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Remove locking from rdataslab_getownercase()

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Under normal circumstances, the case bitfield in the slabheader should
be set only once.  By actually (soft-)enforcing this, the read locking
can be completely removed from the rdataslab_getownercase() as we can
check whether the case has been already set or not and making everything
immutable once the case has been set.
This commit is contained in:
Ondřej Surý 2025-08-12 12:10:24 +02:00
parent eba76df247
commit d0fef4d5e5
No known key found for this signature in database
GPG Key ID: 2820F37E873DEA41
1 changed files with 31 additions and 25 deletions
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56
lib/dns/rdataslab.c
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@ -18,6 +18,7 @@
#include <stdlib.h>
#include <isc/ascii.h>
#include <isc/atomic.h>
#include <isc/mem.h>
#include <isc/region.h>
#include <isc/result.h>
@ -833,36 +834,38 @@ dns_slabheader_raw(dns_slabheader_t *header) {
void
dns_slabheader_setownercase(dns_slabheader_t *header, const dns_name_t *name) {
unsigned int i;
bool fully_lower;
REQUIRE(!CASESET(header));
bool casefullylower = true;
/*
* We do not need to worry about label lengths as they are all
* less than or equal to 63.
*/
memset(header->upper, 0, sizeof(header->upper));
fully_lower = true;
for (i = 0; i < name->length; i++) {
for (size_t i = 0; i < name->length; i++) {
if (isupper(name->ndata[i])) {
header->upper[i / 8] |= 1 << (i % 8);
fully_lower = false;
casefullylower = false;
}
}
DNS_SLABHEADER_SETATTR(header, DNS_SLABHEADERATTR_CASESET);
if (fully_lower) {
if (casefullylower) {
DNS_SLABHEADER_SETATTR(header,
DNS_SLABHEADERATTR_CASEFULLYLOWER);
}
DNS_SLABHEADER_SETATTR(header, DNS_SLABHEADERATTR_CASESET);
}
void
dns_slabheader_copycase(dns_slabheader_t *dest, dns_slabheader_t *src) {
REQUIRE(!CASESET(dest));
if (CASESET(src)) {
uint_least16_t attr = DNS_SLABHEADER_GETATTR(
src, DNS_SLABHEADERATTR_CASESET |
DNS_SLABHEADERATTR_CASEFULLYLOWER);
DNS_SLABHEADER_SETATTR(dest, attr);
memmove(dest->upper, src->upper, sizeof(src->upper));
if (CASEFULLYLOWER(src)) {
DNS_SLABHEADER_SETATTR(
dest, DNS_SLABHEADERATTR_CASEFULLYLOWER);
}
DNS_SLABHEADER_SETATTR(dest, DNS_SLABHEADERATTR_CASESET);
}
}
@ -1198,7 +1201,10 @@ static void
rdataset_setownercase(dns_rdataset_t *rdataset, const dns_name_t *name) {
dns_slabheader_t *header = dns_rdataset_getheader(rdataset);
DNS_SLABHEADER_CLRATTR(header, DNS_SLABHEADERATTR_CASEFULLYLOWER);
/* The case could be set just once for the same header */
if (CASESET(header)) {
return;
}
dns_db_locknode(header->node, isc_rwlocktype_write);
dns_slabheader_setownercase(header, name);
@ -1211,26 +1217,26 @@ rdataset_getownercase(const dns_rdataset_t *rdataset, dns_name_t *name) {
uint8_t mask = (1 << 7);
uint8_t bits = 0;
if (!CASESET(header)) {
return;
}
if (CASEFULLYLOWER(header)) {
isc_ascii_lowercopy(name->ndata, name->ndata, name->length);
return;
}
dns_db_locknode(header->node, isc_rwlocktype_read);
if (CASESET(header)) {
uint8_t *nd = name->ndata;
for (size_t i = 0; i < name->length; i++) {
if (mask == (1 << 7)) {
bits = header->upper[i / 8];
mask = 1;
} else {
mask <<= 1;
}
nd[i] = (bits & mask) ? isc_ascii_toupper(nd[i])
: isc_ascii_tolower(nd[i]);
uint8_t *nd = name->ndata;
for (size_t i = 0; i < name->length; i++) {
if (mask == (1 << 7)) {
bits = header->upper[i / 8];
mask = 1;
} else {
mask <<= 1;
}
nd[i] = (bits & mask) ? isc_ascii_toupper(nd[i])
: isc_ascii_tolower(nd[i]);
}
dns_db_unlocknode(header->node, isc_rwlocktype_read);
}
static dns_slabheader_t *