diff --git a/bpf_progs/clatd.c b/bpf_progs/clatd.c
index a2214dc..6e6af26 100644
--- a/bpf_progs/clatd.c
+++ b/bpf_progs/clatd.c
@@ -38,8 +38,19 @@
 #include "bpf_shared.h"
 #include "clat_mark.h"
 
-// From kernel:include/net/ip.h
-#define IP_DF 0x4000  // Flag: "Don't Fragment"
+// IP flags. (from kernel's include/net/ip.h)
+#define IP_CE      0x8000  // Flag: "Congestion" (really reserved 'evil bit')
+#define IP_DF      0x4000  // Flag: "Don't Fragment"
+#define IP_MF      0x2000  // Flag: "More Fragments"
+#define IP_OFFSET  0x1FFF  // "Fragment Offset" part
+
+// from kernel's include/net/ipv6.h
+struct frag_hdr {
+    __u8   nexthdr;
+    __u8   reserved;        // always zero
+    __be16 frag_off;        // 13 bit offset, 2 bits zero, 1 bit "More Fragments"
+    __be32 identification;
+};
 
 DEFINE_BPF_MAP_GRW(clat_ingress6_map, HASH, ClatIngress6Key, ClatIngress6Value, 16, AID_SYSTEM)