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lib/util: add generate_unique_u64() helper function

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Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
This commit is contained in:
Stefan Metzmacher 2020-06-09 16:19:50 +02:00 committed by Volker Lendecke
parent cd5a2d015b
commit c25fb103ea
2 changed files with 51 additions and 1 deletions
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23
lib/util/genrand_util.c
View File

@ -47,7 +47,30 @@ _PUBLIC_ uint64_t generate_random_u64(void)
return BVAL(v, 0);
}
static struct generate_unique_u64_state {
uint64_t next_value;
int pid;
} generate_unique_u64_state;
_PUBLIC_ uint64_t generate_unique_u64(uint64_t veto_value)
{
int pid = getpid();
if (unlikely(pid != generate_unique_u64_state.pid)) {
generate_unique_u64_state = (struct generate_unique_u64_state) {
.pid = pid,
.next_value = veto_value,
};
}
while (unlikely(generate_unique_u64_state.next_value == veto_value)) {
generate_nonce_buffer(
(void *)&generate_unique_u64_state.next_value,
sizeof(generate_unique_u64_state.next_value));
}
return generate_unique_u64_state.next_value++;
}
/**
Microsoft composed the following rules (among others) for quality

29
lib/util/samba_util.h
View File

@ -94,10 +94,37 @@ _PUBLIC_ int sys_getnameinfo(const struct sockaddr *psa,
_PUBLIC_ uint32_t generate_random(void);
/**
generate a single random uint64_t
* generate a single random uint64_t
* @see generate_unique_u64
**/
_PUBLIC_ uint64_t generate_random_u64(void);
/**
* @brief Generate random nonces usable for re-use detection.
*
* We have a lot of places which require a unique id that can
* be used as a unique identitier for caching states.
*
* Always using generate_nonce_buffer() has it's performance costs,
* it's typically much better than generate_random_buffer(), but
* still it's overhead we want to avoid in performance critical
* workloads.
*
* We call generate_nonce_buffer() just once per given state
* and process.
*
* This is much lighter than generate_random_u64() and it's
* designed for performance critical code paths.
*
* @veto_value It is garanteed that the return value if different from
* the veto_value.
*
* @return a unique value per given state and process
*
* @see generate_random_u64
*/
uint64_t generate_unique_u64(uint64_t veto_value);
/**
very basic password quality checker
**/