udev-builtin-net_id.c

/* SPDX-License-Identifier: LGPL-2.1-or-later */

/*
 * Predictable network interface device names based on:
 *  - firmware/bios-provided index numbers for on-board devices
 *  - firmware-provided pci-express hotplug slot index number
 *  - physical/geographical location of the hardware
 *  - the interface's MAC address
 *
 * https://systemd.io/PREDICTABLE_INTERFACE_NAMES
 *
 * When the code here is changed, man/systemd.net-naming-scheme.xml must be updated too.
 */

#include <linux/if.h>
#include <linux/if_arp.h>
#include <linux/netdevice.h>
#include <linux/pci_regs.h>
#include <unistd.h>

#include "alloc-util.h"
#include "device-private.h"
#include "device-util.h"
#include "dirent-util.h"
#include "ether-addr-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "glyph-util.h"
#include "netif-naming-scheme.h"
#include "parse-util.h"
#include "stdio-util.h"
#include "string-util.h"
#include "udev-builtin.h"

#define ONBOARD_14BIT_INDEX_MAX ((1U << 14) - 1)
#define ONBOARD_16BIT_INDEX_MAX ((1U << 16) - 1)

static int device_get_parent_skip_virtio(sd_device *dev, sd_device **ret) {
        int r;

        assert(dev);
        assert(ret);

        /* This provides the parent device, but skips intermediate virtio devices. There can only ever be one
         * virtio bus per parent device, so we can safely ignore any virtio buses. See
         * https://lore.kernel.org/virtualization/CAPXgP137A=CdmggtVPUZXbnpTbU9Tewq-sOjg9T8ohYktct1kQ@mail.gmail.com/ */

        for (;;) {
                r = sd_device_get_parent(dev, &dev);
                if (r < 0)
                        return r;

                r = device_in_subsystem(dev, "virtio");
                if (r < 0)
                        return r;
                if (r == 0) {
                        *ret = dev;
                        return 0;
                }
        }
}

static int get_matching_parent(
                sd_device *dev,
                char * const *parent_subsystems,
                bool skip_virtio,
                sd_device **ret) {

        sd_device *parent;
        int r;

        assert(dev);

        if (skip_virtio)
                r = device_get_parent_skip_virtio(dev, &parent);
        else
                r = sd_device_get_parent(dev, &parent);
        if (r < 0)
                return r;

        /* check if our direct parent is in an expected subsystem. */
        r = device_in_subsystem_strv(parent, parent_subsystems);
        if (r < 0)
                return r;
        if (r == 0)
                return -ENODEV;

        if (ret)
                *ret = parent;
        return 0;
}

static int get_first_syspath_component(sd_device *dev, const char *prefix, char **ret) {
        _cleanup_free_ char *buf = NULL;
        const char *syspath, *p, *q;
        int r;

        assert(dev);
        assert(prefix);
        assert(ret);

        r = sd_device_get_syspath(dev, &syspath);
        if (r < 0)
                return r;

        p = path_startswith(syspath, prefix);
        if (!p)
                return -EINVAL;

        r = path_find_first_component(&p, /* accept_dot_dot= */ false, &q);
        if (r < 0)
                return r;

        buf = strndup(q, r);
        if (!buf)
                return -ENOMEM;

        *ret = TAKE_PTR(buf);
        return r; /* return the length of the string */
}

static int get_virtfn_info(sd_device *pcidev, sd_device **ret_physfn_pcidev, char **ret_suffix) {
        _cleanup_(sd_device_unrefp) sd_device *physfn_pcidev = NULL;
        const char *syspath, *name;
        int r;

        assert(pcidev);
        assert(ret_physfn_pcidev);
        assert(ret_suffix);

        r = sd_device_get_syspath(pcidev, &syspath);
        if (r < 0)
                return r;

        /* Get physical function's pci device. */
        r = sd_device_new_child(&physfn_pcidev, pcidev, "physfn");
        if (r < 0)
                return r;

        /* Find the virtual function number by finding the right virtfn link. */
        FOREACH_DEVICE_CHILD_WITH_SUFFIX(physfn_pcidev, child, name) {
                const char *n, *s;

                /* Only accepts e.g. virtfn0, virtfn1, and so on. */
                n = startswith(name, "virtfn");
                if (isempty(n) || !in_charset(n, DIGITS))
                        continue;

                if (sd_device_get_syspath(child, &s) < 0)
                        continue;

                if (streq(s, syspath)) {
                        char *suffix;

                        suffix = strjoin("v", n);
                        if (!suffix)
                                return -ENOMEM;

                        *ret_physfn_pcidev = sd_device_ref(physfn_pcidev);
                        *ret_suffix = suffix;
                        return 0;
                }
        }

        return -ENOENT;
}

static int get_subfunc_info(sd_device *aux_dev, sd_device **ret_parent_pcidev, char **ret_suffix) {
        sd_device *parent;
        unsigned sfnum;
        char *suffix;
        int r;

        assert(aux_dev);
        assert(ret_parent_pcidev);
        assert(ret_suffix);

        /* The auxiliary device must expose an 'sfnum' attribute. This is currently used by the
         * mlx5_core driver for sub-function (SF) auxiliary devices. The sfnum is the user-defined
         * stable identifier passed to "devlink port add ... sfnum N". */
        r = device_get_sysattr_unsigned_filtered(aux_dev, "sfnum", &sfnum);
        if (r < 0)
                return r;

        /* Walk one hop up: the auxiliary device's parent must be a PCI function. It can be either
         * the PF directly, or an SR-IOV VF — mlx5 also supports SFs hosted on VFs (VF-SF), see
         * Documentation/networking/representors.rst in the kernel tree. The VF case is handled by
         * the existing virtfn logic in names_pci(), so here we just return the immediate PCI
         * parent and a single "S<sfnum>" suffix piece. */
        r = sd_device_get_parent(aux_dev, &parent);
        if (r < 0)
                return r;

        r = device_in_subsystem(parent, "pci");
        if (r < 0)
                return r;
        if (r == 0)
                return -ENODEV;

        if (asprintf(&suffix, "S%u", sfnum) < 0)
                return log_oom_debug();

        *ret_parent_pcidev = sd_device_ref(parent);
        *ret_suffix = suffix;
        return 0;
}

static int get_port_specifier(sd_device *dev, char **ret) {
        const char *phys_port_name;
        unsigned dev_port;
        char *buf;
        int r;

        assert(dev);
        assert(ret);

        /* First, try to use the kernel provided front panel port name for multiple port PCI device. */
        r = device_get_sysattr_safe_string_filtered(dev, "phys_port_name", &phys_port_name);
        if (r >= 0 && !isempty(phys_port_name)) {
                if (naming_scheme_has(NAMING_SR_IOV_R)) {
                        int vf_id = -1;

                        /* Check if phys_port_name indicates virtual device representor. */
                        (void) sscanf(phys_port_name, "pf%*uvf%d", &vf_id);

                        if (vf_id >= 0) {
                                /* For VF representor append 'r<VF_NUM>'. */
                                if (asprintf(&buf, "r%d", vf_id) < 0)
                                        return log_oom_debug();

                                *ret = buf;
                                return 1;
                        }
                }

                /* Otherwise, use phys_port_name as is. */
                buf = strjoin("n", phys_port_name);
                if (!buf)
                        return log_oom_debug();

                *ret = buf;
                return 1;
        }

        /* Then, try to use the kernel provided port index for the case when multiple ports on a single PCI
         * function. */
        r = device_get_sysattr_unsigned_filtered(dev, "dev_port", &dev_port);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to get device port index: %m");
        if (r > 0) {
                assert(dev_port > 0);
                if (asprintf(&buf, "d%u", dev_port) < 0)
                        return log_oom_debug();

                *ret = buf;
                return 1;
        }

        *ret = NULL;
        return 0;
}

static bool is_valid_onboard_index(unsigned idx) {
        /* Some BIOSes report rubbish indexes that are excessively high (2^24-1 is an index VMware likes to
         * report for example). Let's define a cut-off where we don't consider the index reliable anymore. We
         * pick some arbitrary cut-off, which is somewhere beyond the realistic number of physical network
         * interface a system might have. Ideally the kernel would already filter this crap for us, but it
         * doesn't currently. The initial cut-off value (2^14-1) was too conservative for s390 PCI which
         * allows for index values up 2^16-1 which is now enabled with the NAMING_16BIT_INDEX naming flag. */
        return idx <= (naming_scheme_has(NAMING_16BIT_INDEX) ? ONBOARD_16BIT_INDEX_MAX : ONBOARD_14BIT_INDEX_MAX);
}

static int pci_get_onboard_index(sd_device *dev, unsigned *ret) {
        unsigned idx;
        int r;

        assert(dev);
        assert(ret);

        /* ACPI _DSM — device specific method for naming a PCI or PCI Express device */
        r = device_get_sysattr_unsigned_filtered(dev, "acpi_index", &idx);
        if (r < 0)
                /* SMBIOS type 41 — Onboard Devices Extended Information */
                r = device_get_sysattr_unsigned_filtered(dev, "index", &idx);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Could not obtain onboard index: %m");

        if (idx == 0 && !naming_scheme_has(NAMING_ZERO_ACPI_INDEX))
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "Naming scheme does not allow onboard index==0.");
        if (!is_valid_onboard_index(idx))
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "Not a valid onboard index: %u", idx);

        *ret = idx;
        return 0;
}

static int names_pci_onboard(UdevEvent *event, sd_device *pci_dev, const char *prefix, const char *suffix) {
        sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        _cleanup_free_ char *port = NULL;
        unsigned idx = 0;  /* avoid false maybe-uninitialized warning */
        int r;

        assert(pci_dev);
        assert(prefix);

        /* retrieve on-board index number from firmware */
        r = pci_get_onboard_index(pci_dev, &idx);
        if (r < 0)
                return r;

        r = get_port_specifier(dev, &port);
        if (r < 0)
                return r;

        char str[ALTIFNAMSIZ];
        if (snprintf_ok(str, sizeof str, "%so%u%s%s", prefix, idx, strempty(port), strempty(suffix)))
                udev_builtin_add_property(event, "ID_NET_NAME_ONBOARD", str);

        log_device_debug(dev, "PCI onboard index identifier: index=%u port=%s %s %s",
                         idx, strna(port),
                         glyph(GLYPH_ARROW_RIGHT), empty_to_na(str));

        return 0;
}

static int names_pci_onboard_label(UdevEvent *event, sd_device *pci_dev, const char *prefix) {
        sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        const char *label;
        int r;

        assert(prefix);

        /* retrieve on-board label from firmware */
        r = device_get_sysattr_safe_string_filtered(pci_dev, "label", &label);
        if (r < 0)
                return log_device_debug_errno(pci_dev, r, "Failed to get PCI onboard label: %m");

        char str[ALTIFNAMSIZ];
        if (snprintf_ok(str, sizeof str, "%s%s",
                        naming_scheme_has(NAMING_LABEL_NOPREFIX) ? "" : prefix,
                        label))
                udev_builtin_add_property(event, "ID_NET_LABEL_ONBOARD", str);

        log_device_debug(dev, "Onboard label from PCI device: %s", label);
        return 0;
}

/* read the 256 bytes PCI configuration space to check the multi-function bit */
static int is_pci_multifunction(sd_device *dev) {
        _cleanup_free_ uint8_t *config = NULL;
        const char *filename, *syspath;
        size_t len;
        int r;

        assert(dev);

        r = sd_device_get_syspath(dev, &syspath);
        if (r < 0)
                return r;

        filename = strjoina(syspath, "/config");
        r = read_virtual_file(filename, PCI_HEADER_TYPE + 1, (char **) &config, &len);
        if (r < 0)
                return r;
        if (len < PCI_HEADER_TYPE + 1)
                return -EINVAL;

#ifndef PCI_HEADER_TYPE_MULTIFUNC
#define PCI_HEADER_TYPE_MULTIFUNC 0x80
#endif

        /* bit 0-6 header type, bit 7 multi/single function device */
        return config[PCI_HEADER_TYPE] & PCI_HEADER_TYPE_MULTIFUNC;
}

static bool is_pci_ari_enabled(sd_device *dev) {
        assert(dev);

        return device_get_sysattr_bool_filtered(dev, "ari_enabled") > 0;
}

static bool is_pci_bridge(sd_device *dev) {
        const char *v, *p;

        assert(dev);

        if (device_get_sysattr_safe_string_filtered(dev, "modalias", &v) < 0)
                return false;

        if (!startswith(v, "pci:"))
                return false;

        p = strrchr(v, 's');
        if (!p)
                return false;
        if (p[1] != 'c')
                return false;

        /* PCI device subclass 04 corresponds to PCI bridge */
        bool b = strneq(p + 2, "04", 2);
        if (b)
                log_device_debug(dev, "Device is a PCI bridge.");
        return b;
}

static int parse_hotplug_slot_from_function_id(sd_device *dev, int slots_dirfd, uint32_t *ret) {
        uint64_t function_id;
        char filename[NAME_MAX+1];
        const char *attr;
        int r;

        /* The <sysname>/function_id attribute is unique to the s390 PCI driver. If present, we know that the
         * slot's directory name for this device is /sys/bus/pci/slots/XXXXXXXX/ where XXXXXXXX is the fixed
         * length 8 hexadecimal character string representation of function_id. Therefore we can short cut
         * here and just check for the existence of the slot directory. As this directory has to exist, we're
         * emitting a debug message for the unlikely case it's not found. Note that the domain part doesn't
         * belong to the slot name here because there's a 1-to-1 relationship between PCI function and its
         * hotplug slot. See https://docs.kernel.org/arch/s390/pci.html for more details. */

        assert(dev);
        assert(slots_dirfd >= 0);
        assert(ret);

        if (!naming_scheme_has(NAMING_SLOT_FUNCTION_ID)) {
                *ret = 0;
                return 0;
        }

        if (device_get_sysattr_safe_string_filtered(dev, "function_id", &attr) < 0) {
                *ret = 0;
                return 0;
        }

        r = safe_atou64(attr, &function_id);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to parse function_id, ignoring: '%s'", attr);

        if (function_id <= 0 || function_id > UINT32_MAX)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "Invalid function id (0x%"PRIx64"), ignoring.",
                                              function_id);

        if (!snprintf_ok(filename, sizeof(filename), "%08"PRIx64, function_id))
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(ENAMETOOLONG),
                                              "PCI slot path is too long, ignoring.");

        if (faccessat(slots_dirfd, filename, F_OK, 0) < 0)
                return log_device_debug_errno(dev, errno, "Cannot access '%s' under pci slots, ignoring: %m", filename);

        *ret = (uint32_t) function_id;
        return 1; /* Found. We should ignore domain part. */
}

static int pci_get_hotplug_slot_from_address(
                sd_device *dev,
                sd_device *pci,
                DIR *dir,
                uint32_t *ret) {

        const char *sysname;
        int r;

        assert(dev);
        assert(pci);
        assert(dir);
        assert(ret);

        r = sd_device_get_sysname(dev, &sysname);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to get sysname: %m");

        rewinddir(dir);
        FOREACH_DIRENT_ALL(de, dir, break) {
                _cleanup_free_ char *path = NULL;
                const char *address;
                uint32_t slot;

                if (dot_or_dot_dot(de->d_name))
                        continue;

                if (de->d_type != DT_DIR)
                        continue;

                r = safe_atou32(de->d_name, &slot);
                if (r < 0 || slot <= 0)
                        continue;

                path = path_join("slots", de->d_name, "address");
                if (!path)
                        return log_oom_debug();

                if (device_get_sysattr_safe_string_filtered(pci, path, &address) < 0)
                        continue;

                /* match slot address with device by stripping the function */
                if (!startswith(sysname, address))
                        continue;

                *ret = slot;
                return 1; /* found */
        }

        *ret = 0;
        return 0; /* not found */
}

static int pci_get_hotplug_slot(sd_device *dev, uint32_t *ret) {
        _cleanup_(sd_device_unrefp) sd_device *pci = NULL;
        _cleanup_closedir_ DIR *dir = NULL;
        int r;

        assert(dev);
        assert(ret);

        /* ACPI _SUN — slot user number */
        r = sd_device_new_from_subsystem_sysname(&pci, "subsystem", "pci");
        if (r < 0)
                return log_debug_errno(r, "Failed to create sd_device object for pci subsystem: %m");

        r = device_opendir(pci, "slots", &dir);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Cannot open 'slots' subdirectory: %m");

        for (sd_device *slot_dev = dev; slot_dev; ) {
                uint32_t slot = 0;  /* avoid false maybe-uninitialized warning */

                r = parse_hotplug_slot_from_function_id(slot_dev, dirfd(dir), &slot);
                if (r < 0)
                        return r;
                if (r > 0) {
                        *ret = slot;
                        return 1; /* domain should be ignored. */
                }

                r = pci_get_hotplug_slot_from_address(slot_dev, pci, dir, &slot);
                if (r < 0)
                        return r;
                if (r > 0) {
                        /* We found the match between PCI device and slot. However, we won't use the slot
                         * index if the device is a PCI bridge, because it can have other child devices that
                         * will try to claim the same index and that would create name collision. */
                        if (naming_scheme_has(NAMING_BRIDGE_NO_SLOT) && is_pci_bridge(slot_dev)) {
                                if (naming_scheme_has(NAMING_BRIDGE_MULTIFUNCTION_SLOT) && is_pci_multifunction(dev) <= 0)
                                        return log_device_debug_errno(dev, SYNTHETIC_ERRNO(ESTALE),
                                                                      "Not using slot information because the PCI device associated with "
                                                                      "the hotplug slot is a bridge and the PCI device has a single function.");

                                if (!naming_scheme_has(NAMING_BRIDGE_MULTIFUNCTION_SLOT))
                                        return log_device_debug_errno(dev, SYNTHETIC_ERRNO(ESTALE),
                                                                      "Not using slot information because the PCI device is a bridge.");
                        }

                        *ret = slot;
                        return 0; /* domain can be still used. */
                }

                if (sd_device_get_parent_with_subsystem_devtype(slot_dev, "pci", NULL, &slot_dev) < 0)
                        break;
        }

        return -ENOENT;
}

static int get_device_firmware_node_sun(sd_device *dev, uint32_t *ret) {
        const char *attr;
        int r;

        assert(dev);
        assert(ret);

        r = device_get_sysattr_safe_string_filtered(dev, "firmware_node/sun", &attr);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to read firmware_node/sun, ignoring: %m");

        uint32_t sun;
        r = safe_atou32(attr, &sun);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to parse firmware_node/sun '%s', ignoring: %m", attr);
        if (sun == 0)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL), "firmware_node/sun == 0, ignoring.");

        *ret = sun;
        return 0;
}

static int pci_get_slot_from_firmware_node_sun(sd_device *dev, uint32_t *ret) {
        sd_device *slot_dev;
        int r;

        assert(dev);
        assert(ret);

        if (!naming_scheme_has(NAMING_FIRMWARE_NODE_SUN))
                return -EOPNOTSUPP;

        /* Try getting the ACPI _SUN for the device */
        if (get_device_firmware_node_sun(dev, ret) >= 0)
                return 0;

        r = sd_device_get_parent_with_subsystem_devtype(dev, "pci", NULL, &slot_dev);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to find parent PCI device, ignoring: %m");

        if (is_pci_bridge(slot_dev) && is_pci_multifunction(dev) <= 0)
                return log_device_debug_errno(
                                dev, SYNTHETIC_ERRNO(ESTALE),
                                "Not using slot information because the parent PCI slot is a bridge and the PCI device is not multifunction.");

        /* Try getting the ACPI _SUN from the parent pcieport */
        if (get_device_firmware_node_sun(slot_dev, ret) >= 0)
                return 0;

        return -ENOENT;
}

static int get_pci_slot_specifiers(
                sd_device *dev,
                char **ret_domain,
                char **ret_bus_and_slot,
                char **ret_func) {

        _cleanup_free_ char *domain_spec = NULL, *bus_and_slot_spec = NULL, *func_spec = NULL;
        unsigned domain, bus, slot, func;
        const char *sysname;
        int r;

        assert(dev);
        assert(ret_domain);
        assert(ret_bus_and_slot);
        assert(ret_func);

        r = sd_device_get_sysname(dev, &sysname);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to get sysname: %m");

        r = sscanf(sysname, "%x:%x:%x.%u", &domain, &bus, &slot, &func);
        if (r != 4)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "Failed to parse slot information from PCI device sysname.");

        if (naming_scheme_has(NAMING_NPAR_ARI) &&
            is_pci_ari_enabled(dev))
                /* ARI devices support up to 256 functions on a single device ("slot"), and interpret the
                 * traditional 5-bit slot and 3-bit function number as a single 8-bit function number,
                 * where the slot makes up the upper 5 bits. */
                func += slot * 8;

        /* Include the PCI domain in the name if the ID_NET_NAME_INCLUDE_DOMAIN property says so, if it is
         * set. If it is not set, include it if the domain is non-zero. */
        r = device_get_property_bool(dev, "ID_NET_NAME_INCLUDE_DOMAIN");
        if (r < 0) {
                if (r != -ENOENT)
                        log_device_warning_errno(dev, r, "Failed to read property \"ID_NET_NAME_INCLUDE_DOMAIN\", ignoring: %m");

                r = domain > 0;
        }
        if (r > 0 && asprintf(&domain_spec, "P%u", domain) < 0)
                return log_oom_debug();

        if (asprintf(&bus_and_slot_spec, "p%us%u", bus, slot) < 0)
                return log_oom_debug();

        if ((func > 0 || is_pci_multifunction(dev) > 0) &&
            asprintf(&func_spec, "f%u", func) < 0)
                return log_oom_debug();

        *ret_domain = TAKE_PTR(domain_spec);
        *ret_bus_and_slot = TAKE_PTR(bus_and_slot_spec);
        *ret_func = TAKE_PTR(func_spec);
        return 0;
}

static int names_pci_slot(UdevEvent *event, sd_device *pci_dev, const char *prefix, const char *suffix) {
        sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        _cleanup_free_ char *domain = NULL, *bus_and_slot = NULL, *func = NULL, *port = NULL;
        uint32_t slot = 0;  /* avoid false maybe-uninitialized warning */
        char str[ALTIFNAMSIZ];
        int r;

        assert(pci_dev);
        assert(prefix);

        r = get_pci_slot_specifiers(pci_dev, &domain, &bus_and_slot, &func);
        if (r < 0)
                return r;

        r = get_port_specifier(dev, &port);
        if (r < 0)
                return r;

        /* compose a name based on the raw kernel's PCI bus, slot numbers */
        if (snprintf_ok(str, sizeof str, "%s%s%s%s%s%s",
                        prefix, strempty(domain), bus_and_slot, strempty(func), strempty(port), strempty(suffix)))
                udev_builtin_add_property(event, "ID_NET_NAME_PATH", str);

        log_device_debug(dev, "PCI path identifier: domain=%s bus_and_slot=%s func=%s port=%s %s %s",
                         strna(domain), bus_and_slot, strna(func), strna(port),
                         glyph(GLYPH_ARROW_RIGHT), empty_to_na(str));

        if (pci_get_slot_from_firmware_node_sun(pci_dev, &slot) < 0) {
                /* If we don't find a slot using firmware_node/sun, fallback to hotplug_slot */
                r = pci_get_hotplug_slot(pci_dev, &slot);
                if (r < 0)
                        return r;
                if (r > 0)
                        /* If the hotplug slot is found through the function ID, then drop the domain from the name.
                        * See comments in parse_hotplug_slot_from_function_id(). */
                        domain = mfree(domain);
        }

        if (snprintf_ok(str, sizeof str, "%s%ss%"PRIu32"%s%s%s",
                        prefix, strempty(domain), slot, strempty(func), strempty(port), strempty(suffix)))
                udev_builtin_add_property(event, "ID_NET_NAME_SLOT", str);

        log_device_debug(dev, "PCI slot identifier: domain=%s slot=%"PRIu32" func=%s port=%s %s %s",
                         strna(domain), slot, strna(func), strna(port),
                         glyph(GLYPH_ARROW_RIGHT), empty_to_na(str));

        return 0;
}

static int names_vio(UdevEvent *event, const char *prefix) {
        sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        _cleanup_free_ char *s = NULL;
        unsigned slotid;
        int r;

        assert(prefix);

        /* get ibmveth/ibmvnic slot-based names. */

        /* check if our direct parent is a VIO device with no other bus in-between */
        if (get_matching_parent(dev, STRV_MAKE("vio"), /* skip_virtio= */ false, NULL) < 0)
                return 0;

        log_device_debug(dev, "Parent device is in the vio subsystem.");

        /* The devices' $DEVPATH number is tied to (virtual) hardware (slot id
         * selected in the HMC), thus this provides a reliable naming (e.g.
         * "/devices/vio/30000002/net/eth1"); we ignore the bus number, as
         * there should only ever be one bus, and then remove leading zeros. */
        r = get_first_syspath_component(dev, "/sys/devices/vio/", &s);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to get VIO bus ID and slot ID: %m");

        if (r != 8)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "VIO bus ID and slot ID have invalid length: '%s'", s);

        if (!in_charset(s, HEXDIGITS))
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "VIO bus ID and slot ID contain invalid characters: '%s'", s);

        /* Parse only slot ID (the last 4 hexdigits). */
        r = safe_atou_full(s + 4, 16, &slotid);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to parse VIO slot from '%s': %m", s);

        char str[ALTIFNAMSIZ];
        if (snprintf_ok(str, sizeof str, "%sv%u", prefix, slotid))
                udev_builtin_add_property(event, "ID_NET_NAME_SLOT", str);
        log_device_debug(dev, "Vio slot identifier: slotid=%u %s %s",
                         slotid, glyph(GLYPH_ARROW_RIGHT), str + strlen(prefix));
        return 0;
}

static int names_platform(UdevEvent *event, const char *prefix) {
        sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        _cleanup_free_ char *p = NULL;
        const char *validchars;
        char *vendor, *model_str, *instance_str;
        unsigned model, instance;
        int r;

        assert(prefix);

        /* get ACPI path names for ARM64 platform devices */

        /* check if our direct parent is a platform device with no other bus in-between */
        if (get_matching_parent(dev, STRV_MAKE("platform"), /* skip_virtio= */ false, NULL) < 0)
                return 0;

        log_device_debug(dev, "Parent device is in the platform subsystem.");

        r = get_first_syspath_component(dev, "/sys/devices/platform/", &p);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to get platform ID: %m");

        /* Platform devices are named after ACPI table match, and instance id
         * eg. "/sys/devices/platform/HISI00C2:00"
         * The Vendor (3 or 4 char), followed by hexadecimal model number : instance id. */
        if (r == 10 && p[7] == ':') {
                /* 3 char vendor string */
                vendor = strndupa_safe(p, 3);
                model_str = strndupa_safe(p + 3, 4);
                instance_str = strndupa_safe(p + 8, 2);
                validchars = UPPERCASE_LETTERS;
        } else if (r == 11 && p[8] == ':') {
                /* 4 char vendor string */
                vendor = strndupa_safe(p, 4);
                model_str = strndupa_safe(p + 4, 4);
                instance_str = strndupa_safe(p + 9, 2);
                validchars = UPPERCASE_LETTERS DIGITS;
        } else
                return -EOPNOTSUPP;

        if (!in_charset(vendor, validchars))
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "Platform vendor contains invalid characters: '%s'", vendor);

        ascii_strlower(vendor);

        r = safe_atou_full(model_str, 16, &model);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to parse model number \"%s\": %m", model_str);

        r = safe_atou_full(instance_str, 16, &instance);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to parse instance id \"%s\": %m", instance_str);

        char str[ALTIFNAMSIZ];
        if (snprintf_ok(str, sizeof str, "%sa%s%xi%u", prefix, vendor, model, instance))
                udev_builtin_add_property(event, "ID_NET_NAME_PATH", str);
        log_device_debug(dev, "Platform identifier: vendor=%s model=%x instance=%u %s %s",
                         vendor, model, instance, glyph(GLYPH_ARROW_RIGHT), str + strlen(prefix));
        return 0;
}

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);

        /* Returns 1 if found, 0 if not found, negative if error */

        _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)) {
                r = sd_device_new_child(&ofnode_dev, dev, "of_node");
                if (r < 0)
                        log_device_debug_errno(dev, r, "Failed to get device of_node, ignoring: %m");
        }
        if (!ofnode_dev) {
                sd_device *parent;

                /* check if our direct parent has an of_node as a fallback */
                r = sd_device_get_parent(dev, &parent);
                if (r < 0)
                        return log_device_debug_errno(dev, r, "Failed to get parent device: %m");

                r = sd_device_new_child(&ofnode_dev, parent, "of_node");
                if (r < 0)
                        return log_device_debug_errno(parent, r, "Failed to get device of_node: %m");
        }

        r = sd_device_get_syspath(ofnode_dev, &ofnode_syspath);
        if (r < 0)
                return log_device_debug_errno(ofnode_dev, r, "Failed to get syspath: %m");

        /* /proc/device-tree should be a symlink to /sys/firmware/devicetree/base. */
        r = sd_device_new_from_path(&devicetree_dev, "/proc/device-tree");
        if (r < 0)
                return log_debug_errno(r, "Failed to create sd-device object from '/proc/device-tree': %m");

        r = sd_device_get_syspath(devicetree_dev, &devicetree_syspath);
        if (r < 0)
                return log_device_debug_errno(devicetree_dev, r, "Failed to get syspath: %m");

        /*
         * Example paths:
         * devicetree_syspath = /sys/firmware/devicetree/base
         * ofnode_syspath = /sys/firmware/devicetree/base/soc/ethernet@deadbeef
         * ofnode_path = soc/ethernet@deadbeef
         */
        ofnode_path = path_startswith(ofnode_syspath, devicetree_syspath);
        if (!ofnode_path)
                return log_device_debug_errno(ofnode_dev, SYNTHETIC_ERRNO(EINVAL),
                                              "The device '%s' is not a child device of '%s'.",
                                              ofnode_syspath, devicetree_syspath);

        /* Get back our leading / to match the contents of the aliases */
        ofnode_path--;
        assert(path_is_absolute(ofnode_path));

        r = sd_device_new_child(&aliases_dev, devicetree_dev, "aliases");
        if (r < 0)
                return log_device_debug_errno(devicetree_dev, r,
                                              "Failed to get 'aliases' child device: %m");

        FOREACH_DEVICE_SYSATTR(aliases_dev, alias) {
                const char *alias_path, *alias_index, *conflict;
                unsigned i;

                alias_index = startswith(alias, alias_prefix);
                if (!alias_index)
                        continue;

                if (device_get_sysattr_safe_string_filtered(aliases_dev, alias, &alias_path) < 0)
                        continue;

                if (!path_equal(ofnode_path, alias_path))
                        continue;

                /* If there's no index, we default to 0... */
                if (isempty(alias_index)) {
                        i = 0;
                        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 = alias_prefix;
                }

                /* ...but make sure we don't have an alias conflict */
                if (i == 0 && device_get_sysattr_safe_string_filtered(aliases_dev, conflict, NULL) >= 0)
                        return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EEXIST),
                                        "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 1;
        }

        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, *parent_pcidev = NULL;
        _cleanup_free_ char *virtfn_suffix = NULL, *subfunc_suffix = NULL, *combined_suffix = NULL;
        const char *suffix = NULL;

        assert(prefix);

        /* If the network device's direct parent is an auxiliary device that exposes a stable
         * 'sfnum' attribute (currently mlx5_core sub-functions), peel off the SF identity into
         * a 'S<sfnum>' suffix piece and pick up the aux device's underlying PCI function as
         * 'parent'. The aux device is just a bump on the path; everything below — PF/VF
         * resolution, slot/onboard lookup — proceeds the same way as for any PCI-rooted
         * network device. */
        if (naming_scheme_has(NAMING_SUBFUNC)) {
                sd_device *aux;

                if (get_matching_parent(dev, STRV_MAKE("auxiliary"),
                                        /* skip_virtio= */ false, &aux) >= 0)
                        (void) get_subfunc_info(aux, &parent_pcidev, &subfunc_suffix);
        }

        /* SF: parent is the aux device's PCI function. Otherwise the network device's direct
         * parent must itself be a PCI device. */
        if (subfunc_suffix)
                parent = parent_pcidev;
        else if (get_matching_parent(dev, STRV_MAKE("pci"), /* skip_virtio= */ true, &parent) < 0)
                return 0;

        /* If parent is an SR-IOV VF, walk to the parent PF and add a 'v<N>' suffix piece. The
         * onboard BIOS label is intentionally not exposed for any "child function" (VF, SF, or
         * VF-SF), since the label refers to the parent's physical port, not to a logical child. */
        bool is_child_function = !!subfunc_suffix;
        if (naming_scheme_has(NAMING_SR_IOV_V) &&
            get_virtfn_info(parent, &physfn_pcidev, &virtfn_suffix) >= 0) {
                parent = physfn_pcidev;
                is_child_function = true;
        }
        if (!is_child_function)
                (void) names_pci_onboard_label(event, parent, prefix);

        /* Compose the final suffix in PF -> [VF ->] SF order, e.g. "v0", "S88", or "v0S88". */
        if (virtfn_suffix && subfunc_suffix) {
                combined_suffix = strjoin(virtfn_suffix, subfunc_suffix);
                if (!combined_suffix)
                        return log_oom_debug();
                suffix = combined_suffix;
        } else
                suffix = virtfn_suffix ?: subfunc_suffix;

        (void) names_pci_onboard(event, parent, prefix, suffix);
        (void) names_pci_slot(event, parent, prefix, suffix);
        return 0;
}

static int get_usb_specifier(sd_device *dev, char **ret) {
        char *ports, *config, *interf, *buf;
        const char *sysname;
        int r;

        assert(dev);
        assert(ret);

        r = sd_device_get_sysname(dev, &sysname);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to get sysname: %m");

        /* get USB port number chain, configuration, interface */
        const char *s = strchr(sysname, '-');
        if (!s)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "sysname \"%s\" does not have '-' in the expected place.", sysname);

        ports = strdupa_safe(s + 1);
        char *t = strchr(ports, ':');
        if (!t)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "sysname \"%s\" does not have ':' in the expected place.", sysname);

        *t = '\0';
        config = t + 1;
        t = strchr(config, '.');
        if (!t)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "sysname \"%s\" does not have '.' in the expected place.", sysname);

        *t = '\0';
        interf = t + 1;

        /* prefix every port number in the chain with "u" */
        string_replace_char(ports, '.', 'u');

        /* suppress the common config == 1 */
        if (streq(config, "1"))
                config = NULL;

        /* suppress the interface == 0 */
        if (streq(interf, "0"))
                interf = NULL;

        buf = strjoin("u", ports,
                      config ? "c" : "", strempty(config),
                      interf ? "i" : "", strempty(interf));
        if (!buf)
                return log_oom_debug();

        log_device_debug(dev, "USB name identifier: ports=%s config=%s interface=%s %s %s",
                         ports, strna(config), strna(interf),
                         glyph(GLYPH_ARROW_RIGHT), buf);

        *ret = buf;
        return 0;
}

static int names_usb(UdevEvent *event, const char *prefix) {
        sd_device *usbdev, *pcidev, *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        _cleanup_free_ char *suffix = NULL;
        int r;

        assert(prefix);

        /* USB device */

        r = sd_device_get_parent_with_subsystem_devtype(dev, "usb", "usb_interface", &usbdev);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Could not find USB parent device: %m");

        r = get_usb_specifier(usbdev, &suffix);
        if (r < 0)
                return r;

        /* If the USB bus is on PCI bus, then suffix the USB specifier to the name based on the PCI bus. */
        r = sd_device_get_parent_with_subsystem_devtype(usbdev, "pci", NULL, &pcidev);
        if (r >= 0)
                return names_pci_slot(event, pcidev, prefix, suffix);

        if (r != -ENOENT || !naming_scheme_has(NAMING_USB_HOST))
                return log_device_debug_errno(usbdev, r, "Failed to get parent PCI bus: %m");

        /* Otherwise, e.g. on-chip asics that have USB ports, use the USB specifier as is. */
        char str[ALTIFNAMSIZ];
        if (snprintf_ok(str, sizeof str, "%s%s", prefix, suffix))
                udev_builtin_add_property(event, "ID_NET_NAME_PATH", str);

        return 0;
}

static int get_bcma_specifier(sd_device *dev, char **ret) {
        const char *sysname;
        char *buf = NULL;
        unsigned core;
        int r;

        assert(dev);
        assert(ret);

        r = sd_device_get_sysname(dev, &sysname);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to get sysname: %m");

        /* bus num:core num */
        r = sscanf(sysname, "bcma%*u:%u", &core);
        if (r != 1)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "Failed to parse BCMA device information.");

        /* suppress the common core == 0 */
        if (core > 0 && asprintf(&buf, "b%u", core) < 0)
                return log_oom_debug();

        log_device_debug(dev, "BCMA core identifier: core=%u %s \"%s\"",
                         core, glyph(GLYPH_ARROW_RIGHT), strna(buf));

        *ret = buf;
        return 0;
}

static int names_bcma(UdevEvent *event, const char *prefix) {
        sd_device *bcmadev, *pcidev, *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        _cleanup_free_ char *suffix = NULL;
        int r;

        assert(prefix);

        r = sd_device_get_parent_with_subsystem_devtype(dev, "bcma", NULL, &bcmadev);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Could not get BCMA parent device: %m");

        r = sd_device_get_parent_with_subsystem_devtype(bcmadev, "pci", NULL, &pcidev);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Could not get PCI parent device: %m");

        r = get_bcma_specifier(bcmadev, &suffix);
        if (r < 0)
                return r;

        return names_pci_slot(event, pcidev, prefix, suffix);
}

static int names_ccw(UdevEvent *event, const char *prefix) {
        sd_device *cdev, *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        const char *bus_id;
        size_t bus_id_start, bus_id_len;
        int r;

        assert(prefix);

        /* get path names for Linux on System z network devices */

        if (get_matching_parent(dev, STRV_MAKE("ccwgroup", "ccw"), /* skip_virtio= */ true, &cdev) < 0)
                return 0;

        log_device_debug(dev, "Device is CCW.");

        /* Retrieve bus-ID of the CCW device.  The bus-ID uniquely
         * identifies the network device on the Linux on System z channel
         * subsystem.  Note that the bus-ID contains lowercase characters.
         */
        r = sd_device_get_sysname(cdev, &bus_id);
        if (r < 0)
                return log_device_debug_errno(cdev, r, "Failed to get sysname: %m");

        /* Check the length of the bus-ID. Rely on the fact that the kernel provides a correct bus-ID;
         * alternatively, improve this check and parse and verify each bus-ID part...
         */
        bus_id_len = strlen(bus_id);
        if (!IN_SET(bus_id_len, 8, 9))
                return log_device_debug_errno(cdev, SYNTHETIC_ERRNO(EINVAL), "Invalid bus_id: '%s'", bus_id);

        /* Strip leading zeros from the bus id for aesthetic purposes. This
         * keeps the ccw names stable, yet much shorter in general case of
         * bus_id 0.0.0600 -> 600. This is similar to e.g. how PCI domain is
         * not prepended when it is zero. Preserve the last 0 for 0.0.0000.
         */
        bus_id_start = strspn(bus_id, ".0");
        bus_id += bus_id_start < bus_id_len ? bus_id_start : bus_id_len - 1;

        /* Use the CCW bus-ID as network device name */
        char str[ALTIFNAMSIZ];
        if (snprintf_ok(str, sizeof str, "%sc%s", prefix, bus_id))
                udev_builtin_add_property(event, "ID_NET_NAME_PATH", str);
        log_device_debug(dev, "CCW identifier: ccw_busid=%s %s \"%s\"",
                         bus_id, glyph(GLYPH_ARROW_RIGHT), str + strlen(prefix));
        return 0;
}

/* IEEE Organizationally Unique Identifier vendor string */
static int ieee_oui(UdevEvent *event, const struct hw_addr_data *hw_addr) {
        char str[32];

        assert(event);
        assert(hw_addr);

        if (hw_addr->length != 6)
                return -EOPNOTSUPP;

        /* skip commonly misused 00:00:00 (Xerox) prefix */
        if (hw_addr->bytes[0] == 0 &&
            hw_addr->bytes[1] == 0 &&
            hw_addr->bytes[2] == 0)
                return -EINVAL;

        xsprintf(str, "OUI:%02X%02X%02X%02X%02X%02X",
                 hw_addr->bytes[0],
                 hw_addr->bytes[1],
                 hw_addr->bytes[2],
                 hw_addr->bytes[3],
                 hw_addr->bytes[4],
                 hw_addr->bytes[5]);

        return udev_builtin_hwdb_lookup(event, NULL, str, NULL);
}

static int names_mac(UdevEvent *event, const char *prefix) {
        sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        unsigned iftype, assign_type;
        struct hw_addr_data hw_addr;
        const char *s;
        int r;

        assert(prefix);

        r = device_get_sysattr_unsigned_filtered(dev, "type", &iftype);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to read 'type' attribute: %m");

        /* The persistent part of a hardware address of an InfiniBand NIC is 8 bytes long. We cannot
         * fit this much in an iface name.
         * TODO: but it can be used as alternative names?? */
        if (iftype == ARPHRD_INFINIBAND)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EOPNOTSUPP),
                                              "Not generating MAC name for infiniband device.");

        /* check for NET_ADDR_PERM, skip random MAC addresses */
        r = device_get_sysattr_unsigned_filtered(dev, "addr_assign_type", &assign_type);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to read/parse addr_assign_type: %m");

        if (assign_type != NET_ADDR_PERM)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
                                              "addr_assign_type=%u, MAC address is not permanent.", assign_type);

        r = device_get_sysattr_safe_string_filtered(dev, "address", &s);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to read 'address' attribute: %m");

        r = parse_hw_addr(s, &hw_addr);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to parse 'address' attribute: %m");

        if (hw_addr.length != 6)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EOPNOTSUPP),
                                              "Not generating MAC name for device with MAC address of length %zu.",
                                              hw_addr.length);

        char str[ALTIFNAMSIZ];
        xsprintf(str, "%sx%s", prefix, HW_ADDR_TO_STR_FULL(&hw_addr, HW_ADDR_TO_STRING_NO_COLON));
        udev_builtin_add_property(event, "ID_NET_NAME_MAC", str);
        log_device_debug(dev, "MAC address identifier: hw_addr=%s %s %s",
                         HW_ADDR_TO_STR(&hw_addr),
                         glyph(GLYPH_ARROW_RIGHT), str + strlen(prefix));

        (void) ieee_oui(event, &hw_addr);
        return 0;
}

static int names_netdevsim(UdevEvent *event, const char *prefix) {
        sd_device *netdevsimdev, *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        const char *phys_port_name;
        unsigned addr;
        int r;

        assert(prefix);

        /* get netdevsim path names */

        if (!naming_scheme_has(NAMING_NETDEVSIM))
                return 0;

        r = sd_device_get_parent_with_subsystem_devtype(dev, "netdevsim", NULL, &netdevsimdev);
        if (r < 0)
                return r;

        r = device_get_sysnum_unsigned(netdevsimdev, &addr);
        if (r < 0)
                return log_device_debug_errno(netdevsimdev, r, "Failed to get device sysnum: %m");

        r = device_get_sysattr_safe_string_filtered(dev, "phys_port_name", &phys_port_name);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to get 'phys_port_name' attribute: %m");
        if (isempty(phys_port_name))
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EOPNOTSUPP),
                                              "The 'phys_port_name' attribute is empty.");

        char str[ALTIFNAMSIZ];
        if (snprintf_ok(str, sizeof str, "%si%un%s", prefix, addr, phys_port_name))
                udev_builtin_add_property(event, "ID_NET_NAME_PATH", str);
        log_device_debug(dev, "Netdevsim identifier: address=%u, port_name=%s %s %s",
                         addr, phys_port_name, glyph(GLYPH_ARROW_RIGHT), str + strlen(prefix));
        return 0;
}

static int names_xen(UdevEvent *event, const char *prefix) {
        sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        _cleanup_free_ char *vif = NULL;
        const char *p;
        unsigned id;
        int r;

        assert(prefix);

        /* get xen vif "slot" based names. */

        if (!naming_scheme_has(NAMING_XEN_VIF))
                return 0;

        /* check if our direct parent is a Xen VIF device with no other bus in-between */
        if (get_matching_parent(dev, STRV_MAKE("xen"), /* skip_virtio= */ false, NULL) < 0)
                return 0;

        /* Use the vif-n name to extract "n" */
        r = get_first_syspath_component(dev, "/sys/devices/", &vif);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to get Xen VIF name: %m");

        p = startswith(vif, "vif-");
        if (!p)
                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL), "Invalid vif name: '%s'.", vif);

        r = safe_atou_full(p, SAFE_ATO_REFUSE_PLUS_MINUS | SAFE_ATO_REFUSE_LEADING_ZERO |
                           SAFE_ATO_REFUSE_LEADING_WHITESPACE | 10, &id);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to parse vif index from '%s': %m", p);

        char str[ALTIFNAMSIZ];
        if (snprintf_ok(str, sizeof str, "%sX%u", prefix, id))
                udev_builtin_add_property(event, "ID_NET_NAME_SLOT", str);
        log_device_debug(dev, "Xen identifier: id=%u %s %s",
                         id, glyph(GLYPH_ARROW_RIGHT), str + strlen(prefix));
        return 0;
}

static int get_ifname_prefix(sd_device *dev, const char **ret) {
        unsigned iftype;
        int r;

        assert(dev);
        assert(ret);

        r = device_get_sysattr_unsigned_filtered(dev, "type", &iftype);
        if (r < 0)
                return r;

        /* handle only ARPHRD_ETHER, ARPHRD_SLIP, ARPHRD_INFINIBAND, and ARPHDR_MCTP devices */
        switch (iftype) {
        case ARPHRD_ETHER: {
                if (device_is_devtype(dev, "wlan") > 0)
                        *ret = "wl";
                else if (device_is_devtype(dev, "wwan") > 0)
                        *ret = "ww";
                else
                        *ret = "en";
                return 0;
        }
        case ARPHRD_INFINIBAND:
                if (!naming_scheme_has(NAMING_INFINIBAND))
                        return -EOPNOTSUPP;

                *ret = "ib";
                return 0;

        case ARPHRD_SLIP:
                *ret = "sl";
                return 0;

        case ARPHRD_MCTP:
                if (!naming_scheme_has(NAMING_MCTP))
                        return -EOPNOTSUPP;

                *ret = "mc";
                return 0;

        default:
                return -EOPNOTSUPP;
        }
}

static int device_is_stacked(sd_device *dev) {
        int ifindex, iflink, r;

        assert(dev);

        r = sd_device_get_ifindex(dev, &ifindex);
        if (r < 0)
                return r;

        r = device_get_sysattr_int_filtered(dev, "iflink", &iflink);
        if (r < 0)
                return r;

        return ifindex != iflink;
}

static int builtin_net_id(UdevEvent *event, int argc, char *argv[]) {
        sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
        const char *prefix;
        int r;

        /* skip stacked devices, like VLANs, ... */
        r = device_is_stacked(dev);
        if (r < 0)
                return log_device_debug_errno(dev, r, "Failed to check if the device is stacked: %m");
        if (r > 0)
                return 0;

        r = get_ifname_prefix(dev, &prefix);
        if (r < 0) {
                log_device_debug_errno(dev, r, "Failed to determine prefix for network interface naming, ignoring: %m");
                return 0;
        }

        udev_builtin_add_property(event, "ID_NET_NAMING_SCHEME", naming_scheme()->name);

        (void) names_mac(event, prefix);
        (void) names_devicetree(event, prefix);
        (void) names_ccw(event, prefix);
        (void) names_vio(event, prefix);
        (void) names_platform(event, prefix);
        (void) names_netdevsim(event, prefix);
        (void) names_xen(event, prefix);
        (void) names_pci(event, prefix);
        (void) names_usb(event, prefix);
        (void) names_bcma(event, prefix);

        return 0;
}

static int builtin_net_id_init(void) {
        /* Load naming scheme here to suppress log messages in workers. */
        naming_scheme();
        return 0;
}

const UdevBuiltin udev_builtin_net_id = {
        .name = "net_id",
        .cmd = builtin_net_id,
        .init = builtin_net_id_init,
        .help = "Network device properties",
};