This patch implements the redundant BPF MPTCP scheduler, named bpf_red,
which sends all packets redundantly on all available subflows.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 .../selftests/bpf/progs/mptcp_bpf_red.c       | 54 +++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/mptcp_bpf_red.c

diff --git a/tools/testing/selftests/bpf/progs/mptcp_bpf_red.c b/tools/testing/selftests/bpf/progs/mptcp_bpf_red.c
new file mode 100644
index 000000000000..ea006a895cf1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/mptcp_bpf_red.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022, SUSE. */
+
+#include <linux/bpf.h>
+#include "bpf_tcp_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("struct_ops/mptcp_sched_red_init")
+void BPF_PROG(mptcp_sched_red_init, const struct mptcp_sock *msk)
+{
+}
+
+SEC("struct_ops/mptcp_sched_red_release")
+void BPF_PROG(mptcp_sched_red_release, const struct mptcp_sock *msk)
+{
+}
+
+void BPF_STRUCT_OPS(bpf_red_get_subflow, const struct mptcp_sock *msk,
+		    bool reinject, struct mptcp_sched_data *data)
+{
+	struct sock *ssk = data->contexts[0]->tcp_sock;
+	int i;
+
+	if (reinject) {
+		data->sock = ssk;
+		data->call_again = 0;
+		return;
+	}
+
+	for (i = 0; i < MPTCP_SUBFLOWS_MAX && i < data->subflows; i++) {
+		if (!msk->last_snd)
+			break;
+
+		if (data->contexts[i]->tcp_sock == msk->last_snd) {
+			if (i + 1 == MPTCP_SUBFLOWS_MAX || !data->contexts[i + 1])
+				break;
+
+			ssk = data->contexts[i + 1]->tcp_sock;
+			break;
+		}
+	}
+
+	data->sock = ssk;
+	data->call_again = i + 1 == data->subflows ? 0 : 1;
+}
+
+SEC(".struct_ops")
+struct mptcp_sched_ops red = {
+	.init		= (void *)mptcp_sched_red_init,
+	.release	= (void *)mptcp_sched_red_release,
+	.get_subflow	= (void *)bpf_red_get_subflow,
+	.name		= "bpf_red",
+};
-- 
2.34.1