udev: allow/denylist for reading sysfs attributes when composing a NIC name

Users can currently pick specific versions of NIC naming, but that
does not guarantee that NIC names won't change after the kernel adds
a new sysfs attribute.

This patch allows for an allow/deny list of sysfs attributes
that could be used when composing the name.

These lists can be supplied as an hwdb entry in the form of
/etc/udev/hwdb.d/50-net-naming-allowlist.hwdb
net:naming:drvirtio_net
  ID_NET_NAME_ALLOW=0
  ID_NET_NAME_ALLOW_ACPI_INDEX=1
  ID_NET_NAME_ALLOW_ADDR_ASSIGN_TYPE=1
  ID_NET_NAME_ALLOW_ADDRESS=1
  ID_NET_NAME_ALLOW_ARI_ENABLED=1
  ID_NET_NAME_ALLOW_DEV_PORT=1
  ID_NET_NAME_ALLOW_FUNCTION_ID=1
  ID_NET_NAME_ALLOW_IFLINK=1
  ID_NET_NAME_ALLOW_INDEX=1
  ID_NET_NAME_ALLOW_LABEL=1
  ID_NET_NAME_ALLOW_PHYS_PORT_NAME=1
  ID_NET_NAME_ALLOW_TYPE=1

src/shared/netif-naming-scheme.c

@@ -1,6 +1,9 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include "sd-device.h"
+
 #include "alloc-util.h"
+#include "device-private.h"
 #include "netif-naming-scheme.h"
 #include "proc-cmdline.h"
 #include "string-util.h"
@@ -101,3 +104,81 @@ static const char* const alternative_names_policy_table[_NAMEPOLICY_MAX] = {
 };
 
 DEFINE_STRING_TABLE_LOOKUP(alternative_names_policy, NamePolicy);
+
+static int naming_sysattr_allowed_by_default(sd_device *dev) {
+        int r;
+
+        assert(dev);
+
+        r = device_get_property_bool(dev, "ID_NET_NAME_ALLOW");
+        if (r == -ENOENT)
+                return true;
+
+        return r;
+}
+
+static int naming_sysattr_allowed(sd_device *dev, const char *sysattr) {
+        char *sysattr_property;
+        int r;
+
+        assert(dev);
+        assert(sysattr);
+
+        sysattr_property = strjoina("ID_NET_NAME_ALLOW_", sysattr);
+        ascii_strupper(sysattr_property);
+
+        r = device_get_property_bool(dev, sysattr_property);
+        if (r == -ENOENT)
+                /* If ID_NET_NAME_ALLOW is not set or set to 1 default is to allow */
+                return naming_sysattr_allowed_by_default(dev);
+
+        return r;
+}
+
+int device_get_sysattr_int_filtered(sd_device *device, const char *sysattr, int *ret_value) {
+        int r;
+
+        r = naming_sysattr_allowed(device, sysattr);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOENT;
+
+        return device_get_sysattr_int(device, sysattr, ret_value);
+}
+
+int device_get_sysattr_unsigned_filtered(sd_device *device, const char *sysattr, unsigned *ret_value) {
+        int r;
+
+        r = naming_sysattr_allowed(device, sysattr);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOENT;
+
+        return device_get_sysattr_unsigned(device, sysattr, ret_value);
+}
+
+int device_get_sysattr_bool_filtered(sd_device *device, const char *sysattr) {
+        int r;
+
+        r = naming_sysattr_allowed(device, sysattr);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOENT;
+
+        return device_get_sysattr_bool(device, sysattr);
+}
+
+int device_get_sysattr_value_filtered(sd_device *device, const char *sysattr, const char **ret_value) {
+        int r;
+
+        r = naming_sysattr_allowed(device, sysattr);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOENT;
+
+        return sd_device_get_sysattr_value(device, sysattr, ret_value);
+}

src/shared/netif-naming-scheme.h

@@ -3,6 +3,8 @@
 
 #include <stdbool.h>
 
+#include "sd-device.h"
+
 #include "macro.h"
 
 /* So here's the deal: net_id is supposed to be an exercise in providing stable names for network devices. However, we
@@ -95,3 +97,8 @@ NamePolicy name_policy_from_string(const char *p) _pure_;
 
 const char *alternative_names_policy_to_string(NamePolicy p) _const_;
 NamePolicy alternative_names_policy_from_string(const char *p) _pure_;
+
+int device_get_sysattr_int_filtered(sd_device *device, const char *sysattr, int *ret_value);
+int device_get_sysattr_unsigned_filtered(sd_device *device, const char *sysattr, unsigned *ret_value);
+int device_get_sysattr_bool_filtered(sd_device *device, const char *sysattr);
+int device_get_sysattr_value_filtered(sd_device *device, const char *sysattr, const char **ret_value);