Add new error code DNS_SECURE_RESOLVER_HOSTNAME_RESOLUTION_FAILED.

This error code will be used when a DoH server hostname cannot be
resolved due to a DNS issue.

Bug: 1016325
Change-Id: Icfe5ecd2d80c3182a540340adb7858b8a0c6f88a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1906904Reviewed-by: Eric Orth <ericorth@chromium.org>
Commit-Queue: Katharine Daly <dalyk@google.com>
Cr-Commit-Position: refs/heads/master@{#714344}

net/base/net_error_list.h

@@ -965,5 +965,7 @@ NET_ERROR(DNS_SEARCH_EMPTY, -805)
 // Failed to sort addresses according to RFC3484.
 NET_ERROR(DNS_SORT_ERROR, -806)
 
-// Failed to resolve over HTTP, fallback to legacy
-NET_ERROR(DNS_HTTP_FAILED, -807)
+// Error -807 was removed (DNS_HTTP_FAILED)
+
+// Failed to resolve the hostname of a DNS-over-HTTPS server.
+NET_ERROR(DNS_SECURE_RESOLVER_HOSTNAME_RESOLUTION_FAILED, -808)

net/dns/dns_transaction.cc

@@ -432,6 +432,10 @@ class DnsHTTPAttempt : public DnsAttempt, public URLRequest::Delegate {
     DCHECK_NE(net::ERR_IO_PENDING, net_error);
     std::string content_type;
     if (net_error != OK) {
+      // Update the error code if there was an issue resolving the secure
+      // server hostname.
+      if (IsDnsError(net_error))
+        net_error = ERR_DNS_SECURE_RESOLVER_HOSTNAME_RESOLUTION_FAILED;
       ResponseCompleted(net_error);
       return;
     }

net/dns/dns_transaction_unittest.cc

@@ -1464,6 +1464,27 @@ TEST_F(DnsTransactionTest, HttpsPostLookupAsync) {
   EXPECT_TRUE(helper0.RunUntilDone(transaction_factory_.get()));
 }
 
+URLRequestJob* DohJobMakerCallbackFailLookup(URLRequest* request,
+                                             NetworkDelegate* network_delegate,
+                                             SocketDataProvider* data) {
+  URLRequestMockDohJob::MatchQueryData(request, data);
+  return new URLRequestFailedJob(request, network_delegate,
+                                 URLRequestFailedJob::START,
+                                 ERR_NAME_NOT_RESOLVED);
+}
+
+TEST_F(DnsTransactionTest, HttpsPostLookupFailDohServerLookup) {
+  ConfigureDohServers(true /* use_post */);
+  AddQueryAndResponse(0, kT0HostName, kT0Qtype, kT0ResponseDatagram,
+                      base::size(kT0ResponseDatagram), SYNCHRONOUS,
+                      Transport::HTTPS, nullptr /* opt_rdata */,
+                      DnsQuery::PaddingStrategy::BLOCK_LENGTH_128);
+  TransactionHelper helper0(kT0HostName, kT0Qtype, true /* secure */,
+                            ERR_DNS_SECURE_RESOLVER_HOSTNAME_RESOLUTION_FAILED);
+  SetDohJobMakerCallback(base::BindRepeating(DohJobMakerCallbackFailLookup));
+  EXPECT_TRUE(helper0.RunUntilDone(transaction_factory_.get()));
+}
+
 URLRequestJob* DohJobMakerCallbackFailStart(URLRequest* request,
                                             NetworkDelegate* network_delegate,
                                             SocketDataProvider* data) {