60.9.4.131 无法访问 504 Gateway Time-out
$ dig v2ex.assets.uxengine.net @114.114.114.114 +short |\
grep -oE '\b([0-9]{1,3}\.){3}[0-9]{1,3}\b' |\
xargs -I{} curl https://v2ex.assets.uxengine.net --verbose --resolve v2ex.assets.uxengine.net:443:{}
* Added v2ex.assets.uxengine.net:443:60.9.4.131 to DNS cache
* Rebuilt URL to: https://v2ex.assets.uxengine.net/
* Hostname v2ex.assets.uxengine.net was found in DNS cache
* Trying 60.9.4.131...
* TCP_NODELAY set
* Connected to v2ex.assets.uxengine.net (60.9.4.131) port 443 (#0)
* TLS 1.2 connection using TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
* Server certificate: v2ex.co
* Server certificate: Let's Encrypt Authority X3
* Server certificate: DST Root CA X3
> GET / HTTP/1.1
> Host: v2ex.assets.uxengine.net
> User-Agent: curl/7.54.0
> Accept: */*
>
< HTTP/1.1 504 Gateway Time-out
< Server: nginx/1.15.8
< Date: Fri, 28 Dec 2018 18:42:56 GMT
< Content-Type: text/html
< Content-Length: 167
< Connection: keep-alive
< X-ORCA-Accelerator: MISS from k01.uni.gan01.cn.krill.zenlogic.net
< X-Cache: MISS from k01.uni.gan01.cn.krill.zenlogic.net
<
<html>
<head><title>504 Gateway Time-out</title></head>
<body>
<center><h1>504 Gateway Time-out</h1></center>
<hr><center>nginx/1.15.8</center>
</body>
</html>
* Connection #0 to host v2ex.assets.uxengine.net left intact
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