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dns-rr: invalidate wire format after changing ttl

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dns_resource_record_clamp_ttl() may patch the TTL in place when the
record has a single reference. dnssec_fix_rrset_ttl() also updates TTLs
after canonical wire-format data may have been cached.

If a record already has cached wire-format data, that cache still
contains the old TTL and dns_resource_record_to_wire_format() will keep
reusing it.

Add a small helper to clear the cached wire-format state, and use it
whenever the TTL changes. This makes subsequent serialization match the
record fields.

Signed-off-by: dongshengyuan <dongshengyuan@uniontech.com>
(cherry picked from commit ccae5c7a4f)
(cherry picked from commit b82a9f9f53)
(cherry picked from commit 03e94e2650)
This commit is contained in:
dongshengyuan
2026-07-09 08:35:03 +08:00
committed by Luca Boccassi
parent ec26a4dd29
commit 1d410b0dc9
4 changed files with 28 additions and 1 deletions
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7
src/resolve/resolved-dns-dnssec.c
View File

@@ -551,7 +551,12 @@ static void dnssec_fix_rrset_ttl(
/* Pick the TTL as the minimum of the RR's TTL, the
* RR's original TTL according to the RRSIG and the
* RRSIG's own TTL, see RFC 4035, Section 5.3.3 */
rr->ttl = MIN3(rr->ttl, rrsig->rrsig.original_ttl, rrsig->ttl);
uint32_t ttl = MIN3(rr->ttl, rrsig->rrsig.original_ttl, rrsig->ttl);
if (ttl != rr->ttl) {
rr->ttl = ttl;
dns_resource_record_clear_wire_format(rr);
}
rr->expiry = rrsig->rrsig.expiration * USEC_PER_SEC;
/* Copy over information about the signer and wildcard source of synthesis */

11
src/resolve/test-dns-rr.c
View File

@@ -2449,18 +2449,29 @@ TEST(dns_resource_record_is_synthetic) {
* ================================================================ */
TEST(dns_resource_record_clamp_ttl_in_place) {
_cleanup_free_ void *wire_format = NULL;
DnsResourceRecord *rr = NULL, *orig = NULL;
size_t wire_format_size;
rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_A, "www.example.com");
ASSERT_NOT_NULL(rr);
orig = rr;
rr->ttl = 3600;
rr->a.in_addr.s_addr = htobe32(0xc0a8017f);
ASSERT_FALSE(dns_resource_record_clamp_ttl(&rr, 4800));
ASSERT_EQ(rr->ttl, 3600u);
ASSERT_OK(dns_resource_record_to_wire_format(rr, false));
ASSERT_NOT_NULL(rr->wire_format);
wire_format_size = rr->wire_format_size;
ASSERT_NOT_NULL(wire_format = memdup(rr->wire_format, wire_format_size));
ASSERT_TRUE(dns_resource_record_clamp_ttl(&rr, 2400));
ASSERT_EQ(rr->ttl, 2400u);
ASSERT_OK(dns_resource_record_to_wire_format(rr, false));
ASSERT_EQ(rr->wire_format_size, wire_format_size);
ASSERT_NE(memcmp(rr->wire_format, wire_format, wire_format_size), 0);
ASSERT_TRUE(rr == orig);

10
src/shared/dns-rr.c
View File

@@ -1467,6 +1467,15 @@ int dns_resource_record_to_wire_format(DnsResourceRecord *rr, bool canonical) {
return 0;
}
void dns_resource_record_clear_wire_format(DnsResourceRecord *rr) {
assert(rr);
rr->wire_format = mfree(rr->wire_format);
rr->wire_format_size = 0;
rr->wire_format_rdata_offset = 0;
rr->wire_format_canonical = false;
}
int dns_resource_record_signer(DnsResourceRecord *rr, const char **ret) {
const char *n;
int r;
@@ -1978,6 +1987,7 @@ int dns_resource_record_clamp_ttl(DnsResourceRecord **rr, uint32_t max_ttl) {
if (old_rr->n_ref == 1) {
/* Patch in place */
old_rr->ttl = new_ttl;
dns_resource_record_clear_wire_format(old_rr);
return 1;
}

1
src/shared/dns-rr.h
View File

@@ -394,6 +394,7 @@ const char* dns_resource_record_to_string(DnsResourceRecord *rr);
DnsResourceRecord *dns_resource_record_copy(DnsResourceRecord *rr);
DEFINE_TRIVIAL_CLEANUP_FUNC(DnsResourceRecord*, dns_resource_record_unref);
void dns_resource_record_clear_wire_format(DnsResourceRecord *rr);
int dns_resource_record_to_wire_format(DnsResourceRecord *rr, bool canonical);
int dns_resource_record_signer(DnsResourceRecord *rr, const char **ret);