# Istio Agent

This document describes the internal architecture of Istio agent.

## High Level overview

![High Level overview](docs/overview.svg)

At a high level, the Istio agent acts as an intermediate proxy between Istiod and Envoy. This is done
at two levels. For distributing workload certificates, Envoy will send [SDS](https://www.envoyproxy.io/docs/envoy/latest/configuration/security/secret)

	statusCmd.PersistentFlags().BoolVar(&multiXdsOpts.XdsViaAgents, "xds-via-agents", false,
		"Access Istiod via the tap service of each agent")
	statusCmd.PersistentFlags().IntVar(&multiXdsOpts.XdsViaAgentsLimit, "xds-via-agents-limit", 100,
		"Maximum number of pods being visited by istioctl when `xds-via-agent` flag is true."+
			"To iterate all the agent pods without limit, set to 0")

	return statusCmd

                    // The result would be something like DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'" \"-javaagent:$APP_HOME/lib/agents/foobar.jar\""
                    line + getAgentOptions("\$APP_HOME").joinToString(separator = " ", prefix = "\" ", postfix = "\"") {
                        // Wrap the agent switch in double quotes, as the expanded APP_HOME may contain spaces.

  @Test fun ofMapAcceptsEmptyValue() {
    val headers = mapOf("User-Agent" to "").toHeaders()
    assertThat(headers.value(0)).isEqualTo("")
  }

  @Test fun ofMapTrimsKey() {
    val headers = mapOf(" User-Agent " to "OkHttp").toHeaders()
    assertThat(headers.name(0)).isEqualTo("User-Agent")
  }

  @Test fun ofMapTrimsValue() {
    val headers = mapOf("User-Agent" to " OkHttp ").toHeaders()

    }

    public void test_getUserAgentType_IE9() {
        getMockRequest().addHeader("user-agent", "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.0; Trident/5.0)");
        assertEquals(UserAgentType.IE, userAgentHelper.getUserAgentType());
    }

    public void test_getUserAgentType_IE10() {
        getMockRequest().addHeader("user-agent", "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)");

public class UserAgentHelper {
    protected static final String USER_AGENT = "user-agent";

    protected static final String USER_AGENT_TYPE = "ViewHelper.UserAgent";

    public UserAgentType getUserAgentType() {
        return LaRequestUtil.getOptionalRequest().map(request -> {
            UserAgentType uaType = (UserAgentType) request.getAttribute(USER_AGENT_TYPE);
            if (uaType == null) {

@needs_py310
@pytest.mark.parametrize(
    "path,headers,expected_status,expected_response",
    [
        ("/items", None, 200, {"User-Agent": "testclient"}),
        ("/items", {"X-Header": "notvalid"}, 200, {"User-Agent": "testclient"}),
        ("/items", {"User-Agent": "FastAPI test"}, 200, {"User-Agent": "FastAPI test"}),
    ],
)
def test(path, headers, expected_status, expected_response, client: TestClient):

@pytest.mark.parametrize(
    "path,headers,expected_status,expected_response",
    [
        ("/items", None, 200, {"User-Agent": "testclient"}),
        ("/items", {"X-Header": "notvalid"}, 200, {"User-Agent": "testclient"}),
        ("/items", {"User-Agent": "FastAPI test"}, 200, {"User-Agent": "FastAPI test"}),
    ],
)
def test(path, headers, expected_status, expected_response):
    response = client.get(path, headers=headers)

@pytest.mark.parametrize(
    "path,headers,expected_status,expected_response",
    [
        ("/items", None, 200, {"User-Agent": "testclient"}),
        ("/items", {"X-Header": "notvalid"}, 200, {"User-Agent": "testclient"}),
        ("/items", {"User-Agent": "FastAPI test"}, 200, {"User-Agent": "FastAPI test"}),
    ],
)
def test(path, headers, expected_status, expected_response):
    response = client.get(path, headers=headers)

@needs_py310
@pytest.mark.parametrize(
    "path,headers,expected_status,expected_response",
    [
        ("/items", None, 200, {"User-Agent": "testclient"}),
        ("/items", {"X-Header": "notvalid"}, 200, {"User-Agent": "testclient"}),
        ("/items", {"User-Agent": "FastAPI test"}, 200, {"User-Agent": "FastAPI test"}),
    ],
)
def test(path, headers, expected_status, expected_response, client: TestClient):