[Qemu-devel] [PATCH v5 3/5] guest agent: add guest agent RPCs/commands

[Michael Roth]

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-close
guest-fsfreeze-freeze
guest-fsfreeze-thaw
guest-fsfreeze-status

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

Signed-off-by: Michael Roth <address@hidden>
---
 qerror.c                   |    4 +
 qerror.h                   |    3 +
 qga/guest-agent-commands.c |  522 ++++++++++++++++++++++++++++++++++++++++++++
 qga/guest-agent-core.h     |    1 +
 4 files changed, 530 insertions(+), 0 deletions(-)
 create mode 100644 qga/guest-agent-commands.c

diff --git a/qerror.c b/qerror.c
index d7fcd93..24f0c48 100644
--- a/qerror.c
+++ b/qerror.c
@@ -213,6 +213,10 @@ 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      = "failed to write log statement due to logging being 
disabled",
+    },
     {}
 };
 
diff --git a/qerror.h b/qerror.h
index 7a89a50..bf3d5a9 100644
--- a/qerror.h
+++ b/qerror.h
@@ -184,4 +184,7 @@ QError *qobject_to_qerror(const QObject *obj);
 #define QERR_FEATURE_DISABLED \
     "{ 'class': 'FeatureDisabled', 'data': { 'name': %s } }"
 
+#define QERR_QGA_LOGGING_FAILED \
+    "{ 'class': 'QgaLoggingFailed', 'data': {} }"
+
 #endif /* QERROR_H */
diff --git a/qga/guest-agent-commands.c b/qga/guest-agent-commands.c
new file mode 100644
index 0000000..6f9886a
--- /dev/null
+++ b/qga/guest-agent-commands.c
@@ -0,0 +1,522 @@
+/*
+ * 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"
+
+static GAState *ga_state;
+
+static bool logging_enabled(void)
+{
+    return ga_logging_enabled(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 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 = g_malloc0(sizeof(GuestAgentInfo));
+
+    info->version = g_strdup(QGA_VERSION);
+
+    return info;
+}
+
+void qmp_guest_shutdown(const char *shutdown_mode, Error **err)
+{
+    int ret;
+    const char *shutdown_flag;
+
+    if (!logging_enabled()) {
+        error_set(err, QERR_QGA_LOGGING_FAILED);
+        return;
+    }
+
+    slog("guest-shutdown called, shutdown_mode: %s", shutdown_mode);
+    if (strcmp(shutdown_mode, "halt") == 0) {
+        shutdown_flag = "-H";
+    } else if (strcmp(shutdown_mode, "powerdown") == 0) {
+        shutdown_flag = "-P";
+    } else if (strcmp(shutdown_mode, "reboot") == 0) {
+        shutdown_flag = "-r";
+    } else {
+        error_set(err, QERR_INVALID_PARAMETER_VALUE, "shutdown_mode",
+                  "halt|powerdown|reboot");
+        return;
+    }
+
+    ret = fork();
+    if (ret == 0) {
+        /* child, start the shutdown */
+        setsid();
+        fclose(stdin);
+        fclose(stdout);
+        fclose(stderr);
+
+        sleep(5);
+        ret = execl("/sbin/shutdown", "shutdown", shutdown_flag, "+0",
+                    "hypervisor initiated shutdown", (char*)NULL);
+        exit(!!ret);
+    } else if (ret < 0) {
+        error_set(err, QERR_UNDEFINED_ERROR);
+    }
+}
+
+typedef struct GuestFileHandle {
+    uint64_t id;
+    FILE *fh;
+} GuestFileHandle;
+
+static struct {
+    GSList *filehandles;
+    uint64_t last_id;
+} guest_file_state;
+
+static int64_t guest_file_handle_add(FILE *fh)
+{
+    GuestFileHandle *gfh;
+
+    gfh = g_malloc(sizeof(GuestFileHandle));
+    gfh->id = guest_file_state.last_id++;
+    gfh->fh = fh;
+    guest_file_state.filehandles = g_slist_append(guest_file_state.filehandles,
+                                                  gfh);
+    return gfh->id;
+}
+
+static gint guest_file_handle_match(gconstpointer elem, gconstpointer id_p)
+{
+    const uint64_t *id = id_p;
+    const GuestFileHandle *gfh = elem;
+
+    g_assert(gfh);
+    return (gfh->id != *id);
+}
+
+static FILE *guest_file_handle_find(int64_t id)
+{
+    GSList *elem = g_slist_find_custom(guest_file_state.filehandles, &id,
+                                       guest_file_handle_match);
+    GuestFileHandle *gfh;
+
+    if (elem) {
+        g_assert(elem->data);
+        gfh = elem->data;
+        return gfh->fh;
+    }
+
+    return NULL;
+}
+
+static void guest_file_handle_remove(int64_t id)
+{
+    GSList *elem = g_slist_find_custom(guest_file_state.filehandles, &id,
+                                       guest_file_handle_match);
+    gpointer data = elem->data;
+
+    if (!data) {
+        return;
+    }
+    guest_file_state.filehandles = g_slist_remove(guest_file_state.filehandles,
+                                                  data);
+    g_free(data);
+}
+
+int64_t qmp_guest_file_open(const char *filepath, const char *mode, Error 
**err)
+{
+    FILE *fh;
+    int fd, ret;
+    int64_t id = -1;
+
+    if (!logging_enabled()) {
+        error_set(err, QERR_QGA_LOGGING_FAILED);
+        goto out;
+    }
+    slog("guest-file-open called, filepath: %s, mode: %s", filepath, mode);
+    fh = fopen(filepath, mode);
+    if (!fh) {
+        error_set(err, QERR_OPEN_FILE_FAILED, filepath);
+        goto out;
+    }
+
+    /* 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_OPEN_FILE_FAILED, filepath);
+        fclose(fh);
+        goto out;
+    }
+
+    id = guest_file_handle_add(fh);
+    slog("guest-file-open, filehandle: %ld", id);
+out:
+    return id;
+}
+
+struct GuestFileRead *qmp_guest_file_read(int64_t filehandle, int64_t count,
+                                          Error **err)
+{
+    GuestFileRead *read_data;
+    guchar *buf;
+    FILE *fh = guest_file_handle_find(filehandle);
+    size_t read_count;
+
+    if (!fh) {
+        error_set(err, QERR_FD_NOT_FOUND, "filehandle");
+        return NULL;
+    }
+
+    read_data = g_malloc0(sizeof(GuestFileRead));
+    buf = g_malloc(count);
+
+    read_count = fread(buf, 1, count, fh);
+    buf[read_count] = 0;
+    read_data->count = read_count;
+    read_data->eof = feof(fh);
+    if (read_count) {
+        read_data->buf = g_base64_encode(buf, read_count);
+    }
+    g_free(buf);
+    /* clear error and eof. error is generally due to EAGAIN from non-blocking
+     * mode, and no real way to differenitate from a real error since we only
+     * get boolean error flag from ferror()
+     */
+    clearerr(fh);
+
+    return read_data;
+}
+
+GuestFileWrite *qmp_guest_file_write(int64_t filehandle, const char *data_b64,
+                                     int64_t count, Error **err)
+{
+    GuestFileWrite *write_data;
+    guchar *data;
+    gsize data_len;
+    int write_count;
+    FILE *fh = guest_file_handle_find(filehandle);
+
+    if (!fh) {
+        error_set(err, QERR_FD_NOT_FOUND, "filehandle");
+        return NULL;
+    }
+
+    write_data = g_malloc0(sizeof(GuestFileWrite));
+    data = g_base64_decode(data_b64, &data_len);
+    write_count = fwrite(data, 1, MIN(count, data_len), fh);
+    write_data->count = write_count;
+    write_data->eof = feof(fh);
+    g_free(data);
+    clearerr(fh);
+
+    return write_data;
+}
+
+struct GuestFileSeek *qmp_guest_file_seek(int64_t filehandle, int64_t offset,
+                                          int64_t whence, Error **err)
+{
+    GuestFileSeek *seek_data;
+    FILE *fh = guest_file_handle_find(filehandle);
+    int ret;
+
+    if (!fh) {
+        error_set(err, QERR_FD_NOT_FOUND, "filehandle");
+        return NULL;
+    }
+
+    seek_data = g_malloc0(sizeof(GuestFileRead));
+    ret = fseek(fh, offset, whence);
+    if (ret == -1) {
+        error_set(err, QERR_UNDEFINED_ERROR);
+        g_free(seek_data);
+        return NULL;
+    }
+    seek_data->position = ftell(fh);
+    seek_data->eof = feof(fh);
+    clearerr(fh);
+
+    return seek_data;
+}
+
+void qmp_guest_file_close(int64_t filehandle, Error **err)
+{
+    FILE *fh = guest_file_handle_find(filehandle);
+
+    if (!logging_enabled()) {
+        error_set(err, QERR_QGA_LOGGING_FAILED);
+        return;
+    }
+    slog("guest-file-close called, filehandle: %ld", filehandle);
+    if (!fh) {
+        error_set(err, QERR_FD_NOT_FOUND, "filehandle");
+        return;
+    }
+
+    fclose(fh);
+    guest_file_handle_remove(filehandle);
+}
+
+/*
+ * Walk the mount table and build a list of local file systems
+ */
+
+struct direntry {
+    char *dirname;
+    char *devtype;
+    struct direntry *next;
+};
+
+struct {
+    struct direntry *mount_list;
+    GuestFsfreezeStatus status;
+} guest_fsfreeze_state;
+
+static int guest_fsfreeze_build_mount_list(void)
+{
+    struct mntent *mnt;
+    struct direntry *entry;
+    struct direntry *next;
+    char const *mtab = MOUNTED;
+    FILE *fp;
+
+    fp = setmntent(mtab, "r");
+    if (!fp) {
+        g_warning("fsfreeze: unable to read mtab");
+        goto fail;
+    }
+
+    while ((mnt = 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 ((mnt->mnt_fsname[0] != '/') ||
+            (strcmp(mnt->mnt_type, "smbfs") == 0) ||
+            (strcmp(mnt->mnt_type, "cifs") == 0)) {
+            continue;
+        }
+
+        entry = g_malloc(sizeof(struct direntry));
+        entry->dirname = qemu_strdup(mnt->mnt_dir);
+        entry->devtype = qemu_strdup(mnt->mnt_type);
+        entry->next = guest_fsfreeze_state.mount_list;
+
+        guest_fsfreeze_state.mount_list = entry;
+    }
+
+    endmntent(fp);
+
+    return 0;
+
+fail:
+    while(guest_fsfreeze_state.mount_list) {
+        next = guest_fsfreeze_state.mount_list->next;
+        g_free(guest_fsfreeze_state.mount_list->dirname);
+        g_free(guest_fsfreeze_state.mount_list->devtype);
+        g_free(guest_fsfreeze_state.mount_list);
+        guest_fsfreeze_state.mount_list = next;
+    }
+
+    return -1;
+}
+
+/*
+ * 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 direntry *entry;
+    int fd;
+
+    if (!logging_enabled()) {
+        error_set(err, QERR_QGA_LOGGING_FAILED);
+        goto out;
+    }
+
+    slog("guest-fsfreeze called");
+
+    if (guest_fsfreeze_state.status != GUEST_FSFREEZE_STATUS_THAWED) {
+        ret = 0;
+        goto out;
+    }
+
+    ret = guest_fsfreeze_build_mount_list();
+    if (ret < 0) {
+        goto out;
+    }
+
+    guest_fsfreeze_state.status = GUEST_FSFREEZE_STATUS_INPROGRESS;
+
+    /* cannot risk guest agent blocking itself on a write in this state */
+    disable_logging();
+
+    entry = guest_fsfreeze_state.mount_list;
+    while(entry) {
+        fd = qemu_open(entry->dirname, O_RDONLY);
+        if (fd == -1) {
+            ret = errno;
+            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 reason 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) {
+            close(fd);
+            goto error;
+        }
+        close(fd);
+
+        entry = entry->next;
+        i++;
+    }
+
+    guest_fsfreeze_state.status = GUEST_FSFREEZE_STATUS_FROZEN;
+    ret = i;
+out:
+    return ret;
+error:
+    if (i > 0) {
+        guest_fsfreeze_state.status = GUEST_FSFREEZE_STATUS_ERROR;
+    }
+    goto out;
+}
+
+/*
+ * Walk list of frozen file systems in the guest, and thaw them.
+ */
+int64_t qmp_guest_fsfreeze_thaw(Error **err)
+{
+    int ret;
+    struct direntry *entry;
+    int fd, i = 0;
+
+    if (guest_fsfreeze_state.status != GUEST_FSFREEZE_STATUS_FROZEN &&
+        guest_fsfreeze_state.status != GUEST_FSFREEZE_STATUS_INPROGRESS) {
+        ret = 0;
+        goto out_enable_logging;
+    }
+
+    while((entry = guest_fsfreeze_state.mount_list)) {
+        fd = qemu_open(entry->dirname, O_RDONLY);
+        if (fd == -1) {
+            ret = -errno;
+            goto out;
+        }
+        ret = ioctl(fd, FITHAW);
+        if (ret < 0 && errno != EOPNOTSUPP && errno != EINVAL) {
+            ret = -errno;
+            close(fd);
+            goto out;
+        }
+        close(fd);
+
+        guest_fsfreeze_state.mount_list = entry->next;
+        g_free(entry->dirname);
+        g_free(entry->devtype);
+        g_free(entry);
+        i++;
+    }
+
+    guest_fsfreeze_state.status = GUEST_FSFREEZE_STATUS_THAWED;
+    ret = i;
+out_enable_logging:
+    enable_logging();
+out:
+    return ret;
+}
+
+static void guest_fsfreeze_init(void)
+{
+    guest_fsfreeze_state.status = GUEST_FSFREEZE_STATUS_THAWED;
+}
+
+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);
+}
diff --git a/qga/guest-agent-core.h b/qga/guest-agent-core.h
index 66d1729..a85a5e4 100644
--- a/qga/guest-agent-core.h
+++ b/qga/guest-agent-core.h
@@ -18,6 +18,7 @@
 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));
-- 
1.7.0.4