Ubuntu Manpage: rdma_accept - Called to accept a connection request.

NAME

       rdma_accept - Called to accept a connection request.

SYNOPSIS

       #include <rdma/rdma_cma.h>

       int rdma_accept (struct rdma_cm_id *id, struct rdma_conn_param *conn_param);

ARGUMENTS

       id          Connection identifier associated with the request.

       conn_param  Information  needed  to  establish  the connection.  See CONNECTION PROPERTIES
                   below for details.

DESCRIPTION

       Called from the listening side to accept a connection or datagram service lookup request.

RETURN VALUE

       Returns 0 on success, or -1 on error.  If an error occurs, errno will be set  to  indicate
       the failure reason.

NOTES

       Unlike  the  socket  accept  routine, rdma_accept is not called on a listening rdma_cm_id.
       Instead, after calling rdma_listen, the user waits  for  an  RDMA_CM_EVENT_CONNECT_REQUEST
       event  to  occur.   Connection  request  events  give the user a newly created rdma_cm_id,
       similar to a new  socket,  but  the  rdma_cm_id  is  bound  to  a  specific  RDMA  device.
       rdma_accept is called on the new rdma_cm_id.

CONNECTION PROPERTIES

The following properties are used to configure the communication and specified by the
conn_param parameter when accepting a connection or datagram communication request. Users
should use the rdma_conn_param values reported in the connection request event to
determine appropriate values for these fields when accepting. Users may reference the
rdma_conn_param structure in the connection event directly, or can reference their own
structure. If the rdma_conn_param structure from an event is referenced, the event must
not be acked until after this call returns.

If the conn_param parameter is NULL, the values reported in the connection request event
are used, adjusted down based on local hardware restrictions.

private_data
References a user-controlled data buffer. The contents of the buffer are copied
and transparently passed to the remote side as part of the communication request.
May be NULL if private_data is not required.

private_data_len
Specifies the size of the user-controlled data buffer. Note that the actual amount
of data transferred to the remote side is transport dependent and may be larger
than that requested.

responder_resources
The maximum number of outstanding RDMA read and atomic operations that the local
side will accept from the remote side. Applies only to RDMA_PS_TCP. This value
must be less than or equal to the local RDMA device attribute max_qp_rd_atom, but
preferably greater than or equal to the responder_resources value reported in the
connect request event.

initiator_depth
The maximum number of outstanding RDMA read and atomic operations that the local
side will have to the remote side. Applies only to RDMA_PS_TCP. This value must
be less than or equal to the local RDMA device attribute max_qp_init_rd_atom and
the initiator_depth value reported in the connect request event.

flow_control
Specifies if hardware flow control is available. This value is exchanged with the
remote peer and is not used to configure the QP. Applies only to RDMA_PS_TCP.

retry_count
This value is ignored.

rnr_retry_count
The maximum number of times that a send operation from the remote peer should be
retried on a connection after receiving a receiver not ready (RNR) error. RNR
errors are generated when a send request arrives before a buffer has been posted to
receive the incoming data. Applies only to RDMA_PS_TCP.

srq Specifies if the QP associated with the connection is using a shared receive queue.
This field is ignored by the library if a QP has been created on the rdma_cm_id.
Applies only to RDMA_PS_TCP.

qp_num Specifies the QP number associated with the connection. This field is ignored by
the library if a QP has been created on the rdma_cm_id.

INFINIBAND SPECIFIC

       In addition to the connection properties defined above, InfiniBand QPs are configured with
       minimum  RNR  NAK  timer and local ACK timeout values.  The minimum RNR NAK timer value is
       set to 0, for a delay of 655 ms.  The local ACK timeout is calculated based on the  packet
       lifetime  and  local  HCA  ACK delay.  The packet lifetime is determined by the InfiniBand
       Subnet Administrator and is part of the route (path record) information  obtained  by  the
       active side of the connection.  The HCA ACK delay is a property of the locally used HCA.

       The RNR retry count is a 3-bit value.

       The  length  of  the  private  data  provided  by  the  user  is  limited to 196 bytes for
       RDMA_PS_TCP, or 136 bytes for RDMA_PS_UDP.