udev: add new builtin net_driver

Currently the ID_NET_DRIVER is set in net_setup_link builtin.
But this is called pretty late in the udev processing chain.

Right now in some custom rules it was workarounded by calling ethtool
binary directly, which is ugly.

So let's split this code to a separate builtin.

rules.d/50-udev-default.rules.in

@@ -26,6 +26,8 @@ ENV{MODALIAS}!="", IMPORT{builtin}="hwdb --subsystem=$env{SUBSYSTEM}"
 # To keep the backward compatibility, let's set ID_PATH for them.
 SUBSYSTEM=="pci|usb|platform", IMPORT{builtin}="path_id"
 
+SUBSYSTEM=="net", IMPORT{builtin}="net_driver"
+
 ACTION!="add", GOTO="default_end"
 
 SUBSYSTEM=="tty", KERNEL=="ptmx", GROUP="tty", MODE="0666"

src/udev/meson.build

@@ -32,6 +32,7 @@ libudevd_core_sources = files(
         'udev-builtin-hwdb.c',
         'udev-builtin-input_id.c',
         'udev-builtin-keyboard.c',
+        'udev-builtin-net_driver.c',
         'udev-builtin-net_id.c',
         'udev-builtin-net_setup_link.c',
         'udev-builtin-path_id.c',

src/udev/net/link-config.c

@@ -364,7 +364,6 @@ Link *link_free(Link *link) {
 
         sd_device_unref(link->device);
         free(link->kind);
-        free(link->driver);
         strv_free(link->altnames);
         return mfree(link);
 }
@@ -417,8 +416,8 @@ int link_new(LinkConfigContext *ctx, sd_netlink **rtnl, sd_device *device, Link
                         log_link_debug_errno(link, r, "Failed to get permanent hardware address, ignoring: %m");
         }
 
-        r = ethtool_get_driver(&ctx->ethtool_fd, link->ifname, &link->driver);
-        if (r < 0)
+        r = sd_device_get_property_value(link->device, "ID_NET_DRIVER", &link->driver);
+        if (r < 0 && r != -ENOENT)
                 log_link_debug_errno(link, r, "Failed to get driver, ignoring: %m");
 
         *ret = TAKE_PTR(link);

src/udev/net/link-config.h

@@ -34,7 +34,7 @@ typedef struct Link {
         sd_device_action_t action;
 
         char *kind;
-        char *driver;
+        const char *driver;
         uint16_t iftype;
         uint32_t flags;
         struct hw_addr_data hw_addr;

src/udev/udev-builtin-net_driver.c

@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "alloc-util.h"
+#include "device-util.h"
+#include "errno-util.h"
+#include "ethtool-util.h"
+#include "fd-util.h"
+#include "log.h"
+#include "string-util.h"
+#include "udev-builtin.h"
+
+static int builtin_net_driver_set_driver(UdevEvent *event, int argc, char **argv, bool test) {
+        sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
+        _cleanup_close_ int ethtool_fd = -EBADF;
+        _cleanup_free_ char *driver = NULL;
+        const char *sysname;
+        int r;
+
+        r = sd_device_get_sysname(dev, &sysname);
+        if (r < 0)
+                return log_device_warning_errno(dev, r, "Failed to get sysname: %m");
+
+        r = ethtool_get_driver(&ethtool_fd, sysname, &driver);
+        if (ERRNO_IS_NEG_NOT_SUPPORTED(r)) {
+                log_device_debug_errno(dev, r, "Querying driver name via ethtool API is not supported by device '%s', ignoring: %m", sysname);
+                return 0;
+        }
+        if (r == -ENODEV) {
+                log_device_debug_errno(dev, r, "Device already vanished, ignoring.");
+                return 0;
+        }
+        if (r < 0)
+                return log_device_warning_errno(dev, r, "Failed to get driver for '%s': %m", sysname);
+
+        return udev_builtin_add_property(event->dev, test, "ID_NET_DRIVER", driver);
+}
+
+const UdevBuiltin udev_builtin_net_driver = {
+        .name = "net_driver",
+        .cmd = builtin_net_driver_set_driver,
+        .help = "Set driver for network device",
+        .run_once = true,
+};

src/udev/udev-builtin-net_setup_link.c

@@ -29,9 +29,6 @@ static int builtin_net_setup_link(UdevEvent *event, int argc, char **argv, bool
         if (r < 0)
                 return log_device_warning_errno(dev, r, "Failed to get link information: %m");
 
-        if (link->driver)
-                udev_builtin_add_property(dev, test, "ID_NET_DRIVER", link->driver);
-
         r = link_get_config(ctx, link);
         if (r < 0) {
                 if (r == -ENOENT) {

src/udev/udev-builtin.c

@@ -22,6 +22,7 @@ static const UdevBuiltin *const builtins[_UDEV_BUILTIN_MAX] = {
 #if HAVE_KMOD
         [UDEV_BUILTIN_KMOD] = &udev_builtin_kmod,
 #endif
+        [UDEV_BUILTIN_NET_DRIVER] = &udev_builtin_net_driver,
         [UDEV_BUILTIN_NET_ID] = &udev_builtin_net_id,
         [UDEV_BUILTIN_NET_LINK] = &udev_builtin_net_setup_link,
         [UDEV_BUILTIN_PATH_ID] = &udev_builtin_path_id,

src/udev/udev-builtin.h

@@ -20,6 +20,7 @@ typedef enum UdevBuiltinCommand {
 #if HAVE_KMOD
         UDEV_BUILTIN_KMOD,
 #endif
+        UDEV_BUILTIN_NET_DRIVER,
         UDEV_BUILTIN_NET_ID,
         UDEV_BUILTIN_NET_LINK,
         UDEV_BUILTIN_PATH_ID,
@@ -64,6 +65,7 @@ extern const UdevBuiltin udev_builtin_keyboard;
 #if HAVE_KMOD
 extern const UdevBuiltin udev_builtin_kmod;
 #endif
+extern const UdevBuiltin udev_builtin_net_driver;
 extern const UdevBuiltin udev_builtin_net_id;
 extern const UdevBuiltin udev_builtin_net_setup_link;
 extern const UdevBuiltin udev_builtin_path_id;