inverted_index: sanity error (#12730)

my node had old and broken .ef file - i didn't know about it - until
found that GetAsOf used one `.ef` file and totally different `.v`
(because `.ef` returned some out-of-bound txNum).

addad post-validation to `ii.seekInFiles` method

erigon-lib/state/history.go

@@ -1150,7 +1150,10 @@ func (ht *HistoryRoTx) getFile(txNum uint64) (it visibleFile, ok bool) {
 func (ht *HistoryRoTx) historySeekInFiles(key []byte, txNum uint64) ([]byte, bool, error) {
 	// Files list of II and History is different
 	// it means II can't return index of file, but can return TxNum which History will use to find own file
-	ok, histTxNum := ht.iit.seekInFiles(key, txNum)
+	ok, histTxNum, err := ht.iit.seekInFiles(key, txNum)
+	if err != nil {
+		return nil, false, err
+	}
 	if !ok {
 		return nil, false, nil
 	}

erigon-lib/state/inverted_index.go

@@ -556,12 +556,12 @@ func (iit *InvertedIndexRoTx) statelessIdxReader(i int) *recsplit.IndexReader {
 	return r
 }
 
-func (iit *InvertedIndexRoTx) seekInFiles(key []byte, txNum uint64) (found bool, equalOrHigherTxNum uint64) {
+func (iit *InvertedIndexRoTx) seekInFiles(key []byte, txNum uint64) (found bool, equalOrHigherTxNum uint64, err error) {
 	if len(iit.files) == 0 {
-		return false, 0
+		return false, 0, nil
 	}
 	if iit.files[len(iit.files)-1].endTxNum <= txNum {
-		return false, 0
+		return false, 0, nil
 	}
 
 	hi, lo := iit.hashKey(key)
@@ -576,10 +576,10 @@ func (iit *InvertedIndexRoTx) seekInFiles(key []byte, txNum uint64) (found bool,
 		if ok && fromCache.requested <= txNum {
 			if txNum <= fromCache.found {
 				iit.seekInFilesCache.hit++
-				return true, fromCache.found
+				return true, fromCache.found, nil
 			} else if fromCache.found == 0 {
 				iit.seekInFilesCache.hit++
-				return false, 0
+				return false, 0, nil
 			}
 		}
 	}
@@ -603,17 +603,20 @@ func (iit *InvertedIndexRoTx) seekInFiles(key []byte, txNum uint64) (found bool,
 		equalOrHigherTxNum, found = eliasfano32.Seek(eliasVal, txNum)
 
 		if found {
+			if equalOrHigherTxNum < iit.files[i].startTxNum || equalOrHigherTxNum >= iit.files[i].endTxNum {
+				return false, equalOrHigherTxNum, fmt.Errorf("inverted_index(%s) at (%x, %d) returned value %d, but it out-of-bounds %d-%d. it may signal that .ef file is broke - can detect by `erigon seg integrity --check=InvertedIndex`, or re-download files", g.FileName(), key, txNum, iit.files[i].startTxNum, iit.files[i].endTxNum, equalOrHigherTxNum)
+			}
 			if iit.seekInFilesCache != nil {
 				iit.seekInFilesCache.Add(hi, iiSeekInFilesCacheItem{requested: txNum, found: equalOrHigherTxNum})
 			}
-			return true, equalOrHigherTxNum
+			return true, equalOrHigherTxNum, nil
 		}
 	}
 
 	if iit.seekInFilesCache != nil {
 		iit.seekInFilesCache.Add(hi, iiSeekInFilesCacheItem{requested: txNum, found: 0})
 	}
-	return false, 0
+	return false, 0, nil
 }
 
 // IdxRange - return range of txNums for given `key`