udev: fix slot based network names on s390

The s390 PCI driver assigns the hotplug slot name from the
function_id attribute of the PCI device using a 8 char hexadecimal
format to match the underlying firmware/hypervisor notation.

Further, there's always a one-to-one mapping between a PCI
function and a hotplug slot, as individual functions can
hot plugged even for multi-function devices.

As the generic matching code will always try to parse the slot
name in /sys/bus/pci/slots as a positive decimal number, either
a wrong value might be produced for ID_NET_NAME_SLOT if
the slot name consists of decimal numbers only, or none at all
if a character in the range from 'a' to 'f' is encountered.

Additionally, the generic code assumes that two interfaces
share a hotplug slot, if they differ only in the function part
of the PCI address. E.g., for an interface with the PCI address
dddd:bb:aa.f, it will match the device to the first slot with
an address dddd:bb:aa. As more than one slot may have this address
for the s390 PCI driver, the wrong slot may be selected.

To resolve this we're adding a new naming schema version with the
flag NAMING_SLOT_FUNCTION_ID, which enables the correct matching
of hotplug slots if the device has an attribute named function_id.
The ID_NET_NAME_SLOT property will only be produced if there's
a file /sys/bus/pci/slots/<slotname> where <slotname> matches
the value of /sys/bus/pci/devices/.../function_id in 8 char
hex notation.

Fixes #19016
See also #19078

1 files changed, 10 insertions, 0 deletions

diff --git a/man/systemd.net-naming-scheme.xml b/man/systemd.net-naming-scheme.xml
index 646dd3e561..fe044d236a 100644
--- a/man/systemd.net-naming-scheme.xml
+++ b/man/systemd.net-naming-scheme.xml
@@ -369,6 +369,16 @@
           property.</para></listitem>
         </varlistentry>
 
+        <varlistentry>
+          <term><constant>v249</constant></term>
+
+          <listitem><para>PCI hotplug slot names for the s390 PCI driver are a hexadecimal representation
+          of the <filename>function_id</filename> device attribute. This attribute is now used to build the
+          <varname>ID_NET_NAME_SLOT</varname>. Before that, all slot names were parsed as decimal
+          numbers, which could either result in an incorrect value of the <varname>ID_NET_NAME_SLOT</varname>
+          property or none at all.</para></listitem>
+        </varlistentry>
+
       </variablelist>
 
     <para>Note that <constant>latest</constant> may be used to denote the latest scheme known (to this