+ Integer.toHexString(expected)
              + " got: "
              + Integer.toHexString(verification));
    }
  }

  static final Funnel<Object> BAD_FUNNEL =
      new Funnel<Object>() {
        @Override
        public void funnel(Object object, PrimitiveSink bytePrimitiveSink) {
          bytePrimitiveSink.putInt(object.hashCode());
        }
      };

  enum RandomHasherAction {

    HashFn hf =
        new HashFn() {
          @Override
          public byte[] hash(byte[] input, int seed) {
            Hasher hasher = murmur3_32(seed).newHasher();
            Funnels.byteArrayFunnel().funnel(input, hasher);
            return hasher.hash().asBytes();
          }
        };
    // Murmur3A, MurmurHash3 for x86, 32-bit (MurmurHash3_x86_32)

See [architecture doc](../architecture/ambient/ztunnel-cni-lifecycle.md).

## 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
- and the other end is in ztunnel's pod

and setting up iptables rules to funnel traffic thru that socket "tube" to ztunnel and back.

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If there is no waypoint, ztunnel will enforce RBAC policies against the request.

If all checks pass, ztunnel will open a connection to the target. This will spoof the source IP (from `Forwarded` for waypoints, or the incoming IP otherwise).
Once the connection is established we return a 200 HTTP code, and bi-directionally copy data to/from the tunnel to the destination.

## Certificates

local queries = (import './queries.libsonnet').queries({
  container: "istio-proxy",
  pod: "ztunnel-.*",
  component: "ztunnel",
  app: "ztunnel",
});

dashboard.new('Istio Ztunnel Dashboard')
+ g.dashboard.withPanels(
  grid.makeGrid([
    row.new('Process')
    + row.withPanels([
      panels.timeSeries.base('Ztunnel Versions', queries.istioBuild, 'Version number of each running instance'),

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

And here's an example of an authenticated request to a captured destination:

```mermaid
graph TD;
src[src pod]-->|15008|ztunnel{ztunnel}
ztunnel-->|HBONE|dwp{"destination waypoint (all policy applied here)"}

1. Immediately upon starting a drain, `ztunnel-old` will close its listeners. Now only `ztunnel-new` is listening. Critically, at all times there was at least one ztunnel listening.
1. While `ztunnel-old` will not accept *new* connections, it will continue processing existing connections.
1. After `drain period` seconds, `ztunnel-old` will forcefully terminate any outstanding connections.

> [!NOTE]

                  "type": "prometheus",
                  "uid": "$datasource"
               },
               "expr": "sum by (tag) (istio_build{component=\"ztunnel\"})",
               "legendFormat": "Version ({{tag}})"
            }
         ],
         "title": "Ztunnel Versions",
         "type": "timeseries"
      },
      {
         "datasource": {
            "type": "datasource",
            "uid": "-- Mixed --"