5a4e292440
apply_cell_rules drops all traffic from a cell's subnet except specific service ports. This also drops ICMP replies and TCP ACKs for connections initiated by local peers to the connected cell, breaking cross-cell routing (ping to 10.0.0.1 silently dropped by test's cell DROP rule). Fix: ensure_forward_stateful() inserts a stateful ESTABLISHED,RELATED ACCEPT at the top of FORWARD. Called from apply_cell_rules (every cell add/update) and from _apply_startup_enforcement. Idempotent. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>