docmirror/dev-sidecar · warning

----- ${action}: ${hostname}, dns returned invalid ip

Error message

----- ${action}: ${hostname}, dns returned invalid ip 

What it means

The custom lookup function created by createLookupFunc asks the configured DNS for the hostname. If the DNS result is non-null, differs from the hostname, but is not a valid IP address (isValidIpAddress fails), the value is treated as garbage: a warning is logged and the lookup falls back to Node's default DNS for that request, so resolution still succeeds.

Source

Thrown at packages/mitmproxy/src/lib/proxy/mitmproxy/dnsLookup.js:109

      dns.lookup(hostname, { ipChecker, family }).then((ip) => {
        if (ip !== hostname && isValidIpAddress(ip)) {
          const addressFamily = getAddressFamily(ip)
          if (isDnsIntercept) {
            isDnsIntercept.dns = dns
            isDnsIntercept.hostname = hostname
            isDnsIntercept.ip = ip
            if (tester) isDnsIntercept.tester = tester
          }
          log.info(`----- ${action}: ${hostname}, use ip from dns '${dns.dnsName}': ${ip}(family: ${addressFamily})${target} -----`)
          if (res) {
            const dnsLabel = dns.dnsName === '预设IP' ? 'PreSet' : safeHeaderValue(dns.dnsName)
            res.setHeader('DS-DNS-Lookup', `DNS: ${ip} (IPv${addressFamily}) ${dnsLabel}`)
          }
          respondLookup(callback, ip, addressFamily, all)
        } else {
          // 使用默认dns
          if (ip != null && ip !== hostname && !isValidIpAddress(ip)) {
            log.warn(`----- ${action}: ${hostname}, dns returned invalid ip '${ip}'${target}, fallback to default DNS`)
          }
          log.info(`----- ${action}: ${hostname}, use default DNS: ${hostname}${target}, options:`, options, ', dns:', dns)
          defaultDns.lookup(hostname, options, callback)
        }
      }).catch((err) => {
        log.error(`----- ${action}: ${hostname}, dns lookup error${target}, options:`, options, `, error:`, err)
        defaultDns.lookup(hostname, options, callback)
      })
    }
  },
}

View on GitHub (pinned to 7710cd56cc)

Solutions

1. Inspect the DNS/ip list for the offending hostname and correct entries to be plain IPv4/IPv6 literals.
2. Remove the bad preset ip entry so the request uses default or another DNS backend.
3. Reset the DNS config to shipped defaults and re-apply your customizations one at a time to find the invalid value.
4. No action strictly required — the code already falls back to default DNS; fix the config to stop losing the speed/availability benefits of custom DNS.

Example fix

// before (preset ips)
["github.com", "140.82.112.3"]
// after
["140.82.112.3", "140.82.113.4"]

const bad = presetIps.filter(ip => !/^(\d{1,3}(\.\d{1,3}){3}|[0-9a-fA-F:]+)$/.test(ip))
if (bad.length) console.error('remove invalid ips:', bad)

const isValidIpAddress = (s) => typeof s === 'string' && (/^(\d{1,3}\.){3}\d{1,3}$/.test(s) || s.includes(':'))

When it happens

Trigger: A DNS module (preset ip list, DoH provider, custom dnsMap entry) returns a string that is not an IPv4/IPv6 literal — e.g. a preset list containing a domain name, a truncated/annotated IP, or DoH answer data in unexpected format.

Common situations: Hand-edited pre-set ip files where someone put hostnames or 'ip:port' strings; third-party DoH services returning CNAME-formatted data handled incorrectly; corrupted user config under ~/.dev-sidecar.

Related errors

• 域名 ${rOptions.hostname} 在dns中未配置，但使用了 sni: ${rOptions.server
• FreeEye runtime config is required.
• 无效的代理 IP 地址: ${ip}
• 无效的代理端口号: ${port}
• Unknown type DNS: ${server}, provider: ${provider}

AI-assisted analysis of docmirror/dev-sidecar@7710cd56cc (2026-08-31). Data as JSON: /api/errors/010969f42220ea4a. Report an issue: GitHub.