feat: Use configured DNS name to lookup instance IP address

build.sh

@@ -41,8 +41,12 @@ function test() {
   if [[ "$(uname -s)" == "Darwin" ]]; then
     echo "macOS detected. Setting up IP aliases for tests."
     echo "You may be prompted for your password to run sudo."
-    sudo ifconfig lo0 alias 127.0.0.2 up
-    sudo ifconfig lo0 alias 127.0.0.3 up
+    if ! ifconfig lo0 | grep -q 127.0.0.2 ; then
+      sudo ifconfig lo0 alias 127.0.0.2 up
+    fi
+    if ! ifconfig lo0 | grep -q 127.0.0.3 ; then
+      sudo ifconfig lo0 alias 127.0.0.3 up
+    fi
   fi
   $mvn_cmd -P coverage test
 }
@@ -93,7 +97,7 @@ function write_e2e_env(){
   secret_vars=(
     MYSQL_CONNECTION_NAME=MYSQL_CONNECTION_NAME
     MYSQL_USER=MYSQL_USER
-    MYSQL_USER_IAM=MYSQL_USER_IAM_GO
+    IMPERSONATED_USER=IMPERSONATED_USER
     MYSQL_PASS=MYSQL_PASS
     MYSQL_DB=MYSQL_DB
     MYSQL_MCP_CONNECTION_NAME=MYSQL_MCP_CONNECTION_NAME
@@ -107,8 +111,8 @@ function write_e2e_env(){
     POSTGRES_CAS_PASS=POSTGRES_CAS_PASS
     POSTGRES_CUSTOMER_CAS_CONNECTION_NAME=POSTGRES_CUSTOMER_CAS_CONNECTION_NAME
     POSTGRES_CUSTOMER_CAS_PASS=POSTGRES_CUSTOMER_CAS_PASS
-    POSTGRES_CUSTOMER_CAS_DOMAIN_NAME=POSTGRES_CUSTOMER_CAS_DOMAIN_NAME
-    POSTGRES_CUSTOMER_CAS_INVALID_DOMAIN_NAME=POSTGRES_CUSTOMER_CAS_INVALID_DOMAIN_NAME
+    POSTGRES_CUSTOMER_CAS_PASS_VALID_DOMAIN_NAME=POSTGRES_CUSTOMER_CAS_DOMAIN_NAME
+    POSTGRES_CUSTOMER_CAS_PASS_INVALID_DOMAIN_NAME=POSTGRES_CUSTOMER_CAS_INVALID_DOMAIN_NAME
     POSTGRES_MCP_CONNECTION_NAME=POSTGRES_MCP_CONNECTION_NAME
     POSTGRES_MCP_PASS=POSTGRES_MCP_PASS
     SQLSERVER_CONNECTION_NAME=SQLSERVER_CONNECTION_NAME
@@ -133,6 +137,10 @@ function write_e2e_env(){
     val=$(gcloud secrets versions access latest --project "$TEST_PROJECT" --secret="$secret_name")
     echo "export $env_var_name='$val'"
   done
+
+  echo "export MYSQL_IAM_USER='$(whoami)'"
+  echo "export POSTGRES_IAM_USER='$(whoami)@google.com'"
+
   } > "$outfile"
 
 }

core/src/main/java/com/google/cloud/sql/core/Connector.java

@@ -24,9 +24,12 @@
 import com.google.common.util.concurrent.ListeningScheduledExecutorService;
 import java.io.File;
 import java.io.IOException;
+import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.Socket;
+import java.net.UnknownHostException;
 import java.security.KeyPair;
+import java.util.List;
 import java.util.Timer;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
@@ -52,6 +55,7 @@ class Connector {
   private final ConnectorConfig config;
 
   private final InstanceConnectionNameResolver instanceNameResolver;
+  private final DnsResolver dnsResolver;
   private final Timer instanceNameResolverTimer;
   private final ProtocolHandler mdxProtocolHandler;
 
@@ -65,9 +69,9 @@ class Connector {
       long refreshTimeoutMs,
       int serverProxyPort,
       InstanceConnectionNameResolver instanceNameResolver,
+      DnsResolver dnsResolver,
       ProtocolHandler mdxProtocolHandler) {
     this.config = config;
-
     this.adminApi =
         connectionInfoRepositoryFactory.create(instanceCredentialFactory.create(), config);
     this.instanceCredentialFactory = instanceCredentialFactory;
@@ -76,6 +80,7 @@ class Connector {
     this.minRefreshDelayMs = minRefreshDelayMs;
     this.serverProxyPort = serverProxyPort;
     this.instanceNameResolver = instanceNameResolver;
+    this.dnsResolver = dnsResolver;
     this.instanceNameResolverTimer = new Timer("InstanceNameResolverTimer", true);
     this.mdxProtocolHandler = mdxProtocolHandler;
   }
@@ -125,6 +130,40 @@ Socket connect(ConnectionConfig config, long timeoutMs) throws IOException {
     try {
       ConnectionMetadata metadata = instance.getConnectionMetadata(timeoutMs);
       String instanceIp = metadata.getPreferredIpAddress();
+
+      // If a domain name was used to connect, resolve it to an IP address
+      if (!Strings.isNullOrEmpty(instance.getConfig().getDomainName())) {
+        try {
+          List<InetAddress> addrs = dnsResolver.resolveHost(instance.getConfig().getDomainName());
+          if (addrs != null && !addrs.isEmpty()) {
+            logger.debug(
+                String.format(
+                    "[%s] custom DNS name %s resolved to %s, using it to connect",
+                    instance.getConfig().getCloudSqlInstance(),
+                    instance.getConfig().getDomainName(),
+                    addrs.get(0).getHostAddress()));
+            instanceIp = addrs.get(0).getHostAddress();
+          } else {
+            logger.debug(
+                String.format(
+                    "[%s] custom DNS name %s resolved but returned no entries, using %s from"
+                        + " instance metadata",
+                    instance.getConfig().getCloudSqlInstance(),
+                    instance.getConfig().getDomainName(),
+                    instanceIp));
+          }
+        } catch (UnknownHostException e) {
+          logger.debug(
+              String.format(
+                  "[%s] custom DNS name %s did not resolve to an IP address: %s, using %s from"
+                      + " instance metadata",
+                  instance.getConfig().getCloudSqlInstance(),
+                  instance.getConfig().getDomainName(),
+                  e.getMessage(),
+                  instanceIp));
+        }
+      }
+
       logger.debug(String.format("[%s] Connecting to instance.", instanceIp));
 
       SSLSocket socket = (SSLSocket) metadata.getSslContext().getSocketFactory().createSocket();

core/src/main/java/com/google/cloud/sql/core/DnsJavaResolver.java

@@ -16,11 +16,15 @@
 
 package com.google.cloud.sql.core;
 
+import java.net.InetAddress;
 import java.net.UnknownHostException;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
 import java.util.stream.Collectors;
 import javax.naming.NameNotFoundException;
+import org.xbill.DNS.ARecord;
 import org.xbill.DNS.Lookup;
 import org.xbill.DNS.Record;
 import org.xbill.DNS.SimpleResolver;
@@ -105,4 +109,44 @@ public Collection<String> resolveTxt(String domainName) throws NameNotFoundExcep
       throw new RuntimeException("Invalid domain name format: " + domainName, e);
     }
   }
+
+  /**
+   * Resolve an A record.
+   *
+   * @param hostName the hostname to look up
+   * @return the resolved IP addresses
+   * @throws UnknownHostException if no records are found.
+   */
+  @Override
+  public List<InetAddress> resolveHost(String hostName) throws UnknownHostException {
+    try {
+      Lookup lookup = new Lookup(hostName, Type.A);
+      if (this.resolver != null) {
+        lookup.setResolver(this.resolver);
+      }
+      lookup.run();
+
+      int resultCode = lookup.getResult();
+      if (resultCode == Lookup.HOST_NOT_FOUND) {
+        throw new UnknownHostException("DNS record not found for " + hostName);
+      }
+      if (resultCode != Lookup.SUCCESSFUL) {
+        throw new UnknownHostException(
+            "DNS lookup failed for " + hostName + ": " + lookup.getErrorString());
+      }
+
+      Record[] records = lookup.getAnswers();
+      if (records == null || records.length == 0) {
+        return Collections.emptyList();
+      }
+
+      return Arrays.stream(records)
+          .map(r -> (ARecord) r)
+          .map(ARecord::getAddress)
+          .collect(Collectors.toList());
+
+    } catch (TextParseException e) {
+      throw new UnknownHostException("Invalid domain name format: " + hostName);
+    }
+  }
 }

core/src/main/java/com/google/cloud/sql/core/DnsResolver.java

@@ -16,10 +16,15 @@
 
 package com.google.cloud.sql.core;
 
+import java.net.InetAddress;
+import java.net.UnknownHostException;
 import java.util.Collection;
+import java.util.List;
 import javax.naming.NameNotFoundException;
 
 /** Wraps the Java DNS API. */
 interface DnsResolver {
   Collection<String> resolveTxt(String domainName) throws NameNotFoundException;
+
+  List<InetAddress> resolveHost(String hostName) throws UnknownHostException;
 }

core/src/main/java/com/google/cloud/sql/core/InternalConnectorRegistry.java

@@ -339,6 +339,7 @@ private Connector createConnector(ConnectorConfig config) {
         connectTimeoutMs,
         serverProxyPort,
         new DnsInstanceConnectionNameResolver(new DnsJavaResolver()),
+        new DnsJavaResolver(),
         this.mdxProtocolHandler);
   }