1 files changed, 43 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/sockopt_qos_to_cc.c b/tools/testing/selftests/bpf/progs/sockopt_qos_to_cc.c
new file mode 100644
index 000000000000..5c3614333b01
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/sockopt_qos_to_cc.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include "bpf_tracing_net.h"
+
+char _license[] SEC("license") = "GPL";
+
+__s32 page_size = 0;
+
+const char cc_reno[TCP_CA_NAME_MAX] = "reno";
+const char cc_cubic[TCP_CA_NAME_MAX] = "cubic";
+
+SEC("cgroup/setsockopt")
+int sockopt_qos_to_cc(struct bpf_sockopt *ctx)
+{
+	void *optval_end = ctx->optval_end;
+	int *optval = ctx->optval;
+	char buf[TCP_CA_NAME_MAX];
+
+	if (ctx->level != SOL_IPV6 || ctx->optname != IPV6_TCLASS)
+		goto out;
+
+	if (optval + 1 > optval_end)
+		return 0; /* EPERM, bounds check */
+
+	if (bpf_getsockopt(ctx->sk, SOL_TCP, TCP_CONGESTION, &buf, sizeof(buf)))
+		return 0;
+
+	if (bpf_strncmp(buf, sizeof(buf), cc_cubic))
+		return 0;
+
+	if (*optval == 0x2d) {
+		if (bpf_setsockopt(ctx->sk, SOL_TCP, TCP_CONGESTION, (void *)&cc_reno,
+				sizeof(cc_reno)))
+			return 0;
+	}
+	return 1;
+
+out:
+	/* optval larger than PAGE_SIZE use kernel's buffer. */
+	if (ctx->optlen > page_size)
+		ctx->optlen = 0;
+	return 1;
+}