[1] [[要求]]に [CODE(HTTP)@en[[[CF-Connecting-IP:]]]] [[ヘッダー]]が既に含まれている場合、
[[CloudFlare]] の[[逆串]]が [CODE(HTTP)[[[403]]]] [[応答]]を返すようです。

[404] [CITE@en-US[How does CloudFlare handle HTTP Request headers? – CloudFlare Support]]
( ([TIME[2014-05-09 04:16:11 +09:00]] 版))
<https://support.cloudflare.com/hc/en-us/articles/200170986-How-does-CloudFlare-handle-HTTP-Request-headers->