See the License for the specific language governing permissions and
limitations under the License.
*/

package probe

import (
	"net"
	"syscall"
)

// ProbeDialer returns a dialer optimized for probes to avoid lingering sockets on TIME-WAIT state.
// The dialer reduces the TIME-WAIT period to 1 seconds instead of the OS default of 60 seconds.

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				// TCP starts sending keepalive probes
				_ = syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, syscall.TCP_KEEPIDLE, 15)

				// Number of probes.
				// ~ cat /proc/sys/net/ipv4/tcp_keepalive_probes (defaults to 9, we reduce it to 5)
				_ = syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, syscall.TCP_KEEPCNT, 5)

				// Wait time after successful probe in seconds.

	"io/fs"
	"os"
	"syscall"
)

// probe probes IPv4, IPv6 and IPv4-mapped IPv6 communication
// capabilities.
//
// Plan 9 uses IPv6 natively, see ip(3).
func (p *ipStackCapabilities) probe() {
	p.ipv4Enabled = probe(netdir+"/iproute", "4i")
	p.ipv6Enabled = probe(netdir+"/iproute", "6i")
	if p.ipv4Enabled && p.ipv6Enabled {
		p.ipv4MappedIPv6Enabled = true
	}
}

func probe(filename, query string) bool {
	var file *file

 *     See {@link org.gradle.internal.watch.registry.impl.NonHierarchicalFileWatcherUpdater}.</dd>
 *
 *     <dt>probed hierarchies</dt>
 *     <dd>The list of file system hierarchies that we've activated a file system probe for.
 *     We list every hierarchy here, even if there are ones nested inside others.
 *     See {@link FileWatcherProbeRegistry}.</dd>
 * </dl>
 */

kind: feature

area: traffic-management
issue: []

releaseNotes:
- |
  '**Improved** TCP probes now working as expected: When using TCP probes with older versions of istio the check was always successful, even if the application didn't open the port.'

upgradeNotes:
  - title: TCP probes now working as expected
    content: |

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