Initial commit

6 files changed, 1060 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..f5bd368
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+rtkit-daemon
+rtkit-test
+*.o
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..85c6ab4
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,13 @@
+CFLAGS=-Wextra -Wall -O0 -g `pkg-config --cflags dbus-1`
+LIBS= `pkg-config --libs dbus-1`
+
+all: rtkit-daemon rtkit-test
+
+rtkit-daemon: rtkit-daemon.o
+	$(CC) $(CFLAGS) $(LIBS) -o rtkit-daemon $^
+
+rtkit-test: rtkit-test.o rtkit.o rtkit.h
+	$(CC) $(CFLAGS) $(LIBS) -o rtkit-test $^
+
+clean:
+	rm -rf rtkit-daemon *.o
diff --git a/rtkit-daemon.c b/rtkit-daemon.c
new file mode 100644
index 0000000..6a9f4ff
--- /dev/null
+++ b/rtkit-daemon.c
@@ -0,0 +1,755 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+#define _GNU_SOURCE
+
+#include <unistd.h>
+#include <stdio.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <string.h>
+#include <sched.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <stdlib.h>
+#include <inttypes.h>
+#include <dbus/dbus.h>
+#include <pwd.h>
+#include <sys/capability.h>
+#include <sys/prctl.h>
+
+#include "rtkit.h"
+
+#ifndef __linux__
+#error "This stuff only works on Linux!"
+#endif
+
+#ifndef SCHED_RESET_ON_FORK
+#warning "Your libc lacks the definition of SCHED_RESET_ON_FORK. We'll now define it ourselves, however make sure your kernel is new enough!"
+#define SCHED_RESET_ON_FORK 0x40000000
+#endif
+
+#ifndef RLIMIT_RTTIME
+#define RLIMIT_RTTIME 15
+#endif
+
+#define OUR_RR_PRIORITY 30
+#define OUR_NICE_LEVEL 1
+
+#define USERNAME "rtkit"
+
+#define RTKIT_RTTIME_MAX_NS 200000000ULL /* 200 ms */
+
+#define INTROSPECT_XML                                                  \
+        DBUS_INTROSPECT_1_0_XML_DOCTYPE_DECL_NODE                       \
+        "<node>"                                                        \
+        " <interface name=\"org.freedesktop.RealtimeKit1\">"            \
+        "  <method name=\"MakeThreadRealtime\">"                        \
+        "   <arg name=\"thread\" type=\"t\" direction=\"in\"/>"         \
+        "   <arg name=\"priority\" type=\"u\" direction=\"in\"/>"       \
+        "  </method>"                                                   \
+        "  <method name=\"MakeHighPriority\">"                          \
+        "   <arg name=\"thread\" type=\"t\" direction=\"in\"/>"         \
+        "   <arg name=\"priority\" type=\"i\" direction=\"in\"/>"       \
+        "  </method>"                                                   \
+        " </interface>"                                                 \
+        " <interface name=\"org.freedesktop.DBus.Introspectable\">"     \
+        "  <method name=\"Introspect\">"                                \
+        "   <arg name=\"data\" type=\"s\" direction=\"out\"/>"          \
+        "  </method>"                                                   \
+        " </interface>"                                                 \
+        "</node>"
+
+/* Similar to assert(), but has side effects, and hence shall never be optimized away, regardless of NDEBUG */
+#define assert_se(expr)                                                 \
+        do {                                                            \
+                if (__builtin_expect(!(expr), 0)) {                     \
+                        fprintf(stderr, "Asssertion %s failed at %s:%u, function %s(). Aborting.\n", #expr, __FILE__, __LINE__, __PRETTY_FUNCTION__); \
+                        abort();                                        \
+                }                                                       \
+        } while(0)
+
+#define ELEMENTSOF(x) (sizeof(x)/sizeof(x[0]))
+
+struct process {
+        pid_t pid;
+        uid_t uid;
+        unsigned long long starttime;
+};
+
+static int startswith(const char *s, const char *prefix) {
+        return strncmp(s, prefix, strlen(prefix)) == 0;
+}
+
+static int self_set_realtime(void) {
+        struct sched_param param;
+        int r;
+
+        memset(&param, 0, sizeof(param));
+        param.sched_priority = OUR_RR_PRIORITY;
+
+        if (sched_setscheduler(0, SCHED_RR|SCHED_RESET_ON_FORK, &param) < 0) {
+                r = -errno;
+                fprintf(stderr, "Failed to make ourselves SCHED_RR: %s\n", strerror(errno));
+                goto finish;
+        }
+
+        r = 0;
+
+finish:
+        return r;
+}
+
+static void self_drop_realtime(void) {
+        struct sched_param param;
+
+        memset(&param, 0, sizeof(param));
+
+        if (sched_setscheduler(0, SCHED_OTHER, &param) < 0)
+                fprintf(stderr, "Warning: Failed to reset scheduling to SCHED_OTHER: %s\n", strerror(errno));
+
+        if (setpriority(PRIO_PROCESS, 0, OUR_NICE_LEVEL) < 0)
+                fprintf(stderr, "Warning: Failed to reset nice level to %u: %s\n", OUR_NICE_LEVEL, strerror(errno));
+}
+
+static int verify_rttime(struct process *p) {
+        char fn[128];
+        FILE *f;
+        int r, good = 0;
+
+        /* Verifies that RLIMIT_RTTIME is set for the specified process */
+
+        assert_se(snprintf(fn, sizeof(fn)-1, "/proc/%llu/limits", (unsigned long long) p->pid) < (int) (sizeof(fn)-1));
+        fn[sizeof(fn)-1] = 0;
+
+        if (!(f = fopen(fn, "r"))) {
+                r = -errno;
+                fprintf(stderr, "Failed to open '%s': %s\n", fn, strerror(errno));
+                return r;
+        }
+
+        for (;;) {
+                char line[128];
+                char soft[32], hard[32];
+                unsigned long long rttime;
+                char *e = NULL;
+
+                if (!fgets(line, sizeof(line), f))
+                        break;
+
+                if (!startswith(line, "Max realtime timeout"))
+                        continue;
+
+                if (sscanf(line + 20, "%s %s", soft, hard) != 2)
+                        break;
+
+                errno = 0;
+                rttime = strtoll(hard, &e, 10);
+
+                if (errno != 0 || !e || *e != 0)
+                        break;
+
+                if (rttime <= RTKIT_RTTIME_MAX_NS)
+                        good = 1;
+
+                break;
+        }
+
+        fclose(f);
+
+        return good ? 0 : -EPERM;
+}
+
+static int verify_user(struct process *p) {
+        char fn[128];
+        int r;
+        struct stat st;
+
+        assert_se(snprintf(fn, sizeof(fn)-1, "/proc/%llu", (unsigned long long) p->pid) < (int) (sizeof(fn)-1));
+        fn[sizeof(fn)-1] = 0;
+
+        memset(&st, 0, sizeof(st));
+        if (stat(fn, &st) < 0) {
+                r = -errno;
+                fprintf(stderr, "Failed to stat() file '%s': %s\n", fn, strerror(errno));
+                return r;
+        }
+
+        return st.st_uid == p->uid ? 0 : -EPERM;
+}
+
+static int read_starttime(pid_t pid, unsigned long long *st) {
+        char fn[128];
+        int r;
+        FILE *f;
+
+        assert_se(snprintf(fn, sizeof(fn)-1, "/proc/%llu/stat", (unsigned long long) pid) < (int) (sizeof(fn)-1));
+        fn[sizeof(fn)-1] = 0;
+
+        if (!(f = fopen(fn, "r"))) {
+                r = -errno;
+                fprintf(stderr, "Failed to open '%s': %s\n", fn, strerror(errno));
+                return r;
+        }
+
+        if (fscanf(f,
+                   "%*d "  /* pid */
+                   "%*s "  /* comm */
+                   "%*c "  /* state */
+                   "%*d "  /* ppid */
+                   "%*d "  /* pgrp */
+                   "%*d "  /* session */
+                   "%*d "  /* tty_nr */
+                   "%*d "  /* tpgid */
+                   "%*u "  /* flags */
+                   "%*u "  /* minflt */
+                   "%*u "  /* cminflt */
+                   "%*u "  /* majflt */
+                   "%*u "  /* cmajflt */
+                   "%*u "  /* utime */
+                   "%*u "  /* stime */
+                   "%*d "  /* cutime */
+                   "%*d "  /* cstime */
+                   "%*d "  /* priority */
+                   "%*d "  /* nice */
+                   "%*d "  /* num_threads */
+                   "%*d "  /* itrealvalue */
+                   "%llu "  /* starttime */,
+                   st) != 1) {
+                fclose(f);
+                return -EIO;
+        }
+
+        fclose(f);
+        return 0;
+}
+
+static int verify_starttime(struct process *p) {
+        unsigned long long st;
+        int r;
+
+        if ((r = read_starttime(p->pid, &st)) < 0)
+                return r;
+
+        return st == p->starttime ? 0 : -EPERM;
+}
+
+static int verify_thread(struct process *p, pid_t thread) {
+        char fn[128];
+
+        /* Verifies that the specified thread exists in the specified
+         * process */
+
+        assert_se(snprintf(fn, sizeof(fn)-1, "/proc/%llu/task/%llu", (unsigned long long) p->pid, (unsigned long long) thread) < (int) (sizeof(fn)-1));
+        fn[sizeof(fn)-1] = 0;
+
+        return access(fn, F_OK) == 0 ? 0 : -errno;
+}
+
+static void thread_reset(pid_t thread) {
+        struct sched_param param;
+
+        memset(&param, 0, sizeof(param));
+        param.sched_priority = 0;
+
+        if (sched_setscheduler(thread, SCHED_OTHER, &param) < 0)
+                fprintf(stderr, "Warning: Failed to reset scheduling to SCHED_OTHER for thread %llu: %s\n", (unsigned long long) thread, strerror(errno));
+
+        if (setpriority(PRIO_PROCESS, thread, 0) < 0)
+                fprintf(stderr, "Warning: Failed to reset nice level to 0 for thread %llu: %s\n", (unsigned long long) thread, strerror(errno));
+}
+
+static char* get_exe_name(pid_t pid, char *exe, size_t len) {
+        char fn[128];
+        ssize_t n;
+
+        assert_se(snprintf(fn, sizeof(fn)-1, "/proc/%llu/exe", (unsigned long long) pid) < (int) (sizeof(fn)-1));
+        fn[sizeof(fn)-1] = 0;
+
+        if ((n = readlink(fn, exe, len-1)) < 0) {
+                snprintf(exe, len-1, "n/a");
+                exe[len-1] = 0;
+        } else
+                exe[n] = 0;
+
+        return exe;
+}
+
+static char* get_user_name(uid_t uid, char *user, size_t len) {
+        struct passwd *pw;
+
+        if ((pw = getpwuid(uid))) {
+                strncpy(user, pw->pw_name, len-1);
+                user[len-1] = 0;
+                return user;
+        }
+
+        snprintf(user, len-1, "%llu", (unsigned long long) uid);
+        user[len-1] = 0;
+        return user;
+}
+
+static int process_set_realtime(struct process *p, pid_t thread, unsigned priority) {
+        int r;
+        struct sched_param param;
+        char user[64], exe[128];
+
+        if (thread < 0)
+                return -EINVAL;
+
+        if ((int) priority < sched_get_priority_min(SCHED_RR) ||
+            (int) priority > sched_get_priority_max(SCHED_RR))
+                return -EINVAL;
+
+        if (priority >= OUR_RR_PRIORITY)
+                return -EPERM;
+
+        if (thread == 0)
+                thread = p->pid;
+
+        /* Temporarily become a realtime process. We do this to make
+         * sure that our verification code is not preempted by an evil
+         * client's code which might have gotten SCHED_RR through
+         * us. */
+        if ((r = self_set_realtime()) < 0)
+                return r;
+
+        /* Let's make sure that everything is alright before we make
+         * the process realtime */
+        if ((r = verify_user(p)) < 0 ||
+            (r = verify_starttime(p)) < 0 ||
+            (r = verify_rttime(p)) < 0 ||
+            (r = verify_thread(p, thread)) < 0)
+                goto finish;
+
+        /* Ok, everything seems to be in order, now, let's do it */
+        memset(&param, 0, sizeof(param));
+        param.sched_priority = (int) priority;
+        if (sched_setscheduler(thread, SCHED_RR|SCHED_RESET_ON_FORK, &param) < 0) {
+                r = -errno;
+                fprintf(stderr, "Failed to make thread %llu SCHED_RR: %s\n", (unsigned long long) thread, strerror(errno));
+                goto finish;
+        }
+
+        /* We do some sanity checks afterwards, to verify that the
+         * caller didn't play games with us and replaced the process
+         * behind the PID */
+        if ((r = verify_thread(p, thread)) < 0 ||
+            (r = verify_rttime(p)) < 0 ||
+            (r = verify_starttime(p)) < 0 ||
+            (r = verify_user(p)) < 0) {
+
+                thread_reset(thread);
+                goto finish;
+        }
+
+        fprintf(stderr, "Sucessfully made thread %llu of process %llu (%s) owned by '%s' SCHED_RR at priority %u.\n",
+                (unsigned long long) thread,
+                (unsigned long long) p->pid,
+                get_exe_name(p->pid, exe, sizeof(exe)),
+                get_user_name(p->uid, user, sizeof(user)),
+                priority);
+
+        r = 0;
+
+finish:
+        self_drop_realtime();
+
+        return r;
+}
+
+static int process_set_high_priority(struct process *p, pid_t thread, int priority) {
+        int r;
+        struct sched_param param;
+        char user[64], exe[128];
+
+        if (thread < 0)
+                return -EINVAL;
+
+        if (priority < -20 || priority > 19)
+                return -EINVAL;
+
+        if (thread == 0)
+                thread = p->pid;
+
+        /* Temporarily become a realtime process */
+        if ((r = self_set_realtime()) < 0)
+                return r;
+
+        /* Let's make sure that everything is alright before we make
+         * the process high priority */
+        if ((r = verify_user(p)) < 0 ||
+            (r = verify_starttime(p)) < 0 ||
+            (r = verify_thread(p, thread)) < 0)
+                goto finish;
+
+        /* Ok, everything seems to be in order, now, let's do it */
+        memset(&param, 0, sizeof(param));
+        param.sched_priority = 0;
+        if (sched_setscheduler(thread, SCHED_OTHER|SCHED_RESET_ON_FORK, &param) < 0) {
+                r = -errno;
+                fprintf(stderr, "Failed to make process %llu SCHED_NORMAL: %s\n", (unsigned long long) thread, strerror(errno));
+                goto finish;
+        }
+
+        if (setpriority(PRIO_PROCESS, thread, priority) < 0) {
+                r = -errno;
+                fprintf(stderr, "Failed to set nice level of process %llu to %i: %s\n", (unsigned long long) thread, priority, strerror(errno));
+                goto finish;
+        }
+
+        if ((r = verify_thread(p, thread)) < 0 ||
+            (r = verify_starttime(p)) < 0 ||
+            (r = verify_user(p)) < 0) {
+
+                thread_reset(thread);
+                goto finish;
+        }
+
+        fprintf(stderr, "Sucessfully made thread %llu of process %llu (%s) owned by '%s' high priority at nice level %i.\n",
+                (unsigned long long) thread,
+                (unsigned long long) p->pid,
+                get_exe_name(p->pid, exe, sizeof(exe)),
+                get_user_name(p->uid, user, sizeof(user)),
+                priority);
+
+        r = 0;
+
+finish:
+        self_drop_realtime();
+
+        return r;
+}
+
+/* This mimics dbus_bus_get_unix_user() */
+static unsigned long get_unix_process_id(
+                DBusConnection *connection,
+                const char *name,
+                DBusError *error) {
+
+        DBusMessage *m, *r;
+        uint32_t pid = (uint32_t) -1;
+
+        assert_se(m = dbus_message_new_method_call(
+                                  DBUS_SERVICE_DBUS,
+                                  DBUS_PATH_DBUS,
+                                  DBUS_INTERFACE_DBUS,
+                                  "GetConnectionUnixProcessID"));
+
+        assert_se(dbus_message_append_args(
+                                  m,
+                                  DBUS_TYPE_STRING, &name,
+                                  DBUS_TYPE_INVALID));
+
+        r = dbus_connection_send_with_reply_and_block(connection, m, -1, error);
+        dbus_message_unref (m);
+
+        if (!r)
+                goto finish;
+
+        if (dbus_set_error_from_message(error, r))
+                goto finish;
+
+        if (!dbus_message_get_args(
+                            r, error,
+                            DBUS_TYPE_UINT32, &pid,
+                            DBUS_TYPE_INVALID)) {
+                pid = (uint32_t) -1;
+                goto finish;
+        }
+
+finish:
+
+        if (r)
+                dbus_message_unref(r);
+
+        return (unsigned long) pid;
+}
+
+static int process_fill(struct process *p, DBusConnection *c, DBusMessage *m) {
+        DBusError error;
+        int r;
+        unsigned long pid, uid;
+
+        dbus_error_init(&error);
+
+        if ((uid = dbus_bus_get_unix_user(c, dbus_message_get_sender(m), &error)) == (unsigned long) -1) {
+                fprintf(stderr, "dbus_message_get_unix_user() failed: %s\n", error.message);
+                r = -EIO;
+                goto fail;
+        }
+
+        p->uid = (uid_t) uid;
+
+        if ((pid = get_unix_process_id(c, dbus_message_get_sender(m), &error)) == (unsigned long) -1) {
+                fprintf(stderr, "get_unix_process_id() failed: %s\n", error.message);
+                r = -EIO;
+                goto fail;
+        }
+
+        p->pid = (uid_t) pid;
+
+        if ((r = read_starttime(p->pid, &p->starttime)) < 0)
+                goto fail;
+
+        return 0;
+
+fail:
+        dbus_error_free(&error);
+
+        return r;
+}
+
+static DBusHandlerResult dbus_handler(DBusConnection *c, DBusMessage *m, void *userdata) {
+        DBusError error;
+        DBusMessage *r = NULL;
+
+        dbus_error_init(&error);
+
+        if (dbus_message_is_method_call(m, "org.freedesktop.RealtimeKit1", "MakeThreadRealtime")) {
+
+                uint64_t thread;
+                uint32_t priority;
+                struct process p;
+                int ret;
+
+                if (!dbus_message_get_args(m, &error,
+                                           DBUS_TYPE_UINT64, &thread,
+                                           DBUS_TYPE_UINT32, &priority,
+                                           DBUS_TYPE_INVALID)) {
+
+                        fprintf(stderr, "Failed to parse MakeThreadRealtime() method call: %s\n", error.message);
+                        assert_se(r = dbus_message_new_error(m, error.name, error.message));
+
+                        goto finish;
+                }
+
+                if ((ret = process_fill(&p, c, m)) < 0) {
+                        assert_se(r = dbus_message_new_error_printf(m, DBUS_ERROR_FAILED, strerror(-ret)));
+                        goto finish;
+                }
+
+                if ((ret = process_set_realtime(&p, (pid_t) thread, priority))) {
+                        assert_se(r = dbus_message_new_error_printf(m, DBUS_ERROR_FAILED, strerror(-ret)));
+                        goto finish;
+                }
+
+                assert_se(r = dbus_message_new_method_return(m));
+
+        } else if (dbus_message_is_method_call(m, "org.freedesktop.RealtimeKit1", "MakeThreadHighPriority")) {
+
+                uint64_t thread;
+                int32_t priority;
+                struct process p;
+                int ret;
+
+                if (!dbus_message_get_args(m, &error,
+                                           DBUS_TYPE_UINT64, &thread,
+                                           DBUS_TYPE_INT32, &priority,
+                                           DBUS_TYPE_INVALID)) {
+
+                        fprintf(stderr, "Failed to parse MakeThreadHighPriority() method call: %s\n", error.message);
+                        assert_se(r = dbus_message_new_error(m, error.name, error.message));
+
+                        goto finish;
+                }
+
+                if ((ret = process_fill(&p, c, m)) < 0) {
+                        assert_se(r = dbus_message_new_error_printf(m, DBUS_ERROR_FAILED, strerror(-ret)));
+                        goto finish;
+                }
+
+                if ((ret = process_set_high_priority(&p, (pid_t) thread, priority))) {
+                        assert_se(r = dbus_message_new_error_printf(m, DBUS_ERROR_FAILED, strerror(-ret)));
+                        goto finish;
+                }
+
+                assert_se(r = dbus_message_new_method_return(m));
+
+        } else if (dbus_message_is_method_call(m, "org.freedesktop.DBus.Introspectable", "Introspect")) {
+                const char *xml = INTROSPECT_XML;
+
+                assert_se(r = dbus_message_new_method_return(m));
+                assert_se(dbus_message_append_args(
+                                          r,
+                                          DBUS_TYPE_STRING, &xml,
+                                          DBUS_TYPE_INVALID));
+        } else
+                return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
+
+finish:
+
+        if (r) {
+                assert_se(dbus_connection_send(c, r, NULL));
+                dbus_message_unref(r);
+        }
+
+        dbus_error_free(&error);
+
+        return DBUS_HANDLER_RESULT_HANDLED;
+}
+
+static int setup_dbus(DBusConnection **c) {
+        static const DBusObjectPathVTable vtable = {
+                .message_function = dbus_handler,
+        };
+
+        DBusError error;
+
+        dbus_error_init(&error);
+
+        if (!(*c = dbus_bus_get(DBUS_BUS_SYSTEM, &error))) {
+                fprintf(stderr, "Failed to connect to system bus: %s\n", error.message);
+                goto fail;
+        }
+
+        if (dbus_bus_request_name(*c, RTKIT_SERVICE_NAME, DBUS_NAME_FLAG_DO_NOT_QUEUE, &error) < 0) {
+                fprintf(stderr, "Failed to register name on bus: %s\n", error.message);
+                goto fail;
+        }
+
+        assert_se(dbus_connection_register_object_path(*c, RTKIT_OBJECT_PATH, &vtable, NULL));
+
+        return 0;
+
+fail:
+        dbus_error_free(&error);
+        return -EIO;
+}
+
+static int drop_priviliges(void) {
+        struct passwd *pw;
+        int r;
+        cap_t caps;
+        const cap_value_t cap_values[] = {
+                CAP_SYS_NICE,             /* Needed for obvious reasons */
+                CAP_DAC_READ_SEARCH,      /* Needed so that we can verify resource limits */
+                CAP_SYS_PTRACE            /* Needed so that we can read /proc/$$/exe. Linux is weird. */
+        };
+
+        if (!(pw = getpwnam(USERNAME))) {
+                fprintf(stderr, "Failed to find user '%s'.\n", USERNAME);
+                return -ENOENT;
+        }
+
+        /* First, say that we want to keep caps */
+        if (prctl(PR_SET_KEEPCAPS, 1) < 0) {
+                r = -errno;
+                fprintf(stderr, "PR_SET_KEEPCAPS failed: %s\n", strerror(errno));
+                return r;
+        }
+
+        /* Second, drop privs */
+        if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0 ||
+            setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0) {
+                r = -errno;
+                fprintf(stderr, "Failed to become %s: %s\n", USERNAME, strerror(errno));
+                return r;
+        }
+
+        /* Third, reset caps flag */
+        if (prctl(PR_SET_KEEPCAPS, 0) < 0) {
+                r = -errno;
+                fprintf(stderr, "PR_SET_KEEPCAPS failed: %s\n", strerror(errno));
+                return r;
+        }
+
+        /* Fourth, reduce caps */
+        assert_se(caps = cap_init());
+        assert_se(cap_clear(caps) == 0);
+        assert_se(cap_set_flag(caps, CAP_EFFECTIVE, ELEMENTSOF(cap_values), cap_values, CAP_SET) == 0);
+        assert_se(cap_set_flag(caps, CAP_PERMITTED, ELEMENTSOF(cap_values), cap_values, CAP_SET) == 0);
+
+        if (cap_set_proc(caps) < 0) {
+                r = -errno;
+                fprintf(stderr, "cap_set_proc() failed: %s\n", strerror(errno));
+                return r;
+        }
+
+        /* Fifth, update environment */
+        setenv("USER", USERNAME, 1);
+        setenv("USERNAME", USERNAME, 1);
+        setenv("LOGNAME", USERNAME, 1);
+        setenv("HOME", pw->pw_dir, 1);
+
+        fprintf(stderr, "Sucessfully dropped priviliges.\n");
+
+        return 0;
+}
+
+static int set_resource_limits(void) {
+
+        static const struct {
+                int id;
+                const char *name;
+                rlim_t value;
+        } table[] = {
+                { .id = RLIMIT_FSIZE,    .name = "RLIMIT_FSIZE",    .value =  0 },
+                { .id = RLIMIT_MEMLOCK,  .name = "RLIMIT_MEMLOCK",  .value =  0 },
+                { .id = RLIMIT_MSGQUEUE, .name = "RLIMIT_MSGQUEUE", .value =  0 },
+                { .id = RLIMIT_NICE,     .name = "RLIMIT_NICE",     .value = 20 },
+                { .id = RLIMIT_NOFILE,   .name = "RLIMIT_NOFILE",   .value = 50 },
+                { .id = RLIMIT_NPROC,    .name = "RLIMIT_NPROC",    .value =  1 },
+                { .id = RLIMIT_RTPRIO,   .name = "RLIMIT_RTPRIO",   .value =  0 }, /* Since we have CAP_SYS_NICE we don't need this */
+                { .id = RLIMIT_RTTIME,   .name = "RLIMIT_RTTIME",   .value = RTKIT_RTTIME_MAX_NS } /* Do as I say AND do as I do */
+        };
+
+        unsigned u;
+        int r;
+
+        for (u = 0; u < ELEMENTSOF(table); u++) {
+                struct rlimit rlim;
+
+                if (getrlimit(table[u].id, &rlim) < 0) {
+                        r = -errno;
+                        fprintf(stderr, "Failed to get %s: %s\n", table[u].name, strerror(errno));
+                        return r;
+                }
+
+                if (rlim.rlim_max < table[u].value)
+                        continue;
+
+                rlim.rlim_cur = rlim.rlim_max = table[u].value;
+
+                if (setrlimit(table[u].id, &rlim) < 0) {
+                        r = -errno;
+                        fprintf(stderr, "Failed to set %s: %s\n", table[u].name, strerror(errno));
+                        return r;
+                }
+        }
+
+        return 0;
+}
+
+int main(int argc, char *argv[]) {
+        DBusConnection *bus = NULL;
+        int ret = 1;
+
+        self_drop_realtime();
+
+        if (drop_priviliges() < 0)
+                goto finish;
+
+        if (set_resource_limits() < 0)
+                goto finish;
+
+        assert_se(chdir("/") == 0);
+        umask(0777);
+
+        if (setup_dbus(&bus) < 0)
+                goto finish;
+
+        fprintf(stderr, "Running.\n");
+
+        while (dbus_connection_read_write_dispatch(bus, -1))
+                ;
+
+        ret = 0;
+
+finish:
+
+        if (bus)
+                dbus_connection_unref(bus);
+
+        return ret;
+}
diff --git a/rtkit-test.c b/rtkit-test.c
new file mode 100644
index 0000000..59244f8
--- /dev/null
+++ b/rtkit-test.c
@@ -0,0 +1,84 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+#include <errno.h>
+#include <string.h>
+#include <sched.h>
+#include <stdio.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+
+#include "rtkit.h"
+
+#ifndef SCHED_RESET_ON_FORK
+#define SCHED_RESET_ON_FORK 0x40000000
+#endif
+
+static void print_status(const char *t) {
+    int ret;
+
+    if ((ret = sched_getscheduler(0)) < 0) {
+        fprintf(stderr, "sched_getscheduler() failed: %s\n", strerror(errno));
+        return;
+    }
+
+    printf("%s:\n"
+           "\tSCHED_RESET_ON_FORK: %s\n",
+           t,
+           (ret & SCHED_RESET_ON_FORK) ? "yes" : "no");
+
+    if ((ret & ~SCHED_RESET_ON_FORK) == SCHED_RR) {
+        struct sched_param param;
+
+        if (sched_getparam(0, &param) < 0) {
+            fprintf(stderr, "sched_getschedparam() failed: %s\n", strerror(errno));
+            return;
+        }
+
+        printf("\tSCHED_RR with priority %i\n", param.sched_priority);
+
+    } else if ((ret & ~SCHED_RESET_ON_FORK) == SCHED_OTHER) {
+        errno = 0;
+        ret = getpriority(PRIO_PROCESS, 0);
+        if (errno != 0) {
+            fprintf(stderr, "getpriority() failed: %s\n", strerror(errno));
+            return;
+        }
+
+        printf("\tSCHED_OTHER with nice level: %i\n", ret);
+
+    } else
+        fprintf(stderr, "Neither SCHED_RR nor SCHED_OTHER.\n");
+}
+
+int main(int argc, char *argv[]) {
+    DBusError error;
+    DBusConnection *bus;
+    int r;
+
+    dbus_error_init(&error);
+
+    if (!(bus = dbus_bus_get(DBUS_BUS_SYSTEM, &error))) {
+        fprintf(stderr, "Failed to connect to system bus: %s\n", error.message);
+        return 1;
+    }
+
+    print_status("before");
+
+    if ((r = rtkit_make_high_priority(bus, 0, -10)) < 0)
+        fprintf(stderr, "Failed to become high priority: %s\n", strerror(-r));
+    else
+        printf("Sucessfully became high priority.\n");
+
+    print_status("after high priority");
+
+    if ((r = rtkit_make_realtime(bus, 0, 10)) < 0)
+        fprintf(stderr, "Failed to become realtime: %s\n", strerror(-r));
+    else
+        printf("Sucessfully became realtime.\n");
+
+    print_status("after realtime");
+
+    dbus_connection_unref(bus);
+
+    return 0;
+}
diff --git a/rtkit.c b/rtkit.c
new file mode 100644
index 0000000..67a44f7
--- /dev/null
+++ b/rtkit.c
@@ -0,0 +1,153 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+/***
+  Copyright 2009 Lennart Poettering
+
+  Permission is hereby granted, free of charge, to any person
+  obtaining a copy of this software and associated documentation files
+  (the "Software"), to deal in the Software without restriction,
+  including without limitation the rights to use, copy, modify, merge,
+  publish, distribute, sublicense, and/or sell copies of the Software,
+  and to permit persons to whom the Software is furnished to do so,
+  subject to the following conditions:
+
+  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 AUTHORS OR COPYRIGHT HOLDERS
+  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.
+***/
+
+#include <string.h>
+#include <errno.h>
+
+#include "rtkit.h"
+
+static int translate_error(const char *name) {
+        if (strcmp(name, DBUS_ERROR_NO_MEMORY) == 0)
+                return -ENOMEM;
+        if (strcmp(name, DBUS_ERROR_SERVICE_UNKNOWN) == 0 ||
+            strcmp(name, DBUS_ERROR_NAME_HAS_NO_OWNER) == 0)
+                return -ENOENT;
+        if (strcmp(name, DBUS_ERROR_ACCESS_DENIED) == 0 ||
+            strcmp(name, DBUS_ERROR_AUTH_FAILED) == 0)
+                return -EACCES;
+
+        return -EIO;
+}
+
+int rtkit_make_realtime(DBusConnection *connection, pid_t thread, int priority) {
+        DBusMessage *m = NULL, *r = NULL;
+        dbus_uint64_t u64;
+        dbus_uint32_t u32;
+        DBusError error;
+        int ret;
+
+        dbus_error_init(&error);
+
+        if (!(m = dbus_message_new_method_call(
+                              RTKIT_SERVICE_NAME,
+                              RTKIT_OBJECT_PATH,
+                              "org.freedesktop.RealtimeKit1",
+                              "MakeThreadRealtime"))) {
+                ret = -ENOMEM;
+                goto finish;
+        }
+
+        u64 = (dbus_uint64_t) thread;
+        u32 = (dbus_uint32_t) priority;
+
+        if (!dbus_message_append_args(
+                            m,
+                            DBUS_TYPE_UINT64, &u64,
+                            DBUS_TYPE_UINT32, &u32,
+                            DBUS_TYPE_INVALID)) {
+                ret = -ENOMEM;
+                goto finish;
+        }
+
+        if (!(r = dbus_connection_send_with_reply_and_block(connection, m, -1, &error))) {
+                ret = translate_error(error.name);
+                goto finish;
+        }
+
+
+        if (dbus_set_error_from_message(&error, r)) {
+                ret = translate_error(error.name);
+                goto finish;
+        }
+
+        ret = 0;
+
+finish:
+
+        if (m)
+                dbus_message_unref(m);
+
+        if (r)
+                dbus_message_unref(r);
+
+        return ret;
+}
+
+int rtkit_make_high_priority(DBusConnection *connection, pid_t thread, int nice_level) {
+        DBusMessage *m = NULL, *r = NULL;
+        dbus_uint64_t u64;
+        dbus_int32_t s32;
+        DBusError error;
+        int ret;
+
+        dbus_error_init(&error);
+
+        if (!(m = dbus_message_new_method_call(
+                              RTKIT_SERVICE_NAME,
+                              RTKIT_OBJECT_PATH,
+                              "org.freedesktop.RealtimeKit1",
+                              "MakeThreadHighPriority"))) {
+                ret = -ENOMEM;
+                goto finish;
+        }
+
+        u64 = (dbus_uint64_t) thread;
+        s32 = (dbus_int32_t) nice_level;
+
+        if (!dbus_message_append_args(
+                            m,
+                            DBUS_TYPE_UINT64, &u64,
+                            DBUS_TYPE_INT32, &s32,
+                            DBUS_TYPE_INVALID)) {
+                ret = -ENOMEM;
+                goto finish;
+        }
+
+
+
+        if (!(r = dbus_connection_send_with_reply_and_block(connection, m, -1, &error))) {
+                ret = translate_error(error.name);
+                goto finish;
+        }
+
+
+        if (dbus_set_error_from_message(&error, r)) {
+                ret = translate_error(error.name);
+                goto finish;
+        }
+
+        ret = 0;
+
+finish:
+
+        if (m)
+                dbus_message_unref(m);
+
+        if (r)
+                dbus_message_unref(r);
+
+        return ret;
+}
diff --git a/rtkit.h b/rtkit.h
new file mode 100644
index 0000000..5796ad8
--- /dev/null
+++ b/rtkit.h
@@ -0,0 +1,52 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+#ifndef foortkithfoo
+#define foortkithfoo
+
+/***
+  Copyright 2009 Lennart Poettering
+
+  Permission is hereby granted, free of charge, to any person
+  obtaining a copy of this software and associated documentation files
+  (the "Software"), to deal in the Software without restriction,
+  including without limitation the rights to use, copy, modify, merge,
+  publish, distribute, sublicense, and/or sell copies of the Software,
+  and to permit persons to whom the Software is furnished to do so,
+  subject to the following conditions:
+
+  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 AUTHORS OR COPYRIGHT HOLDERS
+  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.
+***/
+
+#include <sys/types.h>
+#include <dbus/dbus.h>
+
+/* This is the reference implementation for a client for
+ * RealtimeKit. You don't have to use this, but if do, just copy these
+ * sources into your repository */
+
+#define RTKIT_SERVICE_NAME "org.freedesktop.RealtimeKit1"
+#define RTKIT_OBJECT_PATH "/org/freedesktop/RealtimeKit1"
+
+/* This is mostly equivalent to sched_setparam(thread, SCHED_RR, {
+ * .sched_priority = priority }). If thread is 0 the calling
+ * processe's main thread is used. The returned value is a negative
+ * errno error code, or 0 on success. */
+int rtkit_make_realtime(DBusConnection *connection, pid_t thread, int priority);
+
+/* This is mostly equivalent to setpriority(PRIO_PROCESS, thread,
+ * nice_level). If thread is 0 the calling processe's main thread is
+ * used. The returned value is a negative errno error code, or 0 on
+ * success.*/
+int rtkit_make_high_priority(DBusConnection *connection, pid_t thread, int nice_level);
+
+#endif