SoftiWARP Software RDMA-over-TCP Driver
SoftiWARP (siw) is a pure-software implementation of the iWARP RDMA protocol that runs over ordinary TCP/IP, letting machines without dedicated RDMA hardware participate in RDMA workloads such as SMB Direct, NVMe-oF, or storage testing. It is commonly paired with real iWARP NICs at the other end of the connection or used for development and interoperability testing.
recommendation
It should stay in the kernel because it remains actively maintained, with refactoring work landing as recently as early 2026 and SMB Direct related additions in mid-2025. Although deployments are niche, current rdma tooling still provisions siw links and Samba's SMB Direct community continues to treat iWARP as a live target, so the software stack has clear ongoing users.
repository signals
sources
- lore.kernel.org
siw was still receiving upstream functional refactoring in February 2026, indicating active maintenance rather than removal.
- lore.kernel.org
siw gained SMB Direct related protocol support in July 2025, showing ongoing feature work for current interoperability use cases.
- man7.org
Current rdma tooling still exposes 'siw' as a supported RDMA link type alongside 'rxe', so the software stack continues to support provisioning it.
- lists.samba.org
2026 Samba/SMB Direct discussion still treats iWARP as a live protocol case, implying present-day niche deployments and testing relevance.
codex reasoning notes (technical)
Real driver directory: local `rg`/`sed` showed `MODULE_DESCRIPTION("Software iWARP Driver")`, `module_init`, and Kconfig text describing a software RDMA-over-TCP driver. Upstream activity was checked with `lore_file_timeline` on `drivers/infiniband/sw/siw/siw_main.c`, which showed recent 2025-2026 feature/refactor traffic and no removal signal. Removal-discussion regex attempts on lore timed out twice, so I did not rely on them. Deployment evidence came from web search results: `rdma-link(8)` confirms current userspace support for `siw`, and Samba technical discussion from February 2026 shows iWARP/SMB Direct still matters in niche modern setups. This is software-only, not hardware-bound silicon, so there is no "still sold" hardware question in the usual sense; present use appears niche but current, so `keep` is more defensible than deprecate/remove.