gio: Add DTLS interfaces

Add a new GDtlsConnection interface, plus derived GDtlsClientConnection
and GDtlsServerConnection interfaces, for implementing Datagram TLS
support in glib-networking.

A GDtlsConnection is a GDatagramBased, so may be used as a normal
datagram socket, wrapping all datagrams from a base GDatagramBased in
DTLS segments.

Test cases are included in the implementation in glib-networking.

https://bugzilla.gnome.org/show_bug.cgi?id=752240

gio/gdtlsserverconnection.c

@@ -0,0 +1,95 @@
+/* GIO - GLib Input, Output and Streaming Library
+ *
+ * Copyright © 2010 Red Hat, Inc
+ * Copyright © 2015 Collabora, Ltd.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+#include "glib.h"
+
+#include "gdtlsserverconnection.h"
+#include "ginitable.h"
+#include "gioenumtypes.h"
+#include "gsocket.h"
+#include "gtlsbackend.h"
+#include "gtlscertificate.h"
+#include "glibintl.h"
+
+/**
+ * SECTION:gdtlsserverconnection
+ * @short_description: DTLS server-side connection
+ * @include: gio/gio.h
+ *
+ * #GDtlsServerConnection is the server-side subclass of #GDtlsConnection,
+ * representing a server-side DTLS connection.
+ *
+ * Since: 2.48
+ */
+
+G_DEFINE_INTERFACE (GDtlsServerConnection, g_dtls_server_connection,
+                    G_TYPE_DTLS_CONNECTION)
+
+static void
+g_dtls_server_connection_default_init (GDtlsServerConnectionInterface *iface)
+{
+  /**
+   * GDtlsServerConnection:authentication-mode:
+   *
+   * The #GTlsAuthenticationMode for the server. This can be changed
+   * before calling g_dtls_connection_handshake() if you want to
+   * rehandshake with a different mode from the initial handshake.
+   *
+   * Since: 2.48
+   */
+  g_object_interface_install_property (iface,
+                                       g_param_spec_enum ("authentication-mode",
+                                                          P_("Authentication Mode"),
+                                                          P_("The client authentication mode"),
+                                                          G_TYPE_TLS_AUTHENTICATION_MODE,
+                                                          G_TLS_AUTHENTICATION_NONE,
+                                                          G_PARAM_READWRITE |
+                                                          G_PARAM_STATIC_STRINGS));
+}
+
+/**
+ * g_dtls_server_connection_new:
+ * @base_socket: the #GDatagramBased to wrap
+ * @certificate: (allow-none): the default server certificate, or %NULL
+ * @error: #GError for error reporting, or %NULL to ignore
+ *
+ * Creates a new #GDtlsServerConnection wrapping @base_socket.
+ *
+ * Returns: (transfer full) (type GDtlsServerConnection): the new
+ *   #GDtlsServerConnection, or %NULL on error
+ *
+ * Since: 2.48
+ */
+GDatagramBased *
+g_dtls_server_connection_new (GDatagramBased   *base_socket,
+                              GTlsCertificate  *certificate,
+                              GError          **error)
+{
+  GObject *conn;
+  GTlsBackend *backend;
+
+  backend = g_tls_backend_get_default ();
+  conn = g_initable_new (g_tls_backend_get_dtls_server_connection_type (backend),
+                         NULL, error,
+                         "base-socket", base_socket,
+                         "certificate", certificate,
+                         NULL);
+  return G_DATAGRAM_BASED (conn);
+}