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
protected final RecoveryFilesDetails fileDetails;
        public static final long UNKNOWN = -1L;
        private long sourceThrottlingInNanos = UNKNOWN;
        private long targetThrottleTimeInNanos = UNKNOWN;
        public Index() {
            this(new RecoveryFilesDetails());
        }
        public Index(RecoveryFilesDetails recoveryFilesDetails) {
            this.fileDetails = recoveryFilesDetails;
        }
        public Index(StreamInput in) throws IOException {
            super(in);
            fileDetails = new RecoveryFilesDetails(in);
            sourceThrottlingInNanos = in.readLong();
            targetThrottleTimeInNanos = in.readLong();
        }
        @Override
        public synchronized void writeTo(StreamOutput out) throws IOException {
            super.writeTo(out);
            fileDetails.writeTo(out);