fix: Uses more specific error for TLS task cancelled issue (#3174)

Author: maddeleine

quic/s2n-quic-core/src/crypto/tls/offload.rs

@@ -290,7 +290,7 @@ impl<S: tls::Session> tls::Session for OffloadSession<S> {
                 }
                 Err(_) => {
                     // For whatever reason the TLS task was cancelled. We cannot continue the handshake.
-                    return Poll::Ready(Err(transport::Error::from(tls::Error::HANDSHAKE_FAILURE)));
+                    return Poll::Ready(Err(TLS_TASK_CANCELLED));
                 }
             },
             Poll::Pending => (),
@@ -333,7 +333,7 @@ impl<S: tls::Session> tls::Session for OffloadSession<S> {
                 }
                 Err(_) => {
                     // For whatever reason the TLS task was cancelled. We cannot continue the handshake.
-                    return Poll::Ready(Err(transport::Error::from(tls::Error::HANDSHAKE_FAILURE)));
+                    return Poll::Ready(Err(TLS_TASK_CANCELLED));
                 }
             },
             Poll::Pending => (),
@@ -365,6 +365,9 @@ struct AllowedToSend {
 const SLICE_ERROR: crate::transport::Error =
     crate::transport::Error::INTERNAL_ERROR.with_reason("Slice is full");
 
+const TLS_TASK_CANCELLED: crate::transport::Error =
+    crate::transport::Error::INTERNAL_ERROR.with_reason("TLS task cancelled");
+
 #[derive(Debug)]
 struct RemoteContext<'a, Request, H> {
     send_to_quic: SendSlice<'a, Request>,