simple fetchers (#1492)

* network: disable shouldNOTRequestAgain
* vendor singleflight
* network: disable shouldNOTRequestAgain
* network, storage: fix tests
* network/storage: remove HopCount and SkipCheck
* network/stream: use localstore when providing chunks a node has offered
* storage: refactor lnetstore
* storage: rename FetcherItem to Fetcher
* storage/feed: no distinction between catastrophic err or chunk not found
* network/stream: remove TestDeliveryFromNodes, as FindPeer is changed, and Swarm connectivity is not a chain
* network/stream: fixed intervals tests
* swarm: fixes for linter
* storage: use LRU cache for fetchers
* network, storage: better godoc
* storage/netstore: explicit errors
* storage/feed/lookup: Clarify ReadFunc expected return error values
* storage: address comments by elad

network/stream/messages.go

@@ -225,9 +225,14 @@ func (p *Peer) handleOfferedHashesMsg(ctx context.Context, req *OfferedHashesMsg
 	for i := 0; i < lenHashes; i += HashSize {
 		hash := hashes[i : i+HashSize]
 
-		if wait := c.NeedData(ctx, hash); wait != nil {
+		log.Trace("checking offered hash", "ref", fmt.Sprintf("%x", hash))
+
+		if _, wait := c.NeedData(ctx, hash); wait != nil {
 			ctr++
+
+			// set the bit, so create a request
 			want.Set(i/HashSize, true)
+			log.Trace("need data", "ref", fmt.Sprintf("%x", hash), "request", true)
 
 			// measure how long it takes before we mark chunks for retrieval, and actually send the request
 			if !wantDelaySet {