WIP: Add FdListenerspec to listen on passed file-descriptor.

granian/_granian.pyi

@@ -144,6 +144,10 @@ if sys.platform != 'win32':
         def __new__(cls, bind: str, backlog: int, permissions: int | None) -> UnixListenerSpec: ...
         def build(self) -> SocketHolder: ...
         def is_uds(self) -> bool: ...
+    class FdListenerSpec:
+        def __new__(cls, fd: int) -> FdListenerSpec: ...
+        def build(self) -> SocketHolder: ...
+        def is_uds(self) -> bool: ...
 
 class CallbackScheduler:
     _loop: Any

granian/cli.py

@@ -127,6 +127,7 @@ def option(*param_decls: str, cls: type[click.Option] | None = None, **attrs: An
     default=Interfaces.RSGI,
     help='Application interface type',
 )
+@option('--fd', type=int, default=None, help='Listen on socket from this file-descriptor.')
 @option('--http', type=EnumType(HTTPModes), default=HTTPModes.auto, help='HTTP version')
 @option('--ws/--no-ws', 'websockets', default=True, help='Enable websockets handling')
 @option('--workers', type=click.IntRange(1), default=1, help='Number of worker processes')
@@ -438,6 +439,7 @@ def cli(
     port: int,
     uds: pathlib.Path | None,
     uds_permissions: int | None,
+    fd: int | None,
     interface: Interfaces,
     http: HTTPModes,
     websockets: bool,
@@ -524,6 +526,7 @@ def cli(
         port=port,
         uds=uds,
         uds_permissions=uds_permissions,
+        fd=fd,
         interface=interface,
         workers=workers,
         blocking_threads=blocking_threads,

granian/net.py

@@ -8,8 +8,10 @@
 copyreg.pickle(SocketSpec, lambda v: (SocketSpec, v.__getstate__()))
 
 if sys.platform != 'win32':
-    from ._granian import UnixListenerSpec as UnixSocketSpec
+    from ._granian import UnixListenerSpec as UnixSocketSpec, FdListenerSpec as FdSocketSpec
 
     copyreg.pickle(UnixSocketSpec, lambda v: (UnixSocketSpec, v.__getstate__()))
+    copyreg.pickle(FdSocketSpec, lambda v: (FdSocketSpec, v.__getstate__()))
 else:
     UnixSocketSpec = None
+    FdSocketSpec = None

granian/server/common.py

@@ -21,7 +21,7 @@
 from ..errors import ConfigurationError, PidFileError
 from ..http import HTTP1Settings, HTTP2Settings
 from ..log import DEFAULT_ACCESSLOG_FMT, LogLevels, configure_logging, logger
-from ..net import SocketSpec, UnixSocketSpec
+from ..net import SocketSpec, UnixSocketSpec, FdSocketSpec
 
 
 WT = TypeVar('WT')
@@ -87,6 +87,7 @@ def __init__(
         port: int = 8000,
         uds: Path | None = None,
         uds_permissions: int | None = None,
+        fd: int | None = None,
         interface: Interfaces = Interfaces.RSGI,
         workers: int = 1,
         blocking_threads: int | None = None,
@@ -149,6 +150,7 @@ def __init__(
         self.bind_port = port
         self.bind_uds = uds.resolve() if uds else None
         self.uds_permissions = uds_permissions
+        self.bind_fd = fd
         self.interface = interface
         self.workers = max(1, workers)
         self.runtime_threads = max(1, runtime_threads)
@@ -291,7 +293,12 @@ def build_ssl_context(
 
     @property
     def _bind_addr_fmt(self):
-        return f'unix:{self.bind_uds}' if self.bind_uds else f'{self.bind_addr}:{self.bind_port}'
+        if self.bind_fd is not None:
+            return f'fd:{self.bind_fd}'
+        elif self.bind_uds :
+            return f'unix:{self.bind_uds}'
+        else:
+            f'{self.bind_addr}:{self.bind_port}'
 
     @staticmethod
     def _call_hooks(hooks):
@@ -311,7 +318,9 @@ def on_shutdown(self, hook: Callable[[], Any]) -> Callable[[], Any]:
         return hook
 
     def _init_shared_socket(self):
-        if self.bind_uds:
+        if self.bind_fd:
+            self._ssp = FdSocketSpec(self.bind_fd)
+        elif self.bind_uds:
             self._ssp = UnixSocketSpec(str(self.bind_uds), self.backlog, self.uds_permissions)
         else:
             self._ssp = SocketSpec(self.bind_addr, self.bind_port, self.backlog)

src/net.rs

@@ -67,6 +67,15 @@ pub struct UnixListenerSpec {
     permissions: Option<u32>,
 }
 
+
+#[cfg(unix)]
+#[pyclass(frozen, module = "granian._granian")]
+#[derive(Clone)]
+pub struct FdListenerSpec {
+    inp: (i32,),
+    fd: i32,
+}
+
 impl ListenerSpec {
     pub(crate) fn as_socket(&self) -> Result<Socket> {
         let socket = Socket::new(self.domain, Type::STREAM, Some(Protocol::TCP))?;
@@ -161,6 +170,35 @@ impl UnixListenerSpec {
     }
 }
 
+
+#[cfg(unix)]
+impl FdListenerSpec {
+    pub(crate) fn as_socket(&self) -> Result<Socket> {
+        let socket = unsafe { Socket::from_raw_fd(self.fd) };
+        Ok(socket)
+    }
+}
+
+#[cfg(unix)]
+#[pymethods]
+impl FdListenerSpec {
+    #[new]
+    fn new(fd: i32) -> PyResult<Self> {
+        Ok(Self {
+            inp: (fd,),
+            fd,
+        })
+    }
+
+    fn build(&self) -> Result<SocketHolder> {
+        SocketHolder::from_fd_spec(self)
+    }
+
+    pub fn __getstate__(&self, py: Python) -> Py<PyAny> {
+        self.inp.clone().into_py_any(py).unwrap()
+    }
+}
+
 #[cfg(not(any(windows, target_os = "linux", target_os = "freebsd")))]
 #[pyclass(frozen, module = "granian._granian")]
 pub struct SocketHolder {
@@ -186,6 +224,15 @@ impl SocketHolder {
         })
     }
 
+    fn from_fd_spec(spec: &FdListenerSpec) -> Result<Self> {
+        let socket = spec.as_socket()?;
+        let domain = socket.domain().unwrap();
+        Ok(Self {
+            socket: Some(socket),
+            uds: domain == Domain::UNIX,
+        })
+    }
+
     #[allow(clippy::unnecessary_wraps)]
     pub fn as_tcp_listener(&self) -> Result<TcpListener> {
         let listener = unsafe { TcpListener::from_raw_fd(self.socket.as_ref().unwrap().as_raw_fd()) };
@@ -260,6 +307,16 @@ impl SocketHolder {
         })
     }
 
+    fn from_fd_spec(spec: &FdListenerSpec) -> Result<Self> {
+        let socket = spec.as_socket()?;
+        let domain = socket.domain().unwrap();
+        Ok(Self {
+            socket: Some(socket),
+            uds: domain == Domain::UNIX,
+            backlog: 20,
+        })
+    }
+
     pub fn as_tcp_listener(&self) -> Result<TcpListener> {
         let socket = self.socket.as_ref().unwrap();
         socket.listen(self.backlog)?;
@@ -355,6 +412,7 @@ pub(crate) fn init_pymodule(module: &Bound<PyModule>) -> PyResult<()> {
     module.add_class::<SocketHolder>()?;
     #[cfg(unix)]
     module.add_class::<UnixListenerSpec>()?;
+    module.add_class::<FdListenerSpec>()?;
 
     Ok(())
 }