2-rank bidirectional ring deadlock: when E and W neighbors point to the
same peer, sender-coord matching in _handle_meta_arrival / _credit_worker
picked the first direction in dict order, landing data in the wrong rx
slot relative to what the kernel recv(W) was waiting on.
Fix (ADR-0025 D1/D2/D3):
- install.reverse_direction: prefer OPPOSITE direction (E↔W, N↔S) when
peer has it pointing back to us; fallback to any matching for
topologies without opposite convention (tree_binary parent/child).
- _handle_meta_arrival: match by token.dst_addr range against each qp's
my_rx_base_pa + n_slots × slot_size window (unambiguous).
- _credit_worker: match by credit.dst_rx_base_pa == qp.peer.rx_base_pa.
- IpcqCreditMetadata: new dst_rx_base_pa field carrying receiver-side
rx base; _delayed_credit_send fills it from the consuming qp.
Tests (Phase 1 → Phase 2):
- test_reverse_direction_opposite_preference_2rank_ring
- test_reverse_direction_opposite_preference_4rank_ring_sanity
- test_meta_arrival_matches_by_dst_addr_same_peer
- test_credit_matches_by_dst_rx_base_pa_same_peer
- Existing credit-return test updated with dst_rx_base_pa.
508 tests pass.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
ywkang
32536daf2e