Add IPV4 Range Filtering for Backblaze B2 API Integration

Author: AnthonyRoss

extensions/data-transfer/portability-data-transfer-backblaze/src/main/java/org/datatransferproject/datatransfer/backblaze/common/BackblazeDataTransferClientFactory.java

@@ -49,7 +49,13 @@ public BackblazeDataTransferClient getOrCreateB2Client( UUID jobId,
                       SIZE_THRESHOLD_FOR_MULTIPART_UPLOAD,
                       PART_SIZE_FOR_MULTIPART_UPLOAD);
       String exportService = JobMetadata.getExportService();
-      backblazeDataTransferClient.init(authData.getToken(), authData.getSecret(), exportService, HttpClientBuilder.create().build());
+      CustomIPv4DnsResolver customDnsResolver = new CustomIPv4DnsResolver();
+      backblazeDataTransferClient.init(
+              authData.getToken(),
+              authData.getSecret(),
+              exportService,
+              HttpClientBuilder.create().setDnsResolver(customDnsResolver).build()
+      );
       backblazeDataTransferClientMap.put(jobId, backblazeDataTransferClient);
     }
     return backblazeDataTransferClientMap.get(jobId);

extensions/data-transfer/portability-data-transfer-backblaze/src/main/java/org/datatransferproject/datatransfer/backblaze/common/CustomIPv4DnsResolver.java

@@ -0,0 +1,22 @@
+package org.datatransferproject.datatransfer.backblaze.common;
+
+import org.apache.http.impl.conn.SystemDefaultDnsResolver;
+import org.apache.http.conn.DnsResolver;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.Arrays;
+
+// This class is only required because Backblaze only supports IPV4 on the B2 Native APIs, the S3
+// compatible APIs support IPV6. This can be deleted when all B2 API endpoints support IPV6.
+public class CustomIPv4DnsResolver implements DnsResolver {
+    private final SystemDefaultDnsResolver systemDefaultDnsResolver = new SystemDefaultDnsResolver();
+
+    @Override
+    public InetAddress[] resolve(String host) throws UnknownHostException {
+        // Filter to return only IPv4 addresses
+        return Arrays.stream(systemDefaultDnsResolver.resolve(host))
+                .filter(inetAddress -> inetAddress.getAddress().length == 4)
+                .toArray(InetAddress[]::new);
+    }
+}
+