Added #ifdef __cplusplus / extern "C" { ... } / #endif to ~65 headers in src/ and lib/, enabling the C library to be linked into C++ code (chatgui). Fixed packet_dump.h (added missing header guard) and etcp_bbr.h (#pragma once guard).
- Add etcp_udp_send_fn_t hook typedef, send_hook/send_hook_ctx fields to ETCP_LINK - Implement etcp_udp_send() wrapper — all UDP sends go through one point - Remove loss_rate from ETCP_SOCKET, CFG_SERVER, config parser, send path - Add dummynet_filter: inline send-hook with loss/delay, no proxy socket needed - Rewrite test_bgp_route_exchange: 3-node chain A(2 links)↔B↔C, 7 phases with dummynet_filter-based link failure/recovery simulation - Clean up tests: remove skeleton test_routing_mesh, 6 debug/stale test files - Refactor test_etcp_simple_traffic and test_pkt_normalizer_etcp (remove debug spam) - Fix test_etcp_two_instances: remove private field access, fix false PASS on timeout