rdmagetcmevent

rdma_get_cm_event is a function in the librdmacm library used to retrieve a completion manager (CM) event from a specified event channel. It blocks until a CM event becomes available or an error occurs, returning the event through a pointer parameter. The function is typically used in the management loop of RDMA applications to respond to changes in connection state or CM activity.

To use it, an application first creates an event channel with rdma_create_event_channel and then initiates an RDMA connection lifecycle using the librdmacm API (for example, creating a rdma_cm_id, resolving addresses, and initiating or accepting connections). The main loop repeatedly calls rdma_get_cm_event, processes the returned event, and then acknowledges the event with rdma_ack_cm_event to free resources. This pattern allows the application to react to various lifecycle events such as connection requests, establishments, or disconnections.

The events delivered by rdma_get_cm_event are represented by a struct rdma_cm_event, which includes the event type in event and a pointer to an associated rdma_cm_id in id. Event types cover stages such as address and route resolution, connect requests, established connections, and disconnections, along with other lifecycle changes like a connection being rejected or error conditions. Proper handling typically involves inspecting the event type, taking appropriate actions (e.g., creating resources, initiating connections, or cleaning up), and then acknowledging the event before retrieving the next one.

This function is a core part of the RDMA Connection Manager API and is used in user-space networking code to manage RDMA connections through a structured event-driven model. It requires including the header rdma/rdma_cma.h and linking against the librdmacm library.