Common client IP fields

The client-ip-headers feature provides one direct function per field:

• extract_header_cf_connecting_ip / extract_request_cf_connecting_ip;
• extract_header_cloudfront_viewer_address / matching Request function;
• extract_header_fly_client_ip / matching Request function;
• extract_header_true_client_ip / matching Request function;
• extract_header_x_envoy_external_address / matching Request function;
• extract_header_x_real_ip / matching Request function.

All return Result<Option<IpAddr>, Error>. Missing fields return None. Fields are singular; duplicates, non-text values, and malformed addresses fail. CloudFront-Viewer-Address accepts IPv4 and IPv6 IP:port forms, including CloudFront’s unbracketed IPv6 representation.

These are vendor or de facto field names, not IETF standards. Extraction does not authenticate the sender or make the value safe for access control, logging, or rate limiting. The default extract_client_ip order includes CF-Connecting-IP and X-Real-IP; the other sources can be selected through extract_client_ip_with_headers. Selection does not authenticate the sender, so applications must apply a deployment-specific trust policy before using a result. See Standards and compatibility for the complete field classification.