Function resolveTCPAddrs

tcpdialer.go:512–550

(addr string, dualStack bool, resolver Resolver, deadline time.Time)

}

func resolveTCPAddrs(addr string, dualStack bool, resolver Resolver, deadline time.Time) ([]net.TCPAddr, error) {
	host, portS, err := net.SplitHostPort(addr)
	if err != nil {
		return nil, err
	}
	port, err := strconv.Atoi(portS)
	if err != nil {
		return nil, err
	}

	if resolver == nil {
		resolver = net.DefaultResolver
	}

	ctx, cancel := context.WithDeadline(context.Background(), deadline)
	defer cancel()
	ipaddrs, err := resolver.LookupIPAddr(ctx, host)
	if err != nil {
		return nil, err
	}

	n := len(ipaddrs)
	addrs := make([]net.TCPAddr, 0, n)
	for i := range n {
		ip := ipaddrs[i]
		if !dualStack && ip.IP.To4() == nil {
			continue
		}
		addrs = append(addrs, net.TCPAddr{
			IP:   ip.IP,
			Port: port,
			Zone: ip.Zone,
		})
	}
	if len(addrs) == 0 {
		return nil, errNoDNSEntries
	}
	return addrs, nil
}

var errNoDNSEntries = errors.New("couldn't find DNS entries for the given domain. Try using DialDualStack")