netdev - [PATCH bpf-next/net v2 2/5] selftests/bpf: Test setting and creating bpf qdisc as default qdisc

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Message-ID: <20250502201624.3663079-3-ameryhung@gmail.com>
Date: Fri,  2 May 2025 13:16:21 -0700
From: Amery Hung <ameryhung@...il.com>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org,
	alexei.starovoitov@...il.com,
	andrii@...nel.org,
	daniel@...earbox.net,
	martin.lau@...nel.org,
	xiyou.wangcong@...il.com,
	kernel-team@...a.com
Subject: [PATCH bpf-next/net v2 2/5] selftests/bpf: Test setting and creating bpf qdisc as default qdisc

First, test that bpf qdisc can be set as default qdisc. Then, attach
an mq qdisc to see if bpf qdisc can be successfully created and grafted.

The test is a sequential test as net.core.default_qdisc is global.

Signed-off-by: Amery Hung <ameryhung@...il.com>
---
 .../selftests/bpf/prog_tests/bpf_qdisc.c      | 61 +++++++++++++++++++
 .../selftests/bpf/progs/bpf_qdisc_fifo.c      |  3 +
 2 files changed, 64 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
index c9a54177c84e..a22008fd31d2 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
@@ -159,6 +159,62 @@ static void test_qdisc_attach_to_non_root(void)
 	bpf_qdisc_fifo__destroy(fifo_skel);
 }
 
+static int get_default_qdisc(char *qdisc_name)
+{
+	FILE *f;
+	int num;
+
+	f = fopen("/proc/sys/net/core/default_qdisc", "r");
+	if (!f)
+		return -errno;
+
+	num = fscanf(f, "%s", qdisc_name);
+	fclose(f);
+
+	return num == 1 ? 0 : -EFAULT;
+}
+
+static void test_default_qdisc_attach_to_mq(void)
+{
+	char default_qdisc[IFNAMSIZ] = {};
+	struct bpf_qdisc_fifo *fifo_skel;
+	struct netns_obj *netns = NULL;
+	int err;
+
+	fifo_skel = bpf_qdisc_fifo__open_and_load();
+	if (!ASSERT_OK_PTR(fifo_skel, "bpf_qdisc_fifo__open_and_load"))
+		return;
+
+	if (!ASSERT_OK(bpf_qdisc_fifo__attach(fifo_skel), "bpf_qdisc_fifo__attach"))
+		goto out;
+
+	err = get_default_qdisc(default_qdisc);
+	if (!ASSERT_OK(err, "read sysctl net.core.default_qdisc"))
+		goto out;
+
+	err = write_sysctl("/proc/sys/net/core/default_qdisc", "bpf_fifo");
+	if (!ASSERT_OK(err, "write sysctl net.core.default_qdisc"))
+		goto out;
+
+	netns = netns_new("bpf_qdisc_ns", true);
+	if (!ASSERT_OK_PTR(netns, "netns_new"))
+		goto out;
+
+	SYS(out, "ip link add veth0 type veth peer veth1");
+	SYS(out, "tc qdisc add dev veth0 root handle 1: mq");
+
+	ASSERT_EQ(fifo_skel->bss->init_called, true, "init_called");
+
+	SYS(out, "tc qdisc delete dev veth0 root mq");
+out:
+	if (netns)
+		netns_free(netns);
+	if (default_qdisc[0])
+		write_sysctl("/proc/sys/net/core/default_qdisc", default_qdisc);
+
+	bpf_qdisc_fifo__destroy(fifo_skel);
+}
+
 void test_bpf_qdisc(void)
 {
 	struct netns_obj *netns;
@@ -178,3 +234,8 @@ void test_bpf_qdisc(void)
 
 	netns_free(netns);
 }
+
+void serial_test_bpf_qdisc_default(void)
+{
+	test_default_qdisc_attach_to_mq();
+}
diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fifo.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fifo.c
index 0c7cfb82dae1..571fa7233ec0 100644
--- a/tools/testing/selftests/bpf/progs/bpf_qdisc_fifo.c
+++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fifo.c
@@ -14,6 +14,8 @@ struct skb_node {
 private(A) struct bpf_spin_lock q_fifo_lock;
 private(A) struct bpf_list_head q_fifo __contains(skb_node, node);
 
+bool init_called;
+
 SEC("struct_ops/bpf_fifo_enqueue")
 int BPF_PROG(bpf_fifo_enqueue, struct sk_buff *skb, struct Qdisc *sch,
 	     struct bpf_sk_buff_ptr *to_free)
@@ -77,6 +79,7 @@ int BPF_PROG(bpf_fifo_init, struct Qdisc *sch, struct nlattr *opt,
 	     struct netlink_ext_ack *extack)
 {
 	sch->limit = 1000;
+	init_called = true;
 	return 0;
 }
 
-- 
2.47.1