This driver implements the iWARP RDMA transport over
the Linux TCP/IP network stack. It enables a system with a
standard Ethernet adapter to interoperate with a iWARP
adapter or with another system running the SIW driver.
(See also RXE which is a similar software driver for RoCE.)

The driver interfaces with the Linux RDMA stack and
implements both a kernel and user space RDMA verbs API.
The user space verbs API requires a support
library named libsiw which is loaded by the generic user
space verbs API, libibverbs. To implement RDMA over
TCP/IP, the driver further interfaces with the Linux
in-kernel TCP socket layer.

source code:

drivers/infiniband/sw/siw/