We saw a case where the recovery stats reported `recovered_bytes` greater than `length_in_bytes` for one file:

```
GET /_recovery?detailed

200 OK
...
{
  "name": "_buk.fdt",
  "length_in_bytes": 26891307173,
  "reused": false,
  "recovered_in_bytes": 35324928266,
  "recovered_from_snapshot_in_bytes": 8433621093
}
...
```

NB `35324928266 == 26891307173 + 8433621093`

This causes Elasticsearch to compute a negative value for the reserved space on the target node of this recovery, which prevents stats APIs from working. This appears to be caused by a network-level failure which triggers a retry without first cancelling an ongoing download of a different file with the same name from the snapshot repository.

---

### Workaround

Restart the target node to clear these stats.
server/src/main/java/org/elasticsearch/indices/recovery/RecoveryState.java
if (startNanoTime == 0) {
                return 0;
            }
            if (time >= 0) {
                return time;
            }
            return Math.max(0, TimeValue.nsecToMSec(System.nanoTime() - startNanoTime));
        }
        
        public synchronized long stopTime() {
            return stopTime;
        }
        public synchronized void stop() {
            assert stopTime == 0 : "already stopped";
            stopTime = Math.max(System.currentTimeMillis(), startTime);
            time = TimeValue.nsecToMSec(System.nanoTime() - startNanoTime);
            assert time >= 0;
        }
        public synchronized void reset() {
            startTime = 0;
            startNanoTime = 0;
            time = -1;
            stopTime = 0;
        }
        
        public long getStartNanoTime() {
            return startNanoTime;
        }
    }
    public static class VerifyIndex extends Timer implements ToXContentFragment, Writeable {