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.
- 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.
SEE ALSO¶
rdma_listen(3),
rdma_reject(3),
rdma_get_cm_event(3)