netdev - [PATCH bpf-next/net v1 2/5] selftests/bpf: Test setting and creating bpf qdisc as default qdisc

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Message-ID: <20250501223025.569020-3-ameryhung@gmail.com>
Date: Thu,  1 May 2025 15:30:22 -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 v1 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      | 78 +++++++++++++++++++
 1 file changed, 78 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..c954cc2ae64f 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
@@ -159,6 +159,79 @@ 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)
+{
+	struct bpf_qdisc_fifo *fifo_skel;
+	char default_qdisc[IFNAMSIZ];
+	struct netns_obj *netns;
+	char tc_qdisc_show[64];
+	struct bpf_link *link;
+	char *str_ret;
+	FILE *tc;
+	int err;
+
+	fifo_skel = bpf_qdisc_fifo__open_and_load();
+	if (!ASSERT_OK_PTR(fifo_skel, "bpf_qdisc_fifo__open_and_load"))
+		return;
+
+	link = bpf_map__attach_struct_ops(fifo_skel->maps.fifo);
+	if (!ASSERT_OK_PTR(link, "bpf_map__attach_struct_ops")) {
+		bpf_qdisc_fifo__destroy(fifo_skel);
+		return;
+	}
+
+	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_restore_dflt_qdisc, "ip link add veth0 type veth peer veth1");
+	SYS(out_delete_netns, "tc qdisc add dev veth0 root handle 1: mq");
+
+	tc = popen("tc qdisc show dev veth0 parent 1:1", "r");
+	if (!ASSERT_OK_PTR(tc, "tc qdisc show dev veth0 parent 1:1"))
+		goto out_delete_netns;
+
+	str_ret = fgets(tc_qdisc_show, sizeof(tc_qdisc_show), tc);
+	if (!ASSERT_OK_PTR(str_ret, "tc qdisc show dev veth0 parent 1:1"))
+		goto out_delete_netns;
+
+	str_ret = strstr(tc_qdisc_show, "qdisc bpf_fifo");
+	if (!ASSERT_OK_PTR(str_ret, "check if bpf_fifo is created"))
+		goto out_delete_netns;
+
+	SYS(out_delete_netns, "tc qdisc delete dev veth0 root mq");
+out_delete_netns:
+	netns_free(netns);
+out_restore_dflt_qdisc:
+	write_sysctl("/proc/sys/net/core/default_qdisc", default_qdisc);
+out:
+	bpf_link__destroy(link);
+	bpf_qdisc_fifo__destroy(fifo_skel);
+}
+
 void test_bpf_qdisc(void)
 {
 	struct netns_obj *netns;
@@ -178,3 +251,8 @@ void test_bpf_qdisc(void)
 
 	netns_free(netns);
 }
+
+void serial_test_bpf_qdisc_default(void)
+{
+	test_default_qdisc_attach_to_mq();
+}
-- 
2.47.1