为什么Twitter的t.co出现在Referer中，但是没有URL缩短器呢？ [英] Why Twitter's t.co shows up in Referer, but no URL shorteners ever do?
问题描述
我注意到我的<$ c中有一大堆 Referer 链接，例如 t.co/oPQO7Xdz $ c> access_log 文件，但没有出现其他网址缩短程序。为什么？
I've noticed a whole bunch of Referer links like t.co/oPQO7Xdz in my access_log files, but no other URL shorteners ever show up. Why?
推荐答案
URL缩短器永远不会显示，因为 HTTP 301永久移动等 HTTP中的重定向不是为了影响 Referer HTTP请求标头（显然，即使标题是空白的，也可能是因为它会导致行为不一致的事实。
The URL shorteners never show up because HTTP 301 Moved Permanently et al redirects in HTTP are not designed to influence the Referer HTTP Request Header (apparently, not even if the header is blank, potentially due to the fact that it'll cause inconsistency in behaviour otherwise).
然而，Twitter不会发出 301永久移动 重定向code> t.co 服务，如果它看到它认为是热门桌面或移动用户代理。由于重定向因此在HTTP堆栈之外完成，因此后续全新HTTP请求中的 Referer 字段将被组成以包含负责的先前HTML页面。重定向，导致 t.co 条目出现在 access_log 。
However, Twitter does not issue 301 Moved Permanently redirects with its t.co service if it sees what it deems is a popular desktop or mobile User-Agent. As the redirect is thus done outside of the HTTP stack, the Referer field in the subsequent brand-new HTTP Request would then be composed to include the prior HTML page that was responsible for the redirection, causing a t.co entry to appear in access_log.
% curl -v -A"iPhone;" t.co/oPQO7Xdz
* About to connect() to t.co port 80 (#0)
* Trying 104.244.42.5...
* connected
* Connected to t.co (104.244.42.5) port 80 (#0)
> GET /oPQO7Xdz HTTP/1.1
> User-Agent: iPhone;
> Host: t.co
> Accept: */*
>
< HTTP/1.1 200 OK
< cache-control: private,max-age=300
< content-length: 258
< content-security-policy: referrer always;
< content-type: text/html; charset=utf-8
< date: Thu, 07 Jul 2016 05:24:16 GMT
< expires: Thu, 07 Jul 2016 05:29:16 GMT
< server: tsa_o
< set-cookie: muc=1f43e292-e319-4818-ba81-f12d16e5b629; Expires=Tue, 19 Jun 2018 05:24:16 UTC; Domain=t.co
< x-connection-hash: 0dc5a2a6a7e83ac2d7fb207eb0cedf84
< x-response-time: 115
< x-xss-protection: 1; mode=block
<
* Connection #0 to host t.co left intact
<head><meta name="referrer" content="always"><noscript><META http-equiv="refresh" content="0;URL=http://mdoc.su/n/curl"></noscript><title>http://mdoc.su/n/curl</title></head><script>window.opener = null; location.replace("http:\/\/mdoc.su\/n\/curl")</script>* Closing connection #0
将此情况与其他情况进行比较（这是大多数其他网址缩短程序重定向的唯一方式，这将保留 Referer ：
Compare this to what were to occur otherwise (and which is the only way that most other URL shorteners redirect, which would preserve whichever Referer appears when the HTTP request first hits the HTTP stack of the browser):
% curl -v t.co/oPQO7Xdz
* About to connect() to t.co port 80 (#0)
* Trying 104.244.42.69...
* connected
* Connected to t.co (104.244.42.69) port 80 (#0)
> GET /oPQO7Xdz HTTP/1.1
> User-Agent: curl/7.26.0
> Host: t.co
> Accept: */*
>
< HTTP/1.1 301 Moved Permanently
< cache-control: private,max-age=300
< content-length: 0
< date: Thu, 07 Jul 2016 05:24:40 GMT
< expires: Thu, 07 Jul 2016 05:29:40 GMT
< location: http://mdoc.su/n/curl
< server: tsa_o
< set-cookie: muc=2c727b50-311f-4043-9861-9f703996a8a8; Expires=Tue, 19 Jun 2018 05:24:40 UTC; Domain=t.co
< x-connection-hash: 5583cc49ddbcefe8fac9ba392ca868fd
< x-response-time: 103
<
* Connection #0 to host t.co left intact
* Closing connection #0
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