udev-builtin-net_id: Add DeviceTree-based names for WLAN devices (#39060)

Add support for generating names like wldN based on DeviceTree aliases.

DeviceTree alias names follow de facto conventions. As of writing, there
are so far two ways WLAN devices are represented in DeviceTree aliases
in upstream Linux DTS files:

- Firstly, as wifi0, used for example in t600x-j314-j316.dtsi
- Secondly, as ethernet0 or ethernet1, used for example in
sun8i-q8-common.dtsi, with a comment saying the reason is to "Make
u-boot set mac-address for wifi without an eeprom"

So we need to handle both while generating names. Refactor most of the
logic in names_devicetree() into a helper
names_devicetree_alias_prefix() that takes an alias_prefix instead of
hardcoding "ethernet", and, in the new names_devicetree():

- For prefix "en", use alias_prefix "ethernet"
- For prefix "wl", try alias_prefix "wifi" first, and if that was not
found, fall back to alias_prefix "ethernet"

Since this is a naming scheme change, also gate this behind
NAMING_DEVICETREE_ALIASES_WLAN and NAMING_V259, and document this
change.

man/systemd.net-naming-scheme.xml

@@ -552,6 +552,15 @@
           <xi:include href="version-info.xml" xpointer="v258"/>
           </listitem>
         </varlistentry>
+
+        <varlistentry>
+          <term><constant>v259</constant></term>
+
+          <listitem><para>The naming scheme based on devicetree aliases was extended to support WLAN devices.</para>
+
+          <xi:include href="version-info.xml" xpointer="v259"/>
+          </listitem>
+        </varlistentry>
       </variablelist>
 
     <para>Note that <constant>latest</constant> may be used to denote the latest scheme known (to this

src/shared/netif-naming-scheme.c

@@ -29,6 +29,7 @@ static const NamingScheme naming_schemes[] = {
         { "v255", NAMING_V255 },
         { "v257", NAMING_V257 },
         { "v258", NAMING_V258 },
+        { "v259", NAMING_V259 },
         /* … add more schemes here, as the logic to name devices is updated … */
 
         EXTRA_NET_NAMING_MAP

src/shared/netif-naming-scheme.h

@@ -42,6 +42,7 @@ typedef enum NamingSchemeFlags {
         NAMING_FIRMWARE_NODE_SUN         = 1 << 18, /* Use firmware_node/sun to get PCI slot number */
         NAMING_DEVICETREE_PORT_ALIASES   = 1 << 19, /* Include aliases of OF nodes of a netdev itself, not just its parent. See PR #33958. */
         NAMING_USE_INTERFACE_PROPERTY    = 1 << 20, /* Use INTERFACE udev property, rather than sysname, when no renaming is requested. */
+        NAMING_DEVICETREE_ALIASES_WLAN   = 1 << 21, /* Generate names from devicetree aliases for WLAN devices */
 
         /* And now the masks that combine the features above */
         NAMING_V238 = 0,
@@ -63,6 +64,7 @@ typedef enum NamingSchemeFlags {
         NAMING_V255 = NAMING_V254 & ~NAMING_BRIDGE_MULTIFUNCTION_SLOT,
         NAMING_V257 = NAMING_V255 | NAMING_FIRMWARE_NODE_SUN | NAMING_DEVICETREE_PORT_ALIASES,
         NAMING_V258 = NAMING_V257 | NAMING_USE_INTERFACE_PROPERTY,
+        NAMING_V259 = NAMING_V258 | NAMING_DEVICETREE_ALIASES_WLAN,
 
         EXTRA_NET_NAMING_SCHEMES
 

src/udev/udev-builtin-net_id.c

@@ -788,20 +788,20 @@ static int names_platform(UdevEvent *event, const char *prefix) {
         return 0;
 }
 
-static int names_devicetree(UdevEvent *event, const char *prefix) {
+static int names_devicetree_alias_prefix(UdevEvent *event, const char *prefix, const char *alias_prefix) {
         sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
         _cleanup_(sd_device_unrefp) sd_device *aliases_dev = NULL, *ofnode_dev = NULL, *devicetree_dev = NULL;
         const char *ofnode_path, *ofnode_syspath, *devicetree_syspath;
         int r;
 
         assert(prefix);
+        assert(alias_prefix);
 
-        if (!naming_scheme_has(NAMING_DEVICETREE_ALIASES))
-                return 0;
+        /* Returns 1 if found, 0 if not found, negative if error */
 
-        /* only ethernet supported for now */
-        if (!streq(prefix, "en"))
-                return -EOPNOTSUPP;
+        _cleanup_free_ char *alias_prefix_0 = strjoin(alias_prefix, "0");
+        if (!alias_prefix_0)
+                return log_oom_debug();
 
         /* check if the device itself has an of_node */
         if (naming_scheme_has(NAMING_DEVICETREE_PORT_ALIASES)) {
@@ -860,7 +860,7 @@ static int names_devicetree(UdevEvent *event, const char *prefix) {
                 const char *alias_path, *alias_index, *conflict;
                 unsigned i;
 
-                alias_index = startswith(alias, "ethernet");
+                alias_index = startswith(alias, alias_prefix);
                 if (!alias_index)
                         continue;
 
@@ -873,31 +873,59 @@ static int names_devicetree(UdevEvent *event, const char *prefix) {
                 /* If there's no index, we default to 0... */
                 if (isempty(alias_index)) {
                         i = 0;
-                        conflict = "ethernet0";
+                        conflict = alias_prefix_0;
                 } else {
                         r = safe_atou(alias_index, &i);
                         if (r < 0)
                                 return log_device_debug_errno(dev, r,
                                                 "Could not get index of alias %s: %m", alias);
-                        conflict = "ethernet";
+                        conflict = alias_prefix;
                 }
 
                 /* ...but make sure we don't have an alias conflict */
                 if (i == 0 && device_get_sysattr_value_filtered(aliases_dev, conflict, NULL) >= 0)
                         return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EEXIST),
-                                        "Ethernet alias conflict: ethernet and ethernet0 both exist.");
+                                        "DeviceTree alias conflict: %s and %s both exist.",
+                                        alias_prefix, alias_prefix_0);
 
                 char str[ALTIFNAMSIZ];
                 if (snprintf_ok(str, sizeof str, "%sd%u", prefix, i))
                         udev_builtin_add_property(event, "ID_NET_NAME_ONBOARD", str);
                 log_device_debug(dev, "DeviceTree identifier: alias_index=%u %s \"%s\"",
                                  i, glyph(GLYPH_ARROW_RIGHT), str + strlen(prefix));
-                return 0;
+                return 1;
         }
 
-        return -ENOENT;
+        return 0;
 }
 
+static int names_devicetree(UdevEvent *event, const char *prefix) {
+        int r;
+
+        assert(event);
+        assert(prefix);
+
+        if (!naming_scheme_has(NAMING_DEVICETREE_ALIASES))
+                return 0;
+
+        if (streq(prefix, "en"))
+                r = names_devicetree_alias_prefix(event, prefix, "ethernet");
+        else if (naming_scheme_has(NAMING_DEVICETREE_ALIASES_WLAN) &&
+                 streq(prefix, "wl")) {
+                r = names_devicetree_alias_prefix(event, prefix, "wifi");
+                /* Sometimes DeviceTrees have WLAN devices with alias ethernetN, fall back to those */
+                if (r == 0)
+                        r = names_devicetree_alias_prefix(event, prefix, "ethernet");
+        } else
+                return -EOPNOTSUPP; /* Unsupported interface type */
+        if (r < 0)
+                return r;
+        if (r == 0) /* Not found */
+                return -ENOENT;
+
+        return 0; /* Found */
+};
+
 static int names_pci(UdevEvent *event, const char *prefix) {
         sd_device *parent, *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
         _cleanup_(sd_device_unrefp) sd_device *physfn_pcidev = NULL;