[viosock]: Take care of recv requests stucks after socket shutdown

When an other end (peer) of the socket reports a shutdown, the recv request queue is not processed. This means that some recv calls may get stuck forever. This commit changes the behavior -- when a shutdown from its peer is received, the recv queue gets processed and all requests that would get stuck are completed with STATUS_SUCCESS (which usually ends in receiving zero bytes).

Signed-off-by: Martin Drab <[email protected]>

viosock/sys/Rx.c

@@ -1383,7 +1383,21 @@ VIOSockReadDequeueCb(
         }
         else
         {
-            bRequeue = TRUE;
+            // The socket is connected, however, it might
+            // receive a shutdown notification from the other end.
+            // In such a case, we need to complete the recv request with success,
+            // possibly reporting zero data received. If the shutdown is here,
+            // the request must not be requeued since that may cause it being
+            // in the queue forever.
+            status = VIOSockStateValidate(pSocket, FALSE);
+            if (!NT_SUCCESS(status))
+            {
+                bStop = TRUE;
+                if (status == STATUS_LOCAL_DISCONNECT ||
+                    status == STATUS_REMOTE_DISCONNECT)
+                    status = STATUS_SUCCESS;
+            }
+            else bRequeue = TRUE;
         }
     }
 

viosock/sys/Socket.c

@@ -1553,9 +1553,19 @@ VIOSockShutdownFromPeer(
     pSocket->PeerShutdown |= uFlags;
     bRes = (pSocket->PeerShutdown & VIRTIO_VSOCK_SHUTDOWN_MASK) == VIRTIO_VSOCK_SHUTDOWN_MASK;
     WdfSpinLockRelease(pSocket->StateLock);
+    if (uDrain & VIRTIO_VSOCK_SHUTDOWN_SEND)
+    {
+        // Let's empty the recv() request queue. We need to
+        // complete pending requests for which there are no
+        // data. SInce VIOSockReadProcessDequeueCb may process
+        // one such request per call, the loop is needed.
+        //
+        // New recv() requests should not be an issue since they
+        // get removed by queue's Ready Notify callback.
+        while ((WdfIoQueueGetState(pSocket->ReadQueue, NULL, NULL) & WdfIoQueueNoRequests) == 0)
+            VIOSockReadProcessDequeueCb(pSocket);
+    }
 
-//     if (uDrain & VIRTIO_VSOCK_SHUTDOWN_SEND)
-//         VIOSockReadDequeueCb(pSocket, WDF_NO_HANDLE);
 //     if (uDrain & VIRTIO_VSOCK_SHUTDOWN_RCV)
 //     {
 //         //TODO: dequeue requests for current socket only