node.js dns.resolveAny返回空数组

Question

我正在使用dns.resolveAny函数来检查一些域的域名信息。

我发现奇怪的一件事是，对于某些域，nslookup命令不返回空数组，而dns.resolveAny返回空数组。

下面是一个例子：

// node.js version >= 9.2 is required

const dns = require('dns')

dns.resolveAny('www.ifshop.com.tw', (err, ret) => {
  if (err) {
      console.log(`err: ${err}`)
  } else {
      console.log(`ret: ${JSON.stringify(ret)}`)  // JSON.stringify(ret) == [] here
  }
})

resolveAny返回[]。但是nslookup成功地返回了www.ifshop.com.tw的CNAME记录。

> nslookup www.ifshop.com.tw
Server:     192.168.1.1
Address:    192.168.1.1#53

Non-authoritative answer:
www.ifshop.com.tw   canonical name = s1759.dname.91app.io.
s1759.dname.91app.io    canonical name = proxy.letssl.91app.io.
proxy.letssl.91app.io   canonical name = proxy-letssl-91app-io-196811564.ap-northeast-1.elb.amazonaws.com.
Name:   proxy-letssl-91app-io-196811564.ap-northeast-1.elb.amazonaws.com
Address: 54.178.248.57
Name:   proxy-letssl-91app-io-196811564.ap-northeast-1.elb.amazonaws.com
Address: 52.196.80.17

这一切为什么要发生？

这是resolveAny的错误吗？

或者是www.ifshop.com.tw的DNS配置有问题？

我还发现dns.resolveCname成功地返回了CNAME。

// node.js version >= 9.2 is required

const dns = require('dns')

dns.resolveCname('www.ifshop.com.tw', (err, ret) => {
  if (err) {
      console.log(`err: ${err}`)
  } else {
      console.log(`ret: ${JSON.stringify(ret)}`)
  }
})

这里，JSON.stringify(ret)等于["s1759.dname.91app.io"]。