couldn't find dns entries for the given domain: try using du

Error message

couldn't find dns entries for the given domain: try using dual-stack dialing

What it means

errNoDNSEntries is returned by resolveTCPAddrs when DNS resolution for the dial target completes but yields an empty address list. The library appends the hint 'try using dual-stack dialing' because the most common cause is dialing with a network string (e.g. tcp4/tcp6) that excludes the address family the domain actually resolves to (e.g. an IPv6-only domain resolved while forcing tcp4).

Source

Thrown at tcpdialer.go:552

	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 dual-stack dialing")

View on GitHub (pinned to c96f600972)

Solutions

Change the dial network to 'tcp' (dual-stack) so both A and AAAA results are accepted
Verify DNS records exist: run `dig A <host>` and `dig AAAA <host>` and fix DNS if empty
Fix the hostname typo or use the correct domain
If you must pin tcp4/tcp6, confirm the domain has records of that family before dialing

Example fix

// before
conn, err := dialer.Dial("tcp4", "ipv6-only.example.com:443")
// after
conn, err := dialer.Dial("tcp", "ipv6-only.example.com:443")

Defensive patterns

Strategy: validation

Validate before calling

func canDial(host, network string) error {
  ips, err := net.LookupIP(host)
  if err != nil { return err }
  for _, ip := range ips {
    if network == "tcp4" && ip.To4() != nil { return nil }
    if network == "tcp6" && ip.To4() == nil { return nil }
    if network == "tcp" { return nil }
  }
  return fmt.Errorf("host %s has no addresses for network %s", host, network)
}

Type guard

func isDualStackSafe(network string) bool { return network == "tcp" }

Try / catch

addrs, err := dialer.Dial(network, addr)
if err != nil {
  if strings.Contains(err.Error(), "couldn't find dns entries") {
    addrs, err = dialer.Dial("tcp", addr) // retry dual-stack
  }
}

Prevention

Always prefer network "tcp" (dual-stack) unless you have a hard requirement
Pre-flight LookupIP and filter by family before choosing tcp4/tcp6
Monitor DNS zones so A/AAAA record removals are caught
Log the network string and resolved addresses on dial failure

When it happens

Trigger: Calling a TCP dialer with a network of 'tcp4' or 'tcp6' for a domain whose DNS records only contain the other address family, or a domain with no A/AAAA records at all; resolveTCPAddrs then produces len(addrs)==0 and returns errNoDNSEntries.

Common situations: Hardcoding network:'tcp4' for services that are IPv6-only; a domain whose AAAA/A records were just removed; split-horizon or filtered DNS returning no records inside containers/VPNs; typo'd hostname with no records.

Related errors

AI-assisted analysis of valyala/fasthttp@c96f600972 (2026-08-31). Data as JSON: /api/errors/14e2b313b5162dc9. Report an issue: GitHub.