rdma_join_multicast man page

rdma_join_multicast — Joins a multicast group.


#include <rdma/rdma_cma.h>

int rdma_join_multicast (struct rdma_cm_id *id, struct sockaddr *addr, void *context);


Communication identifier associated with the request.
Multicast address identifying the group to join.
User-defined context associated with the join request.


Joins a multicast group and attaches an associated QP to the group.

Return Value

Returns 0 on success, or -1 on error. If an error occurs, errno will be set to indicate the failure reason.


Before joining a multicast group, the rdma_cm_id must be bound to an RDMA device by calling rdma_bind_addr or rdma_resolve_addr. Use of rdma_resolve_addr requires the local routing tables to resolve the multicast address to an RDMA device, unless a specific source address is provided. The user must call rdma_leave_multicast to leave the multicast group and release any multicast resources. After the join operation completes, if a QP is associated with the rdma_cm_id, it is automatically attached to the multicast group when the multicast event is retrieved by the user. Otherwise, the user is responsible for calling ibv_attach_mcast to bind the QP to the multicast group. The join context is returned to the user through the private_data field in the rdma_cm_event.

See Also

rdma_leave_multicast(3), rdma_bind_addr(3), rdma_resolve_addr(3), rdma_create_qp(3), rdma_get_cm_event(3)

Referenced By

rdma_cm(7), rdma_get_cm_event(3), rdma_leave_multicast(3).

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librdmacm Librdmacm Programmer's Manual 2008-01-02