fi_cm(3) Libfabric Programmer's Manual
fi_cm - Connection management operations
- fi_connect / fi_listen / fi_accept / fi_reject / fi_shutdown
- Manage endpoint connection state.
- fi_setname / fi_getname / fi_getpeer
- Set local, or return local or peer endpoint address.
- ep / pep
- Fabric endpoint on which to change connection state.
- Buffer to address. On a set call, the endpoint will be assigned the specified address. On a get, the local address will be copied into the buffer, up to the space provided. For connect, this parameter indicates the peer address to connect to. The address must be in the same format as that specified using fi_info: addr_format when the endpoint was created.
- On input, specifies size of addr buffer. On output, stores number of bytes written to addr buffer.
- User-specified data exchanged as part of the connection exchange.
- Size of param buffer.
- Fabric information associated with a connection request.
- Additional flags for controlling connection operation.
- User context associated with the request.
Connection management functions are used to connect an connection-oriented endpoint to a peer endpoint.
The fi_listen call indicates that the specified endpoint should be transitioned into a passive connection state, allowing it to accept incoming connection requests. Connection requests against a listening endpoint are reported asynchronously to the user through a bound CM event queue using the FI_CONNREQ event type. The number of outstanding connection requests that can be queued at an endpoint is limited by the listening endpoint’s backlog parameter. The backlog is initialized based on administrative configuration values, but may be adjusted through the fi_control call.
The fi_connect call initiates a connection request on a connection-oriented endpoint to the destination address.
fi_accept / fi_reject
The fi_accept and fi_reject calls are used on the passive (listening) side of a connection to accept or reject a connection request, respectively. To accept a connection, the listening application first waits for a connection request event (FI_CONNREQ). After receiving such an event, the application allocates a new endpoint to accept the connection. This endpoint must be allocated using an fi_info structure referencing the handle from this FI_CONNREQ event. fi_accept is then invoked with the newly allocated endpoint. If the listening application wishes to reject a connection request, it calls fi_reject with the listening endpoint and a reference to the connection request.
A successfully accepted connection request will result in the active (connecting) endpoint seeing an FI_CONNECTED event on its associated event queue. A rejected or failed connection request will generate an error event. The error entry will provide additional details describing the reason for the failed attempt.
An FI_CONNECTED event will also be generated on the passive side for the accepting endpoint once the connection has been properly established. The fid of the FI_CONNECTED event will be that of the endpoint passed to fi_accept as opposed to the listening passive endpoint. Outbound data transfers cannot be initiated on a connection-oriented endpoint until an FI_CONNECTED event has been generated. However, receive buffers may be associated with an endpoint anytime.
The fi_shutdown call is used to gracefully disconnect an endpoint from its peer. The flags parameter is reserved and must be 0.
Outstanding operations posted to the endpoint when fi_shutdown is called will be canceled or discarded. Notification of canceled operations will be reported by the provider to the corresponding completion queue(s). Discarded operations will silently be dropped, with no completions generated. The choice of canceling, versus discarding operations, is provider dependent. However, all canceled completions will be written before fi_shutdown returns.
When called, fi_shutdown does not affect completions already written to a completion queue. Any queued completions associated with asynchronous operations posted to the endpoint may still be retrieved from the corresponding completion queue(s) after an endpoint has been shutdown.
An FI_SHUTDOWN event will be generated for an endpoint when the remote peer issues a disconnect using fi_shutdown or abruptly closes the endpoint. Note that in the abrupt close case, an FI_SHUTDOWN event will only be generated if the peer system is reachable and a service or kernel agent on the peer system is able to notify the local endpoint that the connection has been aborted.
The fi_setname call may be used to modify or assign the address of the local endpoint. It is conceptually similar to the socket bind operation. An endpoint may be assigned an address on its creation, through the fi_info structure. The fi_setname call allows an endpoint to be created without being associated with a specific service (e.g., port number) and/or node (e.g., network) address, with the addressing assigned dynamically. The format of the specified addressing data must match that specified through the fi_info structure when the endpoint was created.
If no service address is specified and a service address has not yet been assigned to the endpoint, then the provider will allocate a service address and assign it to the endpoint. If a node or service address is specified, then, upon successful completion of fi_setname, the endpoint will be assigned the given addressing. If an address cannot be assigned, or the endpoint address cannot be modified, an appropriate fabric error number is returned.
fi_getname / fi_getpeer
The fi_getname and fi_getpeer calls may be used to retrieve the local or peer endpoint address, respectively. On input, the addrlen parameter should indicate the size of the addr buffer. If the actual address is larger than what can fit into the buffer, it will be truncated and -FI_ETOOSMALL will be returned. On output, addrlen is set to the size of the buffer needed to store the address, which may be larger than the input value.
fi_getname is not guaranteed to return a valid source address until after the specified endpoint has been enabled or has had an address assigned. An endpoint may be enabled explicitly through fi_enable, or implicitly, such as through fi_connect or fi_listen. An address may be assigned using fi_setname. fi_getpeer is not guaranteed to return a valid peer address until an endpoint has been completely connected – an FI_CONNECTED event has been generated.
Flag values are reserved and must be 0.
Returns 0 on success. On error, a negative value corresponding to fabric
errno is returned. Fabric errno values are defined in
For connection-oriented endpoints, the buffer referenced by param will be sent as part of the connection request or response, subject to the constraints of the underlying connection protocol. Applications may use fi_getopt with the FI_OPT_CM_DATA_SIZE endpoint option to determine the size of application data that may be exchanged as part of a connection request or response. The fi_connect, fi_accept, and fi_reject calls will silently truncate any application data which cannot fit into underlying protocol messages. User data exchanged as part of the connection process is available as part of the fi_eq_cm_entry structure, for FI_CONNREQ and FI_CONNECTED events, or as additional err_data to fi_eq_err_entry, in the case of a rejected connection.