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

name
synopsis
arguments
description
return value
notes
connection properties
infiniband specific
see also

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.