Make IB more configurable

[chhwang]

• Added port and gidIndex field in the IB endpoint config (and deviceIndex field for future usages)
• Added MSCCLPP_IBV_SO env variable to specify a custom libibverbs.so
• Added --ib_gid_index CLI option to mp_unit_tests
• Other minor fixes

[Copilot]

Pull request overview

This PR enhances InfiniBand (IB) configurability by adding support for custom port selection, GID index specification, and custom libibverbs library loading. The changes enable more flexible deployment in heterogeneous IB environments where different ports or GID indices may be required.

Key changes:

• Added port, gidIndex, and deviceIndex fields to EndpointConfig::Ib structure
• Introduced MSCCLPP_IBV_SO environment variable for custom libibverbs library paths
• Added --ib_gid_index CLI option to mp_unit_tests for test-time configuration

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
include/mscclpp/core.hpp	Added new IB configuration fields (port, gidIndex, deviceIndex) to EndpointConfig::Ib with default values
include/mscclpp/env.hpp	Added ibvSo field to support MSCCLPP_IBV_SO environment variable
src/include/ib.hpp	Updated IbQp constructor to accept port and gidIndex; removed port from IbQpInfo struct; added portNum_ and gidIndex_ member variables
src/ib.cc	Refactored IbQp initialization and validation to use configurable port and GID index; updated port usability checks
src/endpoint.cc	Updated createQp call to pass port and gidIndex from config
src/env.cpp	Added reading and logging of MSCCLPP_IBV_SO environment variable; refactored template logic
src/ibverbs_wrapper.cc	Implemented custom libibverbs.so loading via MSCCLPP_IBV_SO environment variable
test/mp_unit/mp_unit_tests.hpp	Fixed license header capitalization (MIT License)
test/mp_unit/mp_unit_tests.cc	Enhanced argument parser with flexible syntax; added --ib_gid_index option; fixed license header
test/mp_unit/port_channel_tests.cu	Updated to use EndpointConfig with gidIndex from command-line argument
test/mp_unit/ib_tests.cu	Changed IB device selection from division to modulo; updated test data type to uint64_t; added gidIndex parameter
python/csrc/core_py.cpp	Added Python bindings for new IB configuration fields with both camelCase and snake_case accessors
python/test/_cpp/proxy_test.cpp	Changed nanobind casts from const reference to value type; switched to emplace_back

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[Copilot]

When a custom libibverbs library is specified via MSCCLPP_IBV_SO but fails to load, the code silently falls through to the default library search without any warning or error. This could lead to confusion when the user expects a specific library to be used but a different one is loaded instead. Consider logging a warning or error message if the custom library path is specified but fails to load.

Suggested change

	globalIBVerbsHandle.reset(handle);
	globalIBVerbsHandle.reset(handle);
	} else {
	WARN(NET, "Failed to load custom libibverbs library specified by MSCCLPP_IBV_SO ('", mscclpp::env()->ibvSo, "'): ", std::string(::dlerror()));

[Copilot]

The operator changed from division (/) to modulo (%). This changes the device selection logic significantly. Previously, if there were multiple ranks per node and multiple IB devices, the division would distribute ranks across IB devices (e.g., with 8 ranks and 4 devices: ranks 0-1 use device 0, ranks 2-3 use device 1, etc.). Now with modulo, ranks are distributed round-robin (e.g., ranks 0,4 use device 0, ranks 1,5 use device 1, etc.). Please verify this behavioral change is intentional, as it may affect multi-device configurations.

Suggested change

	int ibDevId = (gEnv->rank % gEnv->nRanksPerNode) % mscclpp::getIBDeviceCount();
	int ibDevId = (gEnv->rank % gEnv->nRanksPerNode) / (gEnv->nRanksPerNode / mscclpp::getIBDeviceCount());

[Copilot]

The naming convention is inconsistent: the C++ struct uses camelCase (deviceIndex, gidIndex) but the Python property names use snake_case (ib_device_index, ib_gid_index). While the def_rw attributes correctly use camelCase to match the C++ members, the def_prop_rw properties add an "ib_" prefix and use snake_case. This creates two different ways to access the same fields in Python, which could be confusing. Consider using a consistent naming convention.