RESTCONF is an HTTP based protocol as defined in RFC 8040. RESTCONF standardizes a mechanism to allow Web applications to access the configuration data, state data, data-model-specific Remote Procedure Call (RPC) operations, and event notifications within a networking device.
RESTCONF uses HTTP methods to provide Create, Read, Update, Delete (CRUD) operations on a conceptual datastore containing YANG-defined data, which is compatible with a server that implements NETCONF datastores as defined in RFC 6241
Configuration data and state data are exposed as resources that can be retrieved with the GET method. Resources representing configuration data can be modified with the DELETE, PATCH, POST, and PUT methods. Data is encoded with either XML ( W3C.REC-xml-20081126) or JSON ( RFC 7951)
This chapter describes the NSO implementation and extension to or deviation from RFC 8040 respectively.
As of this writing, the server supports the following specifications:
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RFC 6020 - YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)
-
RFC 6021 - Common YANG Data Types
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RFC 6470 - NETCONF Base Notifications
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RFC 6536 - NETCONF Access Control Model
-
RFC 6991 - Common YANG Data Types
-
RFC 7950 - The YANG 1.1 Data Modeling Language
-
RFC 7951 - JSON Encoding of Data Modeled with YANG
-
RFC 7952 - Defining and Using metadata with YANG
-
RFC 8040 - RESTCONF Protocol
-
RFC 8072 - YANG Patch Media Type
-
RFC 8341 - Network Configuration Access Control Model
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RFC 8525 - YANG Library
-
RFC 8528 - YANG Schema Mount
-
I-D.draft-ietf-netconf-restconf-trace-ctx-headers-00 - RESTCONF Extension to support Trace Context Headers
In order to enable RESTCONF in NSO,
RESTCONF must be enabled in the
ncs.conf
configuration file. The web server configuration for RESTCONF
is shared with the WebUI's config, but you may define a separate RESTCONF
transport section.
The WebUI does not have to be enabled for RESTCONF to work.
Here is a minimal example of what is needed in the
ncs.conf
.
<restconf> <enabled>true</enabled> </restconf> <webui> <transport> <tcp> <enabled>true</enabled> <ip>0.0.0.0</ip> <port>8080</port> </tcp> </transport> </webui>
If you want to run RESTCONF with a different transport configuration than what the WebUI is using, you can specify a separate RESTCONF transport section.
<restconf> <enabled>true</enabled> <transport> <tcp> <enabled>true</enabled> <ip>0.0.0.0</ip> <port>8090</port> </tcp> </transport> </restconf> <webui> <enabled>false</enabled> <transport> <tcp> <enabled>true</enabled> <ip>0.0.0.0</ip> <port>8080</port> </tcp> </transport> </webui>
It is now possible to do a RESTCONF requests towards NSO. Any HTTP client can be used, in the following examples curl will be used. The example below will show how a typical RESTCONF request could look like.
# Note that the command is wrapped in several lines in order to fit. # # The switch '-i' will include any HTTP reply headers in the output # and the '-s' will suppress some superflous output. # # The '-u' switch specify the User:Password for login authentication. # # The '-H' switch will add a HTTP header to the request; in this case # an 'Accept' header is added, requesting the preferred reply format. # # Finally, the complete URL to the wanted resource is specified, # in this case the top of the configuration tree. # curl -is -u admin:admin \ -H "Accept: application/yang-data+xml" \ http://localhost:8080/restconf/data
In the rest of the document, in order to simplify the presentation, the example above will be expressed as:
GET /restconf/data Accept: application/yang-data+xml # Any reply with relevant headers will be displayed here! HTTP/1.1 200 OK
Note the HTTP return code (200 OK) in the example, which will be displayed together with any relevant HTTP headers returned and a possible body of content.
Send a RESTCONF query to get a representation of the top-level resource, which is accessible through the path: /restconf.
GET /restconf Accept: application/yang-data+xml HTTP/1.1 200 OK <restconf xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf"> <data/> <operations/> <yang-library-version>2019-01-04</yang-library-version> </restconf>
As can be seen from the result, the server exposes three additional resources:
-
data : this mandatory resource represents the combined configuration and state data resources that can be accessed by a client.
-
operations : this optional resource is a container that provides access to the data-model-specific RPC operations supported by the server.
-
yang-library-version : this mandatory leaf identifies the revision date of the "ietf-yang-library" YANG module that is implemented by this server. This resource exposes which YANG modules are in use by NSO system.
To fetch configuration, operational data, or both, from the server, a request to the data resource is made. In order to restrict the amount of returned data, the following example will prune the amount of output to only consist of the top most nodes. This is achieved by using the depth query argument as shown in the example below:
GET /restconf/data?depth=1 Accept: application/yang-data+xml <data xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf"> <yang-library xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library"/> <modules-state xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library"/> <dhcp xmlns="http://yang-central.org/ns/example/dhcp"/> <nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm"/> <netconf-state xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-monitoring"/> <restconf-state xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring"/> <aaa xmlns="http://tail-f.com/ns/aaa/1.1"/> <confd-state xmls="http://tail-f.com/yang/confd-monitoring"/> <last-logins xmlns="http://tail-f.com/yang/last-login"/> </data>
Let's assume we are interested in the dhcp/subnet resource in our configuration. In the following examples, assume it is defined by a corresponding Yang module that we have named dhcp.yang, looking like this:
> yanger -f tree examples.confd/restconf/basic/dhcp.yang module: dhcp +--rw dhcp +--rw max-lease-time? uint32 +--rw default-lease-time? uint32 +--rw subnet* [net] | +--rw net inet:ip-prefix | +--rw range! | | +--rw dynamic-bootp? empty | | +--rw low inet:ip-address | | +--rw high inet:ip-address | +--rw dhcp-options | | +--rw router* inet:host | | +--rw domain-name? inet:domain-name | +--rw max-lease-time? uint32
We can issue a HTTP GET request to retrieve the value content of the resource. In this case we find that there is no such data, which is indicated by the HTTP return code 204 No Content.
Note also how we have prefixed the dhcp:dhcp resource. This is how RESTCONF handle namespaces, where the prefix is the YANG module name and the namespace is as defined by the namespace statement in the YANG module.
We can now create the dhcp/subnet resource by sending a HTTP POST request + the data that we want to store. Note the Content-Type HTTP header, which indicates the format of the provided body. Two formats is supported: XML or JSON. In this example we are using XML, which is indicated by the Content-Type value: application/yang-data+xml.
POST /restconf/data/dhcp:dhcp Content-Type: application/yang-data+xml <subnet xmlns="http://yang-central.org/ns/example/dhcp" xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> <net>10.254.239.0/27</net> <range> <dynamic-bootp/> <low>10.254.239.10</low> <high>10.254.239.20</high> </range> <dhcp-options> <router>rtr-239-0-1.example.org</router> <router>rtr-239-0-2.example.org</router> </dhcp-options> <max-lease-time>1200</max-lease-time> </subnet> # If the resource is created, the server might respond as follows: HTTP/1.1 201 Created Location: http://localhost:8080/restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27
Note the HTTP return code (201 Created) indicating that the resource was successfully created. We also got a Location header, which always is returned in a reply to a successful creation of a resource, stating the resulting URI leading to the created resource.
If we now want to modify a part of our dhcp/subnet config, we can use the HTTP PATCH method, as shown below. Note that the URI used in the request need to be URL-encoded, such that the key value: 10.254.239.0/27 is URL-encoded as: 10.254.239.0%2F27.
Also, note the difference of the PATCH URI compared to the earlier POST request. With the latter, since the resource does not yet exist, we POST to the parent resource (dhcp:dhcp), while with the PATCH request we address the (existing) resource (10.254.239.0%2F27).
PATCH /restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27 <subnet> <max-lease-time>3333</max-lease-time> </subnet> # If our modification is successful, the server might respond as follows: HTTP/1.1 204 No Content
We can also replace the subnet with some new configuration. To do this we make use of the PUT HTTP method as shown below. Since the operation was successful and no body was returned, we will get a 204 No Content return code.
PUT /restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27 Content-Type: application/yang-data+xml <subnet xmlns="http://yang-central.org/ns/example/dhcp" xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> <net>10.254.239.0/27</net> <!-- ...config left out here... --> </subnet> # At success, the server will respond as follows: HTTP/1.1 204 No Content
To delete the subnet we make use of the DELETE HTTP method as shown below. Since the operation was successful and no body was returned, we will get a 204 No Content return code.
DELETE /restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27 HTTP/1.1 204 No Content
RESTCONF makes it possible to specify where the RESTCONF API is located, as described in the RESTCONF RFC 8040.
As per default, the RESTCONF API root is /restconf.
Typically there is no need to change the default value although it is
possible to change this by configuring the RESTCONF API root in the
ncs.conf
file as:
<restconf> <enabled>true</enabled> <root-resource>my_own_restconf_root</root-resource> </restconf>
The RESTCONF API root will now be /my_own_restconf_root.
A client may discover the root resource by getting the /.well-known/host-meta resource as shown in the example below:
The client might send the following: GET /.well-known/host-meta Accept: application/xrd+xml The server might respond as follows: HTTP/1.1 200 OK <XRD xmlns='http://docs.oasis-open.org/ns/xri/xrd-1.0'> <Link rel='restconf' href='/restconf'/> </XRD>
Note
In this document, all examples will assume the RESTCONF API root to be /restconf.
A RESTCONF capability is a set of functionality that supplements the base RESTCONF specification. The capability is identified by a uniform resource identifier (URI). The RESTCONF server includes a capability URI leaf-list entry identifying each supported protocol feature. This include the basic-mode default-handling mode, optional query parameters and may also include other, NSO specific, capability URIs.
To view currently enabled capabilities, use the ietf-restconf-monitoring YANG model, which is available as: /restconf/data/ietf-restconf-monitoring:restconf-state .
GET /restconf/data/ietf-restconf-monitoring:restconf-state Host: example.com Accept: application/yang-data+xml <restconf-state xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring" xmlns:rcmon="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring"> <capabilities> <capability> urn:ietf:params:restconf:capability:defaults:1.0?basic-mode=explicit </capability> <capability>urn:ietf:params:restconf:capability:depth:1.0</capability> <capability>urn:ietf:params:restconf:capability:fields:1.0</capability> <capability>urn:ietf:params:restconf:capability:with-defaults:1.0</capability> <capability>urn:ietf:params:restconf:capability:filter:1.0</capability> <capability>urn:ietf:params:restconf:capability:replay:1.0</capability> <capability>http://tail-f.com/ns/restconf/collection/1.0</capability> <capability>http://tail-f.com/ns/restconf/query-api/1.0</capability> <capability>http://tail-f.com/ns/restconf/partial-response/1.0</capability> <capability>http://tail-f.com/ns/restconf/unhide/1.0</capability> <capability>urn:ietf:params:xml:ns:yang:traceparent:1.0</capability> <capability>urn:ietf:params:xml:ns:yang:tracestate:1.0</capability> </capabilities> </restconf-state>
This Capability identifies the basic-mode default-handling mode that is used by the server for processing default leafs in requests for data resources.
The capability URL will contain a query parameter named basic-mode which value tells us what the default behaviour of the RESTCONF server is when it returns a leaf. The possible values are shown in the table below:
Value | Description |
---|---|
report-all | Values set to the YANG default value are reported. |
trim | Values set to the YANG default value are not reported. |
explicit | Values that has been set by a client to the YANG default value will be reported. |
The values presented in the table above can also be used by the Client together with the with-defaults query parameter in order to override the default RESTCONF server behaviour. Added to these values, the Client can also use the report-all-tagged value.
Value | Description |
---|---|
report-all-tagged | Works as the report-all but a default value will include a XML/JSON attribute to indicate that the value is in fact a default value. |
Refering back to the example: Example 16, “NSO RESTCONF capabilities”, where the RESTCONF server returned the default capability:
urn:ietf:params:restconf:capability:defaults:1.0?basic-mode=explicit
It tells us that values that has been set by a client to the YANG default value will be reported but default values that has not been set by the Client will not be returned. Again, note that this is the default RESTCONF server behaviour which can be overridden by the Client by using the with-defaults query argument.
A set of optional RESTCONF Capability URIs are defined to identify the specific query parameters that are supported by the server. They are defined as:
Name | URI |
---|---|
depth | urn:ietf:params:restconf:capability:depth:1.0 |
fields | urn:ietf:params:restconf:capability:fields:1.0 |
filter | urn:ietf:params:restconf:capability:filter:1.0 |
replay | urn:ietf:params:restconf:capability:replay:1.0 |
with.defaults | urn:ietf:params:restconf:capability:with.defaults:1.0 |
For a description of the query parameter functionality see the chapter the section called “Query Parameters” .
Each RESTCONF operation allows zero or more query parameters to be present in the request URI. Query parameters can be given in any order, but can appear at most once. Supplying query parameters when invoking RPCs and actions is not supported, if supplied the response will be 400 (Bad Request) and the error-app-tag will be set to invalid-value. However, the query parameters trace-id and unhide are exempted from this rule and supported for RPC and action invocation. The defined query parameters and in what type of HTTP request they can be used are shown in the table below:
Name | Method | Description |
---|---|---|
content | GET,HEAD | Select config and/or non-config data resources. |
depth | GET,HEAD | Request limited subtree depth in the reply content. |
fields | GET,HEAD | Request a subset of the target resource contents. |
exclude | GET,HEAD | Exclude a subset of the target resource contents. |
filter | GET,HEAD | Boolean notification filter for event stream resources. |
insert | POST,PUT | Insertion mode for ordered-by user data resources |
point | POST,PUT | Insertion point for ordered-by user data resources |
start-time | GET,HEAD | Replay buffer start time for event stream resources. |
stop-time | GET,HEAD | Replay buffer stop time for event stream resources. |
with-defaults | GET,HEAD | Control the retrieval of default values. |
with-origin | GET | Include the "origin" metadata annotations, as detailed in the NMDA. |
The content query parameter controls if configuration, non-configuration or both types of data should be returned.
The allowed values are:
Value | Description |
---|---|
config | Return only configuration descendant data nodes. |
nonconfig | Return only non-configuration descendant data nodes. |
all | Return all descendant data nodes. |
The depth query parameter is used to limit the depth of subtrees returned by the server. Data nodes with a value greater than the depth parameter are not returned in a response for a GET request.
The value of the depth parameter is either an integer between 1 and 65535 or the string "unbounded". The default value is: "unbounded".
The fields query parameter is used to optionally identify data nodes within the target resource to be retrieved in a GET method. The client can use this parameter to retrieve a subset of all nodes in a resource.
For a full definition of the fields value can be constructed, refer to the RFC 8040, Section 4.8.3.
NOTE: The fields query parameter cannot be used together with the exclude query parameter. This will result in an error.
GET /restconf/data/dhcp:dhcp?fields=subnet/range(low;high) Accept: application/yang-data+xml HTTP/1.1 200 OK <dhcp xmlns="http://yang-central.org/ns/example/dhcp" \ xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> <subnet> <range> <low>10.254.239.10</low> <high>10.254.239.20</high> </range> </subnet> <subnet> <range> <low>10.254.244.10</low> <high>10.254.244.20</high> </range> </subnet> </dhcp>
The exclude query parameter is used to optionally exclude data nodes within the target resource from being retrieved with a GET request. The client can use this parameter to exclude a subset of all nodes in a resource. Only nodes below the target resource can be excluded, not the target resource itself.
NOTE: The exclude query parameter cannot be used together with the fields query parameter. This will result in an error.
The exclude query parameter uses the same syntax and have the same restrictions as the fields query parameter, as defined in RFC 8040, Section 4.8.3.
Selecting multiple nodes to exclude can be done the same way as for the fields query parameter, as described in RFC 8040, Section 4.8.3.
exclude using wildcards (*) will exclude all child nodes of the node. For lists and presence containers the parent node will be visible in the output but not it's children, i.e. it will be displayed as an empty node. For non-presence containers the parent node will be excluded from the output as well.
exclude can be used together with the depth query parameter to limit the depth of the output. In contrast to fields, where depth is counted from the node selected by fields, for exclude the depth is counted from the target resource, and the nodes are excluded if depth is deep enough to encounter an excluded node.
When exclude is not used:
GET /restconf/data/dhcp:dhcp/subnet Accept: application/yang-data+xml HTTP/1.1 200 OK <subnet xmlns="http://yang-central.org/ns/example/dhcp" xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> <net>10.254.239.0/27</net> <range> <dynamic-bootp/> <low>10.254.239.10</low> <high>10.254.239.20</high> </range> <dhcp-options> <router>rtr-239-0-1.example.org</router> <router>rtr-239-0-2.example.org</router> </dhcp-options> <max-lease-time>1200</max-lease-time> </subnet>
Using exclude to exclude "low" and "high" from "range", note that these are absent in the output:
GET /restconf/data/dhcp:dhcp/subnet?exclude=range(low;high) Accept: application/yang-data+xml HTTP/1.1 200 OK <subnet xmlns="http://yang-central.org/ns/example/dhcp" xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> <net>10.254.239.0/27</net> <range> <dynamic-bootp/> </range> <dhcp-options> <router>rtr-239-0-1.example.org</router> <router>rtr-239-0-2.example.org</router> </dhcp-options> <max-lease-time>1200</max-lease-time> </subnet>
These query parameters are only allowed on an event stream resource and is further described in the chapter: the section called “Streams” .
The insert query parameters is used to specify how a resource should be inserted within an ordered-by user list. The allowed values are as shown in the table below.
Value | Description |
---|---|
first | Insert the new data as the new first entry. |
last | Insert the new data as the new last entry. This is the default value. |
before | Insert the new data before the insertion point, as specified by the value of the point parameter. |
after | Insert the new data after the insertion point, as specified by the value of the point parameter. |
This parameter is only valid if the target data represents a YANG list or leaf-list that is ordered-by user. In the example below we will insert a new router value, first, in the ordered-by user leaf-list of dhcp-options/router values. Remember that the default behaviour is for new entries to be inserted last in an ordered-by user leaf-list.
# Note: we have to split the POST line in order to fit the page POST /restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27/dhcp-options?\ insert=first Content-Type: application/yang-data+xml <router>one.acme.org</router> # If the resource is created, the server might respond as follows: HTTP/1.1 201 Created Location /restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27/dhcp-options/\ router=one.acme.org
To verify that the router value really ended up first:
GET /restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27/dhcp-options Accept: application/yang-data+xml HTTP/1.1 200 OK <dhcp-options xmlns="http://yang-central.org/ns/example/dhcp" xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> <router>one.acme.org</router> <router>rtr-239-0-1.example.org</router> <router>rtr-239-0-2.example.org</router> </dhcp-options>
The point query parameters is used to specify the insertion point for a data resource that is being created or moved within an ordered-by user list or leaf-list. In the example below we will insert the new router value: two.acme.org, after the first value: one.acme.org in the ordered-by user leaf-list of dhcp-options/router values.
# Note: we have to split the POST line in order to fit the page POST /restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27/dhcp-options?\ insert=after&\ point=/dhcp:dhcp/subnet=10.254.239.0%2F27/dhcp-options/router=one.acme.org Content-Type: application/yang-data+xml <router>two.acme.org</router> # If the resource is created, the server might respond as follows: HTTP/1.1 201 Created Location /restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27/dhcp-options/\ router=one.acme.org
To verify that the router value really ended up after our insertion point:
GET /restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27/dhcp-options Accept: application/yang-data+xml HTTP/1.1 200 OK <dhcp-options xmlns="http://yang-central.org/ns/example/dhcp" xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> <router>one.acme.org</router> <router>two.acme.org</router> <router>rtr-239-0-1.example.org</router> <router>rtr-239-0-2.example.org</router> </dhcp-options>
There are additional NSO query parameters available for the RESTCONF API. These additional query parameters are described below.
Name | Methods | Description |
---|---|---|
dry-run | POST, PUT, PATCH, DELETE | Validate and display the configuration changes but do not perform the actual commit. Neither CDB nor the devices are affected. Instead the effects that would have taken place is showed in the returned output. Possible values are: xml, cli and native. The value used specify in what format we want the returned diff to be. |
dry-run-reverse | POST, PUT, PATCH, DELETE | Used together with the dry-run=native parameter to display the device commands for getting back to the current running state in the network if the commit is successfully executed. Beware that if any changes are done later on the same data the reverse device commands returned are invalid. |
no-networking | POST, PUT, PATCH, DELETE | Do not send any data to the devices. This is a way to manipulate CDB in NSO without generating any southbound traffic. |
no-out-of-sync-check | POST, PUT, PATCH, DELETE | Continue with the transaction even if NSO detects that a device's configuration is out of sync. Can't be used together with no-overwrite. |
no-overwrite | POST, PUT, PATCH, DELETE | NSO will check that the data that should be modified has not changed on the device compared to NSO's view of the data. Can't be used together with no-out-of-sync-check. |
no-revision-drop | POST, PUT, PATCH, DELETE | NSO will not run its data model revision algorithm, which requires all participating managed devices to have all parts of the data models for all data contained in this transaction. Thus, this flag forces NSO to never silently drop any data set operations towards a device. |
no-deploy | POST, PUT, PATCH, DELETE | Commit without invoking the service create method, i.e, write the service instance data without activating the service(s). The service(s) can later be re-deployed to write the changes of the service(s) to the network. |
reconcile | POST, PUT, PATCH, DELETE | Reconcile the service data. All data which existed before the service was created will now be owned by the service. When the service is removed that data will also be removed. In technical terms the reference count will be decreased by one for everything which existed prior to the service. If manually configured data exists below in the configuration tree that data is kept unless the option discard-non-service-config is used. |
use-lsa | POST, PUT, PATCH, DELETE |
Force handling of the LSA nodes as such. This flag tells
NSO to propagate applicable commit flags and actions
to the LSA nodes without applying them on the upper
NSO node itself. The commit flags affected are
dry-run ,
no-networking ,
no-out-of-sync-check ,
no-overwrite and
no-revision-drop .
|
no-lsa | POST, PUT, PATCH, DELETE | Do not handle any of the LSA nodes as such. These nodes will be handled as any other device. |
commit-queue | POST, PUT, PATCH, DELETE |
Commit the transaction data to the commit queue.
Possible values are: async,
sync and bypass.
If the async value is set the
operation returns successfully if the transaction data has
been successfully placed in the queue.
The sync value will cause the
operation to not return until the transaction data has been
sent to all devices, or a timeout occurs.
The bypass value means that if
/devices/global-settings/commit-queue/enabled-by-default
is true the data in this
transaction will bypass the commit queue.
The data will be written directly to the devices.
|
commit-queue-atomic | POST, PUT, PATCH, DELETE | Sets the atomic behaviour of the resulting queue item. Possible values are: true and false. If this is set to false, the devices contained in the resulting queue item can start executing if the same devices in other non-atomic queue items ahead of it in the queue are completed. If set to true, the atomic integrity of the queue item is preserved. |
commit-queue-block-others | POST, PUT, PATCH, DELETE | The resulting queue item will block subsequent queue items, which use any of the devices in this queue item, from being queued. |
commit-queue-lock | POST, PUT, PATCH, DELETE |
Place a lock on the resulting queue item. The queue
item will not be processed until it has been unlocked,
see the actions unlock and
lock in
/devices/commit-queue/queue-item .
No following queue items, using the same devices, will
be allowed to execute as long as the lock is in place.
|
commit-queue-tag | POST, PUT, PATCH, DELETE | The value is a user defined opaque tag. The tag is present in all notifications and events sent referencing the specific queue item. |
commit-queue-timeout | POST, PUT, PATCH, DELETE | Specifies a maximum number of seconds to wait for completion. Possible values are infinity or a positive integer. If the timer expires, the transaction is kept in the commit-queue, and the operation returns successfully. If the timeout is not set, the operation waits until completion indefinitely. |
commit-queue-error-option | POST, PUT, PATCH, DELETE |
The error option to use. Depending on the selected
error option NSO will store the reverse of the
original transaction to be able to undo the
transaction changes and get back to the previous
state. This data is stored in the
Read about error recovery in the section called “Commit Queue” in User Guide for a more detailed explanation. |
trace-id | POST, PUT, PATCH, DELETE | Use the provided trace id as part of the log messages emitted while processing. If no trace id is given, NSO is going to generate and assign a trace id to the processing. The trace-id query parameter can also be used with RPCs and actions to relay a trace-id from northbound requests. The trace-id will be included in the X-Cisco-NSO-Trace-ID header in the response. NOTE! trace-id as a query parameter is deprecated from NSO version 6.3. Capabilities within Trace Context will provide support for trace-id, see the section called “Trace Context” |
limit | GET | Used by the client to specify a limited set of list entries to retrieve. See The value of the limit parameter is either an integer greater than or equal to 1, or the string unbounded. The string unbounded is the default value. the section called “Partial Responses” for an example. |
offset | GET | Used by the client to specify the number of list elements to skip before returning the requested set of list entries. See The value of the "offset" parameter is an integer greater than or equal to 0. The default value is 0. the section called “Partial Responses” for an example. |
rollback-comment | POST, PUT, PATCH, DELETE | Used to specify a comment to be attached to the Rollback File that will be created as a result of the POST operation. This assume that Rollback File handling is enabled. |
rollback-label | POST, PUT, PATCH, DELETE | Used to specify a label to be attached to the Rollback File that will be created as a result of the POST operation. This assume that Rollback File handling is enabled. |
rollback-id | POST, PUT, PATCH, DELETE | Return the rollback id in the response if a rollback file was created during this operation. This requires rollbacks to be enabled in the NSO to take effect. |
with-service-meta-data | GET | Include FASTMAP attributes such as backpointers and reference counters in the reply. These are typically internal to NSO and thus not shown by default. |
Two edit collision detection and prevention mechanisms are provided in RESTCONF for the datastore resource: a timestamp and an entity-tag. Any change to configuration data resources will update the timestamp and entity-tag of the datastore resource. This makes it possible for a client to apply precondition HTTP headers to a request.
The NSO RESTCONF API honor the following HTTP response headers: Etag and Last-Modified, and the following request headers: If-Match, If-None-Match, If-Modified-Since and If-Unmodified-Since.
-
Etag
: This header will contain an entity-tag which is an opaque string representing the latest transaction identifier in the NSO database. This header is only available for the running datastore and hence, only relates to configuration data (non-operational). -
Last-Modified
: This header contains the timestamp for the last modification made to the NSO database. This timestamp can be used by a RESTCONF client in subsequent requests, within the If-Modified-Since and If-Unmodified-Since header fields. This header is only available for the running datastore and hence, only relates to configuration data (non-operational).
-
If-None-Match
: This header evaluates to true if the supplied value does not match the latest Etag entity-tag value. If evaluated to false an error response with status 304 (Not Modified) will be sent with no body. This header carry only meaning if the entity-tag of the Etag response header has previously been acquired.The usage of this could for example be a HEAD operation to get information if the data has changed since last retrieval.
-
If-Modified-Since
: This request-header field is used with a HTTP method to make it conditional, i.e if the requested resource has not been modified since the time specified in this field, the request will not be processed by the RESTCONF server; instead, a 304 (Not Modified) response will be returned without any message-body.Usage of this is for instance for a GET operation to retrieve the information if (and only if) the data has changed since last retrieval. Thus, this header should use the value of a Last-Modified response header that has previously been acquired.
-
If-Match
: This header evaluates to true if the supplied value matches the latest Etag value. If evaluated to false an error response with status 412 (Precondition Failed) will be sent with no body. This header carry only meaning if the entity-tag of the Etag response header has previously been acquired.The usage of this can be in case of a PUT, where If-Match can be used to prevent the lost update problem. It can check if the modification of a resource that the user wants to upload will not override another change that has been done since the original resource was fetched.
-
If-Unmodified-Since
: This header evaluates to true if the supplied value has not been last modified after the given date. If the resource has been modified after the given date, the response will be a 412 (Precondition Failed) error with no body. This header carry only meaning if theLast-Modified
response header has previously been acquired.The usage of this can be the case of a POST, where editions are rejected if the stored resource has been modified since the original value was retrieved.
If rollbacks have been enabled in the configuration using the rollback-id query parameter, the fixed id of the rollback file creating during an operation is returned in the results. The below examples shows creation of a new resource and removal of that resource using the rollback created in the first step.
POST /restconf/data/dhcp:dhcp?rollback-id=true Content-Type: application/yang-data+xml <subnet xmlns="http://yang-central.org/ns/example/dhcp"> <net>10.254.239.0/27</net> </subnet> HTTP/1.1 201 Created Location: http://localhost:8008/restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27 <result xmlns="http://tail-f.com/ns/tailf-restconf"> <rollback> <id>10002</id> </rollback> </result>
Then using the fixed id returned above as input to the
apply-rollback-file action:
POST /restconf/data/tailf-rollback:rollback-files/apply-rollback-file Content-Type: application/yang-data+xml <input xmlns="http://tail-f.com/ns/rollback"> <fixed-number>10002</fixed-number> </input> HTTP/1.1 204 No Content
The RESTCONF protocol supports YANG-defined event notifications. The solution preserves aspects of NETCONF event notifications [RFC5277] while utilizing the Server-Sent Events, W3C.REC-eventsource-20150203, transport strategy.
RESTCONF event notification streams are described in Sections 6 and 9.2 of RFC 8040, where also notification examples can be found.
RESTCONF event notification is a way for RESTCONF clients to retrieve notifications for different event streams. Event streams configured in NSO can be subscribed to using different channels such as the RESTCONF or the NETCONF channel.
More information on how to define a new notification event using Yang is described in RFC 6020.
How to add and configure notifications support in NSO is described in
the
ncs.conf(3)
man page.
The design of RESTCONF event notification is inspired by how NETCONF event notification is designed. More information on NETCONF event notification can be found in RFC 5277.
For this example we will define a notification stream, named
interface in the
ncs.conf
configuration file
as shown below.
We also enable the builtin replay store which means that NSO automatically stores all notifications on disk, ready to be replayed should a RESTCONF event notification subscriber ask for logged notifications. The replay store uses a set of wrapping log files on disk (of a certain number and size) to store the notifications.
<notifications> <eventStreams> <stream> <name>interface</name> <description>Example notifications</description> <replaySupport>true</replaySupport> <builtinReplayStore> <dir>./</dir> <maxSize>S1M</maxSize> <maxFiles>5</maxFiles> </builtinReplayStore> </stream> </eventStreams> </notifications>
To view the currently enabled event streams, use the ietf-restconf-monitoring YANG model. The streams are available under the /restconf/data/ietf-restconf-monitoring:restconf-state/streams container.
GET /restconf/data/ietf-restconf-monitoring:restconf-state/streams Accept: application/yang-data+xml HTTP/1.1 200 OK <streams xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring" xmlns:rcmon="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring"> ...other streams info removed here for brewity reason... <stream> <name>interface</name> <description>Example notifications</description> <replay-support>true</replay-support> <replay-log-creation-time> 2020-05-04T13:45:31.033817+00:00 </replay-log-creation-time> <access> <encoding>xml</encoding> <location>https://localhost:8888/restconf/streams/interface/xml</location> </access> <access> <encoding>json</encoding> <location>https://localhost:8888/restconf/streams/interface/json</location> </access> </stream> </streams>
Note the URL value we get in the location element in the example above. This URL should be used when subscribing to the notification events as is shown in the next example.
RESTCONF clients can determine the URL for the subscription resource (to receive notifications) by sending an HTTP GET request for the location leaf with the stream list entry. The value returned by the server can be used for the actual notification subscription.
The client will send an HTTP GET request for the (location) URL returned by the server with the Accept type text/event-stream as shown in the example below. Note that this request works like a long polling request which means that the request will not return. Instead, server side notifications will be sent to the client where each line of the notification will be prepended with data: .
GET /restconf/streams/interface/xml Accept: text/event-stream ...NOTE: we will be waiting here until a notification is generated... HTTP/1.1 200 OK Content-Type: text/event-stream data: <notification xmlns='urn:ietf:params:xml:ns:netconf:notification:1.0'> data: <eventTime>2020-05-04T13:48:02.291816+00:00</eventTime> data: <link-up xmlns='http://tail-f.com/ns/test/notif'> data: <if-index>2</if-index> data: <link-property> data: <newly-added/> data: <flags>42</flags> data: <extensions> data: <name>1</name> data: <value>3</value> data: </extensions> data: <extensions> data: <name>2</name> data: <value>4668</value> data: </extensions> data: </link-property> data: </link-up> data: </notification> ...NOTE: we will still be waiting here for more notifications to come...
Since we have enabled the replay store, we can ask the server to replay any notifications generated since the specific date we specify. After those notifications have been delivered we will continue waiting for new notifications to be generated.
GET /restconf/streams/interface/xml?start-time=2007-07-28T15%3A23%3A36Z Accept: text/event-stream HTTP/1.1 200 OK Content-Type: text/event-stream data: ...any existing notification since given date will be delivered here... ...NOTE: when all notifications are delivered, we will be waiting here for more...
Errors occurring during streaming of events will be reported as Server-Sent Events (SSE) comments as described in W3C.REC-eventsource-20150203 as shown in the example below.
: error: notification stream NETCONF temporarily unavailable
RFC 8040, Section 3.7 describes retrieval of YANG modules used by the
server via the RPC operation get-schema
. The YANG source is
made available by NSO in two ways: compiled into
the fxs file or put in the loadPath.
See the section called “Monitoring of the NETCONF Server”.
The example below show how to list the available Yang modules. Since we are interested by the dhcp module we only show that part of the output:
GET /restconf/data/ietf-yang-library:modules-state Accept: application/yang-data+xml HTTP/1.1 200 OK <modules-state xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library" xmlns:yanglib="urn:ietf:params:xml:ns:yang:ietf-yang-library"> <module-set-id>f4709e88d3250bd84f2378185c2833c2</module-set-id> <module> <name>dhcp</name> <revision>2019-02-14</revision> <schema>http://localhost:8080/restconf/tailf/modules/dhcp/2019-02-14</schema> <namespace>http://yang-central.org/ns/example/dhcp</namespace> <conformance-type>implement</conformance-type> </module> ...rest of the output removed here... </modules-state>
We can now retrieve the dhcp Yang module
via the URL we got in the schema leaf
of the reply. Note that the actual URL may point anywhere.
The URL is configured by the schemaServerUrl
setting in the
ncs.conf
file.
GET /restconf/tailf/modules/dhcp/2019-02-14 HTTP/1.1 200 OK module dhcp { namespace "http://yang-central.org/ns/example/dhcp"; prefix dhcp; import ietf-yang-types { ...the rest of the Yang module removed here...
The NSO RESTCONF API also support the YANG Patch Media Type, as defined in RFC 8072.
A YANG Patch is an ordered list of edits that are applied to the target datastore by the RESTCONF server. A YANG Patch request is sent as a HTTP PATCH request containing a body describing the edit operations to be performed. The format of the body is defined in the RFC 8072.
Refering to the dhcp Yang model in our Getting Started chapter; we will show how to use YANG Patch to achieve the same result but with fewer amount of requests.
In order to create the resources, we send a HTTP PATCH request where the Content-Type indicates that the body in the request consists of a Yang-Patch message. Our Yang-Patch request will initiate two edit operations where each operation will create a new subnet. In contrast, compare this with using "plain" RESTCONF where we would have needed two POST requests to achieve the same result.
PATCH /restconf/data/dhcp:dhcp Accept: application/yang-data+xml Content-Type: application/yang-patch+xml <yang-patch xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-patch"> <patch-id>add-subnets</patch-id> <edit> <edit-id>add-subnet-239</edit-id> <operation>create</operation> <target>/subnet=10.254.239.0%2F27</target> <value> <subnet xmlns="http://yang-central.org/ns/example/dhcp" \ xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> <net>10.254.239.0/27</net> ...content removed here for brevity... <max-lease-time>1200</max-lease-time> </subnet> </value> </edit> <edit> <edit-id>add-subnet-244</edit-id> <operation>create</operation> <target>/subnet=10.254.244.0%2F27</target> <value> <subnet xmlns="http://yang-central.org/ns/example/dhcp" \ xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> <net>10.254.244.0/27</net> ...content removed here for brevity... <max-lease-time>1200</max-lease-time> </subnet> </value> </edit> </yang-patch> # If the YANG Patch request was successful, # the server might respond as follows: HTTP/1.1 200 OK <yang-patch-status xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-patch"> <patch-id>add-subnets</patch-id> <ok/> </yang-patch-status>
Let us modify the 'max-lease-time' of one 'subnet' and delete the 'max-lease-time' value of the second 'subnet'. Note that the delete will cause the default value of 'max-lease-time' to take effect, which we will verify using a RESTCONF GET request.
PATCH /restconf/data/dhcp:dhcp Accept: application/yang-data+xml Content-Type: application/yang-patch+xml <yang-patch xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-patch"> <patch-id>modify-and-delete</patch-id> <edit> <edit-id>modify-max-lease-time-239</edit-id> <operation>merge</operation> <target>/dhcp:subnet=10.254.239.0%2F27</target> <value> <subnet xmlns="http://yang-central.org/ns/example/dhcp" \ xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> <net>10.254.239.0/27</net> <max-lease-time>1234</max-lease-time> </subnet> </value> </edit> <edit> <edit-id>delete-max-lease-time-244</edit-id> <operation>delete</operation> <target>/dhcp:subnet=10.254.244.0%2F27/max-lease-time</target> </edit> </yang-patch> # If the YANG Patch request was successful, # the server might respond as follows: HTTP/1.1 200 OK <yang-patch-status xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-patch"> <patch-id>modify-and-delete</patch-id> <ok/> </yang-patch-status>
To verify that our modify and delete operations took place we make use of two RESTCONF GET request as shown below.
GET /restconf/data/dhcp:dhcp/subnet=10.254.239.0%2F27/max-lease-time Accept: application/yang-data+xml HTTP/1.1 200 OK <max-lease-time xmlns="http://yang-central.org/ns/example/dhcp" xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> 1234 </max-lease-time>
GET /restconf/data/dhcp:dhcp/subnet=10.254.244.0%2F27/max-lease-time?\ with-defaults=report-all-tagged Accept: application/yang-data+xml HTTP/1.1 200 OK <max-lease-time wd:default="true" xmlns:wd="urn:ietf:params:restconf:capability:defaults:1.0" xmlns="http://yang-central.org/ns/example/dhcp" xmlns:dhcp="http://yang-central.org/ns/example/dhcp"> 7200 </max-lease-time>
Note how we in the last GET request make use of the with-defaults query parameter to request that a default value should be returned and also be tagged as such.
Network Management Datastore Architecture (NMDA), as defined in RFC 8527, extends the RESTCONF protocol. This enable RESTCONF clients to discover which datastores are supported by the RESTCONF server, determine which modules are supported in each datastore, and interact with all the datastores supported by the NMDA.
A RESTCONF client can test if a server supports the NMDA by using either the HEAD or GET methods on /restconf/ds/ietf- datastores:operational, as shown below:
HEAD /restconf/ds/ietf-datastores:operational HTTP/1.1 200 OK
A RESTCONF client can discover which datastores and YANG modules the server supports by reading the YANG library information from the operational state datastore. Note in the example below that, since the result consists of three top-nodes, it can't be represented in XML; hence we request the returned content to be in JSON format. See also: the section called “Collections”.
GET /restconf/ds/ietf-datastores:operational/datastore Accept: application/yang-data+json HTTP/1.1 200 OK { "ietf-yang-library:datastore": [ { "name": "ietf-datastores:running", "schema": "common" }, { "name": "ietf-datastores:intended", "schema": "common" }, { "name": "ietf-datastores:operational", "schema": "common" } ] }
To avoid any potential future conflict with the RESTCONF standard, any extensions made to the NSO implementation of RESTCONF is located under the URL path: /restconf/tailf, or is controlled by means of a vendor specific media type.
Note
There is no index of extensions under /restconf/tailf. To list extensions, access /restconf/data/ietf-yang-library:modules-state and follow published links for schemas.
The RESTCONF specification states that a result containing multiple instances (e.g a number of list entries) is not allowed if XML encoding is used. The reason for this is that an XML document can only have one root node.
This functionality is supported if the http://tail-f.com/ns/restconf/collection/1.0 capability is presented. See also: the section called “How to view the capabilities of the RESTCONF server”.
To remedy this, a HTTP GET request can make use of the Accept: media type: application/vnd.yang.collection+xml as shown in the following example. The result will then be wrapped within a collection element.
GET /restconf/ds/ietf-datastores:operational/\ ietf-yang-library:yang-library/datastore Accept: application/vnd.yang.collection+xml <collection xmlns="http://tail-f.com/ns/restconf/collection/1.0"> <datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library" xmlns:yanglib="urn:ietf:params:xml:ns:yang:ietf-yang-library"> <name xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"> ds:running </name> <schema>common</schema> </datastore> <datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library" xmlns:yanglib="urn:ietf:params:xml:ns:yang:ietf-yang-library"> <name xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"> ds:intended </name> <schema>common</schema> </datastore> <datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library xmlns:yanglib="urn:ietf:params:xml:ns:yang:ietf-yang-library"> <name xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"> ds:operational </name> <schema>common</schema> </datastore> </collection>
The NSO RESTCONF Query API consists of a number of operation to start a query which may live over several RESTCONF request, where data can be fetch in suitable chunks. The data to be returned is produced by applying an XPath expression where the data also may be sorted.
The RESTCONF client can check if the NSO RESTCONF server support this functionality by looking for the http://tail-f.com/ns/restconf/query-api/1.0 capability. See also: the section called “How to view the capabilities of the RESTCONF server”.
The tailf-rest-query.yang
and the
tailf-common-query.yang
YANG models
describe the structure of the RESTCONF Query API messages.
By using the Schema Resource functionality, as described in
the section called “Schema resource” , you can
get hold of them.
The API consists of the following Requests:
-
start-query : Start a query and return a query handle.
-
fetch-query-result : Use a query handle to repeatedly fetch chunks of the result.
-
immediate-query : Start a query and return the entire result immediately.
-
reset-query : (Re)set where the next fetched result will begin from.
-
stop-query : Stop (and close) the query.
The API consists of the following Replies:
-
start-query-result : Reply to the start-query request.
-
query-result : Reply to the fetch-query-result and immediate-query requests.
In the following examples, we'll use this data model:
container x { list host { key number; leaf number { type int32; } leaf enabled { type boolean; } leaf name { type string; } leaf address { type inet:ip-address; } } }]
The actual format of the payload should be represented either in XML or JSON. Note how we indicate the type of content using the Content-Type HTTP header. For XML it could look like this:
POST /restconf/tailf/query Content-Type: application/yang-data+xml <start-query xmlns="http://tail-f.com/ns/tailf-rest-query"> <foreach> /x/host[enabled = 'true'] </foreach> <select> <label>Host name</label> <expression>name</expression> <result-type>string</result-type> </select> <select> <expression>address</expression> <result-type>string</result-type> </select> <sort-by>name</sort-by> <limit>100</limit> <offset>1</offset> <timeout>600</timeout> </start-query>]
The same request in JSON format would look like:
POST /restconf/tailf/query Content-Type: application/yang-data+json { "start-query": { "foreach": "/x/host[enabled = 'true']", "select": [ { "label": "Host name", "expression": "name", "result-type": ["string"] }, { "expression": "address", "result-type": ["string"] } ], "sort-by": ["name"], "limit": 100, "offset": 1, "timeout": 600 } }]
An informal interpretation of this query is:
For each /x/host where enabled is true, select its name, and address, and return the result sorted by name, in chunks of 100 result items at a time.
Let us discuss the various pieces of this request. To start with, when using XML, we need to specify the name space as shown:
<start-query xmlns="http://tail-f.com/ns/tailf-rest-query">
The actual XPath query to run is specified by the foreach element. In the example below will search for all /x/host nodes that has the enabled node set to true:
<foreach> /x/host[enabled = 'true'] </foreach>
Now we need to define what we want to have returned from the node set by using one or more select sections. What to actually return is defined by the XPath expression.
Choose how the result should be represented. Basically, it can be the actual value or the path leading to the value. This is specified per select chunk. The possible result-types are: string , path , leaf-value and inline.
The difference between string and leaf-value is somewhat subtle. In the case of string the result will be processed by the XPath function: string() (which if the result is a node-set will concatenate all the values). The leaf-value will return the value of the first node in the result. As long as the result is a leaf node, string and leaf-value will return the same result. In the example above, the string is used as shown below. Note that at least one result-type must be specified.
The result-type inline makes it possible to return the full sub-tree of data, either in XML or in JSON format. The data will be enclosed with a tag: data.
It is possible to specify an optional label for a convenient way of labeling the returned data:
<select> <label>Host name</label> <expression>name</expression> <result-type>string</result-type> </select> <select> <expression>address</expression> <result-type>string</result-type> </select>
The returned result can be sorted. This is expressed as an XPath expression, which in most cases is very simple and refers to the found node set. In this example we sort the result by the content of the name node:
<sort-by>name</sort-by>
With the offset element we can specify at which node we should start to receive the result. The default is 1, i.e., the first node in the resulting node-set.
<offset>1</offset>
It is possible to set a custom timeout when starting or resetting a query. Each time a function is called, the timeout timer resets. The default is 600 seconds, i.e. 10 minutes.
<timeout>600</timeout>
The reply to this request would look something like this:
<start-query-result> <query-handle>12345</query-handle> </start-query-result>
The query handle (in this example '12345') must be used in all subsequent calls. To retrieve the result, we can now send:
<fetch-query-result xmlns="http://tail-f.com/ns/tailf-rest-query"> <query-handle>12345</query-handle> </fetch-query-result>
Which will result in something like the following:
<query-result xmlns="http://tail-f.com/ns/tailf-rest-query"> <result> <select> <label>Host name</label> <value>One</value> </select> <select> <value>10.0.0.1</value> </select> </result> <result> <select> <label>Host name</label> <value>Three</value> </select> <select> <value>10.0.0.3</value> </select> </result> </query-result>
If we try to get more data with the fetch-query-result we might get more result entries in return until no more data exists and we get an empty query result back:
<query-result xmlns="http://tail-f.com/ns/tailf-rest-query"> </query-result>
Finally, when we are done we stop the query:
<stop-query xmlns="http://tail-f.com/ns/tailf-rest-query"> <query-handle>12345</query-handle> </stop-query>
If we want to go back in the "stream" of received data chunks and have them repeated, we can do that with the 'reset-query' request. In the example below we ask to get results from the 42:nd result entry:
<reset-query xmlns="http://tail-f.com/ns/tailf-rest-query"> <query-handle>12345</query-handle> <offset>42</offset> </reset-query>
If we want to get the entire result sent back to us, using only one request, we can do this by using the immediate-query. This function takes similar arguments as start-query and returns the entire result analogous with the result from a fetch-query-result request. Note that it is not possible to paginate or set an offset start node for the result list; i.e. the options limit and offset are ignored.
This functionality is supported if the http://tail-f.com/ns/restconf/partial-response/1.0 capability is presented. See also: the section called “How to view the capabilities of the RESTCONF server”.
By default, the server sends back the full representation of a resource after processing a request. For better performance, the server can be instructed to send only the nodes the client really needs in a partial response.
To request a partial response for a set of list entries, use the offset and limit query parameters to specify a limited set of entries to be returned.
In the following example we retrieve only 2 entries, skipping the first entry and then returning the next two entries:
GET /restconf/data/example-jukebox:jukebox/library/artist?offset=1&limit=2 Accept: application/yang-data+json ...in return we will get the second and third elements of the list...
This functionality is supported if the http://tail-f.com/ns/restconf/unhide/1.0 capability is presented. See also: the section called “How to view the capabilities of the RESTCONF server”.
By default, hidden
nodes are not visible in the RESTCONF interface. In order to
unhide hidden nodes for retrieval or editing, clients can use
the query parameter unhide or set parameter
showHidden to true
under /confdConfig/restconf
in confd.conf file. The
query parameter unhide is supported for RPC
and action invocation.
The format of the unhide parameter is a comma separated list of
<groupname>[;<password>]
As an example:
unhide=extra,debug;secret
This example unhides the unprotected group extra and the password protected group debug with the password secret;.
This functionality is supported if the urn:ietf:params:xml:ns:yang:traceparent:1.0 and urn:ietf:params:xml:ns:yang:tracestate:1.0 capability is presented. See also: the section called “How to view the capabilities of the RESTCONF server”.
RESTCONF supports the IETF standard draft I-D.draft-ietf-netconf-restconf-trace-ctx-headers-00, that is an adaption of the W3C Trace Context standard. Trace Context standardizes the format of trace-id, parent-id and key-value pairs to be sent between distributed entities. The parent-id will become the parent-span-id for the next generated span-id in NSO.
Trace Context consists of two HTTP headers traceparent and tracestate. Header traceparent must be of the format
traceparent = <version>-<trace-id>-<parent-id>-<flags>
where version = "00" and flags = "01". The support for the values of version and flags may change in the future depending on the extension of standard or functionality.
An example of header traceparent in use is:
traceparent: 00-100456789abcde10123456789abcde10-001006789abcdef0-01
Header tracestate is a vendor-specific list of key-value pairs. An example of header tracestate in use is:
tracestate: key1=value1,key2=value2
where a value may contain space characters but not end with a space.
NSO implements Trace Context alongside the legacy way of handling trace-id, where the trace-id comes as a query parameter. These two different ways of handling trace-id cannot be used at the same time. If both are used, the request generates an error response. If a request does not include trace-id or header traceparent, a traceparent will be generated internally in NSO. NSO will consider the headers of Trace Context in RESTCONF requests if the trace-id element is enabled in the configuration file. Trace Context is handled by the progress trace functionality, see also Progress Trace in Development Guide.
It is possible to associate meta-data with the configuration data. For RESTCONF, resources such as containers, lists as well as leafs and leaf-lists can have such meta-data. For XML, this meta-data is represented as attributes attached to the XML element in question. For JSON, there does not exist a natural way to represent this info. Hence, a special notation has been introduced based on RFC 7952, see the example below.
<x xmlns="urn:x" xmlns:x="urn:x"> <id tags=" important ethernet " annotation="hello world">42</id> <person annotation="This is a person"> <name>Bill</name> <person annotation="This is another person">grandma</person> </person> </x>
{ "x": { "foo": 42, "@foo": {"tailf_netconf:tags": ["tags","for","foo"], "tailf_netconf:annotation": "annotation for foo"}, "y": { "@": {"tailf_netconf:annotation": "Annotation for parent y"}, "y": 1, "@y": {"tailf_netconf:annotation": "Annotation for sibling y"} } } }
The meta-data for an object is represented by another object constructed either of an "@" sign if the meta-data object refers to the parent object, or by the object name prefixed with an "@" sign if the meta-data object refers to a sibling object.
Note that the meta-data node types, e.g., tags and annotations, are prefixed by the module name of the YANG module where the meta-data object is defined. This representation conforms to RFC 7952 Section 5.2. The YANG module name prefixes for meta-data node types are listed below:
Meta-data type
|
Prefix
|
origin
|
ietf-origin
|
inactive/active
|
tailf-netconf-inactive
|
default
|
tailf-netconf-defaults
|
All other
|
tailf_netconf
|
Compare this to the encoding in NSO versions prior to 6.3 , where we represented meta-data for an object by another object constructed of the object name prefixed with either one or two "@" signs. The meta-data object "@x" referred to the sibling object "x" and the "@@x" object referred to the parent object. No module name prefixes were included for the meta-data data object types. This did not conform to RFC 7952 for legacy reasons. See the example below.
{ "x": { "foo": 42, "@foo": {"tags": ["tags","for","foo"], "annotation": "annotation for foo"}, "y": { "@@y": {"annotation": "Annotation for parent y"}, "y": 1, "@y": {"annotation": "Annotation for sibling y"} } } }
To continue using the old meta-data format, set
legacy-attribute-format to true in
ncs.conf
. The default is false, which
uses the
RFC 7952
format. The
legacy-attribute-format setting is
deprecated and will be removed in a future release.
It is also possible to set meta-data objects in JSON format, which was previously only possible with XML. Note that the new attribute format must be used and legacy-attribute-format set to false. Except for setting the default and insert meta-data types, which are not supported using JSON.
The RESTCONF server maintains an authentication cache. When authenticating an incoming request for a particular User:Password, it is first checked if the User exists in the cache and if so, the request is processed. This makes it possible to avoid the, potentially time consuming, login procedure that will take place in case of a cache miss.
Cache entries has a maximum Time-To-Live (TTL) and upon expiry a cache entry is removed which will cause the next request for that User to perform the normal login procedure. The TTL value is configurable via the auth-cache-ttl parameter, as shown in the example. Note that, by setting the TTL value to PT0S (zero), the cache is effectively turned off.
It is also possible to combine the Clients IP address with the User name as a key into the cache. This behaviour is disabled by default. It can be enabled by setting the enable-auth-cache-client-ip parameter to true. With this enabled, only a Client coming from the same IP address may get a hit in the authentication cache.
... <aaa> ... <restconf> <!-- Set the TTL to 10 seconds! --> <auth-cache-ttl>PT10S</auth-cache-ttl> <!-- Use both "User" and "ClientIP" as key into the AuthCache --> <enable-auth-cache-client-ip>false</enable-auth-cache-client-ip> </restconf> ... </aaa> ...
It is possible to configure the NSO RESTCONF server to pick up the client IP address via a HTTP header in the request. A list of HTTP headers to look for is configurable via the proxy-headers parameter as shown in the example.
To avoid misuse of this feature, only requests from trusted sources will be searched for such a HTTP header. The list of trusted sources is configured via the allowed-proxy-ip-prefix as shown in the example.
... <webui> ... <use-forwarded-client-ip> <proxy-headers>X-Forwarded-For</proxy-headers> <proxy-headers>X-REAL-IP</proxy-headers> <allowed-proxy-ip-prefix>10.12.34.0/24</allowed-proxy-ip-prefix> <allowed-proxy-ip-prefix>2001:db8:1234::/48</allowed-proxy-ip-prefix> </use-forwarded-client-ip> ... </webui> ...
The NSO RESTCONF server can be setup to pass a long a token used for authentication and/or validation of the client. Note that this require external authentication/validation to be setup properly. See the section called “External token validation” in Administration Guide and the section called “External authentication” in Administration Guide for details.
With token authentication we mean that the client sends a User:Password to the RESTCONF server, which will invoke an external executable that perform the authentication and upon success produces a token that the RESTCONF server will return in the X-Auth-Token HTTP header of the reply.
With token validation we mean that the RESTCONF server will pass along any token, provided in the X-Auth-Token HTTP header, to an external executable that performs the validation. This external program may produce a new token that the RESTCONF server will return in the X-Auth-Token HTTP header of the reply.
To make this work, the following need to be configured in the
ncs.conf
file:
... <restconf> ... <token-response> <x-auth-token>true</x-auth-token> </token-response> ... </restconf> ...
It is also possible to have the RESTCONF server to return a HTTP cookie containing the token.
An HTTP cookie (web cookie, browser cookie) is a small piece of data that a server sends to the user's web browser. The browser may store it and send it back with the next request to the same server. This can be convenient in certain solutions, where typically, it is used to tell if two requests came from the same browser, keeping a user logged-in, for example.
To make this happen, the name of the cookie need to be configured as well as a directives string which will be sent as part of the cookie.
... <restconf> ... <token-cookie> <name>X-JWT-ACCESS-TOKEN</name> <directives>path=/; Expires=Tue, 19 Jan 2038 03:14:07 GMT;</directives> </token-cookie> ... </restconf> ...
The RESTCONF server can be configured to reply with particular HTTP headers in the HTTP response. For example, to support Cross-Origin Resource Sharing (CORS, https://www.w3.org/TR/cors/) there is a need to add a couple of headers to the HTTP Response.
We add the extra configuration parameter in
ncs.conf
.
<restconf> <enabled>true</enabled> <custom-headers> <header> <name>Access-Control-Allow-Origin</name> <value>*</value> </header> </custom-headers> </restconf>
A number of HTTP header has been deemed so important by
security reasons that they, with sensible default values,
per default will be included in the RESTCONF reply. The values
can be changed by configuration in the
ncs.conf
file. Note that a configured empty value will effectively turn
off that particular header from being included in the
RESTCONF reply. The headers and their default values are:
-
xFrameOptions : DENY
The default value indicate that the page cannot be displayed in a frame/iframe/embed/object regardless of the site attempting to do so.
-
xContentTypeOptions : nosniff
The default value indicate that the MIME types advertised in the Content-Type headers should not be changed and be followed. In particular should requests for CSS or Javascript be blocked in case a proper MIME type is not used.
-
xXssProtection : 1; mode=block
This header is a feature of Internet Explorer, Chrome and Safari that stops pages from loading when they detect reflected cross-site scripting (XSS) attacks. It enables XSS filtering and tell the browser to prevent rendering of the page if an attack is detected.
-
strictTransportSecurity : max-age=15552000; includeSubDomains
The default value tell browsers that the RESTCONF server should only be accessed using HTTPS, instead of using HTTP. It set the time that the browser should remember this and state that this rule applies to all of the servers subdomains as well.
-
contentSecurityPolicy : default-src 'self'; block-all-mixed-content; base-uri 'self'; frame-ancestors 'none';
The default value means that: Resources like fonts, scripts, connections, images, and styles will all only load from the same origin as the protected resource. All mixed contents will be blocked and frame-ancestors like iframes and applets is prohibited.
Swagger is a documentation language used to describe RESTful APIs. The resulting specifications are used to both document APIs as well as generating clients in a variety of languages. For more information about the Swagger specification itself and the ecosystem of tools available for it, see swagger.io.
The RESTCONF API in NSO provides an HTTP-based interface for accessing data. The YANG modules loaded into the system define the schema for the data structures that can be manipulated using the RESTCONF protocol. The yanger tool provides options to generate Swagger specifications from YANG files. The tool currently supports generating specifications according to OpenAPI/Swagger 2.0 using JSON encoding. The tool supports validation of JSON bodies in body parameters and response bodies, and XML content validation is not supported.
YANG and Swagger are two different languages serving slightly different purposes. YANG is a data modeling language used to model configuration data, state data, Remote Procedure Calls, and notifications for network management protocols such as NETCONF and RESTCONF. Swagger is an API definition language that documents API resource structure as well as HTTP body content validation for applicable HTTP request methods. Translation from YANG to Swagger is not perfect in the sense that there are certain constructs and features in YANG that is not possible to capture completely in Swagger. The design of the translation is designed such that the resulting Swagger definitions are more restrictive than what is expressed in the YANG definitions. This means that there are certain cases where a client can do more in the RESTCONF API than what the Swagger definition expresses. There is also a set of well-known resources defined in the RESTCONF RFC 8040 that are not part of the generated Swagger specification, notably resources related to event streams.
The yanger tool is a YANG parser and validator that
provides options to convert YANG modules to a multitude of formats
including Swagger. You use the -f swagger option to
generate a Swagger definition from one or more YANG files. The following
command generates a Swagger file named example.json
from the example.yang
YANG file:
yanger -t expand -f swagger example.yang -o example.json
It is only supported to generate Swagger from one YANG module at a
time. It is possible however to augment this module by supplying
additional modules. The following command generates a Swagger document
from base.yang
which is augmented by
base-ext-1.yang
and
base-ext-2.yang
:
yanger -t expand -f swagger base.yang base-ext-1.yang base-ext-2.yang -o base.json
Only supplying augmenting modules is not supported.
Use the --help option to the yanger command to see all available options:
yanger --help
The complete list of options related to Swagger generation is:
Swagger output specific options: --swagger-host Add host to the Swagger output --swagger-basepath Add basePath to the Swagger output --swagger-version Add version url to the Swagger output. NOTE: this will override any revision in the yang file --swagger-tag-mode Set tag mode to group resources. Valid values are: methods, resources, all [default: all] --swagger-terms Add termsOfService to the Swagger output --swagger-contact-name Add contact name to the Swagger output --swagger-contact-url Add contact url to the Swagger output --swagger-contact-email Add contact email to the Swagger output --swagger-license-name Add license name to the Swagger output --swagger-license-url Add license url to the Swagger output --swagger-top-resource Generate only swagger resources from this top resource. Valid values are: root, data, operations, all [default: all] --swagger-omit-query-params Omit RESTCONF query parameters [default: false] --swagger-omit-body-params Omit RESTCONF body parameters [default: false] --swagger-omit-form-params Omit RESTCONF form parameters [default: false] --swagger-omit-header-params Omit RESTCONF header parameters [default: false] --swagger-omit-path-params Omit RESTCONF path parameters [default: false] --swagger-omit-standard-statuses Omit standard HTTP response statuses. NOTE: at least one successful HTTP status will still be included [default: false] --swagger-methods HTTP methods to include. Example: --swagger-methods "get, post" [default: "get, post, put, patch, delete"] --swagger-path-filter Filter out paths matching a path filter. Example: --swagger-path-filter "/data/example-jukebox/jukebox"
Using the example-jukebox.yang
from the
RESTCONF RFC 8040,
the following example generates a comprehensive Swagger
definition using a variety of the Swagger-related options:
yanger -p . -t expand -f swagger example-jukebox.yang \
--swagger-host 127.0.0.1:8080 \
--swagger-basepath /restconf \
--swagger-version "My swagger version 1.0.0.1" \
--swagger-tag-mode all \
--swagger-terms "http://my-terms.example.com" \
--swagger-contact-name "my contact name" \
--swagger-contact-url "http://my-contact-url.example.com" \
--swagger-contact-email "my-contact-email@example.com" \
--swagger-license-name "my license name" \
--swagger-license-url "http://my-license-url.example.com" \
--swagger-top-resource all \
--swagger-omit-query-params false \
--swagger-omit-body-params false \
--swagger-omit-form-params false \
--swagger-omit-header-params false \
--swagger-omit-path-params false \
--swagger-omit-standard-statuses false \
--swagger-methods "post, get, patch, put, delete, head, options"