v4.19.13 snapshot.
diff --git a/samples/bpf/parse_ldabs.c b/samples/bpf/parse_ldabs.c
new file mode 100644
index 0000000..6db6b21
--- /dev/null
+++ b/samples/bpf/parse_ldabs.c
@@ -0,0 +1,42 @@
+/* Copyright (c) 2016 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#define KBUILD_MODNAME "foo"
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/in.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <uapi/linux/bpf.h>
+#include "bpf_helpers.h"
+
+#define DEFAULT_PKTGEN_UDP_PORT 9
+#define IP_MF 0x2000
+#define IP_OFFSET 0x1FFF
+
+static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff)
+{
+ return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off))
+ & (IP_MF | IP_OFFSET);
+}
+
+SEC("ldabs")
+int handle_ingress(struct __sk_buff *skb)
+{
+ __u64 troff = ETH_HLEN + sizeof(struct iphdr);
+
+ if (load_half(skb, offsetof(struct ethhdr, h_proto)) != ETH_P_IP)
+ return 0;
+ if (load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)) != IPPROTO_UDP ||
+ load_byte(skb, ETH_HLEN) != 0x45)
+ return 0;
+ if (ip_is_fragment(skb, ETH_HLEN))
+ return 0;
+ if (load_half(skb, troff + offsetof(struct udphdr, dest)) == DEFAULT_PKTGEN_UDP_PORT)
+ return TC_ACT_SHOT;
+ return 0;
+}
+char _license[] SEC("license") = "GPL";