selftests/bpf: Add bpf_stale scheduler

This patch implements the setting a subflow as stale/unstale in BPF MPTCP
scheduler, named bpf_stale. The staled subflow will be added into a stale
map in sk_storage. Two helper mptcp_subflow_set_stale() and
mptcp_subflow_unstale() are added. The subflow will be set as stale in
bpf_stale_data_init() and will be checked in bpf_stale_get_subflow().

Signed-off-by: Geliang Tang <[email protected]>

tools/testing/selftests/bpf/progs/mptcp_bpf_stale.c

@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023, SUSE. */
+
+#include <linux/bpf.h>
+#include "bpf_tcp_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+struct mptcp_stale_storage {
+	__u8 nr;
+	struct mptcp_subflow_context *stale[MPTCP_SUBFLOWS_MAX];
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, struct mptcp_stale_storage);
+} mptcp_stale_map SEC(".maps");
+
+static void mptcp_subflow_set_stale(struct mptcp_stale_storage *storage,
+				    struct mptcp_subflow_context *subflow)
+{
+	for (int i = 0; i < storage->nr && i < MPTCP_SUBFLOWS_MAX; i++) {
+		if (storage->stale[i] == subflow)
+			return;
+	}
+
+	if (storage->nr < MPTCP_SUBFLOWS_MAX - 1)
+		storage->stale[storage->nr++] = subflow;
+}
+
+static void mptcp_subflow_unstale(struct mptcp_stale_storage *storage,
+				  struct mptcp_subflow_context *subflow)
+{
+	for (int i = 0; i < storage->nr && i < MPTCP_SUBFLOWS_MAX; i++) {
+		if (storage->stale[i] == subflow) {
+			for (int j = i; j < MPTCP_SUBFLOWS_MAX - 1; j++) {
+				if (!storage->stale[j + 1])
+					break;
+				storage->stale[j] = storage->stale[j + 1];
+				storage->stale[j + 1] = NULL;
+			}
+			storage->nr--;
+			return;
+		}
+	}
+}
+
+static bool mptcp_subflow_is_stale(struct mptcp_stale_storage *storage,
+				   struct mptcp_subflow_context *subflow)
+{
+	for (int i = 0; i < storage->nr && i < MPTCP_SUBFLOWS_MAX; i++) {
+		if (storage->stale[i] == subflow)
+			return true;
+	}
+
+	return false;
+}
+
+static bool mptcp_subflow_is_active(struct mptcp_sched_data *data,
+				    struct mptcp_subflow_context *stale)
+{
+	for (int i = 0; i < data->subflows && i < MPTCP_SUBFLOWS_MAX; i++) {
+		struct mptcp_subflow_context *subflow;
+
+		subflow = mptcp_subflow_ctx_by_pos(data, i);
+		if (!subflow)
+			break;
+		if (subflow == stale)
+			return true;
+	}
+
+	return false;
+}
+
+SEC("struct_ops/mptcp_sched_stale_init")
+void BPF_PROG(mptcp_sched_stale_init, struct mptcp_sock *msk)
+{
+}
+
+SEC("struct_ops/mptcp_sched_stale_release")
+void BPF_PROG(mptcp_sched_stale_release, struct mptcp_sock *msk)
+{
+}
+
+void BPF_STRUCT_OPS(bpf_stale_data_init, struct mptcp_sock *msk,
+		    struct mptcp_sched_data *data)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_stale_storage *storage;
+
+	mptcp_sched_data_set_contexts(msk, data);
+
+	storage = bpf_sk_storage_get(&mptcp_stale_map, msk, 0,
+				     BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (!storage)
+		return;
+
+	for (int i = 0; i < storage->nr && i < MPTCP_SUBFLOWS_MAX; i++) {
+		if (!mptcp_subflow_is_active(data, storage->stale[i]))
+			mptcp_subflow_unstale(storage, storage->stale[i]);
+	}
+
+	subflow = mptcp_subflow_ctx_by_pos(data, 0);
+	if (subflow) {
+		mptcp_subflow_set_stale(storage, subflow);
+		mptcp_subflow_unstale(storage, subflow);
+	}
+
+	subflow = mptcp_subflow_ctx_by_pos(data, 1);
+	if (subflow) {
+		mptcp_subflow_set_stale(storage, subflow);
+		mptcp_subflow_unstale(storage, subflow);
+		mptcp_subflow_set_stale(storage, subflow);
+	}
+}
+
+int BPF_STRUCT_OPS(bpf_stale_get_subflow, struct mptcp_sock *msk,
+		   const struct mptcp_sched_data *data)
+{
+	struct mptcp_stale_storage *storage;
+	int nr = -1;
+
+	storage = bpf_sk_storage_get(&mptcp_stale_map, msk, 0,
+				     BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (!storage)
+		return -1;
+
+	for (int i = 0; i < data->subflows && i < MPTCP_SUBFLOWS_MAX; i++) {
+		struct mptcp_subflow_context *subflow;
+
+		subflow = mptcp_subflow_ctx_by_pos(data, i);
+		if (!subflow)
+			break;
+
+		if (mptcp_subflow_is_stale(storage, subflow))
+			continue;
+
+		nr = i;
+	}
+
+	if (nr != -1)
+		mptcp_subflow_set_scheduled(mptcp_subflow_ctx_by_pos(data, nr), true);
+	return 0;
+}
+
+SEC(".struct_ops")
+struct mptcp_sched_ops stale = {
+	.init		= (void *)mptcp_sched_stale_init,
+	.release	= (void *)mptcp_sched_stale_release,
+	.data_init	= (void *)bpf_stale_data_init,
+	.get_subflow	= (void *)bpf_stale_get_subflow,
+	.name		= "bpf_stale",
+};