Istio中的流量配置
-
Istio中的流量配置
-
Istio注入的容器
- Envoy架构
- Pilot-agent生成的初始配置文件
- Envoy管理接口获取的完整配置
- SDS
- 参考
Istio注入的容器
Istio的数据面会在pod中注入两个容器：istio-init和istio-proxy。
Istio-init
istio-init会通过创建iptables规则来接管流量：
-
命令行参数 -p 15001表示出向流量被iptable重定向到Envoy的15001端口
-
命令行参数 -z 15006表示入向流量被iptable重定向到Envoy的15006端口
-
命令行参数 -u 1337参数用于排除用户ID为1337，即Envoy自身的流量，以避免Iptable把Envoy发出的数据又重定向到Envoy，形成死循环。在istio-proxy容器中执行如下命令可以看到Envoy使用的用户id为1337。
$ id
uid=1337(istio-proxy) gid=1337(istio-proxy) groups=1337(istio-proxy)
istio-iptables
-p
15001
-z
15006
-u
1337
-m
REDIRECT
-i
*
-x
-b
*
-d
15090,15021,15020
--run-validation
--skip-rule-apply
istio-proxy
istio-proxy容器中会运行两个程序：pilot-agent和envoy。
$ ps -ef|cat
UID PID PPID C STIME TTY TIME CMD
istio-p+ 1 0 0 Sep10 ? 00:03:39 /usr/local/bin/pilot-agent proxy sidecar --domain default.svc.cluster.local --serviceCluster sleep.default --proxyLogLevel=warning --proxyComponentLogLevel=misc:error --trust-domain=cluster.local --concurrency 2
istio-p+ 27 1 0 Sep10 ? 00:14:30 /usr/local/bin/envoy -c etc/istio/proxy/envoy-rev0.json --restart-epoch 0 --drain-time-s 45 --parent-shutdown-time-s 60 --service-cluster sleep.default --service-node sidecar~10.80.3.109~sleep-856d589c9b-x6szk.default~default.svc.cluster.local --local-address-ip-version v4 --log-format-prefix-with-location 0 --log-format %Y-%m-%dT%T.%fZ.%l.envoy %n.%v -l warning --component-log-level misc:error --concurrency 2
Envoy架构
Envoy对入站/出站请求的处理过程如下，Envoy按照如下顺序依次在各个过滤器中处理请求。
典型的入站请求流程如下，首先在监听过滤器链中解析入站报文中的TLS，然后通过传输socket建立连接，最后由网络过滤器链进行处理(含HTTP连接管理器)。
Pilot-agent生成的初始配置文件
pilot-agent根据启动参数和K8S API Server中的配置信息生成Envoy的bootstrap文件(/etc/istio/proxy/envoy-rev0.json)，并负责启动Envoy进程(可以看到Envoy进程的父进程是pilot-agent)；envoy会通过xDS接口从istiod动态获取配置文件。envoy-rev0.json初始配置文件结构如下：
-
node：给出了Envoy 实例的信息
"node": {
"id": "sidecar~10.80.3.109~sleep-856d589c9b-x6szk.default~default.svc.cluster.local","cluster": "sleep.default","locality": {
},"metadata": {"APP_CONTAINERS":"sleep,istio-proxy","CLUSTER_ID":"Kubernetes","EXCHANGE_KEYS":"NAME,NAMESPACE,INSTANCE_IPS,LABELS,OWNER,PLATFORM_METADATA,WORKLOAD_NAME,MESH_ID,SERVICE_ACCOUNT,CLUSTER_ID","INSTANCE_IPS":"10.80.3.109,fe80::40fb:daff:feed:e56c","INTERCEPTION_MODE":"REDIRECT","ISTIO_PROXY_SHA":"istio-proxy:f642a7fd07d0a99944a6e3529566e7985829839c","ISTIO_VERSION":"1.7.0","LABELS":{"app":"sleep","istio.io/rev":"default","pod-template-hash":"856d589c9b","security.istio.io/tlsMode":"istio","service.istio.io/canonical-name":"sleep","service.istio.io/canonical-revision":"latest"},"MESH_ID":"cluster.local","NAME":"sleep-856d589c9b-x6szk","NAMESPACE":"default","OWNER":"kubernetes://apis/apps/v1/namespaces/default/deployments/sleep","POD_PORTS":"[{"name":"http-envoy-prom","containerPort":15090,"protocol":"TCP"}]","PROXY_CONFIG":{"binaryPath":"/usr/local/bin/envoy","concurrency":2,"configPath":"./etc/istio/proxy","controlPlaneAuthPolicy":"MUTUAL_TLS","discoveryAddress":"istiod.istio-system.svc:15012","drainDuration":"45s","envoyAccessLogService":{},"envoyMetricsService":{},"parentShutdownDuration":"60s","proxyAdminPort":15000,"proxyMetadata":{"DNS_AGENT":""},"serviceCluster":"sleep.default","statNameLength":189,"statusPort":15020,"terminationDrainDuration":"5s","tracing":{"zipkin":{"address":"zipkin.istio-system:9411"}}},"SDS":"true","SERVICE_ACCOUNT":"sleep","WORKLOAD_NAME":"sleep","k8s.v1.cni.cncf.io/networks":"istio-cni","sidecar.istio.io/interceptionMode":"REDIRECT","sidecar.istio.io/status":"{"version":"8e6e902b765af607513b28d284940ee1421e9a0d07698741693b2663c7161c11","initContainers":["istio-validation"],"containers":["istio-proxy"],"volumes":["istio-envoy","istio-data","istio-podinfo","istiod-ca-cert"],"imagePullSecrets":null}","traffic.sidecar.istio.io/excludeInboundPorts":"15020","traffic.sidecar.istio.io/includeOutboundIPRanges":"*"}
},
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admin：给出了Envoy的日志路径和管理端口，例如可以通过curl -X POST localhost:15000/logging?level=trace设置日志级别为trace。
"admin": {
"access_log_path": "/dev/null",/* 管理服务器的访问日志路径 */
"profile_path": "/var/lib/istio/data/envoy.prof",/* 管理服务器的CPU输出路径 */
"address": { /* 管理服务器监听的TCP地址 */
"socket_address": {
"address": "127.0.0.1","port_value": 15000
}
}
},
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dynamic_resources：配置动态资源，用于配置lds_config，cds_config和ads_config
Envoy通过xds-grpc cluster(参见static_resources)来获得xDS服务的地址。
"dynamic_resources": {
"lds_config": { /* 通过一个LDS配置Listeners */
"ads": {},"resource_api_version": "V3" /* LDS使用的API版本号 */
},"cds_config": { /* 通过一个CDS配置Cluster */
"ads": {},"resource_api_version": "V3"
},"ads_config": { /* API配置资源，用于指定API类型和Envoy获取xDS API的cluster */
"api_type": "GRPC",/* 使用GRPC获取xDS信息 */
"transport_api_version": "V3",/* xDS传输协议的版本号 */
"grpc_services": [
{
"envoy_grpc": {
"cluster_name": "xds-grpc" /* 动态获取xDS配置的cluster */
}
}
]
}
},
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static_resources：配置静态资源，主要包括clusters和listeners两种资源：
-
clusters：下面给出了几个静态配置的cluster。
"clusters": [
{
"name": "prometheus_stats",/* 使用Prometheus暴露metrics，接口为127.0.0.1:15000/stats/prometheus */
"type": "STATIC",/* 明确指定上游host的网络名(IP地址/端口等) */
"connect_timeout": "0.250s","lb_policy": "ROUND_ROBIN","load_assignment": { /* 仅用于类型为STATIC,STRICT_DNS或LOGICAL_DNS，用于给非EDS的clyster内嵌与EDS等同的endpoint */
"cluster_name": "prometheus_stats","endpoints": [{
"lb_endpoints": [{ /* 负载均衡的后端 */
"endpoint": {
"address":{
"socket_address": {
"protocol": "TCP","address": "127.0.0.1","port_value": 15000
}
}
}
}]
}]
}
},{
"name": "agent",/* 暴露健康检查接口，可以使用curl http://127.0.0.1:15020/healthz/ready -v查看 */
"type": "STATIC","connect_timeout": "0.250s","load_assignment": {
"cluster_name": "prometheus_stats","port_value": 15020
}
}
}
}]
}]
}
},{
"name": "sds-grpc",/* 配置SDS cluster */
"type": "STATIC","http2_protocol_options": {},"connect_timeout": "1s","load_assignment": {
"cluster_name": "sds-grpc","endpoints": [{
"lb_endpoints": [{
"endpoint": {
"address":{
"pipe": {
"path": "./etc/istio/proxy/SDS" /* 进行SDS的UNIX socket路径，用于在mTLS期间给istio-agent和proxy提供通信 */
}
}
}
}]
}]
}
},{
"name": "xds-grpc",/* 动态xDS使用的grpc服务器配置 */
"type": "STRICT_DNS","respect_dns_ttl": true,"dns_lookup_family": "V4_ONLY","transport_socket": { /* 配置与上游连接的传输socket */
"name": "envoy.transport_sockets.tls",/* 需要实例化的传输socket名称 */
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext","sni": "istiod.istio-system.svc",/* 创建TLS后端(即SDS服务器)连接时要使用的SNI字符串 */
"common_tls_context": { /* 配置client和server使用的TLS上下文 */
"alpn_protocols": [/* listener暴露的ALPN协议列表，如果为空，则不使用APPN */
"h2"
],"tls_certificate_sds_secret_configs": [/*通过SDS API获取TLS证书的配置 */
{
"name": "default","sds_config": { /* 配置sds_config时将会从静态资源加载secret */
"resource_api_version": "V3",/* xDS的API版本 */
"initial_fetch_timeout": "0s","api_config_source": { /* SDS API配置，如版本和SDS服务 */
"api_type": "GRPC","transport_api_version": "V3",/* xDS传输协议的API版本 */
"grpc_services": [
{ /* SDS服务器对应上面配置的sds-grpc cluster */
"envoy_grpc": { "cluster_name": "sds-grpc" }
}
]
}
}
}
],"validation_context": {
"trusted_ca": {
"filename": "./var/run/secrets/istio/root-cert.pem" /* 本地文件系统的数据源。挂载当前命名空间下的config istio-ca-root-cert，其中的CA证书与istio-system命名空间下的istio-ca-secret中的CA证书相同，用于校验对端istiod的证书 */
},"match_subject_alt_names": [{"exact":"istiod.istio-system.svc"}] /* 验证证书中的SAN，即来自istiod的证书 */
}
}
}
},"load_assignment": {
"cluster_name": "xds-grpc",/* 可以看到xds-grpc的后端为istiod的15012端口 */
"endpoints": [{
"lb_endpoints": [{
"endpoint": {
"address":{
"socket_address": {"address": "istiod.istio-system.svc","port_value": 15012}
}
}
}]
}]
},"circuit_breakers": { /* 断路器配置 */
"thresholds": [
{
"priority": "DEFAULT","max_connections": 100000,"max_pending_requests": 100000,"max_requests": 100000
},{
"priority": "HIGH","max_requests": 100000
}
]
},"upstream_connection_options": {
"tcp_keepalive": {
"keepalive_time": 300
}
},"max_requests_per_connection": 1,"http2_protocol_options": { }
},{
"name": "zipkin",/* 分布式链路跟踪zipkin的cluster配置 */
"type": "STRICT_DNS","load_assignment": {
"cluster_name": "zipkin","endpoints": [{
"lb_endpoints": [{
"endpoint": {
"address":{
"socket_address": {"address": "zipkin.istio-system","port_value": 9411}
}
}
}]
}]
}
}
],
上面使用type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext API接口来对传输socket进行配置，sni和common_tls_context 都属于结构体UpstreamTlsContext中的成员变量。
可以使用istioctl pc cluster命令查看静态cluster资源，第一列对应上面的Cluster.name，其中sds-grpc用于提供SDS服务，SDS的原理可以参见官方文档。
# istioctl pc cluster sleep-856d589c9b-x6szk.default |grep STATIC
BlackHoleCluster - - - STATIC
agent - - - STATIC
prometheus_stats - - - STATIC
sds-grpc - - - STATIC
sleep.default.svc.cluster.local 80 http inbound STATIC
-
listener，下面用到了Network filter中的HTTP connection manager
"listeners":[
{
"address": { /* listener监听的地址 */
"socket_address": {
"protocol": "TCP","address": "0.0.0.0","port_value": 15090
}
},"filter_chains": [
{
"filters": [
{
"name": "envoy.http_connection_manager","typed_config": { /* 对扩展API的配置 */
"@type": "type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager","codec_type": "AUTO",/* 由连接管理器判断使用哪种编解码器 */
"stat_prefix": "stats","route_config": { /* 连接管理器的静态路由表 */
"virtual_hosts": [ /* 路由表使用的虚拟主机列表 */
{
"name": "backend",/* 路由表使用的虚拟主机 */
"domains": [ /* 匹配该虚拟主机的域列表 */
"*"
],"routes": [ /* 匹配入请求的路由列表，使用第一个匹配的路由 */
{
"match": { /* 将HTTP地址为/stats/prometheus的请求路由到cluster prometheus_stats */
"prefix": "/stats/prometheus"
},"route": {
"cluster": "prometheus_stats"
}
}
]
}
]
},"http_filters": [{ /* 构成filter链的filter，用于处理请求。此处并没有定义任何规则 */
"name": "envoy.router","typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.http.router.v3.Router"
}
}]
}
}
]
}
]
},{
"address": {
"socket_address": {
"protocol": "TCP","port_value": 15021
}
},"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager","stat_prefix": "agent","route_config": { /* 静态路由表配置 */
"virtual_hosts": [
{
"name": "backend","domains": [
"*"
],"routes": [
{
"match": { /* 将HTTP地址为/healthz/ready的请求路由到cluster agent */
"prefix": "/healthz/ready"
},"route": {
"cluster": "agent"
}
}
]
}
]
},"http_filters": [{
"name": "envoy.router","typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.http.router.v3.Router"
}
}]
}
}
]
}
]
}
]
}
-
tracing，对应上面static_resources里定义的zipkin cluster。
"tracing": {
"http": {
"name": "envoy.zipkin","typed_config": {
"@type": "type.googleapis.com/envoy.config.trace.v3.ZipkinConfig","collector_cluster": "zipkin","collector_endpoint": "/api/v2/spans","collector_endpoint_version": "HTTP_JSON","trace_id_128bit": true,"shared_span_context": false
}
}
}
基本流程如下：
Envoy管理接口获取的完整配置
可以在注入Envoy sidecar的pod中执行curl -X POST localhost:15000/config_dump来获取完整的配置信息。可以看到它主要包含BootstrapConfig，ClustersConfig，ListenersConfig，RoutesConfig，SecretsConfig这5部分。
-
Bootstrap：它与上面由Pilot-agent生成的envoy-rev0.json文件中的内容相同，即提供给Envoy proxy的初始化配置，给出了xDS服务器的地址等信息。
-
Clusters：在Envoy中，Cluster是一个服务集群，每个cluster包含一个或多个endpoint(可以将cluster近似看作是k8s中的service)。
从上图可以看出，ClustersConfig包含两种cluster配置：static_clusters和dynamic_active_clusters。前者中的cluster来自envoy-rev0.json中配置的静态cluster资源，包含agent，prometheus_stats，sds-grpc，xds-grpc和zipkin；后者是通过xDS接口从istio的控制面获取的动态配置信息，dynamic_active_clusters主要分为如下四种类型：
-
BlackHoleCluster：
"cluster": {
"@type": "type.googleapis.com/envoy.config.cluster.v3.Cluster","name": "BlackHoleCluster",/* cluster名称 */
"type": "STATIC","connect_timeout": "10s","filters": [ /* 出站连接的过滤器配置 */
{
"name": "istio.metadata_exchange","typed_config": { /* 对扩展API的配置 */
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct","type_url": "type.googleapis.com/envoy.tcp.metadataexchange.config.MetadataExchange","value": {
"protocol": "istio-peer-exchange"
}
}
}
]
},
BlackHoleCluster使用的API类型为type.googleapis.com/udpa.type.v1.TypedStruct，表示控制面缺少缺少该扩展的模式定义，client会使用type_url指定的API，将内容转换为类型化的配置资源。
在上面可以看到Istio使用了协议istio-peer-exchange ，服务网格内部的两个Envoy实例之间使用该协议来交互Node Metadata。NodeMetadata的数据结构如下：
type NodeMetadata struct {
// ProxyConfig defines the proxy config specified for a proxy.
// Note that this setting may be configured different for each proxy,due user overrides
// or from different versions of proxies connecting. While Pilot has access to the meshConfig.defaultConfig,// this field should be preferred if it is present.
ProxyConfig *NodeMetaProxyConfig `json:"PROXY_CONFIG,omitempty"`
// IstioVersion specifies the Istio version associated with the proxy
IstioVersion string `json:"ISTIO_VERSION,omitempty"`
// Labels specifies the set of workload instance (ex: k8s pod) labels associated with this node.
Labels map[string]string `json:"LABELS,omitempty"`
// InstanceIPs is the set of IPs attached to this proxy
InstanceIPs StringList `json:"INSTANCE_IPS,omitempty"`
// Namespace is the namespace in which the workload instance is running.
Namespace string `json:"NAMESPACE,omitempty"`
// InterceptionMode is the name of the metadata variable that carries info about
// traffic interception mode at the proxy
InterceptionMode TrafficInterceptionMode `json:"INTERCEPTION_MODE,omitempty"`
// ServiceAccount specifies the service account which is running the workload.
ServiceAccount string `json:"SERVICE_ACCOUNT,omitempty"`
// RouterMode indicates whether the proxy is functioning as a SNI-DNAT router
// processing the AUTO_PASSTHROUGH gateway servers
RouterMode string `json:"ROUTER_MODE,omitempty"`
// MeshID specifies the mesh ID environment variable.
MeshID string `json:"MESH_ID,omitempty"`
// ClusterID defines the cluster the node belongs to.
ClusterID string `json:"CLUSTER_ID,omitempty"`
// Network defines the network the node belongs to. It is an optional metadata,// set at injection time. When set,the Endpoints returned to a note and not on same network
// will be replaced with the gateway defined in the settings.
Network string `json:"NETWORK,omitempty"`
// RequestedNetworkView specifies the networks that the proxy wants to see
RequestedNetworkView StringList `json:"REQUESTED_NETWORK_VIEW,omitempty"`
// PodPorts defines the ports on a pod. This is used to lookup named ports.
PodPorts PodPortList `json:"POD_PORTS,omitempty"`
// TLSServerCertChain is the absolute path to server cert-chain file
TLSServerCertChain string `json:"TLS_SERVER_CERT_CHAIN,omitempty"`
// TLSServerKey is the absolute path to server private key file
TLSServerKey string `json:"TLS_SERVER_KEY,omitempty"`
// TLSServerRootCert is the absolute path to server root cert file
TLSServerRootCert string `json:"TLS_SERVER_ROOT_CERT,omitempty"`
// TLSClientCertChain is the absolute path to client cert-chain file
TLSClientCertChain string `json:"TLS_CLIENT_CERT_CHAIN,omitempty"`
// TLSClientKey is the absolute path to client private key file
TLSClientKey string `json:"TLS_CLIENT_KEY,omitempty"`
// TLSClientRootCert is the absolute path to client root cert file
TLSClientRootCert string `json:"TLS_CLIENT_ROOT_CERT,omitempty"`
CertBaseDir string `json:"BASE,omitempty"`
// IdleTimeout specifies the idle timeout for the proxy,in duration format (10s).
// If not set,no timeout is set.
IdleTimeout string `json:"IDLE_TIMEOUT,omitempty"`
// HTTP10 indicates the application behind the sidecar is making outbound http requests with HTTP/1.0
// protocol. It will enable the "AcceptHttp_10" option on the http options for outbound HTTP listeners.
// Alpha in 1.1,based on feedback may be turned into an API or change. Set to "1" to enable.
HTTP10 string `json:"HTTP10,omitempty"`
// Generator indicates the client wants to use a custom Generator plugin.
Generator string `json:"GENERATOR,omitempty"`
// DNSCapture indicates whether the workload has enabled dns capture
DNSCapture string `json:"DNS_CAPTURE,omitempty"`
// ProxyXDSViaAgent indicates that xds data is being proxied via the agent
ProxyXDSViaAgent string `json:"PROXY_XDS_VIA_AGENT,omitempty"`
// Contains a copy of the raw metadata. This is needed to lookup arbitrary values.
// If a value is known ahead of time it should be added to the struct rather than reading from here,Raw map[string]interface{} `json:"-"`
}
Istio通过一些特定的TCP属性来启用TCP策略和控制(这些属性由Envoy代理生成)，并通过Envoy的Node Metadata来获取这些属性。Envoy使用ALPN隧道和基于前缀的协议来转发Node Metadata到对端的Envoy。Istio定义了一个新的协议istio-peer-exchange，由网格中的客户端和服务端的sidecar在TLS协商时进行宣告并确定优先级。启用istio代理的两端会通过ALPN协商将协议解析为istio-peer-exchange(因此仅限于istio服务网格内的交互)，后续的TCP交互将会按照istio-peer-exchange的协议规则进行交互：
使用如下命令可以看到cluster BlackHoleCluster是没有endpoint的。
# istioctl pc endpoint sleep-856d589c9b-x6szk.default --cluster BlackHoleCluster
ENDPOINT STATUS OUTLIER CHECK CLUSTER
如下内容参考官方博客：
对于外部服务，Istio提供了两种管理方式：通过将global.outboundTrafficPolicy.mode 设置为REGISTRY_ONLY来block所有到外部服务的访问；以及通过将global.outboundTrafficPolicy.mode设置为ALLOW_ANY来允许所有到外部服务的访问。默认会允许所有到外部服务的访问。
BlackHoleCluster ：当global.outboundTrafficPolicy.mode设置为REGISTRY_ONLY时，Envoy会创建一个虚拟的cluster BlackHoleCluster。该模式下，所有到外部服务的访问都会被block(除非为每个服务添加service entries)。为了实现该功能，默认的outbound listener(监听地址为 0.0.0.0:15001)使用原始目的地来设置TCP代理，BlackHoleCluster 作为一个静态cluster。由于BlackHoleCluster 没有任何endpoint，因此会丢弃所有到外部的流量。此外，Istio会为平台服务的每个端口/协议组合创建唯一的listener，如果对同一端口的外部服务发起请求，则不会命中虚拟listener。这种情况会对route配置进行扩展，添加到BlackHoleCluster的路由。如果没有匹配到其他路由，则Envoy代理会直接返回502 HTTP状态码(BlackHoleCluster可以看作是路由黑洞)。
{
"name": "block_all","domains": [
"*"
],"routes": [
{
"match": {
"prefix": "/"
},"direct_response": {
"status": 502
},"name": "block_all"
}
],"include_request_attempt_count": true
},
-
PassthroughCluster：可以看到PassthroughCluster也使用了istio-peer-exchange协议来处理TCP。
"cluster": {
"@type": "type.googleapis.com/envoy.config.cluster.v3.Cluster","name": "PassthroughCluster","type": "ORIGINAL_DST",/* 指定type为ORIGINAL_DST，这是一个特殊的cluster */
"connect_timeout": "10s","lb_policy": "CLUSTER_PROVIDED","circuit_breakers": {
"thresholds": [
{
"max_connections": 4294967295,"max_pending_requests": 4294967295,"max_requests": 4294967295,"max_retries": 4294967295
}
]
},"protocol_selection": "USE_DOWNSTREAM_PROTOCOL","filters": [
{
"name": "istio.metadata_exchange",/* 配置使用ALPN istio-peer-exchange协议来交换Node Metadata */
"typed_config": {
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct",
使用如下命令可以看到cluster PassthroughCluster是没有endpoint的。
# istioctl pc endpoint sleep-856d589c9b-x6szk.default --cluster PassthroughCluster
ENDPOINT STATUS OUTLIER CHECK CLUSTER
PassthroughCluster ：当global.outboundTrafficPolicy.mode设置为ALLOW_ANY时，Envoy会创建一个虚拟的cluster PassthroughCluster 。该模式下，会允许所有到外部服务的访问。为了实现该功能，默认的outbound listener(监听地址为 0.0.0.0:15001)使用SO_ORIGINAL_DST来配置TCP Proxy，PassthroughCluster作为一个静态cluster。
PassthroughCluster cluster使用原始目的地负载均衡策略来配置Envoy发送到原始目的地的流量。
与BlackHoleCluster类似，对于每个基于端口/协议的listener，都会添加虚拟路由，将PassthroughCluster作为为默认路由。
{
"name": "allow_any","domains": [
"*"
],"routes": [
{
"match": {
"prefix": "/"
},"route": {
"cluster": "PassthroughCluster","timeout": "0s","max_grpc_timeout": "0s"
},"name": "allow_any"
}
],"include_request_attempt_count": true
},
由于global.outboundTrafficPolicy.mode只能配置某一个值，因此BlackHoleCluster和PassthroughCluster的出现是互斥的，BlackHoleCluster和PassthroughCluster的路由仅存在istio服务网格内，即注入sidecar的pod中。
可以使用Prometheus metrics来监控到BlackHoleCluster和PassthroughCluster的访问。
-
inbound cluster：处理入站请求的cluster，对于下面的sleep应用来说，其只有一个本地后端127.0.0.1:80，并通过load_assignment指定了cluster名称和负载信息。由于该监听器上的流量不会出战，因此下面并没有配置过滤器。
"cluster": {
"@type": "type.googleapis.com/envoy.config.cluster.v3.Cluster","name": "inbound|80|http|sleep.default.svc.cluster.local","type": "STATIC","circuit_breakers": {
"thresholds": [
{
"max_connections": 4294967295,"max_retries": 4294967295
}
]
},"load_assignment": { /* 设置入站的cluster的endpoint的负载均衡 */
"cluster_name": "inbound|80|http|sleep.default.svc.cluster.local","endpoints": [
{
"lb_endpoints": [
{
"endpoint": {
"address": {
"socket_address": {
"address": "127.0.0.1","port_value": 80
}
}
}
}
]
}
]
}
},
也可以使用如下命令查看inbound的cluster信息：
# istioctl pc cluster sleep-856d589c9b-c6xsm.default --direction inbound
SERVICE FQDN PORT SUBSET DIRECTION TYPE DESTINATION RULE
sleep.default.svc.cluster.local 80 http inbound STATIC
-
outbound cluster：这类cluster为Envoy节点外的服务，配置如何连接上游。下面的EDS表示该cluster的endpoint来自EDS服务发现。下面给出的outbound cluster是istiod的15012端口上的服务。基本结构如下，transport_socket_matches仅在使用TLS才会出现，用于配置与TLS证书相关的信息。
可以使用istioctl pc endpoint查看EDS的内容
# istioctl pc endpoint sleep-856d589c9b-rn7dw.default --cluster "outbound|15012||istiod.istio-system.svc.cluster.local"
ENDPOINT STATUS OUTLIER CHECK CLUSTER
10.80.3.141:15012 HEALTHY OK outbound|15012||istiod.istio-system.svc.cluster.local
具体内容如下：
{
"version_info": "2020-09-15T08:05:54Z/4","cluster": {
"@type": "type.googleapis.com/envoy.config.cluster.v3.Cluster","name": "outbound|15012||istiod.istio-system.svc.cluster.local","type": "EDS","eds_cluster_config": { /* EDS的配置 */
"eds_config": {
"ads": {},"resource_api_version": "V3"
},"service_name": "outbound|15012||istiod.istio-system.svc.cluster.local" /* EDS的cluster的可替代名称，无需与cluster名称完全相同 */
},"circuit_breakers": { /* 断路器设置 */
"thresholds": [
{
"max_connections": 4294967295,"filters": [ /* 设置Node Metadata交互使用的协议为istio-peer-exchange */
{
"name": "istio.metadata_exchange","typed_config": {
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct","value": {
"protocol": "istio-peer-exchange"
}
}
}
],"transport_socket_matches": [ /* 指定匹配的后端使用的带TLS的传输socket */
{
"name": "tlsMode-istio",/* match的名称 */
"match": { /* 匹配后端的条件，注入istio sidecar的pod会打上标签：security.istio.io/tlsMode=istio */
"tlsMode": "istio"
},"transport_socket": { /* 匹配cluster的后端使用的传输socket的配置 */
"name": "envoy.transport_sockets.tls","typed_config": {
"@type": "type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext","common_tls_context": { /* 配置client和server端使用的TLS上下文 */
"alpn_protocols": [ /* 配置交互使用的ALPN协议集，供上游选择 */
"istio-peer-exchange","istio"
],"tls_certificate_sds_secret_configs": [ /* 通过SDS API获取TLS证书的配置 */
{
"name": "default","sds_config": {
"api_config_source": {
"api_type": "GRPC","grpc_services": [ /* SDS的cluster */
{
"envoy_grpc": {
"cluster_name": "sds-grpc" /* 为上面静态配置的cluster */
}
}
],"transport_api_version": "V3"
},"initial_fetch_timeout": "0s","resource_api_version": "V3"
}
}
],"combined_validation_context": { /* 包含一个CertificateValidationContext(即下面的default_validation_context)和SDS配置。当SDS服务返回动态的CertificateValidationContext时，动态和默认的CertificateValidationContext会合并为一个新的CertificateValidationContext来进行校验 */
"default_validation_context": { /* 配置如何认证对端istiod服务的证书 */
"match_subject_alt_names": [ /* Envoy会按照如下配置来校验证书中的SAN */
{
"exact": "spiffe://new-td/ns/istio-system/sa/istiod-service-account" /* Istio数据面使用serviceaccount进行授权 */
}
]
},"validation_context_sds_secret_config": { /* SDS配置，也是通过静态的cluster sds-grpc提供SDS API服务 */
"name": "ROOTCA",/* 用于认证对端的CA证书， */
"sds_config": {
"api_config_source": {
"api_type": "GRPC","grpc_services": [
{
"envoy_grpc": {
"cluster_name": "sds-grpc" /* 获取该CA证书的SDS服务器 */
}
}
],"resource_api_version": "V3"
}
}
}
},"sni": "outbound_.15012_._.istiod.istio-system.svc.cluster.local" /* 创建TLS连接时使用的SNI字符串，即TLS的server_name扩展字段中的值 */
}
}
},{
"name": "tlsMode-disabled",/* 如果与没有匹配到的后端(即istio服务网格外的后端)进行通信时，则使用明文方式 */
"match": {},"transport_socket": {
"name": "envoy.transport_sockets.raw_buffer"
}
}
]
},"last_updated": "2020-09-15T08:06:23.565Z"
},
-
Listeners：Envoy使用listener来接收并处理下游发来的请求。与cluster类似，listener也分为静态和动态两种配置。静态配置来自Istio-agent生成的envoy-rev0.json文件。动态配置为：
-
virtualOutbound Listener：Istio在注入sidecar时，会通过init容器来设置iptables规则，将所有出站的TCP流量拦截到本地的15001端口：
-A ISTIO_REDIRECT -p tcp -j REDIRECT --to-ports 15001
一个istio-agent配置中仅包含一个virtualOutbound listener，可以看到该listener并没有配置transport_socket，它的下游流量就是来自本pod的业务容器，并不需要进行TLS校验，直接将流量重定向到15001端口即可，然后转发给和原始目的IP:Port匹配的listener。
{
"name": "virtualOutbound","active_state": {
"version_info": "2020-09-15T08:05:54Z/4","listener": {
"@type": "type.googleapis.com/envoy.config.listener.v3.Listener","name": "virtualOutbound","address": { /* 监听器监听的地址 */
"socket_address": {
"address": "0.0.0.0","port_value": 15001
}
},"filter_chains": [ /* 应用到该监听器的过滤器链 */
{
"filters": [ /* 与该监听器建立连接时使用的过滤器，按顺序处理各个过滤器。如果过滤器列表为空，则默认会关闭连接 */
{
"name": "istio.stats","typed_config": {
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct","type_url": "type.googleapis.com/envoy.extensions.filters.network.wasm.v3.Wasm","value": {
"config": { /* Wasm插件配置 */
"root_id": "stats_outbound",/* 一个VM中具有相同root_id的一组filters/services会共享相同的RootContext和Contexts，如果该字段为空，所有该字段为空的filters/services都会共享具有相同vm_id的Context(s) */
"vm_config": { /* Wasm VM的配置 */
"vm_id": "tcp_stats_outbound",/* 使用相同vm_id和code将使用相同的VM */
"runtime": "envoy.wasm.runtime.null",/* Wasm运行时，v8或null */
"code": {
"local": {
"inline_string": "envoy.wasm.stats"
}
}
},"configuration": {
"@type": "type.googleapis.com/google.protobuf.StringValue","value": "{n "debug": "false",n "stat_prefix": "istio"n}n"
}
}
}
}
},{
"name": "envoy.tcp_proxy",/* 处理TCP的过滤器 */
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.network.tcp_proxy.v3.TcpProxy","stat_prefix": "PassthroughCluster","cluster": "PassthroughCluster",/* 连接的上游cluster */
"access_log": [
{
"name": "envoy.file_access_log","typed_config": { /* 配置日志的输出格式和路径 */
"@type": "type.googleapis.com/envoy.extensions.access_loggers.file.v3.FileAccessLog","path": "/dev/stdout","format": "[%START_TIME%] "%REQ(:METHOD)% %REQ(X-ENVOY-ORIGINAL-PATH?:PATH)% %PROTOCOL%" %RESPONSE_CODE% %RESPONSE_FLAGS% "%DYNAMIC_METADATA(istio.mixer:status)%" "%UPSTREAM_TRANSPORT_FAILURE_REASON%" %BYTES_RECEIVED% %BYTES_SENT% %DURATION% %RESP(X-ENVOY-UPSTREAM-SERVICE-TIME)% "%REQ(X-FORWARDED-FOR)%" "%REQ(USER-AGENT)%" "%REQ(X-REQUEST-ID)%" "%REQ(:AUTHORITY)%" "%UPSTREAM_HOST%" %UPSTREAM_CLUSTER% %UPSTREAM_LOCAL_ADDRESS% %DOWNSTREAM_LOCAL_ADDRESS% %DOWNSTREAM_REMOTE_ADDRESS% %REQUESTED_SERVER_NAME% %ROUTE_NAME%n"
}
}
]
}
}
],"name": "virtualOutbound-catchall-tcp"
}
],"hidden_envoy_deprecated_use_original_dst": true,"traffic_direction": "OUTBOUND"
},"last_updated": "2020-09-15T08:06:24.066Z"
}
},
上面envoy.tcp_proxy过滤器的cluster为PassthroughCluster，这是因为将global.outboundTrafficPolicy.mode设置为了ALLOW_ANY，默认可以访问外部服务。如果global.outboundTrafficPolicy.mode设置为了REGISTRY_ONLY，则此处将变为cluster BlackHoleCluster，默认丢弃所有到外部服务的请求。
上面使用wasm(WebAssembly)来记录遥测信息，Envoy官方文档中目前缺少对wasm的描述，可以参考开源代码的描述。从runtime字段为null可以看到并没有启用。可以在安装istio的时候使用如下参数来启用基于Wasm的遥测。
$ istioctl install --set values.telemetry.v2.metadataExchange.wasmEnabled=true --set values.telemetry.v2.prometheus.wasmEnabled=true
启用之后，与wasm有关的用于遥测的过滤器配置变为了如下内容，可以看到其runtime使用了envoy.wasm.runtime.v8。更多参见官方博客。
{
"name": "istio.stats","typed_config": {
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct","value": {
"config": {
"root_id": "stats_outbound","vm_config": { /* wasm虚拟机配置 */
"vm_id": "tcp_stats_outbound","runtime": "envoy.wasm.runtime.v8",/* 使用的wasm runtime */
"code": {
"local": {
"filename": "/etc/istio/extensions/stats-filter.compiled.wasm" /* 编译后的wasm插件路径 */
}
},"allow_precompiled": true
},"configuration": {
"@type": "type.googleapis.com/google.protobuf.StringValue",n "stat_prefix": "istio"n}n"
}
}
}
}
},
在istio-proxy容器的/etc/istio/extensions/目录下可以看到wasm编译的相关程序，包含用于交换Node Metadata的metadata-exchange-filter.wasm和用于遥测的stats-filter.wasm，带compiled的wasm用于HTTP。
$ ls
metadata-exchange-filter.compiled.wasm metadata-exchange-filter.wasm stats-filter.compiled.wasm stats-filter.wasm
Istio的filter处理示意图如下：
-
VirtualInbound/Inbound Listener：与virtualOutbound listener类似，通过如下规则将所有入站的TCP流量重定向到15006端口
-A ISTIO_IN_REDIRECT -p tcp -j REDIRECT --to-ports 15006
下面是一个demo环境中的典型配置，可以看到对于每个监听的地址，都配置了两个过滤器：一个带transport_socket，一个不带transport_socket，分别处理使用TLS的连接和不使用TLS的连接。主要的入站监听器为：
- 处理基于IPv4的带TLS 的TCP连接
- 处理基于IPv4的不带TLS 的TCP连接
- 处理基于IPv6的带TLS 的TCP连接
- 处理基于IPv6的不带TLS 的TCP连接
- 处理基于IPv4的带TLS 的HTTP连接
- 处理基于IPv4的不带TLS 的HTTP连接
- 处理基于IPv6的带TLS 的HTTP连接
- 处理基于IPv6的不带TLS 的HTTP连接
- 处理业务的带TLS(不带TLS)的连接
下面给出如下内容的inbound listener：
- 处理基于IPv4的带TLS 的TCP连接
- 处理基于IPv4的不带TLS 的TCP连接
- 处理业务的带TLS的连接
{
"name": "virtualInbound","name": "virtualInbound","address": { /* 该listener绑定的地址和端口 */
"socket_address": {
"address": "0.0.0.0","port_value": 15006
}
},"filter_chains": [
/* 匹配所有IPV4地址，使用TLS且ALPN为istio-peer-exchange或istio的连接 */
{
"filter_chain_match": { /* 将连接匹配到该过滤器链时使用的标准 */
"prefix_ranges": [ /* 当listener绑定到0.0.0.0/::时匹配的IP地址和前缀长度，下面表示整个网络地址 */
{
"address_prefix": "0.0.0.0","prefix_len": 0
}
],"transport_protocol": "tls",/* 匹配的传输协议 */
"application_protocols": [ /* 使用的ALPN */
"istio-peer-exchange","istio"
]
},"filters": [
{
"name": "istio.metadata_exchange",/* 交换Node Metadata的配置 */
"typed_config": {
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct","value": {
"protocol": "istio-peer-exchange"
}
}
},{
"name": "istio.stats",/* 使用wasm进行遥测的配置 */
"typed_config": {
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct","value": {
"config": {
"root_id": "stats_inbound","vm_config": {
"vm_id": "tcp_stats_inbound","runtime": "envoy.wasm.runtime.null","code": {
"local": {
"inline_string": "envoy.wasm.stats"
}
}
},/* 配置连接上游cluster InboundPassthroughClusterIpv4时的访问日志，InboundPassthroughClusterIpv4 cluster用于处理基于IPv4的HTTP */
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.network.tcp_proxy.v3.TcpProxy","stat_prefix": "InboundPassthroughClusterIpv4","cluster": "InboundPassthroughClusterIpv4","access_log": [
{
"name": "envoy.file_access_log","typed_config": {
"@type": "type.googleapis.com/envoy.extensions.access_loggers.file.v3.FileAccessLog","transport_socket": { /* 匹配TLS的传输socket */
"name": "envoy.transport_sockets.tls","typed_config": {
"@type": "type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.DownstreamTlsContext","common_tls_context": {
"alpn_protocols": [ /* 监听器使用的ALPN列表 */
"istio-peer-exchange","h2","http/1.1"
],"tls_certificate_sds_secret_configs": [ /* 通过SDS API获取证书的配置 */
{
"name": "default","sds_config": {
"api_config_source": {
"api_type": "GRPC","grpc_services": [
{
"envoy_grpc": {
"cluster_name": "sds-grpc"
}
}
],"transport_api_version": "V3"
},"resource_api_version": "V3"
}
}
],"combined_validation_context": {
"default_validation_context": { /* 对对端的证书的SAN进行认证 */
"match_subject_alt_names": [
{
"prefix": "spiffe://new-td/"
},{
"prefix": "spiffe://old-td/"
}
]
},"validation_context_sds_secret_config": { /* 配置通过SDS API获取证书 */
"name": "ROOTCA","resource_api_version": "V3"
}
}
}
},"require_client_certificate": true
}
},"name": "virtualInbound"
},/* 与上面不同的是，此处匹配不带TLS的连接 */
{
"filter_chain_match": {
"prefix_ranges": [
{
"address_prefix": "0.0.0.0","prefix_len": 0
}
]
},...
},...
}
],...
/* 应用的监听器，监听端口为HTTP 80端口 */
{
"filter_chain_match": {
"destination_port": 80,/* 匹配的请求的目的端口 */
"application_protocols": [ /* 匹配的ALPN，仅在使用TLS时使用 */
"istio","istio-http/1.0","istio-http/1.1","istio-h2"
]
},/* 交换Node Metadata的配置 */
...
},{
"name": "envoy.http_connection_manager",/* HTTP连接管理过滤器 */
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager","stat_prefix": "inbound_0.0.0.0_80","route_config": { /* 静态路由表 */
"name": "inbound|80|http|sleep.default.svc.cluster.local",/* 路由配置的名称 */
"virtual_hosts": [ /* 构成路由表的虚拟主机列表 */
{
"name": "inbound|http|80",/* 构成路由表的虚拟主机名 */
"domains": [ /* 匹配到该虚拟主机的域列表 */
"*"
],"routes": [ /* 对入站请求的路由，将路径为"/"的HTTP请求路由到cluster inbound|80|http|sleep.default.svc.cluster.local*/
{
"match": {
"prefix": "/"
},"route": {
"cluster": "inbound|80|http|sleep.default.svc.cluster.local","max_grpc_timeout": "0s"
},"decorator": {
"operation": "sleep.default.svc.cluster.local:80/*"
},"name": "default" /* 路由的名称 */
}
]
}
],"validate_clusters": false
},"http_filters": [ /* HTTP连接过滤器链 */
{
"name": "istio.metadata_exchange",/* 基于HTTP的Metadata的交换配置 */
...
},{
"name": "istio_authn",/* istio的mTLS的默认值 */
"typed_config": {
"@type": "type.googleapis.com/istio.envoy.config.filter.http.authn.v2alpha1.FilterConfig","policy": {
"peers": [
{
"mtls": {
"mode": "PERMISSIVE"
}
}
]
},"skip_validate_trust_domain": true
}
},{
"name": "envoy.filters.http.cors","typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.http.cors.v3.Cors"
}
},{
"name": "envoy.fault","typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.http.fault.v3.HTTPFault"
}
},{
"name": "istio.stats",/* 基于HTTP的遥测配置 */
...
},{
"name": "envoy.router","typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.http.router.v3.Router"
}
}
],"tracing": {
"client_sampling": {
"value": 100
},"random_sampling": {
"value": 1
},"overall_sampling": {
"value": 100
}
},"server_name": "istio-envoy",/* 设置访问日志格式 */
"access_log": [
{
"name": "envoy.file_access_log",...
}
],"use_remote_address": false,"generate_request_id": true,"forward_client_cert_details": "APPEND_FORWARD","set_current_client_cert_details": {
"subject": true,"dns": true,"uri": true
},"upgrade_configs": [
{
"upgrade_type": "websocket"
}
],"stream_idle_timeout": "0s","normalize_path": true
}
}
],"transport_socket": { /* TLS传输socket配置 */
"name": "envoy.transport_sockets.tls",...
},"name": "0.0.0.0_80"
},
-
Outbound listener: 下面是到Prometheus服务9092端口的outbound listener。10.84.30.227为Prometheus的k8s service地址，指定了后端的cluster outbound|9092||prometheus-k8s.openshift-monitoring.svc.cluster.local。route_config_name字段指定了该listener使用的route prometheus-k8s.openshift-monitoring.svc.cluster.local:9092。
{
"name": "10.84.30.227_9092","name": "10.84.30.227_9092","address": {
"socket_address": {
"address": "10.84.30.227","port_value": 9092
}
},"filter_chains": [
{
"filters": [
{
"name": "istio.stats",...
}
},/* TCP过滤器设置，设置连接到对应cluster的日志格式 */
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.network.tcp_proxy.v3.TcpProxy","stat_prefix": "outbound|9092||prometheus-k8s.openshift-monitoring.svc.cluster.local","cluster": "outbound|9092||prometheus-k8s.openshift-monitoring.svc.cluster.local","access_log": [
...
]
}
}
]
},{
"filter_chain_match": {
"application_protocols": [
"http/1.0","http/1.1","h2c"
]
},"filters": [
{
"name": "envoy.http_connection_manager",/* 配置HTTP连接 */
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager","stat_prefix": "outbound_10.84.30.227_9092","rds": { /* RDS接口配置 */
"config_source": {
"ads": {},"resource_api_version": "V3"
},"route_config_name": "prometheus-k8s.openshift-monitoring.svc.cluster.local:9092" /* 指定路由配置 */
},"http_filters": [
{
"name": "istio.metadata_exchange","typed_config": {
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct","type_url": "type.googleapis.com/envoy.extensions.filters.http.wasm.v3.Wasm",...
}
},{
"name": "istio.alpn","typed_config": {
"@type": "type.googleapis.com/istio.envoy.config.filter.http.alpn.v2alpha1.FilterConfig","alpn_override": [
{
"alpn_override": [
"istio-http/1.0","istio"
]
},{
"upstream_protocol": "HTTP11","alpn_override": [
"istio-http/1.1",{
"upstream_protocol": "HTTP2","alpn_override": [
"istio-h2","istio"
]
}
]
}
},"tracing": {
...
},...
}
}
],"normalize_path": true
}
}
]
}
],"deprecated_v1": {
"bind_to_port": false
},"listener_filters": [
{
"name": "envoy.listener.tls_inspector","typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.listener.tls_inspector.v3.TlsInspector"
}
},{
"name": "envoy.listener.http_inspector","typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.listener.http_inspector.v3.HttpInspector"
}
}
],"listener_filters_timeout": "5s","traffic_direction": "OUTBOUND","continue_on_listener_filters_timeout": true
},"last_updated": "2020-09-15T08:06:23.989Z"
}
},
从上面的配置可以看出，路由配置位于HttpConnectionManager类型中，因此如果某个listener没有用到HTTP，则不会有对应的route。如下面的istiod15012端口上的服务，提供了基于gRPC协议的XDP和CA的服务(使用TLS)。
{
"name": "10.84.251.157_15012","active_state": {
"version_info": "2020-09-16T07:48:42Z/22","listener": {
"@type": "type.googleapis.com/envoy.config.listener.v3.Listener","name": "10.84.251.157_15012","address": {
"socket_address": {
"address": "10.84.251.157","port_value": 15012
}
},"filter_chains": [
{
"filters": [
{
"name": "istio.stats",...
},{
"name": "envoy.tcp_proxy","typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.network.tcp_proxy.v3.TcpProxy","stat_prefix": "outbound|15012||istiod.istio-system.svc.cluster.local","cluster": "outbound|15012||istiod.istio-system.svc.cluster.local","access_log": [
...
]
}
}
]
}
],"deprecated_v1": {
"bind_to_port": false
},"traffic_direction": "OUTBOUND"
},"last_updated": "2020-09-16T07:49:34.134Z"
}
},
-
Route：Istio的route也分为静态配置和动态配置。静态路由配置与静态监听器，以及inbound 动态监听器中设置的静态路由配置(envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager中的route_config)有关。
下面看一个与Prometheus 9092端口提供的服务有关的动态路由，路由配置名称route_config.name与上面Prometheus outbound监听器route_config_name字段指定的值是相同的。
{
"version_info": "2020-09-16T07:48:42Z/22","route_config": {
"@type": "type.googleapis.com/envoy.config.route.v3.RouteConfiguration","name": "prometheus-k8s.openshift-monitoring.svc.cluster.local:9092","virtual_hosts": [
{
"name": "prometheus-k8s.openshift-monitoring.svc.cluster.local:9092","domains": [
"prometheus-k8s.openshift-monitoring.svc.cluster.local","prometheus-k8s.openshift-monitoring.svc.cluster.local:9092","prometheus-k8s.openshift-monitoring","prometheus-k8s.openshift-monitoring:9092","prometheus-k8s.openshift-monitoring.svc.cluster","prometheus-k8s.openshift-monitoring.svc.cluster:9092","prometheus-k8s.openshift-monitoring.svc","prometheus-k8s.openshift-monitoring.svc:9092","10.84.30.227","10.84.30.227:9092"
],"routes": [
{
"match": {
"prefix": "/"
},"route": { /* 路由到的后端cluster */
"cluster": "outbound|9092||prometheus-k8s.openshift-monitoring.svc.cluster.local","retry_policy": {
"retry_on": "connect-failure,refused-stream,unavailable,cancelled,retriable-status-codes","num_retries": 2,"retry_host_predicate": [
{
"name": "envoy.retry_host_predicates.previous_hosts"
}
],"host_selection_retry_max_attempts": "5","retriable_status_codes": [
503
]
},"max_grpc_timeout": "0s"
},"decorator": {
"operation": "prometheus-k8s.openshift-monitoring.svc.cluster.local:9092/*"
},"name": "default"
}
],"include_request_attempt_count": true
}
],"validate_clusters": false
},"last_updated": "2020-09-16T07:49:52.551Z"
},
整个访问流程简单可以视为：
-
Inbound请求：
+----------+ +-----------------------+ +-----------------+ +----------+
| iptables +--->+ virtualInbound:15006 +--->+ Inbound Cluster +--->+ endpoint |
+----------+ +-----------------------+ +-----------------+ +----------+
-
出站请求：
+----------+ +-----------------------+ +-------------------+
| iptables +--->+ virtualOutbound：105001+--->+ Outbound Listener +---+
+----------+ +-----------------------+ +-------------------+ |
|
|
+--------------------------------------------------------------+
|
| +-------+ +-----------------+ +----------+
+---->+ route +--->+Outbound Cluster +--->+ endpoint |
+-------+ +-----------------+ +----------+
更多内容可以参考Envoy的官方文档
下面是基于Istio官方BookInfo的一个访问流程图，可以帮助理解整个流程。
SDS
下图来自这篇文章
SDS会动态下发两个证书：default和ROOTCA。前者表示本服务使用的证书，证书中的SAN使用了该服务对应的命名空间下的serviceaccount；后者为集群的CA，通过将configmap istio-ca-root-cert挂载到服务的pod中，它与istio-system命名空间中的secret istio-ca-secret相同，可以用于认证各个服务的证书(default)。因此不同的服务使用的default证书是不同的，但使用的ROOTCA证书是相同的。
{
"@type": "type.googleapis.com/envoy.admin.v3.SecretsConfigDump","dynamic_active_secrets": [
{
"name": "default","version_info": "09-21 20:10:52.178","last_updated": "2020-09-21T20:10:52.446Z","secret": {
"@type": "type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.Secret","name": "default",/* 服务使用的证书 */
"tls_certificate": {
"certificate_chain": {
"inline_bytes": "LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JS..."
},"private_key": {
"inline_bytes": "W3JlZGFjdGVkXQ=="
}
}
}
},{
"name": "ROOTCA","version_info": "2020-09-15 08:05:53.174860205 +0000 UTC m=+1.073140142","last_updated": "2020-09-15T08:05:53.275Z","name": "ROOTCA",/* 验证服务证书使用的CA证书 */
"validation_context": {
"trusted_ca": {
"inline_bytes": "LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0t..."
}
}
}
}
]
}
将default证书导出，查看该证书，可以看到其使用的SAN为spiffe://new-td/ns/default/sa/sleep，用到了default命名空间下的serviceaccount sleep，提供了该服务的身份标识。
# openssl x509 -in ca-chain.crt -noout -text
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
37:31:36:d4:25:64:18:10:27:47:75:79:6c:ff:21:3a
Signature Algorithm: sha256WithRSAEncryption
Issuer: O=cluster.local
Validity
Not Before: Sep 21 08:34:33 2020 GMT
Not After : Sep 22 08:34:33 2020 GMT
Subject:
Subject Public Key Info:
...
X509v3 Subject Alternative Name: critical
URI:spiffe://new-td/ns/default/sa/sleep
Signature Algorithm: sha256WithRSAEncryption
...
到处default和ROOTCA证书，分别对应下面的pod.crt和root-cat.crt，可以看到，能够使用ROOTCA来验证default。
# openssl verify -CAfile root-ca.crt pod.crt
ca-chain.crt: OK
在 Istio的sidecar配置中，有两处需要通过 SDS 来配置证书：
-
Inbound Listener：Inbound Listener用于接收来自下游的连接，在DownstreamTlsContext中配置了对下游连接的认证。其指定了用于验证下游连接的ROOTCA证书。match_subject_alt_names中指定的通配SAN是因为在安装Istio时通过参数values.global.trustDomain指定了信任域。
"common_tls_context": {
"alpn_protocols": [
"istio-peer-exchange","tls_certificate_sds_secret_configs": [
{
"name": "default",/* 服务器使用的证书名称，由SDS下发 */
"sds_config": {
"api_config_source": {
"api_type": "GRPC","combined_validation_context": {
"default_validation_context": {
"match_subject_alt_names": [ /* 指定的信任域 */
{
"prefix": "spiffe://new-td/"
},"validation_context_sds_secret_config": {
"name": "ROOTCA",/* 用于认证下游连接的CA证书 */
"sds_config": {
"api_config_source": {
"api_type": "GRPC",
-
Outbound Cluster：outbound cluster(下例为outbound|80||sleep.default.svc.cluster.local)作为下游配置，也需要对服务端的证书进行验证。其UpstreamTlsContext中的配置如下。由于上有服务为sleep.default.svc.cluster.local，因此在match_subject_alt_names字段中指定了验证的服务端的SAN。
"common_tls_context": {
"alpn_protocols": [
"istio-peer-exchange","istio"
],"tls_certificate_sds_secret_configs": [
{
"name": "default","sds_config": {
"api_config_source": {
"api_type": "GRPC","grpc_services": [
{
"envoy_grpc": {
"cluster_name": "sds-grpc"
}
}
],"transport_api_version": "V3"
},"resource_api_version": "V3"
}
}
],"combined_validation_context": {
"default_validation_context": {
"match_subject_alt_names": [ /* 上游服务使用的证书中的SAN */
{
"exact": "spiffe://new-td/ns/default/sa/sleep"
}
]
},"validation_context_sds_secret_config": {
"name": "ROOTCA","resource_api_version": "V3"
}
}
}
},
可以看到，作为服务端，仅需要使用ROOTCA证书对客户端进行证书校验即可(如果没有指定信任域)；作为客户端，需要使用ROOTCA证书对服务端证书进行校验，也需要对服务端使用的证书中的SAN进行校验。
gateway上，如果需要针对服务网格外部的服务进行TLS双向认证，可以参考Traffic Management。
参考
- Sidecar 流量路由机制分析
- WebAssembly在Envoy与Istio中的应用
- Istio1.5 & Envoy 数据面 WASM 实践
- How to write WASM filters for Envoy and deploy it with Istio
- Implementing Filters in Envoy
- 一文带你彻底厘清 Isito 中的证书工作机制
（编辑：李大同）
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