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Johnathan Corgan
274b09d4ff
Add six forwarding counters that partition transit-forwarded packets by their tree relationship to the chosen next hop: tree-up (peer is our ancestor), tree-down (peer is our descendant and the destination is within its subtree), tree-down-cross (peer is our descendant but the destination is outside its subtree), cross-link descend (lateral peer, destination within its subtree), cross-link ascend (lateral peer, destination outside its subtree), and direct-peer. The six classes sum to forwarded_packets, asserted by a unit test. Classification is computed from tree coordinates at the transit chokepoint, so the error-signal routing callers are excluded. The two "outside the chosen peer's subtree" classes are both up-and-over forwards but differ in what they depend on. Tree-down-cross is the dive-to-tree-child cut-through: we forward down to our own child for a destination not beneath it, which is only possible because the child advertised cross-link reach upward to us, beyond its own subtree. Its count measures how much forwarding depends on that upward advertisement, i.e. what would change if cross-link advertisements were narrowed to subtree-entry only. Cross-link ascend, by contrast, uses the node's own lateral cross-link learned from a peer's split-horizon advertisement, so it does not depend on any upward advertisement. Surface the counters through the forwarding stats snapshot (control socket, show_routing and show_status) and reorganize the fipstop routing tab so its two columns separate own/endpoint traffic (received, delivered, originated) from forwarded/transit traffic (the route-class breakdown and drop reasons), with the tree-down-cross line visually flagged.