bugfix: Fixed the downloader issue and extra genesis header response

Removed the unnessesary number checks in the queue, and in the handlers
for the get header by number request was sending an extra genesis header
which is not required.

Also simplified the logic of accepting the chain of headers in the queue

eth/downloader/queue.go

@@ -711,11 +711,12 @@ func (q *queue) DeliverHeaders(id string, headers []*types.Header, headerProcCh
 	// Ensure headers can be mapped onto the skeleton chain
 	targetTo := q.headerToPool[request.From+1]
 
+	var accepted bool
 	requiredHeaderFetch := request.From - targetTo
-	if targetTo != 0 {
+	if targetTo != 0 || common.NodeLocation.Context() == common.PRIME_CTX {
 		requiredHeaderFetch += 1
 	}
-	accepted := len(headers) == int(requiredHeaderFetch)
+	accepted = len(headers) == int(requiredHeaderFetch)
 
 	// reverse the array
 	for i, j := 0, len(headers)-1; i < j; i, j = i+1, j-1 {
@@ -736,19 +737,8 @@ func (q *queue) DeliverHeaders(id string, headers []*types.Header, headerProcCh
 
 	if accepted {
 		parentHash := headers[0].Hash()
-		for i, header := range headers[1:] {
+		for _, header := range headers[1:] {
 			hash := header.Hash()
-			var want uint64
-			if targetTo != 0 {
-				want = targetTo + 1 + uint64(i)
-			} else {
-				want = targetTo + 2 + uint64(i)
-			}
-			if header.Number().Uint64() != want {
-				logger.Warn("Header broke chain ordering", "number", header.Number(), "hash", hash, "expected", want)
-				accepted = false
-				break
-			}
 			if parentHash != header.ParentHash() {
 				logger.Warn("Header broke chain ancestry", "number", header.Number(), "hash", hash)
 				accepted = false

eth/protocols/eth/handlers.go

@@ -99,10 +99,6 @@ func answerGetBlockHeadersQuery(backend Backend, query *GetBlockHeadersPacket, p
 		// If the to number is reached stop the search
 		// By default the To is 0 and if its value is specified we need to stop
 		if query.To >= query.Origin.Number && query.Reverse {
-			if query.Origin.Number == 0 {
-				genesis := backend.Core().GetHeaderByNumber(0)
-				headers = append(headers, genesis)
-			}
 			break
 		}