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Message-ID: <83c8f387-c4a9-4293-9996-fec285d34c94@linux.dev>
Date: Thu, 1 May 2025 16:58:09 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Amery Hung <ameryhung@...il.com>
Cc: bpf@...r.kernel.org, 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: Re: [PATCH bpf-next/net v1 2/5] selftests/bpf: Test setting and
creating bpf qdisc as default qdisc
On 5/1/25 3:30 PM, Amery Hung wrote:
> 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);
fifo_skel->links.fifo = bpf_map__attach_struct_ops(....);
Then no need to bpf_link__destroy(link). bpf_qdisc_fifo__destroy() should do.
> + 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;
This should be 'goto out_restore_dflt_qdisc'.
I would stay with minimum number of cleanup labels if possible. Initialize the
variables that need to be cleaned up instead. There is no need to optimize each
cleanup case for a test,
e.g. "struct netns_obj netns = NULL; char default_qdisc[IFNAMSIZ] = {};..."
> +
> + 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;
Instead of pipe and grep, how about having the bpf_fifo_init bpf prog to set a
global variable when called and then check the "fifo_skel->bss->init_called ==
true" here?
> +
> + 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();
> +}
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