diff --git a/21-xdp/.gitignore b/21-xdp/.gitignore
new file mode 100644
index 0000000..bbee7c8
--- /dev/null
+++ b/21-xdp/.gitignore
@@ -0,0 +1,10 @@
+.vscode
+package.json
+*.wasm
+ewasm-skel.h
+ecli
+ewasm
+*.o
+*.skel.json
+*.skel.yaml
+package.yaml
diff --git a/21-xdp/xdp.bpf.c b/21-xdp/xdp.bpf.c
new file mode 100644
index 0000000..a27e475
--- /dev/null
+++ b/21-xdp/xdp.bpf.c
@@ -0,0 +1,17 @@
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+/// @ifindex 1
+/// @flags 0
+/// @xdpopts {"old_prog_fd":0}
+SEC("xdp")
+int xdp_pass(struct xdp_md* ctx) {
+    void* data = (void*)(long)ctx->data;
+    void* data_end = (void*)(long)ctx->data_end;
+    int pkt_sz = data_end - data;
+
+    bpf_printk("packet size is %d", pkt_sz);
+    return XDP_PASS;
+}
+
+char __license[] SEC("license") = "GPL";
\ No newline at end of file