.\" -*- nroff -*-
.\" Licensed under the OpenIB.org BSD license (FreeBSD Variant) - See COPYING.md
.\"
.TH IBV_POST_RECV 3 2006-10-31 libibverbs "Libibverbs Programmer's Manual"
.SH "NAME"
ibv_post_recv \- post a list of work requests (WRs) to a receive queue
.SH "SYNOPSIS"
.nf
.B #include <infiniband/verbs.h>
.sp
.BI "int ibv_post_recv(struct ibv_qp " "*qp" ", struct ibv_recv_wr " "*wr" ,
.BI "                  struct ibv_recv_wr " "**bad_wr" );
.fi
.SH "DESCRIPTION"
.B ibv_post_recv()
posts the linked list of work requests (WRs) starting with
.I wr
to the receive queue of the queue pair
.I qp\fR.
It stops processing WRs from this list at the first failure (that can
be detected immediately while requests are being posted), and returns
this failing WR through
.I bad_wr\fR.
.PP
The argument
.I wr
is an ibv_recv_wr struct, as defined in <infiniband/verbs.h>.
.PP
.nf
struct ibv_recv_wr {
.in +8
uint64_t                wr_id;     /* User defined WR ID */
struct ibv_recv_wr     *next;      /* Pointer to next WR in list, NULL if last WR */
struct ibv_sge         *sg_list;   /* Pointer to the s/g array */
int                     num_sge;   /* Size of the s/g array */
.in -8
};
.sp
.nf
struct ibv_sge {
.in +8
uint64_t                addr;      /* Start address of the local memory buffer */
uint32_t                length;    /* Length of the buffer */
uint32_t                lkey;      /* Key of the local Memory Region */
.in -8
};
.fi
.SH "RETURN VALUE"
.B ibv_post_recv()
returns 0 on success, or the value of errno on failure (which indicates the failure reason).
.SH "NOTES"
The buffers used by a WR can only be safely reused after WR the
request is fully executed and a work completion has been retrieved
from the corresponding completion queue (CQ).
.PP
If the QP
.I qp
is associated with a shared receive queue, you must use the function
.B ibv_post_srq_recv()\fR,
and not
.B ibv_post_recv()\fR,
since the QP's own receive queue will not be used.
.PP
If a WR is being posted to a UD QP, the Global Routing Header (GRH) of
the incoming message will be placed in the first 40 bytes of the
buffer(s) in the scatter list.  If no GRH is present in the incoming
message, then the first bytes will be undefined.  This means that in
all cases, the actual data of the incoming message will start at an
offset of 40 bytes into the buffer(s) in the scatter list.
.SH "SEE ALSO"
.BR ibv_create_qp (3),
.BR ibv_post_send (3),
.BR ibv_post_srq_recv (3),
.BR ibv_poll_cq (3)
.SH "AUTHORS"
.TP
Dotan Barak <dotanba@gmail.com>