client: don't crash when agent is missing WAN support

If you try to connect to a linux guest with WAN options, SPICE window opens up
and is blank - it then fails with vdagent timeout message.  It should give a
warning that this is only applicable for windows guest and still connect to
guest.

It all starts in RedClient::handle_init
This function checks whether we have an agent or not, because if we have an
agent, there will be some kind of handshake to check both sides capabilities
before all the spice channels are created.

When there is no agent running, the startup process goes on with
SPICE_MSGC_MAIN_ATTACH_CHANNELS

When there is a windows agent running, VD_AGENT_ANNOUNCE_CAPABILITIES and
VD_AGENT_DISPLAY_CONFIG messages are sent to the agent, and when processing the
agent answer to the VD_AGENT_DISPLAY_CONFIG message,
SPICE_MSGC_MAIN_ATTACH_CHANNELS will be sent and the startup process will go
on.

However, when there is no agent running but --color-depth was used, handle_init
won't send the SPICE_MSGC_MAIN_ATTACH_CHANNELS message but will wait for the
agent handshake to proceed to its end, which won't happen, so it will timeout
waiting for agent answers.

Similarly, the linux agent handles VD_AGENT_ANNOUNCE_CAPABILITIES messages, but
it doesn't handle VD_AGENT_DISPLAY_CONFIG messages, so we'll never reach the
point where a SPICE_MSGC_MAIN_ATTACH_CHANNELS will be sent.

This commit fixes this in 2 places:
- unconditionnally send SPICE_MSGC_ATTACH_CHANNELS when no agent is running in
handle_init
- send SPICE_MSGC_MAIN_ATTACH_CHANNELS in
RedClient::on_agent_announce_capabilities if the agent doesn't have the
VD_AGENT_CAP_DISPLAY_CONFIG capability

This fixes RH bug #712938

1 files changed, 20 insertions, 8 deletions

diff --git a/client/red_client.cpp b/client/red_client.cpp
index 8918e4fc..67690e90 100644
--- a/client/red_client.cpp
+++ b/client/red_client.cpp
@@ -966,19 +966,20 @@ void RedClient::handle_init(RedPeer::InMessage* message)
         agent_start.num_tokens = ~0;
         _marshallers->msgc_main_agent_start(msg->marshaller(), &agent_start);
         post_message(msg);
-    }
-
-    if (_agent_connected) {
         send_agent_announce_capabilities(true);
         if (_auto_display_res) {
            send_agent_monitors_config();
         }
-    }
-
-    if (!_auto_display_res && _display_setting.is_empty()) {
-        post_message(new Message(SPICE_MSGC_MAIN_ATTACH_CHANNELS));
+        if (_auto_display_res || !_display_setting.is_empty()) {
+            _application.activate_interval_timer(*_agent_timer, AGENT_TIMEOUT);
+        } else {
+            post_message(new Message(SPICE_MSGC_MAIN_ATTACH_CHANNELS));
+        }
     } else {
-        _application.activate_interval_timer(*_agent_timer, AGENT_TIMEOUT);
+        if (_auto_display_res || !_display_setting.is_empty()) {
+            LOG_WARN("no agent running, display options have been ignored");
+        }
+        post_message(new Message(SPICE_MSGC_MAIN_ATTACH_CHANNELS));
     }
 }
 
@@ -1046,6 +1047,17 @@ void RedClient::on_agent_announce_capabilities(
         // not sending the color depth through send_agent_monitors_config, since
         // it applies only for attached screens.
         send_agent_display_config();
+    } else if (!_auto_display_res) {
+        /* some agents don't support monitors/displays agent messages, so
+         * we'll never reach on_agent_reply which sends this
+         * ATTACH_CHANNELS message which is needed for client startup to go
+         * on.
+         */
+        if (!_display_setting.is_empty()) {
+            LOG_WARN("display options have been requested, but the agent doesn't support these options");
+        }
+        post_message(new Message(SPICE_MSGC_MAIN_ATTACH_CHANNELS));
+        _application.deactivate_interval_timer(*_agent_timer);
     }
 }