resolved: internalize string buffer of dns_resource_record_to_string()

Let's simplify usage and memory management of DnsResourceRecord's
dns_resource_record_to_string() call: cache the formatted string as
part of the object, and return it on subsequent calls, freeing it when
the DnsResourceRecord itself is freed.

7 files changed, 69 insertions, 90 deletions

diff --git a/src/resolve/resolved-dns-answer.c b/src/resolve/resolved-dns-answer.c
index 7e64ca52b7..4dea4a2d45 100644
--- a/src/resolve/resolved-dns-answer.c
+++ b/src/resolve/resolved-dns-answer.c
@@ -657,18 +657,18 @@ int dns_answer_reserve_or_clone(DnsAnswer **a, unsigned n_free) {
 void dns_answer_dump(DnsAnswer *answer, FILE *f) {
         DnsResourceRecord *rr;
         DnsAnswerFlags flags;
-        int ifindex, r;
+        int ifindex;
 
         if (!f)
                 f = stdout;
 
         DNS_ANSWER_FOREACH_FULL(rr, ifindex, flags, answer) {
-                _cleanup_free_ char *t = NULL;
+                const char *t;
 
                 fputc('\t', f);
 
-                r = dns_resource_record_to_string(rr, &t);
-                if (r < 0) {
+                t = dns_resource_record_to_string(rr);
+                if (!t) {
                         log_oom();
                         continue;
                 }
diff --git a/src/resolve/resolved-dns-cache.c b/src/resolve/resolved-dns-cache.c
index e8541d5e14..f9fe2c2e30 100644
--- a/src/resolve/resolved-dns-cache.c
+++ b/src/resolve/resolved-dns-cache.c
@@ -938,13 +938,13 @@ void dns_cache_dump(DnsCache *cache, FILE *f) {
                 DnsCacheItem *j;
 
                 LIST_FOREACH(by_key, j, i) {
-                        _cleanup_free_ char *t = NULL;
 
                         fputc('\t', f);
 
                         if (j->rr) {
-                                r = dns_resource_record_to_string(j->rr, &t);
-                                if (r < 0) {
+                                const char *t;
+                                t = dns_resource_record_to_string(j->rr);
+                                if (!t) {
                                         log_oom();
                                         continue;
                                 }
@@ -952,13 +952,14 @@ void dns_cache_dump(DnsCache *cache, FILE *f) {
                                 fputs(t, f);
                                 fputc('\n', f);
                         } else {
-                                r = dns_resource_key_to_string(j->key, &t);
+                                _cleanup_free_ char *z = NULL;
+                                r = dns_resource_key_to_string(j->key, &z);
                                 if (r < 0) {
                                         log_oom();
                                         continue;
                                 }
 
-                                fputs(t, f);
+                                fputs(z, f);
                                 fputs(" -- ", f);
                                 fputs(j->type == DNS_CACHE_NODATA ? "NODATA" : "NXDOMAIN", f);
                                 fputc('\n', f);
diff --git a/src/resolve/resolved-dns-rr.c b/src/resolve/resolved-dns-rr.c
index 067fb1cd08..04d442bf03 100644
--- a/src/resolve/resolved-dns-rr.c
+++ b/src/resolve/resolved-dns-rr.c
@@ -448,6 +448,7 @@ DnsResourceRecord* dns_resource_record_unref(DnsResourceRecord *rr) {
                 dns_resource_key_unref(rr->key);
         }
 
+        free(rr->to_string);
         free(rr);
 
         return NULL;
@@ -763,16 +764,19 @@ static char *format_txt(DnsTxtItem *first) {
         return s;
 }
 
-int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
+const char *dns_resource_record_to_string(DnsResourceRecord *rr) {
         _cleanup_free_ char *k = NULL, *t = NULL;
         char *s;
         int r;
 
         assert(rr);
 
+        if (rr->to_string)
+                return rr->to_string;
+
         r = dns_resource_key_to_string(rr->key, &k);
         if (r < 0)
-                return r;
+                return NULL;
 
         switch (rr->unparseable ? _DNS_TYPE_INVALID : rr->key->type) {
 
@@ -784,7 +788,7 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                              rr->srv.port,
                              strna(rr->srv.name));
                 if (r < 0)
-                        return -ENOMEM;
+                        return NULL;
                 break;
 
         case DNS_TYPE_PTR:
@@ -793,25 +797,25 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
         case DNS_TYPE_DNAME:
                 s = strjoin(k, " ", rr->ptr.name, NULL);
                 if (!s)
-                        return -ENOMEM;
+                        return NULL;
 
                 break;
 
         case DNS_TYPE_HINFO:
                 s = strjoin(k, " ", rr->hinfo.cpu, " ", rr->hinfo.os, NULL);
                 if (!s)
-                        return -ENOMEM;
+                        return NULL;
                 break;
 
         case DNS_TYPE_SPF: /* exactly the same as TXT */
         case DNS_TYPE_TXT:
                 t = format_txt(rr->txt.items);
                 if (!t)
-                        return -ENOMEM;
+                        return NULL;
 
                 s = strjoin(k, " ", t, NULL);
                 if (!s)
-                        return -ENOMEM;
+                        return NULL;
                 break;
 
         case DNS_TYPE_A: {
@@ -819,22 +823,22 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
 
                 r = in_addr_to_string(AF_INET, (const union in_addr_union*) &rr->a.in_addr, &x);
                 if (r < 0)
-                        return r;
+                        return NULL;
 
                 s = strjoin(k, " ", x, NULL);
                 if (!s)
-                        return -ENOMEM;
+                        return NULL;
                 break;
         }
 
         case DNS_TYPE_AAAA:
                 r = in_addr_to_string(AF_INET6, (const union in_addr_union*) &rr->aaaa.in6_addr, &t);
                 if (r < 0)
-                        return r;
+                        return NULL;
 
                 s = strjoin(k, " ", t, NULL);
                 if (!s)
-                        return -ENOMEM;
+                        return NULL;
                 break;
 
         case DNS_TYPE_SOA:
@@ -848,7 +852,7 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                              rr->soa.expire,
                              rr->soa.minimum);
                 if (r < 0)
-                        return -ENOMEM;
+                        return NULL;
                 break;
 
         case DNS_TYPE_MX:
@@ -857,7 +861,7 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                              rr->mx.priority,
                              rr->mx.exchange);
                 if (r < 0)
-                        return -ENOMEM;
+                        return NULL;
                 break;
 
         case DNS_TYPE_LOC:
@@ -870,17 +874,17 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                                     rr->loc.horiz_pre,
                                     rr->loc.vert_pre);
                 if (!t)
-                        return -ENOMEM;
+                        return NULL;
 
                 s = strjoin(k, " ", t, NULL);
                 if (!s)
-                        return -ENOMEM;
+                        return NULL;
                 break;
 
         case DNS_TYPE_DS:
                 t = hexmem(rr->ds.digest, rr->ds.digest_size);
                 if (!t)
-                        return -ENOMEM;
+                        return NULL;
 
                 r = asprintf(&s, "%s %u %u %u %s",
                              k,
@@ -889,13 +893,13 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                              rr->ds.digest_type,
                              t);
                 if (r < 0)
-                        return -ENOMEM;
+                        return NULL;
                 break;
 
         case DNS_TYPE_SSHFP:
                 t = hexmem(rr->sshfp.fingerprint, rr->sshfp.fingerprint_size);
                 if (!t)
-                        return -ENOMEM;
+                        return NULL;
 
                 r = asprintf(&s, "%s %u %u %s",
                              k,
@@ -903,7 +907,7 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                              rr->sshfp.fptype,
                              t);
                 if (r < 0)
-                        return -ENOMEM;
+                        return NULL;
                 break;
 
         case DNS_TYPE_DNSKEY: {
@@ -913,7 +917,7 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
 
                 t = base64mem(rr->dnskey.key, rr->dnskey.key_size);
                 if (!t)
-                        return -ENOMEM;
+                        return NULL;
 
                 r = asprintf(&s, "%s %u %u %.*s%.*u %s",
                              k,
@@ -923,7 +927,7 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                              alg ? 0 : 1, alg ? 0u : (unsigned) rr->dnskey.algorithm,
                              t);
                 if (r < 0)
-                        return -ENOMEM;
+                        return NULL;
                 break;
         }
 
@@ -936,15 +940,15 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
 
                 t = base64mem(rr->rrsig.signature, rr->rrsig.signature_size);
                 if (!t)
-                        return -ENOMEM;
+                        return NULL;
 
                 r = format_timestamp_dns(expiration, sizeof(expiration), rr->rrsig.expiration);
                 if (r < 0)
-                        return r;
+                        return NULL;
 
                 r = format_timestamp_dns(inception, sizeof(inception), rr->rrsig.inception);
                 if (r < 0)
-                        return r;
+                        return NULL;
 
                 /* TYPE?? follows
                  * http://tools.ietf.org/html/rfc3597#section-5 */
@@ -963,21 +967,21 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                              rr->rrsig.signer,
                              t);
                 if (r < 0)
-                        return -ENOMEM;
+                        return NULL;
                 break;
         }
 
         case DNS_TYPE_NSEC:
                 t = format_types(rr->nsec.types);
                 if (!t)
-                        return -ENOMEM;
+                        return NULL;
 
                 r = asprintf(&s, "%s %s %s",
                              k,
                              rr->nsec.next_domain_name,
                              t);
                 if (r < 0)
-                        return -ENOMEM;
+                        return NULL;
                 break;
 
         case DNS_TYPE_NSEC3: {
@@ -986,16 +990,16 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                 if (rr->nsec3.salt_size > 0) {
                         salt = hexmem(rr->nsec3.salt, rr->nsec3.salt_size);
                         if (!salt)
-                                return -ENOMEM;
+                                return NULL;
                 }
 
                 hash = base32hexmem(rr->nsec3.next_hashed_name, rr->nsec3.next_hashed_name_size, false);
                 if (!hash)
-                        return -ENOMEM;
+                        return NULL;
 
                 t = format_types(rr->nsec3.types);
                 if (!t)
-                        return -ENOMEM;
+                        return NULL;
 
                 r = asprintf(&s, "%s %"PRIu8" %"PRIu8" %"PRIu16" %s %s %s",
                              k,
@@ -1006,7 +1010,7 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                              hash,
                              t);
                 if (r < 0)
-                        return -ENOMEM;
+                        return NULL;
 
                 break;
         }
@@ -1014,16 +1018,16 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
         default:
                 t = hexmem(rr->generic.data, rr->generic.size);
                 if (!t)
-                        return -ENOMEM;
+                        return NULL;
 
                 r = asprintf(&s, "%s \\# %zu %s", k, rr->generic.size, t);
                 if (r < 0)
-                        return -ENOMEM;
+                        return NULL;
                 break;
         }
 
-        *ret = s;
-        return 0;
+        rr->to_string = s;
+        return s;
 }
 
 int dns_resource_record_to_wire_format(DnsResourceRecord *rr, bool canonical) {
diff --git a/src/resolve/resolved-dns-rr.h b/src/resolve/resolved-dns-rr.h
index a35f01ce10..f2997883a8 100644
--- a/src/resolve/resolved-dns-rr.h
+++ b/src/resolve/resolved-dns-rr.h
@@ -95,6 +95,7 @@ struct DnsTxtItem {
 struct DnsResourceRecord {
         unsigned n_ref;
         DnsResourceKey *key;
+        char *to_string;
         uint32_t ttl;
         bool unparseable:1;
         bool wire_format_canonical:1;
@@ -253,7 +254,7 @@ DnsResourceRecord* dns_resource_record_unref(DnsResourceRecord *rr);
 int dns_resource_record_new_reverse(DnsResourceRecord **ret, int family, const union in_addr_union *address, const char *name);
 int dns_resource_record_new_address(DnsResourceRecord **ret, int family, const union in_addr_union *address, const char *name);
 int dns_resource_record_equal(const DnsResourceRecord *a, const DnsResourceRecord *b);
-int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret);
+const char* dns_resource_record_to_string(DnsResourceRecord *rr);
 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsResourceRecord*, dns_resource_record_unref);
 
 int dns_resource_record_to_wire_format(DnsResourceRecord *rr, bool canonical);
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 347b1683f9..d2aec13264 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -1906,12 +1906,7 @@ int dns_transaction_validate_dnssec(DnsTransaction *t) {
                         if (r < 0)
                                 return r;
 
-                        if (log_get_max_level() >= LOG_DEBUG) {
-                                _cleanup_free_ char *rrs = NULL;
-
-                                (void) dns_resource_record_to_string(rr, &rrs);
-                                log_debug("Looking at %s: %s", rrs ? strstrip(rrs) : "???", dnssec_result_to_string(result));
-                        }
+                        log_debug("Looking at %s: %s", strna(dns_resource_record_to_string(rr)), dnssec_result_to_string(result));
 
                         if (result == DNSSEC_VALIDATED) {
 
diff --git a/src/resolve/resolved-dns-zone.c b/src/resolve/resolved-dns-zone.c
index 20c8a4da90..f60b0bddc1 100644
--- a/src/resolve/resolved-dns-zone.c
+++ b/src/resolve/resolved-dns-zone.c
@@ -471,15 +471,12 @@ return_empty:
 }
 
 void dns_zone_item_conflict(DnsZoneItem *i) {
-        _cleanup_free_ char *pretty = NULL;
-
         assert(i);
 
         if (!IN_SET(i->state, DNS_ZONE_ITEM_PROBING, DNS_ZONE_ITEM_VERIFYING, DNS_ZONE_ITEM_ESTABLISHED))
                 return;
 
-        dns_resource_record_to_string(i->rr, &pretty);
-        log_info("Detected conflict on %s", strna(pretty));
+        log_info("Detected conflict on %s", strna(dns_resource_record_to_string(i->rr)));
 
         dns_zone_item_probe_stop(i);
 
@@ -492,8 +489,6 @@ void dns_zone_item_conflict(DnsZoneItem *i) {
 }
 
 void dns_zone_item_notify(DnsZoneItem *i) {
-        _cleanup_free_ char *pretty = NULL;
-
         assert(i);
         assert(i->probe_transaction);
 
@@ -530,15 +525,13 @@ void dns_zone_item_notify(DnsZoneItem *i) {
                 log_debug("Got a successful probe reply, but peer has lexicographically lower IP address and thus lost.");
         }
 
-        dns_resource_record_to_string(i->rr, &pretty);
-        log_debug("Record %s successfully probed.", strna(pretty));
+        log_debug("Record %s successfully probed.", strna(dns_resource_record_to_string(i->rr)));
 
         dns_zone_item_probe_stop(i);
         i->state = DNS_ZONE_ITEM_ESTABLISHED;
 }
 
 static int dns_zone_item_verify(DnsZoneItem *i) {
-        _cleanup_free_ char *pretty = NULL;
         int r;
 
         assert(i);
@@ -546,8 +539,7 @@ static int dns_zone_item_verify(DnsZoneItem *i) {
         if (i->state != DNS_ZONE_ITEM_ESTABLISHED)
                 return 0;
 
-        dns_resource_record_to_string(i->rr, &pretty);
-        log_debug("Verifying RR %s", strna(pretty));
+        log_debug("Verifying RR %s", strna(dns_resource_record_to_string(i->rr)));
 
         i->state = DNS_ZONE_ITEM_VERIFYING;
         r = dns_zone_item_probe_start(i);
@@ -632,7 +624,6 @@ void dns_zone_verify_all(DnsZone *zone) {
 void dns_zone_dump(DnsZone *zone, FILE *f) {
         Iterator iterator;
         DnsZoneItem *i;
-        int r;
 
         if (!zone)
                 return;
@@ -644,10 +635,10 @@ void dns_zone_dump(DnsZone *zone, FILE *f) {
                 DnsZoneItem *j;
 
                 LIST_FOREACH(by_key, j, i) {
-                        _cleanup_free_ char *t = NULL;
+                        const char *t;
 
-                        r = dns_resource_record_to_string(j->rr, &t);
-                        if (r < 0) {
+                        t = dns_resource_record_to_string(j->rr);
+                        if (!t) {
                                 log_oom();
                                 continue;
                         }
diff --git a/src/resolve/test-dnssec.c b/src/resolve/test-dnssec.c
index 5b4ee220c4..6104d8b4c0 100644
--- a/src/resolve/test-dnssec.c
+++ b/src/resolve/test-dnssec.c
@@ -56,7 +56,6 @@ static void test_dnssec_verify_rrset2(void) {
 
         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *nsec = NULL, *rrsig = NULL, *dnskey = NULL;
         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
-        _cleanup_free_ char *x = NULL, *y = NULL, *z = NULL;
         DnssecResult result;
 
         nsec = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_NSEC, "nasa.gov");
@@ -77,8 +76,7 @@ static void test_dnssec_verify_rrset2(void) {
         assert_se(bitmap_set(nsec->nsec.types, DNS_TYPE_DNSKEY) >= 0);
         assert_se(bitmap_set(nsec->nsec.types, 65534) >= 0);
 
-        assert_se(dns_resource_record_to_string(nsec, &x) >= 0);
-        log_info("NSEC: %s", x);
+        log_info("NSEC: %s", strna(dns_resource_record_to_string(nsec)));
 
         rrsig = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_RRSIG, "NaSa.GOV.");
         assert_se(rrsig);
@@ -96,8 +94,7 @@ static void test_dnssec_verify_rrset2(void) {
         rrsig->rrsig.signature = memdup(signature_blob, rrsig->rrsig.signature_size);
         assert_se(rrsig->rrsig.signature);
 
-        assert_se(dns_resource_record_to_string(rrsig, &y) >= 0);
-        log_info("RRSIG: %s", y);
+        log_info("RRSIG: %s", strna(dns_resource_record_to_string(rrsig)));
 
         dnskey = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_DNSKEY, "nASA.gOV");
         assert_se(dnskey);
@@ -109,8 +106,7 @@ static void test_dnssec_verify_rrset2(void) {
         dnskey->dnskey.key = memdup(dnskey_blob, sizeof(dnskey_blob));
         assert_se(dnskey->dnskey.key);
 
-        assert_se(dns_resource_record_to_string(dnskey, &z) >= 0);
-        log_info("DNSKEY: %s", z);
+        log_info("DNSKEY: %s", strna(dns_resource_record_to_string(dnskey)));
         log_info("DNSKEY keytag: %u", dnssec_keytag(dnskey));
 
         assert_se(dnssec_key_match_rrsig(nsec->key, rrsig) > 0);
@@ -152,7 +148,6 @@ static void test_dnssec_verify_rrset(void) {
 
         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *a = NULL, *rrsig = NULL, *dnskey = NULL;
         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
-        _cleanup_free_ char *x = NULL, *y = NULL, *z = NULL;
         DnssecResult result;
 
         a = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_A, "nAsA.gov");
@@ -160,8 +155,7 @@ static void test_dnssec_verify_rrset(void) {
 
         a->a.in_addr.s_addr = inet_addr("52.0.14.116");
 
-        assert_se(dns_resource_record_to_string(a, &x) >= 0);
-        log_info("A: %s", x);
+        log_info("A: %s", strna(dns_resource_record_to_string(a)));
 
         rrsig = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_RRSIG, "NaSa.GOV.");
         assert_se(rrsig);
@@ -179,8 +173,7 @@ static void test_dnssec_verify_rrset(void) {
         rrsig->rrsig.signature = memdup(signature_blob, rrsig->rrsig.signature_size);
         assert_se(rrsig->rrsig.signature);
 
-        assert_se(dns_resource_record_to_string(rrsig, &y) >= 0);
-        log_info("RRSIG: %s", y);
+        log_info("RRSIG: %s", strna(dns_resource_record_to_string(rrsig)));
 
         dnskey = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_DNSKEY, "nASA.gOV");
         assert_se(dnskey);
@@ -192,8 +185,7 @@ static void test_dnssec_verify_rrset(void) {
         dnskey->dnskey.key = memdup(dnskey_blob, sizeof(dnskey_blob));
         assert_se(dnskey->dnskey.key);
 
-        assert_se(dns_resource_record_to_string(dnskey, &z) >= 0);
-        log_info("DNSKEY: %s", z);
+        log_info("DNSKEY: %s", strna(dns_resource_record_to_string(dnskey)));
         log_info("DNSKEY keytag: %u", dnssec_keytag(dnskey));
 
         assert_se(dnssec_key_match_rrsig(a->key, rrsig) > 0);
@@ -239,7 +231,6 @@ static void test_dnssec_verify_dns_key(void) {
         };
 
         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *dnskey = NULL, *ds1 = NULL, *ds2 = NULL;
-        _cleanup_free_ char *a = NULL, *b = NULL, *c = NULL;
 
         /* The two DS RRs in effect for nasa.gov on 2015-12-01. */
         ds1 = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_DS, "nasa.gov");
@@ -252,8 +243,7 @@ static void test_dnssec_verify_dns_key(void) {
         ds1->ds.digest = memdup(ds1_fprint, ds1->ds.digest_size);
         assert_se(ds1->ds.digest);
 
-        assert_se(dns_resource_record_to_string(ds1, &a) >= 0);
-        log_info("DS1: %s", a);
+        log_info("DS1: %s", strna(dns_resource_record_to_string(ds1)));
 
         ds2 = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_DS, "NASA.GOV");
         assert_se(ds2);
@@ -265,8 +255,7 @@ static void test_dnssec_verify_dns_key(void) {
         ds2->ds.digest = memdup(ds2_fprint, ds2->ds.digest_size);
         assert_se(ds2->ds.digest);
 
-        assert_se(dns_resource_record_to_string(ds2, &b) >= 0);
-        log_info("DS2: %s", b);
+        log_info("DS2: %s", strna(dns_resource_record_to_string(ds2)));
 
         dnskey = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_DNSKEY, "nasa.GOV");
         assert_se(dnskey);
@@ -278,8 +267,7 @@ static void test_dnssec_verify_dns_key(void) {
         dnskey->dnskey.key = memdup(dnskey_blob, sizeof(dnskey_blob));
         assert_se(dnskey->dnskey.key);
 
-        assert_se(dns_resource_record_to_string(dnskey, &c) >= 0);
-        log_info("DNSKEY: %s", c);
+        log_info("DNSKEY: %s", strna(dns_resource_record_to_string(dnskey)));
         log_info("DNSKEY keytag: %u", dnssec_keytag(dnskey));
 
         assert_se(dnssec_verify_dnskey(dnskey, ds1) > 0);
@@ -310,8 +298,8 @@ static void test_dnssec_nsec3_hash(void) {
         static const uint8_t salt[] = { 0xB0, 0x1D, 0xFA, 0xCE };
         static const uint8_t next_hashed_name[] = { 0x84, 0x10, 0x26, 0x53, 0xc9, 0xfa, 0x4d, 0x85, 0x6c, 0x97, 0x82, 0xe2, 0x8f, 0xdf, 0x2d, 0x5e, 0x87, 0x69, 0xc4, 0x52 };
         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
-        _cleanup_free_ char *a = NULL, *b = NULL;
         uint8_t h[DNSSEC_HASH_SIZE_MAX];
+        _cleanup_free_ char *b = NULL;
         int k;
 
         /* The NSEC3 RR for eurid.eu on 2015-12-14. */
@@ -328,8 +316,7 @@ static void test_dnssec_nsec3_hash(void) {
         assert_se(rr->nsec3.next_hashed_name);
         rr->nsec3.next_hashed_name_size = sizeof(next_hashed_name);
 
-        assert_se(dns_resource_record_to_string(rr, &a) >= 0);
-        log_info("NSEC3: %s", a);
+        log_info("NSEC3: %s", strna(dns_resource_record_to_string(rr)));
 
         k = dnssec_nsec3_hash(rr, "eurid.eu", &h);
         assert_se(k >= 0);