server/vdi_port (virtserial): always read data

We erronously ignored data from guest on the serial channel if no client is
connected. This leads to an assert when the guest writes a second time, since
there is still data unconsumed by us (the host).
Fix by reading data anyway, and discarding it after parsing (and reading) whole
messages from the guest.
Net affect is that any messages the agent sends while no client is connected
get discarded, but only full messages are discarded.
This fixes an abort if booting a winxp guest with vdagent without a connected
client.

1 files changed, 13 insertions, 6 deletions

diff --git a/server/reds.c b/server/reds.c
index 728778cf..c7181ee5 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -1213,11 +1213,16 @@ static void dispatch_vdi_port_data(int port, VDIReadBuf *buf)
 
     switch (port) {
     case VDP_CLIENT_PORT: {
-        item = new_out_item(SPICE_MSG_MAIN_AGENT_DATA);
+        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);
+            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);
+        }
         break;
     }
     case VDP_SERVER_PORT:
@@ -1254,13 +1259,15 @@ static int read_from_vdi_port(void)
     }
     inside_call = 1;
 
-    if (!reds->agent_state.connected || reds->mig_target) {
+    if (reds->mig_target || !vdagent) {
+        // discard data only if we are migrating or vdagent has not been
+        // initialized.
         inside_call = 0;
         return 0;
     }
 
     sif = SPICE_CONTAINEROF(vdagent->base.sif, SpiceCharDeviceInterface, base);
-    while (!quit_loop && reds->agent_state.connected) {
+    while (!quit_loop) {
         switch (state->read_state) {
         case VDI_PORT_READ_STATE_READ_HADER:
             n = sif->read(vdagent, state->recive_pos, state->recive_len);