code: func (d *Dialer) rawConnDial(ctx context.Context, raddr ma.Multiaddr, remote peer.ID) (transport.Conn, error) {
  	if strings.HasPrefix(raddr.String(), "/ip4/0.0.0.0") {
  		log.Event(ctx, "connDialZeroAddr", lgbl.Dial("conn", d.LocalPeer, remote, nil, raddr))
  		return nil, fmt.Errorf("Attempted to connect to zero address: %s", raddr)
  	}
  
  	sd := d.subDialerForAddr(raddr)
  	if sd == nil {
  		return nil, fmt.Errorf("no dialer for %s", raddr)
  	}
  
  	return sd.DialContext(ctx, raddr)
  }
docs: // rawConnDial dials the underlying net.Conn + manet.Conns