[Qemu-devel] [PATCH 25/25] guest agent: add guest agent RPCs/commands

[Luiz Capitulino]

From: Michael Roth <address@hidden>

This adds the initial set of QMP/QAPI commands provided by the guest
agent:

guest-sync
guest-ping
guest-info
guest-shutdown
guest-file-open
guest-file-read
guest-file-write
guest-file-seek
guest-file-flush
guest-file-close
guest-fsfreeze-freeze
guest-fsfreeze-thaw
guest-fsfreeze-status

The input/output specification for these commands are documented in the
schema.

Example usage:

  host:
    qemu -device virtio-serial \
         -chardev socket,path=/tmp/vs0.sock,server,nowait,id=qga0 \
         -device virtserialport,chardev=qga0,name=org.qemu.quest_agent.0
         ...

    echo "{'execute':'guest-info'}" | socat stdio unix-connect:/tmp/qga0.sock

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

Signed-off-by: Michael Roth <address@hidden>
Signed-off-by: Luiz Capitulino <address@hidden>
---
 Makefile                   |   16 +-
 qapi-schema-guest.json     |  217 ++++++++++++++++++
 qemu-ga.c                  |    4 +
 qerror.c                   |    8 +
 qerror.h                   |    6 +
 qga/guest-agent-commands.c |  518 ++++++++++++++++++++++++++++++++++++++++++++
 qga/guest-agent-core.h     |    2 +
 7 files changed, 768 insertions(+), 3 deletions(-)
 create mode 100644 qapi-schema-guest.json
 create mode 100644 qga/guest-agent-commands.c

diff --git a/Makefile b/Makefile
index 0d2e33d..f3a03ad 100644
--- a/Makefile
+++ b/Makefile
@@ -164,7 +164,7 @@ check-qjson: check-qjson.o qfloat.o qint.o qdict.o 
qstring.o qlist.o qbool.o qjs
 
 $(qapi-obj-y): $(GENERATED_HEADERS)
 qapi-dir := qapi-generated
-test-visitor.o test-qmp-commands.o: QEMU_CFLAGS += -I $(qapi-dir)
+test-visitor.o test-qmp-commands.o qemu-ga$(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
@@ -176,15 +176,25 @@ $(qapi-dir)/test-qmp-commands.h: 
$(qapi-dir)/test-qmp-marshal.c
 $(qapi-dir)/test-qmp-marshal.c: $(SRC_PATH)/qapi-schema-test.json 
$(SRC_PATH)/scripts/qapi-commands.py
            $(call quiet-command,python $(SRC_PATH)/scripts/qapi-commands.py -o 
"$(qapi-dir)" -p "test-" < $<, "  GEN   $@")
 
+$(qapi-dir)/qga-qapi-types.c: $(qapi-dir)/qga-qapi-types.h
+$(qapi-dir)/qga-qapi-types.h: $(SRC_PATH)/qapi-schema-guest.json 
$(SRC_PATH)/scripts/qapi-types.py
+       $(call quiet-command,python $(SRC_PATH)/scripts/qapi-types.py -o 
"$(qapi-dir)" -p "qga-" < $<, "  GEN   $@")
+$(qapi-dir)/qga-qapi-visit.c: $(qapi-dir)/qga-qapi-visit.h
+$(qapi-dir)/qga-qapi-visit.h: $(SRC_PATH)/qapi-schema-guest.json 
$(SRC_PATH)/scripts/qapi-visit.py
+       $(call quiet-command,python $(SRC_PATH)/scripts/qapi-visit.py -o 
"$(qapi-dir)" -p "qga-" < $<, "  GEN   $@")
+$(qapi-dir)/qga-qmp-marshal.c: $(SRC_PATH)/qapi-schema-guest.json 
$(SRC_PATH)/scripts/qapi-commands.py
+       $(call quiet-command,python $(SRC_PATH)/scripts/qapi-commands.py -o 
"$(qapi-dir)" -p "qga-" < $<, "  GEN   $@")
+
 test-visitor.o: $(addprefix $(qapi-dir)/, test-qapi-types.c test-qapi-types.h 
test-qapi-visit.c test-qapi-visit.h) $(qapi-obj-y)
 test-visitor: test-visitor.o qfloat.o qint.o qdict.o qstring.o qlist.o qbool.o 
$(qapi-obj-y) error.o osdep.o qemu-malloc.o $(oslib-obj-y) qjson.o 
json-streamer.o json-lexer.o json-parser.o qerror.o qemu-error.o qemu-tool.o 
$(qapi-dir)/test-qapi-visit.o $(qapi-dir)/test-qapi-types.o
 
 test-qmp-commands.o: $(addprefix $(qapi-dir)/, test-qapi-types.c 
test-qapi-types.h test-qapi-visit.c test-qapi-visit.h test-qmp-marshal.c 
test-qmp-commands.h) $(qapi-obj-y)
 test-qmp-commands: test-qmp-commands.o qfloat.o qint.o qdict.o qstring.o 
qlist.o qbool.o $(qapi-obj-y) error.o osdep.o qemu-malloc.o $(oslib-obj-y) 
qjson.o json-streamer.o json-lexer.o json-parser.o qerror.o qemu-error.o 
qemu-tool.o $(qapi-dir)/test-qapi-visit.o $(qapi-dir)/test-qapi-types.o 
$(qapi-dir)/test-qmp-marshal.o module.o
 
-QGALIB=qga/guest-agent-command-state.o
+QGALIB=qga/guest-agent-command-state.o qga/guest-agent-commands.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
+qemu-ga.o: $(addprefix $(qapi-dir)/, qga-qapi-types.c qga-qapi-types.h 
qga-qapi-visit.c qga-qmp-marshal.c) $(qapi-obj-y)
+qemu-ga$(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 $(qapi-dir)/qga-qapi-visit.o $(qapi-dir)/qga-qapi-types.o 
$(qapi-dir)/qga-qmp-marshal.o
 
 QEMULIBS=libhw32 libhw64 libuser libdis libdis-user
 
diff --git a/qapi-schema-guest.json b/qapi-schema-guest.json
new file mode 100644
index 0000000..fde5971
--- /dev/null
+++ b/qapi-schema-guest.json
@@ -0,0 +1,217 @@
+# *-*- Mode: Python -*-*
+
+##
+# @guest-sync:
+#
+# Echo back a unique integer value
+#
+# This is used by clients talking to the guest agent over the
+# wire to ensure the stream is in sync and doesn't contain stale
+# data from previous client. All guest agent responses should be
+# ignored until the provided unique integer value is returned,
+# and it is up to the client to handle stale whole or
+# partially-delivered JSON text in such a way that this response
+# can be obtained.
+#
+# Such clients should also preceed this command
+# with a 0xFF byte to make such the guest agent flushes any
+# partially read JSON data from a previous session.
+#
+# @id: randomly generated 64-bit integer
+#
+# Returns: The unique integer id passed in by the client
+#
+# Since: 0.15.0
+##
+{ 'command': 'guest-sync'
+  'data':    { 'id': 'int' },
+  'returns': 'int' }
+
+##
+# @guest-ping:
+#
+# Ping the guest agent, a non-error return implies success
+#
+# Since: 0.15.0
+##
+{ 'command': 'guest-ping' }
+
+##
+# @guest-info:
+#
+# Get some information about the guest agent.
+#
+# Since: 0.15.0
+##
+{ 'type': 'GuestAgentInfo', 'data': {'version': 'str'} }
+{ 'command': 'guest-info',
+  'returns': 'GuestAgentInfo' }
+
+##
+# @guest-shutdown:
+#
+# Initiate guest-activated shutdown. Note: this is an asynchronous
+# shutdown request, with no guaruntee of successful shutdown. Errors
+# will be logged to guest's syslog.
+#
+# @mode: #optional "halt", "powerdown" (default), or "reboot"
+#
+# Returns: Nothing on success
+#
+# Since: 0.15.0
+##
+{ 'command': 'guest-shutdown', 'data': { '*mode': 'str' } }
+
+##
+# @guest-file-open:
+#
+# Open a file in the guest and retrieve a file handle for it
+#
+# @filepath: Full path to the file in the guest to open.
+#
+# @mode: #optional open mode, as per fopen(), "r" is the default.
+#
+# Returns: Guest file handle on success.
+#
+# Since: 0.15.0
+##
+{ 'command': 'guest-file-open',
+  'data':    { 'path': 'str', '*mode': 'str' },
+  'returns': 'int' }
+
+##
+# @guest-file-close:
+#
+# Close an open file in the guest
+#
+# @handle: filehandle returned by guest-file-open
+#
+# Returns: Nothing on success.
+#
+# Since: 0.15.0
+##
+{ 'command': 'guest-file-close',
+  'data': { 'handle': 'int' } }
+
+##
+# @guest-file-read:
+#
+# Read from an open file in the guest. Data will be base64-encoded
+#
+# @handle: filehandle returned by guest-file-open
+#
+# @count: #optional maximum number of bytes to read (default is 4KB)
+#
+# Returns: GuestFileRead on success. Note: count is number of bytes read
+#          *before* base64 encoding bytes read.
+#
+# Since: 0.15.0
+##
+{ 'type': 'GuestFileRead',
+  'data': { 'count': 'int', 'buf-b64': 'str', 'eof': 'bool' } }
+
+{ 'command': 'guest-file-read',
+  'data':    { 'handle': 'int', '*count': 'int' },
+  'returns': 'GuestFileRead' }
+
+##
+# @guest-file-write:
+#
+# Write to an open file in the guest.
+#
+# @handle: filehandle returned by guest-file-open
+#
+# @buf-b64: base64-encoded string representing data to be written
+#
+# @count: #optional bytes to write (actual bytes, after base64-decode),
+#         default is all content in buf-b64 buffer after base64 decoding
+#
+# Returns: GuestFileWrite on success. Note: count is the number of bytes
+#          base64-decoded bytes written
+#
+# Since: 0.15.0
+##
+{ 'type': 'GuestFileWrite',
+  'data': { 'count': 'int', 'eof': 'bool' } }
+{ 'command': 'guest-file-write',
+  'data':    { 'handle': 'int', 'buf-b64': 'str', '*count': 'int' },
+  'returns': 'GuestFileWrite' }
+
+##
+# @guest-file-seek:
+#
+# Seek to a position in the file, as with fseek(), and return the
+# current file position afterward. Also encapsulates ftell()'s
+# functionality, just Set offset=0, whence=SEEK_CUR.
+#
+# @handle: filehandle returned by guest-file-open
+#
+# @offset: bytes to skip over in the file stream
+#
+# @whence: SEEK_SET, SEEK_CUR, or SEEK_END, as with fseek()
+#
+# Returns: GuestFileSeek on success.
+#
+# Since: 0.15.0
+##
+{ 'type': 'GuestFileSeek',
+  'data': { 'position': 'int', 'eof': 'bool' } }
+
+{ 'command': 'guest-file-seek',
+  'data':    { 'handle': 'int', 'offset': 'int', 'whence': 'int' },
+  'returns': 'GuestFileSeek' }
+
+##
+# @guest-file-flush:
+#
+# Write file changes bufferred in userspace to disk/kernel buffers
+#
+# @handle: filehandle returned by guest-file-open
+#
+# Returns: Nothing on success.
+#
+# Since: 0.15.0
+##
+{ 'command': 'guest-file-flush',
+  'data': { 'handle': 'int' } }
+
+##
+# @guest-fsfreeze-status:
+#
+# Get guest fsfreeze state. error state indicates failure to thaw 1 or more
+# previously frozen filesystems, or failure to open a previously cached
+# filesytem (filesystem unmounted/directory changes, etc).
+#
+# Returns: GuestFsfreezeStatus ("thawed", "frozen", etc., as defined below)
+#
+# Since: 0.15.0
+##
+{ 'enum': 'GuestFsfreezeStatus',
+  'data': [ 'thawed', 'frozen', 'error' ] }
+{ 'command': 'guest-fsfreeze-status',
+  'returns': 'GuestFsfreezeStatus' }
+
+##
+# @guest-fsfreeze-freeze:
+#
+# Sync and freeze all non-network guest filesystems
+#
+# Returns: Number of file systems frozen on success
+#
+# Since: 0.15.0
+##
+{ 'command': 'guest-fsfreeze-freeze',
+  'returns': 'int' }
+
+##
+# @guest-fsfreeze-thaw:
+#
+# Unfreeze frozen guest fileystems
+#
+# Returns: Number of file systems thawed
+#          If error, -1 (unknown error) or -errno
+#
+# Since: 0.15.0
+##
+{ 'command': 'guest-fsfreeze-thaw',
+  'returns': 'int' }
diff --git a/qemu-ga.c b/qemu-ga.c
index 1f3585c..6e2f61f 100644
--- a/qemu-ga.c
+++ b/qemu-ga.c
@@ -636,6 +636,9 @@ int main(int argc, char **argv)
     g_log_set_default_handler(ga_log, s);
     g_log_set_fatal_mask(NULL, G_LOG_LEVEL_ERROR);
     s->logging_enabled = true;
+    s->command_state = ga_command_state_new();
+    ga_command_state_init(s, s->command_state);
+    ga_command_state_init_all(s->command_state);
     ga_state = s;
 
     module_call_init(MODULE_INIT_QAPI);
@@ -644,6 +647,7 @@ int main(int argc, char **argv)
 
     g_main_loop_run(ga_state->main_loop);
 
+    ga_command_state_cleanup_all(ga_state->command_state);
     unlink(pidfile);
 
     return 0;
diff --git a/qerror.c b/qerror.c
index c92adfc..229d0d6 100644
--- a/qerror.c
+++ b/qerror.c
@@ -218,6 +218,14 @@ static const QErrorStringTable qerror_table[] = {
         .error_fmt = QERR_VNC_SERVER_FAILED,
         .desc      = "Could not start VNC server on %(target)",
     },
+    {
+        .error_fmt = QERR_QGA_LOGGING_FAILED,
+        .desc      = "Guest agent failed to log non-optional log statement",
+    },
+    {
+        .error_fmt = QERR_QGA_COMMAND_FAILED,
+        .desc      = "Guest agent command failed, error was '%(message)'",
+    },
     {}
 };
 
diff --git a/qerror.h b/qerror.h
index 9a9fa5b..7ec0fc1 100644
--- a/qerror.h
+++ b/qerror.h
@@ -184,4 +184,10 @@ QError *qobject_to_qerror(const QObject *obj);
 #define QERR_FEATURE_DISABLED \
     "{ 'class': 'FeatureDisabled', 'data': { 'name': %s } }"
 
+#define QERR_QGA_LOGGING_FAILED \
+    "{ 'class': 'QgaLoggingFailed', 'data': {} }"
+
+#define QERR_QGA_COMMAND_FAILED \
+    "{ 'class': 'QgaCommandFailed', 'data': { 'message': %s } }"
+
 #endif /* QERROR_H */
diff --git a/qga/guest-agent-commands.c b/qga/guest-agent-commands.c
new file mode 100644
index 0000000..8c0d67e
--- /dev/null
+++ b/qga/guest-agent-commands.c
@@ -0,0 +1,518 @@
+/*
+ * QEMU Guest Agent commands
+ *
+ * Copyright IBM Corp. 2011
+ *
+ * Authors:
+ *  Michael Roth      <address@hidden>
+ *
+ * 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 <glib.h>
+#include <mntent.h>
+#include <sys/types.h>
+#include <sys/ioctl.h>
+#include <linux/fs.h>
+#include "qga/guest-agent-core.h"
+#include "qga-qmp-commands.h"
+#include "qerror.h"
+#include "qemu-queue.h"
+
+static GAState *ga_state;
+
+static void disable_logging(void)
+{
+    ga_disable_logging(ga_state);
+}
+
+static void enable_logging(void)
+{
+    ga_enable_logging(ga_state);
+}
+
+/* Note: in some situations, like with the fsfreeze, logging may be
+ * temporarilly disabled. if it is necessary that a command be able
+ * to log for accounting purposes, check ga_logging_enabled() beforehand,
+ * and use the QERR_QGA_LOGGING_DISABLED to generate an error
+ */
+static void slog(const char *fmt, ...)
+{
+    va_list ap;
+
+    va_start(ap, fmt);
+    g_logv("syslog", G_LOG_LEVEL_INFO, fmt, ap);
+    va_end(ap);
+}
+
+int64_t qmp_guest_sync(int64_t id, Error **errp)
+{
+    return id;
+}
+
+void qmp_guest_ping(Error **err)
+{
+    slog("guest-ping called");
+}
+
+struct GuestAgentInfo *qmp_guest_info(Error **err)
+{
+    GuestAgentInfo *info = qemu_mallocz(sizeof(GuestAgentInfo));
+
+    info->version = g_strdup(QGA_VERSION);
+
+    return info;
+}
+
+void qmp_guest_shutdown(bool has_mode, const char *mode, Error **err)
+{
+    int ret;
+    const char *shutdown_flag;
+
+    slog("guest-shutdown called, mode: %s", mode);
+    if (!has_mode || strcmp(mode, "powerdown") == 0) {
+        shutdown_flag = "-P";
+    } else if (strcmp(mode, "halt") == 0) {
+        shutdown_flag = "-H";
+    } else if (strcmp(mode, "reboot") == 0) {
+        shutdown_flag = "-r";
+    } else {
+        error_set(err, QERR_INVALID_PARAMETER_VALUE, "mode",
+                  "halt|powerdown|reboot");
+        return;
+    }
+
+    ret = fork();
+    if (ret == 0) {
+        /* child, start the shutdown */
+        setsid();
+        fclose(stdin);
+        fclose(stdout);
+        fclose(stderr);
+
+        ret = execl("/sbin/shutdown", "shutdown", shutdown_flag, "+0",
+                    "hypervisor initiated shutdown", (char*)NULL);
+        if (ret) {
+            slog("guest-shutdown failed: %s", strerror(errno));
+        }
+        exit(!!ret);
+    } else if (ret < 0) {
+        error_set(err, QERR_UNDEFINED_ERROR);
+    }
+}
+
+typedef struct GuestFileHandle {
+    uint64_t id;
+    FILE *fh;
+    QTAILQ_ENTRY(GuestFileHandle) next;
+} GuestFileHandle;
+
+static struct {
+    QTAILQ_HEAD(, GuestFileHandle) filehandles;
+} guest_file_state;
+
+static void guest_file_handle_add(FILE *fh)
+{
+    GuestFileHandle *gfh;
+
+    gfh = qemu_mallocz(sizeof(GuestFileHandle));
+    gfh->id = fileno(fh);
+    gfh->fh = fh;
+    QTAILQ_INSERT_TAIL(&guest_file_state.filehandles, gfh, next);
+}
+
+static GuestFileHandle *guest_file_handle_find(int64_t id)
+{
+    GuestFileHandle *gfh;
+
+    QTAILQ_FOREACH(gfh, &guest_file_state.filehandles, next)
+    {
+        if (gfh->id == id) {
+            return gfh;
+        }
+    }
+
+    return NULL;
+}
+
+int64_t qmp_guest_file_open(const char *path, bool has_mode, const char *mode, 
Error **err)
+{
+    FILE *fh;
+    int fd;
+    int64_t ret = -1;
+
+    if (!has_mode) {
+        mode = "r";
+    }
+    slog("guest-file-open called, filepath: %s, mode: %s", path, mode);
+    fh = fopen(path, mode);
+    if (!fh) {
+        error_set(err, QERR_OPEN_FILE_FAILED, path);
+        return -1;
+    }
+
+    /* set fd non-blocking to avoid common use cases (like reading from a
+     * named pipe) from hanging the agent
+     */
+    fd = fileno(fh);
+    ret = fcntl(fd, F_GETFL);
+    ret = fcntl(fd, F_SETFL, ret | O_NONBLOCK);
+    if (ret == -1) {
+        error_set(err, QERR_QGA_COMMAND_FAILED, "fcntl() failed");
+        fclose(fh);
+        return -1;
+    }
+
+    guest_file_handle_add(fh);
+    slog("guest-file-open, handle: %d", fd);
+    return fd;
+}
+
+void qmp_guest_file_close(int64_t handle, Error **err)
+{
+    GuestFileHandle *gfh = guest_file_handle_find(handle);
+    int ret;
+
+    slog("guest-file-close called, handle: %ld", handle);
+    if (!gfh) {
+        error_set(err, QERR_FD_NOT_FOUND, "handle");
+        return;
+    }
+
+    ret = fclose(gfh->fh);
+    if (ret == -1) {
+        error_set(err, QERR_QGA_COMMAND_FAILED, "fclose() failed");
+        return;
+    }
+
+    QTAILQ_REMOVE(&guest_file_state.filehandles, gfh, next);
+    qemu_free(gfh);
+}
+
+struct GuestFileRead *qmp_guest_file_read(int64_t handle, bool has_count,
+                                          int64_t count, Error **err)
+{
+    GuestFileHandle *gfh = guest_file_handle_find(handle);
+    GuestFileRead *read_data = NULL;
+    guchar *buf;
+    FILE *fh;
+    size_t read_count;
+
+    if (!gfh) {
+        error_set(err, QERR_FD_NOT_FOUND, "handle");
+        return NULL;
+    }
+
+    if (!has_count) {
+        count = QGA_READ_COUNT_DEFAULT;
+    } else if (count < 0) {
+        error_set(err, QERR_INVALID_PARAMETER, "count");
+        return NULL;
+    }
+
+    fh = gfh->fh;
+    buf = qemu_mallocz(count+1);
+    read_count = fread(buf, 1, count, fh);
+    if (ferror(fh)) {
+        slog("guest-file-read failed, handle: %ld", handle);
+        error_set(err, QERR_QGA_COMMAND_FAILED, "fread() failed");
+    } else {
+        buf[read_count] = 0;
+        read_data = qemu_mallocz(sizeof(GuestFileRead));
+        read_data->count = read_count;
+        read_data->eof = feof(fh);
+        if (read_count) {
+            read_data->buf_b64 = g_base64_encode(buf, read_count);
+        }
+    }
+    qemu_free(buf);
+    clearerr(fh);
+
+    return read_data;
+}
+
+GuestFileWrite *qmp_guest_file_write(int64_t handle, const char *buf_b64,
+                                     bool has_count, int64_t count, Error 
**err)
+{
+    GuestFileWrite *write_data = NULL;
+    guchar *buf;
+    gsize buf_len;
+    int write_count;
+    GuestFileHandle *gfh = guest_file_handle_find(handle);
+    FILE *fh;
+
+    if (!gfh) {
+        error_set(err, QERR_FD_NOT_FOUND, "handle");
+        return NULL;
+    }
+
+    fh = gfh->fh;
+    buf = g_base64_decode(buf_b64, &buf_len);
+
+    if (!has_count) {
+        count = buf_len;
+    } else if (count < 0 || count > buf_len) {
+        qemu_free(buf);
+        error_set(err, QERR_INVALID_PARAMETER, "count");
+        return NULL;
+    }
+
+    write_count = fwrite(buf, 1, count, fh);
+    if (ferror(fh)) {
+        slog("guest-file-write failed, handle: %ld", handle);
+        error_set(err, QERR_QGA_COMMAND_FAILED, "fwrite() error");
+    } else {
+        write_data = qemu_mallocz(sizeof(GuestFileWrite));
+        write_data->count = write_count;
+        write_data->eof = feof(fh);
+    }
+    qemu_free(buf);
+    clearerr(fh);
+
+    return write_data;
+}
+
+struct GuestFileSeek *qmp_guest_file_seek(int64_t handle, int64_t offset,
+                                          int64_t whence, Error **err)
+{
+    GuestFileHandle *gfh = guest_file_handle_find(handle);
+    GuestFileSeek *seek_data = NULL;
+    FILE *fh;
+    int ret;
+
+    if (!gfh) {
+        error_set(err, QERR_FD_NOT_FOUND, "handle");
+        return NULL;
+    }
+
+    fh = gfh->fh;
+    ret = fseek(fh, offset, whence);
+    if (ret == -1) {
+        error_set(err, QERR_QGA_COMMAND_FAILED, strerror(errno));
+    } else {
+        seek_data = qemu_mallocz(sizeof(GuestFileRead));
+        seek_data->position = ftell(fh);
+        seek_data->eof = feof(fh);
+    }
+    clearerr(fh);
+
+    return seek_data;
+}
+
+void qmp_guest_file_flush(int64_t handle, Error **err)
+{
+    GuestFileHandle *gfh = guest_file_handle_find(handle);
+    FILE *fh;
+    int ret;
+
+    if (!gfh) {
+        error_set(err, QERR_FD_NOT_FOUND, "handle");
+        return;
+    }
+
+    fh = gfh->fh;
+    ret = fflush(fh);
+    if (ret == EOF) {
+        error_set(err, QERR_QGA_COMMAND_FAILED, strerror(errno));
+    }
+}
+
+static void guest_file_init(void)
+{
+    QTAILQ_INIT(&guest_file_state.filehandles);
+}
+
+typedef struct GuestFsfreezeMount {
+    char *dirname;
+    char *devtype;
+    QTAILQ_ENTRY(GuestFsfreezeMount) next;
+} GuestFsfreezeMount;
+
+struct {
+    GuestFsfreezeStatus status;
+    QTAILQ_HEAD(, GuestFsfreezeMount) mount_list;
+} guest_fsfreeze_state;
+
+/*
+ * Walk the mount table and build a list of local file systems
+ */
+static int guest_fsfreeze_build_mount_list(void)
+{
+    struct mntent *ment;
+    GuestFsfreezeMount *mount, *temp;
+    char const *mtab = MOUNTED;
+    FILE *fp;
+
+    QTAILQ_FOREACH_SAFE(mount, &guest_fsfreeze_state.mount_list, next, temp) {
+        QTAILQ_REMOVE(&guest_fsfreeze_state.mount_list, mount, next);
+        qemu_free(mount->dirname);
+        qemu_free(mount->devtype);
+        qemu_free(mount);
+    }
+
+    fp = setmntent(mtab, "r");
+    if (!fp) {
+        g_warning("fsfreeze: unable to read mtab");
+        return -1;
+    }
+
+    while ((ment = getmntent(fp))) {
+        /*
+         * An entry which device name doesn't start with a '/' is
+         * either a dummy file system or a network file system.
+         * Add special handling for smbfs and cifs as is done by
+         * coreutils as well.
+         */
+        if ((ment->mnt_fsname[0] != '/') ||
+            (strcmp(ment->mnt_type, "smbfs") == 0) ||
+            (strcmp(ment->mnt_type, "cifs") == 0)) {
+            continue;
+        }
+
+        mount = qemu_mallocz(sizeof(GuestFsfreezeMount));
+        mount->dirname = qemu_strdup(ment->mnt_dir);
+        mount->devtype = qemu_strdup(ment->mnt_type);
+
+        QTAILQ_INSERT_TAIL(&guest_fsfreeze_state.mount_list, mount, next);
+    }
+
+    endmntent(fp);
+
+    return 0;
+}
+
+/*
+ * Return status of freeze/thaw
+ */
+GuestFsfreezeStatus qmp_guest_fsfreeze_status(Error **err)
+{
+    return guest_fsfreeze_state.status;
+}
+
+/*
+ * Walk list of mounted file systems in the guest, and freeze the ones which
+ * are real local file systems.
+ */
+int64_t qmp_guest_fsfreeze_freeze(Error **err)
+{
+    int ret = 0, i = 0;
+    struct GuestFsfreezeMount *mount, *temp;
+    int fd;
+    char err_msg[512];
+
+    slog("guest-fsfreeze called");
+
+    if (guest_fsfreeze_state.status == GUEST_FSFREEZE_STATUS_FROZEN) {
+        return 0;
+    }
+
+    ret = guest_fsfreeze_build_mount_list();
+    if (ret < 0) {
+        return ret;
+    }
+
+    /* cannot risk guest agent blocking itself on a write in this state */
+    disable_logging();
+
+    QTAILQ_FOREACH_SAFE(mount, &guest_fsfreeze_state.mount_list, next, temp) {
+        fd = qemu_open(mount->dirname, O_RDONLY);
+        if (fd == -1) {
+            sprintf(err_msg, "failed to open %s, %s", mount->dirname, 
strerror(errno));
+            error_set(err, QERR_QGA_COMMAND_FAILED, err_msg);
+            goto error;
+        }
+
+        /* we try to cull filesytems we know won't work in advance, but other
+         * filesytems may not implement fsfreeze for less obvious reasons.
+         * these will report EOPNOTSUPP, so we simply ignore them. when
+         * thawing, these filesystems will return an EINVAL instead, due to
+         * not being in a frozen state. Other filesystem-specific
+         * errors may result in EINVAL, however, so the user should check the
+         * number * of filesystems returned here against those returned by the
+         * thaw operation to determine whether everything completed
+         * successfully
+         */
+        ret = ioctl(fd, FIFREEZE);
+        if (ret < 0 && errno != EOPNOTSUPP) {
+            sprintf(err_msg, "failed to freeze %s, %s", mount->dirname, 
strerror(errno));
+            error_set(err, QERR_QGA_COMMAND_FAILED, err_msg);
+            close(fd);
+            goto error;
+        }
+        close(fd);
+
+        i++;
+    }
+
+    guest_fsfreeze_state.status = GUEST_FSFREEZE_STATUS_FROZEN;
+    return i;
+
+error:
+    if (i > 0) {
+        qmp_guest_fsfreeze_thaw(NULL);
+    }
+    return 0;
+}
+
+/*
+ * Walk list of frozen file systems in the guest, and thaw them.
+ */
+int64_t qmp_guest_fsfreeze_thaw(Error **err)
+{
+    int ret;
+    GuestFsfreezeMount *mount, *temp;
+    int fd, i = 0;
+    bool has_error = false;
+
+    QTAILQ_FOREACH_SAFE(mount, &guest_fsfreeze_state.mount_list, next, temp) {
+        fd = qemu_open(mount->dirname, O_RDONLY);
+        if (fd == -1) {
+            has_error = true;
+            continue;
+        }
+        ret = ioctl(fd, FITHAW);
+        if (ret < 0 && errno != EOPNOTSUPP && errno != EINVAL) {
+            has_error = true;
+            close(fd);
+            continue;
+        }
+        close(fd);
+        i++;
+    }
+
+    if (has_error) {
+        guest_fsfreeze_state.status = GUEST_FSFREEZE_STATUS_ERROR;
+    } else {
+        guest_fsfreeze_state.status = GUEST_FSFREEZE_STATUS_THAWED;
+    }
+    enable_logging();
+    return i;
+}
+
+static void guest_fsfreeze_init(void)
+{
+    guest_fsfreeze_state.status = GUEST_FSFREEZE_STATUS_THAWED;
+    QTAILQ_INIT(&guest_fsfreeze_state.mount_list);
+}
+
+static void guest_fsfreeze_cleanup(void)
+{
+    int64_t ret;
+    Error *err = NULL;
+
+    if (guest_fsfreeze_state.status == GUEST_FSFREEZE_STATUS_FROZEN) {
+        ret = qmp_guest_fsfreeze_thaw(&err);
+        if (ret < 0 || err) {
+            slog("failed to clean up frozen filesystems");
+        }
+    }
+}
+
+/* register init/cleanup routines for stateful command groups */
+void ga_command_state_init(GAState *s, GACommandState *cs)
+{
+    ga_state = s;
+    ga_command_state_add(cs, guest_fsfreeze_init, guest_fsfreeze_cleanup);
+    ga_command_state_add(cs, guest_file_init, NULL);
+}
diff --git a/qga/guest-agent-core.h b/qga/guest-agent-core.h
index 66d1729..e42b91d 100644
--- a/qga/guest-agent-core.h
+++ b/qga/guest-agent-core.h
@@ -14,10 +14,12 @@
 #include "qemu-common.h"
 
 #define QGA_VERSION "1.0"
+#define QGA_READ_COUNT_DEFAULT 4 << 10
 
 typedef struct GAState GAState;
 typedef struct GACommandState GACommandState;
 
+void ga_command_state_init(GAState *s, GACommandState *cs);
 void ga_command_state_add(GACommandState *cs,
                           void (*init)(void),
                           void (*cleanup)(void));
-- 
1.7.6.233.gd79bc