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>
---
 .../testing/selftests/bpf/bpf_mptcp_helpers.h |  1 +
 .../selftests/bpf/progs/mptcp_bpf_red.c       | 52 +++++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/mptcp_bpf_red.c

diff --git a/tools/testing/selftests/bpf/bpf_mptcp_helpers.h b/tools/testing/selftests/bpf/bpf_mptcp_helpers.h
index 2d5109f459b4..9004947ee4e4 100644
--- a/tools/testing/selftests/bpf/bpf_mptcp_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_mptcp_helpers.h
@@ -12,6 +12,7 @@
 struct mptcp_sched_data {
 	struct sock	*sock;
 	bool		call_again;
+	__u8		subflows;
 	struct mptcp_subflow_context *contexts[MPTCP_SUBFLOWS_MAX];
 };
 
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..74c928e8154f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/mptcp_bpf_red.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022, SUSE. */
+
+#include <linux/bpf.h>
+#include "bpf_mptcp_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+char fmt[] = "ssk=%p call_again=%u";
+
+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;
+
+	for (i = 0; i < MPTCP_SUBFLOWS_MAX; i++) {
+		if (!msk->last_snd || !data->contexts[i])
+			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;
+	if (i < data->subflows - 1)
+		data->call_again = 1;
+	else
+		data->call_again = 0;
+}
+
+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