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.TH "IBV_ATTACH_MCAST" "3" "2006\-10\-31" "libibverbs" "Libibverbs Programmer\(cqs Manual"
.SH NAME
ibv_attach_mcast, ibv_detach_mcast \- attach and detach a queue pair
(QPs) to/from a multicast group
.SH SYNOPSIS
.IP
.EX
#include \f[B]<infiniband/verbs.h>\f[R]

int ibv_attach_mcast(\f[B]struct\f[R] ibv_qp *qp, const \f[B]union\f[R] ibv_gid *gid, uint16_t lid);

int ibv_detach_mcast(\f[B]struct\f[R] ibv_qp *qp, const \f[B]union\f[R] ibv_gid *gid, uint16_t lid);
.EE
.SH DESCRIPTION
\f[B]ibv_attach_mcast()\f[R] attaches the QP \f[I]qp\f[R] to the
multicast group having MGID \f[I]gid\f[R] and MLID \f[I]lid\f[R].
.PP
\f[B]ibv_detach_mcast()\f[R] detaches the QP \f[I]qp\f[R] to the
multicast group having MGID \f[I]gid\f[R] and MLID \f[I]lid\f[R].
.SH RETURN VALUE
\f[B]ibv_attach_mcast()\f[R] and \f[B]ibv_detach_mcast()\f[R] returns 0
on success, or the value of errno on failure (which indicates the
failure reason).
.SH NOTES
Only QPs of Transport Service Type \f[B]IBV_QPT_UD\f[R] may be attached
to multicast groups.
.PP
If a QP is attached to the same multicast group multiple times, the QP
will still receive a single copy of a multicast message.
.PP
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\(cqs multicast routing is configured to deliver messages to the
local port.
.SH SEE ALSO
\f[B]ibv_create_qp\f[R](3)
.SH AUTHOR
Dotan Barak \c
.MT dotanba@gmail.com
.ME \c
