cgi.referer # Referer row
cgi.user_agent # User-agent string row
cgi.remote_addr # IP address row
cgi.remote_host # Hostname row
ENV['REMOTE_PORT'] # Port row
cgi.request_method # Request method row
ENV['SERVER_ADMIN'] # Webmaster row
cgi.server_protocol # Server protocol row
cgi.server_software # Server software row

X-Forwarded-For
The IP address of the client.
X-Forwarded-Host
The original host requested by the client in the Host HTTP request header.
X-Forwarded-Server
The hostname of the proxy server.

"HTTP_HOST"
"HTTP_USER_AGENT"
"HTTP_ACCEPT"
"HTTP_ACCEPT_LANGUAGE"
"HTTP_ACCEPT_ENCODING"
"HTTP_DNT"
"HTTP_COOKIE"
"HTTP_UPGRADE_INSECURE_REQUESTS"
"HTTP_PRAGMA"
"HTTP_CACHE_CONTROL"
"HTTP_X_FORWARDED_FOR"
"HTTP_X_FORWARDED_HOST"
"HTTP_X_FORWARDED_SERVER"
"HTTP_CONNECTION"
"PATH"
"LD_LIBRARY_PATH"
"SERVER_SIGNATURE"
"SERVER_SOFTWARE"
"SERVER_NAME"
"SERVER_ADDR"
"SERVER_PORT"
"REMOTE_ADDR"
"DOCUMENT_ROOT"
"REQUEST_SCHEME"
"CONTEXT_PREFIX"
"CONTEXT_DOCUMENT_ROOT"
"SERVER_ADMIN"
"SCRIPT_FILENAME"
"REMOTE_PORT"
"GATEWAY_INTERFACE"
"SERVER_PROTOCOL"
"REQUEST_METHOD"
"QUERY_STRING"
"REQUEST_URI"
"SCRIPT_NAME"