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Lower the minimum value for MaxMemInQueues to 64 MB for relays.

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For clients, there is no minimum value; in both cases, we warn if
the value seems too low.

Closes ticket 24308.
This commit is contained in:
Nick Mathewson 2020-08-11 17:01:49 -04:00
parent 431dcc42e0
commit a02002dc99
2 changed files with 27 additions and 4 deletions
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6
changes/ticket24308 Normal file
View File

@ -0,0 +1,6 @@
o Minor features (denial-of-service memory limiter):
- Allow the user to configure even lower values for the MaxMemInQueues
parameter. Relays now enforce a minimum of 64 MB, when previously
the minimum was 256 MB. On clients, there is no minimum. Relays and
clients will both warn if the value is set so low that Tor is likely
to stop working. Closes ticket 24308.

25
src/app/config/config.c
View File

@ -4585,6 +4585,9 @@ options_validate(or_options_t *old_options, or_options_t *options,
STATIC uint64_t
compute_real_max_mem_in_queues(const uint64_t val, bool is_server)
{
#define MIN_SERVER_MB 64
#define MIN_UNWARNED_SERVER_MB 256
#define MIN_UNWARNED_CLIENT_MB 64
uint64_t result;
if (val == 0) {
@ -4650,10 +4653,24 @@ compute_real_max_mem_in_queues(const uint64_t val, bool is_server)
notice_sent = 1;
}
return result;
} else if (val < ONE_GIGABYTE / 4) {
log_warn(LD_CONFIG, "MaxMemInQueues must be at least 256 MB for now. "
"Ideally, have it as large as you can afford.");
return ONE_GIGABYTE / 4;
} else if (is_server && val < ONE_MEGABYTE * MIN_SERVER_MB) {
/* We can't configure less than this much on a server. */
log_warn(LD_CONFIG, "MaxMemInQueues must be at least %d MB on servers "
"for now. Ideally, have it as large as you can afford.",
MIN_SERVER_MB);
return MIN_SERVER_MB * ONE_MEGABYTE;
} else if (is_server && val < ONE_MEGABYTE * MIN_UNWARNED_SERVER_MB) {
/* On a server, if it's less than this much, we warn that things
* may go badly. */
log_warn(LD_CONFIG, "MaxMemInQueues is set to a low value; if your "
"relay doesn't work, this may be the reason why.");
return val;
} else if (! is_server && val < ONE_MEGABYTE * MIN_UNWARNED_CLIENT_MB) {
/* On a client, if it's less than this much, we warn that things
* may go badly. */
log_warn(LD_CONFIG, "MaxMemInQueues is set to a low value; if your "
"client doesn't work, this may be the reason why.");
return val;
} else {
/* The value was fine all along */
return val;