SOLR-18098: Fix replication failure for files with exact MB sizes (back port to 9x)

changelog/unreleased/SOLR-18098-fix-replication-exact-mb-sizes.yml

@@ -0,0 +1,7 @@
+title: Fix replication failure for files with exact MB sizes
+type: fixed
+authors:
+  - name: Shubham Ranjan
+links:
+  - name: SOLR-18098
+    url: https://issues.apache.org/jira/browse/SOLR-18098

solr/core/src/java/org/apache/solr/handler/admin/api/ReplicationAPIBase.java

@@ -393,6 +393,13 @@ public void write(OutputStream out) throws IOException {
         while (true) {
           offset = offset == -1 ? 0 : offset;
           int read = (int) Math.min(buf.length, filelen - offset);
+
+          if (read <= 0) {
+            writeNothingAndFlush();
+            fos.close();
+            break;
+          }
+
           in.readBytes(buf, 0, read);
 
           fos.writeInt(read);