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

src/shared/netif-naming-scheme.c

@@ -13,6 +13,7 @@ static const NamingScheme naming_schemes[] = {
         { "v243", NAMING_V243 },
         { "v245", NAMING_V245 },
         { "v247", NAMING_V247 },
+        { "v249", NAMING_V249 },
         /* … add more schemes here, as the logic to name devices is updated … */
 };
 

src/shared/netif-naming-scheme.h

@@ -32,6 +32,7 @@ typedef enum NamingSchemeFlags {
         NAMING_LABEL_NOPREFIX      = 1 << 7, /* Don't prepend ID_NET_LABEL_ONBOARD with interface type prefix */
         NAMING_NSPAWN_LONG_HASH    = 1 << 8, /* Shorten nspawn interfaces by including 24bit hash, instead of simple truncation  */
         NAMING_BRIDGE_NO_SLOT      = 1 << 9, /* Don't use PCI hotplug slot information if the corresponding device is a PCI bridge */
+        NAMING_SLOT_FUNCTION_ID    = 1 << 10, /* Use function_id if present to identify PCI hotplug slots */
 
         /* And now the masks that combine the features above */
         NAMING_V238 = 0,
@@ -41,6 +42,7 @@ typedef enum NamingSchemeFlags {
         NAMING_V243 = NAMING_V241 | NAMING_NETDEVSIM | NAMING_LABEL_NOPREFIX,
         NAMING_V245 = NAMING_V243 | NAMING_NSPAWN_LONG_HASH,
         NAMING_V247 = NAMING_V245 | NAMING_BRIDGE_NO_SLOT,
+        NAMING_V249 = NAMING_V247 | NAMING_SLOT_FUNCTION_ID,
 
         _NAMING_SCHEME_FLAGS_INVALID = -EINVAL,
 } NamingSchemeFlags;