[balsa] Implement testing reachability of a server

[Peter Bloomfield <peterb src gnome org>]

commit 71f2908adc0173a6a35e3520c5836b6630171c07
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Mon May 22 18:29:23 2017 -0400

    Implement testing reachability of a server
    
        * libbalsa/server.c (libbalsa_server_can_reach_cb),
          (libbalsa_server_test_can_reach_full),
          (libbalsa_server_test_can_reach): new methods for testing
          whether a server's host can be reached over the network;
        * libbalsa/server.h: declare them.

 ChangeLog         |   10 +++++++++
 libbalsa/server.c |   56 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 libbalsa/server.h |   12 +++++++++++
 3 files changed, 78 insertions(+), 0 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index c0e5f16..c1b3ee3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2017-05-22  Peter Bloomfield  <pbloomfield bellsouth net>
+
+       Implement testing reachability of a server
+
+       * libbalsa/server.c (libbalsa_server_can_reach_cb),
+         (libbalsa_server_test_can_reach_full),
+         (libbalsa_server_test_can_reach): new methods for testing
+         whether a server's host can be reached over the network;
+       * libbalsa/server.h: declare them.
+
 2017-05-14  Peter Bloomfield  <pbloomfield bellsouth net>
 
        * libbalsa/imap/imap-handle.c (idle_start): clear
diff --git a/libbalsa/server.c b/libbalsa/server.c
index 6dcd95e..5711829 100644
--- a/libbalsa/server.c
+++ b/libbalsa/server.c
@@ -689,3 +689,59 @@ libbalsa_server_get_cert_pass(NetClient        *client,
        /* FIXME - we just return the passphrase from the config, but we may also want to show a dialogue 
here... */
        return g_strdup(LIBBALSA_SERVER(user_data)->cert_passphrase);
 }
+
+/* Test whether a server is reachable */
+
+typedef struct {
+    LibBalsaCanReachCallback * cb;
+    gpointer                   cb_data;
+    GObject                  * source_object;
+} CanReachInfo;
+
+static void
+libbalsa_server_can_reach_cb(GObject      * monitor,
+                             GAsyncResult * res,
+                             gpointer       user_data)
+{
+    CanReachInfo *info = user_data;
+    gboolean can_reach;
+
+    can_reach = g_network_monitor_can_reach_finish((GNetworkMonitor *) monitor, res, NULL);
+    info->cb(info->source_object, can_reach, info->cb_data);
+
+    g_object_unref(info->source_object);
+    g_free(info);
+}
+
+void
+libbalsa_server_test_can_reach_full(LibBalsaServer           * server,
+                                    LibBalsaCanReachCallback * cb,
+                                    gpointer                   cb_data,
+                                    GObject                  * source_object)
+{
+    CanReachInfo *info;
+    const gchar *host;
+    GNetworkMonitor *monitor;
+    GSocketConnectable *address;
+
+    info = g_new(CanReachInfo, 1);
+    info->cb              = cb;
+    info->cb_data         = cb_data;
+    info->source_object = g_object_ref(source_object);
+
+    monitor = g_network_monitor_get_default();
+
+    host = server->host;
+    address = g_network_address_new(host, 0);
+    g_network_monitor_can_reach_async(monitor, address, NULL,
+                                      libbalsa_server_can_reach_cb, info);
+    g_object_unref(address);
+}
+
+void
+libbalsa_server_test_can_reach(LibBalsaServer           * server,
+                               LibBalsaCanReachCallback * cb,
+                               gpointer                   cb_data)
+{
+    libbalsa_server_test_can_reach_full(server, cb, cb_data, (GObject *) server);
+}
diff --git a/libbalsa/server.h b/libbalsa/server.h
index 7b43ee5..af30ade 100644
--- a/libbalsa/server.h
+++ b/libbalsa/server.h
@@ -132,4 +132,16 @@ gchar *libbalsa_server_get_cert_pass(NetClient        *client,
 void libbalsa_server_connect_signals(LibBalsaServer * server, GCallback cb,
                                      gpointer cb_data);
 
+/* Check whether a server can be reached */
+
+void libbalsa_server_test_can_reach(LibBalsaServer           * server,
+                                    LibBalsaCanReachCallback * cb,
+                                    gpointer                   cb_data);
+
+/* Private: used only by LibBalsaMailboxRemote */
+void libbalsa_server_test_can_reach_full(LibBalsaServer           * server,
+                                         LibBalsaCanReachCallback * cb,
+                                         gpointer                   cb_data,
+                                         GObject                  * source_object);
+
 #endif                         /* __LIBBALSA_SERVER_H__ */