rxrpc: rxperf: Fix missing decoding of terminal magic cookie

The rxperf RPCs seem to have a magic cookie at the end of the request that
was failing to be taken account of by the unmarshalling of the request.
Fix the rxperf code to expect this.

Fixes: 75bfdbf ("rxrpc: Implement an in-kernel rxperf server for testing purposes")
Signed-off-by: David Howells <[email protected]>
cc: Marc Dionne <[email protected]>
cc: Simon Horman <[email protected]>
cc: [email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: dhowells

net/rxrpc/rxperf.c

@@ -478,6 +478,18 @@ static int rxperf_deliver_request(struct rxperf_call *call)
 		call->unmarshal++;
 		fallthrough;
 	case 2:
+		ret = rxperf_extract_data(call, true);
+		if (ret < 0)
+			return ret;
+
+		/* Deal with the terminal magic cookie. */
+		call->iov_len = 4;
+		call->kvec[0].iov_len	= call->iov_len;
+		call->kvec[0].iov_base	= call->tmp;
+		iov_iter_kvec(&call->iter, READ, call->kvec, 1, call->iov_len);
+		call->unmarshal++;
+		fallthrough;
+	case 3:
 		ret = rxperf_extract_data(call, false);
 		if (ret < 0)
 			return ret;