migration: convert exec socket protocol to use QIOChannel

Convert the exec socket migration protocol driver to use
QIOChannel and QEMUFileChannel, instead of the stdio
popen APIs. It can be unconditionally built because the
QIOChannelCommand class can report suitable error messages
on platforms which can't fork processes.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
Message-Id: <1461751518-12128-17-git-send-email-berrange@redhat.com>
Signed-off-by: NAmit Shah <amit.shah@redhat.com>

migration/Makefile.objs

-common-obj-y += migration.o socket.o fd.o
+common-obj-y += migration.o socket.o fd.o exec.o
 common-obj-y += vmstate.o
 common-obj-y += qemu-file.o qemu-file-buf.o qemu-file-unix.o qemu-file-stdio.o
 common-obj-y += qemu-file-channel.o
@@ -6,7 +6,6 @@ common-obj-y += xbzrle.o postcopy-ram.o
 common-obj-y += qjson.o
 
 common-obj-$(CONFIG_RDMA) += rdma.o
-common-obj-$(CONFIG_POSIX) += exec.o
 
 common-obj-y += block.o
 

migration/exec.c

@@ -3,10 +3,12 @@
  *
  * Copyright IBM, Corp. 2008
  * Copyright Dell MessageOne 2008
+ * Copyright Red Hat, Inc. 2015-2016
  *
  * Authors:
  *  Anthony Liguori   <aliguori@us.ibm.com>
  *  Charles Duffy     <charles_duffy@messageone.com>
+ *  Daniel P. Berrange <berrange@redhat.com>
  *
  * This work is licensed under the terms of the GNU GPL, version 2.  See
  * the COPYING file in the top-level directory.
@@ -18,53 +20,53 @@
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "qemu-common.h"
-#include "qemu/sockets.h"
-#include "qemu/main-loop.h"
 #include "migration/migration.h"
-#include "migration/qemu-file.h"
-#include "block/block.h"
-#include <sys/wait.h>
+#include "io/channel-command.h"
+#include "trace.h"
 
-//#define DEBUG_MIGRATION_EXEC
-
-#ifdef DEBUG_MIGRATION_EXEC
-#define DPRINTF(fmt, ...) \
-    do { printf("migration-exec: " fmt, ## __VA_ARGS__); } while (0)
-#else
-#define DPRINTF(fmt, ...) \
-    do { } while (0)
-#endif
 
 void exec_start_outgoing_migration(MigrationState *s, const char *command, Error **errp)
 {
-    s->to_dst_file = qemu_popen_cmd(command, "w");
-    if (s->to_dst_file == NULL) {
-        error_setg_errno(errp, errno, "failed to popen the migration target");
+    QIOChannel *ioc;
+    const char *argv[] = { "/bin/sh", "-c", command, NULL };
+
+    trace_migration_exec_outgoing(command);
+    ioc = QIO_CHANNEL(qio_channel_command_new_spawn(argv,
+                                                    O_WRONLY,
+                                                    errp));
+    if (!ioc) {
         return;
     }
 
-    migrate_fd_connect(s);
+    migration_set_outgoing_channel(s, ioc);
+    object_unref(OBJECT(ioc));
 }
 
-static void exec_accept_incoming_migration(void *opaque)
+static gboolean exec_accept_incoming_migration(QIOChannel *ioc,
+                                               GIOCondition condition,
+                                               gpointer opaque)
 {
-    QEMUFile *f = opaque;
-
-    qemu_set_fd_handler(qemu_get_fd(f), NULL, NULL, NULL);
-    process_incoming_migration(f);
+    migration_set_incoming_channel(migrate_get_current(), ioc);
+    object_unref(OBJECT(ioc));
+    return FALSE; /* unregister */
 }
 
 void exec_start_incoming_migration(const char *command, Error **errp)
 {
-    QEMUFile *f;
+    QIOChannel *ioc;
+    const char *argv[] = { "/bin/sh", "-c", command, NULL };
 
-    DPRINTF("Attempting to start an incoming migration\n");
-    f = qemu_popen_cmd(command, "r");
-    if(f == NULL) {
-        error_setg_errno(errp, errno, "failed to popen the migration source");
+    trace_migration_exec_incoming(command);
+    ioc = QIO_CHANNEL(qio_channel_command_new_spawn(argv,
+                                                    O_RDONLY,
+                                                    errp));
+    if (!ioc) {
         return;
     }
 
-    qemu_set_fd_handler(qemu_get_fd(f), exec_accept_incoming_migration, NULL,
-                        f);
+    qio_channel_add_watch(ioc,
+                          G_IO_IN,
+                          exec_accept_incoming_migration,
+                          NULL,
+                          NULL);
 }

migration/migration.c

@@ -311,10 +311,8 @@ void qemu_start_incoming_migration(const char *uri, Error **errp)
     } else if (strstart(uri, "rdma:", &p)) {
         rdma_start_incoming_migration(p, errp);
 #endif
-#if !defined(WIN32)
     } else if (strstart(uri, "exec:", &p)) {
         exec_start_incoming_migration(p, errp);
-#endif
     } else if (strstart(uri, "unix:", &p)) {
         unix_start_incoming_migration(p, errp);
     } else if (strstart(uri, "fd:", &p)) {
@@ -1069,10 +1067,8 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
     } else if (strstart(uri, "rdma:", &p)) {
         rdma_start_outgoing_migration(s, p, &local_err);
 #endif
-#if !defined(WIN32)
     } else if (strstart(uri, "exec:", &p)) {
         exec_start_outgoing_migration(s, p, &local_err);
-#endif
     } else if (strstart(uri, "unix:", &p)) {
         unix_start_outgoing_migration(s, p, &local_err);
     } else if (strstart(uri, "fd:", &p)) {

trace-events

@@ -1595,6 +1595,10 @@ postcopy_ram_incoming_cleanup_entry(void) ""
 postcopy_ram_incoming_cleanup_exit(void) ""
 postcopy_ram_incoming_cleanup_join(void) ""
 
+# migration/exec.c
+migration_exec_outgoing(const char *cmd) "cmd=%s"
+migration_exec_incoming(const char *cmd) "cmd=%s"
+
 # migration/fd.c
 migration_fd_outgoing(int fd) "fd=%d"
 migration_fd_incoming(int fd) "fd=%d"