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.

## 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

  // 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

FROM ubuntu:noble

ENV DEBIAN_FRONTEND=noninteractive

# Do not add more stuff to this list that isn't small or critically useful.
# If you occasionally need something on the container do
# sudo apt-get update && apt-get whichever

# hadolint ignore=DL3005,DL3008
RUN apt-get update && \
  apt-get install --no-install-recommends -y \
  ca-certificates \
  curl \
  iptables \
  iproute2 \
  iputils-ping \
  knot-dnsutils \

  // 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
//

  // At least one of ipv4 and ipv6 must be specified.
  // This field is immutable.
  // +optional
  optional string ipv6 = 4;
}

// IPAddress represents a single IP of a single IP Family. The object is designed to be used by APIs
// that operate on IP addresses. The object is used by the Service core API for allocation of IP addresses.
// An IP address can be represented in different formats, to guarantee the uniqueness of the IP,

These are replaced by this chart.
While not required, it is recommended all new users use this chart, and existing users migrate when possible.

This chart has the following benefits and differences:
* Designed with Helm best practices in mind (standardized values options, values schema, values are not all nested under `gateways.istio-ingressgateway.*`, release name and namespace taken into account, etc).

  // +optional
  optional ParamKind paramKind = 1;

  // MatchConstraints specifies what resources this policy is designed to validate.
  // The AdmissionPolicy cares about a request if it matches _all_ Constraints.
  // However, in order to prevent clusters from being put into an unstable state that cannot be recovered from via the API