Patchwork [v6,2/4] guest agent: qemu-ga daemon

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Submitter Michael Roth
Date July 5, 2011, 1:21 p.m.
Message ID <1309872100-27912-3-git-send-email-mdroth@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/103310/
State New
Headers show

Comments

Michael Roth - July 5, 2011, 1:21 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 -c virtio-serial -p /dev/virtio-ports/org.qemu.guest_agent \
          -p /var/run/qemu-guest-agent.pid -d

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 Makefile               |   10 +-
 qemu-ga.c              |  651 ++++++++++++++++++++++++++++++++++++++++++++++++
 qga/guest-agent-core.h |    4 +
 3 files changed, 661 insertions(+), 4 deletions(-)
 create mode 100644 qemu-ga.c
Luiz Capitulino - July 8, 2011, 2:36 p.m.
On Tue,  5 Jul 2011 08:21:38 -0500
Michael Roth <mdroth@linux.vnet.ibm.com> wrote:

> 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 -c virtio-serial -p /dev/virtio-ports/org.qemu.guest_agent \
>           -p /var/run/qemu-guest-agent.pid -d

I think you meant -f /var/run/qemu-guest-agent.pid

> 
> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> ---
>  Makefile               |   10 +-
>  qemu-ga.c              |  651 ++++++++++++++++++++++++++++++++++++++++++++++++
>  qga/guest-agent-core.h |    4 +
>  3 files changed, 661 insertions(+), 4 deletions(-)
>  create mode 100644 qemu-ga.c
> 
> 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..649c16a
> --- /dev/null
> +++ b/qemu-ga.c
> @@ -0,0 +1,651 @@
> +/*
> + * 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"
> +
> +#define QGA_VIRTIO_PATH_DEFAULT "/dev/virtio-ports/org.qemu.guest_agent"
> +#define QGA_PIDFILE_DEFAULT "/var/run/qemu-va.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");
> +
> +    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;
> +
> +    sigact.sa_handler = quit_handler;
> +
> +    ret = sigaction(SIGINT, &sigact, NULL);
> +    if (ret == -1) {
> +        g_error("error configuring signal handler: %s", strerror(errno));
> +    }
> +    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"
> +"  -c, --channel     channel method: one of unix-connect, virtio-serial, or\n"
> +"                    isa-serial (virtio-serial is the default)\n"
> +"  -p, --path        channel 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_error("Cannot create pid file, %s", strerror(errno));
> +    }
> +
> +    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_error("failed to daemonize");
> +}
> +
> +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;
> +    }

You can do:

 qstring_append_chr(payload_qstr, '\n');

so that you avoid the additional conn_channel_send_buf() call below.

> +
> +    buf = qstring_get_str(payload_qstr);
> +    ret = conn_channel_send_buf(channel, buf, strlen(buf));
> +    if (ret) {
> +        goto out_free;
> +    }
> +
> +    ret = conn_channel_send_buf(channel, "\n", 1);
> +    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;
> +
> +    g_assert(s && parser);
> +
> +    g_debug("process_event: called");
> +    obj = json_parser_parse_err(tokens, NULL, &err);
> +    if (!obj || qobject_type(obj) != QTYPE_QDICT) {
> +        qobject_decref(obj);
> +        g_warning("failed to parse event");

No error is returned to the client, is this intended?

> +        return;
> +    }
> +
> +    if (err) {
> +        error_free(err);
> +        g_warning("failed to parse event: %s", error_get_pretty(err));

Same here.

> +        return;
> +    }
> +
> +    g_debug("parse successful");
> +    qdict = qobject_to_qdict(obj);
> +    g_assert(qdict);
> +
> +    /* handle host->guest commands */
> +    if (qdict_haskey(qdict, "execute")) {
> +        process_command(s, qdict);
> +    } else {

And here.

> +        g_warning("unrecognized payload format, ignoring");
> +    }
> +
> +    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_error("must specify a path for this channel");
> +        }
> +        /* 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);
> +        if (fd == -1) {
> +            g_error("error opening channel: %s", strerror(errno));
> +        }
> +        ret = fcntl(fd, F_GETFL);
> +        if (ret < 0) {
> +            g_error("error getting channel flags: %s", strerror(errno));
> +        }
> +        ret = fcntl(fd, F_SETFL, ret | O_NONBLOCK | O_ASYNC);
> +        if (ret < 0) {
> +            g_error("error setting channel flags: %s", strerror(errno));
> +        }

Can't O_NONBLOCK and O_ASYNC be set as open() flags?

> +        ret = conn_channel_add(s, fd);
> +        if (ret) {
> +            g_error("error adding channel to main loop");
> +        }
> +    } else if (strcmp(s->method, "isa-serial") == 0) {
> +        fd = qemu_open(s->path, O_RDWR | O_NOCTTY);
> +        if (fd == -1) {
> +            g_error("error opening channel: %s", strerror(errno));
> +        }
> +        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_error("error opening path: %s", strerror(errno));
> +        }
> +        ret = listen_channel_add(s, fd, true);
> +        if (ret) {
> +            g_error("error binding/listening to specified socket");
> +        }
> +    } else {
> +        g_error("unsupported channel method/type: %s", s->method);
> +    }
> +
> +    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 = "hVvdc:p:l:f:";
> +    const char *method = NULL, *path = NULL, *pidfile = QGA_PIDFILE_DEFAULT;
> +    struct option lopt[] = {

Can be const.

> +        { "help", 0, NULL, 'h' },
> +        { "version", 0, NULL, 'V' },
> +        { "logfile", 0, NULL, 'l' },
> +        { "pidfile", 0, NULL, 'f' },
> +        { "verbose", 0, NULL, 'v' },
> +        { "channel", 0, NULL, 'c' },
> +        { "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 'c':
> +            method = optarg;

Why don't you call this option 'm' ('method') then?

> +            break;
> +        case 'p':
> +            path = optarg;
> +            break;
> +        case 'l':
> +            log_file = fopen(optarg, "a");
> +            if (!log_file) {
> +                g_error("unable to open specified log file: %s",
> +                        strerror(errno));
> +            }
> +            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_error("Unknown option, try '%s --help' for more information.",
> +                    argv[0]);

g_error() documentation from:

 http://developer.gnome.org/glib/2.29/glib-Message-Logging.html#g-error

Says:

 "This function will result in a core dump; don't use it for errors you expect.
  Using this function indicates a bug in your program, i.e. an assertion failure."

But I see it's being used beyond assertions.

> +        }
> +    }
> +
> +    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);
Michael Roth - July 8, 2011, 9:12 p.m.
On 07/08/2011 09:36 AM, Luiz Capitulino wrote:
> On Tue,  5 Jul 2011 08:21:38 -0500
> Michael Roth<mdroth@linux.vnet.ibm.com>  wrote:
>
>> 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 -c virtio-serial -p /dev/virtio-ports/org.qemu.guest_agent \
>>            -p /var/run/qemu-guest-agent.pid -d
>
> I think you meant -f /var/run/qemu-guest-agent.pid
>

Yup, sorry.

>>
>> Signed-off-by: Michael Roth<mdroth@linux.vnet.ibm.com>
>> ---
>>   Makefile               |   10 +-
>>   qemu-ga.c              |  651 ++++++++++++++++++++++++++++++++++++++++++++++++
>>   qga/guest-agent-core.h |    4 +
>>   3 files changed, 661 insertions(+), 4 deletions(-)
>>   create mode 100644 qemu-ga.c
>>
>> 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..649c16a
>> --- /dev/null
>> +++ b/qemu-ga.c
>> @@ -0,0 +1,651 @@
>> +/*
>> + * 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"
>> +
>> +#define QGA_VIRTIO_PATH_DEFAULT "/dev/virtio-ports/org.qemu.guest_agent"
>> +#define QGA_PIDFILE_DEFAULT "/var/run/qemu-va.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");
>> +
>> +    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;
>> +
>> +    sigact.sa_handler = quit_handler;
>> +
>> +    ret = sigaction(SIGINT,&sigact, NULL);
>> +    if (ret == -1) {
>> +        g_error("error configuring signal handler: %s", strerror(errno));
>> +    }
>> +    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"
>> +"  -c, --channel     channel method: one of unix-connect, virtio-serial, or\n"
>> +"                    isa-serial (virtio-serial is the default)\n"
>> +"  -p, --path        channel 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_error("Cannot create pid file, %s", strerror(errno));
>> +    }
>> +
>> +    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_error("failed to daemonize");
>> +}
>> +
>> +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;
>> +    }
>
> You can do:
>
>   qstring_append_chr(payload_qstr, '\n');
>
> so that you avoid the additional conn_channel_send_buf() call below.
>

Nice!

>> +
>> +    buf = qstring_get_str(payload_qstr);
>> +    ret = conn_channel_send_buf(channel, buf, strlen(buf));
>> +    if (ret) {
>> +        goto out_free;
>> +    }
>> +
>> +    ret = conn_channel_send_buf(channel, "\n", 1);
>> +    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;
>> +
>> +    g_assert(s&&  parser);
>> +
>> +    g_debug("process_event: called");
>> +    obj = json_parser_parse_err(tokens, NULL,&err);
>> +    if (!obj || qobject_type(obj) != QTYPE_QDICT) {
>> +        qobject_decref(obj);
>> +        g_warning("failed to parse event");
>
> No error is returned to the client, is this intended?
>

Hmm, nope... originally the errors got rolled into the response in 
qmp_dispatch(). But when I reworked qmp_dispatch() to take a pre-parsed 
QDict instead of a token list this functionality was lost..

Which makes me wonder if I should move the parsing back into 
qmp_dispatch()... I'll take a look. But yah, these errors should get 
returned.

>> +        return;
>> +    }
>> +
>> +    if (err) {
>> +        error_free(err);
>> +        g_warning("failed to parse event: %s", error_get_pretty(err));
>
> Same here.
>
>> +        return;
>> +    }
>> +
>> +    g_debug("parse successful");
>> +    qdict = qobject_to_qdict(obj);
>> +    g_assert(qdict);
>> +
>> +    /* handle host->guest commands */
>> +    if (qdict_haskey(qdict, "execute")) {
>> +        process_command(s, qdict);
>> +    } else {
>
> And here.
>
>> +        g_warning("unrecognized payload format, ignoring");
>> +    }
>> +
>> +    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_error("must specify a path for this channel");
>> +        }
>> +        /* 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);
>> +        if (fd == -1) {
>> +            g_error("error opening channel: %s", strerror(errno));
>> +        }
>> +        ret = fcntl(fd, F_GETFL);
>> +        if (ret<  0) {
>> +            g_error("error getting channel flags: %s", strerror(errno));
>> +        }
>> +        ret = fcntl(fd, F_SETFL, ret | O_NONBLOCK | O_ASYNC);
>> +        if (ret<  0) {
>> +            g_error("error setting channel flags: %s", strerror(errno));
>> +        }
>
> Can't O_NONBLOCK and O_ASYNC be set as open() flags?
>
>> +        ret = conn_channel_add(s, fd);
>> +        if (ret) {
>> +            g_error("error adding channel to main loop");
>> +        }
>> +    } else if (strcmp(s->method, "isa-serial") == 0) {
>> +        fd = qemu_open(s->path, O_RDWR | O_NOCTTY);
>> +        if (fd == -1) {
>> +            g_error("error opening channel: %s", strerror(errno));
>> +        }
>> +        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_error("error opening path: %s", strerror(errno));
>> +        }
>> +        ret = listen_channel_add(s, fd, true);
>> +        if (ret) {
>> +            g_error("error binding/listening to specified socket");
>> +        }
>> +    } else {
>> +        g_error("unsupported channel method/type: %s", s->method);
>> +    }
>> +
>> +    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 = "hVvdc:p:l:f:";
>> +    const char *method = NULL, *path = NULL, *pidfile = QGA_PIDFILE_DEFAULT;
>> +    struct option lopt[] = {
>
> Can be const.
>
>> +        { "help", 0, NULL, 'h' },
>> +        { "version", 0, NULL, 'V' },
>> +        { "logfile", 0, NULL, 'l' },
>> +        { "pidfile", 0, NULL, 'f' },
>> +        { "verbose", 0, NULL, 'v' },
>> +        { "channel", 0, NULL, 'c' },
>> +        { "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 'c':
>> +            method = optarg;
>
> Why don't you call this option 'm' ('method') then?
>

That's probably better.

>> +            break;
>> +        case 'p':
>> +            path = optarg;
>> +            break;
>> +        case 'l':
>> +            log_file = fopen(optarg, "a");
>> +            if (!log_file) {
>> +                g_error("unable to open specified log file: %s",
>> +                        strerror(errno));
>> +            }
>> +            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_error("Unknown option, try '%s --help' for more information.",
>> +                    argv[0]);
>
> g_error() documentation from:
>
>   http://developer.gnome.org/glib/2.29/glib-Message-Logging.html#g-error
>
> Says:
>
>   "This function will result in a core dump; don't use it for errors you expect.
>    Using this function indicates a bug in your program, i.e. an assertion failure."
>
> But I see it's being used beyond assertions.
>

I've been using it to bail on unrecoverable error states. Might be a bit 
extreme for unknown options though.

>> +        }
>> +    }
>> +
>> +    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);
>

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..649c16a
--- /dev/null
+++ b/qemu-ga.c
@@ -0,0 +1,651 @@ 
+/*
+ * 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"
+
+#define QGA_VIRTIO_PATH_DEFAULT "/dev/virtio-ports/org.qemu.guest_agent"
+#define QGA_PIDFILE_DEFAULT "/var/run/qemu-va.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");
+
+    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;
+
+    sigact.sa_handler = quit_handler;
+
+    ret = sigaction(SIGINT, &sigact, NULL);
+    if (ret == -1) {
+        g_error("error configuring signal handler: %s", strerror(errno));
+    }
+    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"
+"  -c, --channel     channel method: one of unix-connect, virtio-serial, or\n"
+"                    isa-serial (virtio-serial is the default)\n"
+"  -p, --path        channel 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_error("Cannot create pid file, %s", strerror(errno));
+    }
+
+    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_error("failed to daemonize");
+}
+
+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;
+    }
+
+    buf = qstring_get_str(payload_qstr);
+    ret = conn_channel_send_buf(channel, buf, strlen(buf));
+    if (ret) {
+        goto out_free;
+    }
+
+    ret = conn_channel_send_buf(channel, "\n", 1);
+    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;
+
+    g_assert(s && parser);
+
+    g_debug("process_event: called");
+    obj = json_parser_parse_err(tokens, NULL, &err);
+    if (!obj || qobject_type(obj) != QTYPE_QDICT) {
+        qobject_decref(obj);
+        g_warning("failed to parse event");
+        return;
+    }
+
+    if (err) {
+        error_free(err);
+        g_warning("failed to parse event: %s", error_get_pretty(err));
+        return;
+    }
+
+    g_debug("parse successful");
+    qdict = qobject_to_qdict(obj);
+    g_assert(qdict);
+
+    /* handle host->guest commands */
+    if (qdict_haskey(qdict, "execute")) {
+        process_command(s, qdict);
+    } else {
+        g_warning("unrecognized payload format, ignoring");
+    }
+
+    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_error("must specify a path for this channel");
+        }
+        /* 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);
+        if (fd == -1) {
+            g_error("error opening channel: %s", strerror(errno));
+        }
+        ret = fcntl(fd, F_GETFL);
+        if (ret < 0) {
+            g_error("error getting channel flags: %s", strerror(errno));
+        }
+        ret = fcntl(fd, F_SETFL, ret | O_NONBLOCK | O_ASYNC);
+        if (ret < 0) {
+            g_error("error setting channel flags: %s", strerror(errno));
+        }
+        ret = conn_channel_add(s, fd);
+        if (ret) {
+            g_error("error adding channel to main loop");
+        }
+    } else if (strcmp(s->method, "isa-serial") == 0) {
+        fd = qemu_open(s->path, O_RDWR | O_NOCTTY);
+        if (fd == -1) {
+            g_error("error opening channel: %s", strerror(errno));
+        }
+        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_error("error opening path: %s", strerror(errno));
+        }
+        ret = listen_channel_add(s, fd, true);
+        if (ret) {
+            g_error("error binding/listening to specified socket");
+        }
+    } else {
+        g_error("unsupported channel method/type: %s", s->method);
+    }
+
+    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 = "hVvdc:p:l:f:";
+    const char *method = NULL, *path = NULL, *pidfile = QGA_PIDFILE_DEFAULT;
+    struct option lopt[] = {
+        { "help", 0, NULL, 'h' },
+        { "version", 0, NULL, 'V' },
+        { "logfile", 0, NULL, 'l' },
+        { "pidfile", 0, NULL, 'f' },
+        { "verbose", 0, NULL, 'v' },
+        { "channel", 0, NULL, 'c' },
+        { "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 'c':
+            method = optarg;
+            break;
+        case 'p':
+            path = optarg;
+            break;
+        case 'l':
+            log_file = fopen(optarg, "a");
+            if (!log_file) {
+                g_error("unable to open specified log file: %s",
+                        strerror(errno));
+            }
+            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_error("Unknown option, try '%s --help' for more information.",
+                    argv[0]);
+        }
+    }
+
+    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);