![SDS decision flow](docs/sds-flow.svg)

### Default CA Flow through istio-agent

![CA Flow](docs/ca.svg)

A single SDS request from Envoy goes through a few different layers in istio-agent.

interface FlowControlListener {
  /**
   * Notification that the receiving stream flow control window has changed.
   * [WindowCounter] generally carries the client view of total and acked bytes.
   */
  fun receivingStreamWindowChanged(
    streamId: Int,
    windowCounter: WindowCounter,
    bufferSize: Long,
  )

  /**
   * Notification that the receiving connection flow control window has changed.

It can be used by third party applications and systems.

And it can also be used by yourself, to debug, check and test the same application.

## The `password` flow

Now let's go back a bit and understand what is all that.

The `password` "flow" is one of the ways ("flows") defined in OAuth2, to handle security and authentication.

OAuth2 was designed so that the backend or API could be independent of the server that authenticates the user.

a timeout elapses. If we get bytes but there's nobody asking for them, we buffer them. We don't consider bytes as delivered for flow control until they're consumed by the application.

Consider an application streaming a video over http/2. Perhaps the user pauses the video and the application stops reading bytes from this stream. The buffer will fill up, and flow control prevents the server from sending more data on this stream. When the user unpauses her video the buffer drains, the read...

 * limitations under the License.
 */
package okhttp3.internal.http2

import okhttp3.ConnectionListener
import okhttp3.internal.http2.flowcontrol.WindowCounter

/**
 * ConnectionListener that outputs CSV for flow control of client receiving streams.
 */
class Http2FlowControlConnectionListener : ConnectionListener(), FlowControlListener {
  val start = System.currentTimeMillis()

  override fun receivingStreamWindowChanged(

	OpMuxServerMsg

	// OpUnblockSrvMux contains a message that a server mux is unblocked with one.
	// Only Stateful streams has flow control.
	OpUnblockSrvMux

	// OpUnblockClMux contains a message that a client mux is unblocked with one.
	// Only Stateful streams has flow control.
	OpUnblockClMux

	// OpAckMux acknowledges a mux was created.
	OpAckMux

	// OpRequest is a single request + response.

# by whitespace. The flag "-F<x>" changes the behavior such that fields are now strings
# separated by the character <x>. Therefore, -F\' (escaped single quote) means that field
# $2 in <Tensor'flow'> is <flow>. This is useful for reading string literals like below.
export TF_VER_SUFFIX=$(awk -F\" '/#define TF_VERSION_SUFFIX/ {print $2}' tensorflow/core/public/version.h)

org.checkerframework.dataflow.cfg.node
org.checkerframework.dataflow.cfg.playground
org.checkerframework.dataflow.constantpropagation
org.checkerframework.dataflow.qual
org.checkerframework.dataflow.util
org.checkerframework.framework.flow
org.checkerframework.framework.qual
org.checkerframework.framework.source
org.checkerframework.framework.test
org.checkerframework.framework.test.diagnostics
org.checkerframework.framework.type

The following diagram illustrates the flow of unauthenticated traffic with a `PERMISSIVE` policy:

```mermaid
graph TD;
src[src pod]-->|plaintext port|ztunnel{"ztunnel (L4 policy applied here)"}
ztunnel{ztunnel}-->|TLS|wp{waypoint}
wp-->|mTLS|ztunnel

  # Options for controlling the logger.
  logger:
    level: "debug"
    format: "text" # can also be "json"

# Default values shown below
oauth2:
  # use ["code", "token", "id_token"] to enable implicit flow for web-only clients
  responseTypes: [ "code", "token", "id_token" ] # also allowed are "token" and "id_token"
  # By default, Dex will ask for approval to share data with application