Add a task dispatcher for gnutls_bye similar to the
qio_channel_tls_handshake_task(). The gnutls_bye() call might be
interrupted and so it needs to be rescheduled.

The migration code will make use of this to help the migration
destination identify a premature EOF. Once the session termination is
in place, any EOF that happens before the source issued gnutls_bye()
will be considered an error.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 include/io/channel-tls.h | 12 ++++++
 io/channel-tls.c         | 84 ++++++++++++++++++++++++++++++++++++++++
 io/trace-events          |  5 +++
 3 files changed, 101 insertions(+)

diff --git a/include/io/channel-tls.h b/include/io/channel-tls.h
index 26c67f17e2..7e9023570d 100644
--- a/include/io/channel-tls.h
+++ b/include/io/channel-tls.h
@@ -49,8 +49,20 @@ struct QIOChannelTLS {
     QCryptoTLSSession *session;
     QIOChannelShutdown shutdown;
     guint hs_ioc_tag;
+    guint bye_ioc_tag;
 };
 
+/**
+ * qio_channel_tls_bye:
+ * @ioc: the TLS channel object
+ * @errp: pointer to a NULL-initialized error object
+ *
+ * Perform the TLS session termination. This method will return
+ * immediately and the termination will continue in the background,
+ * provided the main loop is running.
+ */
+void qio_channel_tls_bye(QIOChannelTLS *ioc, Error **errp);
+
 /**
  * qio_channel_tls_new_server:
  * @master: the underlying channel object
diff --git a/io/channel-tls.c b/io/channel-tls.c
index aab630e5ae..517ce190a4 100644
--- a/io/channel-tls.c
+++ b/io/channel-tls.c
@@ -247,6 +247,85 @@ void qio_channel_tls_handshake(QIOChannelTLS *ioc,
     qio_channel_tls_handshake_task(ioc, task, context);
 }
 
+static gboolean qio_channel_tls_bye_io(QIOChannel *ioc, GIOCondition condition,
+                                       gpointer user_data);
+
+static void qio_channel_tls_bye_task(QIOChannelTLS *ioc, QIOTask *task,
+                                     GMainContext *context)
+{
+    GIOCondition condition;
+    QIOChannelTLSData *data;
+    int status;
+    Error *err = NULL;
+
+    status = qcrypto_tls_session_bye(ioc->session, &err);
+
+    if (status < 0) {
+        trace_qio_channel_tls_bye_fail(ioc);
+        qio_task_set_error(task, err);
+        qio_task_complete(task);
+        return;
+    }
+
+    if (status == QCRYPTO_TLS_BYE_COMPLETE) {
+        qio_task_complete(task);
+        return;
+    }
+
+    data = g_new0(typeof(*data), 1);
+    data->task = task;
+    data->context = context;
+
+    if (context) {
+        g_main_context_ref(context);
+    }
+
+    if (status == QCRYPTO_TLS_BYE_SENDING) {
+        condition = G_IO_OUT;
+    } else {
+        condition = G_IO_IN;
+    }
+
+    trace_qio_channel_tls_bye_pending(ioc, status);
+    ioc->bye_ioc_tag = qio_channel_add_watch_full(ioc->master, condition,
+                                                  qio_channel_tls_bye_io,
+                                                  data, NULL, context);
+}
+
+
+static gboolean qio_channel_tls_bye_io(QIOChannel *ioc, GIOCondition condition,
+                                       gpointer user_data)
+{
+    QIOChannelTLSData *data = user_data;
+    QIOTask *task = data->task;
+    GMainContext *context = data->context;
+    QIOChannelTLS *tioc = QIO_CHANNEL_TLS(qio_task_get_source(task));
+
+    tioc->bye_ioc_tag = 0;
+    g_free(data);
+    qio_channel_tls_bye_task(tioc, task, context);
+
+    if (context) {
+        g_main_context_unref(context);
+    }
+
+    return FALSE;
+}
+
+static void propagate_error(QIOTask *task, gpointer opaque)
+{
+    qio_task_propagate_error(task, opaque);
+}
+
+void qio_channel_tls_bye(QIOChannelTLS *ioc, Error **errp)
+{
+    QIOTask *task;
+
+    task = qio_task_new(OBJECT(ioc), propagate_error, errp, NULL);
+
+    trace_qio_channel_tls_bye_start(ioc);
+    qio_channel_tls_bye_task(ioc, task, NULL);
+}
 
 static void qio_channel_tls_init(Object *obj G_GNUC_UNUSED)
 {
@@ -379,6 +458,11 @@ static int qio_channel_tls_close(QIOChannel *ioc,
         g_clear_handle_id(&tioc->hs_ioc_tag, g_source_remove);
     }
 
+    if (tioc->bye_ioc_tag) {
+        trace_qio_channel_tls_bye_cancel(ioc);
+        g_clear_handle_id(&tioc->bye_ioc_tag, g_source_remove);
+    }
+
     return qio_channel_close(tioc->master, errp);
 }
 
diff --git a/io/trace-events b/io/trace-events
index d4c0f84a9a..dc3a63ba1f 100644
--- a/io/trace-events
+++ b/io/trace-events
@@ -44,6 +44,11 @@ qio_channel_tls_handshake_pending(void *ioc, int status) "TLS handshake pending
 qio_channel_tls_handshake_fail(void *ioc) "TLS handshake fail ioc=%p"
 qio_channel_tls_handshake_complete(void *ioc) "TLS handshake complete ioc=%p"
 qio_channel_tls_handshake_cancel(void *ioc) "TLS handshake cancel ioc=%p"
+qio_channel_tls_bye_start(void *ioc) "TLS termination start ioc=%p"
+qio_channel_tls_bye_pending(void *ioc, int status) "TLS termination pending ioc=%p status=%d"
+qio_channel_tls_bye_fail(void *ioc) "TLS termination fail ioc=%p"
+qio_channel_tls_bye_complete(void *ioc) "TLS termination complete ioc=%p"
+qio_channel_tls_bye_cancel(void *ioc) "TLS termination cancel ioc=%p"
 qio_channel_tls_credentials_allow(void *ioc) "TLS credentials allow ioc=%p"
 qio_channel_tls_credentials_deny(void *ioc) "TLS credentials deny ioc=%p"
 
-- 
2.35.3