11 RESTCONF¶

Clixon supports two RESTCONF compile-time variants: FCGI and Native.

11.1 Architecture¶

The restconf deamon provides a http/https RESTCONF interface to the Clixon backend. It comes in two variants, as shown in the figure above:

Native http, which combines a HTTP and Restconf server. Further, HTTP configuration is made using Clixon.

A reverse proxy (such as NGINX) and FastCGI where web and restconf function is separated. NGINX is used to make all HTTP configuration.

The restconf daemon communicates with the backend using internal netconf over the CLIXON_SOCK. If FCGI is used, there is also a FCGI socket specified by fcgi-socket in clixon-config/restconf.

The restconf daemon reads its initial config options from the configuration file on startup. The native http variant can read config options from the backend as an alternative to reading everything from clixon options.

You can add plugins to the restconf daemon, where the primary usecase is authentication, using the ca_auth callback.

Note that there is some complexity in the configuration of the different variants of native Clixon restconf involving HTTP/1 vs HTTP/2, TLS vs plain HTTP, client cert vs basic authentication and external vs internal daemon start.

11.2 Installation¶

The RESTCONF daemon can be configured for compile-time (by autotools) as follows:

--disable-http1

Disable native http/1.1 (ie http/2 only)

--disable-nghttp2

Disable native http/2 using libnghttp2 (ie http/1 only)

--with-restconf=native

RESTCONF using native http. (DEFAULT)

--with-restconf=fcgi

RESTCONF using fcgi/ reverse proxy.

--without-restconf

No RESTCONF

After that perform system-wide compilation:

make && sudo make install

11.3 Command-line options¶

The restconf daemon have the following command-line options:

`-h`	Help
`-D <level>`	Debug level
`-f <file>`	Clixon config file
`-E <dir>`	Extra configuration directory
`-l <option>`	Log on (s)yslog, std(e)rr, std(o)ut, (n)one or (f)ile. Syslog is default. If foreground, then syslog and stderr is default.
`-p <dir>`	Add Yang directory path (see CLICON_YANG_DIR)
`-y <file>`	Load yang spec file (override yang main module)
`-a <family>`	Internal backend socket family: UNIX\|IPv4\|IPv6
`-u <path\|addr>`	Internal socket domain path or IP addr (see -a)
`-r`	Do not drop privileges if run as root
`-W <user>`	Run restconf daemon as this user, drop according to `CLICON_RESTCONF_PRIVILEGES`
`-R <xml>`	Restconf configuration in-line overriding config file
`-o <option=value>`
	Give configuration option overriding config file (see clixon-config.yang)

Note that the restconf daemon started as root, drops privileges to wwwuser, unless the -r command-line option is used, or CLICON_RESTCONF_PRIVILEGES is defined.

11.4 Configuration options¶

The following RESTCONF configuration options can be defined in the clixon configuration file:

CLICON_RESTCONF_DIR: Location of restconf .so plugins. Load all .so plugins in this dir as restconf code plugins.
CLICON_RESTCONF_INSTALLDIR: Path to dir of clixon-restconf daemon binary as used by backend if started internally
CLICON_RESTCONF_STARTUP_DONTUPDATE: Disable automatic update of startup on restconf edit operations This is not according to standard RFC 8040 Sec 1.4.
CLICON_RESTCONF_USER: Run clixon_restconf daemon as this user, default is www-data.
CLICON_RESTCONF_PRIVILEGES: Restconf daemon drop privileges mode, one of: none, drop_perm, drop_temp
CLICON_RESTCONF_HTTP2_PLAIN: Enable plain (non-tls) HTTP/2.
CLICON_BACKEND_RESTCONF_PROCESS: Start restconf daemon internally from backend daemon. The restconf daemon reads its config from the backend running datastore.
CLICON_ANONYMOUS_USER: If RESTCONF authentication auth-type=none then use this user
CLICON_RESTCONF_API_ROOT: RESTCONF API root path as defined in RFC 8040, default is /restconf

More more documentation of the options, see the source YANG file.

11.5 Advanced config¶

Apart from options, there is also structured restconf data primarily for native mode encapsulated with <restconf>...</restconf> as defined in clixon-restconf.yang.

The first-level fields of the advanced restconf structure are the following:

enable: Enable the RESTCONF daemon. If disabled, the restconf daemon will not start
auth-type: Authentication method (see auth types)
debug: Enable debug
log-destination: Either syslog or file (/var/log/clixon_restconf.log)
pretty: Restconf vallues are pretty printed by default. Disable to turn this off

The advanced config can be given using three different methods

inline - as command-line option using -R

config-file - as part of the regular config file

datastore - committed in the regular running datastore

11.5.1 Inline¶

When starting the restconf daemon, structured data can be directly given as a command-line option:

-R <restconf xmlns="http://clicon.org/restconf"><enable>true</enable></restconf>

11.5.2 Config file¶

The restconf config can also be defined locally within the clixon config file, such as:

<CLICON_FEATURE>clixon-restconf:fcgi</CLICON_FEATURE>
<CLICON_BACKEND_RESTCONF_PROCESS>false/CLICON_BACKEND_RESTCONF_PROCESS>
<restconf>
    <enable>true</enable>
    <fcgi-socket>/wwwdata/restconf.sock</fcgi-socket>
 </restconf>

11.5.3 Datastore¶

Alternatively if CLICON_BACKEND_RESTCONF_PROCESS is set, the restconf configuration is:

<CLICON_FEATURE>clixon-restconf:fcgi</CLICON_FEATURE>
<CLICON_BACKEND_RESTCONF_PROCESS>false/CLICON_BACKEND_RESTCONF_PROCESS>

And the detailed restconf is defined in the regular running datastore by adding something like:

<restconf xmlns="http://clicon.org/restconf">
   <enable>true</enable>
   <fcgi-socket>/wwwdata/restconf.sock</fcgi-socket>
</restconf>

In the latter case, the restconf daemon reads its config from the running datastore on startup.

Note

If CLICON_BACKEND_RESTCONF_PROCESS is enabled, the restconf config must be in the regular datastore.

11.5.4 Features¶

The Restconf config has two features:

fcgi: The restconf server supports the fast-cgi reverse proxy mode. Set this if fcgi/nginx is used.
allow-auth-none: Authentication supports a none mode.

Example, add this in the config file to enable fcgi:

<clixon-config xmlns="http://clicon.org/config">
   ...
   <CLICON_FEATURE>clixon-restconf:fcgi</CLICON_FEATURE>

11.5.5 Auth types¶

The RESTCONF daemon uses the following authentication types:

none: Messages are not authenticated and set to the value of CLICON_ANONYMOUS_USER. A callback can revise this behavior. Note, must set allow-auth-none feature.
client-cert: Set to authenticated and extract the username from the SSL_CN parameter. A callback can revise this behavior.
user: User-defined behaviour as implemented by the auth callback. Typically done by basic auth, eg HTTP_AUTHORIZATION header, and verify password

11.5.6 FCGI mode¶

Applies if clixon is configured with --with-restconf=fcgi. Fcgi-specific config options are:

fcgi-socket: Path to FCGI unix socket. This path should be the same as specific in fcgi reverse proxy

Need also fcgi feature enabled: features

11.5.7 Native mode¶

Applies if clixon is configured with --with-restconf=native. Native specific config options are:

server-cert-path: Path to server certificate file
server-key-path: Path to server key file
server-ca-cert-path: Path to server CA cert file
socket: List of server sockets that the restconf daemon listens to with the following fields:
socket namespace: Network namespace
socket address: IP address to bind to
socket port: TCP port to bind to
socket ssl: If true: HTTPS; if false: HTTP protocol

11.5.8 Examples¶

Configure a single HTTP on port 80 in the default config file:

<clixon-config xmlns="http://clicon.org/config">
   <CLICON_CONFIGFILE>/usr/local/etc/clixon.xml</CLICON_CONFIGFILE>
   ...
   <restconf>
      <enable>true</enable>
      <auth-type>user</auth-type>
      <socket>
         <namespace>default</namespace>
         <address>0.0.0.0</address>
         <port>80</port>
         <ssl>false</ssl>
      </socket>
   </restconf>
</clixon-config>

Configure two HTTPS listeners in two different namespaces:

<restconf xmlns="https://clicon.org/restconf">
   <enable>true</enable>
   <auth-type>client-certificate</auth-type>
   <server-cert-path>/etc/ssl/certs/clixon-server-crt.pem</server-cert-path>
   <server-key-path>/etc/ssl/private/clixon-server-key.pem</server-key-path>
   <server-ca-cert-path>/etc/ssl/certs/clixon-ca_crt.pem</server-ca-cert-path>
   <socket>
      <namespace>default</namespace>
      <address>0.0.0.0</address>
      <port>443</port>
      <ssl>true</ssl>
   </socket>
   <socket>
      <namespace>myns</namespace>
      <address>0.0.0.0</address>
      <port>443</port>
      <ssl>true</ssl>
   </socket>
</restconf>

11.5.9 SSL Certificates¶

If you use native RESTCONF you may want to have server/client certs. If you use FCGI, certs are configured according to the reverse proxy documentation, such as NGINX. The rest of this section applies to native restconf only.

If you already have certified server certs, ensure CLICON_SSL_SERVER_CERT and CLICON_SSL_SERVER_KEY points to them.

If you do not have them, you can generate self-signed certs, for example as follows:

openssl req -x509 -nodes -newkey rsa:4096 -keyout /etc/ssl/private/clixon-server-key.pem -out /etc/ssl/certs/clixon-server-crt.pem -days 365

You can also generate client certs (not shown here) using CLICON_SSL_CA_CERT. Example using client certs and curl for client andy:

curl -Ssik --key andy.key --cert andy.crt -X GET https://localhost/restconf/data/example:x

11.6 Starting¶

You can start the RESTCONF daemon in several ways:

systemd , externally started

internally using the process-control RPC (see below)

docker mechanisms, see the docker container docs

11.6.1 Start with Systemd¶

The Restconf service can be installed at, for example, /etc/systemd/system/example_restconf.service:

[Unit]
Description=Starts and stops an example clixon restconf service on this system
Wants=example.service
After=example.service
[Service]
Type=simple
User=root
Restart=on-failure
ExecStart=/usr/local/sbin/clixon_restconf -f /usr/local/etc/example.xml
[Install]
WantedBy=multi-user.target

11.6.2 Internal start¶

For starting restconf internally, you need to enable CLICON_BACKEND_RESTCONF_PROCESS option

Thereafter, you can either use the clixon-restconf.yang configuration or use the clixon-lib.yang process control RPC:s to start/stop/restart the daemon or query status.

The algorithm for starting and stopping the clixon-restconf internally is as follows:

on RPC start, if enable is true, start the service, if false, error or ignore it

on RPC stop, stop the service

on backend start make the state as configured

on enable change, make the state as configured

Example 1, using netconf edit-config to start the process:

<?xml version="1.0" encoding="UTF-8"?>
<hello xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
   <capabilities><capability>urn:ietf:params:netconf:base:1.1</capability></capabilities>
</hello>]]>]]>
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="10">
   <edit-config>
      <default-operation>merge</default-operation>
      <target><candidate/></target>
      <config>
         <restconf xmlns="http://clicon.org/restconf">
            <enable>true</enable>
         </restconf>
      </config>
   </edit-config
</rpc>
<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="10">
   <ok/>
</rpc-reply>
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="11">
   <commit/>
  </rpc>
<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="10">
   <ok/>
</rpc-reply>

Example 2, using netconf RPC to restart the process:

<?xml version="1.0" encoding="UTF-8"?>
<hello xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
   <capabilities><capability>urn:ietf:params:netconf:base:1.1</capability></capabilities>
</hello>]]>]]>
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="10">
   <process-control xmlns="http://clicon.org/lib">
      <name>restconf</name>
      <operation>restart</operation>
   </process-control>
</rpc>
<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="10">
   <pid xmlns="http://clicon.org/lib">1029</pid>
</rpc-reply>

Note that the backend daemon must run as root (no lowering of privileges) to use this feature.

11.7 Plugin callbacks¶

Restconf plugins implement callbacks, some are same as for backend plugins.

init: Clixon plugin init function, called immediately after plugin is loaded into the restconf daemon.
start: Called when application is started and initialization is complete, and after drop privileges.
exit: Called just before plugin is unloaded
extension: Called at parsing of yang modules containing an extension statement.
auth: See auth callback

11.7.1 Auth callback¶

The role of the authentication callback is, given a message (its headers) and authentication type, determine if the message passes authentication and return an associated user.

The auth callback is invoked after incoming processing, including cert validation, if any, but before relaying the message to the backend for NACM checks and datastore processing.

If the message is not authenticated, an error message is returned with tag: access denied and HTTP error code 401 Unauthorized.

There are default handlers for TLS client certs and for “none” authentication. But other variants, such as http basic authentication, oauth2 or the remapping of client certs to NACM usernames, can be implemented by this callback

If the message is authenticated, a user is associated with the message. This user can be derived from the headers or mapped in an application-dependent way. This user is used internally in Clixon and sent via the IPC protocol to the backend where it may be used for NACM authorization.

The signature of the auth callback is as follows:

int ca_auth(clicon_handle h, void *req, clixon_auth_type_t auth_type, char **authp);

where:

h: Clixon handle
req: Per-message request www handle to use with restconf_api.h
auth-type: Specifies how the authentication is made and what default value
authp: NULL if credentials failed, otherwise malloced string of authentoicated user

The return value is one of:

-1: Fatal error, close socket
0: Ignore, undecided, not handled, same as no callback. Fallback to default handler.
1: OK see authp parameter whether the result is authenticated or not, and the associated user.

If there are multiple callbacks, the first result which is not “ignore” is returned. This is to allow for different callbacks registering different classes, or grouping of authentication.

The main example contains example code.

11.8 FCGI¶

This section describes the RESTCONF FCGI mode using NGINX.

You need to configure the following:

Configure clixon with --with-restconf=fcgi

Restconf config in the Clixon config file

Reverse proxy configuration

Start the restconf daemon (see starting)

11.8.1 Restconf config¶

The restconf daemon can be started in several ways as described in Section auth types. In all cases however, the configuration is simpler than in native mode. For example:

<clixon-config xmlns="http://clicon.org/config">
   ...
   <CLICON_FEATURE>clixon-restconf:fcgi</CLICON_FEATURE>
   <restconf>
      <enable>true</enable>
      <fcgi-socket>/wwwdata/restconf.sock</fcgi-socket>
   </restconf>
</clixon-config>

11.8.2 Reverse proxy config¶

If you use FCGI, you need to configure a reverse-proxy, such as NGINX. A typical configuration is as follows:

server {
  ...
  location / {
    fastcgi_pass unix:/www-data/fastcgi_restconf.sock;
    include fastcgi_params;
  }
}

where fastcgi_pass setting should match by fcgi-socket in clixon-config/restconf.

11.9 HTTP data¶

As part of the native restconf implementation, Clixon provides a limited http-data (web) server.

11.9.1 Configuration options¶

The following configuration options can be defined in the clixon configuration file:

CLICON_HTTP_DATA_ROOT: Location in file system where http-data files are searched. Soft links, ‘..’, ‘~’ etc are not followed. Default is /var/www.
CLICON_HTTP_DATA_PATH: Prefix to match with URI to match for http-data. This path will be appended to CLICON_HTTP_DATA_ROOT to find a matching file. Default is /. Note that the restconf match prefix is /restconf.

You also need to define <CLICON_FEATURE>clixon-restconf:http-data</CLICON_FEATURE> to enable the functionality.

Example¶

The following is an example of a config file for setting up an http-data service at /var/www/data:

<clixon-config xmlns="http://clicon.org/config">
  <CLICON_FEATURE>clixon-restconf:http-data</CLICON_FEATURE>
  <CLICON_HTTP_DATA_ROOT>/var/www</CLICON_HTTP_DATA_ROOT>
  <CLICON_HTTP_DATA_PATH>/data</CLICON_HTTP_DATA_PATH>
  ...

An example curl call could be:

curl -X GET -H 'Accept: text/html' http://localhost/data/index.html

Provided there is a valid html file at /var/www/data/index.hmtl.

11.9.2 Features and limitation¶

The http server is very limited in functionality:

No dynamic (backend scripts) supported, only static pages loaded from files.

Operations limited to GET, HEAD, and OPTIONS

Query parameters are not supported

Indata is not supported

Supported media is: html, css, js, fonts, and some images. ALll other media is octet-stream

All features of the native restconf implementation are available for the http-data as well. This includes http/1 and http/2 and TLS using openssl.

There is support for URI path internal redirect to a file called index.html. This can be changed by compile-time option HTTP_DATA_INTERNAL_REDIRECT.

11.10 RESTCONF streams¶

Clixon has an experimental RESTCONF event stream implementations following RFC8040 Section 6 using Server-Sent Events (SSE). Currently this is implemented in FCGI/Nginx only (not native).

Note

RESTCONF streams are experimental and only implemented for FCGI.

Example: set the Clixon configuration options:

<CLICON_STREAM_PATH>streams</CLICON_STREAM_PATH>
<CLICON_STREAM_URL>https://example.com</CLICON_STREAM_URL>
<CLICON_STREAM_RETENTION>3600</CLICON_STREAM_RETENTION>

In this example, the stream example is accessed with https://example.com/streams/example.

Clixon defines an internal in-memory (not persistent) replay function controlled by the configure option above. In this example, the retention is configured to 1 hour, i.e., the stream replay function will only save timeseries one hour, but if the restconf daemon is restarted, the history will be lost.

In the Nginx configuration, add the following to extend the nginx configuration file with the following statements (for example):

location /streams {
    fastcgi_pass unix:/www-data/fastcgi_restconf.sock;
    include fastcgi_params;
    proxy_http_version 1.1;
    proxy_set_header Connection "";
}

An example of a stream access is as follows:

curl -H "Accept: text/event-stream" -s -X GET http://localhost/streams/EXAMPLE
data: <notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"><eventTime>2018-11-04T14:47:11.373124</eventTime><event><event-class>fault</event-class><reportingEntity><card>Ethernet0</card></reportingEntity><severity>major</severity></event></notification>
data: <notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"><eventTime>2018-11-04T14:47:16.375265</eventTime><event><event-class>fault</event-class><reportingEntity><card>Ethernet0</card></reportingEntity><severity>major</severity></event></notification>

You can also specify start and stop time. Start-time enables replay of existing samples, while stop-time is used both for replay, but also for stopping a stream at some future time:

curl -H "Accept: text/event-stream" -s -X GET http://localhost/streams/EXAMPLE?start-time=2014-10-25T10:02:00&stop-time=2014-10-25T12:31:00

11.10.1 Fcgi stream options¶

The following options apply only for fcgi mode and notification streams:

CLICON_STREAM_DISCOVERY_RFC8040: Enable monitoring information for the RESTCONF protocol from RFC 804 (only fcgi)
CLICON_STREAM_PATH: Stream path appended to CLICON_STREAM_URL to form stream subscription URL (only fcgi)