yank: Unregister function when using TLS migration

After yank feature was introduced in migration, whenever migration
is started using TLS, the following error happens in both source and
destination hosts:

(qemu) qemu-kvm: ../util/yank.c:107: yank_unregister_instance:
Assertion `QLIST_EMPTY(&entry->yankfns)' failed.

This happens because of a missing yank_unregister_function() when using
qio-channel-tls.

Fix this by also allowing TYPE_QIO_CHANNEL_TLS object type to perform
yank_unregister_function() in channel_close() and multifd_load_cleanup().

Also, inside migration_channel_connect() and
migration_channel_process_incoming() move yank_register_function() so
it only runs once on a TLS migration.

Fixes: b5eea99ec2 ("migration: Add yank feature", 2021-01-13)
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1964326
Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
Reviewed-by: Lukas Straub <lukasstraub2@web.de>
Reviewed-by: Peter Xu <peterx@redhat.com>

--
Changes since v2:
- Dropped all references to ioc->master
- yank_register_function() and yank_unregister_function() now only run
  once in a TLS migration.

Changes since v1:
- Cast p->c to QIOChannelTLS into multifd_load_cleanup()
Message-Id: <20210601054030.1153249-1-leobras.c@gmail.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

migration/channel.c

@@ -38,18 +38,19 @@ void migration_channel_process_incoming(QIOChannel *ioc)
     trace_migration_set_incoming_channel(
         ioc, object_get_typename(OBJECT(ioc)));
 
-    if (object_dynamic_cast(OBJECT(ioc), TYPE_QIO_CHANNEL_SOCKET)) {
-        yank_register_function(MIGRATION_YANK_INSTANCE,
-                               migration_yank_iochannel,
-                               QIO_CHANNEL(ioc));
-    }
-
     if (s->parameters.tls_creds &&
         *s->parameters.tls_creds &&
         !object_dynamic_cast(OBJECT(ioc),
                              TYPE_QIO_CHANNEL_TLS)) {
         migration_tls_channel_process_incoming(s, ioc, &local_err);
     } else {
+        if (object_dynamic_cast(OBJECT(ioc), TYPE_QIO_CHANNEL_SOCKET) ||
+            object_dynamic_cast(OBJECT(ioc), TYPE_QIO_CHANNEL_TLS)) {
+            yank_register_function(MIGRATION_YANK_INSTANCE,
+                                   migration_yank_iochannel,
+                                   QIO_CHANNEL(ioc));
+        }
+
         migration_ioc_process_incoming(ioc, &local_err);
     }
 
@@ -76,12 +77,6 @@ void migration_channel_connect(MigrationState *s,
         ioc, object_get_typename(OBJECT(ioc)), hostname, error);
 
     if (!error) {
-        if (object_dynamic_cast(OBJECT(ioc), TYPE_QIO_CHANNEL_SOCKET)) {
-            yank_register_function(MIGRATION_YANK_INSTANCE,
-                                   migration_yank_iochannel,
-                                   QIO_CHANNEL(ioc));
-        }
-
         if (s->parameters.tls_creds &&
             *s->parameters.tls_creds &&
             !object_dynamic_cast(OBJECT(ioc),
@@ -99,6 +94,13 @@ void migration_channel_connect(MigrationState *s,
         } else {
             QEMUFile *f = qemu_fopen_channel_output(ioc);
 
+            if (object_dynamic_cast(OBJECT(ioc), TYPE_QIO_CHANNEL_SOCKET) ||
+                object_dynamic_cast(OBJECT(ioc), TYPE_QIO_CHANNEL_TLS)) {
+                yank_register_function(MIGRATION_YANK_INSTANCE,
+                                       migration_yank_iochannel,
+                                       QIO_CHANNEL(ioc));
+            }
+
             qemu_mutex_lock(&s->qemu_file_lock);
             s->to_dst_file = f;
             qemu_mutex_unlock(&s->qemu_file_lock);

migration/multifd.c

@@ -987,7 +987,8 @@ int multifd_load_cleanup(Error **errp)
     for (i = 0; i < migrate_multifd_channels(); i++) {
         MultiFDRecvParams *p = &multifd_recv_state->params[i];
 
-        if (object_dynamic_cast(OBJECT(p->c), TYPE_QIO_CHANNEL_SOCKET)
+        if ((object_dynamic_cast(OBJECT(p->c), TYPE_QIO_CHANNEL_SOCKET) ||
+             object_dynamic_cast(OBJECT(p->c), TYPE_QIO_CHANNEL_TLS))
             && OBJECT(p->c)->ref == 1) {
             yank_unregister_function(MIGRATION_YANK_INSTANCE,
                                      migration_yank_iochannel,

migration/qemu-file-channel.c

@@ -26,6 +26,7 @@
 #include "qemu-file-channel.h"
 #include "qemu-file.h"
 #include "io/channel-socket.h"
+#include "io/channel-tls.h"
 #include "qemu/iov.h"
 #include "qemu/yank.h"
 #include "yank_functions.h"
@@ -106,7 +107,8 @@ static int channel_close(void *opaque, Error **errp)
     int ret;
     QIOChannel *ioc = QIO_CHANNEL(opaque);
     ret = qio_channel_close(ioc, errp);
-    if (object_dynamic_cast(OBJECT(ioc), TYPE_QIO_CHANNEL_SOCKET)
+    if ((object_dynamic_cast(OBJECT(ioc), TYPE_QIO_CHANNEL_SOCKET) ||
+         object_dynamic_cast(OBJECT(ioc), TYPE_QIO_CHANNEL_TLS))
         && OBJECT(ioc)->ref == 1) {
         yank_unregister_function(MIGRATION_YANK_INSTANCE,
                                  migration_yank_iochannel,