From 36c79adb2fdf4eadb7a96fcb753deecb1a66eb9b Mon Sep 17 00:00:00 2001
From: Iain Lane <iainl@gnome.org>
Date: Mon, 10 Sep 2018 12:07:48 +0100
Subject: [PATCH] gnetworkmonitornetlink: Pass a GError into
 read_netlink_messages()

Currently this function calls `g_warning()` explicitly. It would be
nicer to properly propagate these failure up to the caller that tried to
initialise us.
---
 gio/gnetworkmonitornetlink.c | 78 +++++++++++++++++++++++++-----------
 1 file changed, 55 insertions(+), 23 deletions(-)

diff --git a/gio/gnetworkmonitornetlink.c b/gio/gnetworkmonitornetlink.c
index 3841e69e1..95de87929 100644
--- a/gio/gnetworkmonitornetlink.c
+++ b/gio/gnetworkmonitornetlink.c
@@ -52,9 +52,11 @@ struct _GNetworkMonitorNetlinkPrivate
   GPtrArray *dump_networks;
 };
 
-static gboolean read_netlink_messages (GSocket             *socket,
-                                       GIOCondition         condition,
-                                       gpointer             user_data);
+static gboolean read_netlink_messages (GNetworkMonitorNetlink  *nl,
+                                       GError                 **error);
+static gboolean read_netlink_messages_callback (GSocket             *socket,
+                                                GIOCondition         condition,
+                                                gpointer             user_data);
 static gboolean request_dump (GNetworkMonitorNetlink  *nl,
                               GError                 **error);
 
@@ -139,15 +141,20 @@ g_network_monitor_netlink_initable_init (GInitable     *initable,
    */
   while (nl->priv->dump_networks)
     {
-      if (!read_netlink_messages (NULL, G_IO_IN, nl))
-        break;
+      GError *local_error = NULL;
+      if (!read_netlink_messages (nl, &local_error))
+        {
+          g_warning ("%s", local_error->message);
+          g_clear_error (&local_error);
+          break;
+        }
     }
 
   g_socket_set_blocking (nl->priv->sock, FALSE);
   nl->priv->context = g_main_context_ref_thread_default ();
   nl->priv->source = g_socket_create_source (nl->priv->sock, G_IO_IN, NULL);
   g_source_set_callback (nl->priv->source,
-                         (GSourceFunc) read_netlink_messages, nl, NULL);
+                         (GSourceFunc) read_netlink_messages_callback, nl, NULL);
   g_source_attach (nl->priv->source, nl->priv->context);
 
   return initable_parent_iface->init (initable, cancellable, error);
@@ -287,15 +294,13 @@ finish_dump (GNetworkMonitorNetlink *nl)
 }
 
 static gboolean
-read_netlink_messages (GSocket      *socket,
-                       GIOCondition  condition,
-                       gpointer      user_data)
+read_netlink_messages (GNetworkMonitorNetlink  *nl,
+                       GError                 **error)
 {
-  GNetworkMonitorNetlink *nl = user_data;
   GInputVector iv;
   gssize len;
   gint flags;
-  GError *error = NULL;
+  GError *local_error = NULL;
   GSocketAddress *addr = NULL;
   struct nlmsghdr *msg;
   struct rtmsg *rtmsg;
@@ -310,11 +315,9 @@ read_netlink_messages (GSocket      *socket,
 
   flags = MSG_PEEK | MSG_TRUNC;
   len = g_socket_receive_message (nl->priv->sock, NULL, &iv, 1,
-                                  NULL, NULL, &flags, NULL, &error);
+                                  NULL, NULL, &flags, NULL, &local_error);
   if (len < 0)
     {
-      g_warning ("Error on netlink socket: %s", error->message);
-      g_clear_error (&error);
       retval = FALSE;
       goto done;
     }
@@ -322,19 +325,15 @@ read_netlink_messages (GSocket      *socket,
   iv.buffer = g_malloc (len);
   iv.size = len;
   len = g_socket_receive_message (nl->priv->sock, &addr, &iv, 1,
-                                  NULL, NULL, NULL, NULL, &error);
+                                  NULL, NULL, NULL, NULL, &local_error);
   if (len < 0)
     {
-      g_warning ("Error on netlink socket: %s", error->message);
-      g_clear_error (&error);
       retval = FALSE;
       goto done;
     }
 
-  if (!g_socket_address_to_native (addr, &source_sockaddr, sizeof (source_sockaddr), &error))
+  if (!g_socket_address_to_native (addr, &source_sockaddr, sizeof (source_sockaddr), &local_error))
     {
-      g_warning ("Error on netlink socket: %s", error->message);
-      g_clear_error (&error);
       retval = FALSE;
       goto done;
     }
@@ -348,7 +347,10 @@ read_netlink_messages (GSocket      *socket,
     {
       if (!NLMSG_OK (msg, (size_t) len))
         {
-          g_warning ("netlink message was truncated; shouldn't happen...");
+          g_set_error_literal (&local_error,
+                               G_IO_ERROR,
+                               G_IO_ERROR_PARTIAL_INPUT,
+                               "netlink message was truncated; shouldn't happen...");
           retval = FALSE;
           goto done;
         }
@@ -409,13 +411,21 @@ read_netlink_messages (GSocket      *socket,
           {
             struct nlmsgerr *e = NLMSG_DATA (msg);
 
-            g_warning ("netlink error: %s", g_strerror (-e->error));
+            g_set_error (&local_error,
+                         G_IO_ERROR,
+                         g_io_error_from_errno (-e->error),
+                         "netlink error: %s",
+                         g_strerror (-e->error));
           }
           retval = FALSE;
           goto done;
 
         default:
-          g_warning ("unexpected netlink message %d", msg->nlmsg_type);
+          g_set_error (&local_error,
+                       G_IO_ERROR,
+                       G_IO_ERROR_INVALID_DATA,
+                       "unexpected netlink message %d",
+                       msg->nlmsg_type);
           retval = FALSE;
           goto done;
         }
@@ -427,6 +437,10 @@ read_netlink_messages (GSocket      *socket,
 
   if (!retval && nl->priv->dump_networks)
     finish_dump (nl);
+
+  if (local_error)
+    g_propagate_prefixed_error (error, local_error, "Error on netlink socket: ");
+
   return retval;
 }
 
@@ -459,6 +473,24 @@ g_network_monitor_netlink_finalize (GObject *object)
   G_OBJECT_CLASS (g_network_monitor_netlink_parent_class)->finalize (object);
 }
 
+static gboolean
+read_netlink_messages_callback (GSocket      *socket,
+                                GIOCondition  condition,
+                                gpointer      user_data)
+{
+  GError *error = NULL;
+  GNetworkMonitorNetlink *nl = G_NETWORK_MONITOR_NETLINK (user_data);
+
+  if (!read_netlink_messages (nl, &error))
+    {
+      g_warning ("Error reading netlink message: %s", error->message);
+      g_clear_error (&error);
+      return FALSE;
+    }
+
+  return TRUE;
+}
+
 static void
 g_network_monitor_netlink_class_init (GNetworkMonitorNetlinkClass *nl_class)
 {