This is xnu-10002.1.13. See this file in:
module DarwinPrivate.netinet [system] {
  module in {
    header "netinet/in_private.h"
    export *

    exclude header "netinet6/in6_private.h"
  }

  module in_stat {
    header "netinet/in_stat.h"
    export *
  }

  module tcp {
    header "netinet/tcp_private.h"
    export *
  }
}