fix: add header range mix up check (#273)

Fixes #224

Author: varun-doshi

interface.go

@@ -56,6 +56,9 @@ var (
 	// ErrHeadersLimitExceeded is returned when ExchangeServer receives header request for more
 	// than maxRequestSize headers.
 	ErrHeadersLimitExceeded = errors.New("header/p2p: header limit per 1 request exceeded")
+
+	// ErrRangeMixUp is returned when `from` >= `to`.
+	ErrRangeMixUp = errors.New("header/p2p: `from` must be less than `to`")
 )
 
 // Store encompasses the behavior necessary to store and retrieve Headers

p2p/server.go

@@ -203,6 +203,10 @@ func (serv *ExchangeServer[H]) handleRangeRequest(
 	ctx context.Context,
 	from, to uint64,
 ) ([]H, error) {
+	if from >= to {
+		return nil, header.ErrRangeMixUp
+	}
+
 	if from == uint64(0) {
 		return serv.handleHeadRequest(ctx)
 	}