// with dead end because tcp-keepalive is not fired when there is data in the socket buffer.
			//    https://blog.cloudflare.com/when-tcp-sockets-refuse-to-die/
			// This is a sensitive configuration, it is better to set it to high values, > 60 secs since it can
			// affect clients reading data with a very slow pace  (disappropriate with socket buffer sizes)
			if opts.UserTimeout > 0 {

## CA Flow

istio-agent checks the presence of a socket file on the defined **socket path** `/var/run/secrets/workload-spiffe-uds/socket`.

* If a socket is found, istio-agent will not start its own SDS Server and Envoy will be configured to use that socket as its source of cryptographic material.

    assertThat(c1.socket().isClosed).isFalse()
    assertThat(c2.socket().isClosed).isFalse()

    // Add a third connection
    val c3 = factory.newConnection(pool, routeC1, 75L)

    // The third connection bounces the first.
    assertThat(pool.closeConnections(100L)).isEqualTo(0L)
    assertThat(pool.connectionCount()).isEqualTo(2)
    assertThat(c1.socket().isClosed).isTrue()

* nat
-N ISTIO_POSTRT
-A POSTROUTING -j ISTIO_POSTRT
-A ISTIO_POSTRT -m owner --socket-exists -p tcp -m set --match-set istio-inpod-probes-v4 dst -j SNAT --to-source 169.254.7.127
COMMIT
* nat
-N ISTIO_POSTRT
-A POSTROUTING -j ISTIO_POSTRT
-A ISTIO_POSTRT -m owner --socket-exists -p tcp -m set --match-set istio-inpod-probes-v6 dst -j SNAT --to-source fd16:9254:7127:1337:ffff:ffff:ffff:ffff

}

// TCPOptions specify customizable TCP optimizations on raw socket
type TCPOptions struct {
	UserTimeout int // this value is expected to be in milliseconds

	// When the net.Conn is a remote drive this value is honored, we close the connection to remote peer proactively.
	DriveOPTimeout func() time.Duration

	SendBufSize int              // SO_SNDBUF size for the socket connection, NOTE: this sets server and client connection

* nat
-N ISTIO_POSTRT
-A POSTROUTING -j ISTIO_POSTRT
-A ISTIO_POSTRT -m owner --socket-exists -p tcp -m set --match-set istio-inpod-probes-v4 dst -j SNAT --to-source 169.254.7.127

	//
	// We want to do the same thing in ambient but can't rely on podSpec injection. So, do effectively the same thing,
	// but with iptables rules - use `--socket-exists` as a proxy for "is this a forwarded packet" vs "is this originating from
	// a local node socket". If the latter, outside the pod in the host netns, redirect that traffic to a hardcoded/custom proxy

### 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.

net.ipv4.tcp_timestamps=0

# Increase throughput
net.ipv4.tcp_sack=1

# Low latency mode for TCP
net.ipv4.tcp_low_latency=1

# The following variable is used to tell the kernel how 
# much of the socket buffer space should be used for TCP 
# window size, and how much to save for an application buffer.
net.ipv4.tcp_adv_win_scale=1

# disable RFC2861 behavior
net.ipv4.tcp_slow_start_after_idle = 0

	CNIBinSourceDir string
	// Directories into which to copy the CNI binaries
	CNIBinTargetDirs []string

	// The HTTP port for monitoring
	MonitoringPort int

	// The ztunnel server socket address that the ztunnel will connect to.
	ZtunnelUDSAddress string

	// Whether ambient is enabled
	AmbientEnabled bool

	// Whether ambient DNS capture is enabled
	AmbientDNSCapture bool