rx_acked was used for two conflicting purposes:
1. remote ack of our sends (inflight = tx_seq - rx_acked)
2. our last sent ACK seq (dedup: rx_seq != rx_acked)
When the ack timer fired and set rx_acked = rx_seq, it overwrote
the inflight-tracking value. If rx_seq > tx_seq, the computation
tx_seq - rx_acked underflowed (e.g. 18 - 24 = 0xFFFFFFFA),
permanently blocking router_drain_send_q and causing send_q to
grow indefinitely.
Fix:
- Split rx_acked into tx_acked (remote ack, for inflight) and
last_sent_ack_seq (our ACK, for dedup)
- Incoming ACK handler only advances tx_acked forward (stale guard)
- Use int32_t cast on all inflight comparisons to handle stale states
- Add etcp_router architecture diagram (doc/etcp_router_arch.md)
- New SVC_ROUTE_HDR (packed struct, 22 bytes): cmd+dst+src+seq+svc_id
- ETCP_ROUTER_CONN: state per (remote_node_id, svc_id), hash-indexed in router_conns
- Reorder via recv_q (hash by seq), dedup with 32-bit circular compare
- Periodic ACK (100ms), idle ACK (500ms), inflight limit via tx_seq - rx_acked
- Legacy mode: no conn → direct delivery without reorder
- etcp_router_conn_get/send/close API for seq-managed connections
- Unit test test_etcp_router_unit: 18 tests, 3ms, no ETCP/sockets/BGP
Evgeny