--- zzzz-none-000/linux-5.4.213/net/ipv6/netfilter/nf_conntrack_reasm.c	2022-09-15 10:04:56.000000000 +0000
+++ alder-5690pro-762/linux-5.4.213/net/ipv6/netfilter/nf_conntrack_reasm.c	2024-08-14 09:02:13.000000000 +0000
@@ -461,6 +461,24 @@
 	hdr = ipv6_hdr(skb);
 	fhdr = (struct frag_hdr *)skb_transport_header(skb);
 
+#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)) {
+		/* TODO: Should we return 0 or something else?*/
+		return 0;
+	}
+#endif
+
 	skb_orphan(skb);
 	fq = fq_find(net, fhdr->identification, user, hdr,
 		     skb->dev ? skb->dev->ifindex : 0);