# Istio operator code overview

## Introduction

This document covers primarily the code, with some background on how the design maps to it.
See the
[design doc](https://docs.google.com/document/d/11j9ZtYWNWnxQYnZy8ayZav1FMwTH6F6z6fkDYZ7V298/edit#heading=h.qex63c29z2to)
for a more complete design description. The operator code is divided roughly into five areas:

1. [IstioOperatorSpec API](#istiooperatorspec-api) and related infrastructure, which is expressed as a

# Ztunnel

This document provides an overview of the architecture and design decisions around Ztunnel, the node-proxy component in ambient mode.

## Background and motivation

Motivations to implement ztunnel generally came from two areas.

First, and most importantly, it serves as a means to implement the real goal: waypoints.

# Updating charts and values.yaml

## Acceptable Pull Requests

Helm charts `values.yaml` represent a complex user facing API that tends to grow uncontrollably over time
due to design choices in Helm.
The underlying Kubernetes resources we configure have 1000s of fields; given enough users and bespoke use cases,
eventually someone will want to customize every one of those fields.

  // index 2 in this pod). This syntax is chosen only to have some well-defined way of
  // referencing a part of an object.
  // TODO: this design is not final and this field is subject to change in the future.
  // +optional
  optional string fieldPath = 7;
}

// PersistentVolume (PV) is a storage resource provisioned by an administrator.

//
// <digit>           ::= 0 | 1 | ... | 9
// <digits>          ::= <digit> | <digit><digits>
// <number>          ::= <digits> | <digits>.<digits> | <digits>. | .<digits>
// <sign>            ::= "+" | "-"
// <signedNumber>    ::= <number> | <sign><number>
// <suffix>          ::= <binarySI> | <decimalExponent> | <decimalSI>
// <binarySI>        ::= Ki | Mi | Gi | Ti | Pi | Ei
//

    listKind: IPAddressPoolList
    plural: ipaddresspools
    singular: ipaddresspool
  scope: Namespaced
  versions:
  - additionalPrinterColumns:
    - jsonPath: .spec.autoAssign
      name: Auto Assign
      type: boolean
    - jsonPath: .spec.avoidBuggyIPs
      name: Avoid Buggy IPs
      type: boolean
    - jsonPath: .spec.addresses
      name: Addresses
      type: string
    name: v1beta1

- [node selector](https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#nodeselector)
- [toleration](https://kubernetes.io/docs/concepts/configuration/taint-and-toleration/)
- [affinity and anti-affinity](https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#affinity-and-anti-affinity)
- [deployment strategy](https://kubernetes.io/docs/concepts/workloads/controllers/deployment/)

  // controller. If a Job is suspended after creation (i.e. the flag goes from
  // false to true), the Job controller will delete all active Pods associated
  // with this Job. Users must design their workload to gracefully handle this.
  // Suspending a Job will reset the StartTime field of the Job, effectively
  // resetting the ActiveDeadlineSeconds timer too. Defaults to false.
  //
  // +optional

## Reference

### Design details

Broadly, `istio-cni` accomplishes ambient redirection by instructing ztunnel to set up sockets within the application pod network namespace, where:

- one end of the socket is in the application pod

digraph { grpc -> ca [label="Send CSR gRPC Request"] subgraph cluster_istioagent { label = "Istio Agent" color="orange" sds SecretManager -> caClient [label="Sign CSR"] caClient -> grpc grpc -> TokenProvider [dir=none,label="Fetch JWT",color=purple] grpc -> cfiles [dir=none,label="Fetch Cert",color=purple] sds -> SecretManager [label="Generate certificate"] SecretManager -> cfiles [label="Write certs to file"] cfiles [label="Certificate Files"] grpc [shape=diamond] } subgraph cluster_istiod {...