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IBV_ATTACH_MCAST(3)   Libibverbs Programmer’s Manual  IBV_ATTACH_MCAST(3)
       ibv_attach_mcast, ibv_detach_mcast - attach and detach a queue
       pair (QPs) to/from a multicast group
              #include <infiniband/verbs.h>
              int ibv_attach_mcast(struct ibv_qp *qp, const union ibv_gid *gid, uint16_t lid);
              int ibv_detach_mcast(struct ibv_qp *qp, const union ibv_gid *gid, uint16_t lid);
       ibv_attach_mcast() attaches the QP qp to the multicast group
       having MGID gid and MLID lid.
       ibv_detach_mcast() detaches the QP qp to the multicast group
       having MGID gid and MLID lid.
       ibv_attach_mcast() and ibv_detach_mcast() returns 0 on success, or
       the value of errno on failure (which indicates the failure
       reason).
       Only QPs of Transport Service Type IBV_QPT_UD may be attached to
       multicast groups.
       If a QP is attached to the same multicast group multiple times,
       the QP will still receive a single copy of a multicast message.
       In order to receive multicast messages, a join request for the
       multicast group must be sent to the subnet administrator (SA), so
       that the fabric’s multicast routing is configured to deliver
       messages to the local port.
       ibv_create_qp(3)
       Dotan Barak ⟨dotanba@gmail.com⟩
       This page is part of the rdma-core (RDMA Core Userspace Libraries
       and Daemons) project.  Information about the project can be found
       at ⟨https://github.com/linux-rdma/rdma-core⟩.  If you have a bug
       report for this manual page, send it to
       linux-rdma@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨https://github.com/linux-rdma/rdma-core.git⟩ on 2025-08-11.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2025-08-04.)  If you discover any rendering
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       (which is not part of the original manual page), send a mail to
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libibverbs                      2006-10-31            IBV_ATTACH_MCAST(3)