alt="Istio logo" title="Istio" height="100" width="100" />
</a>

---

                          type: object
                        tunnel:
                          description: Configuration of tunneling TCP over other transport
                            or application layers for the host configured in the DestinationRule.
                          properties:
                            protocol:
                              description: Specifies which protocol to use for tunneling

                          type: object
                        tunnel:
                          description: Configuration of tunneling TCP over other transport
                            or application layers for the host configured in the DestinationRule.
                          properties:
                            protocol:
                              description: Specifies which protocol to use for tunneling

### Inbound

Traffic entering a pod over HBONE will be handled by the "inbound" code path, on port 15008.

Incoming requests have multiple "layers": TLS wrapping HTTP CONNECT that is wrapping the user's connection.

To unwrap the first layer, we terminate TLS.
As part of this, we need to pick the correct certificate to serve on behalf of the destination workload.

string subjectAltNames: description: A list of alternate names to verify the subject identity in the certificate. items: type: string type: array type: object tunnel: description: Configuration of tunneling TCP over other transport or application layers for the host configured in the DestinationRule. properties: protocol: description: Specifies which protocol to use for tunneling the downstream connection. type: string targetHost: description: Specifies a host to which the downstream connection is...

![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.

1. First, the request is handled by the SDS server. This is mostly just an intermediate translation layer exposing

immutable snapshot of the current state of the world. It is regenerated (usually partially) on each configuration push (more on this below). Due to being a snapshot, most lookups are lock-free.

`PushContext` is built up by querying the above layers. For some simple use cases, this is as simple as storing something like `configstore.List(SomeType)`; in this case, the only difference from directly exposing the configstore is to snapshot the current state. In other cases, some pre-computations...