mctpd: Support MCTP Discovery Notify command - #165
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In MCTP networks, endpoints broadcast or send a Discovery Notify control request (0x0D) to inform the Bus Owner when they boot up, reset, or are hot-plugged. Currently, mctpd relies on active bus scanning or static configurations, leaving newly online endpoints undiscovered until the next poll cycle. This change adds support for handling Discovery Notify requests when mctpd is in the Bus Owner role: - Immediately acknowledges Discovery Notify requests over the physical socket with MCTP_CTRL_CC_SUCCESS inside handle_control_discovery_notify() to prevent hardware endpoints (e.g. PCIe VDMs / SMBus sequencers) from dropping subsequent Set Endpoint ID requests while waiting for an ACK. - Asynchronously defers EID assignment and route programming (RTM_NEWROUTE) to the systemd event loop (sd_event_add_defer) to prevent thread blocking. - Safely handles event deferral failures by dropping the request and returning -ENOMEM rather than executing synchronously in receive context, eliminating re-entrance and event loop corruption risks. - Scopes request deduplication to (ifindex, dest_phys) composite keys to prevent cross-bus address collisions on multi-bus platforms. - Enforces per-interface rate-limiting (maximum 5 discovery requests per second) to protect against discovery request floods. - Correctly supports Bridge Endpoints by reserving EID pools and invoking endpoint_allocate_eids() for downstream pool allocation and gateway routing. - Includes comprehensive unit test coverage in test_mctpd.py and test_mctpd_endpoint.py. Assisted-by: Antigravity:Gemini-Next Signed-off-by: Jasmine Cha <chajasmine@google.com>
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I see there's been a few updates; let me know when this is stable and you'd like a review. |
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The code is ready for review, please take a look at this. Thanks. |
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Implement support for the MCTP Discovery Notify control command in mctpd. When an MCTP endpoint issues a Discovery Notify control request to the Bus Owner, mctpd immediately acknowledges the request over the physical socket and defers EID assignment to the main systemd event loop.
This avoids blocking the event thread during control message processing and safely handles EID re-assignments via change_peer_eid(), keeping D-Bus object paths and netlink kernel routing tables synchronized. Also include unit test coverage for Discovery Notify in the test suite.
Assisted-by: Antigravity:Gemini-Next