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
    SOFTWARE.
    
    ******************************************************************/
    /*****************************************************************
     *  Stuff to create connections --- OS dependent
     *
     *      EstablishNewConnections, CreateWellKnownSockets, ResetWellKnownSockets,
     *      CloseDownConnection,
     *	OnlyListToOneClient,
     *      ListenToAllClients,
     *
     *      (WaitForSomething is in its own file)
     *
     *      In this implementation, a client socket table is not kept.
     *      Instead, what would be the index into the table is just the
     *      file descriptor of the socket.  This won't work for if the
     *      socket ids aren't small nums (0 - 2^8)
     *
     *****************************************************************/
    
    #ifdef HAVE_DIX_CONFIG_H
    #include <dix-config.h>
    #endif
    
    #ifdef WIN32
    #include <X11/Xwinsock.h>
    #endif
    #include <X11/X.h>
    #include <X11/Xproto.h>
    #define XSERV_t
    #define TRANS_SERVER
    #define TRANS_REOPEN
    #include <X11/Xtrans/Xtrans.h>
    #include <X11/Xtrans/Xtransint.h>
    #include <errno.h>
    #include <signal.h>
    #include <stdio.h>
    #include <stdlib.h>
    
    #include <sys/stat.h>
    
    #ifndef WIN32
    #include <sys/socket.h>
    
    #if defined(TCPCONN)
    #include <netinet/in.h>
    #include <arpa/inet.h>
    #ifdef apollo
    #ifndef NO_TCP_H
    #include <netinet/tcp.h>
    #endif
    #else
    #ifdef CSRG_BASED
    #include <sys/param.h>
    #endif
    #include <netinet/tcp.h>
    #endif
    #include <arpa/inet.h>
    #endif
    
    #include <sys/uio.h>
    
    #endif                          /* WIN32 */
    #include "misc.h"               /* for typedef of pointer */
    #include "osdep.h"
    #include "opaque.h"
    #include "dixstruct.h"
    #include "xace.h"
    
    #define Pid_t pid_t
    
    #ifdef HAVE_GETPEERUCRED
    #include <ucred.h>
    #include <zone.h>
    #else
    #define zoneid_t int
    #endif
    
    #ifdef HAVE_SYSTEMD_DAEMON
    #include <systemd/sd-daemon.h>
    #endif
    
    #include "probes.h"
    
    struct ospoll   *server_poll;
    
    Bool NewOutputPending;          /* not yet attempted to write some new output */
    Bool NoListenAll;               /* Don't establish any listening sockets */
    
    static Bool RunFromSmartParent; /* send SIGUSR1 to parent process */
    Bool RunFromSigStopParent;      /* send SIGSTOP to our own process; Upstart (or
                                       equivalent) will send SIGCONT back. */
    static char dynamic_display[7]; /* display name */
    Bool PartialNetwork;            /* continue even if unable to bind all addrs */
    static Pid_t ParentProcess;
    
    int GrabInProgress = 0;
    
    static void
    EstablishNewConnections(int curconn, int ready, void *data);
    
    static void
    set_poll_client(ClientPtr client);
    
    static void
    set_poll_clients(void);
    
    static XtransConnInfo *ListenTransConns = NULL;
    static int *ListenTransFds = NULL;
    static int ListenTransCount;
    
    static void ErrorConnMax(XtransConnInfo /* trans_conn */ );
    
    static int FdReserve = 5;
    static Bool Backoff = FALSE;
    
    static XtransConnInfo
    lookup_trans_conn(int fd)
    {
        if (ListenTransFds) {
            int i;
    
            for (i = 0; i < ListenTransCount; i++)
                if (ListenTransFds[i] == fd)
                    return ListenTransConns[i];
        }
    
        return NULL;
    }
    
    /*
     * If SIGUSR1 was set to SIG_IGN when the server started, assume that either
     *
     *  a- The parent process is ignoring SIGUSR1
     *
     * or
     *
     *  b- The parent process is expecting a SIGUSR1
     *     when the server is ready to accept connections
     *
     * In the first case, the signal will be harmless, in the second case,
     * the signal will be quite useful.
     */
    static void
    InitParentProcess(void)
    {
    #if !defined(WIN32)
        OsSigHandlerPtr handler;
    
        handler = OsSignal(SIGUSR1, SIG_IGN);
        if (handler == SIG_IGN)
            RunFromSmartParent = TRUE;
        OsSignal(SIGUSR1, handler);
        ParentProcess = getppid();
    #ifdef X_PRIVSEP
        priv_init_parent_process(ParentProcess);
    #endif
    #endif
    }
    
    void
    NotifyParentProcess(void)
    {
    #if !defined(WIN32)
        if (displayfd >= 0) {
            if (write(displayfd, display, strlen(display)) != strlen(display))
                FatalError("Cannot write display number to fd %d\n", displayfd);
            if (write(displayfd, "\n", 1) != 1)
                FatalError("Cannot write display number to fd %d\n", displayfd);
            close(displayfd);
            displayfd = -1;
        }
        if (RunFromSmartParent) {
    	if (ParentProcess > 1) {
    #ifdef X_PRIVSEP
                priv_signal_parent();
    #else
                kill (ParentProcess, SIGUSR1);
    #endif
    	}
        }
        if (RunFromSigStopParent)
            raise(SIGSTOP);
    #ifdef HAVE_SYSTEMD_DAEMON
        /* If we have been started as a systemd service, tell systemd that
           we are ready. Otherwise sd_notify() won't do anything. */
        sd_notify(0, "READY=1");
    #endif
    #endif
    }
    
    static Bool
    TryCreateSocket(int num, int *partial)
    {
        char port[20];
    
        snprintf(port, sizeof(port), "%d", num);
    
        return (_XSERVTransMakeAllCOTSServerListeners(port, partial,
                                                      &ListenTransCount,
                                                      &ListenTransConns) >= 0);
    }
    
    /*****************
     * CreateWellKnownSockets
     *    At initialization, create the sockets to listen on for new clients.
     *****************/
    
    void
    CreateWellKnownSockets(void)
    {
        int i;
        int partial = 0;
    
        /* display is initialized to "0" by main(). It is then set to the display
         * number if specified on the command line. */
    
        if (NoListenAll) {
            ListenTransCount = 0;
        }
        else if ((displayfd < 0) || explicit_display) {
            if (TryCreateSocket(atoi(display), &partial) &&
                ListenTransCount >= 1)
                if (!PartialNetwork && partial)
                    FatalError ("Failed to establish all listening sockets");
        }
        else { /* -displayfd and no explicit display number */
            Bool found = 0;
            for (i = 0; i < 65536 - X_TCP_PORT; i++) {
                if (TryCreateSocket(i, &partial) && !partial) {
                    found = 1;
                    break;
                }
                else
                    CloseWellKnownConnections();
            }
            if (!found)
                FatalError("Failed to find a socket to listen on");
            snprintf(dynamic_display, sizeof(dynamic_display), "%d", i);
            display = dynamic_display;
            LogSetDisplay();
        }
    
        ListenTransFds = xallocarray(ListenTransCount, sizeof (int));
        if (ListenTransFds == NULL)
            FatalError ("Failed to create listening socket array");
    
        for (i = 0; i < ListenTransCount; i++) {
            int fd = _XSERVTransGetConnectionNumber(ListenTransConns[i]);
    
            ListenTransFds[i] = fd;
            _XSERVTransSetOption(ListenTransConns[i], TRANS_CLOSEONEXEC, 0);
            SetNotifyFd(fd, EstablishNewConnections, X_NOTIFY_READ, NULL);
    
            if (!_XSERVTransIsLocal(ListenTransConns[i]))
                DefineSelf (fd);
        }
    
        if (ListenTransCount == 0 && !NoListenAll)
            FatalError
                ("Cannot establish any listening sockets - Make sure an X server isn't already running");
    
    #if !defined(WIN32)
        OsSignal(SIGPIPE, SIG_IGN);
        OsSignal(SIGHUP, AutoResetServer);
    #endif
        OsSignal(SIGINT, GiveUp);
        OsSignal(SIGTERM, GiveUp);
        ResetHosts(display);
    
        InitParentProcess();
    
    #ifdef XDMCP
        XdmcpInit();
    #endif
    }
    
    void
    ResetWellKnownSockets(void)
    {
        int i;
    
        ResetOsBuffers();
    
        for (i = 0; i < ListenTransCount; i++) {
            int status = _XSERVTransResetListener(ListenTransConns[i]);
    
            if (status != TRANS_RESET_NOOP) {
                if (status == TRANS_RESET_FAILURE) {
                    /*
                     * ListenTransConns[i] freed by xtrans.
                     * Remove it from out list.
                     */
    
                    RemoveNotifyFd(ListenTransFds[i]);
                    ListenTransFds[i] = ListenTransFds[ListenTransCount - 1];
                    ListenTransConns[i] = ListenTransConns[ListenTransCount - 1];
                    ListenTransCount -= 1;
                    i -= 1;
                }
                else if (status == TRANS_RESET_NEW_FD) {
                    /*
                     * A new file descriptor was allocated (the old one was closed)
                     */
    
                    int newfd = _XSERVTransGetConnectionNumber(ListenTransConns[i]);
    
                    ListenTransFds[i] = newfd;
                }
            }
        }
        for (i = 0; i < ListenTransCount; i++)
            SetNotifyFd(ListenTransFds[i], EstablishNewConnections, X_NOTIFY_READ,
                        NULL);
    
        ResetAuthorization();
        ResetHosts(display);
        /*
         * restart XDMCP
         */
    #ifdef XDMCP
        XdmcpReset();
    #endif
    }
    
    void
    CloseWellKnownConnections(void)
    {
        int i;
    
        for (i = 0; i < ListenTransCount; i++) {
            if (ListenTransConns[i] != NULL) {
                _XSERVTransClose(ListenTransConns[i]);
                ListenTransConns[i] = NULL;
                if (ListenTransFds != NULL)
                    RemoveNotifyFd(ListenTransFds[i]);
            }
        }
        ListenTransCount = 0;
    }
    
    static void
    AuthAudit(ClientPtr client, Bool letin,
              struct sockaddr *saddr, int len,
              unsigned int proto_n, char *auth_proto, int auth_id)
    {
        char addr[128];
        char client_uid_string[64];
        LocalClientCredRec *lcc;
    
    #ifdef XSERVER_DTRACE
        pid_t client_pid = -1;
        zoneid_t client_zid = -1;
    #endif
    
        if (!len)
            strlcpy(addr, "local host", sizeof(addr));
        else
            switch (saddr->sa_family) {
            case AF_UNSPEC:
    #if defined(UNIXCONN) || defined(LOCALCONN)
            case AF_UNIX:
    #endif
                strlcpy(addr, "local host", sizeof(addr));
                break;
    #if defined(TCPCONN)
            case AF_INET:
                snprintf(addr, sizeof(addr), "IP %s",
                         inet_ntoa(((struct sockaddr_in *) saddr)->sin_addr));
                break;
    #if defined(IPv6) && defined(AF_INET6)
            case AF_INET6:{
                char ipaddr[INET6_ADDRSTRLEN];
    
                inet_ntop(AF_INET6, &((struct sockaddr_in6 *) saddr)->sin6_addr,
                          ipaddr, sizeof(ipaddr));
                snprintf(addr, sizeof(addr), "IP %s", ipaddr);
            }
                break;
    #endif
    #endif
            default:
                strlcpy(addr, "unknown address", sizeof(addr));
            }
    
        if (GetLocalClientCreds(client, &lcc) != -1) {
            int slen;               /* length written to client_uid_string */
    
            strcpy(client_uid_string, " ( ");
            slen = 3;
    
            if (lcc->fieldsSet & LCC_UID_SET) {
                snprintf(client_uid_string + slen,
                         sizeof(client_uid_string) - slen,
                         "uid=%ld ", (long) lcc->euid);
                slen = strlen(client_uid_string);
            }
    
            if (lcc->fieldsSet & LCC_GID_SET) {
                snprintf(client_uid_string + slen,
                         sizeof(client_uid_string) - slen,
                         "gid=%ld ", (long) lcc->egid);
                slen = strlen(client_uid_string);
            }
    
            if (lcc->fieldsSet & LCC_PID_SET) {
    #ifdef XSERVER_DTRACE
                client_pid = lcc->pid;
    #endif
                snprintf(client_uid_string + slen,
                         sizeof(client_uid_string) - slen,
                         "pid=%ld ", (long) lcc->pid);
                slen = strlen(client_uid_string);
            }
    
            if (lcc->fieldsSet & LCC_ZID_SET) {
    #ifdef XSERVER_DTRACE
                client_zid = lcc->zoneid;
    #endif
                snprintf(client_uid_string + slen,
                         sizeof(client_uid_string) - slen,
                         "zoneid=%ld ", (long) lcc->zoneid);
                slen = strlen(client_uid_string);
            }
    
            snprintf(client_uid_string + slen, sizeof(client_uid_string) - slen,
                     ")");
            FreeLocalClientCreds(lcc);
        }
        else {
            client_uid_string[0] = '\0';
        }
    
    #ifdef XSERVER_DTRACE
        XSERVER_CLIENT_AUTH(client->index, addr, client_pid, client_zid);
    #endif
        if (auditTrailLevel > 1) {
            if (proto_n)
                AuditF("client %d %s from %s%s\n  Auth name: %.*s ID: %d\n",
                       client->index, letin ? "connected" : "rejected", addr,
                       client_uid_string, (int) proto_n, auth_proto, auth_id);
            else
                AuditF("client %d %s from %s%s\n",
                       client->index, letin ? "connected" : "rejected", addr,
                       client_uid_string);
    
        }
    }
    
    XID
    AuthorizationIDOfClient(ClientPtr client)
    {
        if (client->osPrivate)
            return ((OsCommPtr) client->osPrivate)->auth_id;
        else
            return None;
    }
    
    /*****************************************************************
     * ClientAuthorized
     *
     *    Sent by the client at connection setup:
     *                typedef struct _xConnClientPrefix {
     *                   CARD8	byteOrder;
     *                   BYTE	pad;
     *                   CARD16	majorVersion, minorVersion;
     *                   CARD16	nbytesAuthProto;
     *                   CARD16	nbytesAuthString;
     *                 } xConnClientPrefix;
     *
     *     	It is hoped that eventually one protocol will be agreed upon.  In the
     *        mean time, a server that implements a different protocol than the
     *        client expects, or a server that only implements the host-based
     *        mechanism, will simply ignore this information.
     *
     *****************************************************************/
    
    const char *
    ClientAuthorized(ClientPtr client,
                     unsigned int proto_n, char *auth_proto,
                     unsigned int string_n, char *auth_string)
    {
        OsCommPtr priv;
        Xtransaddr *from = NULL;
        int family;
        int fromlen;
        XID auth_id;
        const char *reason = NULL;
        XtransConnInfo trans_conn;
    
        priv = (OsCommPtr) client->osPrivate;
        trans_conn = priv->trans_conn;
    
        /* Allow any client to connect without authorization on a launchd socket,
           because it is securely created -- this prevents a race condition on launch */
        if (trans_conn->flags & TRANS_NOXAUTH) {
            auth_id = (XID) 0L;
        }
        else {
            auth_id =
                CheckAuthorization(proto_n, auth_proto, string_n, auth_string,
                                   client, &reason);
        }
    
        if (auth_id == (XID) ~0L) {
            if (_XSERVTransGetPeerAddr(trans_conn, &family, &fromlen, &from) != -1) {
                if (InvalidHost((struct sockaddr *) from, fromlen, client))
                    AuthAudit(client, FALSE, (struct sockaddr *) from,
                              fromlen, proto_n, auth_proto, auth_id);
                else {
                    auth_id = (XID) 0;
    #ifdef XSERVER_DTRACE
                    if ((auditTrailLevel > 1) || XSERVER_CLIENT_AUTH_ENABLED())
    #else
                    if (auditTrailLevel > 1)
    #endif
                        AuthAudit(client, TRUE,
                                  (struct sockaddr *) from, fromlen,
                                  proto_n, auth_proto, auth_id);
                }
    
                free(from);
            }
    
            if (auth_id == (XID) ~0L) {
                if (reason)
                    return reason;
                else
                    return "Client is not authorized to connect to Server";
            }
        }
    #ifdef XSERVER_DTRACE
        else if ((auditTrailLevel > 1) || XSERVER_CLIENT_AUTH_ENABLED())
    #else
        else if (auditTrailLevel > 1)
    #endif
        {
            if (_XSERVTransGetPeerAddr(trans_conn, &family, &fromlen, &from) != -1) {
                AuthAudit(client, TRUE, (struct sockaddr *) from, fromlen,
                          proto_n, auth_proto, auth_id);
    
                free(from);
            }
        }
        priv->auth_id = auth_id;
        priv->conn_time = 0;
    
    #ifdef XDMCP
        /* indicate to Xdmcp protocol that we've opened new client */
        XdmcpOpenDisplay(priv->fd);
    #endif                          /* XDMCP */
    
        XaceHook(XACE_AUTH_AVAIL, client, auth_id);
    
        /* At this point, if the client is authorized to change the access control
         * list, we should getpeername() information, and add the client to
         * the selfhosts list.  It's not really the host machine, but the
         * true purpose of the selfhosts list is to see who may change the
         * access control list.
         */
        return ((char *) NULL);
    }
    
    static void
    ClientReady(int fd, int xevents, void *data)
    {
        ClientPtr client = data;
    
        if (xevents & X_NOTIFY_ERROR) {
            CloseDownClient(client);
            return;
        }
        if (xevents & X_NOTIFY_READ)
            mark_client_ready(client);
        if (xevents & X_NOTIFY_WRITE) {
            ospoll_mute(server_poll, fd, X_NOTIFY_WRITE);
            NewOutputPending = TRUE;
        }
    }
    
    static ClientPtr
    AllocNewConnection(XtransConnInfo trans_conn, int fd, CARD32 conn_time)
    {
        OsCommPtr oc;
        ClientPtr client;
    
        oc = malloc(sizeof(OsCommRec));
        if (!oc)
            return NullClient;
        oc->trans_conn = trans_conn;
        oc->fd = fd;
        oc->input = (ConnectionInputPtr) NULL;
        oc->output = (ConnectionOutputPtr) NULL;
        oc->auth_id = None;
        oc->conn_time = conn_time;
        oc->flags = 0;
        if (!(client = NextAvailableClient((void *) oc))) {
            free(oc);
            return NullClient;
        }
        client->local = ComputeLocalClient(client);
        ospoll_add(server_poll, fd,
                   ospoll_trigger_edge,
                   ClientReady,
                   client);
        set_poll_client(client);
    
    #ifdef DEBUG
        ErrorF("AllocNewConnection: client index = %d, socket fd = %d, local = %d\n",
               client->index, fd, client->local);
    #endif
    #ifdef XSERVER_DTRACE
        XSERVER_CLIENT_CONNECT(client->index, fd);
    #endif
    
        return client;
    }
    
    /*****************
     * EstablishNewConnections
     *    If anyone is waiting on listened sockets, accept them. Drop pending
     *    connections if they've stuck around for more than one minute.
     *****************/
    #define TimeOutValue 60 * MILLI_PER_SECOND
    static void
    EstablishNewConnections(int curconn, int ready, void *data)
    {
        int newconn;       /* fd of new client */
        CARD32 connect_time;
        int i;
        ClientPtr client;
        OsCommPtr oc;
        XtransConnInfo trans_conn, new_trans_conn;
        int status;
    
        connect_time = GetTimeInMillis();
        /* kill off stragglers */
        for (i = 1; i < currentMaxClients; i++) {
            if ((client = clients[i])) {
                oc = (OsCommPtr) (client->osPrivate);
                if ((oc && (oc->conn_time != 0) &&
                     (connect_time - oc->conn_time) >= TimeOutValue) ||
                    (client->noClientException != Success && !client->clientGone))
                    CloseDownClient(client);
            }
        }
    
        if ((trans_conn = lookup_trans_conn(curconn)) == NULL)
            return;
    
        if ((getdtablecount() + FdReserve) >= getdtablesize())
            Backoff = TRUE;
        else
            Backoff = FALSE;
    
        if ((new_trans_conn = _XSERVTransAccept(trans_conn, &status)) == NULL)
            return;
    
        newconn = _XSERVTransGetConnectionNumber(new_trans_conn);
    
        _XSERVTransSetOption(new_trans_conn, TRANS_NONBLOCKING, 1);
    
        if (trans_conn->flags & TRANS_NOXAUTH)
            new_trans_conn->flags = new_trans_conn->flags | TRANS_NOXAUTH;
    
        if (Backoff || !AllocNewConnection(new_trans_conn, newconn, connect_time)) {
            ErrorConnMax(new_trans_conn);
        }
        return;
    }
    
    #define NOROOM "Maximum number of clients reached"
    
    /************
     *   ErrorConnMax
     *     Fail a connection due to lack of client or file descriptor space
     ************/
    
    static void
    ConnMaxNotify(int fd, int events, void *data)
    {
        XtransConnInfo trans_conn = data;
        char order = 0;
    
        /* try to read the byte-order of the connection */
        (void) _XSERVTransRead(trans_conn, &order, 1);
        if (order == 'l' || order == 'B' || order == 'r' || order == 'R') {
            xConnSetupPrefix csp;
            char pad[3] = { 0, 0, 0 };
            int whichbyte = 1;
            struct iovec iov[3];
    
            csp.success = xFalse;
            csp.lengthReason = sizeof(NOROOM) - 1;
            csp.length = (sizeof(NOROOM) + 2) >> 2;
            csp.majorVersion = X_PROTOCOL;
            csp.minorVersion = X_PROTOCOL_REVISION;
            if (((*(char *) &whichbyte) && (order == 'B' || order == 'R')) ||
                (!(*(char *) &whichbyte) && (order == 'l' || order == 'r'))) {
                swaps(&csp.majorVersion);
                swaps(&csp.minorVersion);
                swaps(&csp.length);
            }
            iov[0].iov_len = sz_xConnSetupPrefix;
            iov[0].iov_base = (char *) &csp;
            iov[1].iov_len = csp.lengthReason;
            iov[1].iov_base = (void *) NOROOM;
            iov[2].iov_len = (4 - (csp.lengthReason & 3)) & 3;
            iov[2].iov_base = pad;
            (void) _XSERVTransWritev(trans_conn, iov, 3);
        }
        RemoveNotifyFd(trans_conn->fd);
        _XSERVTransClose(trans_conn);
    
        Backoff = FALSE;
    }
    
    static void
    ErrorConnMax(XtransConnInfo trans_conn)
    {
        if (!SetNotifyFd(trans_conn->fd, ConnMaxNotify, X_NOTIFY_READ, trans_conn))
            _XSERVTransClose(trans_conn);
    }
    
    /************
     *   CloseDownFileDescriptor:
     *     Remove this file descriptor
     ************/
    
    void
    CloseDownFileDescriptor(OsCommPtr oc)
    {
        if (oc->trans_conn) {
            int connection = oc->fd;
    #ifdef XDMCP
            XdmcpCloseDisplay(connection);
    #endif
            ospoll_remove(server_poll, connection);
            _XSERVTransDisconnect(oc->trans_conn);
            _XSERVTransClose(oc->trans_conn);
            oc->trans_conn = NULL;
            oc->fd = -1;
        }
    }
    
    /*****************
     * CloseDownConnection
     *    Delete client from AllClients and free resources
     *****************/
    
    void
    CloseDownConnection(ClientPtr client)
    {
        OsCommPtr oc = (OsCommPtr) client->osPrivate;
    
        if (FlushCallback)
            CallCallbacks(&FlushCallback, client);
    
        if (oc->output)
    	FlushClient(client, oc, (char *) NULL, 0);
        CloseDownFileDescriptor(oc);
        FreeOsBuffers(oc);
        free(client->osPrivate);
        client->osPrivate = (void *) NULL;
        if (auditTrailLevel > 1)
            AuditF("client %d disconnected\n", client->index);
    }
    
    struct notify_fd {
        int mask;
        NotifyFdProcPtr notify;
        void *data;
    };
    
    /*****************
     * HandleNotifyFd
     *    A poll callback to be called when the registered
     *    file descriptor is ready.
     *****************/
    
    static void
    HandleNotifyFd(int fd, int xevents, void *data)
    {
        struct notify_fd *n = data;
        n->notify(fd, xevents, n->data);
    }
    
    /*****************
     * SetNotifyFd
     *    Registers a callback to be invoked when the specified
     *    file descriptor becomes readable.
     *****************/
    
    Bool
    SetNotifyFd(int fd, NotifyFdProcPtr notify, int mask, void *data)
    {
        struct notify_fd *n;
    
        n = ospoll_data(server_poll, fd);
        if (!n) {
            if (mask == 0)
                return TRUE;
    
            n = calloc(1, sizeof (struct notify_fd));
            if (!n)
                return FALSE;
            ospoll_add(server_poll, fd,
                       ospoll_trigger_level,
                       HandleNotifyFd,
                       n);
        }
    
        if (mask == 0) {
            ospoll_remove(server_poll, fd);
            free(n);
        } else {
            int listen = mask & ~n->mask;
            int mute = n->mask & ~mask;
    
            if (listen)
                ospoll_listen(server_poll, fd, listen);
            if (mute)
                ospoll_mute(server_poll, fd, mute);
            n->mask = mask;
            n->data = data;
            n->notify = notify;
        }
    
        return TRUE;
    }
    
    /*****************
     * OnlyListenToOneClient:
     *    Only accept requests from  one client.  Continue to handle new
     *    connections, but don't take any protocol requests from the new
     *    ones.  Note that if GrabInProgress is set, EstablishNewConnections
     *    needs to put new clients into SavedAllSockets and SavedAllClients.
     *    Note also that there is no timeout for this in the protocol.
     *    This routine is "undone" by ListenToAllClients()
     *****************/
    
    int
    OnlyListenToOneClient(ClientPtr client)
    {
        int rc;
    
        rc = XaceHook(XACE_SERVER_ACCESS, client, DixGrabAccess);
        if (rc != Success)
            return rc;
    
        if (!GrabInProgress) {
            GrabInProgress = client->index;
            set_poll_clients();
        }
    
        return rc;
    }
    
    /****************
     * ListenToAllClients:
     *    Undoes OnlyListentToOneClient()
     ****************/
    
    void
    ListenToAllClients(void)
    {
        if (GrabInProgress) {
            GrabInProgress = 0;
            set_poll_clients();
        }
    }
    
    /****************
     * IgnoreClient
     *    Removes one client from input masks.
     *    Must have corresponding call to AttendClient.
     ****************/
    
    void
    IgnoreClient(ClientPtr client)
    {
        OsCommPtr oc = (OsCommPtr) client->osPrivate;
    
        client->ignoreCount++;
        if (client->ignoreCount > 1)
            return;
    
        isItTimeToYield = TRUE;
        mark_client_not_ready(client);
    
        oc->flags |= OS_COMM_IGNORED;
        set_poll_client(client);
    }
    
    /****************
     * AttendClient
     *    Adds one client back into the input masks.
     ****************/
    
    void
    AttendClient(ClientPtr client)
    {
        OsCommPtr oc = (OsCommPtr) client->osPrivate;
    
        if (client->clientGone) {
            /*
             * client is gone, so any pending requests will be dropped and its
             * ignore count doesn't matter.
             */
            return;
        }
    
        client->ignoreCount--;
        if (client->ignoreCount)
            return;
    
        oc->flags &= ~OS_COMM_IGNORED;
        set_poll_client(client);
        if (listen_to_client(client))
            mark_client_ready(client);
        else {
            /* grab active, mark ready when grab goes away */
            mark_client_saved_ready(client);
        }
    }
    
    /* make client impervious to grabs; assume only executing client calls this */
    
    void
    MakeClientGrabImpervious(ClientPtr client)
    {
        OsCommPtr oc = (OsCommPtr) client->osPrivate;
    
        oc->flags |= OS_COMM_GRAB_IMPERVIOUS;
        set_poll_client(client);
    
        if (ServerGrabCallback) {
            ServerGrabInfoRec grabinfo;
    
            grabinfo.client = client;
            grabinfo.grabstate = CLIENT_IMPERVIOUS;
            CallCallbacks(&ServerGrabCallback, &grabinfo);
        }
    }
    
    /* make client pervious to grabs; assume only executing client calls this */
    
    void
    MakeClientGrabPervious(ClientPtr client)
    {
        OsCommPtr oc = (OsCommPtr) client->osPrivate;
    
        oc->flags &= ~OS_COMM_GRAB_IMPERVIOUS;
        set_poll_client(client);
        isItTimeToYield = TRUE;
    
        if (ServerGrabCallback) {
            ServerGrabInfoRec grabinfo;
    
            grabinfo.client = client;
            grabinfo.grabstate = CLIENT_PERVIOUS;
            CallCallbacks(&ServerGrabCallback, &grabinfo);
        }
    }
    
    /* Add a fd (from launchd or similar) to our listeners */
    void
    ListenOnOpenFD(int fd, int noxauth)
    {
        char port[PATH_MAX];
        XtransConnInfo ciptr;
        const char *display_env = getenv("DISPLAY");
    
        /* First check if display_env matches a <absolute path to unix socket>[.<screen number>] scheme (eg: launchd) */
        if (display_env && display_env[0] == '/') {
            struct stat sbuf;
    
            strlcpy(port, display_env, sizeof(port));
    
            /* If the path exists, we don't have do do anything else.
             * If it doesn't, we need to check for a .<screen number> to strip off and recheck.
             */
            if (0 != stat(port, &sbuf)) {
                char *dot = strrchr(port, '.');
                if (dot) {
                    *dot = '\0';
    
                    if (0 != stat(port, &sbuf)) {
                        display_env = NULL;
                    }
                } else {
                    display_env = NULL;
                }
            }
        }
    
        if (!display_env) {
            /* Just some default so things don't break and die. */
            snprintf(port, sizeof(port), ":%d", atoi(display));
        }
    
        /* Make our XtransConnInfo
         * TRANS_SOCKET_LOCAL_INDEX = 5 from Xtrans.c
         */
        ciptr = _XSERVTransReopenCOTSServer(5, fd, port);
        if (ciptr == NULL) {
            ErrorF("Got NULL while trying to Reopen listen port.\n");
            return;
        }
    
        if (noxauth)
            ciptr->flags = ciptr->flags | TRANS_NOXAUTH;
    
        /* Allocate space to store it */
        ListenTransFds =
            xnfreallocarray(ListenTransFds, ListenTransCount + 1, sizeof(int));
        ListenTransConns =
            xnfreallocarray(ListenTransConns, ListenTransCount + 1,
                            sizeof(XtransConnInfo));
    
        /* Store it */
        ListenTransConns[ListenTransCount] = ciptr;
        ListenTransFds[ListenTransCount] = fd;
    
        SetNotifyFd(fd, EstablishNewConnections, X_NOTIFY_READ, NULL);
    
        /* Increment the count */
        ListenTransCount++;
    }
    
    /* based on TRANS(SocketUNIXAccept) (XtransConnInfo ciptr, int *status) */
    Bool
    AddClientOnOpenFD(int fd)
    {
        XtransConnInfo ciptr;
        CARD32 connect_time;
        char port[20];
    
        snprintf(port, sizeof(port), ":%d", atoi(display));
        ciptr = _XSERVTransReopenCOTSServer(5, fd, port);
        if (ciptr == NULL)
            return FALSE;
    
        _XSERVTransSetOption(ciptr, TRANS_NONBLOCKING, 1);
        ciptr->flags |= TRANS_NOXAUTH;
    
        connect_time = GetTimeInMillis();
    
        if (!AllocNewConnection(ciptr, fd, connect_time)) {
            ErrorConnMax(ciptr);
            return FALSE;
        }
    
        return TRUE;
    }
    
    Bool
    listen_to_client(ClientPtr client)
    {
        OsCommPtr oc = (OsCommPtr) client->osPrivate;
    
        if (oc->flags & OS_COMM_IGNORED)
            return FALSE;
    
        if (!GrabInProgress)
            return TRUE;
    
        if (client->index == GrabInProgress)
            return TRUE;
    
        if (oc->flags & OS_COMM_GRAB_IMPERVIOUS)
            return TRUE;
    
        return FALSE;
    }
    
    static void
    set_poll_client(ClientPtr client)
    {
        OsCommPtr oc = (OsCommPtr) client->osPrivate;
    
        if (oc->trans_conn) {
            if (listen_to_client(client))
                ospoll_listen(server_poll, oc->trans_conn->fd, X_NOTIFY_READ);
            else
                ospoll_mute(server_poll, oc->trans_conn->fd, X_NOTIFY_READ);
        }
    }
    
    static void
    set_poll_clients(void)
    {
        int i;
    
        for (i = 1; i < currentMaxClients; i++) {
            ClientPtr client = clients[i];
            if (client && !client->clientGone)
                set_poll_client(client);
        }
    }