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]

    val get = server.takeRequest()
    assertThat(get.requestLine).isEqualTo("GET /foo HTTP/1.1")
    assertThat(get.headers["Proxy-Authorization"]).isNull()
  }

  // Don't disconnect after building a tunnel with CONNECT
  // http://code.google.com/p/android/issues/detail?id=37221
  @Test
  fun proxyWithConnectionClose() {
    server.useHttps(handshakeCertificates.sslSocketFactory())

    assertThat(get2.headers["Proxy-Authorization"]).isEqualTo("password")
  }

  /**
   * OkHttp has a bug where a `Connection: close` response header is not honored when establishing a
   * TLS tunnel. https://github.com/square/okhttp/issues/2426
   */
  @Test
  fun proxyAuthenticateOnConnectWithConnectionClose() {
    server.useHttps(handshakeCertificates.sslSocketFactory())

                  "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 --"

        .addEqualityGroup(Funnels.longFunnel())
        .addEqualityGroup(Funnels.unencodedCharsFunnel())
        .addEqualityGroup(Funnels.stringFunnel(UTF_8))
        .addEqualityGroup(Funnels.stringFunnel(US_ASCII))
        .addEqualityGroup(
            Funnels.sequentialFunnel(Funnels.integerFunnel()),
            SerializableTester.reserialize(Funnels.sequentialFunnel(Funnels.integerFunnel())))

      Funnel<? super T> funnel, long expectedInsertions, double fpp) {
    return create(funnel, expectedInsertions, fpp, BloomFilterStrategies.MURMUR128_MITZ_64);
  }

  @VisibleForTesting
  static <T extends @Nullable Object> BloomFilter<T> create(
      Funnel<? super T> funnel, long expectedInsertions, double fpp, Strategy strategy) {
    checkNotNull(funnel);
    checkArgument(

        .addEqualityGroup(BloomFilter.create(Funnels.byteArrayFunnel(), 100, 0.01))
        .addEqualityGroup(BloomFilter.create(Funnels.byteArrayFunnel(), 100, 0.02))
        .addEqualityGroup(BloomFilter.create(Funnels.byteArrayFunnel(), 200, 0.01))
        .addEqualityGroup(BloomFilter.create(Funnels.byteArrayFunnel(), 200, 0.02))
        .addEqualityGroup(BloomFilter.create(Funnels.unencodedCharsFunnel(), 100, 0.01))

### **Cluster Lifecycle**

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.

    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)