which is used by the administrators to manage Kea servers' instances.
In the most typical case, the CA forwards commands received over the
-RESTful API to the respetive Kea servers, e.g. DHCPv4 server, DHCPv6
+RESTful API to the respective Kea servers, e.g. DHCPv4 server, DHCPv6
server etc. The communication between the CA and other servers is
established with the use of unix domain sockets. This is possible because
the CA is running on the same system as other Kea services to which
The CA can forward the same command to multiple Kea services and return
an aggregated response (from all services) over the RESTful API. The
"service" parameter included in the client's command can contain one
-or multiple services at which the command is targetted. The CA will
+or more services at which the command is targeted. The CA will
iterate over this list and forward the command to each of them
individually.
In some cases, the commands containing the "service" value can be handled
directly by the CA. This is usually the case when the CA is running
with hooks libraries attached. The hooks libraries must implement
-callouts for the "control_command_receive" hook point, which are
+callouts for the "control_command_receive" hook point, which will be
invoked by the CA when the command is received. If the hooks libraries
set the 'skip' status, it is an indication to the CA that the command
-has been processed by the CA and simply return a response created by the
-hooks libraries to the client. An example of the hooks library attached to
-the CA and handling the commands for other services is the library which
+has been processed by the CA and that it should return the response created
+by the hooks libraries to the client. An example of the hooks library attached
+to the CA and handling the commands for other services is a library which
stores or retrieves some data from the SQL database.
The "service" parameter is optional. If it is not included in the command
-(or it is blank list), it is an indication that the command relates to
+(or it is an empty list), this indicates that the command relates to the
CA and that the CA should handle it, e.g. return its own configuration in
response to a "config-get" command.
The @ref isc::http::HttpListener provides an entry point to this library.
It is used by the CA to bind the acceptor to the specific address and
port. When the client connects to this address and port, the acceptor's
-callback function is invoked which opens new connection and starts
-receiving the data over the socket. The @ref isc::http::HttpConnection
-implements a logic to read and parse the received data. Each new TCP
-connection has a unique instance of the @ref isc::http::HttpConnection
-associated. When the portion of data is received (asynchronously) over
-the socket the data is provided to the instance of the
+callback function is invoked which opens a new connection and starts
+receiving data over that socket. The @ref isc::http::HttpConnection
+implements the logic to read and parse received data. Each new TCP
+connection is associated with unique instance of the @ref isc::http::HttpConnection
+When a portion of data is received (asynchronously) over
+the socket it is provided to the instance of the
@ref isc::http::HttpRequestParser object (unique per connection) and
data parsing is continued until the parser runs out of data or until
the entire HTTP request has been received. The
content types. The Control Agent uses "application/json" content
type which describes messages with JSON structures carried within the
message body. The JSON structures represent commands sent to the Kea
-server(s) by the controlling clients. libkea-http provides generic classes
-(derived from @ref isc::http::HttpRequest) which faciliate validation of
-messsages holding various content types.
+server(s) by controlling clients. libkea-http provides generic classes
+(derived from @ref isc::http::HttpRequest) which facilitate validation of
+messages holding various content types.
CA uses @ref isc::http::PostHttpRequestJson, which encapsulate messages
sent using HTTP POST and including JSON content, to represent received messages.
the HTTP responses of a desired type. The instance of the factory class is
provided to the @ref isc::http::HttpListener via its constructor. The listener
calls an implementation of the
-@ref isc::http::HttpResponseCreatorFactory::create when the new HTTP
+@ref isc::http::HttpResponseCreatorFactory::create when a new HTTP
message has been received and parsed.
The CA component includes the @ref isc::agent::CtrlAgentResponseCreatorFactory
@section ctrlAgentCommandMgr Handling commands with Command Manager
The @ref isc::agent::CtrlAgentCommandMgr is a derivation of the
-@ref isc::config::HookedCommandMgr and adds capability to forward received
-(over HTTP) commands to the respective Kea servers. The
-@ref isc::agent::CtrlAgentCommandMgr forwards commands over the unix domain
+@ref isc::config::HookedCommandMgr which adds the capability to forward
+commands received over HTTP to specific Kea servers. The
+@ref isc::agent::CtrlAgentCommandMgr forwards commands over a Unix domain
socket, using @ref isc::asiolink::UnixDomainSocket class. All responses
to a particular command (possibly received from multiple Kea servers) are
aggregated within a JSON list and sent back to the controlling client over
In some cases the responses may be generated locally (without forwarding).
Typically, the command will be generated by the CA when the command sent
by the client lacks the "service" parameter, which indicates that the
-command is targetted at the CA itself. In some cases the commands can also
+command is targeted at the CA itself. In some cases the commands can also
be processed by the hooks libraries attached to the CA.
@section CtrlAgentSecurity Security considerations
The Control Agent doesn't provide any mechanisms to secure the communication
-over the RESTful API. In the design of the CA we have considered including builtin
+over the RESTful API. In the design of the CA we have considered including built-in
HTTPS solutions (HTTP + TLS), making use of crypto libraries supported by Kea.
-It was evetually decided to not implement the secure layer within Kea for the following resons:
+It was eventually decided to not implement the secure layer within Kea for the following reasons:
- additional code complexity which requires maintenance, bug fixing and
monitoring for security vulnerabilities in the OpenSSL/Botan code,
- OpenSSL/Botan code may be awkward to use and it is likely we wouldn't
installations?), a reverse HTTP proxy can be setup using one of the third
party HTTP server implementations, e.g. Apache, nginx etc.
-*/
\ No newline at end of file
+*/
projects / thirdparty / kea.git / commitdiff
