[net/dns] If the only name server is 0.0.0.0:53 assume DnsConfig is invalid.

net/dns/dns_config_service_posix_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <resolv.h>
 
 #include "base/sys_byteorder.h"
 #include "net/dns/dns_config_service_posix.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 104 matching lines @@
   ASSERT_TRUE(internal::ConvertResStateToDnsConfig(res, &config));
   CloseResState(&res);
   EXPECT_TRUE(config.IsValid());
 
   DnsConfig expected_config;
   EXPECT_FALSE(expected_config.EqualsIgnoreHosts(config));
   InitializeExpectedConfig(&expected_config);
   EXPECT_TRUE(expected_config.EqualsIgnoreHosts(config));
 }
 
+TEST(DnsConfigServicePosixTest, RejectDefaultNameserver) {
+  struct __res_state res = {};
+  res.options = RES_INIT;
+  const char kDnsrch[] = "chromium.org";
+  memcpy(res.defdname, kDnsrch, sizeof(kDnsrch));
+  res.dnsrch[0] = res.defdname;
+
+  struct sockaddr_in sa = {};
+  sa.sin_family = AF_INET;
+  sa.sin_port = base::HostToNet16(NS_DEFAULTPORT);
+  sa.sin_addr.s_addr = INADDR_ANY;
+  res.nsaddr_list[0] = sa;
+  res.nscount = 1;
+
+  DnsConfig config;
+  EXPECT_FALSE(internal::ConvertResStateToDnsConfig(res, &config));
+
+  sa.sin_addr.s_addr = 0xDEADBEEF;
+  res.nsaddr_list[0] = sa;
+  EXPECT_TRUE(internal::ConvertResStateToDnsConfig(res, &config));
+}
+
 }  // namespace
 }  // namespace net