Fix router fuzz failure due to LengthLimitedReader

We recently switched the decode_msg macro in the router fuzz target from
reading from a Cursor to reading from a slice. This caused a failure because
the slice advances its pointer as it is being read from, so asserting that the
length of the slice is equal to the length of the message that was read no
longer works. Instead assert that the original fuzz data length is equal to
the length of the message that was read.

Author: valentinewallace

fuzz/src/router.rs

@@ -150,7 +150,8 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
 			let mut reader = &data[..];
 			match <$MsgType>::read_from_fixed_length_buffer(&mut reader) {
 				Ok(msg) => {
-					assert_eq!(reader.len(), $len);
+					// Check that we read the slice to the end
+					assert!(reader.is_empty());
 					msg
 				},
 				Err(e) => match e {