Look the expected checksum up instead of carrying it in the frame

probe.go

@@ -156,8 +156,7 @@ func (p *probeSender) run(done *atomic.Bool, startTx <-chan struct{}) {
 			}
 		}
 
-		putHeader(buf, probePattern, probeStream, seq, probeSize-minFrame,
-			p.spec.crcFor[probePattern][probeSize])
+		putHeader(buf, probePattern, probeStream, seq, probeSize-minFrame)
 		err := unix.Send(p.fd, buf, 0)
 		// The sequence advances even when a probe fails, so a stale receive half
 		// can never be paired with a later probe that reused its number.