gNMI interface
A gRPC Network Management Interface (gNMI) is a gRPC based protocol that defines a service or set of services or RPC methods used to configure and retrieve data from network devices.
The SR Linux provides a gNMI-based RPC for the modification and retrieval of a configuration. Supported RPCs are:
get
set
subscribe
capabilities
Common notification messages
When the SR Linux gNMI process communicates data to a client, it uses common notification messages. Notification messages use the fields shown in the following table.
Field |
Definition |
---|---|
timestamp |
Time data was collected |
prefix |
Prefix applied to all path fields included in the notification message. The paths expressed within the message are formed by the concatenation of prefix + path. |
update |
List of update messages that indicate changes in the underlying data. Subfields are:
|
delete |
List of paths indicating the deletion of data nodes |
Timestamps
Timestamp values are represented in nanoseconds. The value is encoded as a signed 64-bit integer (int64).
Path prefix
A prefix can be specified to reduce the lengths of path fields within a message. The absolute path is a concatenation of the path elements representing the prefix and the list of path elements in the path field. For example:
Path Prefix
notification: <
timestamp: (timestamp) // timestamp as int64
prefix: <
elem: <
name: "a"
>
elem: <
name: "b"
key: <
key: "name"
value: "b1"
>
>
elem: <
name: "c"
>
>
update: <
path: <
elem: <
name: "d"
>
>
value: <
val: <
json_val: "AStringValue"
>
>
>
update: <
path: <
elem: <
name: "e"
>
>
val: <
json_val: 10042 // converted to int representation
>
>
>
Paths
Paths are represented according to gNMI path conventions. Each path is represented by an ordered list of PathElem messages, starting at the root node, and ending at the most specific path element (versus a single string with a ‟/” character separating each element). Each PathElem message contains the name of the node within the data tree, along with any associated keys and attributes that may be required. For example:
path: <
elem: <
name: "a"
>
elem: <
name: "e"
key: <
key: "key"
value: "k1"
>
>
elem: <
name: "f"
>
elem: <
name: "g"
>
>
Multiple paths are supported. Multiple notification messages are triggered in response to each path. For example:
path <
elem <
name: "interface"
key <
key: "name"
value: "mgmt0"
>
>
>
path <
elem <
name: "system"
>
>
type: 1
encoding: JSON_IETF
Data node values
The value of a data node can be the following:
scalar types, such as a string in the string_val field, int64 in the int_val field, unit64 in the uint_val field, bool in the bool_val field, bytes, and float in the float_val field
additional types used in some schema languages, such as decimal64 in the decimal_val field and ScalarArray in the leaflist_val field
structured data types
Structured data types
When structured data is sent in an update message, it is serialized according to supported encoding, as shown in the following table.
Data type |
Description |
Field |
---|---|---|
ASCII |
An ASCII encoded string |
ascii_val |
JSON_IETF |
A JSON encoded string using JSON encoding compatible with RFC 7951 |
json_ietf_val |
gNMI get RPC
The get RPC allows you to obtain a view of the existing state. A GetRequest message is sent to the target (SR Linux gNMI process gnmi_mgr) that specifies the data to retrieve. A GetResponse message is returned that reflects the values of specified leafs at the collection time.
The get RPC is recommended for retrieving small data sets. For larger data sets, the gNMI subscribe RPC is recommended, using the ONCE mode.
GetRequest message
A GetRequest message retrieves a view of data from the server. A Get RPC requests the server retrieve a subset of the data tree as specified by the paths included in the message and serializes this using the specified encoding.The GetRequest message uses the fields shown in the following table.
Field |
Definition |
---|---|
path |
Path (or set of paths) for the requested data view. Wildcards are permitted. |
type |
Type of data requested. Supported options are:
|
encoding |
Encoding that the target should use (ASCII or JSON_IETF). If not specified, JSON is the default. |
extension |
Repeated field to carry gNMI extensions |
GetResponse message
The GetResponse message uses the fields shown in the following table.
Field |
Definition |
---|---|
notification |
Set of notification messages for each path specified in the GetRequest. |
extension |
Repeated field to carry gNMI extensions |
gNMI set RPC
The set RPC allows you to modify an existing state. A SetRequest message is sent to the target (SR Linux gNMI process gnmi_mgr) that specifies the required modifications. The server deletes, replaces, and updates paths based on the order they are listed. For each operation designated in the SetRequest message, an UpdateResult message is included in the SetResponse message.
SetRequest message
The SetRequest message uses the fields shown in the following table.
Field |
Definition |
---|---|
prefix |
A specified prefix is applied to all defined paths within each field |
delete |
A set of paths to be removed from the data tree |
replace |
A set of update messages that defines content to replace |
update |
A set of update messages that defines content to update |
extension |
Repeated field to carry gNMI extensions |
An update message indicates changes to paths where a new value is required. Update messages contain the following:
path - the path of the element to be modified
value - a value to apply to the specified node
All changes to the state included in a SetRequest message are consider part of a transaction. Either all modifications are applied or changes are rolled back to reflect the original state. For changes to be applied together, they must be in a single SetRequest message.
For replace operations, the behavior of omitted data elements depends on whether they are non-default values (set by a previous SetRequest message) or unmodified defaults. When the replace operation omits values that have been previously set, they are deleted from the data tree. Otherwise, omitted data elements are created with their default values.
For update operations, only the value of the data elements explicitly specified are changed.
SetResponse message
The SetResponse message uses the fields shown in the following table.
Field |
Definition |
---|---|
prefix |
The prefix specified for all paths |
response |
A list of responses (one per operation). Each response consists of an UpdateResult message with the following:
|
extension |
Repeated field to carry gNMI extensions |
gNMI subscribe RPC
The subscribe RPC allows you to receive updates relating to the state of data instances. The user creates a subscription using the subscribe RPC with the desired subscription mode. The defined mode triggers how and when the data is sent to the client.
A SubscribeRequest message is sent to the target (SR Linux gNMI process gnmi_mgr) to request updates for one or more paths. A SubscribeReponse message is sent to the client over an established RPC.
SubscribeRequest message
The SubscribeRequest message uses the fields shown in the following table.
Field |
Definition |
---|---|
subscribe |
A SubscriptionList message specifying a new set of paths to subscribe to |
extension |
Repeated field to carry gNMI extensions |
Subscriptions are set once and cannot be modified. A new subscribe RPC call must be created for new paths. To end an existing subscription, the client must cancel the subscribe RPC that relates to the subscription.
SubscriptionList message
A SubscriptionList message indicates a set of paths where common subscription behavior is required. The SubscriptionList message uses the fields shown in the following table.
Field |
Definition |
---|---|
subscription |
A set of subscription messages indicating the paths associated with the subscription |
mode |
Type of subscription to create:
|
extension |
Repeated field to carry gNMI extensions |
ONCE subscriptions are one-time requests. A ONCE subscription is created by sending a SubscribeRequest message with the subscribe field containing a SubscriptionList, with the mode type set to ONCE. The relevant update messages are sent and the RPC channel is closed.
STEAM subscriptions are long-lived and transmit updates indefinitely. A STREAM subscription is created by sending a SubscribeRequest message with the subscribe field containing a SubscriptionList, with the mode type set to STREAM. The STEAM mode subscription message also specifies a mode.
ON_CHANGE - Data updates are only sent when the value of the data item changes.
SAMPLE - Data is sent at specified intervals as specified in the sample_interval field. The maximum sample rate is a 64-bit integer in nanoseconds and minimum is 0.
TARGET_DEFINED - The target determines the best subscription type to create on a per-leaf basis. For example, if the path specified refers to leaves that are event-driven, then an ON_CHANGE subscription may be created. If the data represents counters values, a SAMPLE subscription may be created.
SubscribeResponse message
The SubscribeResponse message uses the fields shown in the following table.
Field |
Definition |
---|---|
update OR sync_response |
A response field. Only one type can be specified per message:
|
extension |
Repeated field to carry gNMI extensions |
gNMI capabilities RPC
The capabilities RPC allows you to discover the capabilities of a specific gNMI server.
A CapabilityRequest message is sent by the client to request capability information from the target. The target replies with a CapabilityResponse message that includes its gNMI service version, the versioned data models it supports, and the supported data encodings.
This information is used in subsequent RPC messages from the client to indicate the set of models that the client uses, and the encoding used for data.
CapabilityRequest message
The CapabilityRequest message is sent by the client to request capability information from the target. The CapabilityRequest message carries a single repeated extension field which can be used to carry gNMI extensions.
CapabilityRequest message
message CapabilityRequest {
repeated gnmi_ext.Extension extension = 1;
}
CapabilityResponse message
A CapabilityResponse message is sent from the target and includes the following fields:
supported_models - a set of ModelData messages describing each model supported by the target
supported_encodings - an enumerated field describing the data encodings supported by the target (ASCII and JSON_IETF are supported)
gNMI_version - the version of the gNMI service supported by the target
encoding - a repeated field for gNMI extensions
CapabilityResponse message
message CapabilityResponse {
repeated ModelData supported_models = 1;
repeated Encoding supported_encodings = 2;
string gNMIversion = 3;
repeated gnmi_ext.Extension extension = 4;
}
Candidate mode
The gNMI uses its own private candidate that allows multiple users or services to make simultaneous changes to a configuration.
gNMI examples
Open source clients can be used to run GetRequests, SetRequests, subscriptions, and capabilities. The examples that follow show requests and responses using the following clients although any client that conforms to gNMI specifications can be used:
gnmi_get — used for simple GetRequests
gnmi_set — used for simple SetRequests
gnmi_cli — used for SubscribeRequests, and advanced GetRequests and SetRequests
gnmi_capabilities — used for CapabilityRequests
gnmi_get examples
The get gNMI-RPC allows you to retrieve state and configuration from a datastore. The following examples are shown:
-
get all request
-
get interface with wildcard key request
get all request
# gnmi_get -target_addr 172.18.0.6:50052 -insecure -xpath '/'
== getRequest:
path: <
>
encoding: JSON_IETF
Response (get all)
notification: <
timestamp: 1565672122888042050
update: <
path: <
>
val: <
json_ietf_val: "{\n \"srl_nokia-acl:acl\": {\n \"ipv4-
filter\" ---- snip ---- ]\n }\n}\n"
>
>
>
get interface with wildcard key request
# gnmi_get -target_addr 172.18.0.6:50052 -insecure -xpath
'/interface[name=mgmt0]/subinterface[index=*]'
== getRequest:
path: <
elem: <
name: "interface"
key: <
key: "name"
value: "mgmt0"
>
>
elem: <
name: "subinterface"
key: <
key: "index"
value: "*"
>
>
>
encoding: JSON_IETF
Response (get interface with wildcard key)
notification: <
timestamp: 1565671919030747121
update: <
path: <
elem: <
name: "srl_nokia-interfaces:interface"
key: <
key: "name"
value: "mgmt0"
>
>
>
val: <
json_ietf_val: "{\n \"name\": \"mgmt0\",\n \"subinterface\":
[\n {\n \"index\": 0,\n \"admin-state\": \"enable\",\n
\"ip-mtu\": 1500,\n \"ifindex\": 524288000,\n \"operstate\":
\"up\",\n \"last-change\": \"2019-08-
11T17:21:48.366Z\",\n \"ipv4\": {\n \"allow-directedbroadcast\":
false,\n \"dhcp-client\": true,\n
\"address\": [\n {\n \"ip-prefix\":in
\"172.18.0.6/24\",\n \"origin\": \"dhcp\"\n }\n
],\n \"srl_nokia-interfaces-nbr:arp\": {\n
\"timeout\": 14400,\n \"neighbor\": [\n {\n
\"ipv4-address\": \"172.18.0.1\",\n \"link-layeraddress\":
\"02:42:45:9D:DB:FC\",\n \"origin\":
\"dynamic\",\n \"expiration-time\": \"2019-08-
13T07:14:34.707Z\"\n },\n {\n
\"ipv4-address\": \"172.18.0.2\",\n \"link-layeraddress\":
\"02:42:AC:12:00:02\",\n \"origin\":
\"dynamic\",\n \"expiration-time\": \"2019-08-
13T05:17:51.893Z\"\n }\n ]\n }\n },\n
\"ipv6\": {\n \"dhcp-client\": true,\n \"address\": [\n
{\n \"ip-prefix\": \"2001:172:18::6/80\",\n
\"origin\": \"dhcp\",\n \"status\": \"preferred\"\n
},\n {\n \"ip-prefix\":
\"fe80::42:acff:fe12:6/64\",\n \"origin\": \"linklayer\",\
n \"status\": \"preferred\"\n }\n
],\n \"srl_nokia-interfaces-nbr:neighbor-discovery\": {\n
\"dup-addr-detect\": true,\n \"reachable-time\": 30,\n
\"stale-time\": 14400\n }\n },\n \"statistics\": {\n
\"in-pkts\": \"5136\",\n \"in-octets\": \"438953\",\n
\"in-error-pkts\": \"0\",\n \"in-discarded-pkts\": \"0\",\n
\"in-terminated-pkts\": \"5136\",\n \"in-terminated-octets\":
\"438953\",\n \"in-forwarded-pkts\": \"0\",\n \"inforwarded-
octets\": \"0\",\n \"out-forwarded-pkts\":
\"6062\",\n \"out-forwarded-octets\": \"2746613\",\n
\"out-error-pkts\": \"0\",\n \"out-discarded-pkts\": \"0\",\n
\"out-pkts\": \"6062\",\n \"out-octets\": \"2746520\"\n
},\n \"srl_nokia-qos:qos\": {\n \"input\": {\n
\"classifiers\": {\n \"ipv4-dscp\": \"default\",\n
\"ipv6-dscp\": \"default\",\n \"mpls-tc\": \"default\"\n
}\n }\n }\n }\n ]\n}\n"
>
>
>
gnmi_set examples
The set gNMI-RPC allows you to modify the state. The following examples are shown:
set delete request
set update all request
set delete request
# gnmi_set -target_addr 172.18.0.3:50052 -username admin -password
admin -insecure -delete /system/name/host-name
== setRequest:
delete: <
elem: <
name: "system"
>
elem: <
name: "name"
>
elem: <
name: "host-name"
>
>
Response (set delete)
response: <
path: <
elem: <
name: "system"
>
elem: <
name: "name"
>
elem: <
name: "host-name"
>
>
op: DELETE
>
timestamp: 1567203341816078044
set an update all request
# gnmi_set -target_addr 172.18.0.3:50052 -username admin -password
admin -insecure -update /system/name/host-name:replaced-host -replace
/system/name/domain-name:replaced-domain
== setRequest:
replace: <
path: <
elem: <
name: "system"
>
elem: <
name: "name"
>
elem: <
name: "domain-name"
>
>
val: <
string_val: "replaced-domain"
>
>
update: <
path: <
elem: <
name: "system"
>
elem: <
name: "name"
>
elem: <
name: "host-name"
>
>
val: <
string_val: "replaced-host"
>
>
Response (set update all)
response: <
path: <
elem: <
name: "system"
>
elem: <
name: "name"
>
elem: <
name: "domain-name"
>
>
op: REPLACE
response: <
path: <
elem: <
name: "system"
>
elem: <
name: "name"
>
elem: <
name: "host-name"
>
>
op: UPDATE
>
timestamp: 1567204165851469784
gnmi_cli examples
The cli gNMI-RPC allows you to subscribe and receive updates on the state of a data instance. The following examples are shown:
Subscribe - ONCE for all (one-time subscription) request
Subscribe - STREAM ON_CHANGE interface (long term subscription) request
In these examples, -qt
specifies the subscription type. ONCE mode is the default and therefore is not shown in the first example.
Subscribe ONCE for all request
# gnmi_cli -a 172.18.0.6:50052 -insecure -q '/'
Response (subscribe ONCE for all)
{
"acl": {
"ipv4-filter": {
"allow_sip_dip": {
"entry": {
"10": {
"action": {
"accept": {
"log": "false"
}
-- Snip –
}
Subscribe STREAM ON_CHANGE interface request
# gnmi_cli -a 172.18.0.6:50052 -insecure --qt streaming -q
'/interface[name=mgmt0]'
Response (Subscribe STREAM ON_CHANGE interface)
{
"interface": {
"mgmt0": {
"admin-state": "enable",
"ethernet": {
"flow-control": {
"receive": "false"
},
"hw-mac-address": "02:42:AC:12:00:06",
"statistics": {
"in-crc-errors": "0",
"in-fragment-frames": "0",
"in-jabber-frames": "0",
"in-mac-pause-frames": "0",
"in-oversize-frames": "0",
"out-mac-pause-frames": "0"
}
},
"ifindex": "524304383",
"last-change": "2019-08-30T18:44:45.490Z",
"mtu": "1514",
"oper-state": "up",
"statistics": {
"carrier-transitions": "1",
"in-broadcast-pkts": "5",
"in-errors": "0",
"in-fcs-errors": "0",
"in-multicast-pkts": "1356",
"in-octets": "612022",
"in-unicast-pkts": "4662",
"out-broadcast-pkts": "1",
"out-errors": "0",
"out-multicast-pkts": "456",
"out-octets": "2724476",
"out-unicast-pkts": "5505"
},
"subinterface": {
"0": {
"admin-state": "enable",
"ifindex": "524288000",
"ip-mtu": "1500",
"ipv4": {
"address": {
"172.18.0.6/24": {
"origin": "dhcp"
}
},
"allow-directed-broadcast": "false",
"arp": {
"neighbor": {
"172.18.0.1": {
"expiration-time": "2019-08-31T01:13:22.987Z",
"link-layer-address": "02:42:45:9D:DB:FC",
"origin": "dynamic"
},
"172.18.0.2": {
"expiration-time": "2019-08-30T22:44:54.422Z",
"link-layer-address": "02:42:AC:12:00:02",
"origin": "dynamic"
}
},
"timeout": "14400"
},
"dhcp-client": "true"
},
"ipv6": {
"address": {
"2001:172:18::6/80": {
"origin": "dhcp",
"status": "preferred"
},
"fe80::42:acff:fe12:6/64": {
"origin": "link-layer",
"status": "preferred"
}
},
"dhcp-client": "true",
"neighbor-discovery": {
"dup-addr-detect": "true",
"reachable-time": "30",
"stale-time": "14400"
}
},
"last-change": "2019-08-30T18:44:45.490Z",
"oper-state": "up",
"qos": {
"input": {
"classifiers": {
"ipv4-dscp": "default",
"ipv6-dscp": "default",
"mpls-tc": "default"
}
}
},
"statistics": {
"in-discarded-pkts": "0",
"in-error-pkts": "0",
"in-forwarded-octets": "0",
"in-forwarded-pkts": "0",
"in-octets": "404380",
"in-pkts": "4679",
"in-terminated-octets": "404380",
"in-terminated-pkts": "4679",
"out-discarded-pkts": "0",
"out-error-pkts": "0",
"out-forwarded-octets": "2409995",
"out-forwarded-pkts": "5511",
"out-octets": "2409995",
"out-pkts": "5511"
}
}
},
"vlan-tagging": "false"
}
}
{
"interface": {
"mgmt0": {
"statistics": {
"in-octets": "615366"
}
}
}
}
{
"interface": {
"mgmt0": {
"statistics": {
"in-unicast-pkts": "4693"
}
}
}
}
{
"interface": {
"mgmt0": {
"statistics": {
"out-octets": "2736287"
}
}
}
}
.
.
.
gnmi_capabilities example
The capabilities gNMI-RPC allows you to discover the capabilities of a specific gNMI server. The following example shows a request to obtain model, data encodings, and version for a specified server.
Request server capabilities for specified server
gnmi_capabilities -username admin -password admin --target_addr [172.18.0.8]:50264
Response (request server capabilities)
supported_models: <
name: "urn:srl_nokia/aaa:srl_nokia-aaa"
organization: "Nokia"
version: "2020-12-31"
>
supported_models: <
name: "urn:srl_nokia/aaa-types:srl_nokia-aaa-types"
organization: "Nokia"
version: "2019-11-30"
>
.
.
.
supported_encodings: JSON_IETF
supported_encodings: ASCII
supported_encodings: 45
supported_encodings: 44
supported_encodings: 46
supported_encodings: 47
gNMI_version: "0.7.0"