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Merge branch '2777-use-minimal-sized-caches-for-non-recursive-views' into 'main'

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Use minimal-sized caches for non-recursive views

Closes #2777

See merge request isc-projects/bind9!5189
This commit is contained in:
Michał Kępień 2021-06-22 13:31:03 +00:00
commit 48256df57c
3 changed files with 48 additions and 0 deletions
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5
CHANGES
View file

@ -1,3 +1,8 @@
5662. [bug] Views with recursion disabled are now configured with a
default cache size of 2 MB, unless "max-cache-size" is
explicitly set. This prevents cache RBT hash tables from
being needlessly preallocated for such views. [GL #2777]
5661. [bug] A deadlock was introduced when fixing [GL #1875] because
when locking the key file mutex for each zone structure
that is in a different view, "in-view" logic was not

1
bin/named/config.c
View file

@ -263,6 +263,7 @@ view \"_bind\" chaos {\n\
recursion no;\n\
notify no;\n\
allow-new-zones no;\n\
max-cache-size 2M;\n\
\n\
# Prevent use of this zone in DNS amplified reflection DoS attacks\n\
rate-limit {\n\

42
bin/named/server.c
View file

@ -3971,6 +3971,42 @@ register_one_plugin(const cfg_obj_t *config, const cfg_obj_t *obj,
return (result);
}
/*
* Determine if a minimal-sized cache can be used for a given view, according
* to 'maps' (implicit defaults, global options, view options) and 'optionmaps'
* (global options, view options). This is only allowed for views which have
* recursion disabled and do not have "max-cache-size" set explicitly. Using
* minimal-sized caches prevents a situation in which all explicitly configured
* and built-in views inherit the default "max-cache-size 90%;" setting, which
* could lead to memory exhaustion with multiple views configured.
*/
static bool
minimal_cache_allowed(const cfg_obj_t *maps[4],
const cfg_obj_t *optionmaps[3]) {
const cfg_obj_t *obj;
/*
* Do not use a minimal-sized cache for a view with recursion enabled.
*/
obj = NULL;
(void)named_config_get(maps, "recursion", &obj);
INSIST(obj != NULL);
if (cfg_obj_asboolean(obj)) {
return (false);
}
/*
* Do not use a minimal-sized cache if a specific size was requested.
*/
obj = NULL;
(void)named_config_get(optionmaps, "max-cache-size", &obj);
if (obj != NULL) {
return (false);
}
return (true);
}
/*
* Configure 'view' according to 'vconfig', taking defaults from
* 'config' where values are missing in 'vconfig'.
@ -4236,6 +4272,12 @@ configure_view(dns_view_t *view, dns_viewlist_t *viewlist, cfg_obj_t *config,
*/
if (named_g_maxcachesize != 0) {
max_cache_size = named_g_maxcachesize;
} else if (minimal_cache_allowed(maps, optionmaps)) {
/*
* dns_cache_setcachesize() will adjust this to the smallest
* allowed value.
*/
max_cache_size = 1;
} else if (cfg_obj_isstring(obj)) {
str = cfg_obj_asstring(obj);
INSIST(strcasecmp(str, "unlimited") == 0);