migration: Add helpers to detect TLS capability

Add migrate_channel_requires_tls() to detect whether the specific channel
requires TLS, leveraging the recently introduced migrate_use_tls().  No
functional change intended.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20220707185513.27421-1-peterx@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

migration/channel.c

@@ -38,9 +38,7 @@ void migration_channel_process_incoming(QIOChannel *ioc)
     trace_migration_set_incoming_channel(
         ioc, object_get_typename(OBJECT(ioc)));
 
-    if (migrate_use_tls() &&
-        !object_dynamic_cast(OBJECT(ioc),
-                             TYPE_QIO_CHANNEL_TLS)) {
+    if (migrate_channel_requires_tls_upgrade(ioc)) {
         migration_tls_channel_process_incoming(s, ioc, &local_err);
     } else {
         migration_ioc_register_yank(ioc);
@@ -70,10 +68,7 @@ void migration_channel_connect(MigrationState *s,
         ioc, object_get_typename(OBJECT(ioc)), hostname, error);
 
     if (!error) {
-        if (s->parameters.tls_creds &&
-            *s->parameters.tls_creds &&
-            !object_dynamic_cast(OBJECT(ioc),
-                                 TYPE_QIO_CHANNEL_TLS)) {
+        if (migrate_channel_requires_tls_upgrade(ioc)) {
             migration_tls_channel_connect(s, ioc, hostname, &error);
 
             if (!error) {

migration/migration.c

@@ -48,6 +48,7 @@
 #include "trace.h"
 #include "exec/target_page.h"
 #include "io/channel-buffer.h"
+#include "io/channel-tls.h"
 #include "migration/colo.h"
 #include "hw/boards.h"
 #include "hw/qdev-properties.h"

migration/multifd.c

@@ -831,9 +831,7 @@ static bool multifd_channel_connect(MultiFDSendParams *p,
         migrate_get_current()->hostname, error);
 
     if (!error) {
-        if (migrate_use_tls() &&
-            !object_dynamic_cast(OBJECT(ioc),
-                                 TYPE_QIO_CHANNEL_TLS)) {
+        if (migrate_channel_requires_tls_upgrade(ioc)) {
             multifd_tls_channel_connect(p, ioc, &error);
             if (!error) {
                 /*

migration/tls.c

@@ -166,3 +166,12 @@ void migration_tls_channel_connect(MigrationState *s,
                               NULL,
                               NULL);
 }
+
+bool migrate_channel_requires_tls_upgrade(QIOChannel *ioc)
+{
+    if (!migrate_use_tls()) {
+        return false;
+    }
+
+    return !object_dynamic_cast(OBJECT(ioc), TYPE_QIO_CHANNEL_TLS);
+}

migration/tls.h

@@ -37,4 +37,8 @@ void migration_tls_channel_connect(MigrationState *s,
                                    QIOChannel *ioc,
                                    const char *hostname,
                                    Error **errp);
+
+/* Whether the QIO channel requires further TLS handshake? */
+bool migrate_channel_requires_tls_upgrade(QIOChannel *ioc);
+
 #endif