[PATCH v9 07/25] tools/libxl: add back channel support to read stream

[Wen Congyang <wency@cn.fujitsu.com>]

This is used by primay to read records sent by secondary.

Signed-off-by: Yang Hongyang <hongyang.yang@easystack.cn>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
---
 tools/libxl/libxl_create.c      |  1 +
 tools/libxl/libxl_internal.h    |  1 +
 tools/libxl/libxl_stream_read.c | 27 +++++++++++++++++++++++----
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 8087bcc..c2eeb9d 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -1012,6 +1012,7 @@ static void domcreate_bootloader_done(libxl__egc *egc,
     dcs->srs.dcs = dcs;
     dcs->srs.fd = restore_fd;
     dcs->srs.legacy = (dcs->restore_params.stream_version == 1);
+    dcs->srs.back_channel = false;
     dcs->srs.completion_callback = domcreate_stream_done;
 
     if (restore_fd >= 0) {
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 3cf297f..ea2cfb8 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -3418,6 +3418,7 @@ struct libxl__stream_read_state {
     libxl__domain_create_state *dcs;
     int fd;
     bool legacy;
+    bool back_channel;
     void (*completion_callback)(libxl__egc *egc,
                                 libxl__stream_read_state *srs,
                                 int rc);
diff --git a/tools/libxl/libxl_stream_read.c b/tools/libxl/libxl_stream_read.c
index 6ad2a27..6437639 100644
--- a/tools/libxl/libxl_stream_read.c
+++ b/tools/libxl/libxl_stream_read.c
@@ -104,6 +104,15 @@
  * Depending on the contents of the stream, there are likely to be several
  * parallel tasks being managed.  check_all_finished() is used to join all
  * tasks in both success and error cases.
+ *
+ * For back channel stream:
+ * - libxl__stream_read_start()
+ *    - Set up the stream to running state
+ *
+ * - libxl__stream_read_continue()
+ *     - Set up reading the next record from a started stream.
+ *       Add some codes to process_record() to handle the record.
+ *       Then call stream->checkpoint_callback() to return.
  */
 
 /* Success/error/cleanup handling. */
@@ -207,6 +216,17 @@ void libxl__stream_read_start(libxl__egc *egc,
     stream->running = true;
     stream->phase   = SRS_PHASE_NORMAL;
 
+    dc->ao       = stream->ao;
+    dc->copywhat = "restore v2 stream";
+    dc->writefd  = -1;
+
+    if (stream->back_channel) {
+        assert(!stream->legacy);
+
+        dc->readfd = stream->fd;
+        return;
+    }
+
     if (stream->legacy) {
         /* Convert the legacy stream. */
         libxl__conversion_helper_state *chs = &stream->chs;
@@ -229,10 +249,7 @@ void libxl__stream_read_start(libxl__egc *egc,
     }
     /* stream->fd is now a v2 stream. */
 
-    dc->ao       = stream->ao;
-    dc->copywhat = "restore v2 stream";
     dc->readfd   = stream->fd;
-    dc->writefd  = -1;
 
     /* Start reading the stream header. */
     rc = setup_read(stream, "stream header",
@@ -748,7 +765,9 @@ static void stream_done(libxl__egc *egc,
     LIBXL_STAILQ_FOREACH_SAFE(rec, &stream->record_queue, entry, trec)
         free_record(rec);
 
-    check_all_finished(egc, stream, rc);
+    if (!stream->back_channel)
+        /* back channel stream doesn't have restore helper */
+        check_all_finished(egc, stream, rc);
 }
 
 void libxl__xc_domain_restore_done(libxl__egc *egc, void *dcs_void,
-- 
2.5.0