[Qemu-devel] [PATCH 5/5] qga: guest-exec simple stdin/stdout/stderr redirection

[Denis V. Lunev]

From: Yuri Pudgorodskiy <address@hidden>

Implemented with base64-encoded strings in qga json protocol.
Glib portable GIOChannel is used for data I/O.

Optinal stdin parameter of guest-exec command is now used as
stdin content for spawned subprocess.

If capture-output bool flag is specified, guest-exec redirects out/err
file descriptiors internally to pipes and collects subprocess
output.

Guest-exe-status is modified to return this collected data to requestor
in base64 encoding.

Signed-off-by: Yuri Pudgorodskiy <address@hidden>
Signed-off-by: Denis V. Lunev <address@hidden>
Signed-by: Michael Roth <address@hidden>
---
 qga/commands.c       | 188 ++++++++++++++++++++++++++++++++++++++++++++++++---
 qga/qapi-schema.json |   7 +-
 2 files changed, 186 insertions(+), 9 deletions(-)

diff --git a/qga/commands.c b/qga/commands.c
index b487324..2f88026 100644
--- a/qga/commands.c
+++ b/qga/commands.c
@@ -15,6 +15,11 @@
 #include "qga-qmp-commands.h"
 #include "qapi/qmp/qerror.h"
 
+/* Maximum captured guest-exec out_data/err_data - 16MB */
+#define GUEST_EXEC_MAX_OUTPUT (16*1024*1024)
+/* Allocation and I/O buffer for reading guest-exec out_data/err_data - 4KB */
+#define GUEST_EXEC_IO_SIZE (4*1024)
+
 /* 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,
@@ -71,10 +76,23 @@ struct GuestAgentInfo *qmp_guest_info(Error **errp)
     return info;
 }
 
+struct GuestExecIOData {
+    guchar *data;
+    gsize size;
+    gsize length;
+    gint closed;
+    bool truncated;
+    const char *name;
+};
+
 struct GuestExecInfo {
     GPid pid;
     gint status;
-    bool finished;
+    bool has_output;
+    gint finished;
+    struct GuestExecIOData in;
+    struct GuestExecIOData out;
+    struct GuestExecIOData err;
     QTAILQ_ENTRY(GuestExecInfo) next;
 };
 typedef struct GuestExecInfo GuestExecInfo;
@@ -123,9 +141,18 @@ GuestExecStatus *qmp_guest_exec_status(int64_t pid, Error 
**err)
     }
 
     ges = g_new0(GuestExecStatus, 1);
-    ges->exited = gei->finished;
 
-    if (gei->finished) {
+    bool finished = g_atomic_int_get(&gei->finished);
+
+    /* need to wait till output channels are closed
+     * to be sure we captured all output at this point */
+    if (gei->has_output) {
+        finished = finished && g_atomic_int_get(&gei->out.closed);
+        finished = finished && g_atomic_int_get(&gei->err.closed);
+    }
+
+    ges->exited = finished;
+    if (finished) {
         /* Glib has no portable way to parse exit status.
          * On UNIX, we can get either exit code from normal termination
          * or signal number.
@@ -160,6 +187,20 @@ GuestExecStatus *qmp_guest_exec_status(int64_t pid, Error 
**err)
             ges->signal = WTERMSIG(gei->status);
         }
 #endif
+        if (gei->out.length > 0) {
+            ges->has_out_data = true;
+            ges->out_data = g_base64_encode(gei->out.data, gei->out.length);
+            g_free(gei->out.data);
+            ges->has_out_truncated = gei->out.truncated;
+        }
+
+        if (gei->err.length > 0) {
+            ges->has_err_data = true;
+            ges->err_data = g_base64_encode(gei->err.data, gei->err.length);
+            g_free(gei->err.data);
+            ges->has_err_truncated = gei->err.truncated;
+        }
+
         QTAILQ_REMOVE(&guest_exec_state.processes, gei, next);
         g_free(gei);
     }
@@ -230,6 +271,98 @@ static void guest_exec_task_setup(gpointer data)
 #endif
 }
 
+static gboolean guest_exec_input_watch(GIOChannel *ch,
+        GIOCondition cond, gpointer p_)
+{
+    struct GuestExecIOData *p = (struct GuestExecIOData *)p_;
+    gsize bytes_written = 0;
+    GIOStatus status;
+    GError *gerr = NULL;
+
+    /* nothing left to write */
+    if (p->size == p->length) {
+        goto done;
+    }
+
+    status = g_io_channel_write_chars(ch, (gchar *)p->data + p->length,
+            p->size - p->length, &bytes_written, &gerr);
+
+    /* can be not 0 even if not G_IO_STATUS_NORMAL */
+    if (bytes_written != 0) {
+        p->length += bytes_written;
+    }
+
+    /* continue write, our callback will be called again */
+    if (status == G_IO_STATUS_NORMAL || status == G_IO_STATUS_AGAIN) {
+        return TRUE;
+    }
+
+    if (gerr) {
+        g_warning("qga: i/o error writing to inp_data channel: %s",
+                gerr->message);
+        g_error_free(gerr);
+    }
+
+done:
+    g_io_channel_shutdown(ch, true, NULL);
+    g_io_channel_unref(ch);
+    g_atomic_int_set(&p->closed, 1);
+    g_free(p->data);
+
+    return FALSE;
+}
+
+static gboolean guest_exec_output_watch(GIOChannel *ch,
+        GIOCondition cond, gpointer p_)
+{
+    struct GuestExecIOData *p = (struct GuestExecIOData *)p_;
+    gsize bytes_read;
+    GIOStatus gstatus;
+
+    if (cond == G_IO_HUP || cond == G_IO_ERR) {
+        goto close;
+    }
+
+    if (p->size == p->length) {
+        gpointer t = NULL;
+        if (!p->truncated && p->size < GUEST_EXEC_MAX_OUTPUT) {
+            t = g_try_realloc(p->data, p->size + GUEST_EXEC_IO_SIZE);
+        }
+        if (t == NULL) {
+            /* ignore truncated output */
+            gchar buf[GUEST_EXEC_IO_SIZE];
+
+            p->truncated = true;
+            gstatus = g_io_channel_read_chars(ch, buf, sizeof(buf),
+                                              &bytes_read, NULL);
+            if (gstatus == G_IO_STATUS_EOF || gstatus == G_IO_STATUS_ERROR) {
+                goto close;
+            }
+
+            return TRUE;
+        }
+        p->size += GUEST_EXEC_IO_SIZE;
+        p->data = t;
+    }
+
+    /* Calling read API once.
+     * On next available data our callback will be called again */
+    gstatus = g_io_channel_read_chars(ch, (gchar *)p->data + p->length,
+            p->size - p->length, &bytes_read, NULL);
+    if (gstatus == G_IO_STATUS_EOF || gstatus == G_IO_STATUS_ERROR) {
+        goto close;
+    }
+
+    p->length += bytes_read;
+
+    return TRUE;
+
+close:
+    g_io_channel_unref(ch);
+    g_atomic_int_set(&p->closed, 1);
+    return FALSE;
+}
+
 GuestExec *qmp_guest_exec(const char *path,
                        bool has_arg, strList *arg,
                        bool has_env, strList *env,
@@ -244,6 +377,10 @@ GuestExec *qmp_guest_exec(const char *path,
     strList arglist;
     gboolean ret;
     GError *gerr = NULL;
+    gint in_fd, out_fd, err_fd;
+    GIOChannel *in_ch, *out_ch, *err_ch;
+    GSpawnFlags flags;
+    bool has_output = (has_capture_output && capture_output);
 
     arglist.value = (char *)path;
     arglist.next = has_arg ? arg : NULL;
@@ -251,11 +388,14 @@ GuestExec *qmp_guest_exec(const char *path,
     argv = guest_exec_get_args(&arglist, true);
     envp = guest_exec_get_args(has_env ? env : NULL, false);
 
-    ret = g_spawn_async_with_pipes(NULL, argv, envp,
-            G_SPAWN_SEARCH_PATH |
-            G_SPAWN_DO_NOT_REAP_CHILD |
-            G_SPAWN_STDOUT_TO_DEV_NULL | G_SPAWN_STDERR_TO_DEV_NULL,
-            guest_exec_task_setup, NULL, &pid, NULL, NULL, NULL, &gerr);
+    flags = G_SPAWN_SEARCH_PATH | G_SPAWN_DO_NOT_REAP_CHILD;
+    if (!has_output) {
+        flags |= G_SPAWN_STDOUT_TO_DEV_NULL | G_SPAWN_STDERR_TO_DEV_NULL;
+    }
+
+    ret = g_spawn_async_with_pipes(NULL, argv, envp, flags,
+            guest_exec_task_setup, NULL, &pid, has_inp_data ? &in_fd : NULL,
+            has_output ? &out_fd : NULL, has_output ? &err_fd : NULL, &gerr);
     if (!ret) {
         error_setg(err, QERR_QGA_COMMAND_FAILED, gerr->message);
         g_error_free(gerr);
@@ -266,8 +406,40 @@ GuestExec *qmp_guest_exec(const char *path,
     ge->pid = (int64_t)pid;
 
     gei = guest_exec_info_add(pid);
+    gei->has_output = has_output;
     g_child_watch_add(pid, guest_exec_child_watch, gei);
 
+    if (has_inp_data) {
+        gei->in.data = g_base64_decode(inp_data, &gei->in.size);
+#ifdef G_OS_WIN32
+        in_ch = g_io_channel_win32_new_fd(in_fd);
+#else
+        in_ch = g_io_channel_unix_new(in_fd);
+#endif
+        g_io_channel_set_encoding(in_ch, NULL, NULL);
+        g_io_channel_set_buffered(in_ch, false);
+        g_io_channel_set_flags(in_ch, G_IO_FLAG_NONBLOCK, NULL);
+        g_io_add_watch(in_ch, G_IO_OUT, guest_exec_input_watch, &gei->in);
+    }
+
+    if (has_output) {
+#ifdef G_OS_WIN32
+        out_ch = g_io_channel_win32_new_fd(out_fd);
+        err_ch = g_io_channel_win32_new_fd(err_fd);
+#else
+        out_ch = g_io_channel_unix_new(out_fd);
+        err_ch = g_io_channel_unix_new(err_fd);
+#endif
+        g_io_channel_set_encoding(out_ch, NULL, NULL);
+        g_io_channel_set_encoding(err_ch, NULL, NULL);
+        g_io_channel_set_buffered(out_ch, false);
+        g_io_channel_set_buffered(err_ch, false);
+        g_io_add_watch(out_ch, G_IO_IN | G_IO_HUP,
+                guest_exec_output_watch, &gei->out);
+        g_io_add_watch(err_ch, G_IO_IN | G_IO_HUP,
+                guest_exec_output_watch, &gei->err);
+    }
+
 done:
     g_free(argv);
     g_free(envp);
diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index 6143632..6f5ea50 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -941,12 +941,17 @@
 # @err-data: #optional base64-encoded stderr of the process
 #       Note: @out-data and @err-data are present only
 #       if 'capture-output' was specified for 'guest-exec'
+# @out-truncated: #optional true if stdout was not fully captured
+#       due to size limitation.
+# @err-truncated: #optional true if stderr was not fully captured
+#       due to size limitation.
 #
 # Since: 2.5
 ##
 { 'struct': 'GuestExecStatus',
   'data': { 'exited': 'bool', '*exitcode': 'int', '*signal': 'int',
-            '*out-data': 'str', '*err-data': 'str' }}
+            '*out-data': 'str', '*err-data': 'str',
+            '*out-truncated': 'bool', '*err-truncated': 'bool' }}
 ##
 # @guest-exec-status
 #
-- 
2.1.4