udevd: Add ReceivePacketSteeringCPUMask for systemd.link

Takes a list of CPU indices or ranges separated by either whitespace or commas. Alternatively,
takes the special value "all" in which will include all available CPUs in the mask.
CPU ranges are specified by the lower and upper CPU indices separated by a dash (e.g. "2-6").
This option may be specified more than once, in which case the specified CPU affinity masks are merged.
If an empty string is assigned, the mask is reset, all assignments prior to this will have no effect.
Defaults to unset and RPS CPU list is unchanged. To disable RPS when it was previously enabled, use the
special value "disable".

Currently, this will set CPU mask to all `rx` queue of matched device (if it has multiple queues).

The `/sys/class/net/<dev>/queues/rx-<n>/rps_cpus` only accept cpu bitmap mask in hexadecimal.

Fix: #30323

src/shared/cpu-set-util.h

@@ -19,11 +19,15 @@ static inline void cpu_set_reset(CPUSet *a) {
         *a = (CPUSet) {};
 }
 
+CPUSet* cpu_set_free(CPUSet *c);
+DEFINE_TRIVIAL_CLEANUP_FUNC(CPUSet*, cpu_set_free);
+
 int cpu_set_add_all(CPUSet *a, const CPUSet *b);
 int cpu_set_add(CPUSet *a, unsigned cpu);
 
 char* cpu_set_to_string(const CPUSet *a);
 char *cpu_set_to_range_string(const CPUSet *a);
+char* cpu_set_to_mask_string(const CPUSet *a);
 int cpu_set_realloc(CPUSet *cpu_set, unsigned ncpus);
 
 int parse_cpu_set_full(
@@ -50,3 +54,4 @@ int cpu_set_to_dbus(const CPUSet *set, uint8_t **ret, size_t *allocated);
 int cpu_set_from_dbus(const uint8_t *bits, size_t size, CPUSet *set);
 
 int cpus_in_affinity_mask(void);
+int cpu_mask_add_all(CPUSet *mask);