Initial commit

12 files changed, 1667 insertions, 0 deletions

diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..f9960f5
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,498 @@
+#include "userlist.h"
+#include "warn.h"
+#include "x11util.h"
+#include "util.h"
+#include "main.h"
+#include "rpc.h"
+
+#include <string.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <error.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <pwd.h>
+#include <getopt.h>
+
+#define CAP_SLEEP(newval) do { if ( (newval) < sleepTime ) sleepTime = (newval); } while (0)
+
+static time_t lastActivity;
+
+// Tracked user sessions
+#define USERS (50)
+static struct user *users;
+
+// List of reboot and shutdown times
+enum Shutdown {
+    REBOOT = 0,
+    POWEROFF,
+    KEXEC,
+    SUSPEND,
+    SHUTDOWN_ENUM_END,
+};
+static const char *shutdownActions[SHUTDOWN_ENUM_END] = {
+    [REBOOT] = "reboot",
+    [POWEROFF] = "poweroff",
+    [KEXEC] = "kexec",
+    [SUSPEND] = "suspend",
+};
+#define TABMAX (20)
+struct time {
+    int hour;
+    int minute;
+    enum Shutdown action;
+};
+static struct {
+    time_t deadline; // MONOTONIC; 0 = none, or last one was disarmed and time elapsed past deadline
+    enum Shutdown action;
+    bool disarmed;
+} nextAction;
+
+// Config via command line
+static struct {
+    char *shutdownCommand;
+    struct time shutdown[TABMAX];
+    int shutdowns;
+    int poweroffTimeout;
+    int logoutTimeout;
+    int suspendTimeout;
+    int saverTimeout;
+    int dpmsTimeout;
+    int gracePeriod;
+} config;
+
+static void getXAuthority( struct user *user );
+
+static bool parseCmdline( int argc, char **argv );
+
+static void execShutdown( enum Shutdown action );
+
+int main( int argc, char **argv )
+{
+    int idx;
+    time_t startWall, startMono, endWall, endMono;
+    init_time();
+    if ( ! parseCmdline( argc, argv ) )
+        return 2;
+    // Always line buffered output
+    setvbuf( stdout, NULL, _IOLBF, -BUFSIZ );
+    setvbuf( stderr, NULL, _IOLBF, -BUFSIZ );
+    if ( _testmode ) {
+        fprintf( stderr, "Test mode only!\n" );
+    }
+    users = calloc( USERS, sizeof(*users) );
+    nextAction.deadline = 0;
+    startWall = time( NULL );
+    startMono = now();
+    // Calculate shortest possible sleep time without delaying any timeout related actions
+    int defaultSleep = 900;
+    if ( config.logoutTimeout > 0 && config.logoutTimeout < defaultSleep ) {
+        defaultSleep = config.logoutTimeout;
+    }
+    if ( config.saverTimeout > 0 && config.saverTimeout < defaultSleep ) {
+        defaultSleep = config.saverTimeout;
+    }
+    if ( config.dpmsTimeout > 0 && config.dpmsTimeout < defaultSleep ) {
+        defaultSleep = config.dpmsTimeout;
+    }
+    int listenFd = rpcOpen();
+    if ( listenFd == -1 )
+        return 1;
+    lastActivity = now();
+    for ( ;; ) {
+        int sleepTime = defaultSleep;
+        const int count = getUserList( users, USERS );
+        for ( idx = 0; idx < count; ++idx ) {
+            struct user * const usr = &users[idx];
+            if ( !usr->mark ) {
+                fprintf( stderr, "This will never happen \\o/\n" );
+                continue;
+            }
+            const time_t NOW = time( NULL );
+            const time_t monoNOW = now();
+            if ( *usr->display ) {
+                // User has an X11 session going, get actual idle time
+                struct x11state screen;
+                getXAuthority( usr );
+                if ( !getX11IdleTimes( usr->xauth, usr->display, &screen ) ) {
+                    // Failed, assume active to be safe
+                    printf( "X11 query failed. Using NOW.\n ");
+                    usr->lastActivity = NOW;
+                    usr->lastActivityOffset = 0;
+                } else {
+                    // Fiddle and fumble
+                    usr->isLocked = ( screen.saverState == SAVER_LOCKED );
+                    if ( screen.lockTimestamp == 0 && ( NOW - usr->lockTime ) > 4 ) {
+                        // Session is not locked, unconditionally update timestamp
+                        if ( usr->lockTime != 0 ) {
+                            printf( "%s #### Session got unlocked.\n", usr->display );
+                        }
+                        usr->lockTime = 0;
+                        usr->lockTimeOffset = 0;
+                        usr->lastActivity = NOW - screen.idleSeconds;
+                        usr->lastActivityOffset = 0;
+                    } else if ( screen.lockTimestamp - usr->lockTime > 10 ) { // Allow for slight offset in case we manually set this
+                        // Session is locked
+                        printf( "%s #### Session got externally locked.\n", usr->display );
+                        usr->lockTime = screen.lockTimestamp;
+                        usr->lockTimeOffset = 0;
+                        if ( usr->lastActivity == 0 || usr->lockTime != 0 ) {
+                            // We have no activity log yet, or quickly unlocked and relocked -- update idle time
+                            usr->lastActivity = usr->lockTime;
+                            usr->lastActivityOffset = 0;
+                        }
+                    }
+                    const int idleTime = NOW - ( usr->lastActivity + usr->lastActivityOffset );
+                    if ( config.dpmsTimeout > 0 && screen.screenStandby != SCREEN_UNKNOWN ) {
+                        int want = SCREEN_UNKNOWN;
+                        if ( config.logoutTimeout > 0 && idleTime + 300 > config.logoutTimeout ) {
+                            want = SCREEN_ON;
+                        } else if ( ! nextAction.disarmed && nextAction.deadline != 0 && monoNOW - nextAction.deadline < 300 ) {
+                            want = SCREEN_ON;
+                        } else if ( idleTime > config.dpmsTimeout && screen.idleSeconds >= 60 ) {
+                            want = SCREEN_OFF;
+                        }
+                        if ( want != SCREEN_UNKNOWN && screen.screenStandby != want ) {
+                            printf( "#### Powering %s %s.\n", usr->display, want == SCREEN_ON ? "ON" : "OFF" );
+                            setScreenDpms( usr->xauth, usr->display, want );
+                        }
+                    }
+                    if ( config.saverTimeout > 0 ) {
+                        int want = SAVER_OFF;
+                        if ( config.gracePeriod >= 0 && idleTime > config.saverTimeout + config.gracePeriod
+                                && ( screen.saverState == SAVER_OFF || screen.saverState == SAVER_ACTIVE ) ) {
+                            want = SAVER_LOCKED;
+                        } else if ( idleTime > config.saverTimeout && screen.saverState == SAVER_OFF ) {
+                            want = SAVER_ACTIVE;
+                        } else if ( screen.saverState == SAVER_OFF ) {
+                            CAP_SLEEP( config.saverTimeout - idleTime );
+                        }
+                        if ( want != SAVER_OFF ) {
+                            enableScreenSaver( usr->xauth, usr->display, want );
+                            usr->lockTime = NOW;
+                            usr->lockTimeOffset = 0;
+                            if ( screen.screenStandby == SCREEN_OFF ) {
+                                // Screen was off before, but our ugly vmware ungrab hack might
+                                // have simulated input and woke up the screen - enable standby
+                                // again right away
+                                setScreenDpms( usr->xauth, usr->display, SCREEN_OFF );
+                            }
+                        }
+                    }
+                } // End X11 handling
+            }
+            //printf( "Have User %d: %s Locked %d (%+d) Idle %d (%+d) -- Leader: %d\n", idx, usr->user, (int)usr->lockTime, usr->lockTimeOffset, (int)usr->lastActivity, usr->lastActivityOffset, (int)usr->sessionLeader );
+            const int idleTime = NOW - usr->lastActivity;
+            // See if we need to shorten sleep time for a pending session kill
+            // or warn the user about an imminent session kill
+            // or whether the screen saver is supposed to activate
+            if ( config.logoutTimeout > 0 ) {
+                // Idle logout is enabled
+                const int remaining = config.logoutTimeout - idleTime;
+                if ( remaining <= 2 ) {
+                    killSession( usr );
+                } else if ( remaining <= 65 ) {
+                    warnUser( usr, WARN_LOGOUT, remaining );
+                    CAP_SLEEP( remaining );
+                } else if ( remaining < 310 ) {
+                    warnUser( usr, WARN_LOGOUT_LOW, remaining );
+                    CAP_SLEEP( remaining - ( ( remaining - 30 ) / 60 * 60 ) );
+                } else {
+                    CAP_SLEEP( remaining - 300 );
+                }
+                usr->logoutTime = NOW + remaining;
+            }
+            const time_t laMono = monoNOW - idleTime;
+            if ( laMono > lastActivity ) {
+                lastActivity = laMono;
+            }
+        } // End loop over users
+        const time_t monoNOW = now();
+        // See if any reboot or poweroff is due (if none is currently pending or still 5min+ away)
+        if ( config.shutdowns > 0 && ( nextAction.deadline == 0 || nextAction.deadline - monoNOW > 300 ) ) {
+            if ( nextAction.deadline != 0 && nextAction.deadline - monoNOW > 300 ) {
+                nextAction.deadline = 0;
+            }
+            const time_t NOW = time( NULL );
+            struct tm tmNOW;
+            if ( localtime_r( &NOW, &tmNOW ) != NULL ) {
+                struct tm dtime;
+                time_t deadline;
+                int delta;
+                for ( idx = 0; idx < config.shutdowns; ++idx ) {
+                    dtime = tmNOW;
+                    dtime.tm_hour = config.shutdown[idx].hour;
+                    dtime.tm_min = config.shutdown[idx].minute;
+                    dtime.tm_sec = 0;
+                    deadline = mktime( &dtime );
+                    if ( deadline + 6 < NOW ) {
+                        // Try again tomorrow
+                        dtime.tm_mday++;
+                        deadline = mktime( &dtime );
+                    }
+                    if ( deadline == -1 ) {
+                        perror( "Cannot convert shutdown entry to time_t via mktime" );
+                        continue;
+                    }
+                    delta = deadline - NOW;
+                    if ( delta >= -6 && ( nextAction.deadline == 0 || ( nextAction.deadline - monoNOW - 3 ) > delta ) ) {
+                        // Engage
+                        nextAction.deadline = monoNOW + ( delta < 0 ? 0 : delta );
+                        nextAction.disarmed = false;
+                        nextAction.action = config.shutdown[idx].action;
+                        if ( delta < 300 ) {
+                            printf( "Scheduling reboot/poweroff in %d seconds\n", delta );
+                        }
+                        CAP_SLEEP( delta );
+                    }
+                }
+            }
+        }
+        // Check unused idle time
+        if ( count == 0 ) {
+            if ( config.poweroffTimeout != 0 ) {
+                int delta = config.poweroffTimeout - ( monoNOW - lastActivity );
+                if ( delta <= 0 ) {
+                    execShutdown( POWEROFF );
+                } else {
+                    CAP_SLEEP( delta );
+                }
+            }
+            if ( config.suspendTimeout != 0 ) {
+                int delta = config.suspendTimeout - ( monoNOW - lastActivity );
+                if ( delta <= 0 ) {
+                    execShutdown( SUSPEND );
+                } else {
+                    CAP_SLEEP( delta );
+                }
+            }
+        }
+        if ( nextAction.deadline != 0 ) {
+            // Some action seems pending
+            const int remaining = nextAction.deadline - monoNOW;
+            if ( remaining < -60 ) {
+                if ( ! nextAction.disarmed ) {
+                    fprintf( stderr, "Missed planned action!? Late by %d seconds. Ignored.\n", remaining );
+                }
+                nextAction.deadline = 0;
+            } else if ( ! nextAction.disarmed ) {
+                if ( remaining <= 3 ) {
+                    // Execute!
+                    execShutdown( nextAction.action );
+                    nextAction.disarmed = true;
+                    if ( ! _testmode ) {
+                    }
+                } else if ( remaining < 310 ) {
+                    enum Warning w = WARN_REBOOT;
+                    if ( nextAction.action == POWEROFF ) {
+                        w = WARN_POWEROFF;
+                    }
+                    for ( idx = 0; idx < count; ++idx ) {
+                        warnUser( &users[idx], w, remaining );
+                    }
+                    CAP_SLEEP( remaining - ( ( remaining - 30 ) / 60 * 60 ) );
+                } else {
+                    CAP_SLEEP( remaining );
+                }
+            }
+        }
+        // Handle requests
+        rpcHandle( listenFd );
+        // Sleep until next run
+        //printf( "Sleeping %d seconds\n ", sleepTime );
+        rpcWait( listenFd, sleepTime > 5 ? sleepTime : 5 );
+        // Detect time changes
+        endWall = time( NULL );
+        endMono = now();
+        // Adjust for clock changes
+        const int diff = ( endWall - startWall ) - ( endMono - startMono );
+        if ( diff != 0 ) {
+            for ( idx = 0; idx < count; ++idx ) {
+                if ( users[idx].display[0] == '\0' )
+                    continue;
+                if ( users[idx].lockTime != 0 ) {
+                    users[idx].lockTimeOffset += diff;
+                }
+                users[idx].lastActivityOffset += diff;
+            }
+        }
+        startWall = endWall;
+        startMono = endMono;
+    }
+    return 0;
+}
+
+/**
+ * This doesn't really use any clever logic but rather assumes that
+ * it will be $HOME/.Xauthority
+ */
+static void getXAuthority( struct user *user )
+{
+    if ( user->xauth[0] != '\0' )
+        return;
+    char buffer[1000];
+    struct passwd p, *ok;
+    if ( getpwnam_r( user->user, &p, buffer, sizeof(buffer), &ok ) != 0 || ok == NULL ) {
+        user->xauth[0] = '-';
+        user->xauth[1] = '\0';
+        return;
+    }
+    // Got valid data
+    snprintf( user->xauth, AUTHLEN, "%s/.Xauthority", p.pw_dir );
+    struct stat foo;
+    if ( stat( user->xauth, &foo ) == -1 ) {
+        user->xauth[0] = '-';
+        user->xauth[1] = '\0';
+    }
+}
+
+// cmdline options. Only support long for now.
+static struct option long_options[] = {
+    { "reboot", required_argument, NULL, 'r' },
+    { "poweroff", required_argument, NULL, 'p' },
+    { "poweroff-timeout", required_argument, NULL, 'pot' },
+    { "suspend-timeout", required_argument, NULL, 'sbt' },
+    { "logout-timeout", required_argument, NULL, 'lot' },
+    { "screensaver-timeout", required_argument, NULL, 'sst' },
+    { "dpms-timeout", required_argument, NULL, 'dpms' },
+    { "grace-period", required_argument, NULL, 'gp' },
+    { "cmd", required_argument, NULL, 'cmd' },
+    { "test", no_argument, NULL, 't' },
+    { NULL, 0, NULL, 0 }
+};
+
+static bool parseTime( const char *str, struct time *result )
+{
+    char *next;
+    result->hour = (int)strtol( str, &next, 10 );
+    if ( result->hour < 0 || result->hour > 24 )
+        return false;
+    result->hour %= 24; // Allow 24:00
+    if ( *next != ':' )
+        return false;
+    result->minute = (int)strtol( next + 1, &next, 10 );
+    if ( result->minute < 0 || result->minute > 59 )
+        return false;
+    if ( *next != '\0' ) {
+        fprintf( stderr, "Ignoring trailing garbage after minute\n" );
+    }
+    return true;
+}
+
+/**
+ * Parse command line and fill all the tables / vars etc.
+ * Return false if command line is unparsable.
+ */
+static bool parseCmdline( int argc, char **argv )
+{
+    int ch;
+    config.shutdowns = 0;
+    config.logoutTimeout = 0;
+    config.poweroffTimeout = 0;
+    config.suspendTimeout = 0;
+    config.saverTimeout = 0;
+    config.dpmsTimeout = 0;
+    config.gracePeriod = -1;
+    config.shutdownCommand = NULL;
+    while ( ( ch = getopt_long( argc, argv, "", long_options, NULL ) ) != -1 ) {
+        switch ( ch ) {
+        case 'pot':
+            config.poweroffTimeout = atoi( optarg );
+            break;
+        case 'sbt':
+            config.suspendTimeout = atoi( optarg );
+            break;
+        case 'lot':
+            config.logoutTimeout = atoi( optarg );
+            break;
+        case 'sst':
+            config.saverTimeout = atoi( optarg );
+            break;
+        case 'dpms':
+            config.dpmsTimeout = atoi( optarg );
+            break;
+        case 'gp':
+            config.gracePeriod = atoi( optarg );
+            break;
+        case 'r':
+        case 'p':
+            if ( config.shutdowns < TABMAX ) {
+                if ( parseTime( optarg, &config.shutdown[config.shutdowns] ) ) {
+                    config.shutdown[config.shutdowns].action = ( ch == 'r' ? REBOOT : POWEROFF );
+                    config.shutdowns++;
+                } else {
+                    fprintf( stderr, "Could not parse shutdown time %s\n", optarg );
+                }
+            } else {
+                fprintf( stderr, "Ignoring shutdown time %s: Table full\n", optarg );
+            }
+            break;
+        case 't':
+            _testmode = 1;
+            break;
+        case 'cmd':
+            config.shutdownCommand = strdup( optarg );
+            break;
+        default:
+            fprintf( stderr, "Unhandled command line option %d, aborting\n", ch );
+            return false;
+        }
+    }
+    return true;
+}
+
+static void execShutdown( enum Shutdown action )
+{
+    if ( action < 0 && action >= SHUTDOWN_ENUM_END ) {
+        fprintf( stderr, "Invalid shutdown action %d\n", (int)action );
+        return;
+    }
+    if ( _testmode ) {
+        printf( "[dryrun] Not execution shutdown(%d)\n", (int)action );
+        return;
+    }
+    if ( config.shutdownCommand != NULL ) {
+        printf( "Executing shutdown via %s %s\n", config.shutdownCommand, shutdownActions[action] );
+        run( true, config.shutdownCommand, shutdownActions[action], (char*)NULL );
+        return;
+    }
+    // Builtin
+    printf( "Executing shutdown via builtin handler for %s\n", shutdownActions[action] );
+    switch ( action ) {
+    case REBOOT:
+    case POWEROFF:
+    case SUSPEND:
+        run( true, "systemctl", shutdownActions[action], (char*)NULL );
+        break;
+    case KEXEC:
+        run( true, "systemctl", "isolate", "kexec.target", (char*)NULL );
+        break;
+    default:
+        fprintf( stderr, "BUG! Unhandled shutdown action %d\n", (int)action );
+        break;
+    }
+}
+
+void main_getStatus( const char **nextString, time_t *deadline )
+{
+    if ( nextAction.deadline == 0 || nextAction.disarmed ) {
+        *deadline = 0;
+        return;
+    }
+    *deadline = ( nextAction.deadline - now() ) + time( NULL );
+    *nextString = shutdownActions[nextAction.action];
+}
+
+struct user* main_getUser( const char *terminal )
+{
+    for ( int i = 0; i < USERS && users[i].mark; ++i ) {
+        if ( strcmp( users[i].device, terminal ) == 0
+                || strcmp( users[i].display, terminal ) == 0 ) {
+            return &users[i];
+        }
+    }
+    return NULL;
+}
+
diff --git a/src/main.h b/src/main.h
new file mode 100644
index 0000000..1ff924a
--- /dev/null
+++ b/src/main.h
@@ -0,0 +1,10 @@
+#ifndef _MAIN_H_
+#define _MAIN_H_
+
+#include <time.h>
+
+void main_getStatus( const char **nextAction, time_t *deadline );
+
+struct user* main_getUser( const char *terminal );
+
+#endif
diff --git a/src/rpc.c b/src/rpc.c
new file mode 100644
index 0000000..e49547e
--- /dev/null
+++ b/src/rpc.c
@@ -0,0 +1,132 @@
+#include "rpc.h"
+#include "util.h"
+#include "main.h"
+#include "userlist.h"
+
+#include <poll.h>
+#include <sys/types.h>  
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/un.h>
+#include <stdio.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+#define SOCKPATH "/run/idle-daemon"
+
+static void handleClient( int fd, struct ucred *user );
+
+int rpcOpen()
+{
+	int fd = socket( AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0 );
+	if ( fd == -1 ) {
+		perror( "Cannot create local RPC socket" );
+		return -1;
+	}
+	struct sockaddr_un address = {
+		.sun_family = AF_UNIX,
+		.sun_path = SOCKPATH,
+	};
+	unlink( SOCKPATH );
+	if ( bind( fd, (struct sockaddr *)&address, sizeof(address) ) == -1 ) {
+		perror( "Could not bind RPC socket" );
+		close( fd );
+		return -1;
+	}
+	chmod( SOCKPATH, 0777 );
+	if ( listen( fd, 10 ) == -1 ) {
+		perror( "Could not listen() on RPC socket" );
+		close( fd );
+		return -1;
+	}
+	return fd;
+}
+
+void rpcWait( int listenFd, int seconds )
+{
+	waitRead( listenFd, seconds * 1000 );
+}
+
+void rpcHandle( int listenFd )
+{
+	int fd;
+	while ( ( fd = accept( listenFd, NULL, NULL ) ) != -1 ) {
+		// Determine who connected
+		socklen_t len;
+		struct ucred ucred;
+		len = sizeof(struct ucred);
+		if ( getsockopt( fd, SOL_SOCKET, SO_PEERCRED, &ucred, &len ) == -1 ) {
+			perror( "Could not get credentials of connection" );
+			close( fd ); // TODO: Allow more for root (eg. cancel reboot/poweroff)
+			continue;
+		}
+		if ( ! doublefork() )
+			continue; // Parent continues
+		handleClient( fd, &ucred );
+		exit( 0 );
+	}
+	if ( errno != EAGAIN && errno != EWOULDBLOCK ) {
+		perror( "accept() on RPC socket failed" );
+	}
+}
+
+static void handleClient( int fd, struct ucred *user )
+{
+	//printf( "Credentials from SO_PEERCRED: pid=%ld, euid=%ld, egid=%ld\n",
+	//	(long) ucred.pid, (long) ucred.uid, (long) ucred.gid );
+	// Make socket blocking (should be default on linux after accept() but...)
+	(void)user;
+	int flags = fcntl( fd, F_GETFL, 0 );
+	if ( flags != -1 ) {
+		fcntl( fd, F_SETFL, flags & ~O_NONBLOCK );
+	}
+	// But set timeouts
+	struct timeval tv = {
+		.tv_sec = 2,
+	};
+	setsockopt( fd, SOL_SOCKET, SO_RCVTIMEO, (const char*)&tv, sizeof(tv) );
+	setsockopt( fd, SOL_SOCKET, SO_SNDTIMEO, (const char*)&tv, sizeof(tv) );
+	// Now read request
+	char buffer[1000];
+	ssize_t len = read( fd, buffer, sizeof(buffer) - 1 );
+	if ( len <= 0 )
+		return;
+	buffer[len] = '\0';
+	if ( strncmp( buffer, "get", 3 ) != 0 ) {
+		write( fd, "error", 5 );
+	} else {
+		// Get request
+		FILE *s = fdopen( fd, "w" );
+		if ( s == NULL ) {
+			perror( "Cannot wrap socket in stream" );
+			return;
+		}
+		// 1) Global state
+		time_t deadline;
+		const char *name = "none";
+		main_getStatus( &name, &deadline );
+		fprintf( s, "[General]\n"
+				"nextAction=%s\n"
+				"nextActionTime=%lld\n",
+				name, (long long)deadline );
+		// 2) Requested sessions
+		char *tok = strtok( buffer + 4, " \t\n\r" );
+		while ( tok != NULL ) {
+			struct user *user = main_getUser( tok );
+			if ( user != NULL ) {
+				fprintf( s, "[%s]\n"
+						"logoutTime=%lld\n"
+						"locked=%d\n",
+						tok, (long long)user->logoutTime, (int)user->isLocked );
+			}
+			tok = strtok( NULL, " \t\n\r" );
+		}
+		fflush( s );
+	}
+	shutdown( fd, SHUT_WR );
+	read( fd, buffer, sizeof(buffer) );
+	close( fd );
+}
+
diff --git a/src/rpc.h b/src/rpc.h
new file mode 100644
index 0000000..08e08cd
--- /dev/null
+++ b/src/rpc.h
@@ -0,0 +1,10 @@
+#ifndef _RPC_H__
+#define _RPC_H__
+
+int rpcOpen();
+
+void rpcHandle( int listenFd );
+
+void rpcWait( int listenFd, int seconds );
+
+#endif
diff --git a/src/userlist.c b/src/userlist.c
new file mode 100644
index 0000000..6e1f3d2
--- /dev/null
+++ b/src/userlist.c
@@ -0,0 +1,232 @@
+#include "userlist.h"
+#include "util.h"
+
+
+#include <stdlib.h>
+#include <utmp.h>
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <time.h>
+#include <ctype.h>
+#include <signal.h>
+
+#define TRUE 1
+#define FALSE 0
+#define MIN(a,b) ((a) < (b) ? (a) : (b))
+
+static void getSessionData( struct user * user );
+
+static void fixString( char *buffer, int maxLen )
+{
+    while ( *buffer != '\0' && maxLen-- > 1 ) {
+        if ( *buffer == ' ' || *buffer == '\t' || *buffer == '\r' || *buffer == '\n' ) {
+            *buffer = '_';
+        }
+        buffer++;
+    }
+    *buffer = '\0';
+}
+
+static time_t lastActivity( char *line ) {
+    struct stat s;
+    char dev[40];
+    snprintf( dev, sizeof(dev), "/dev/%s", line );
+    if ( stat( dev, &s ) != 0 || s.st_atime == 0 )
+        return -1;
+    return s.st_atime;
+}
+
+int getUserList( struct user *outbuf, int size )
+{
+    int fh = open( "/run/utmp", O_RDONLY );
+    if ( fh == -1 )
+        return 0;
+    // Mark
+    int deadzone = 0;
+    for ( int i = 0; i < size; ++i ) {
+        if ( outbuf[i].user[0] != '\0' ) {
+            deadzone = i + 1;
+        }
+        outbuf[i].mark = false;
+    }
+    struct utmp buffer[100];
+    ssize_t len = read( fh, buffer, sizeof(buffer) );
+    int num = len / sizeof(struct utmp);
+    for ( int i = 0; i < num; ++i ) {
+        struct utmp *u = buffer + i;
+        if ( u->ut_type != USER_PROCESS )
+            continue; // Not user session
+        if ( u->ut_user[0] == '\0' )
+            continue; // Empty username!?
+        // Check if alive
+        if ( kill( u->ut_pid, 0 ) != 0 )
+            continue;
+        // Make sure these contain anything
+        if ( u->ut_line[0] == '\0' ) {
+            snprintf( u->ut_line, UT_LINESIZE, "-" );
+        }
+        if ( u->ut_host[0] == '\0' ) {
+            snprintf( u->ut_host, UT_HOSTSIZE, "-" );
+        }
+        // No spaces, null terminated
+        fixString( u->ut_user, UT_NAMESIZE );
+        fixString( u->ut_line, UT_LINESIZE );
+        fixString( u->ut_host, UT_HOSTSIZE );
+        // Find slot in outbuf (matching one, first free one if not found)
+        int use = -1;
+        for ( int j = 0; j < deadzone; ++j ) {
+            if ( outbuf[j].user[0] == '\0' ) {
+                if ( use == -1 ) {
+                    use = j;
+                }
+            } else if ( outbuf[j].sessionLeader == u->ut_pid
+                    && strcmp( outbuf[j].user, u->ut_user ) == 0
+                    && strcmp( outbuf[j].device, u->ut_line ) == 0 ) {
+                use = j;
+                break;
+            }
+        }
+        if ( use == -1 ) { // Not found and no free slot, expand if possible
+            if ( deadzone >= size ) // No more slots :-/
+                continue;
+            use = deadzone++;
+        }
+        if ( outbuf[use].user[0] == '\0' ) {
+            // New entry, init
+            memset( &outbuf[use], 0, sizeof(outbuf[use]) );
+            snprintf( outbuf[use].user, STRLEN, "%.*s",
+                    (int)MIN( UT_NAMESIZE, STRLEN-1 ), u->ut_user );
+            snprintf( outbuf[use].device, STRLEN, "%.*s",
+                    (int)MIN( UT_LINESIZE, STRLEN-1 ), u->ut_line );
+            if ( u->ut_host[0] == ':' && isdigit( u->ut_host[1] ) ) {
+                snprintf( outbuf[use].display, STRLEN, "%.*s",
+                        (int)MIN( UT_HOSTSIZE, STRLEN-1 ), u->ut_host );
+            }
+            outbuf[use].sessionLeader = u->ut_pid;
+            getSessionData( &outbuf[use] );
+            printf( "New Session: '%s' on '%s', Display '%s', logind session '%s', login pid '%d', utmp pid '%d'.\n", outbuf[use].user, outbuf[use].device, outbuf[use].display, outbuf[use].sessionName, (int)outbuf[use].sessionHead, (int)outbuf[use].sessionLeader );
+        }
+        outbuf[use].mark = true;
+        // Reset offset if timestamp changed
+        // but ONLY if this isn't a known X session
+        if ( outbuf[use].display[0] == '\0' ) {
+            const time_t la = lastActivity( outbuf[use].device );
+            if ( outbuf[use].lastActivity != la ) {
+                outbuf[use].lastActivity = la;
+                outbuf[use].lastActivityOffset = 0;
+            }
+        }
+    }
+    close( fh );
+    // Compact
+    for ( int i = 0; i < deadzone; ++i ) {
+        if ( outbuf[i].mark )
+            continue; // In use
+        do {
+            deadzone--;
+            if ( outbuf[deadzone].mark ) {
+                outbuf[i] = outbuf[deadzone];
+                outbuf[deadzone].user[0] = '\0';
+                break;
+            }
+        } while ( deadzone > i );
+    }
+    return deadzone;
+}
+
+static void getSessionData( struct user * user )
+{
+    char buffer[500];
+    snprintf( buffer, sizeof(buffer), "/proc/%d/cgroup", (int)user->sessionLeader );
+    FILE *fh = fopen( buffer, "r" );
+    if ( fh == NULL ) {
+        fprintf( stderr, "getSessionData: Cannot open %s to get logind session name\n", buffer );
+        return;
+    }
+    // Read from cgroup file
+    user->sessionName[0] = '\0';
+    char sessionName[40] = "";
+    while ( fgets( buffer, sizeof(buffer), fh ) != NULL ) {
+        const char *p = strstr( buffer, ":name=systemd:" );
+        if ( p == NULL )
+            continue;
+        p = strstr( p + 14, "/session-" );
+        if ( p == NULL )
+            continue;
+        copy( p + 9, sessionName, sizeof(sessionName), ".\n" );
+        break;
+    }
+    fclose( fh );
+    // Extract session leader pid from loginctl - it's often different from what utmp says
+    int fds[2];
+    if ( pipe( fds ) == -1 ) {
+        perror( "getSessionData: pipe for loginctl failed" );
+        return;
+    }
+    if ( doublefork() ) {
+        close( fds[0] );
+        redirect( -1, fds[1] );
+        run( false, "loginctl", "-p", "Name", "-p", "Class", "-p", "Leader", "show-session", sessionName, (char*)NULL );
+    }
+    close( fds[1] );
+    char lcName[100] = "", lcClass[100] = "", lcLeader[100] = "";
+    if ( ! waitRead( fds[0], 2000 ) ) {
+        fprintf( stderr, "getSessionData: loginctl timed out.\n" );
+    } else {
+        char output[4000] = "\n";
+        char *pos = output + 1, *end = output + sizeof(output) - 1;
+        do {
+            ssize_t ret = read( fds[0], pos, end - pos );
+            if ( ret == -1 ) {
+                if ( errno == EINTR )
+                    continue;
+                perror( "getSessionData: read() from loginctl failed" );
+                break;
+            }
+            if ( ret == 0 )
+                break;
+            pos += ret;
+        } while ( waitRead( fds[0], 50 ) && pos < end );
+        *pos = '\0';
+        // Find strings
+        pos = strstr( output, "\nName=" );
+        if ( pos != NULL ) {
+            copy( pos + 6, lcName, sizeof(lcName), "\n \t" );
+        }
+        pos = strstr( output, "\nClass=" );
+        if ( pos != NULL ) {
+            copy( pos + 7, lcClass, sizeof(lcClass), "\n \t" );
+        }
+        pos = strstr( output, "\nLeader=" );
+        if ( pos != NULL ) {
+            copy( pos + 8, lcLeader, sizeof(lcLeader), "\n \t" );
+        }
+    }
+    close( fds[0] );
+    // Eval what we got - only honor output if it makes sense
+    if ( *lcName == '\0' ) {
+        fprintf( stderr, "getSessionData: Could not get user name for session %s\n", sessionName );
+        return;
+    }
+    if ( strcmp( lcName, user->user ) != 0 ) {
+        fprintf( stderr, "getSessionData: Sanity check failed. Session %s belongs to %s, but expected %s.\n", sessionName, lcName, user->user );
+        return;
+    }
+    if ( *lcClass != '\0' && strcmp( lcClass, "user" ) != 0 ) {
+        fprintf( stderr, "killSession: Sanity check failed. Session %s has Class=%s, but expected user.\n", sessionName, lcClass );
+        return;
+    }
+    // All good
+    snprintf( user->sessionName, sizeof(user->sessionName), "%s", sessionName );
+    user->sessionHead = atol( lcLeader );
+    if ( user->sessionHead < 10 ) {
+        fprintf( stderr, "getSessionData: Nonsensical Leader=%s reported by loginctl for session %s.\n", lcLeader, sessionName );
+        user->sessionHead = 0;
+    }
+}
+
diff --git a/src/userlist.h b/src/userlist.h
new file mode 100644
index 0000000..c0ffc2f
--- /dev/null
+++ b/src/userlist.h
@@ -0,0 +1,31 @@
+#ifndef _USER_LIST_H_
+#define _USER_LIST_H_
+
+#include <time.h>
+#include <stdbool.h>
+
+#define STRLEN (40)
+#define AUTHLEN (128)
+
+struct user {
+    time_t lastActivity;
+    time_t lockTime;
+    time_t lastWarn;
+    time_t logoutTime;
+    pid_t sessionLeader;
+    pid_t sessionHead;
+    int lastWarnLevel;
+    int lastActivityOffset;
+    int lockTimeOffset;
+    bool mark;
+    bool isLocked;
+    char user[STRLEN];
+    char device[STRLEN];
+    char display[STRLEN];
+    char sessionName[STRLEN];
+    char xauth[AUTHLEN];
+};
+
+int getUserList( struct user *outbuf, int numElements );
+
+#endif
diff --git a/src/util.c b/src/util.c
new file mode 100644
index 0000000..e9d642c
--- /dev/null
+++ b/src/util.c
@@ -0,0 +1,187 @@
+#include "util.h"
+#include "userlist.h"
+
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdarg.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/stat.h>
+#include <signal.h>
+#include <pwd.h>
+#include <poll.h>
+
+int _testmode = 0;
+
+// Base time for monotonic clock
+static struct timespec basetime;
+
+time_t now()
+{
+    struct timespec retval;
+    if ( clock_gettime( CLOCK_MONOTONIC, &retval ) == -1 ) {
+        perror( "Cannot clock_gettime CLOCK_MONOTONIC" );
+        abort();
+    }
+    return (time_t)( retval.tv_sec - basetime.tv_sec );
+}
+
+void init_time()
+{
+    if ( clock_gettime( CLOCK_MONOTONIC, &basetime ) == -1 ) {
+        perror( "cannot clock_gettime CLOCK_MONOTONIC" );
+        basetime.tv_sec = 0; // Hope it doesn't overflow
+    }
+}
+
+/**
+ * Return false = parent, true = second child
+ */
+bool doublefork()
+{
+    const pid_t c1 = fork();
+    if ( c1 == -1 ) {
+        perror( "doublefork: First fork failed" );
+        return false;
+    }
+    if ( c1 != 0 ) {
+        // Parent (main program)
+        int ws;
+        while ( waitpid( c1, &ws, 0 ) == -1 && errno == EINTR ) {}
+        return false;
+    }
+    // This is executed by first child
+    signal( SIGCHLD, SIG_IGN );
+    // Fork again
+    const pid_t c2 = fork();
+    if ( c2 == -1 ) {
+        perror( "doublefork: Second fork failed" );
+        abort();
+    }
+    if ( c2 != 0 ) {
+        // Second parent (first child), exit immediately
+        exit( 0 );
+    }
+    // Second child, this is what we want
+    signal( SIGCHLD, SIG_DFL );
+    return true;
+}
+
+bool waitRead( int fd, int ms )
+{
+    struct pollfd pd = { .fd = fd, .events = POLLIN | POLLHUP | POLLRDHUP };
+    return poll( &pd, 1, ms ) > 0 && ( pd.revents & POLLIN ) != 0;
+}
+
+void copy( const char *src, char *dst, size_t len, const char *stop )
+{
+    const char *end = src + len - 1;
+    while ( src < end && *src != '\0' && ( stop == NULL || strchr( stop, *src ) == NULL ) ) {
+        *dst++ = *src++;
+    }
+    *dst = '\0';
+}
+
+void killSession( const struct user * user )
+{
+    if ( _testmode ) {
+        printf( "Not really killing session %s of user %s.\n", user->sessionName, user->user );
+        return;
+    }
+    if ( ! doublefork() )
+        return;
+    // Async do NOT use return from here on
+    if ( user->sessionName[0] != '\0' ) {
+        printf( "Terminating session %s of %s.\n", user->sessionName, user->user );
+        run( true, "loginctl", "terminate-session", user->sessionName );
+        sleep( 5 );
+        if ( kill( user->sessionLeader, 0 ) == -1
+                && ( user->sessionHead == 0 || kill( user->sessionHead, 0 ) == -1 ) )
+            exit( 0 );
+    }
+    if ( user->sessionHead != 0 && kill( user->sessionHead, SIGTERM ) == 0 ) {
+        printf( "Session %s seems not entirely dead, TERMing loginpid %d...\n", user->sessionName, (int)user->sessionHead );
+        sleep( 2 );
+    }
+    if ( ( killpg( user->sessionLeader, SIGTERM ) & kill( user->sessionLeader, SIGTERM ) ) == 0 ) {
+        printf( "Session %s seems not entirely dead, TERMing process group %d...\n", user->sessionName, (int)user->sessionLeader );
+        sleep( 3 );
+    }
+    // Maybe we need KILL now...
+    if ( user->sessionHead != 0 && kill( user->sessionHead, SIGKILL ) == 0 ) {
+        printf( "Session %s seems not entirely dead, KILLing %d...\n", user->sessionName, (int)user->sessionHead );
+    }
+    exit( 0 );
+}
+
+void redirect( int newIn, int newOut )
+{
+    if ( newIn > 2 ) {
+        dup2( newIn, STDIN_FILENO );
+        close( newIn );
+    }
+    if ( newOut > 2 ) {
+        dup2( newOut, STDOUT_FILENO );
+        close( newOut );
+    }
+}
+
+void switchUserSafe( const char* user )
+{
+    errno = 0;
+    struct passwd *u = getpwnam( user );
+    if ( u == NULL ) {
+        if ( errno != 0 ) {
+            perror( "switchUserSafe: Cannot switch to user" );
+        } else {
+            fprintf( stderr, "switchUserSafe: Cannot switch to user %s: User not known.\n", user );
+        }
+        exit( 1 );
+    }
+    chdir( "/" );
+    if ( setgid( u->pw_gid ) != 0 ) {
+        perror( "switchUserSafe: setgid failed" );
+        exit( 1 );
+    }
+    if ( setuid( u->pw_uid ) != 0 ) {
+        perror( "switchUserSafe: setuid failed" );
+        exit( 1 );
+    }
+    if ( u->pw_dir == NULL ) {
+        unsetenv( "HOME" );
+    } else {
+        setenv( "HOME", u->pw_dir, 1 );
+    }
+    setenv( "USER", u->pw_name, 1 );
+}
+
+void run( bool detach, const char *file, ... )
+{
+    if ( detach && ! doublefork() )
+        return;
+    char *argv[100];
+    argv[0] = strdup( file );
+    argv[99] = NULL;
+    va_list ap;
+    va_start( ap, file );
+    for ( int i = 1; i < 99; ++i ) {
+        argv[i] = va_arg( ap, char* );
+        if ( argv[i] == NULL )
+            break;
+        argv[i] = strdup( argv[i] );
+    }
+    va_end( ap );
+    printf( "Running: '%s'", file );
+    for ( int i = 0; i < 100 && argv[i] != NULL; ++i ) {
+        printf( " '%s'", argv[i] );
+    }
+    printf( "\n" );
+    execvp( strdup( file ), argv );
+    // Something went wrong...
+    perror( "run execvp failed" );
+    exit( 1 );
+}
+
diff --git a/src/util.h b/src/util.h
new file mode 100644
index 0000000..2c3bc51
--- /dev/null
+++ b/src/util.h
@@ -0,0 +1,30 @@
+#ifndef _UTIL_H_
+#define _UTIL_H_
+
+#include <time.h>
+#include <stdbool.h>
+
+extern int _testmode;
+
+struct user;
+
+// Get monotonic clock (seconds)
+time_t now();
+
+void init_time();
+
+bool doublefork();
+
+bool waitRead( int fd, int ms );
+
+void copy( const char *src, char *dst, size_t len, const char *stop );
+
+void killSession( const struct user * user );
+
+void redirect( int newIn, int newOut );
+
+void switchUserSafe( const char* user );
+
+void run( bool detach, const char *file, ... );
+
+#endif
diff --git a/src/warn.c b/src/warn.c
new file mode 100644
index 0000000..6dfd427
--- /dev/null
+++ b/src/warn.c
@@ -0,0 +1,86 @@
+#include "warn.h"
+#include "util.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+struct action {
+	const char *message;
+	const char *title;
+	int level;
+};
+
+static struct action actions[WARN_ENUM_END] = {
+	[WARN_REBOOT] = {
+		.level = 50,
+		.title = "Neustart des Rechners",
+		.message = 
+		"Dieser PC wird in %02d:%02d neu gestartet. Bitte speichern Sie Ihre Arbeit und beenden Sie die Sitzung.\n\n"
+		"This Computer will reboot in %02d:%02d. Please save your work and end the session."
+	},
+	[WARN_POWEROFF] = {
+		.level = 50,
+		.title = "Herunterfahren des Rechners",
+		.message =
+		"Dieser PC wird in %02d:%02d heruntergefahren. Bitte speichern Sie Ihre Arbeit und beenden Sie die Sitzung.\n\n"
+		"This Computer will power down in %02d:%02d. Please save your work and end the session."
+	},
+	[WARN_LOGOUT] = {
+		.level = 40,
+		.title = "Inaktivität",
+		.message =
+		"Diese Sitzung scheint inaktiv und wird bei weiterer Inaktivität in %02d:%02d beendet.\n\n"
+		"This session seems inactive and will be killed in %02d:%02d if no further activity is detected."
+	},
+	[WARN_LOGOUT_LOW] = {
+		.level = 30,
+		.title = "Inaktivität",
+		.message =
+		"Diese Sitzung scheint inaktiv und wird bei weiterer Inaktivität in %02d:%02d beendet.\n\n"
+		"This session seems inactive and will be killed in %02d:%02d if no further activity is detected."
+	},
+};
+
+void warnUser( struct user *usr, enum Warning what, int seconds )
+{
+	const time_t NOW = now();
+	if ( what < 0 || what >= WARN_ENUM_END )
+		return; // Invalid!
+	struct action *warning = &actions[what];
+	if ( usr->lastWarn + 30 > NOW && warning->level <= usr->lastWarnLevel )
+		return; // Ignore
+	usr->lastWarn = NOW;
+	usr->lastWarnLevel = warning->level;
+	if ( seconds > 60 ) {
+		seconds = ( seconds / 10 ) * 10;
+	}
+	int minutes = seconds / 60;
+	seconds %= 60;
+	char buffer[1000];
+	snprintf( buffer, sizeof(buffer), warning->message, minutes, seconds, minutes, seconds );
+	// Text or X11 warning
+	if ( *usr->display ) {
+		// notify-send
+		if ( doublefork() ) {
+			switchUserSafe( usr->user );
+			setenv( "DISPLAY", usr->display, 1 );
+			if ( usr->xauth[0] != '\0' && usr->xauth[0] != '-' ) {
+				setenv( "XAUTHORITY", usr->xauth, 1 );
+			}
+			run( false, "notify-send", "-t", "15000", warning->title, buffer, (char*)NULL );
+		}
+	} else {
+		// write to device
+		char dev[100];
+		snprintf( dev, sizeof(dev), "/dev/%s", usr->device );
+		FILE *fh = fopen( dev, "w" );
+		if ( fh == NULL )
+			return;
+		fputs( "\n\n****************************\n", fh );
+		fputs( warning->title, fh );
+		fputs( "\n****************************\n", fh );
+		fputs( buffer, fh );
+		fputs( "\n****************************\n\n", fh );
+		fclose( fh );
+	}
+}
+
diff --git a/src/warn.h b/src/warn.h
new file mode 100644
index 0000000..c414378
--- /dev/null
+++ b/src/warn.h
@@ -0,0 +1,18 @@
+#ifndef _WARN_H_
+#define _WARN_H_
+
+#include "userlist.h"
+
+enum Warning
+{
+	WARN_REBOOT = 0,
+	WARN_POWEROFF,
+	WARN_LOGOUT,
+	WARN_LOGOUT_LOW,
+	WARN_ENUM_END,
+};
+
+void warnUser( struct user *usr, enum Warning what, int seconds );
+
+#endif
+
diff --git a/src/x11util.c b/src/x11util.c
new file mode 100644
index 0000000..18e2fe4
--- /dev/null
+++ b/src/x11util.c
@@ -0,0 +1,405 @@
+#include "x11util.h"
+#include "util.h"
+
+#include <X11/Xlib.h>
+#include <X11/Xatom.h>
+#include <X11/Xutil.h>
+#include <X11/extensions/dpms.h>
+#include <X11/extensions/scrnsaver.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+
+static XErrorHandler old_handler = 0;
+
+static int runClient( const char *display, int fd );
+
+static void getLockState( Display *dpy, struct x11state *state );
+
+static Window getScreenSaverWindow( Display *dpy );
+
+static Window find_screensaver_window( Display *dpy, char **version );
+
+bool getX11IdleTimes( const char *xauth, const char *display, struct x11state *state )
+{
+    int fds[2];
+    if ( pipe( fds ) == -1 ) {
+        perror( "Could not create pipe for X11 stuff" );
+        return false;
+    }
+    if ( doublefork() ) {
+        // The child
+        close( fds[0] );
+        if ( xauth[0] != '\0' && strcmp( xauth, "-" ) != 0 ) {
+            setenv( "XAUTHORITY", xauth, 1 );
+        }
+        int ret = runClient( display, fds[1] );
+        close( fds[1] );
+        exit( ret );
+    }
+    // Parent -- wait
+    bool ok = false;
+    close( fds[1] );
+    if ( ! waitRead( fds[0], 1000 ) ) {
+        fprintf( stderr, "X11 child didn't write to pipe in time\n" );
+    } else {
+        // We should be able to read a reply
+        if ( read( fds[0], state, sizeof(*state) ) != sizeof(*state) ) {
+            fprintf( stderr, "X11 child wrote partial data\n" );
+        } else {
+            ok = true;
+        }
+    }
+    close( fds[0] );
+    return ok;
+}
+
+static int printErrorHandler( Display *dpy, XErrorEvent *error )
+{
+    char msg[500] = {0};
+
+    XGetErrorText( dpy, error->error_code, msg, sizeof(msg) );
+    fprintf( stderr, "X11 Error %d: %s\n", (int)error->error_code, msg );
+
+    if( !old_handler ) {
+        abort();
+    }
+    return ( *old_handler )( dpy, error );
+}
+
+static void setScreenDpmsFork( const char *xauth, const char *display, int mode )
+{
+    Display *dpy;
+    int dummy;
+
+    if ( xauth[0] != '\0' && strcmp( xauth, "-" ) != 0 ) {
+        setenv( "XAUTHORITY", xauth, 1 );
+    }
+    dpy = XOpenDisplay( display );
+    if ( dpy == NULL ) {
+        fprintf( stderr, "setScreenDpms: Cannot open display\n" );
+        return;
+    }
+    if ( ! DPMSQueryExtension( dpy, &dummy, &dummy ) || ! DPMSCapable( dpy ) ) {
+        fprintf( stderr, "%s doesn't support DPMS.\n", display );
+        return;
+    }
+    //DPMSInfo( dpy, &dummy, &onoff );
+    old_handler = XSetErrorHandler( printErrorHandler );
+    DPMSForceLevel( dpy, mode == SCREEN_ON ? DPMSModeOn : DPMSModeSuspend );
+    XSync( dpy, False );
+    XSetErrorHandler( old_handler );
+    old_handler = 0;
+    XCloseDisplay( dpy );
+}
+
+void setScreenDpms( const char *xauth, const char *display, int mode )
+{
+    if ( _testmode ) {
+        printf( "Testmode: Not setting screen to %d\n", mode );
+        return;
+    }
+    if ( ! doublefork() )
+        return;
+    sleep( 2 ); // Sleep a bit in case this was called right after enabling the screen saver
+    setScreenDpmsFork( xauth, display, mode );
+    exit( 0 );
+}
+
+static void enableScreenSaverFork( const char *xauth, const char *display, const int state )
+{
+    if ( xauth[0] != '\0' && strcmp( xauth, "-" ) != 0 ) {
+        setenv( "XAUTHORITY", xauth, 1 );
+    }
+    Display *dpy;
+    Atom XA_SCREENSAVER;
+    Atom XA_ACTION;
+
+    dpy = XOpenDisplay( display );
+    if ( dpy == NULL ) {
+        fprintf( stderr, "enableScreenSaver: Cannot open display %s\n", display );
+        return;
+    }
+
+    Window window = getScreenSaverWindow( dpy );
+    if( ! window )
+        return;
+
+    XA_SCREENSAVER = XInternAtom( dpy, "SCREENSAVER", False );
+    if ( state == SAVER_LOCKED ) {
+        XA_ACTION = XInternAtom( dpy, "LOCK", False );
+    } else {
+        XA_ACTION = XInternAtom( dpy, "ACTIVATE", False );
+    }
+    /*
+    XEvent event = {
+        .xany.type = ClientMessage,
+        .xclient.display = dpy,
+        .xclient.window = window,
+        .xclient.message_type = XA_SCREENSAVER,
+        .xclient.format = 32,
+        .xclient.data.l[0] = (long) XA_ACTION,
+    };
+    */
+    XEvent event;
+    event.xany.type = ClientMessage;
+    event.xclient.display = dpy;
+    event.xclient.window = window;
+    event.xclient.message_type = XA_SCREENSAVER;
+    event.xclient.format = 32;
+    memset (&event.xclient.data, 0, sizeof(event.xclient.data));
+    event.xclient.data.l[0] = (long) XA_ACTION;
+    event.xclient.data.l[1] = 0;
+    event.xclient.data.l[2] = 0;
+    old_handler = XSetErrorHandler( printErrorHandler );
+    if ( ! XSendEvent( dpy, window, False, 0, &event ) ) {
+        fprintf( stderr, "enableScreenSaver: XSendEvent to window failed.\n" );
+    }
+    XSync( dpy, False );
+    XSetErrorHandler( old_handler );
+    old_handler = 0;
+    XCloseDisplay( dpy );
+}
+
+void enableScreenSaver( const char *xauth, const char *display, const int state )
+{
+    if ( state != SAVER_ACTIVE && state != SAVER_LOCKED ) {
+        fprintf( stderr, "enableScreenSaver: Invalid state %d requested.\n", state );
+        return;
+    }
+    if ( _testmode ) {
+        printf( "Testmode: Not setting screen saver to %d\n", state );
+        return;
+    }
+    if ( ! doublefork() )
+        return;
+    enableScreenSaverFork( xauth, display, state );
+    exit( 0 );
+}
+
+static int runClient( const char *display, int fd )
+{
+    struct x11state buffer = {0};
+    XScreenSaverInfo *ssi;
+    Display *dpy;
+    int dummy;
+
+    dpy = XOpenDisplay( display );
+    if ( dpy == NULL ) {
+        fprintf( stderr, "Cannot open display\n" );
+        return 1;
+    }
+    if ( !XScreenSaverQueryExtension( dpy, &dummy, &dummy ) ) {
+        fprintf( stderr, "screen saver extension not supported\n" );
+       return 1;
+    }
+    ssi = XScreenSaverAllocInfo();
+    if ( ssi == NULL ) {
+          fprintf( stderr, "Cannot allocate screen saver info\n" );
+        return 1;
+    }
+    if ( ! XScreenSaverQueryInfo(dpy, DefaultRootWindow( dpy ), ssi ) ) {
+        fprintf( stderr, "Cannot query screen saver info\n" );
+        return 1;
+    }
+
+    buffer.idleSeconds = ssi->idle / 1000;
+    XFree( ssi );
+    getLockState( dpy, &buffer );
+    if ( DPMSQueryExtension( dpy, &dummy, &dummy ) && DPMSCapable( dpy ) ) {
+        CARD16 state;
+        BOOL onoff;
+        if ( DPMSInfo( dpy, &state, &onoff ) && onoff ) {
+            if ( state == DPMSModeStandby || state == DPMSModeSuspend || state == DPMSModeOff ) {
+                buffer.screenStandby = SCREEN_OFF;
+            } else if ( state == DPMSModeOn ) {
+                buffer.screenStandby = SCREEN_ON;
+            }
+        }
+    }
+
+    if ( write( fd, &buffer, sizeof(buffer) ) != sizeof(buffer) ) {
+        fprintf( stderr, "Error writing to pipe from child\n" );
+    }
+    return 0;
+}
+
+static Window getScreenSaverWindow( Display *dpy )
+{
+    XWindowAttributes xgwa;
+
+    char *v = NULL;
+    Window window = find_screensaver_window( dpy, &v );
+    if( ! window ) {
+        return 0;
+    }
+    if( ! v || ! *v ) {
+        fprintf( stderr, "version property not set on window 0x%x?\n",
+                 ( unsigned int ) window );
+        return 0;
+    }
+
+    /* Select for property change events, so that we can read the response. */
+    XGetWindowAttributes( dpy, window, &xgwa );
+    XSelectInput( dpy, window, xgwa.your_event_mask | PropertyChangeMask );
+
+    XClassHint hint = {0};
+    XGetClassHint( dpy, window, &hint );
+    if( ! hint.res_class ) {
+        fprintf( stderr, "class hints not set on window 0x%x?\n",
+                 ( unsigned int ) window );
+        return 0;
+    }
+    return window;
+}
+
+static void getLockState( Display *dpy, struct x11state *state )
+{
+    Atom XA_LOCK, XA_BLANK;
+    Atom XA_SCREENSAVER_STATUS;
+    XA_SCREENSAVER_STATUS = XInternAtom( dpy, "_SCREENSAVER_STATUS", False );
+    XA_LOCK = XInternAtom( dpy, "LOCK", False );
+    XA_BLANK = XInternAtom( dpy, "BLANK", False );
+
+    Window window = getScreenSaverWindow( dpy );
+    if ( ! window )
+        return;
+
+    Atom type;
+    int format;
+    unsigned long nitems, bytesafter;
+    unsigned char *dataP = 0;
+
+    if( XGetWindowProperty( dpy,
+                            RootWindow( dpy, 0 ),
+                            XA_SCREENSAVER_STATUS,
+                            0, 999, False, XA_INTEGER,
+                            &type, &format, &nitems, &bytesafter,
+                            &dataP )
+            != Success ) {
+        fprintf( stderr, "Foof foof! No property\n" );
+        return;
+    }
+    if ( ! type || dataP == NULL )
+        return;
+
+    Atom *data = ( Atom * ) dataP;
+    if( type != XA_INTEGER || nitems < 3 ) {
+        if( data ) {
+            free( data );
+        }
+        fprintf( stderr, "bad status format on root window.\n" );
+        return;
+    }
+
+    Atom blanked = ( Atom ) data[0];
+    time_t tt = ( time_t ) data[1];
+
+    if( tt <= ( time_t ) 666000000L ) { /* early 1991 */
+        fprintf( stderr, "Bad lock time reported\n" );
+        return;
+    }
+
+    if( blanked == XA_LOCK ) {
+        // Got valid lock time
+        state->lockTimestamp = tt;
+        state->saverState = SAVER_LOCKED;
+    } else if ( blanked == XA_BLANK ) {
+        state->lockTimestamp = tt;
+        state->saverState = SAVER_ACTIVE;
+    }
+}
+
+static Bool got_badwindow = False;
+static int BadWindow_ehandler( Display *dpy, XErrorEvent *error )
+{
+    if( error->error_code == BadWindow ) {
+        got_badwindow = True;
+        return 0;
+    }
+    if( !old_handler ) {
+        abort();
+    }
+    return ( *old_handler )( dpy, error );
+}
+
+static Window find_screensaver_window( Display *dpy, char **version )
+{
+    Window root = RootWindowOfScreen( DefaultScreenOfDisplay( dpy ) );
+    Window root2, parent, *kids;
+    unsigned int nkids;
+    Atom XA_SCREENSAVER_VERSION;
+    XA_SCREENSAVER_VERSION = XInternAtom( dpy, "_SCREENSAVER_VERSION", False );
+
+    if( version ) {
+        *version = 0;
+    }
+
+    if( ! XQueryTree( dpy, root, &root2, &parent, &kids, &nkids ) ) {
+        fprintf( stderr, "fssw: Cannot query tree\n" );
+        return 0;
+    }
+    if( root != root2 ) {
+        fprintf( stderr, "fssw: root != root2\n" );
+        return 0;
+    }
+    if( parent ) {
+        fprintf( stderr, "fssw: Got parent!\n" );
+        return 0;
+    }
+    if( !( kids && nkids ) ) {
+        return 0;
+    }
+    for( unsigned int i = 0; i < nkids; i++ ) {
+        Atom type;
+        int format;
+        unsigned long nitems, bytesafter;
+        unsigned char *v;
+        int status;
+
+        /* We're walking the list of root-level windows and trying to find
+           the one that has a particular property on it.  We need to trap
+           BadWindows errors while doing this, because it's possible that
+           some random window might get deleted in the meantime.  (That
+           window won't have been the one we're looking for.)
+         */
+        XSync( dpy, False );
+        if( old_handler ) {
+            abort();
+        }
+        got_badwindow = False;
+        old_handler = XSetErrorHandler( BadWindow_ehandler );
+        status = XGetWindowProperty( dpy, kids[i],
+                                     XA_SCREENSAVER_VERSION,
+                                     0, 200, False, XA_STRING,
+                                     &type, &format, &nitems, &bytesafter,
+                                     &v );
+        XSync( dpy, False );
+        XSetErrorHandler( old_handler );
+        old_handler = 0;
+
+        if( got_badwindow ) {
+            status = BadWindow;
+            got_badwindow = False;
+        }
+
+        if( status == Success && type != None ) {
+            Window ret = kids[i];
+            if( version ) {
+                *version = ( char* )v;
+            }
+            XFree( kids );
+            return ret;
+        }
+    }
+
+    if( kids ) {
+        XFree( kids );
+    }
+    return 0;
+}
+
diff --git a/src/x11util.h b/src/x11util.h
new file mode 100644
index 0000000..6389a7c
--- /dev/null
+++ b/src/x11util.h
@@ -0,0 +1,28 @@
+#ifndef _X11_UTIL_H_
+#define _X11_UTIL_H_
+
+#include <stdbool.h>
+#include <time.h>
+
+#define SAVER_OFF (0)
+#define SAVER_ACTIVE (1)
+#define SAVER_LOCKED (2)
+
+#define SCREEN_UNKNOWN (0)
+#define SCREEN_ON (1)
+#define SCREEN_OFF (2)
+
+struct x11state {
+	time_t lockTimestamp;
+	int idleSeconds;
+	int saverState;
+	int screenStandby;
+};
+
+bool getX11IdleTimes( const char *xauth, const char *display, struct x11state *state );
+
+void setScreenDpms( const char *xauth, const char *display, int mode );
+
+void enableScreenSaver( const char *xauth, const char *display, const int state );
+
+#endif