Update docs and add tcp_keepalive_probes setting

.changelog/14800.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+connect: Added gateway options to Envoy proxy config for enabling tcp keepalives on upstream connections to mesh gateways in remote datacenters.
+```

agent/xds/clusters.go

@@ -1545,6 +1545,9 @@ func (s *ResourceGenerator) makeGatewayCluster(snap *proxycfg.ConfigSnapshot, op
 		if cfg.TcpKeepaliveInterval != 0 {
 			cluster.UpstreamConnectionOptions.TcpKeepalive.KeepaliveInterval = makeUint32Value(cfg.TcpKeepaliveInterval)
 		}
+		if cfg.TcpKeepaliveProbes != 0 {
+			cluster.UpstreamConnectionOptions.TcpKeepalive.KeepaliveProbes = makeUint32Value(cfg.TcpKeepaliveProbes)
+		}
 	}
 
 	// If none of the service instances are addressed by a hostname we provide the endpoint IP addresses via EDS

agent/xds/clusters_test.go

@@ -419,6 +419,7 @@ func TestClustersFromSnapshot(t *testing.T) {
 					ns.Proxy.Config["envoy_mesh_gateway_tcp_enable_keepalive"] = true
 					ns.Proxy.Config["envoy_mesh_gateway_tcp_keepalive_time"] = 120
 					ns.Proxy.Config["envoy_mesh_gateway_tcp_keepalive_interval"] = 60
+					ns.Proxy.Config["envoy_mesh_gateway_tcp_keepalive_probes"] = 7
 				}, nil)
 			},
 		},

agent/xds/config.go

@@ -138,6 +138,7 @@ type GatewayConfig struct {
 	TcpKeepaliveEnable   bool `mapstructure:"envoy_mesh_gateway_tcp_enable_keepalive"`
 	TcpKeepaliveTime     int  `mapstructure:"envoy_mesh_gateway_tcp_keepalive_time"`
 	TcpKeepaliveInterval int  `mapstructure:"envoy_mesh_gateway_tcp_keepalive_interval"`
+	TcpKeepaliveProbes   int  `mapstructure:"envoy_mesh_gateway_tcp_keepalive_probes"`
 }
 
 // ParseGatewayConfig returns the GatewayConfig parsed from an opaque map. If an

agent/xds/testdata/clusters/mesh-gateway-tcp-keepalives.latest.golden

@@ -36,6 +36,7 @@
       },
       "upstreamConnectionOptions": {
         "tcpKeepalive": {
+          "keepaliveProbes": 7,
           "keepaliveTime": 120,
           "keepaliveInterval": 60
         }
@@ -74,6 +75,7 @@
       },
       "upstreamConnectionOptions": {
         "tcpKeepalive": {
+          "keepaliveProbes": 7,
           "keepaliveTime": 120,
           "keepaliveInterval": 60
         }
@@ -112,6 +114,7 @@
       },
       "upstreamConnectionOptions": {
         "tcpKeepalive": {
+          "keepaliveProbes": 7,
           "keepaliveTime": 120,
           "keepaliveInterval": 60
         }

website/content/docs/connect/proxies/envoy.mdx

@@ -441,6 +441,25 @@ will continue to be supported.
   addressed by a hostname, such as a managed database. It also applies to mesh gateways,
   such as when gateways in other Consul datacenters are behind a load balancer that is addressed by a hostname.
 
+- `envoy_mesh_gateway_tcp_enable_keepalive` - Enables TCP keepalive settings on mesh gateway upstream connections
+  to remote datacenters. Defaults to `false`. Must be one of `true` or `false`. Details for this feature are available in
+  the [Envoy documentation](https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/core/v3/address.proto#envoy-v3-api-msg-config-core-v3-tcpkeepalive).
+
+- `envoy_mesh_gateway_tcp_keepalive_time` - The number of seconds a connection needs to
+  be idle before keep-alive probes start being sent. For more information, see the
+  [Envoy documentation](https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/core/v3/address.proto#envoy-v3-api-msg-config-core-v3-tcpkeepalive).
+  This option only applies to mesh gateway upstream connections to remote datacenters.
+
+- `envoy_mesh_gateway_tcp_keepalive_interval` - The number of seconds between keep-alive probes.
+  For more information, see the
+  [Envoy documentation](https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/core/v3/address.proto#envoy-v3-api-msg-config-core-v3-tcpkeepalive).
+  This option only applies to mesh gateway upstream connections to remote datacenters.
+
+- `envoy_mesh_gateway_tcp_keepalive_probes` - Maximum number of keepalive probes to send without
+  response before deciding the connection is dead. For more information, see the
+  [Envoy documentation](https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/core/v3/address.proto#envoy-v3-api-msg-config-core-v3-tcpkeepalive).
+  This option only applies to mesh gateway upstream connections to remote datacenters.
+
 ## Advanced Configuration
 
 To support more flexibility when configuring Envoy, several "lower-level" options exist