Direction field in marker.match events
=======================================
Read ubridge dir=<tx|rx> from MARK signal datagrams and forward it
as a "dir" key in the marker.match notification event. The field is
additive -- older ubridge builds omit it and the parser leaves it null,
so consumers fall back to undirected rendering with no version coupling.
Semantics are relative to the capture node (the signal's node=<id>):
tx = capture node is sending (ingressed device-side NIO), rx = it is
receiving (ingressed link-side NIO).
Per-marker direction filter (opt-in, server-side pipeline)
==========================================================
Add a direction field to MarkerCreate and MarkerDefinitionCreate
schemas ("tx" | "rx" | null). Plumb it through the full pipeline:
Schema -> controller (start_marker/update_marker, marker_entry,
_markers_for_node, update_marker_definition sync)
-> REST/MCP handlers -> compute _ubridge_add_marker_filter +
IOU _ubridge_apply_markers -> bridge add_packet_filter dir <tx|rx>
When set, ubridge only fires the mark handler (signal + pcap) for
packets matching the chosen direction. null (default/legacy) = both
directions -- zero behavioural change for existing markers.
Docs and tests
==============
- docs/features/marker-traffic-insight.md: signal format updated,
new Direction section with NIO mapping, arrow mapping, and additive
compatibility note.
- tests/compute/marker/test_marker_manager.py: 3 new parser tests
(dir tx/rx/absent) plus existing test extended to assert dir=None.
13 files, +123/-22, 72 tests pass (zero breakage)
A uBridge MARK signal carries only node= and filter= (no bridge/link field), so when one node is the capture side for several links that share a marker name (always the case for global-{name} definitions on a multi-interface node) the signals were indistinguishable and the (node, filter) registry collapsed them to a single link.
The mark filter is now stamped with its link id (mark <bpf> ... link <link_id>); uBridge echoes it verbatim (link=<link_id>) and the listener uses the signal's link= as the authoritative link_id of the marker.match event, falling back to the registry only for legacy signals without it. base_node and iou apply paths pass link_id; covered by two new listener tests.
