[multicast] Add multicast replication support for (upcoming) softnpu/a4x2#240
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[multicast] Add multicast replication support for (upcoming) softnpu/a4x2#240zeeshanlakhani wants to merge 1 commit intomainfrom
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Introduce two-group multicast replication (mcast_grp_a / mcast_grp_b) modeled after dendrite's replication contract and P4 sidecar expectations. When egress metadata declares the multicast field triplet, the generated pipeline replicates packets to group members with per-copy attribution tags, ingress-port exclusion, and mcast-over-broadcast precedence. ## Slice codegen fix Fix a latent bug where non-byte-aligned multi-byte slices (e.g., field[11:4] on bit<32>) produced incorrect bitvec ranges after header byte-reversal. Validation moves to HLIR so these are now rejected at compile time with a diagnostic rather than silently generating wrong code. ## Multicast contract The codegen path activates when egress_metadata_t declares all three fields: mcast_grp_a, mcast_grp_b, and mcast_replication. Partial declarations of these fields are caught at codegen time. A separate softnpu_mcast.p4 test platform definition keeps multicast opt-in. ## Runtime support McastReplicationTag tracks per-copy group attribution (External / Underlay / Both) via bitwise OR, distinct from dendrite's MULTICAST_TAG_* wire encoding. Five new required methods on the Pipeline trait expose group management. ## Tests Integration tests covering varying multicast workflows. Two end-to-end HLIR tests verify slice alignment diagnostics through the full compiler pipeline.
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…protocol This extends the management message protocol with operations for multicast group lifecycle: create, destroy, add port, remove port, and list. These dispatch to the corresponding [p4rs](https://github.com/oxidecomputer/p4) Pipeline trait methods (add_mcast_group, remove_mcast_group, add_mcast_port, etc.) that were added to support bifurcated multicast replication in the p4rs codegen. Mutating operations (create, destroy, add, remove) are fire-and-forget, matching the existing TableAdd/TableRemove pattern. `MulticastGroupList` is the only round-trip operation, returning a sorted group-to-ports mapping for use by dendrite's `AsicMulticastOps` queries. The `MulticastPortAdd` struct carries rid and level1_excl_id for API parity with dendrite's AsicMulticastOps trait, though softnpu does not use them. Tofino's PRE handles per-replica identification and exclusion via these fields. softnpu handles the equivalent via `McastReplicationTag` in the codegenning. This branch depends on the related oxidecomputer/p4#240.
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This PR introduces two-group multicast replication (mcast_grp_a / mcast_grp_b) modeled after dendrite's replication contract and P4 sidecar expectations. When egress metadata declares the multicast field triplet, the generated pipeline replicates packets to group members with per-copy attribution tags, ingress-port exclusion, and mcast-over-broadcast precedence.
Fix a latent issue where non-byte-aligned multi-byte slices (e.g., field[11:4] on bit<32>) produced incorrect bitvec ranges after header byte-reversal. Validation moves to HLIR so these are now rejected at compile time with a diagnostic rather than silently generating wrong code.
The codegen path activates when egress_metadata_t declares all three fields: mcast_grp_a, mcast_grp_b, and mcast_replication. Partial declarations of these fields are caught at codegen time. A separate softnpu_mcast.p4 test platform definition keeps multicast opt-in.
McastReplicationTag tracks per-copy group attribution (External / Underlay / Both) via bitwise OR, distinct from dendrite's MULTICAST_TAG_* wire encoding. Five new required methods on the Pipeline trait expose group management.
Integration tests covering varying multicast workflows. Two end-to-end HLIR tests verify slice alignment diagnostics through the full compiler pipeline.