Initiates an active connection request.
Syntax
#include <rdma/rdma_cma.h>
int rdma_connect(struct rdma_cm_id *id, struct rdma_conn_param *conn_param);
Description
The rdma_connect function
initiates a connection request to a remote destination.
Note: You must have resolved a route to the destination address
by calling rdma_resolve_route before calling the rdma_connect routine.
Connection Properties
The following properties
are used to configure the communication specified by the
conn_param parameter
when connecting or establishing a datagram communication.
- 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. private_data might be NULL if
it is not required.
- private_data_len:
- Specifies the size of the user-controlled data buffer.
- responder_resources:
- The maximum number of outstanding RDMA read operations that the
local side accepts from the remote side. Applies only to RDMA_PS_TCP.
The responder_resources value must be less than or equal to
the local RDMA device attribute max_qp_rd_atom and remote RDMA
device attribute max_qp_init_rd_atom. The remote endpoint can
adjust this value when accepting the connection.
- initiator_depth:
- The maximum number of outstanding RDMA read operations that the
local side has to the remote side. Applies only to RDMA_PS_TCP. The initiator_depth value
must be less than or equal to the local RDMA device attribute max_qp_init_rd_atom and
remote RDMA device attribute max_qp_rd_atom. The remote endpoint
can adjust this value when accepting the connection.
- flow_control:
- Specifies if the hardware flow control is available. The flow_control value
is exchanged with the remote peer and is not used to configure the
QP. Applies only to RDMA_PS_TCP, and is specific to the InfiniBand architecture.
- retry_count:
- The maximum number of times that a data transfer operation must
be tried on the connection when an error occurs. The retry_count setting
controls the number of times to retry send RDMA, and atomic operations
when time outs occur. Applies only to RDMA_PS_TCP, and is specific
to the InfiniBand architecture.
- rnr_retry_count:
- The maximum number of times that a send operation from the remote
peer is tried on a connection after receiving a receiver not ready (RNR)
error. RNR errors are generated when a send request arrives before
a buffer is posted to receive the incoming data. Applies only to RDMA_PS_TCP,
and is specific to the InfiniBand architecture.
- srq:
- Specifies if the QP associated with the connection is using a
shared receive queue. The srq field is ignored by the library
if a QP is created on the rdma_cm_id. Applies only to RDMA_PS_TCP
and is currently not supported.
- qp_num:
- Specifies the QP number associated with the connection. The qp_num field
is ignored by the library if a QP is created on the rdma_cm_id. Applies
only to RDMA_PS_TCP.
- iWARP specific:
- Connections established over iWARP RDMA devices currently require
that the active side of the connection send the first message.
Parameters
| id |
Specifies the RDMA identifier. |
| conn_param |
Specifies the connection parameters. |
Return Values
The
rdma_connect function
returns the following values:
| 0 |
On success. |
| -1 |
Error, see errno. |
| -EINVAL |
- If the id or conn_param parameter is NULL
- If the parameter conn_param->responder_resources is bigger than
the local RDMA device attribute max_qp_rd_atom, and remote
RDMA device attribute max_qp_init_rd_atom
- If the parameter onn_param->initiator_depth is bigger than the
local RDMA device attribute max_qp_init_rd_atom, and remote
RDMA device attribute max_qp_rd_atom
|
| -EPROTONOSUPPORT |
id->ps is not RDMA_PS_TCP. |
| -ENODATA |
The write operation on id->channel->fd failed. |