ibvpostrecv

ibv_post_recv is a function in the libibverbs API used to post one or more receive work requests to the receive queue of a queue pair (QP). It is a core primitive for handling incoming messages in InfiniBand and RDMA communications, enabling the hardware to DMA incoming data into user buffers described by the posted work requests.

The typical prototype is: int ibv_post_recv(struct ibv_qp *qp, const struct ibv_recv_wr *wr, struct ibv_recv_wr **bad_wr); The qp parameter selects the target queue pair. The wr parameter points to the first receive work request in a singly linked list of ibv_recv_wr structures. The bad_wr parameter, if non-NULL, is used to return the first failing receive work request in the chain in case of an error.

A receive work request describes one or more memory buffers via a linked array of scatter/gather entries (struct ibv_sge) and includes a work-request identifier (wr_id) that the application can use to correlate completions with posted requests. The memory buffers referenced by the SGEs must be registered with the protection domain to be accessible by the network hardware.

On success, ibv_post_recv returns 0 and sets bad_wr to NULL. On failure, it returns a nonzero error code and sets bad_wr to point to the first problematic receive work request. Common failure reasons include an inappropriate QP state, insufficient resources to queue the WRs, or unregistered or inaccessible memory regions in the SGEs.

Usage typically involves preparing a pool of pre-registered buffers, constructing a linked list of ibv_recv_wr with corresponding SGEs, and repeatedly posting them to maintain a ready set of buffers for incoming data. Completion and processing of received messages are then handled through the completion queue.

See also: ibv_post_send.