Manual Pages  — IBV_POST_RECV

ibv_post_recv - post a list of work requests (WRs) to a receive queue

SYNOPSIS DESCRIPTION RETURN VALUE NOTES SEE ALSO AUTHORS

#include <infiniband/verbs.h> 

int ibv_post_recv(struct ibv_qp *qp, struct ibv_recv_wr *wr, 
                  struct ibv_recv_wr **bad_wr); 

ibv_post_recv() posts the linked list of work requests (WRs) starting with wr to the receive queue of the queue pair qp. 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 bad_wr.

The argument wr is an ibv_recv_wr struct, as defined in <infiniband/verbs.h>.

struct ibv_recv_wr {
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 */
};

struct ibv_sge {
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 */
};

ibv_post_recv() returns 0 on success, or the value of errno on failure (which indicates the failure reason).

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).

If the QP qp is associated with a shared receive queue, you must use the function ibv_post_srq_recv(), and not ibv_post_recv(), since the QP's own receive queue will not be used.

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.