code: func (p *peer) AsyncSendNewBlockHash(block *types.Block) {
  	select {
  	case p.queuedAnns <- block:
  		p.knownBlocks.Add(block.Hash())
  	default:
  		p.Log().Debug("Dropping block announcement", "number", block.NumberU64(), "hash", block.Hash())
  	}
  }
docs: // AsyncSendNewBlockHash queues the availability of a block for propagation to a
  // remote peer. If the peer's broadcast queue is full, the event is silently
  // dropped.