1 files changed, 42 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_update_frags.c b/tools/testing/selftests/bpf/progs/test_xdp_update_frags.c
new file mode 100644
index 000000000000..2a3496d8e327
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_xdp_update_frags.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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.
+ */
+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <bpf/bpf_helpers.h>
+
+int _version SEC("version") = 1;
+
+SEC("xdp.frags")
+int xdp_adjust_frags(struct xdp_md *xdp)
+{
+	__u8 *data_end = (void *)(long)xdp->data_end;
+	__u8 *data = (void *)(long)xdp->data;
+	__u8 val[16] = {};
+	__u32 offset;
+	int err;
+
+	if (data + sizeof(__u32) > data_end)
+		return XDP_DROP;
+
+	offset = *(__u32 *)data;
+	err = bpf_xdp_load_bytes(xdp, offset, val, sizeof(val));
+	if (err < 0)
+		return XDP_DROP;
+
+	if (val[0] != 0xaa || val[15] != 0xaa) /* marker */
+		return XDP_DROP;
+
+	val[0] = 0xbb; /* update the marker */
+	val[15] = 0xbb;
+	err = bpf_xdp_store_bytes(xdp, offset, val, sizeof(val));
+	if (err < 0)
+		return XDP_DROP;
+
+	return XDP_PASS;
+}
+
+char _license[] SEC("license") = "GPL";