--- zzzz-none-000/linux-4.4.271/net/ipv6/netfilter/nf_conntrack_reasm.c	2021-06-03 06:22:09.000000000 +0000
+++ hawkeye-5590-750/linux-4.4.271/net/ipv6/netfilter/nf_conntrack_reasm.c	2023-04-19 10:22:30.000000000 +0000
@@ -576,6 +576,23 @@
 	hdr = ipv6_hdr(clone);
 	fhdr = (struct frag_hdr *)skb_transport_header(clone);
 
+#if IS_ENABLED(CONFIG_NF_IPV6_DUMMY_HEADER)
+	/*
+	 * Revoke dummy header removal by IPv6 reassembly code.
+	 *
+	 * Fragment header with MF and fragment offset field as 0, is a
+	 * dummy fragment header.
+	 *
+	 * MAP-T's RFC mandates CE to add the dummy header in packets and
+	 * adds its identification in its ID field. This field should be
+	 * conserved and delivered to BR, which uses it to identify the
+	 * particular CE.
+	 */
+	if (unlikely((fhdr->frag_off & htons(IP6_OFFSET | IP6_MF)) == 0)) {
+		goto ret_orig;
+	}
+#endif
+
 	if (clone->len - skb_network_offset(clone) < IPV6_MIN_MTU &&
 	    fhdr->frag_off & htons(IP6_MF))
 		goto ret_orig;