Interface Naming broken in 2345 Stable

[goochjj]

When 2345 was installed this morning, all my network renaming rules stopped working.

This is in the release notes, and broke it coreos/bugs#1767

My link file is pretty simple:
[Match]
MacAddress=....

[Link]
Name=srv0

This worked in previous stables releases of coreos and flatcar.

My server was in-place upgraded to flatcar per your documentation.

Upon running
SYSTEMD_LOG_LEVEL=debug udevadm test-builtin net_setup_link /sys/class/net/ens192

It indicates the default naming scheme is v238 - this naming scheme IMPLICITLY has the NamePolicy "keep" behavior applied. The keep option isn't available until v240 - BEFORE v240 it is ALWAYS applied even if you try to clear it. So what happens is in the initrd, eth0 gets renamed to ens192, and then when non-initrd systemd picks it up, it won't rename something that the "userspace" has already renamed. Ever.

I had to add this
set linux_append="net.naming-scheme=latest"
to my /usr/share/oem/grub.cfg to fix it. After boot, the interfaces are renamed properly, and udevadm shows it's using v240.

If there's a more permanent fix to this, or this needs to be documented, or re-changed, or the coreos to flatcar upgrade process needs another step... I don't know. Please investigate.

[pothos]

Hello,
thanks for reporting!
In /usr/lib/systemd/network/99-default.link we set NamePolicy=keep kernel database onboard slot path as default for all links. According to the docs for Name, NamePolicy always takes precedence so I tried to unset it but without success (I tried both unsetting it for all links as directly below Name). I guess it is a bug in the old naming scheme behavior. Switching to the new one seems the correct way to fix this problem in the next release.

[goochjj]

Yeah I saw that, but masking 99-default.link didn't help. The docs also seem to indicate that if an earlier lexical file matches (i.e. 20-ens192.link), and that file DOESN'T have a NamePolicy defined, then the NamePolicy is blank. I also tried explicitly setting NamePolicy= in my 20-ens192.link file but it didn't help.

I had to dig into the code of systemd.

For detail:

SYSTEMD_LOG_LEVEL=debug udevadm test-builtin net_setup_link /sys/class/net/ens192

Config file /etc/systemd/network/20-ens192.link applies to device ens192
link_config: autonegotiation is unset or enabled, the speed and duplex are not writable.
ens192: Device has name_assign_type=4
Using default interface naming scheme 'v238'.
ens192: Device already has a name given by userspace, not renaming.
ID_NET_LINK_FILE=/etc/systemd/network/20-ens192.link

Led me to this code in v244:
https://fossies.org/linux/systemd/src/udev/net/link-config.c

  396         if (IN_SET(name_type, NET_NAME_USER, NET_NAME_RENAMED)
  397             && !naming_scheme_has(NAMING_ALLOW_RERENAMES)) {
  398                 log_device_debug(device, "Device already has a name given by userspace, not renaming.");
  399                 goto no_rename;
  400         }

I didn't trace it back further - it seemed pretty clear to me at that point that if the naming scheme came up as v238, upon further digging I'd probably find that RERENAMES aren't allowed.

[goochjj]

Just for confirmation:
https://github.com/hramrach/systemd-1/blob/master/src/udev/net/naming-scheme.h

typedef enum NamingSchemeFlags {
        /* First, the individual features */
        NAMING_SR_IOV_V            = 1 << 0, /* Use "v" suffix for SR-IOV, see 609948c7043a */
        NAMING_NPAR_ARI            = 1 << 1, /* Use NPAR "ARI", see 6bc04997b6ea */
        NAMING_INFINIBAND          = 1 << 2, /* Use "ib" prefix for infiniband, see 938d30aa98df */
        NAMING_ZERO_ACPI_INDEX     = 1 << 3, /* Use zero acpi_index field, see d81186ef4f6a */
        NAMING_ALLOW_RERENAMES     = 1 << 4, /* Allow re-renaming of devices, see #9006 */
        NAMING_STABLE_VIRTUAL_MACS = 1 << 5, /* Use device name to generate MAC, see 6d3646406560 */
        NAMING_NETDEVSIM           = 1 << 6, /* Generate names for netdevsim devices, see eaa9d507d855 */
        NAMING_LABEL_NOPREFIX      = 1 << 7, /* Don't prepend ID_NET_LABEL_ONBOARD with interface type prefix */

        /* And now the masks that combine the features above */
        NAMING_V238 = 0,
        NAMING_V239 = NAMING_V238 | NAMING_SR_IOV_V | NAMING_NPAR_ARI,
        NAMING_V240 = NAMING_V239 | NAMING_INFINIBAND | NAMING_ZERO_ACPI_INDEX | NAMING_ALLOW_RERENAMES,
        NAMING_V241 = NAMING_V240 | NAMING_STABLE_VIRTUAL_MACS,
        NAMING_V243 = NAMING_V241 | NAMING_NETDEVSIM | NAMING_LABEL_NOPREFIX,

        _NAMING_SCHEME_FLAGS_INVALID = -1,
} NamingSchemeFlags;

The NamePolicy setup will work with scheme v240 or newer.

[pothos]

Good, thanks for the details!

[pothos]

The change will land in the next release but has some other possible side effects where in few cases the persistent name will change slightly. Also a persistent name will be used where there was no one available before.

[dongsupark]

Stable 2345.3.1 was just released, so this issue should be fixed.
If you still see the issue, feel free to reopen it.
Thanks.