Patchwork [v7,3/4] guest agent: qemu-ga daemon

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Submitter Michael Roth
Date July 14, 2011, 8 p.m.
Message ID <1310673634-17631-4-git-send-email-mdroth@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/104724/
State New
Headers show

Comments

Michael Roth - July 14, 2011, 8 p.m.
This is the actual guest daemon, it listens for requests over a
virtio-serial/isa-serial/unix socket channel and routes them through
to dispatch routines, and writes the results back to the channel in
a manner similar to QMP.

A shorthand invocation:

  qemu-ga -d

Is equivalent to:

  qemu-ga -m virtio-serial -p /dev/virtio-ports/org.qemu.guest_agent.0 \
          -f /var/run/qemu-guest-agent.pid -d

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 Makefile               |   10 +-
 qemu-ga.c              |  667 ++++++++++++++++++++++++++++++++++++++++++++++++
 qga/guest-agent-core.h |    4 +
 3 files changed, 677 insertions(+), 4 deletions(-)
 create mode 100644 qemu-ga.c

Patch

diff --git a/Makefile b/Makefile
index 6c3ba71..b2e8593 100644
--- a/Makefile
+++ b/Makefile
@@ -140,7 +140,7 @@  endif
 ######################################################################
 
 qemu-img.o: qemu-img-cmds.h
-qemu-img.o qemu-tool.o qemu-nbd.o qemu-io.o cmd.o: $(GENERATED_HEADERS)
+qemu-img.o qemu-tool.o qemu-nbd.o qemu-io.o cmd.o qemu-ga.o: $(GENERATED_HEADERS)
 
 qemu-img$(EXESUF): qemu-img.o qemu-tool.o qemu-error.o $(oslib-obj-y) $(trace-obj-y) $(block-obj-y) $(qobject-obj-y) $(version-obj-y) qemu-timer-common.o
 
@@ -163,7 +163,7 @@  check-qfloat: check-qfloat.o qfloat.o $(CHECK_PROG_DEPS)
 check-qjson: check-qjson.o qfloat.o qint.o qdict.o qstring.o qlist.o qbool.o qjson.o json-streamer.o json-lexer.o json-parser.o error.o qerror.o qemu-error.o $(CHECK_PROG_DEPS)
 
 qapi-dir := qapi-generated
-$(qapi-obj-y) test-visitor.o test-qmp-commands.o: QEMU_CFLAGS += -I $(qapi-dir)
+$(qapi-obj-y) test-visitor.o test-qmp-commands.o qemu-ga$(EXESUF): QEMU_CFLAGS += -I $(qapi-dir)
 
 $(qapi-dir)/test-qapi-types.c: $(qapi-dir)/test-qapi-types.h
 $(qapi-dir)/test-qapi-types.h: $(SRC_PATH)/qapi-schema-test.json $(SRC_PATH)/scripts/qapi-types.py
@@ -183,13 +183,15 @@  test-qmp-commands: test-qmp-commands.o qfloat.o qint.o qdict.o qstring.o qlist.o
 
 QGALIB=qga/guest-agent-command-state.o
 
+qemu-ga$(EXESUF): qemu-ga.o $(QGALIB) qemu-tool.o qemu-error.o error.o $(oslib-obj-y) $(trace-obj-y) $(block-obj-y) $(qobject-obj-y) $(version-obj-y) $(qapi-obj-y) qemu-timer-common.o qemu-sockets.o module.o qapi/qmp-dispatch.o qapi/qmp-registry.o
+
 QEMULIBS=libhw32 libhw64 libuser libdis libdis-user
 
 clean:
 # avoid old build problems by removing potentially incorrect old files
 	rm -f config.mak op-i386.h opc-i386.h gen-op-i386.h op-arm.h opc-arm.h gen-op-arm.h
 	rm -f qemu-options.def
-	rm -f *.o *.d *.a *.lo $(TOOLS) TAGS cscope.* *.pod *~ */*~
+	rm -f *.o *.d *.a *.lo $(TOOLS) qemu-ga TAGS cscope.* *.pod *~ */*~
 	rm -Rf .libs
 	rm -f slirp/*.o slirp/*.d audio/*.o audio/*.d block/*.o block/*.d net/*.o net/*.d fsdev/*.o fsdev/*.d ui/*.o ui/*.d qapi/*.o qapi/*.d qga/*.o qga/*.d
 	rm -f qemu-img-cmds.h
@@ -385,4 +387,4 @@  tarbin:
 	$(mandir)/man8/qemu-nbd.8
 
 # Include automatically generated dependency files
--include $(wildcard *.d audio/*.d slirp/*.d block/*.d net/*.d ui/*.d qapi/*.d)
+-include $(wildcard *.d audio/*.d slirp/*.d block/*.d net/*.d ui/*.d qapi/*.d qga/*.d)
diff --git a/qemu-ga.c b/qemu-ga.c
new file mode 100644
index 0000000..eb09100
--- /dev/null
+++ b/qemu-ga.c
@@ -0,0 +1,667 @@ 
+/*
+ * QEMU Guest Agent
+ *
+ * Copyright IBM Corp. 2011
+ *
+ * Authors:
+ *  Adam Litke        <aglitke@linux.vnet.ibm.com>
+ *  Michael Roth      <mdroth@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <glib.h>
+#include <gio/gio.h>
+#include <getopt.h>
+#include <termios.h>
+#include <syslog.h>
+#include "qemu_socket.h"
+#include "json-streamer.h"
+#include "json-parser.h"
+#include "qint.h"
+#include "qjson.h"
+#include "qga/guest-agent-core.h"
+#include "module.h"
+#include "signal.h"
+#include "qerror.h"
+#include "error_int.h"
+
+#define QGA_VIRTIO_PATH_DEFAULT "/dev/virtio-ports/org.qemu.guest_agent.0"
+#define QGA_PIDFILE_DEFAULT "/var/run/qemu-ga.pid"
+#define QGA_BAUDRATE_DEFAULT B38400 /* for isa-serial channels */
+#define QGA_TIMEOUT_DEFAULT 30*1000 /* ms */
+
+struct GAState {
+    JSONMessageParser parser;
+    GMainLoop *main_loop;
+    guint conn_id;
+    GSocket *conn_sock;
+    GIOChannel *conn_channel;
+    guint listen_id;
+    GSocket *listen_sock;
+    GIOChannel *listen_channel;
+    const char *path;
+    const char *method;
+    bool virtio; /* fastpath to check for virtio to deal with poll() quirks */
+    GACommandState *command_state;
+    GLogLevelFlags log_level;
+    FILE *log_file;
+    bool logging_enabled;
+};
+
+static struct GAState *ga_state;
+
+static void quit_handler(int sig)
+{
+    g_debug("recieved signal num %d, quitting", sig);
+
+    if (g_main_loop_is_running(ga_state->main_loop)) {
+        g_main_loop_quit(ga_state->main_loop);
+    }
+}
+
+static void register_signal_handlers(void)
+{
+    struct sigaction sigact;
+    int ret;
+
+    memset(&sigact, 0, sizeof(struct sigaction));
+    sigact.sa_handler = quit_handler;
+
+    ret = sigaction(SIGINT, &sigact, NULL);
+    if (ret == -1) {
+        g_error("error configuring signal handler: %s", strerror(errno));
+        exit(EXIT_FAILURE);
+    }
+    ret = sigaction(SIGTERM, &sigact, NULL);
+    if (ret == -1) {
+        g_error("error configuring signal handler: %s", strerror(errno));
+    }
+}
+
+static void usage(const char *cmd)
+{
+    printf(
+"Usage: %s -c <channel_opts>\n"
+"QEMU Guest Agent %s\n"
+"\n"
+"  -m, --method      transport method: one of unix-listen, virtio-serial, or\n"
+"                    isa-serial (virtio-serial is the default)\n"
+"  -p, --path        device/socket path (%s is the default for virtio-serial)\n"
+"  -l, --logfile     set logfile path, logs to stderr by default\n"
+"  -f, --pidfile     specify pidfile (default is %s)\n"
+"  -v, --verbose     log extra debugging information\n"
+"  -V, --version     print version information and exit\n"
+"  -d, --daemonize   become a daemon\n"
+"  -h, --help        display this help and exit\n"
+"\n"
+"Report bugs to <mdroth@linux.vnet.ibm.com>\n"
+    , cmd, QGA_VERSION, QGA_VIRTIO_PATH_DEFAULT, QGA_PIDFILE_DEFAULT);
+}
+
+static void conn_channel_close(GAState *s);
+
+static const char *ga_log_level_str(GLogLevelFlags level)
+{
+    switch (level & G_LOG_LEVEL_MASK) {
+        case G_LOG_LEVEL_ERROR:
+            return "error";
+        case G_LOG_LEVEL_CRITICAL:
+            return "critical";
+        case G_LOG_LEVEL_WARNING:
+            return "warning";
+        case G_LOG_LEVEL_MESSAGE:
+            return "message";
+        case G_LOG_LEVEL_INFO:
+            return "info";
+        case G_LOG_LEVEL_DEBUG:
+            return "debug";
+        default:
+            return "user";
+    }
+}
+
+bool ga_logging_enabled(GAState *s)
+{
+    return s->logging_enabled;
+}
+
+void ga_disable_logging(GAState *s)
+{
+    s->logging_enabled = false;
+}
+
+void ga_enable_logging(GAState *s)
+{
+    s->logging_enabled = true;
+}
+
+static void ga_log(const gchar *domain, GLogLevelFlags level,
+                   const gchar *msg, gpointer opaque)
+{
+    GAState *s = opaque;
+    GTimeVal time;
+    const char *level_str = ga_log_level_str(level);
+
+    if (!ga_logging_enabled(s)) {
+        return;
+    }
+
+    level &= G_LOG_LEVEL_MASK;
+    if (g_strcmp0(domain, "syslog") == 0) {
+        syslog(LOG_INFO, "%s: %s", level_str, msg);
+    } else if (level & s->log_level) {
+        g_get_current_time(&time);
+        fprintf(s->log_file,
+                "%lu.%lu: %s: %s\n", time.tv_sec, time.tv_usec, level_str, msg);
+        fflush(s->log_file);
+    }
+}
+
+static void become_daemon(const char *pidfile)
+{
+    pid_t pid, sid;
+    int pidfd;
+    char *pidstr = NULL;
+
+    pid = fork();
+    if (pid < 0) {
+        exit(EXIT_FAILURE);
+    }
+    if (pid > 0) {
+        exit(EXIT_SUCCESS);
+    }
+
+    pidfd = open(pidfile, O_CREAT|O_WRONLY|O_EXCL, S_IRUSR|S_IWUSR);
+    if (pidfd == -1) {
+        g_critical("Cannot create pid file, %s", strerror(errno));
+        exit(EXIT_FAILURE);
+    }
+
+    if (asprintf(&pidstr, "%d", getpid()) == -1) {
+        g_critical("Cannot allocate memory");
+        goto fail;
+    }
+    if (write(pidfd, pidstr, strlen(pidstr)) != strlen(pidstr)) {
+        free(pidstr);
+        g_critical("Failed to write pid file");
+        goto fail;
+    }
+
+    umask(0);
+    sid = setsid();
+    if (sid < 0) {
+        goto fail;
+    }
+    if ((chdir("/")) < 0) {
+        goto fail;
+    }
+
+    close(STDIN_FILENO);
+    close(STDOUT_FILENO);
+    close(STDERR_FILENO);
+    free(pidstr);
+    return;
+
+fail:
+    unlink(pidfile);
+    g_critical("failed to daemonize");
+    exit(EXIT_FAILURE);
+}
+
+static int conn_channel_send_buf(GIOChannel *channel, const char *buf,
+                                 gsize count)
+{
+    GError *err = NULL;
+    gsize written = 0;
+    GIOStatus status;
+
+    while (count) {
+        status = g_io_channel_write_chars(channel, buf, count, &written, &err);
+        g_debug("sending data, count: %d", (int)count);
+        if (err != NULL) {
+            g_warning("error sending newline: %s", err->message);
+            return err->code;
+        }
+        if (status == G_IO_STATUS_ERROR || status == G_IO_STATUS_EOF) {
+            return -EPIPE;
+        }
+
+        if (status == G_IO_STATUS_NORMAL) {
+            count -= written;
+        }
+    }
+
+    return 0;
+}
+
+static int conn_channel_send_payload(GIOChannel *channel, QObject *payload)
+{
+    int ret = 0;
+    const char *buf;
+    QString *payload_qstr;
+    GError *err = NULL;
+
+    g_assert(payload && channel);
+
+    payload_qstr = qobject_to_json(payload);
+    if (!payload_qstr) {
+        return -EINVAL;
+    }
+
+    qstring_append_chr(payload_qstr, '\n');
+    buf = qstring_get_str(payload_qstr);
+    ret = conn_channel_send_buf(channel, buf, strlen(buf));
+    if (ret) {
+        goto out_free;
+    }
+
+    g_io_channel_flush(channel, &err);
+    if (err != NULL) {
+        g_warning("error flushing payload: %s", err->message);
+        ret = err->code;
+        goto out_free;
+    }
+
+out_free:
+    QDECREF(payload_qstr);
+    if (err) {
+        g_error_free(err);
+    }
+    return ret;
+}
+
+static void process_command(GAState *s, QDict *req)
+{
+    QObject *rsp = NULL;
+    int ret;
+
+    g_assert(req);
+    g_debug("processing command");
+    rsp = qmp_dispatch(QOBJECT(req));
+    if (rsp) {
+        ret = conn_channel_send_payload(s->conn_channel, rsp);
+        if (ret) {
+            g_warning("error sending payload: %s", strerror(ret));
+        }
+        qobject_decref(rsp);
+    } else {
+        g_warning("error getting response");
+    }
+}
+
+/* handle requests/control events coming in over the channel */
+static void process_event(JSONMessageParser *parser, QList *tokens)
+{
+    GAState *s = container_of(parser, GAState, parser);
+    QObject *obj;
+    QDict *qdict;
+    Error *err = NULL;
+    int ret;
+
+    g_assert(s && parser);
+
+    g_debug("process_event: called");
+    obj = json_parser_parse_err(tokens, NULL, &err);
+    if (err || !obj || qobject_type(obj) != QTYPE_QDICT) {
+        qobject_decref(obj);
+        qdict = qdict_new();
+        if (!err) {
+            g_warning("failed to parse event: unknown error");
+            error_set(&err, QERR_JSON_PARSING);
+        } else {
+            g_warning("failed to parse event: %s", error_get_pretty(err));
+        }
+        qdict_put_obj(qdict, "error", error_get_qobject(err));
+        error_free(err);
+    } else {
+        qdict = qobject_to_qdict(obj);
+    }
+
+    g_assert(qdict);
+
+    /* handle host->guest commands */
+    if (qdict_haskey(qdict, "execute")) {
+        process_command(s, qdict);
+    } else {
+        if (!qdict_haskey(qdict, "error")) {
+            QDECREF(qdict);
+            qdict = qdict_new();
+            g_warning("unrecognized payload format");
+            error_set(&err, QERR_UNSUPPORTED);
+            qdict_put_obj(qdict, "error", error_get_qobject(err));
+            error_free(err);
+        }
+        ret = conn_channel_send_payload(s->conn_channel, QOBJECT(qdict));
+        if (ret) {
+            g_warning("error sending payload: %s", strerror(ret));
+        }
+    }
+
+    QDECREF(qdict);
+}
+
+static gboolean conn_channel_read(GIOChannel *channel, GIOCondition condition,
+                                  gpointer data)
+{
+    GAState *s = data;
+    gchar buf[1024];
+    gsize count;
+    GError *err = NULL;
+    memset(buf, 0, 1024);
+    GIOStatus status = g_io_channel_read_chars(channel, buf, 1024,
+                                               &count, &err);
+    if (err != NULL) {
+        g_warning("error reading channel: %s", err->message);
+        conn_channel_close(s);
+        g_error_free(err);
+        return false;
+    }
+    switch (status) {
+    case G_IO_STATUS_ERROR:
+        g_warning("problem");
+        return false;
+    case G_IO_STATUS_NORMAL:
+        g_debug("read data, count: %d, data: %s", (int)count, buf);
+        json_message_parser_feed(&s->parser, (char *)buf, (int)count);
+    case G_IO_STATUS_AGAIN:
+        /* virtio causes us to spin here when no process is attached to
+         * host-side chardev. sleep a bit to mitigate this
+         */
+        if (s->virtio) {
+            usleep(100*1000);
+        }
+        return true;
+    case G_IO_STATUS_EOF:
+        g_debug("received EOF");
+        conn_channel_close(s);
+        if (s->virtio) {
+            return true;
+        }
+        return false;
+    default:
+        g_warning("unknown channel read status, closing");
+        conn_channel_close(s);
+        return false;
+    }
+    return true;
+}
+
+static int conn_channel_add(GAState *s, int fd)
+{
+    GIOChannel *conn_channel;
+    guint conn_id;
+    GError *err = NULL;
+
+    g_assert(s && !s->conn_channel);
+    conn_channel = g_io_channel_unix_new(fd);
+    g_assert(conn_channel);
+    g_io_channel_set_encoding(conn_channel, NULL, &err);
+    if (err != NULL) {
+        g_warning("error setting channel encoding to binary");
+        g_error_free(err);
+        return -1;
+    }
+    conn_id = g_io_add_watch(conn_channel, G_IO_IN | G_IO_HUP,
+                             conn_channel_read, s);
+    if (err != NULL) {
+        g_warning("error adding io watch: %s", err->message);
+        g_error_free(err);
+        return -1;
+    }
+    s->conn_channel = conn_channel;
+    s->conn_id = conn_id;
+    return 0;
+}
+
+static gboolean listen_channel_accept(GIOChannel *channel,
+                                      GIOCondition condition, gpointer data)
+{
+    GAState *s = data;
+    GError *err = NULL;
+    g_assert(channel != NULL);
+    int ret;
+    bool accepted = false;
+
+    s->conn_sock = g_socket_accept(s->listen_sock, NULL, &err);
+    if (err != NULL) {
+        g_warning("error converting fd to gsocket: %s", err->message);
+        g_error_free(err);
+        goto out;
+    }
+    ret = conn_channel_add(s, g_socket_get_fd(s->conn_sock));
+    if (ret) {
+        g_warning("error setting up connection");
+        goto out;
+    }
+    accepted = true;
+
+out:
+    /* only accept 1 connection at a time */
+    return !accepted;
+}
+
+/* start polling for readable events on listen fd, new==true
+ * indicates we should use the existing s->listen_channel
+ */
+static int listen_channel_add(GAState *s, int listen_fd, bool new)
+{
+    GError *err = NULL;
+    guint listen_id;
+
+    if (new) {
+        s->listen_channel = g_io_channel_unix_new(listen_fd);
+        if (s->listen_sock) {
+            g_object_unref(s->listen_sock);
+        }
+        s->listen_sock = g_socket_new_from_fd(listen_fd, &err);
+        if (err != NULL) {
+            g_warning("error converting fd to gsocket: %s", err->message);
+            g_error_free(err);
+            return -1;
+        }
+    }
+    listen_id = g_io_add_watch(s->listen_channel, G_IO_IN,
+                               listen_channel_accept, s);
+    if (err != NULL) {
+        g_warning("error adding io watch: %s", err->message);
+        g_error_free(err);
+        return -1;
+    }
+    return 0;
+}
+
+/* cleanup state for closed connection/session, start accepting new
+ * connections if we're in listening mode
+ */
+static void conn_channel_close(GAState *s)
+{
+    if (strcmp(s->method, "unix-listen") == 0) {
+        g_io_channel_shutdown(s->conn_channel, true, NULL);
+        g_object_unref(s->conn_sock);
+        s->conn_sock = NULL;
+        listen_channel_add(s, 0, false);
+    } else if (strcmp(s->method, "virtio-serial") == 0) {
+        /* we spin on EOF for virtio-serial, so back off a bit. also,
+         * dont close the connection in this case, it'll resume normal
+         * operation when another process connects to host chardev
+         */
+        usleep(100*1000);
+        goto out_noclose;
+    }
+    g_io_channel_unref(s->conn_channel);
+    s->conn_channel = NULL;
+    s->conn_id = 0;
+out_noclose:
+    return;
+}
+
+static void init_guest_agent(GAState *s)
+{
+    struct termios tio;
+    int ret, fd;
+
+    if (s->method == NULL) {
+        /* try virtio-serial as our default */
+        s->method = "virtio-serial";
+    }
+
+    if (s->path == NULL) {
+        if (strcmp(s->method, "virtio-serial") != 0) {
+            g_critical("must specify a path for this channel");
+            exit(EXIT_FAILURE);
+        }
+        /* try the default path for the virtio-serial port */
+        s->path = QGA_VIRTIO_PATH_DEFAULT;
+    }
+
+    if (strcmp(s->method, "virtio-serial") == 0) {
+        s->virtio = true;
+        fd = qemu_open(s->path, O_RDWR | O_NONBLOCK | O_ASYNC);
+        if (fd == -1) {
+            g_critical("error opening channel: %s", strerror(errno));
+            exit(EXIT_FAILURE);
+        }
+        ret = conn_channel_add(s, fd);
+        if (ret) {
+            g_critical("error adding channel to main loop");
+            exit(EXIT_FAILURE);
+        }
+    } else if (strcmp(s->method, "isa-serial") == 0) {
+        fd = qemu_open(s->path, O_RDWR | O_NOCTTY);
+        if (fd == -1) {
+            g_critical("error opening channel: %s", strerror(errno));
+            exit(EXIT_FAILURE);
+        }
+        tcgetattr(fd, &tio);
+        /* set up serial port for non-canonical, dumb byte streaming */
+        tio.c_iflag &= ~(IGNBRK | BRKINT | IGNPAR | PARMRK | INPCK | ISTRIP |
+                         INLCR | IGNCR | ICRNL | IXON | IXOFF | IXANY |
+                         IMAXBEL);
+        tio.c_oflag = 0;
+        tio.c_lflag = 0;
+        tio.c_cflag |= QGA_BAUDRATE_DEFAULT;
+        /* 1 available byte min or reads will block (we'll set non-blocking
+         * elsewhere, else we have to deal with read()=0 instead)
+         */
+        tio.c_cc[VMIN] = 1;
+        tio.c_cc[VTIME] = 0;
+        /* flush everything waiting for read/xmit, it's garbage at this point */
+        tcflush(fd, TCIFLUSH);
+        tcsetattr(fd, TCSANOW, &tio);
+        ret = conn_channel_add(s, fd);
+        if (ret) {
+            g_error("error adding channel to main loop");
+        }
+    } else if (strcmp(s->method, "unix-listen") == 0) {
+        fd = unix_listen(s->path, NULL, strlen(s->path));
+        if (fd == -1) {
+            g_critical("error opening path: %s", strerror(errno));
+            exit(EXIT_FAILURE);
+        }
+        ret = listen_channel_add(s, fd, true);
+        if (ret) {
+            g_critical("error binding/listening to specified socket");
+            exit(EXIT_FAILURE);
+        }
+    } else {
+        g_critical("unsupported channel method/type: %s", s->method);
+        exit(EXIT_FAILURE);
+    }
+
+    json_message_parser_init(&s->parser, process_event);
+    s->main_loop = g_main_loop_new(NULL, false);
+}
+
+int main(int argc, char **argv)
+{
+    const char *sopt = "hVvdm:p:l:f:";
+    const char *method = NULL, *path = NULL, *pidfile = QGA_PIDFILE_DEFAULT;
+    const struct option lopt[] = {
+        { "help", 0, NULL, 'h' },
+        { "version", 0, NULL, 'V' },
+        { "logfile", 0, NULL, 'l' },
+        { "pidfile", 0, NULL, 'f' },
+        { "verbose", 0, NULL, 'v' },
+        { "method", 0, NULL, 'm' },
+        { "path", 0, NULL, 'p' },
+        { "daemonize", 0, NULL, 'd' },
+        { NULL, 0, NULL, 0 }
+    };
+    int opt_ind = 0, ch, daemonize = 0;
+    GLogLevelFlags log_level = G_LOG_LEVEL_ERROR | G_LOG_LEVEL_CRITICAL;
+    FILE *log_file = stderr;
+    GAState *s;
+
+    while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) {
+        switch (ch) {
+        case 'm':
+            method = optarg;
+            break;
+        case 'p':
+            path = optarg;
+            break;
+        case 'l':
+            log_file = fopen(optarg, "a");
+            if (!log_file) {
+                g_critical("unable to open specified log file: %s",
+                           strerror(errno));
+                return EXIT_FAILURE;
+            }
+            break;
+        case 'f':
+            pidfile = optarg;
+            break;
+        case 'v':
+            /* enable all log levels */
+            log_level = G_LOG_LEVEL_MASK;
+            break;
+        case 'V':
+            printf("QEMU Guest Agent %s\n", QGA_VERSION);
+            return 0;
+        case 'd':
+            daemonize = 1;
+            break;
+        case 'h':
+            usage(argv[0]);
+            return 0;
+        case '?':
+            g_print("Unknown option, try '%s --help' for more information.\n",
+                    argv[0]);
+            return EXIT_FAILURE;
+        }
+    }
+
+    if (daemonize) {
+        g_debug("starting daemon");
+        become_daemon(pidfile);
+    }
+
+    g_type_init();
+    g_thread_init(NULL);
+
+    s = qemu_mallocz(sizeof(GAState));
+    s->conn_id = 0;
+    s->conn_channel = NULL;
+    s->path = path;
+    s->method = method;
+    s->log_file = log_file;
+    s->log_level = log_level;
+    g_log_set_default_handler(ga_log, s);
+    g_log_set_fatal_mask(NULL, G_LOG_LEVEL_ERROR);
+    s->logging_enabled = true;
+    ga_state = s;
+
+    module_call_init(MODULE_INIT_QAPI);
+    init_guest_agent(ga_state);
+    register_signal_handlers();
+
+    g_main_loop_run(ga_state->main_loop);
+
+    unlink(pidfile);
+
+    return 0;
+}
diff --git a/qga/guest-agent-core.h b/qga/guest-agent-core.h
index 688f120..66d1729 100644
--- a/qga/guest-agent-core.h
+++ b/qga/guest-agent-core.h
@@ -15,6 +15,7 @@ 
 
 #define QGA_VERSION "1.0"
 
+typedef struct GAState GAState;
 typedef struct GACommandState GACommandState;
 
 void ga_command_state_add(GACommandState *cs,
@@ -23,3 +24,6 @@  void ga_command_state_add(GACommandState *cs,
 void ga_command_state_init_all(GACommandState *cs);
 void ga_command_state_cleanup_all(GACommandState *cs);
 GACommandState *ga_command_state_new(void);
+bool ga_logging_enabled(GAState *s);
+void ga_disable_logging(GAState *s);
+void ga_enable_logging(GAState *s);