[Spice-devel] [PATCH 0.8 7/9] server: hookup agent-msg-filter discard-all functionality

[Hans de Goede]

This ensures that if the client or agent connects to the client-agent
"tunnel" while the other side is halfway through sending a multi part
message, the rest of the message gets discarded, and the connecting
party starts getting data at the beginning of the next message.
---
 server/reds.c |   56 +++++++++++++++++++++++---------------------------------
 1 files changed, 23 insertions(+), 33 deletions(-)

diff --git a/server/reds.c b/server/reds.c
index 40b6bb0..05f52a0 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -205,8 +205,6 @@ typedef struct VDIPortState {
     AgentMsgFilter read_filter;
 
     VDIChunkHeader vdi_chunk_header;
-
-    int client_agent_started;
 } VDIPortState;
 
 typedef struct InputsState {
@@ -713,8 +711,12 @@ static void reds_reset_vdp()
         ring_add(&state->read_bufs, &state->current_read_buf->link);
         state->current_read_buf = NULL;
     }
-    agent_msg_filter_init(&state->read_filter, agent_copypaste, FALSE);
-    state->client_agent_started = FALSE;
+    /* Reset read filter to start with clean state when the agent reconnects */
+    agent_msg_filter_init(&state->read_filter, agent_copypaste, TRUE);
+    /* Throw away pending chunks from the current (if any) and future
+       messages written by the client */
+    state->write_filter.result = AGENT_MSG_FILTER_DISCARD;
+    state->write_filter.discard_all = TRUE;
 }
 
 static void reds_reset_outgoing()
@@ -744,8 +746,13 @@ static void reds_disconnect()
     red_printf("");
     reds->disconnecting = TRUE;
     reds_reset_outgoing();
+    /* Reset write filter to start with clean state on client reconnect */
     agent_msg_filter_init(&reds->agent_state.write_filter, agent_copypaste,
-                          FALSE);
+                          TRUE);
+    /* Throw away pending chunks from the current (if any) and future
+       messages read from the agent */
+    reds->agent_state.read_filter.result = AGENT_MSG_FILTER_DISCARD;
+    reds->agent_state.read_filter.discard_all = TRUE;
 
     if (reds->agent_state.connected) {
         SpiceCharDeviceInterface *sif;
@@ -754,7 +761,6 @@ static void reds_disconnect()
         if (sif->state) {
             sif->state(vdagent, reds->agent_state.connected);
         }
-        reds->agent_state.client_agent_started = FALSE;
     }
 
     reds_shatdown_channels();
@@ -1239,17 +1245,10 @@ static void dispatch_vdi_port_data(int port, VDIReadBuf *buf)
             reds_agent_remove();
             return;
         }
-
-        if (reds->agent_state.connected) {
-            item = new_out_item(SPICE_MSG_MAIN_AGENT_DATA);
-
-            spice_marshaller_add_ref_full(item->m, buf->data, buf->len,
-                                          vdi_read_buf_release, buf);
-            reds_push_pipe_item(item);
-        } else {
-            red_printf("throwing away, no client: %d", buf->len);
-            vdi_read_buf_release(buf->data, buf);
-        }
+        item = new_out_item(SPICE_MSG_MAIN_AGENT_DATA);
+        spice_marshaller_add_ref_full(item->m, buf->data, buf->len,
+                                      vdi_read_buf_release, buf);
+        reds_push_pipe_item(item);
         break;
     }
     case VDP_SERVER_PORT:
@@ -1436,7 +1435,7 @@ static void main_channel_push_migrate_data_item()
     data->ping_id = reds->ping_id;
 
     data->agent_connected = !!state->connected;
-    data->client_agent_started = state->client_agent_started;
+    data->client_agent_started = !state->write_filter.discard_all;
     data->num_client_tokens = state->num_client_tokens;
     data->send_tokens = ~0;
 
@@ -1676,7 +1675,7 @@ static void main_channel_recive_migrate_data(MainMigrateData *data, uint8_t *end
         return;
     }
 
-    state->client_agent_started = data->client_agent_started;
+    state->write_filter.discard_all = !data->client_agent_started;
 
     pos = (uint8_t *)(data + 1);
 
@@ -1698,7 +1697,7 @@ static void reds_main_handle_message(void *opaque, size_t size, uint32_t type, v
         if (!reds->peer) {
             return;
         }
-        reds->agent_state.client_agent_started = TRUE;
+        reds->agent_state.write_filter.discard_all = FALSE;
         break;
     case SPICE_MSGC_MAIN_AGENT_DATA: {
         RingItem *ring_item;
@@ -1724,17 +1723,6 @@ static void reds_main_handle_message(void *opaque, size_t size, uint32_t type, v
             return;
         }
 
-        if (!vdagent) {
-            add_token();
-            break;
-        }
-
-        if (!reds->agent_state.client_agent_started) {
-            red_printf("SPICE_MSGC_MAIN_AGENT_DATA race");
-            add_token();
-            break;
-        }
-
         if (!(ring_item = ring_get_head(&reds->agent_state.external_bufs))) {
             red_printf("no agent free bufs");
             reds_disconnect();
@@ -2088,6 +2076,7 @@ static void reds_handle_main_link(RedLinkInfo *link)
         SpiceCharDeviceInterface *sif;
         sif = SPICE_CONTAINEROF(vdagent->base.sif, SpiceCharDeviceInterface, base);
         reds->agent_state.connected = 1;
+        reds->agent_state.read_filter.discard_all = FALSE;
         if (sif->state) {
             sif->state(vdagent, reds->agent_state.connected);
         }
@@ -3497,6 +3486,7 @@ static void attach_to_red_agent(SpiceCharDeviceInstance *sin)
     }
     sif = SPICE_CONTAINEROF(vdagent->base.sif, SpiceCharDeviceInterface, base);
     state->connected = 1;
+    state->read_filter.discard_all = FALSE;
     if (sif->state) {
         sif->state(vdagent, state->connected);
     }
@@ -3751,8 +3741,8 @@ static void init_vd_agent_resources()
     ring_init(&state->internal_bufs);
     ring_init(&state->write_queue);
     ring_init(&state->read_bufs);
-    agent_msg_filter_init(&state->write_filter, agent_copypaste, FALSE);
-    agent_msg_filter_init(&state->read_filter, agent_copypaste, FALSE);
+    agent_msg_filter_init(&state->write_filter, agent_copypaste, TRUE);
+    agent_msg_filter_init(&state->read_filter, agent_copypaste, TRUE);
 
     state->read_state = VDI_PORT_READ_STATE_READ_HADER;
     state->recive_pos = (uint8_t *)&state->vdi_chunk_header;
-- 
1.7.4.2