Merge pull request #5248 from joostjager/concurrent-onion

htlcswitch: concurrent onion decoding

htlcswitch/hop/iterator.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"sync"
 
 	"github.com/btcsuite/btcd/btcec"
 	sphinx "github.com/lightningnetwork/lightning-onion"
@@ -251,9 +252,8 @@ func (p *OnionProcessor) DecodeHopIterators(id []byte,
 
 	tx := p.router.BeginTxn(id, batchSize)
 
-	for i, req := range reqs {
-		onionPkt := &onionPkts[i]
-		resp := &resps[i]
+	decode := func(seqNum uint16, onionPkt *sphinx.OnionPacket,
+		req DecodeHopIteratorRequest) lnwire.FailCode {
 
 		err := onionPkt.Decode(req.OnionReader)
 		switch err {
@@ -261,45 +261,55 @@ func (p *OnionProcessor) DecodeHopIterators(id []byte,
 			// success
 
 		case sphinx.ErrInvalidOnionVersion:
-			resp.FailCode = lnwire.CodeInvalidOnionVersion
-			continue
+			return lnwire.CodeInvalidOnionVersion
 
 		case sphinx.ErrInvalidOnionKey:
-			resp.FailCode = lnwire.CodeInvalidOnionKey
-			continue
+			return lnwire.CodeInvalidOnionKey
 
 		default:
 			log.Errorf("unable to decode onion packet: %v", err)
-			resp.FailCode = lnwire.CodeInvalidOnionKey
-			continue
+			return lnwire.CodeInvalidOnionKey
 		}
 
 		err = tx.ProcessOnionPacket(
-			uint16(i), onionPkt, req.RHash, req.IncomingCltv,
+			seqNum, onionPkt, req.RHash, req.IncomingCltv,
 		)
 		switch err {
 		case nil:
 			// success
+			return lnwire.CodeNone
 
 		case sphinx.ErrInvalidOnionVersion:
-			resp.FailCode = lnwire.CodeInvalidOnionVersion
-			continue
+			return lnwire.CodeInvalidOnionVersion
 
 		case sphinx.ErrInvalidOnionHMAC:
-			resp.FailCode = lnwire.CodeInvalidOnionHmac
-			continue
+			return lnwire.CodeInvalidOnionHmac
 
 		case sphinx.ErrInvalidOnionKey:
-			resp.FailCode = lnwire.CodeInvalidOnionKey
-			continue
+			return lnwire.CodeInvalidOnionKey
 
 		default:
 			log.Errorf("unable to process onion packet: %v", err)
-			resp.FailCode = lnwire.CodeInvalidOnionKey
-			continue
+			return lnwire.CodeInvalidOnionKey
 		}
 	}
 
+	// Execute cpu-heavy onion decoding in parallel.
+	var wg sync.WaitGroup
+	for i := range reqs {
+		wg.Add(1)
+		go func(seqNum uint16) {
+			defer wg.Done()
+
+			onionPkt := &onionPkts[seqNum]
+
+			resps[seqNum].FailCode = decode(
+				seqNum, onionPkt, reqs[seqNum],
+			)
+		}(uint16(i))
+	}
+	wg.Wait()
+
 	// With that batch created, we will now attempt to write the shared
 	// secrets to disk. This operation will returns the set of indices that
 	// were detected as replays, and the computed sphinx packets for all