tbc: check block does not exist prior to inserting into blocksmissing…

… db (#382)

* Verify block does not exist prior to inserting into blocksmissing db

This is needed to support synthetic blockheader inserts in headers only
mode.

* Eat Has call on hash height as well

* Provide max requested BlockHeadersInsert

database/tbcd/level/level.go

@@ -1061,6 +1061,9 @@ func (l *ldb) BlockHeadersInsert(ctx context.Context, bhs *wire.MsgHeaders, batc
 	}
 	defer hhDiscard()
 
+	// blocks
+	blocksDB := l.rawPool[level.BlocksDB]
+
 	// retrieve best/canonical block header
 	bbh, err := bhsTx.Get([]byte(bhsCanonicalTipKey), nil)
 	if err != nil {
@@ -1111,12 +1114,23 @@ func (l *ldb) BlockHeadersInsert(ctx context.Context, bhs *wire.MsgHeaders, batc
 
 		// Store height_hash for future reference
 		hhKey := heightHashToKey(height, bhash[:])
-		hhBatch.Put(hhKey, []byte{}) // XXX nil?
+		ok, err := hhTx.Has(hhKey, nil)
+		if err != nil {
+			return tbcd.ITInvalid, nil, nil, 0,
+				fmt.Errorf("height hash has: %w", err)
+		} else if !ok {
+			hhBatch.Put(hhKey, []byte{})
+		}
 
 		// Insert a synthesized height_hash key that serves as an index
 		// to see which blocks are missing.
-		// XXX should we always insert or should we verify prior to insert?
-		bmBatch.Put(hhKey, []byte{})
+		ok, err = blocksDB.Has(hhKey)
+		if err != nil {
+			return tbcd.ITInvalid, nil, nil, 0,
+				fmt.Errorf("blocks has: %w", err)
+		} else if !ok {
+			bmBatch.Put(hhKey, []byte{})
+		}
 
 		// XXX reason about pre encoding. Due to the caller code being
 		// heavily reentrant the odds are not good that encoding would

service/tbc/tbc.go

@@ -1409,6 +1409,10 @@ func (s *Server) BlockInsert(ctx context.Context, blk *wire.MsgBlock) (int64, er
 	return s.db.BlockInsert(ctx, btcutil.NewBlock(blk))
 }
 
+func (s *Server) BlockHeadersInsert(ctx context.Context, headers *wire.MsgHeaders) (tbcd.InsertType, *tbcd.BlockHeader, *tbcd.BlockHeader, int, error) {
+	return s.db.BlockHeadersInsert(ctx, headers, nil)
+}
+
 func (s *Server) handleBlock(ctx context.Context, p *rawpeer.RawPeer, msg *wire.MsgBlock, raw []byte) error {
 	log.Tracef("handleBlock (%v)", p)
 	defer log.Tracef("handleBlock exit (%v)", p)