Negotiating ECE

[chenBright]

What problem does this PR solve?

Issue Number: resolve

Problem Summary:

The RDMA endpoint already declares the intent to do ECE (Enhanced Connection Establishment) negotiation (BringUpQp is gated by FLAGS_rdma_ece), but the existing implementation never exchanges ECE capabilities between the two peers.

What is changed and the side effects?

Changed:

This PR implements an end-to-end ECE negotiation in the v3 handshake.

• Client (RdmaHandshakeClientV3::SendLocalHello): query local ECE, store it in _outgoing_ece, advertise it in the v3 hello.
• Server (BringUpQp): apply the client's ECE during INIT->RTR (ibv_set_ece). After QP reaches RTS, ibv_query_ece to obtain the reduced/negotiated ECE (the subset both peers support) and store it in _outgoing_ece.
• Server (SendLocalHello → FillLocalRdmaHello): advertise the negotiated ECE in the reply hello.
• Client (BringUpQp): apply the server's reduced ECE during INIT->RTR.

Side effects:

• Performance effects:

• Breaking backward compatibility:

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Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[Copilot]

Pull request overview

This PR adds end-to-end Enhanced Connection Establishment (ECE) negotiation support to the RDMA v3 (“RDM3”) handshake by extending the protobuf hello message, soft-loading the necessary libibverbs APIs, and adding unit tests that validate the degrade-safe wire behavior under UT/no-hardware mode.

Changes:

• Extend the v3 handshake protobuf (RdmaHello) to optionally carry an ECE capability block.
• Soft-load ibv_query_ece / ibv_set_ece so RDMA init can succeed on older libibverbs (ECE disabled when unavailable).
• Add UTs that ensure v3 hello round-trips with/without ECE and that server replies omit ECE in degrade cases.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
test/brpc_rdma_unittest.cpp	Adds UT coverage for v3 hello ECE field presence/absence and degrade-safe server replies.
src/brpc/rdma/rdma_helper.cpp	Makes ECE-related ibverbs symbols optional at runtime via soft-loading.
src/brpc/rdma/rdma_handshake.proto	Adds optional RdmaEce message to the v3 hello protobuf schema.
src/brpc/rdma/rdma_handshake.h	Extends parsed handshake state to carry optional ibv_ece for v3 peers.
src/brpc/rdma/rdma_handshake.cpp	Implements client-side ECE capability query + hello advertisement and v3 hello encode/decode for ECE.
src/brpc/rdma/rdma_endpoint.h	Adds per-endpoint storage for the next outgoing ECE payload to advertise.
src/brpc/rdma/rdma_endpoint.cpp	Updates QP bring-up signature and adds server-side negotiated ECE query for reply hello.
.github/workflows/ci-linux.yml	Runs the full Bazel test suite for the RDMA-configured job (removes prior filter).

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