This is xnu-10002.1.13. See this file in:
module DarwinPrivate.net [system] {
  module if {
    header "net/if_private.h"
    export *
  }

  #ifndef XNU_PLATFORM_MacOSX
  module if_media {
    header "net/if_media.h"
    export *
  }

  #endif
  module if_var {
    header "net/if_var_private.h"
    export *
  }

  module if_vlan_var {
    header "net/if_vlan_var.h"
    export *
  }

  module route {
    #ifndef XNU_PLATFORM_MacOSX
    header "net/route.h"
    #endif
    header "net/route_private.h"
    export *
  }
}