1 files changed, 114 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c b/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c
new file mode 100644
index 000000000000..dc6e43bc6a62
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* This logic is lifted from a real-world use case of packet parsing, used in
+ * the open source library katran, a layer 4 load balancer.
+ *
+ * This test demonstrates how to parse packet contents using dynptrs. The
+ * original code (parsing without dynptrs) can be found in test_parse_tcp_hdr_opt.c
+ */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <linux/tcp.h>
+#include <stdbool.h>
+#include <linux/ipv6.h>
+#include <linux/if_ether.h>
+#include "test_tcp_hdr_options.h"
+#include "bpf_kfuncs.h"
+
+char _license[] SEC("license") = "GPL";
+
+/* Kind number used for experiments */
+const __u32 tcp_hdr_opt_kind_tpr = 0xFD;
+/* Length of the tcp header option */
+const __u32 tcp_hdr_opt_len_tpr = 6;
+/* maximum number of header options to check to lookup server_id */
+const __u32 tcp_hdr_opt_max_opt_checks = 15;
+
+__u32 server_id;
+
+static int parse_hdr_opt(struct bpf_dynptr *ptr, __u32 *off, __u8 *hdr_bytes_remaining,
+			 __u32 *server_id)
+{
+	__u8 kind, hdr_len;
+	__u8 buffer[sizeof(kind) + sizeof(hdr_len) + sizeof(*server_id)];
+	__u8 *data;
+
+	__builtin_memset(buffer, 0, sizeof(buffer));
+
+	data = bpf_dynptr_slice(ptr, *off, buffer, sizeof(buffer));
+	if (!data)
+		return -1;
+
+	kind = data[0];
+
+	if (kind == TCPOPT_EOL)
+		return -1;
+
+	if (kind == TCPOPT_NOP) {
+		*off += 1;
+		*hdr_bytes_remaining -= 1;
+		return 0;
+	}
+
+	if (*hdr_bytes_remaining < 2)
+		return -1;
+
+	hdr_len = data[1];
+	if (hdr_len > *hdr_bytes_remaining)
+		return -1;
+
+	if (kind == tcp_hdr_opt_kind_tpr) {
+		if (hdr_len != tcp_hdr_opt_len_tpr)
+			return -1;
+
+		__builtin_memcpy(server_id, (__u32 *)(data + 2), sizeof(*server_id));
+		return 1;
+	}
+
+	*off += hdr_len;
+	*hdr_bytes_remaining -= hdr_len;
+	return 0;
+}
+
+SEC("xdp")
+int xdp_ingress_v6(struct xdp_md *xdp)
+{
+	__u8 buffer[sizeof(struct tcphdr)] = {};
+	__u8 hdr_bytes_remaining;
+	struct tcphdr *tcp_hdr;
+	__u8 tcp_hdr_opt_len;
+	int err = 0;
+	__u32 off;
+
+	struct bpf_dynptr ptr;
+
+	bpf_dynptr_from_xdp(xdp, 0, &ptr);
+
+	off = sizeof(struct ethhdr) + sizeof(struct ipv6hdr);
+
+	tcp_hdr = bpf_dynptr_slice(&ptr, off, buffer, sizeof(buffer));
+	if (!tcp_hdr)
+		return XDP_DROP;
+
+	tcp_hdr_opt_len = (tcp_hdr->doff * 4) - sizeof(struct tcphdr);
+	if (tcp_hdr_opt_len < tcp_hdr_opt_len_tpr)
+		return XDP_DROP;
+
+	hdr_bytes_remaining = tcp_hdr_opt_len;
+
+	off += sizeof(struct tcphdr);
+
+	/* max number of bytes of options in tcp header is 40 bytes */
+	for (int i = 0; i < tcp_hdr_opt_max_opt_checks; i++) {
+		err = parse_hdr_opt(&ptr, &off, &hdr_bytes_remaining, &server_id);
+
+		if (err || !hdr_bytes_remaining)
+			break;
+	}
+
+	if (!server_id)
+		return XDP_DROP;
+
+	return XDP_PASS;
+}