rdmaaccept

rdma_accept is a function in the RDMA Connection Manager (RDMA CM) API used to accept a pending inbound connection request on a server-side RDMA communication identifier (struct rdma_cm_id). It is part of the user-space RDMA API provided by libraries such as libibverbs/rdma-core and is used with InfiniBand, RoCE, and iWARP devices. The function fits into the typical server-side handshake: the server listens for connection attempts, receives a connect request event, and then calls rdma_accept to negotiate parameters and complete the connection.

Usage and flow: In a typical workflow, an application creates an RDMA CM ID, binds and listens, and processes events on an event channel. When an RDMA_CM_EVENT_CONNECT_REQUEST is received, the application calls rdma_accept to establish the connection. If successful, the kernel reports RDMA_CM_EVENT_ESTABLISHED to indicate that the connection is up. If the accept fails, the application may reject the request or tear down the attempt using appropriate RDMA CM functions such as rdma_reject or rdma_disconnect.

Parameters: rdma_accept takes two arguments: the RDMA CM ID corresponding to the pending connection, and an optional pointer to a struct rdma_conn_param. The conn_param structure lets the application specify parameters such as responder_resources, initiator_depth, flow_control, retry_count, and rnr_retry_count, as well as private_data_len and private_data for exchanging application-specific information during the connect handshake. If conn_param is NULL, default negotiation values may be used by the underlying transport.

Return value and error handling: the call returns 0 on success or a negative errno on failure, indicating conditions such as invalid state, insufficient resources, or other transport-layer errors. After a successful accept, the application proceeds with the remaining connection setup and data-path operations. See also: rdma_connect, rdma_listen, rdma_cm_id, and the RDMA CM event mechanisms.