[1] HTTP 串が元の client の情報を server に伝える欄。

X-Forwarded-By:
X-Forwarded-Host:
X-Forwarded-HTTPS:
X-Forwarded-For:
X-Forwarded-Port:
X-Forwarded-Proto:
X-Forwarded-Protocol:
X-Forwarded-Server:
X-Forwarded-Scheme:
X-Forwarded-Ssl:

関連

[2] Forwarded:, Via:, X-Real-Ip: も参照してください。