gin: GDAKI reuses shared proxy APIs for MR reg, close, progress, finalize

[anshumang]

Summary

Wire GDAKI plugin APIs that are structurally identical to the proxy APIs
directly to the proxy implementations at compile time, instead of patching
the plugin struct at runtime. Rebased onto current master (post-#1197 and
#1195) to use the v13 GIN API.

Design

11 plugin APIs — init, devices, listen, connect, regMrSym,
regMrSymDmaBuf, deregMrSym, closeColl, closeListen, ginProgress,
finalize — operate on shared types (nccl_ofi_rdma_gin_put_comm etc.)
produced by connect() in both proxy and GDAKI modes. Their semantics are
identical across modes, so GDAKI reuses the proxy implementations directly.
Concretely:

• Un-static the 11 shared functions in nccl_ofi_gin_api.cpp so they have
  external linkage.
• Forward-declare them in nccl_ofi_gin_gdaki.h.
• nccl_ofi_gin_gdaki_plugin now sets all 11 slots to the shared functions
  at compile time. GDAKI-specific stubs (createContext, destroyContext,
  get_properties, queryLastError) stay in nccl_ofi_gin_gdaki.cpp.
• Drop the 4 runtime .init/.devices/.listen/.connect assignments from
  the GDAKI init branch in nccl_ofi_gin_api.cpp; keep the memcpy that
  swaps the exported plugin symbol.

Remaining stubs

• createContext, destroyContext — tracked separately
• queryLastError — writes *hasError = false; paired with createContext
• regMrSym, regMrSymDmaBuf — return ncclInternalError until real GDAKI
  MR registration is wired up
• iput, iputSignal, iget, iflush, test — permanently nullptr in
  GDAKI mode (GPU posts work directly)

Testing

Built on p5en cluster (EFA, libfabric 2.2, CUDA 12.8).

alltoall_perf from nccl-tests (NCCL v2.29.2):

Config	Flags	Result
1-node, 8 ranks	-R 2 -D 3 (pure GIN)	clean exit 0, GDAKI mode enabled on every rank
1-node, 8 ranks	-R 2 -D 4 (hybrid GIN)	same
2-node, 16 ranks	-R 2 -D 3 (pure GIN)	same, both nodes
2-node, 16 ranks	-R 2 -D 4 (hybrid GIN)	same, both nodes

NCCL 2.29 exercises the v11 fallback path; the 4-config run confirms the
compile-time wiring does not regress the non-GDAKI proxy mode.

Repo's own GIN functional test (tests/functional/gin), which uses
ncclGin_v13_t directly:

• 2 ranks, OFI_NCCL_GIN_GDAKI=1
• gin: GDAKI mode enabled (OFI_NCCL_GIN_GDAKI=1) on both ranks
• NCCL-GIN device used … is Libfabric_GDAKI — confirms ncclGinPlugin_v13
  symbol was replaced by nccl_ofi_gin_gdaki_plugin
• gin GDAKI: createContext not yet implemented (nSignals=64, nCounters=0)
  fired on both ranks with real ncclGinConfig_v13_t values
• Clean exit 3 (expected — test returns ncclInternalError)

Description of changes:

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