Provided by: libfabric-dev_1.6.2-3ubuntu0.1_amd64 
NAME
fi_getinfo, fi_freeinfo - Obtain / free fabric interface information
fi_allocinfo, fi_dupinfo - Allocate / duplicate an fi_info structure
SYNOPSIS
#include <rdma/fabric.h>
int fi_getinfo(int version, const char *node, const char *service,
uint64_t flags, const struct fi_info *hints,
struct fi_info **info);
void fi_freeinfo(struct fi_info *info);
struct fi_info *fi_allocinfo(void);
struct fi_info *fi_dupinfo(const struct fi_info *info);
ARGUMENTS
version : Interface version requested by application.
node : Optional, name or fabric address to resolve.
service : Optional, service name or port number of address.
flags : Operation flags for the fi_getinfo call.
hints : Reference to an fi_info structure that specifies criteria for selecting the returned fabric
information.
info : A pointer to a linked list of fi_info structures containing response information.
DESCRIPTION
fi_getinfo returns information about available fabric services for reaching specified node or service,
subject to any provided hints. Callers may specify NULL for node, service, and hints in order to
retrieve information about what providers are available and their optimal usage models. If no matching
fabric information is available, info will be set to NULL and the call will return -FI_ENODATA.
Based on the input hints, node, and service parameters, a list of fabric domains and endpoints will be
returned. Each fi_info structure will describe an endpoint that meets the application's specified
communication criteria. Each endpoint will be associated with a domain. Applications can restrict the
number of returned endpoints by including additional criteria in their search hints. Relaxing or
eliminating input hints will increase the number and type of endpoints that are available. Providers
that return multiple endpoints to a single fi_getinfo call should return the endpoints that are highest
performing first. Providers may indicate that an endpoint and domain can support additional capabilities
than those requested by the user only if such support will not adversely affect application performance
or security.
The version parameter is used by the application to request the desired version of the interfaces. The
version determines the format of all data structures used by any of the fabric interfaces. Applications
should use the FI_VERSION(major, minor) macro to indicate the version, with hard-coded integer values for
the major and minor values. The FI_MAJOR_VERSION and FI_MINOR_VERSION enum values defined in fabric.h
specify the latest version of the installed library. However, it is recommended that the integer values
for FI_MAJOR_VERSION and FI_MINOR_VERSION be used, rather than referencing the enum types in order to
ensure compatibility with future versions of the library. This protects against the application being
built from source against a newer version of the library that introduces new fields to data structures,
which would not be initialized by the application.
Node, service, or hints may be provided, with any combination being supported. If node is provided,
fi_getinfo will attempt to resolve the fabric address to the given node. If node is not given,
fi_getinfo will attempt to resolve the fabric addressing information based on the provided hints. Node
is commonly used to provide a network address (such as an IP address) or hostname. Service is usually
associated with a transport address (such as a TCP port number). Node and service parameters may be
mapped by providers to native fabric addresses. Applications may also pass in an FI_ADDR_STR formatted
address (see format details below) as the node parameter. In such cases, the service parameter must be
NULL.
The hints parameter, if provided, may be used to limit the resulting output as indicated below. As a
general rule, specifying a non-zero value for input hints indicates that a provider must support the
requested value or fail the operation with -FI_ENODATA. With the exception of mode bits, hints that are
set to zero are treated as a wildcard. A zeroed hint value results in providers either returning a
default value or a value that works best for their implementation. Mode bits that are set to zero
indicate the application does not support any modes.
The caller must call fi_freeinfo to release fi_info structures returned by this call.
The fi_allocinfo call will allocate and zero an fi_info structure and all related substructures. The
fi_dupinfo will duplicate a single fi_info structure and all the substructures within it.
FI_INFO
struct fi_info {
struct fi_info *next;
uint64_t caps;
uint64_t mode;
uint32_t addr_format;
size_t src_addrlen;
size_t dest_addrlen;
void *src_addr;
void *dest_addr;
fid_t handle;
struct fi_tx_attr *tx_attr;
struct fi_rx_attr *rx_attr;
struct fi_ep_attr *ep_attr;
struct fi_domain_attr *domain_attr;
struct fi_fabric_attr *fabric_attr;
};
next : Pointer to the next fi_info structure in the list. Will be NULL if no more structures exist.
caps - fabric interface capabilities : If specified, indicates the desired capabilities of the fabric
interfaces. Supported capabilities are listed in the Capabilities section below.
mode : Operational modes supported by the application. See the Mode section below.
addr_format - address format : If specified, indicates the format of addresses referenced by the fabric
interfaces and data structures. Supported formats are listed in the Addressing formats section below.
src_addrlen - source address length : Indicates the length of the source address. This value must be > 0
if src_addr is non-NULL. This field will be ignored in hints if FI_SOURCE flag is set, or src_addr is
NULL.
dest_addrlen - destination address length : Indicates the length of the destination address. This value
must be > 0 if dest_addr is non-NULL. This field will be ignored in hints unless the node and service
parameters are NULL or FI_SOURCE flag is set, or if dst_addr is NULL.
src_addr - source address : If specified, indicates the source address. This field will be ignored in
hints if FI_SOURCE flag is set. On output a provider shall return an address that corresponds to the
indicated fabric, domain, node, and/or service fields. The format of the address is indicated by the
returned addr_format field. Note that any returned address is only used when opening a local endpoint.
The address is not guaranteed to be usable by a peer process.
dest_addr - destination address : If specified, indicates the destination address. This field will be
ignored in hints unless the node and service parameters are NULL or FI_SOURCE flag is set. If FI_SOURCE
is not specified, on output a provider shall return an address the corresponds to the indicated node
and/or service fields, relative to the fabric and domain. Note that any returned address is only usable
locally.
handle - provider context handle : References a provider specific handle. The use of this field is
operation specific. Unless its use is described for a given operation, the handle field must be NULL.
It is commonly used by applications that make use of connection-oriented endpoints. For other
applications, the field should usually be NULL.
This field is used when processing connection requests and responses. It is also used to inherit
endpoint's attributes. See fi_eq(3), fi_reject(3), and fi_endpoint(3) .
tx_attr - transmit context attributes : Optionally supplied transmit context attributes. Transmit
context attributes may be specified and returned as part of fi_getinfo. When provided as hints,
requested values of struct fi_tx_ctx_attr should be set. On output, the actual transmit context
attributes that can be provided will be returned. Output values will be greater than or equal to the
requested input values.
rx_attr - receive context attributes : Optionally supplied receive context attributes. Receive context
attributes may be specified and returned as part of fi_getinfo. When provided as hints, requested values
of struct fi_rx_ctx_attr should be set. On output, the actual receive context attributes that can be
provided will be returned. Output values will be greater than or or equal to the requested input values.
ep_attr - endpoint attributes : Optionally supplied endpoint attributes. Endpoint attributes may be
specified and returned as part of fi_getinfo. When provided as hints, requested values of struct
fi_ep_attr should be set. On output, the actual endpoint attributes that can be provided will be
returned. Output values will be greater than or equal to requested input values. See fi_endpoint(3) for
details.
domain_attr - domain attributes : Optionally supplied domain attributes. Domain attributes may be
specified and returned as part of fi_getinfo. When provided as hints, requested values of struct
fi_domain_attr should be set. On output, the actual domain attributes that can be provided will be
returned. Output values will be greater than or equal to requested input values. See fi_domain(3) for
details.
fabric_attr - fabric attributes : Optionally supplied fabric attributes. Fabric attributes may be
specified and returned as part of fi_getinfo. When provided as hints, requested values of struct
fi_fabric_attr should be set. On output, the actual fabric attributes that can be provided will be
returned. See fi_fabric(3) for details.
CAPABILITIES
Interface capabilities are obtained by OR-ing the following flags together. If capabilities in the hint
parameter are set to 0, the underlying provider will return the set of capabilities which are supported.
Otherwise, providers will return data matching the specified set of capabilities. Providers may indicate
support for additional capabilities beyond those requested when the use of expanded capabilities will not
adversely affect performance or expose the application to communication beyond that which was requested.
Applications may use this feature to request a minimal set of requirements, then check the returned
capabilities to enable additional optimizations.
FI_MSG : Specifies that an endpoint should support sending and receiving messages or datagrams. Message
capabilities imply support for send and/or receive queues. Endpoints supporting this capability support
operations defined by struct fi_ops_msg.
The caps may be used to specify or restrict the type of messaging operations that are supported. In the
absence of any relevant flags, FI_MSG implies the ability to send and receive messages. Applications can
use the FI_SEND and FI_RECV flags to optimize an endpoint as send-only or receive-only.
FI_RMA : Specifies that the endpoint should support RMA read and write operations. Endpoints supporting
this capability support operations defined by struct fi_ops_rma. In the absence of any relevant flags,
FI_RMA implies the ability to initiate and be the target of remote memory reads and writes. Applications
can use the FI_READ, FI_WRITE, FI_REMOTE_READ, and FI_REMOTE_WRITE flags to restrict the types of RMA
operations supported by an endpoint.
FI_TAGGED : Specifies that the endpoint should handle tagged message transfers. Tagged message transfers
associate a user-specified key or tag with each message that is used for matching purposes at the remote
side. Endpoints supporting this capability support operations defined by struct fi_ops_tagged. In the
absence of any relevant flags, FI_TAGGED implies the ability to send and receive tagged messages.
Applications can use the FI_SEND and FI_RECV flags to optimize an endpoint as send-only or receive-only.
FI_ATOMIC : Specifies that the endpoint supports some set of atomic operations. Endpoints supporting
this capability support operations defined by struct fi_ops_atomic. In the absence of any relevant
flags, FI_ATOMIC implies the ability to initiate and be the target of remote atomic reads and writes.
Applications can use the FI_READ, FI_WRITE, FI_REMOTE_READ, and FI_REMOTE_WRITE flags to restrict the
types of atomic operations supported by an endpoint.
FI_MULTICAST : Indicates that the endpoint support multicast data transfers. This capability must be
paired with at least one other data transfer capability, (e.g. FI_MSG, FI_SEND, FI_RECV, ...).
FI_NAMED_RX_CTX : Requests that endpoints which support multiple receive contexts allow an initiator to
target (or name) a specific receive context as part of a data transfer operation.
FI_DIRECTED_RECV : Requests that the communication endpoint use the source address of an incoming message
when matching it with a receive buffer. If this capability is not set, then the src_addr parameter for
msg and tagged receive operations is ignored.
FI_MULTI_RECV : Specifies that the endpoint must support the FI_MULTI_RECV flag when posting receive
buffers.
FI_SOURCE : Requests that the endpoint return source addressing data as part of its completion data.
This capability only applies to connectionless endpoints. Note that returning source address information
may require that the provider perform address translation and/or look-up based on data available in the
underlying protocol in order to provide the requested data, which may adversely affect performance. The
performance impact may be greater for address vectors of type FI_AV_TABLE.
FI_READ : Indicates that the user requires an endpoint capable of initiating reads against remote memory
regions. This flag requires that FI_RMA and/or FI_ATOMIC be set.
FI_WRITE : Indicates that the user requires an endpoint capable of initiating writes against remote
memory regions. This flag requires that FI_RMA and/or FI_ATOMIC be set.
FI_SEND : Indicates that the user requires an endpoint capable of sending message data transfers.
Message transfers include base message operations as well as tagged message functionality.
FI_RECV : Indicates that the user requires an endpoint capable of receiving message data transfers.
Message transfers include base message operations as well as tagged message functionality.
FI_REMOTE_READ : Indicates that the user requires an endpoint capable of receiving read memory operations
from remote endpoints. This flag requires that FI_RMA and/or FI_ATOMIC be set.
FI_REMOTE_WRITE : Indicates that the user requires an endpoint capable of receiving write memory
operations from remote endpoints. This flag requires that FI_RMA and/or FI_ATOMIC be set.
FI_RMA_EVENT : Requests that an endpoint support the generation of completion events when it is the
target of an RMA and/or atomic operation. This flag requires that FI_REMOTE_READ and/or FI_REMOTE_WRITE
be enabled on the endpoint.
FI_SHARED_AV : Requests or indicates support for address vectors which may be shared among multiple
processes.
FI_TRIGGER : Indicates that the endpoint should support triggered operations. Endpoints support this
capability must meet the usage model as described by fi_trigger.3.
FI_FENCE : Indicates that the endpoint support the FI_FENCE flag on data transfer operations. Support
requires tracking that all previous transmit requests to a specified remote endpoint complete prior to
initiating the fenced operation. Fenced operations are often used to enforce ordering between operations
that are not otherwise guaranteed by the underlying provider or protocol.
FI_LOCAL_COMM : Indicates that the endpoint support host local communication. This flag may be used in
conjunction with FI_REMOTE_COMM to indicate that local and remote communication are required. If neither
FI_LOCAL_COMM or FI_REMOTE_COMM are specified, then the provider will indicate support for the
configuration that minimally affects performance. Providers that set FI_LOCAL_COMM but not
FI_REMOTE_COMM, for example a shared memory provider, may only be used to communication between processes
on the same system.
FI_REMOTE_COMM : Indicates that the endpoint support communication with endpoints located at remote nodes
(across the fabric). See FI_LOCAL_COMM for additional details. Providers that set FI_REMOTE_COMM but
not FI_LOCAL_COMM, for example NICs that lack loopback support, cannot be used to communicate with
processes on the same system.
FI_SOURCE_ERR : Must be paired with FI_SOURCE. When specified, this requests that raw source addressing
data be returned as part of completion data for any address that has not been inserted into the local
address vector. Use of this capability may require the provider to validate incoming source address data
against addresses stored in the local address vector, which may adversely affect performance.
FI_RMA_PMEM : Indicates that the provider is 'persistent memory aware' and supports RMA operations to and
from persistent memory. Persistent memory aware providers must support registration of memory that is
backed by non- volatile memory, RMA transfers to/from persistent memory, and enhanced completion
semantics. This flag requires that FI_RMA be set. This capability is experimental.
Capabilities may be grouped into two general categories: primary and secondary. Primary capabilities
must explicitly be requested by an application, and a provider must enable support for only those primary
capabilities which were selected. Secondary capabilities may optionally be requested by an application.
If requested, a provider must support the capability or fail the fi_getinfo request (FI_ENODATA). A
provider may optionally report non-selected secondary capabilities if doing so would not compromise
performance or security.
Primary capabilities: FI_MSG, FI_RMA, FI_TAGGED, FI_ATOMIC, FI_MULTICAST, FI_NAMED_RX_CTX,
FI_DIRECTED_RECV, FI_READ, FI_WRITE, FI_RECV, FI_SEND, FI_REMOTE_READ, and FI_REMOTE_WRITE.
Secondary capabilities: FI_MULTI_RECV, FI_SOURCE, FI_RMA_EVENT, FI_SHARED_AV, FI_TRIGGER, FI_FENCE,
FI_LOCAL_COMM, FI_REMOTE_COMM, FI_SOURCE_ERR, FI_RMA_PMEM.
MODE
The operational mode bits are used to convey requirements that an application must adhere to when using
the fabric interfaces. Modes specify optimal ways of accessing the reported endpoint or domain.
Applications that are designed to support a specific mode of operation may see improved performance when
that mode is desired by the provider. It is recommended that providers support applications that disable
any provider preferred modes.
On input to fi_getinfo, applications set the mode bits that they support. On output, providers will
clear mode bits that are not necessary to achieve high-performance. Mode bits that remain set indicate
application requirements for using the fabric interfaces created using the returned fi_info. The set of
modes are listed below. If a NULL hints structure is provided, then the provider's supported set of
modes will be returned in the info structure(s).
FI_CONTEXT : Specifies that the provider requires that applications use struct fi_context as their per
operation context parameter for operations that generated full completions. This structure should be
treated as opaque to the application. For performance reasons, this structure must be allocated by the
user, but may be used by the fabric provider to track the operation. Typically, users embed struct
fi_context within their own context structure. The struct fi_context must remain valid until the
corresponding operation completes or is successfully canceled. As such, fi_context should NOT be
allocated on the stack. Doing so is likely to result in stack corruption that will be difficult to
debug. Users should not update or interpret the fields in this structure, or reuse it until the original
operation has completed. If an operation does not generate a completion (i.e. the endpoint was
configured with FI_SELECTIVE_COMPLETION and the operation was not initiated with the FI_COMPLETION flag)
then the context parameter is ignored by the fabric provider.The structure is specified in rdma/fabric.h.
FI_CONTEXT2 : This bit is similar to FI_CONTEXT, but doubles the provider's requirement on the size of
the per context structure. When set, this specifies that the provider requires that applications use
struct fi_context2 as their per operation context parameter. Or, optionally, an application can provide
an array of two fi_context structures (e.g. struct fi_context[2]) instead. The requirements for using
struct fi_context2 are identical as defined for FI_CONTEXT above.
FI_LOCAL_MR : The provider is optimized around having applications register memory for locally accessed
data buffers. Data buffers used in send and receive operations and as the source buffer for RMA and
atomic operations must be registered by the application for access domains opened with this capability.
This flag is defined for compatibility and is ignored if the application version is 1.5 or later and the
domain mr_mode is set to anything other than FI_MR_BASIC or FI_MR_SCALABLE. See the domain attribute
mr_mode fi_domain(3) and fi_mr(3).
FI_MSG_PREFIX : Message prefix mode indicates that an application will provide buffer space in front of
all message send and receive buffers for use by the provider. Typically, the provider uses this space to
implement a protocol, with the protocol headers being written into the prefix area. The contents of the
prefix space should be treated as opaque. The use of FI_MSG_PREFIX may improve application performance
over certain providers by reducing the number of IO vectors referenced by underlying hardware and
eliminating provider buffer allocation.
FI_MSG_PREFIX only applies to send and receive operations, including tagged sends and receives. RMA and
atomics do not require the application to provide prefix buffers. Prefix buffer space must be provided
with all sends and receives, regardless of the size of the transfer or other transfer options. The
ownership of prefix buffers is treated the same as the corresponding message buffers, but the size of the
prefix buffer is not counted toward any message limits, including inject.
Applications that support prefix mode must supply buffer space before their own message data. The size
of space that must be provided is specified by the msg_prefix_size endpoint attribute. Providers are
required to define a msg_prefix_size that is a multiple of 8 bytes. Additionally, applications may
receive provider generated packets that do not contain application data. Such received messages will
indicate a transfer size of that is equal to or smaller than msg_prefix_size.
The buffer pointer given to all send and receive operations must point to the start of the prefix region
of the buffer (as opposed to the payload). For scatter-gather send/recv operations, the prefix buffer
must be a contiguous region, though it may or may not be directly adjacent to the payload portion of the
buffer.
FI_ASYNC_IOV : Applications can reference multiple data buffers as part of a single operation through the
use of IO vectors (SGEs). Typically, the contents of an IO vector are copied by the provider into an
internal buffer area, or directly to the underlying hardware. However, when a large number of IOV
entries are supported, IOV buffering may have a negative impact on performance and memory consumption.
The FI_ASYNC_IOV mode indicates that the application must provide the buffering needed for the IO
vectors. When set, an application must not modify an IO vector of length > 1, including any related
memory descriptor array, until the associated operation has completed.
FI_RX_CQ_DATA : This mode bit only applies to data transfers that set FI_REMOTE_CQ_DATA. When set, a
data transfer that carries remote CQ data will consume a receive buffer at the target. This is true even
for operations that would normally not consume posted receive buffers, such as RMA write operations.
FI_NOTIFY_FLAGS_ONLY : This bit indicates that general completion flags may not be set by the provider,
and are not needed by the application. If specified, completion flags which simply report the type of
operation that completed (e.g. send or receive) may not be set. However, completion flags that are used
for remote notifications will still be set when applicable. See fi_cq(3) for details on which completion
flags are valid when this mode bit is enabled.
FI_RESTRICTED_COMP : This bit indicates that the application will only share completion queues and
counters among endpoints, transmit contexts, and receive contexts that have the same set of capability
flags.
ADDRESSING FORMATS
Multiple fabric interfaces take as input either a source or destination address parameter. This includes
struct fi_info (src_addr and dest_addr), CM calls (getname, getpeer, connect, join, and leave), and AV
calls (insert, lookup, and straddr). The fi_info addr_format field indicates the expected address format
for these operations.
A provider may support one or more of the following addressing formats. In some cases, a selected
addressing format may need to be translated or mapped into an address which is native to the fabric. See
fi_av(3).
FI_FORMAT_UNSPEC : FI_FORMAT_UNSPEC indicates that a provider specific address format should be selected.
Provider specific addresses may be protocol specific or a vendor proprietary format. Applications that
select FI_FORMAT_UNSPEC should be prepared to treat returned addressing data as opaque. FI_FORMAT_UNSPEC
targets apps which make use of an out of band address exchange. Applications which use FI_FORMAT_UNSPEC
may use fi_getname() to obtain a provider specific address assigned to an allocated endpoint.
FI_SOCKADDR : Address is of type sockaddr. The specific socket address format will be determined at run
time by interfaces examining the sa_family field.
FI_SOCKADDR_IN : Address is of type sockaddr_in (IPv4).
FI_SOCKADDR_IN6 : Address is of type sockaddr_in6 (IPv6).
FI_SOCKADDR_IB : Address is of type sockaddr_ib (defined in Linux kernel source)
FI_ADDR_PSMX : Address is an Intel proprietary format that is used with their PSMX (extended performance
scaled messaging) protocol.
FI_ADDR_GNI : Address is a Cray proprietary format that is used with their GNI protocol.
FI_ADDR_STR : Address is a formatted character string. The length and content of the string is address
and/or provider specific, but in general follows a URI model:
address_format[://[node][:[service][/[field3]...][?[key=value][&k2=v2]...]]]
Examples: - fi_sockaddr://10.31.6.12:7471 - fi_sockaddr_in6://[fe80::6:12]:7471 -
fi_sockaddr://10.31.6.12:7471?qos=3
Since the string formatted address does not contain any provider information, the prov_name field of the
fabric attribute structure should be used to filter by provider if necessary.
FLAGS
The operation of the fi_getinfo call may be controlled through the use of input flags. Valid flags
include the following.
FI_NUMERICHOST : Indicates that the node parameter is a numeric string representation of a fabric
address, such as a dotted decimal IP address. Use of this flag will suppress any lengthy name resolution
protocol.
FI_SOURCE : Indicates that the node and service parameters specify the local source address to associate
with an endpoint. If specified, either the node and/or service parameter must be non-NULL. This flag is
often used with passive endpoints.
FI_PROV_ATTR_ONLY : Indicates that the caller is only querying for what providers are potentially
available. All providers will return exactly one fi_info struct, regardless of whether that provider is
usable on the current platform or not. The returned fi_info struct will contain default values for all
members, with the exception of fabric_attr. The fabric_attr member will have the prov_name and
prov_version values filled in.
RETURN VALUE
fi_getinfo() returns 0 on success. On error, fi_getinfo() returns a negative value corresponding to
fabric errno. Fabric errno values are defined in rdma/fi_errno.h.
fi_allocinfo() returns a pointer to a new fi_info structure on success, or NULL on error. fi_dupinfo()
duplicates a single fi_info structure and all the substructures within it, returning a pointer to the new
fi_info structure on success, or NULL on error. Both calls require that the returned fi_info structure
be freed via fi_freeinfo().
ERRORS
FI_EBADFLAGS : The specified endpoint or domain capability or operation flags are invalid.
FI_ENOMEM : Indicates that there was insufficient memory to complete the operation.
FI_ENODATA : Indicates that no providers could be found which support the requested fabric information.
NOTES
If hints are provided, the operation will be controlled by the values that are supplied in the various
fields (see section on fiinfo_). Applications that require specific communication interfaces, domains,
capabilities or other requirements, can specify them using fields in hints. Libfabric returns a linked
list in info that points to a list of matching interfaces. info is set to NULL if there are no
communication interfaces or none match the input hints.
If node is provided, fi_getinfo will attempt to resolve the fabric address to the given node. If node is
not provided, fi_getinfo will attempt to resolve the fabric addressing information based on the provided
hints. The caller must call fi_freeinfo to release fi_info structures returned by fi_getinfo.
If neither node, service or hints are provided, then fi_getinfo simply returns the list all available
communication interfaces.
Multiple threads may call fi_getinfo simultaneously, without any requirement for serialization.
SEE ALSO
fi_open(3), fi_endpoint(3), fi_domain(3)
AUTHORS
OpenFabrics.
Libfabric Programmer's Manual 2018-02-13 fi_getinfo(3)