hcm: allow unix sockets to be considered internal addresses (#4470)

* hcm: allow unix sockets to be considered internal addresses

Adds a config option that treats unix socket addresses as internal for
the purpose of stats/header santization.

Signed-off-by: Snow Pettersen <snowp@squareup.com>

Mirrored from https://github.com/envoyproxy/envoy @ abf17919e363a1c9a2ce6dec85cda8cd6ba725dc

envoy/config/filter/network/http_connection_manager/v2/http_connection_manager.proto

@@ -195,6 +195,17 @@ message HttpConnectionManager {
   // :ref:`config_http_conn_man_headers_x-forwarded-for` for more information.
   uint32 xff_num_trusted_hops = 19;
 
+  message InternalAddressConfig {
+    // Whether unix socket addresses should be considered internal.
+    bool unix_sockets = 1;
+  }
+
+  // Configures what network addresses are considered internal for stats and header sanitazion
+  // purposes. If unspecified, only RFC1918 IP addresses will be considered internal.
+  // See the documentation for :ref:`config_http_conn_man_headers_x-envoy-internal` for more
+  // information about internal/external addresses.
+  InternalAddressConfig internal_address_config = 25;
+
   // If set, Envoy will not append the remote address to the
   // :ref:`config_http_conn_man_headers_x-forwarded-for` HTTP header. This may be used in
   // conjunction with HTTP filters that explicitly manipulate XFF after the HTTP connection manager