Update proxy config docs and add test for ipv6

agent/agent_test.go

@@ -2676,6 +2676,20 @@ func TestAgent_AddProxy(t *testing.T) {
 			wantTCPCheck: "127.10.10.10:1234",
 			wantErr:      false,
 		},
+		{
+			desc: "managed proxy with overridden but unspecified ipv6 bind address",
+			proxy: &structs.ConnectManagedProxy{
+				ExecMode: structs.ProxyExecModeDaemon,
+				Command:  []string{"consul", "connect", "proxy"},
+				Config: map[string]interface{}{
+					"foo":          "bar",
+					"bind_address": "[::]",
+				},
+				TargetServiceID: "web",
+			},
+			wantTCPCheck: "127.0.0.1:20000",
+			wantErr:      false,
+		},
 		{
 			desc: "managed proxy with overridden check address",
 			proxy: &structs.ConnectManagedProxy{

website/source/docs/connect/configuration.html.md

@@ -62,6 +62,8 @@ described here, the rest of the service definition is shown for context and is
         "config": {
           "bind_address": "0.0.0.0",
           "bind_port": 20000,
+          "tcp_check_address": "192.168.0.1",
+          "disable_tcp_check": false,
           "local_service_address": "127.0.0.1:1234",
           "local_connect_timeout_ms": 1000,
           "handshake_timeout_ms": 10000,
@@ -84,6 +86,8 @@ described here, the rest of the service definition is shown for context and is
 
 #### Configuration Key Reference
 
+All fields are optional with a sane default.
+
 * <a name="bind_address"></a><a href="#bind_address">`bind_address`</a> -
   The address the proxy will bind it's _public_ mTLS listener to. It
   defaults to the same address the agent binds to.
@@ -94,6 +98,22 @@ described here, the rest of the service definition is shown for context and is
   range](/docs/agent/options.html#proxy_min_port) if available. By default the
   range is [20000, 20255] and the port is selected at random from that range.
 
+* <a name="tcp_check_address"></a><a
+  href="#tcp_check_address">`tcp_check_address`</a> - The address the agent will
+  run a [TCP health check](/docs/agent/checks.html) against. By default this is
+  the same as the proxy's [bind address](#bind_address) except if the
+  bind_address is `0.0.0.0` or `[::]` in which case this defaults to `127.0.0.1`
+  and assumes agent can dial proxy over loopback. For more complex
+  configurations where agent and proxy communicate over a bridge for example,
+  this configuration can be used to specify a different _address_ (but not port)
+  for the agent to use for health checks if it can't talk to the proxy over
+  localhost or it's publicly advertised port. The check always uses the same
+  port that the proxy is bound to.
+
+* <a name="disable_tcp_check"></a><a
+  href="#disable_tcp_check">`disable_tcp_check`</a> - If true, this disables a
+  TCP check being setup for the proxy. Default is false.
+
 * <a name="local_service_address"></a><a href="#local_service_address">`local_service_address`</a> - The
   `[address]:port` that the proxy should use to connect to the local application
   instance. By default it assumes `127.0.0.1` as the address and takes the port