selftests/bpf: Add bpf_bkup scheduler & test

This patch implements the backup flag test scheduler, named bpf_bkup,
which picks the first non-backup subflow to send data.

Using MPTCP_SCHED_TEST macro to add a new test for this bpf_bkup
scheduler, the arguments "1 0" means data has been only sent on the
first subflow ADDR1. Run this test by RUN_MPTCP_TEST macro.

Signed-off-by: Geliang Tang <[email protected]>
Reviewed-by: Mat Martineau <[email protected]>
Reviewed-by: Matthieu Baerts (NGI0) <[email protected]>

Author: Geliang Tang

tools/testing/selftests/bpf/prog_tests/mptcp.c

@@ -13,6 +13,7 @@
 #include "mptcp_subflow.skel.h"
 #include "mptcp_bpf_iters.skel.h"
 #include "mptcp_bpf_first.skel.h"
+#include "mptcp_bpf_bkup.skel.h"
 
 #define NS_TEST "mptcp_ns"
 #define ADDR_1	"10.0.1.1"
@@ -683,6 +684,18 @@ static void test_first(void)
 	mptcp_bpf_first__destroy(skel);
 }
 
+static void test_bkup(void)
+{
+	struct mptcp_bpf_bkup *skel;
+
+	skel = mptcp_bpf_bkup__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "open_and_load: bkup"))
+		return;
+
+	test_bpf_sched(skel->obj, "bkup", WITH_DATA, WITHOUT_DATA);
+	mptcp_bpf_bkup__destroy(skel);
+}
+
 void test_mptcp(void)
 {
 	if (test__start_subtest("base"))
@@ -697,4 +710,6 @@ void test_mptcp(void)
 		test_default();
 	if (test__start_subtest("first"))
 		test_first();
+	if (test__start_subtest("bkup"))
+		test_bkup();
 }

tools/testing/selftests/bpf/progs/mptcp_bpf.h

@@ -4,6 +4,9 @@
 
 #include "bpf_experimental.h"
 
+/* mptcp helpers from include/net/mptcp.h */
+#define MPTCP_SUBFLOWS_MAX 8
+
 /* list helpers from include/linux/list.h */
 static inline int list_is_head(const struct list_head *list,
 			       const struct list_head *head)

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

@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022, SUSE. */
+
+#include "mptcp_bpf.h"
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("struct_ops")
+void BPF_PROG(mptcp_sched_bkup_init, struct mptcp_sock *msk)
+{
+}
+
+SEC("struct_ops")
+void BPF_PROG(mptcp_sched_bkup_release, struct mptcp_sock *msk)
+{
+}
+
+SEC("struct_ops")
+int BPF_PROG(bpf_bkup_get_subflow, struct mptcp_sock *msk,
+	     struct mptcp_sched_data *data)
+{
+	int nr = -1;
+
+	for (int i = 0; i < data->subflows && i < MPTCP_SUBFLOWS_MAX; i++) {
+		struct mptcp_subflow_context *subflow;
+
+		subflow = bpf_mptcp_subflow_ctx_by_pos(data, i);
+		if (!subflow)
+			break;
+
+		if (!BPF_CORE_READ_BITFIELD_PROBED(subflow, backup) ||
+		    !BPF_CORE_READ_BITFIELD_PROBED(subflow, request_bkup)) {
+			nr = i;
+			break;
+		}
+	}
+
+	if (nr != -1) {
+		mptcp_subflow_set_scheduled(bpf_mptcp_subflow_ctx_by_pos(data, nr), true);
+		return -1;
+	}
+	return 0;
+}
+
+SEC(".struct_ops")
+struct mptcp_sched_ops bkup = {
+	.init		= (void *)mptcp_sched_bkup_init,
+	.release	= (void *)mptcp_sched_bkup_release,
+	.get_subflow	= (void *)bpf_bkup_get_subflow,
+	.name		= "bpf_bkup",
+};