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

[Amery Hung <ameryhung@xxxxxxxxx>]

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@xxxxxxxxx>
---
 .../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