RDMA_GET_CM_EVENT(3) Librdmacm Programmer's Manual RDMA_GET_CM_EVENT(3)NAMErdma_get_cm_event - Retrieves the next pending communication event.
SYNOPSIS
#include <rdma/rdma_cma.h>
int rdma_get_cm_event (struct rdma_event_channel *channel, struct
rdma_cm_event **event);
ARGUMENTS
channel Event channel to check for events.
event Allocated information about the next communication event.
DESCRIPTION
Retrieves a communication event. If no events are pending, by default,
the call will block until an event is received.
RETURN VALUE
Returns 0 on success, or -1 on error. If an error occurs, errno will
be set to indicate the failure reason.
NOTES
The default synchronous behavior of this routine can be changed by mod‐
ifying the file descriptor associated with the given channel. All
events that are reported must be acknowledged by calling
rdma_ack_cm_event. Destruction of an rdma_cm_id will block until
related events have been acknowledged.
EVENT DATA
Communication event details are returned in the rdma_cm_event struc‐
ture. This structure is allocated by the rdma_cm and released by the
rdma_ack_cm_event routine. Details of the rdma_cm_event structure are
given below.
id The rdma_cm identifier associated with the event. If the
event type is RDMA_CM_EVENT_CONNECT_REQUEST, then this ref‐
erences a new id for that communication.
listen_id For RDMA_CM_EVENT_CONNECT_REQUEST event types, this refer‐
ences the corresponding listening request identifier.
event Specifies the type of communication event which occurred.
See EVENT TYPES below.
status Returns any asynchronous error information associated with
an event. The status is zero if the operation was success‐
ful, otherwise the status value is non-zero and is either
set to an errno or a transport specific value. For details
on transport specific status values, see the event type
information below.
param Provides additional details based on the type of event.
Users should select the conn or ud subfields based on the
rdma_port_space of the rdma_cm_id associated with the
event. See UD EVENT DATA and CONN EVENT DATA below.
UD EVENT DATA
Event parameters related to unreliable datagram (UD) services:
RDMA_PS_UDP and RDMA_PS_IPOIB. The UD event data is valid for
RDMA_CM_EVENT_ESTABLISHED and RDMA_CM_EVENT_MULTICAST_JOIN events,
unless stated otherwise.
private_data
References any user-specified data associated with
RDMA_CM_EVENT_CONNECT_REQUEST or RDMA_CM_EVENT_ESTABLISHED
events. The data referenced by this field matches that
specified by the remote side when calling rdma_connect or
rdma_accept. This field is NULL if the event does not
include private data. The buffer referenced by this
pointer is deallocated when calling rdma_ack_cm_event.
private_data_len
The size of the private data buffer. Users should note
that the size of the private data buffer may be larger than
the amount of private data sent by the remote side. Any
additional space in the buffer will be zeroed out.
ah_attr Address information needed to send data to the remote end‐
point(s). Users should use this structure when allocating
their address handle.
qp_num QP number of the remote endpoint or multicast group.
qkey QKey needed to send data to the remote endpoint(s).
CONN EVENT DATA
Event parameters related to connected QP services: RDMA_PS_TCP. The
connection related event data is valid for RDMA_CM_EVENT_CON‐
NECT_REQUEST and RDMA_CM_EVENT_ESTABLISHED events, unless stated other‐
wise.
private_data
References any user-specified data associated with the
event. The data referenced by this field matches that
specified by the remote side when calling rdma_connect or
rdma_accept. This field is NULL if the event does not
include private data. The buffer referenced by this
pointer is deallocated when calling rdma_ack_cm_event.
private_data_len
The size of the private data buffer. Users should note
that the size of the private data buffer may be larger than
the amount of private data sent by the remote side. Any
additional space in the buffer will be zeroed out.
responder_resources
The number of responder resources requested of the recipi‐
ent. This field matches the initiator depth specified by
the remote node when calling rdma_connect and rdma_accept.
initiator_depth
The maximum number of outstanding RDMA read/atomic opera‐
tions that the recipient may have outstanding. This field
matches the responder resources specified by the remote
node when calling rdma_connect and rdma_accept.
flow_control
Indicates if hardware level flow control is provided by the
sender.
retry_count For RDMA_CM_EVENT_CONNECT_REQUEST events only, indicates
the number of times that the recipient should retry send
operations.
rnr_retry_count
The number of times that the recipient should retry
receiver not ready (RNR) NACK errors.
srq Specifies if the sender is using a shared-receive queue.
qp_num Indicates the remote QP number for the connection.
EVENT TYPES
The following types of communication events may be reported.
RDMA_CM_EVENT_ADDR_RESOLVED
Address resolution (rdma_resolve_addr) completed successfully.
RDMA_CM_EVENT_ADDR_ERROR
Address resolution (rdma_resolve_addr) failed.
RDMA_CM_EVENT_ROUTE_RESOLVED
Route resolution (rdma_resolve_route) completed successfully.
RDMA_CM_EVENT_ROUTE_ERROR
Route resolution (rdma_resolve_route) failed.
RDMA_CM_EVENT_CONNECT_REQUEST
Generated on the passive side to notify the user of a new con‐
nection request.
RDMA_CM_EVENT_CONNECT_RESPONSE
Generated on the active side to notify the user of a successful
response to a connection request. It is only generated on
rdma_cm_id's that do not have a QP associated with them.
RDMA_CM_EVENT_CONNECT_ERROR
Indicates that an error has occurred trying to establish or a
connection. May be generated on the active or passive side of a
connection.
RDMA_CM_EVENT_UNREACHABLE
Generated on the active side to notify the user that the remote
server is not reachable or unable to respond to a connection
request. If this event is generated in response to a UD QP res‐
olution request over InfiniBand, the event status field will
contain an errno, if negative, or the status result carried in
the IB CM SIDR REP message.
RDMA_CM_EVENT_REJECTED
Indicates that a connection request or response was rejected by
the remote end point. The event status field will contain the
transport specific reject reason if available. Under Infini‐
Band, this is the reject reason carried in the IB CM REJ mes‐
sage.
RDMA_CM_EVENT_ESTABLISHED
Indicates that a connection has been established with the remote
end point.
RDMA_CM_EVENT_DISCONNECTED
The connection has been disconnected.
RDMA_CM_EVENT_DEVICE_REMOVAL
The local RDMA device associated with the rdma_cm_id has been
removed. Upon receiving this event, the user must destroy the
related rdma_cm_id.
RDMA_CM_EVENT_MULTICAST_JOIN
The multicast join operation (rdma_join_multicast) completed
successfully.
RDMA_CM_EVENT_MULTICAST_ERROR
An error either occurred joining a multicast group, or, if the
group had already been joined, on an existing group. The speci‐
fied multicast group is no longer accessible and should be
rejoined, if desired.
RDMA_CM_EVENT_ADDR_CHANGE
The network device associated with this ID through address reso‐
lution changed its HW address, eg following of bonding failover.
This event can serve as a hint for applications who want the
links used for their RDMA sessions to align with the network
stack.
RDMA_CM_EVENT_TIMEWAIT_EXIT
The QP associated with a connection has exited its timewait
state and is now ready to be re-used. After a QP has been dis‐
connected, it is maintained in a timewait state to allow any in
flight packets to exit the network. After the timewait state
has completed, the rdma_cm will report this event.
SEE ALSOrdma_ack_cm_event(3), rdma_create_event_channel(3),
rdma_resolve_addr(3), rdma_resolve_route(3), rdma_connect(3), rdma_lis‐
ten(3), rdma_join_multicast(3), rdma_destroy_id(3), rdma_event_str(3)librdmacm 2007-10-31 RDMA_GET_CM_EVENT(3)
