FINDING · DETECTION
The whitelist enforcement drops TLS ClientHello packets to non-whitelisted destination IPs while still accepting the TCP SYN, meaning the block occurs at or after the TCP handshake completes but before application-layer data is processed. This behavior is consistent with TSPU-level in-path interception rather than BGP null-routing.
From 2025-its0ka-mobile-network-website — Mobile network website whitelist · Issue body (its0ka, Sep 7 2025) · 2025 · net4people/bbs
Implications
- TCP-based circumvention protocols cannot rely on completing a TCP handshake as evidence that a path is unblocked; the censor allows SYN/SYN-ACK but drops subsequent data to non-whitelisted IPs.
- Design fallback probing to test actual data delivery (e.g., send a dummy byte after TCP connect) rather than TCP connect success alone.
Tags
Extracted by claude-sonnet-4-6 — review before relying.