daemon: distinguish inetd from local stdin sockets

clientserver.c

@@ -1722,9 +1722,30 @@ static void become_daemon(void)
 	}
 }
 
+/* Inetd supplies a connected IP stream on stdin. Other launchers may use a
+ * local socket for process I/O, which must not select inetd mode. */
+static int is_inetd_socket(int fd)
+{
+	int type;
+	struct sockaddr_storage peer = {0};
+	socklen_t type_len = sizeof type;
+	socklen_t peer_len = sizeof peer;
+
+	if (getsockopt(fd, SOL_SOCKET, SO_TYPE, (char *)&type, &type_len) != 0
+	 || type != SOCK_STREAM
+	 || getpeername(fd, (struct sockaddr *)&peer, &peer_len) != 0)
+		return 0;
+
+	return peer.ss_family == AF_INET
+#ifdef INET6
+	    || peer.ss_family == AF_INET6
+#endif
+	    ;
+}
+
 int daemon_main(void)
 {
-	if (is_a_socket(STDIN_FILENO)) {
+	if (is_inetd_socket(STDIN_FILENO)) {
 		int i;
 
 		/* we are running via inetd - close off stdout and

testsuite/daemon-stdin-local-socket_test.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+"""A local stdin socket must not make a standalone daemon enter inetd mode."""
+
+import socket
+
+from rsyncfns import (
+    RSYNC, SCRATCHDIR, claim_free_port, rmtree, start_rsyncd,
+    test_skipped, write_daemon_conf,
+)
+
+if not hasattr(socket, 'AF_UNIX') or not hasattr(socket, 'socketpair'):
+    test_skipped('Unix-domain socket pairs are unavailable')
+
+base = SCRATCHDIR / 'daemon-stdin-local-socket'
+rmtree(base)
+module = base / 'module'
+module.mkdir(parents=True)
+conf = write_daemon_conf([
+    ('module', {'path': str(module), 'read only': 'yes'}),
+])
+port = claim_free_port(12979)
+
+try:
+    parent, child = socket.socketpair(socket.AF_UNIX, socket.SOCK_STREAM)
+except (OSError, ValueError) as e:
+    test_skipped(f'Unix-domain socket pairs are unavailable: {e}')
+try:
+    # ADB shell without a PTY similarly presents a local socket as fd 0. The
+    # local socket must not be mistaken for an inetd connection.
+    start_rsyncd(conf, port, rsync_cmd=RSYNC, stdin=child)
+finally:
+    child.close()
+    parent.close()
+
+print('daemon ignores a local stdin socket when selecting inetd mode')

testsuite/rsyncfns.py

@@ -767,7 +767,8 @@ def _cleanup_rsyncd(proc, port: int) -> 'None':
         _record_port_proc(port, 0, 0)
 
 
-def start_rsyncd(conf_path, port: int, rsync_cmd: str = None) -> 'subprocess.Popen':
+def start_rsyncd(conf_path, port: int, rsync_cmd: str = None,
+                 stdin=subprocess.DEVNULL) -> 'subprocess.Popen':
     """Spawn `rsync --daemon --no-detach --address=127.0.0.1 --port=N
     --config=conf` and return the Popen handle after the port is accepting
     connections.
@@ -784,7 +785,8 @@ def start_rsyncd(conf_path, port: int, rsync_cmd: str = None) -> 'subprocess.Pop
     RSYNC_PEER (the peer side of a two-sided run), so ordinary daemon tests
     get current-client <-> peer-daemon. The reverse-direction test passes
     rsync_cmd=RSYNC to put the current build on the daemon side and drive with
-    the old client.
+    the old client. stdin may override the default /dev/null input when a test
+    needs to exercise daemon launch detection.
 
     This is only ever reached from start_test_daemon() in --use-tcp mode; the
     default (pipe) mode never starts a listening daemon.
@@ -797,7 +799,7 @@ def start_rsyncd(conf_path, port: int, rsync_cmd: str = None) -> 'subprocess.Pop
     ]
     proc = subprocess.Popen(
         argv,
-        stdin=subprocess.DEVNULL,
+        stdin=stdin,
         stdout=subprocess.DEVNULL,
         stderr=subprocess.DEVNULL,
         preexec_fn=_set_pdeathsig,

testsuite/skiplist/cygwin.txt

@@ -28,6 +28,7 @@ daemon-config-symlink
 daemon-module-chdir-symlink
 daemon-module-private-parent
 daemon-secrets-file-symlink
+daemon-stdin-local-socket             # Cygwin Python has no AF_UNIX socketpair
 devices
 dir-sgid
 early-input-symlink

testsuite/stdio_daemon.py

@@ -1,4 +1,4 @@
-"""Launch one rsync daemon session over a local socketpair."""
+"""Launch one rsync daemon session over a loopback TCP connection."""
 
 import socket
 import subprocess
@@ -28,7 +28,19 @@ def _client_for_socket(sock, timeout=10):
 
 def start_stdio_daemon(conf, timeout=10, env=None):
     """Return ``(DaemonClient, Popen)`` for one daemon connection."""
-    parent, child = socket.socketpair()
+    listener = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    parent = None
+    try:
+        listener.bind(('127.0.0.1', 0))
+        listener.listen(1)
+        parent = socket.create_connection(listener.getsockname(), timeout)
+        child, _ = listener.accept()
+    except OSError:
+        if parent is not None:
+            parent.close()
+        raise
+    finally:
+        listener.close()
     try:
         proc = subprocess.Popen(
             rsync_argv('--daemon', '--no-detach', f'--config={conf}'),
@@ -60,4 +72,3 @@ def finish_stdio_daemon(client, proc, timeout=5):
             proc.kill()
             proc.wait(timeout=timeout)
     return proc.stderr.read().decode('utf-8', 'replace') if proc.stderr else ''
-