[PATCH 04/20] migration: file URI

[Steve Sistare]

Extend the migration URI to support file:<filename>.  This can be used for
any migration scenario that does not require a reverse path.  It can be used
as an alternative to 'exec:cat > file' in minimized containers that do not
contain /bin/sh, and it is easier to use than the fd:<fdname> URI.  It can
be used in HMP commands, and as a qemu command-line parameter.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 migration/file.c       | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++
 migration/file.h       | 14 ++++++++++++
 migration/meson.build  |  1 +
 migration/migration.c  |  5 ++++
 migration/trace-events |  4 ++++
 qemu-options.hx        |  6 ++++-
 6 files changed, 91 insertions(+), 1 deletion(-)
 create mode 100644 migration/file.c
 create mode 100644 migration/file.h

diff --git a/migration/file.c b/migration/file.c
new file mode 100644
index 0000000..8e35827
--- /dev/null
+++ b/migration/file.c
@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2021-2023 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "channel.h"
+#include "file.h"
+#include "migration.h"
+#include "io/channel-file.h"
+#include "io/channel-util.h"
+#include "trace.h"
+
+void file_start_outgoing_migration(MigrationState *s, const char *filename,
+                                   Error **errp)
+{
+    g_autoptr(QIOChannelFile) fioc = NULL;
+    QIOChannel *ioc;
+
+    trace_migration_file_outgoing(filename);
+
+    fioc = qio_channel_file_new_path(filename, O_CREAT | O_WRONLY | O_TRUNC,
+                                     0600, errp);
+    if (!fioc) {
+        return;
+    }
+
+    ioc = QIO_CHANNEL(fioc);
+    qio_channel_set_name(ioc, "migration-file-outgoing");
+    migration_channel_connect(s, ioc, NULL, NULL);
+}
+
+static gboolean file_accept_incoming_migration(QIOChannel *ioc,
+                                               GIOCondition condition,
+                                               gpointer opaque)
+{
+    migration_channel_process_incoming(ioc);
+    object_unref(OBJECT(ioc));
+    return G_SOURCE_REMOVE;
+}
+
+void file_start_incoming_migration(const char *filename, Error **errp)
+{
+    QIOChannelFile *fioc = NULL;
+    QIOChannel *ioc;
+
+    trace_migration_file_incoming(filename);
+
+    fioc = qio_channel_file_new_path(filename, O_RDONLY, 0, errp);
+    if (!fioc) {
+        return;
+    }
+
+    ioc = QIO_CHANNEL(fioc);
+    qio_channel_set_name(QIO_CHANNEL(ioc), "migration-file-incoming");
+    qio_channel_add_watch_full(ioc, G_IO_IN,
+                               file_accept_incoming_migration,
+                               NULL, NULL,
+                               g_main_context_get_thread_default());
+}
diff --git a/migration/file.h b/migration/file.h
new file mode 100644
index 0000000..841b94a
--- /dev/null
+++ b/migration/file.h
@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2021-2023 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef QEMU_MIGRATION_FILE_H
+#define QEMU_MIGRATION_FILE_H
+void file_start_incoming_migration(const char *filename, Error **errp);
+
+void file_start_outgoing_migration(MigrationState *s, const char *filename,
+                                   Error **errp);
+#endif
diff --git a/migration/meson.build b/migration/meson.build
index 8ba6e42..3af817e 100644
--- a/migration/meson.build
+++ b/migration/meson.build
@@ -16,6 +16,7 @@ softmmu_ss.add(files(
   'dirtyrate.c',
   'exec.c',
   'fd.c',
+  'file.c',
   'global_state.c',
   'migration-hmp-cmds.c',
   'migration.c',
diff --git a/migration/migration.c b/migration/migration.c
index dc05c6f..cfbde86 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -20,6 +20,7 @@
 #include "migration/blocker.h"
 #include "exec.h"
 #include "fd.h"
+#include "file.h"
 #include "socket.h"
 #include "sysemu/runstate.h"
 #include "sysemu/sysemu.h"
@@ -442,6 +443,8 @@ static void qemu_start_incoming_migration(const char *uri, 
Error **errp)
         exec_start_incoming_migration(p, errp);
     } else if (strstart(uri, "fd:", &p)) {
         fd_start_incoming_migration(p, errp);
+    } else if (strstart(uri, "file:", &p)) {
+        file_start_incoming_migration(p, errp);
     } else {
         error_setg(errp, "unknown migration protocol: %s", uri);
     }
@@ -1662,6 +1665,8 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
         exec_start_outgoing_migration(s, p, &local_err);
     } else if (strstart(uri, "fd:", &p)) {
         fd_start_outgoing_migration(s, p, &local_err);
+    } else if (strstart(uri, "file:", &p)) {
+        file_start_outgoing_migration(s, p, &local_err);
     } else {
         if (!(has_resume && resume)) {
             yank_unregister_instance(MIGRATION_YANK_INSTANCE);
diff --git a/migration/trace-events b/migration/trace-events
index cdaef7a..c8c1771 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -307,6 +307,10 @@ migration_exec_incoming(const char *cmd) "cmd=%s"
 migration_fd_outgoing(int fd) "fd=%d"
 migration_fd_incoming(int fd) "fd=%d"
 
+# file.c
+migration_file_outgoing(const char *filename) "filename=%s"
+migration_file_incoming(const char *filename) "filename=%s"
+
 # socket.c
 migration_socket_incoming_accepted(void) ""
 migration_socket_outgoing_connected(const char *hostname) "hostname=%s"
diff --git a/qemu-options.hx b/qemu-options.hx
index b37eb96..b93449d 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4610,6 +4610,7 @@ DEF("incoming", HAS_ARG, QEMU_OPTION_incoming, \
     "                prepare for incoming migration, listen on\n" \
     "                specified protocol and socket address\n" \
     "-incoming fd:fd\n" \
+    "-incoming file:filename\n" \
     "-incoming exec:cmdline\n" \
     "                accept incoming migration on given file descriptor\n" \
     "                or from given external command\n" \
@@ -4626,7 +4627,10 @@ SRST
     Prepare for incoming migration, listen on a given unix socket.
 
 ``-incoming fd:fd``
-    Accept incoming migration from a given filedescriptor.
+    Accept incoming migration from a given file descriptor.
+
+``-incoming file:filename``
+    Accept incoming migration from a given file.
 
 ``-incoming exec:cmdline``
     Accept incoming migration as an output from specified external
-- 
1.8.3.1