NAME

       ibv_query_qp - get the attributes of a queue pair (QP)

SYNOPSIS

       #include <infiniband/verbs.h>

       int ibv_query_qp(struct ibv_qp *qp, struct ibv_qp_attr *attr,
                        int attr_mask,
                        struct ibv_qp_init_attr *init_attr);

DESCRIPTION

       ibv_query_qp()  gets  the  attributes  specified  in attr_mask for the QP qp and returns them through the
       pointers  attr  and  init_attr.   The  argument  attr  is  an   ibv_qp_attr   struct,   as   defined   in
       <infiniband/verbs.h>.

       struct ibv_qp_attr {
               enum ibv_qp_state       qp_state;            /* Current QP state */
               enum ibv_qp_state       cur_qp_state;        /* Current QP state - irrelevant for ibv_query_qp */
               enum ibv_mtu            path_mtu;            /* Path MTU (valid only for RC/UC QPs) */
               enum ibv_mig_state      path_mig_state;      /* Path migration state (valid if HCA supports APM) */
               uint32_t                qkey;                /* Q_Key of the QP (valid only for UD QPs) */
               uint32_t                rq_psn;              /* PSN for receive queue (valid only for RC/UC QPs) */
               uint32_t                sq_psn;              /* PSN for send queue */
               uint32_t                dest_qp_num;         /* Destination QP number (valid only for RC/UC QPs) */
               unsigned int            qp_access_flags;     /* Mask of enabled remote access operations (valid only for RC/UC QPs) */
               struct ibv_qp_cap       cap;                 /* QP capabilities */
               struct ibv_ah_attr      ah_attr;             /* Primary path address vector (valid only for RC/UC QPs) */
               struct ibv_ah_attr      alt_ah_attr;         /* Alternate path address vector (valid only for RC/UC QPs) */
               uint16_t                pkey_index;          /* Primary P_Key index */
               uint16_t                alt_pkey_index;      /* Alternate P_Key index */
               uint8_t                 en_sqd_async_notify; /* Enable SQD.drained async notification - irrelevant for ibv_query_qp */
               uint8_t                 sq_draining;         /* Is the QP draining? (Valid only if qp_state is SQD) */
               uint8_t                 max_rd_atomic;       /* Number of outstanding RDMA reads & atomic operations on the destination QP (valid only for RC QPs) */
               uint8_t                 max_dest_rd_atomic;  /* Number of responder resources for handling incoming RDMA reads & atomic operations (valid only for RC QPs) */
               uint8_t                 min_rnr_timer;       /* Minimum RNR NAK timer (valid only for RC QPs) */
               uint8_t                 port_num;            /* Primary port number */
               uint8_t                 timeout;             /* Local ack timeout for primary path (valid only for RC QPs) */
               uint8_t                 retry_cnt;           /* Retry count (valid only for RC QPs) */
               uint8_t                 rnr_retry;           /* RNR retry (valid only for RC QPs) */
               uint8_t                 alt_port_num;        /* Alternate port number */
               uint8_t                 alt_timeout;         /* Local ack timeout for alternate path (valid only for RC QPs) */
       };

       For  details  on  struct  ibv_qp_cap  see  the  description  of  ibv_create_qp().   For details on struct
       ibv_ah_attr see the description of ibv_create_ah().

RETURN VALUE

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

NOTES

       The  argument  attr_mask  is a hint that specifies the minimum list of attributes to retrieve.  Some RDMA
       devices may return extra attributes not requested, for example if the value can be returned cheaply. This
       has the same form as in ibv_modify_qp().

       Attribute  values  are  valid  if  they  have  been  set  using ibv_modify_qp().  The exact list of valid
       attributes depends on the QP state.

       Multiple calls to ibv_query_qp() may yield some differences in the  values  returned  for  the  following
       attributes: qp_state, path_mig_state, sq_draining, ah_attr (if APM is enabled).

SEE ALSO

       ibv_create_qp(3), ibv_destroy_qp(3), ibv_modify_qp(3), ibv_create_ah(3)

AUTHORS

       Dotan Barak <dotanba@gmail.com>