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Convert rwlock in dns_acl to RCU

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The dns_aclenv_t contains two dns_acl_t - localhost and localnets that
can be swapped with a different ACLs as we configure BIND 9.  Instead of
protecting those two pointers with heavyweight read-write lock, use RCU
mechanism to dereference and swap the pointers.
This commit is contained in:
Ondřej Surý 2023-10-13 08:59:41 +02:00 committed by Ondřej Surý
parent 546c327349
commit 96bbf95b83
4 changed files with 65 additions and 60 deletions
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87
lib/dns/acl.c
View file

@ -19,6 +19,7 @@
#include <isc/mem.h>
#include <isc/once.h>
#include <isc/string.h>
#include <isc/urcu.h>
#include <isc/util.h>
#include <dns/acl.h>
@ -47,6 +48,7 @@ dns_acl_create(isc_mem_t *mctx, int n, dns_acl_t **target) {
};
isc_mem_attach(mctx, &acl->mctx);
dns_iptable_create(acl->mctx, &acl->iptable);
*target = acl;
}
@ -401,26 +403,18 @@ dns_aclelement_match(const isc_netaddr_t *reqaddr, const dns_name_t *reqsigner,
if (env == NULL) {
return (false);
}
RWLOCK(&env->rwlock, isc_rwlocktype_read);
if (env->localhost == NULL) {
RWUNLOCK(&env->rwlock, isc_rwlocktype_read);
return (false);
}
dns_acl_attach(env->localhost, &inner);
RWUNLOCK(&env->rwlock, isc_rwlocktype_read);
rcu_read_lock();
dns_acl_attach(rcu_dereference(env->localhost), &inner);
rcu_read_unlock();
break;
case dns_aclelementtype_localnets:
if (env == NULL) {
return (false);
}
RWLOCK(&env->rwlock, isc_rwlocktype_read);
if (env->localnets == NULL) {
RWUNLOCK(&env->rwlock, isc_rwlocktype_read);
return (false);
}
dns_acl_attach(env->localnets, &inner);
RWUNLOCK(&env->rwlock, isc_rwlocktype_read);
rcu_read_lock();
dns_acl_attach(rcu_dereference(env->localnets), &inner);
rcu_read_unlock();
break;
#if defined(HAVE_GEOIP2)
@ -652,7 +646,6 @@ dns_aclenv_create(isc_mem_t *mctx, dns_aclenv_t **envp) {
isc_mem_attach(mctx, &env->mctx);
isc_refcount_init(&env->references, 1);
isc_rwlock_init(&env->rwlock);
dns_acl_create(mctx, 0, &env->localhost);
dns_acl_create(mctx, 0, &env->localnets);
@ -663,34 +656,45 @@ dns_aclenv_create(isc_mem_t *mctx, dns_aclenv_t **envp) {
void
dns_aclenv_set(dns_aclenv_t *env, dns_acl_t *localhost, dns_acl_t *localnets) {
REQUIRE(VALID_ACLENV(env));
REQUIRE(DNS_ACL_VALID(localhost));
REQUIRE(DNS_ACL_VALID(localnets));
RWLOCK(&env->rwlock, isc_rwlocktype_write);
dns_acl_detach(&env->localhost);
dns_acl_attach(localhost, &env->localhost);
dns_acl_detach(&env->localnets);
dns_acl_attach(localnets, &env->localnets);
RWUNLOCK(&env->rwlock, isc_rwlocktype_write);
rcu_read_lock();
localhost = rcu_xchg_pointer(&env->localhost, dns_acl_ref(localhost));
localnets = rcu_xchg_pointer(&env->localnets, dns_acl_ref(localnets));
rcu_read_unlock();
dns_acl_detach(&localhost);
dns_acl_detach(&localnets);
}
void
dns_aclenv_copy(dns_aclenv_t *t, dns_aclenv_t *s) {
REQUIRE(VALID_ACLENV(s));
REQUIRE(VALID_ACLENV(t));
dns_aclenv_copy(dns_aclenv_t *target, dns_aclenv_t *source) {
REQUIRE(VALID_ACLENV(source));
REQUIRE(VALID_ACLENV(target));
RWLOCK(&t->rwlock, isc_rwlocktype_write);
RWLOCK(&s->rwlock, isc_rwlocktype_read);
dns_acl_detach(&t->localhost);
dns_acl_attach(s->localhost, &t->localhost);
dns_acl_detach(&t->localnets);
dns_acl_attach(s->localnets, &t->localnets);
rcu_read_lock();
t->match_mapped = s->match_mapped;
dns_acl_t *localhost = rcu_dereference(source->localhost);
INSIST(DNS_ACL_VALID(localhost));
dns_acl_t *localnets = rcu_dereference(source->localnets);
INSIST(DNS_ACL_VALID(localnets));
localhost = rcu_xchg_pointer(&target->localhost,
dns_acl_ref(localhost));
localnets = rcu_xchg_pointer(&target->localnets,
dns_acl_ref(localnets));
target->match_mapped = source->match_mapped;
#if defined(HAVE_GEOIP2)
t->geoip = s->geoip;
target->geoip = source->geoip;
#endif /* if defined(HAVE_GEOIP2) */
RWUNLOCK(&s->rwlock, isc_rwlocktype_read);
RWUNLOCK(&t->rwlock, isc_rwlocktype_write);
rcu_read_unlock();
dns_acl_detach(&localhost);
dns_acl_detach(&localnets);
}
static void
@ -699,10 +703,17 @@ dns__aclenv_destroy(dns_aclenv_t *aclenv) {
aclenv->magic = 0;
isc_refcount_destroy(&aclenv->references);
dns_acl_detach(&aclenv->localhost);
dns_acl_detach(&aclenv->localnets);
isc_rwlock_destroy(&aclenv->rwlock);
rcu_read_lock();
dns_acl_t *localhost = rcu_xchg_pointer(&aclenv->localhost, NULL);
INSIST(DNS_ACL_VALID(localhost));
dns_acl_t *localnets = rcu_xchg_pointer(&aclenv->localnets, NULL);
INSIST(DNS_ACL_VALID(localnets));
rcu_read_unlock();
dns_acl_detach(&localhost);
dns_acl_detach(&localnets);
isc_mem_putanddetach(&aclenv->mctx, aclenv, sizeof(*aclenv));
}

6
lib/dns/include/dns/acl.h
View file

@ -34,7 +34,6 @@
#include <isc/magic.h>
#include <isc/netaddr.h>
#include <isc/refcount.h>
#include <isc/rwlock.h>
#include <dns/geoip.h>
#include <dns/iptable.h>
@ -103,9 +102,8 @@ struct dns_aclenv {
isc_mem_t *mctx;
isc_refcount_t references;
isc_rwlock_t rwlock; /*%< Locks localhost and localnets */
dns_acl_t *localhost;
dns_acl_t *localnets;
dns_acl_t *localhost;
dns_acl_t *localnets;
bool match_mapped;
#if defined(HAVE_GEOIP2)

7
lib/dns/ssu.c
View file

@ -367,10 +367,11 @@ dns_ssutable_checkrules(dns_ssutable_t *table, const dns_name_t *signer,
if (!dns_name_issubdomain(name, rule->name)) {
continue;
}
RWLOCK(&env->rwlock, isc_rwlocktype_read);
dns_acl_match(addr, NULL, env->localhost, NULL, &match,
rcu_read_lock();
dns_acl_t *localhost = rcu_dereference(env->localhost);
dns_acl_match(addr, NULL, localhost, NULL, &match,
NULL);
RWUNLOCK(&env->rwlock, isc_rwlocktype_read);
rcu_read_unlock();
if (match == 0) {
if (signer != NULL) {
isc_log_write(dns_lctx,

25
lib/ns/sortlist.c
View file

@ -84,30 +84,25 @@ ns_sortlist_setup(dns_acl_t *acl, dns_aclenv_t *env, isc_netaddr_t *clientaddr,
}
if (order_elt->type == dns_aclelementtype_localhost) {
dns_acl_t *inner = NULL;
RWLOCK(&env->rwlock, isc_rwlocktype_read);
if (env->localhost != NULL) {
dns_acl_attach(env->localhost, &inner);
}
RWUNLOCK(&env->rwlock, isc_rwlocktype_read);
rcu_read_lock();
dns_acl_t *inner = rcu_dereference(env->localhost);
if (inner != NULL) {
*argp = inner;
*argp = dns_acl_ref(inner);
rcu_read_unlock();
return (NS_SORTLISTTYPE_2ELEMENT);
}
rcu_read_unlock();
}
if (order_elt->type == dns_aclelementtype_localnets) {
dns_acl_t *inner = NULL;
RWLOCK(&env->rwlock, isc_rwlocktype_read);
if (env->localnets != NULL) {
dns_acl_attach(env->localnets, &inner);
}
RWUNLOCK(&env->rwlock, isc_rwlocktype_read);
rcu_read_lock();
dns_acl_t *inner = rcu_dereference(env->localhost);
if (inner != NULL) {
*argp = inner;
*argp = dns_acl_ref(inner);
rcu_read_unlock();
return (NS_SORTLISTTYPE_2ELEMENT);
}
rcu_read_unlock();
}
/*