c-ares
diff --git a/‎src/lib/ares_qcache.c
+5-3 b/‎src/lib/ares_qcache.c
+5-3
diff --git a/‎src/lib/ares_send.c
+5-1 b/‎src/lib/ares_send.c
+5-1
diff --git a/‎src/lib/str/ares__buf.c
+5-1 b/‎src/lib/str/ares__buf.c
+5-1
diff --git a/‎test/ares-test-internal.cc
+1-1 b/‎test/ares-test-internal.cc
+1-1
diff --git a/‎test/ares-test-mock.cc
+22 b/‎test/ares-test-mock.cc
+22
@@ -121,9 +121,11 @@ static char *ares__qcache_calc_key(const ares_dns_record_t *dnsrec)
       name_len--;
     }
 
-    status = ares__buf_append(buf, (const unsigned char *)name, name_len);
-    if (status != ARES_SUCCESS) {
-      goto fail; /* LCOV_EXCL_LINE: OutOfMemory */
+    if (name_len > 0) {
+      status = ares__buf_append(buf, (const unsigned char *)name, name_len);
+      if (status != ARES_SUCCESS) {
+        goto fail; /* LCOV_EXCL_LINE: OutOfMemory */
+      }
     }
   }
 
 
@@ -62,7 +62,11 @@ static ares_status_t ares_apply_dns0x20(ares_channel_t    *channel,
   }
 
   len = ares_strlen(name);
-  if (len == 0 || len >= sizeof(dns0x20name)) {
+  if (len == 0) {
+    return ARES_SUCCESS;
+  }
+
+  if (len >= sizeof(dns0x20name)) {
     status = ARES_EBADNAME;
     goto done;
   }
 
@@ -213,10 +213,14 @@ ares_status_t ares__buf_append(ares__buf_t *buf, const unsigned char *data,
 {
   ares_status_t status;
 
-  if (data == NULL || data_len == 0) {
+  if (data == NULL && data_len != 0) {
     return ARES_EFORMERR;
   }
 
+  if (data_len == 0) {
+    return ARES_SUCCESS;
+  }
+
   status = ares__buf_ensure_space(buf, data_len);
   if (status != ARES_SUCCESS) {
     return status;
 
@@ -1021,7 +1021,7 @@ TEST_F(LibraryTest, ArrayMisuse) {
 TEST_F(LibraryTest, BufMisuse) {
   EXPECT_EQ(NULL, ares__buf_create_const(NULL, 0));
   ares__buf_reclaim(NULL);
-  EXPECT_NE(ARES_SUCCESS, ares__buf_append(NULL, NULL, 0));
+  EXPECT_NE(ARES_SUCCESS, ares__buf_append(NULL, NULL, 55));
   size_t len = 10;
   EXPECT_EQ(NULL, ares__buf_append_start(NULL, &len));
   EXPECT_EQ(NULL, ares__buf_append_start(NULL, NULL));
 
@@ -817,6 +817,28 @@ TEST_P(MockChannelTest, SearchDomains) {
   EXPECT_EQ("{'www.third.gov' aliases=[] addrs=[2.3.4.5]}", ss.str());
 }
 
+// Issue #858
+TEST_P(CacheQueriesTest, BlankName) {
+  DNSPacket rsp;
+  rsp.set_response().set_aa()
+    .add_question(new DNSQuestion(".", T_SOA))
+    .add_answer(new DNSSoaRR(".", 600, "a.root-servers.net", "nstld.verisign-grs.com", 123456, 3600, 3600, 3600, 3600));
+  EXPECT_CALL(server_, OnRequest("", T_SOA))
+    .WillOnce(SetReply(&server_, &rsp));
+
+  QueryResult result;
+  ares_query_dnsrec(channel_, ".", ARES_CLASS_IN, ARES_REC_TYPE_SOA, QueryCallback, &result, NULL);
+  Process();
+  EXPECT_TRUE(result.done_);
+  EXPECT_EQ(0, result.timeouts_);
+
+  QueryResult cacheresult;
+  ares_query_dnsrec(channel_, ".", ARES_CLASS_IN, ARES_REC_TYPE_SOA, QueryCallback, &cacheresult, NULL);
+  Process();
+  EXPECT_TRUE(cacheresult.done_);
+  EXPECT_EQ(0, cacheresult.timeouts_);
+}
+
 // Relies on retries so is UDP-only
 TEST_P(MockUDPChannelTest, SearchDomainsWithResentReply) {
   DNSPacket nofirst;
Original file line number	Diff line number	Diff line change
`@@ -121,9 +121,11 @@ static char ares__qcache_calc_key(const ares_dns_record_t dnsrec)`
`121`	`121`	`name_len--;`
`122`	`122`	`}`
`123`	`123`
`124`		`- status = ares__buf_append(buf, (const unsigned char *)name, name_len);`
`125`		`- if (status != ARES_SUCCESS) {`
`126`		`- goto fail; /* LCOV_EXCL_LINE: OutOfMemory */`
	`124`	`+ if (name_len > 0) {`
	`125`	`+ status = ares__buf_append(buf, (const unsigned char *)name, name_len);`
	`126`	`+ if (status != ARES_SUCCESS) {`
	`127`	`+ goto fail; /* LCOV_EXCL_LINE: OutOfMemory */`
	`128`	`+ }`
`127`	`129`	`}`
`128`	`130`	`}`
`129`	`131`
Original file line number	Diff line number	Diff line change
`@@ -62,7 +62,11 @@ static ares_status_t ares_apply_dns0x20(ares_channel_t *channel,`
`62`	`62`	`}`
`63`	`63`
`64`	`64`	`len = ares_strlen(name);`
`65`		`- if (len == 0 \|\| len >= sizeof(dns0x20name)) {`
	`65`	`+ if (len == 0) {`
	`66`	`+ return ARES_SUCCESS;`
	`67`	`+ }`
	`68`	`+`
	`69`	`+ if (len >= sizeof(dns0x20name)) {`
`66`	`70`	`status = ARES_EBADNAME;`
`67`	`71`	`goto done;`
`68`	`72`	`}`
Original file line number	Diff line number	Diff line change
`@@ -213,10 +213,14 @@ ares_status_t ares__buf_append(ares__buf_t buf, const unsigned char data,`
`213`	`213`	`{`
`214`	`214`	`ares_status_t status;`
`215`	`215`
`216`		`- if (data == NULL \|\| data_len == 0) {`
	`216`	`+ if (data == NULL && data_len != 0) {`
`217`	`217`	`return ARES_EFORMERR;`
`218`	`218`	`}`
`219`	`219`
	`220`	`+ if (data_len == 0) {`
	`221`	`+ return ARES_SUCCESS;`
	`222`	`+ }`
	`223`	`+`
`220`	`224`	`status = ares__buf_ensure_space(buf, data_len);`
`221`	`225`	`if (status != ARES_SUCCESS) {`
`222`	`226`	`return status;`