New internal/proxyproto package implements PROXY protocol parsing and
writing without buffering past the header boundary (reads exact byte
counts so the connection is correctly positioned for SNI extraction).
Parser: auto-detects v1 (text) and v2 (binary) by first byte. Parses
TCP4/TCP6 for both versions plus v2 LOCAL command. Enforces max header
sizes and read deadlines.
Writer: generates v2 binary headers for IPv4 and IPv6 with PROXY
command.
Server integration:
- Receive: when listener.ProxyProtocol is true, parses PROXY header
before firewall check. Real client IP from header is used for
firewall evaluation and logging. Malformed headers cause RST.
- Send: when route.SendProxyProtocol is true, writes PROXY v2 header
to backend before forwarding the ClientHello bytes.
Tests cover v1/v2 parsing, malformed rejection, timeout, round-trip
write+parse, and five server integration tests: receive with valid
header, receive with garbage, send verification, send-disabled
verification, and firewall evaluation using the real client IP.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
