ioctl: Forward standard termios calls to real pty

meson.build

@@ -162,6 +162,8 @@ umockdev_lib = shared_library('umockdev',
    'src/uevent_sender.c',
    'src/ioctl_tree.vapi',
    'src/ioctl_tree.c',
+   'src/ioctl_termios.vapi',
+   'src/ioctl_termios.c',
    'src/utils.c',
    'src/debug.c'],
   vala_vapi: 'umockdev-1.0.vapi',
@@ -224,6 +226,8 @@ umockdev_record_exe = executable('umockdev-record',
    'src/umockdev-spi.vala',
    'src/ioctl_tree.vapi',
    'src/ioctl_tree.c',
+   'src/ioctl_termios.vapi',
+   'src/ioctl_termios.c',
    'src/utils.c',
    'src/debug.c'],
   dependencies: [glib, gobject, gio_unix, vapi_posix, vapi_config, vapi_ioctl, vapi_selinux, libpcap, selinux],
@@ -282,7 +286,9 @@ if gudev.found()
   depends: [preload_lib])
 
   test('umockdev-vala', executable('test-umockdev-vala',
-      'tests/test-umockdev-vala.vala',
+      ['tests/test-umockdev-vala.vala',
+       'src/ioctl_termios.vapi',
+       'src/ioctl_termios.c'],
       include_directories: include_directories('src'),
       dependencies: [glib, gobject, gio, gudev, vapi_posix, vapi_assertions, vapi_ioctl, vapi_glibc, vapi_selinux, selinux],
       link_with: [umockdev_lib, umockdev_utils_lib],

src/ioctl_termios.c

@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * ioctl_termios.c - Helper functions for termios ioctl handling
+ *
+ * We can't use the Linux.Termios.TCGETS2 constants here: It is defined in sys/ioctl.h using _IOR(struct termios2),
+ * and Vala tries to apply sizeof() to the incomplete termios2 struct. Also, the TC*2 variants are not available
+ * on ppc64le, and Vala does not have conditional compilation.
+ */
+
+#include "ioctl_termios.h"
+#include <sys/ioctl.h>
+#include <asm/termbits.h>
+#include <asm/ioctls.h>
+
+bool is_termios_ioctl(unsigned long request)
+{
+    switch (request) {
+        case TCGETS:
+        case TCSETS:
+        case TCSETSW:
+        case TCSETSF:
+        case TCGETA:
+        case TCSETA:
+        case TCSETAW:
+        case TCSETAF:
+        case TIOCGWINSZ:
+        case TIOCSWINSZ:
+#ifdef TCGETS2
+        case TCGETS2:
+        case TCSETS2:
+        case TCSETSW2:
+        case TCSETSF2:
+#endif
+            return true;
+        default:
+            return false;
+    }
+}
+
+unsigned long get_tcgets_ioctl(void)
+{
+    return TCGETS;
+}

src/ioctl_termios.h

@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * ioctl_termios.h - Helper functions for termios ioctl handling
+ */
+
+#pragma once
+
+#include <stdbool.h>
+
+bool is_termios_ioctl(unsigned long request);
+unsigned long get_tcgets_ioctl(void);

src/ioctl_termios.vapi

@@ -0,0 +1,8 @@
+[CCode (cprefix = "", lower_case_cprefix = "", cheader_filename = "ioctl_termios.h")]
+namespace IoctlTermios {
+    [CCode (cname = "is_termios_ioctl")]
+    public bool is_termios_ioctl(ulong request);
+
+    [CCode (cname = "get_tcgets_ioctl")]
+    public ulong get_tcgets_ioctl();
+}

src/libumockdev-preload.c

@@ -760,7 +760,9 @@ remote_emulate(int fd, int cmd, long arg1, long arg2)
 
 	switch (req.cmd) {
 	    case IOCTL_RES_DONE:
-		errno = req.arg2;
+		/* Only set errno on failure (POSIX behavior) */
+		if (req.arg1 == (unsigned long)-1)
+		    errno = req.arg2;
 
 		pthread_mutex_unlock (&fdinfo->sock_lock);
 		pthread_sigmask(SIG_SETMASK, &sig_restore, NULL);

src/umockdev-ioctl.vala

@@ -1,5 +1,4 @@
 
-
 namespace UMockdev {
 
 /**
@@ -30,7 +29,6 @@ internal bool signal_accumulator_true_handled(GLib.SignalInvocationHint ihint,
     return continue_emission;
 }
 
-
 /**
  * UMockdevIoctlData:
  *
@@ -568,6 +566,9 @@ public class IoctlClient : GLib.Object {
         }
 
         if (!handled && args[0] == 1) {
+            /* No specific handler for this ioctl. First try stateless ioctls
+             * (like USB ioctls), then fall back to executing on the real fd
+             * for terminal ioctls on PTY-backed devices. */
             IoctlTree.Tree tree = null;
             IoctlData? data = null;
             ulong size = IoctlTree.data_size_by_id(_request);
@@ -585,16 +586,30 @@ public class IoctlClient : GLib.Object {
                 return;
             }
 
+            /* Set default errno for tree.execute if it doesn't set one itself */
             if ((char) type == 'E') {
                 Posix.errno = Posix.ENOENT;
             } else {
                 Posix.errno = Posix.ENOTTY;
             }
+
+            /* Try handling with ioctl tree (stateless ioctls like USB) */
             tree.execute(null, _request, *(void**) _arg.data, out ret);
-            my_errno = Posix.errno;
-            Posix.errno = 0;
+            my_errno = Posix.errno;  /* Capture errno (may be set by tree.execute) */
 
-            if (ret != -1) {
+            if (ret == -1) {
+                /* tree.execute failed - check if we should forward to real PTY for termios */
+                if (my_errno == Posix.ENOTTY && IoctlTermios.is_termios_ioctl(_request)) {
+                    try {
+                        ret = execute(out my_errno);
+                        /* execute() returns errno from real ioctl on failure,
+                         * or preserved errno on success (POSIX behavior) */
+                    } catch (IOError e) {
+                        /* execute() threw exception - keep ENOTTY */
+                    }
+                }
+            } else {
+                /* tree.execute succeeded - errno not used (preload doesn't set it on success) */
                 my_errno = 0;
             }