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rdma_join_multicast_ex - Joins a multicast group with extended options.


#include <rdma/rdma_cma.h>

int rdma_join_multicast_ex (struct rdma_cm_id *id, struct rdma_cm_join_mc_attr_ex *mc_join_attr, void *context);


Communication identifier associated with the request.
Is an rdma_cm_join_mc_attr_ex struct, as defined in <rdma/rdma_cma.h>.
User-defined context associated with the join request.


Joins a multicast group (MCG) with extended options. Currently supporting MC join with a specified join flag.

struct rdma_cm_join_mc_attr_ex {

uint32_t comp_mask; /* Bitwise OR between "rdma_cm_join_mc_attr_mask" enum */ uint32_t join_flags; /* Use a single flag from "rdma_cm_mc_join_flags" enum */ struct sockaddr *addr; /* Multicast address identifying the group to join */

The supported join flags are:

RDMA_MC_JOIN_FLAG_FULLMEMBER - Create multicast group, Send multicast messages to MCG, Receive multicast messages from MCG.

RDMA_MC_JOIN_FLAG_SENDONLY_FULLMEMBER - Create multicast group, Send multicast messages to MCG, Don't receive multicast messages from MCG (send-only).

Initiating a MC join as "Send Only Full Member" on InfiniBand requires SM support, otherwise joining will fail.

Initiating a MC join as "Send Only Full Member" on RoCEv2/ETH will not send any IGMP messages unlike a Full Member MC join. When "Send Only Full Member" is used the QP will not be attached to the MCG.


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.


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


2017-11-17 librdmacm