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Date: Mon, 20 May 2024 20:15:04 -0700
From: Stanislav Fomichev <sdf@...gle.com>
To: Amery Hung <ameryhung@...il.com>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, yangpeihao@...u.edu.cn,
daniel@...earbox.net, andrii@...nel.org, martin.lau@...nel.org,
sinquersw@...il.com, toke@...hat.com, jhs@...atatu.com, jiri@...nulli.us,
xiyou.wangcong@...il.com, yepeilin.cs@...il.com
Subject: Re: [RFC PATCH v8 17/20] selftests: Add a basic fifo qdisc test
On 05/10, Amery Hung wrote:
> This selftest shows a bare minimum fifo qdisc, which simply enqueues skbs
> into the back of a bpf list and dequeues from the front of the list.
>
> Signed-off-by: Amery Hung <amery.hung@...edance.com>
> ---
> .../selftests/bpf/prog_tests/bpf_qdisc.c | 161 ++++++++++++++++++
> .../selftests/bpf/progs/bpf_qdisc_common.h | 23 +++
> .../selftests/bpf/progs/bpf_qdisc_fifo.c | 83 +++++++++
> 3 files changed, 267 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
> create mode 100644 tools/testing/selftests/bpf/progs/bpf_qdisc_common.h
> create mode 100644 tools/testing/selftests/bpf/progs/bpf_qdisc_fifo.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
> new file mode 100644
> index 000000000000..295d0216e70f
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
> @@ -0,0 +1,161 @@
> +#include <linux/pkt_sched.h>
> +#include <linux/rtnetlink.h>
> +#include <test_progs.h>
> +
> +#include "network_helpers.h"
> +#include "bpf_qdisc_fifo.skel.h"
> +
> +#ifndef ENOTSUPP
> +#define ENOTSUPP 524
> +#endif
> +
> +#define LO_IFINDEX 1
> +
> +static const unsigned int total_bytes = 10 * 1024 * 1024;
> +static int stop;
> +
> +static void *server(void *arg)
> +{
> + int lfd = (int)(long)arg, err = 0, fd;
> + ssize_t nr_sent = 0, bytes = 0;
> + char batch[1500];
> +
> + fd = accept(lfd, NULL, NULL);
> + while (fd == -1) {
> + if (errno == EINTR)
> + continue;
> + err = -errno;
> + goto done;
> + }
> +
> + if (settimeo(fd, 0)) {
> + err = -errno;
> + goto done;
> + }
> +
> + while (bytes < total_bytes && !READ_ONCE(stop)) {
> + nr_sent = send(fd, &batch,
> + MIN(total_bytes - bytes, sizeof(batch)), 0);
> + if (nr_sent == -1 && errno == EINTR)
> + continue;
> + if (nr_sent == -1) {
> + err = -errno;
> + break;
> + }
> + bytes += nr_sent;
> + }
> +
> + ASSERT_EQ(bytes, total_bytes, "send");
> +
> +done:
> + if (fd >= 0)
> + close(fd);
> + if (err) {
> + WRITE_ONCE(stop, 1);
> + return ERR_PTR(err);
> + }
> + return NULL;
> +}
> +
> +static void do_test(char *qdisc)
> +{
> + DECLARE_LIBBPF_OPTS(bpf_tc_hook, hook, .ifindex = LO_IFINDEX,
> + .attach_point = BPF_TC_QDISC,
> + .parent = TC_H_ROOT,
> + .handle = 0x8000000,
> + .qdisc = qdisc);
> + struct sockaddr_in6 sa6 = {};
> + ssize_t nr_recv = 0, bytes = 0;
> + int lfd = -1, fd = -1;
> + pthread_t srv_thread;
> + socklen_t addrlen = sizeof(sa6);
> + void *thread_ret;
> + char batch[1500];
> + int err;
> +
> + WRITE_ONCE(stop, 0);
> +
> + err = bpf_tc_hook_create(&hook);
> + if (!ASSERT_OK(err, "attach qdisc"))
> + return;
> +
> + lfd = start_server(AF_INET6, SOCK_STREAM, NULL, 0, 0);
> + if (!ASSERT_NEQ(lfd, -1, "socket")) {
> + bpf_tc_hook_destroy(&hook);
> + return;
> + }
> +
> + fd = socket(AF_INET6, SOCK_STREAM, 0);
> + if (!ASSERT_NEQ(fd, -1, "socket")) {
> + bpf_tc_hook_destroy(&hook);
> + close(lfd);
> + return;
> + }
> +
> + if (settimeo(lfd, 0) || settimeo(fd, 0))
> + goto done;
> +
> + err = getsockname(lfd, (struct sockaddr *)&sa6, &addrlen);
> + if (!ASSERT_NEQ(err, -1, "getsockname"))
> + goto done;
> +
> + /* connect to server */
> + err = connect(fd, (struct sockaddr *)&sa6, addrlen);
> + if (!ASSERT_NEQ(err, -1, "connect"))
> + goto done;
> +
> + err = pthread_create(&srv_thread, NULL, server, (void *)(long)lfd);
> + if (!ASSERT_OK(err, "pthread_create"))
> + goto done;
> +
> + /* recv total_bytes */
> + while (bytes < total_bytes && !READ_ONCE(stop)) {
> + nr_recv = recv(fd, &batch,
> + MIN(total_bytes - bytes, sizeof(batch)), 0);
> + if (nr_recv == -1 && errno == EINTR)
> + continue;
> + if (nr_recv == -1)
> + break;
> + bytes += nr_recv;
> + }
> +
> + ASSERT_EQ(bytes, total_bytes, "recv");
> +
> + WRITE_ONCE(stop, 1);
> + pthread_join(srv_thread, &thread_ret);
> + ASSERT_OK(IS_ERR(thread_ret), "thread_ret");
> +
> +done:
> + close(lfd);
> + close(fd);
> +
> + bpf_tc_hook_destroy(&hook);
> + return;
> +}
> +
> +static void test_fifo(void)
> +{
> + struct bpf_qdisc_fifo *fifo_skel;
> + struct bpf_link *link;
> +
> + 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;
> + }
> +
> + do_test("bpf_fifo");
> +
> + bpf_link__destroy(link);
> + bpf_qdisc_fifo__destroy(fifo_skel);
> +}
> +
> +void test_bpf_qdisc(void)
> +{
> + if (test__start_subtest("fifo"))
> + test_fifo();
> +}
> diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_common.h b/tools/testing/selftests/bpf/progs/bpf_qdisc_common.h
> new file mode 100644
> index 000000000000..96ab357de28e
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_common.h
> @@ -0,0 +1,23 @@
> +#ifndef _BPF_QDISC_COMMON_H
> +#define _BPF_QDISC_COMMON_H
> +
> +#define NET_XMIT_SUCCESS 0x00
> +#define NET_XMIT_DROP 0x01 /* skb dropped */
> +#define NET_XMIT_CN 0x02 /* congestion notification */
> +
> +#define TC_PRIO_CONTROL 7
> +#define TC_PRIO_MAX 15
> +
> +void bpf_skb_set_dev(struct sk_buff *skb, struct Qdisc *sch) __ksym;
> +u32 bpf_skb_get_hash(struct sk_buff *p) __ksym;
> +void bpf_skb_release(struct sk_buff *p) __ksym;
> +void bpf_qdisc_skb_drop(struct sk_buff *p, struct bpf_sk_buff_ptr *to_free) __ksym;
> +void bpf_qdisc_watchdog_schedule(struct Qdisc *sch, u64 expire, u64 delta_ns) __ksym;
> +bool bpf_qdisc_find_class(struct Qdisc *sch, u32 classid) __ksym;
> +int bpf_qdisc_create_child(struct Qdisc *sch, u32 min,
> + struct netlink_ext_ack *extack) __ksym;
> +int bpf_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, u32 classid,
> + struct bpf_sk_buff_ptr *to_free_list) __ksym;
> +struct sk_buff *bpf_qdisc_dequeue(struct Qdisc *sch, u32 classid) __ksym;
> +
> +#endif
> diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fifo.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fifo.c
> new file mode 100644
> index 000000000000..433fd9c3639c
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fifo.c
> @@ -0,0 +1,83 @@
> +#include <vmlinux.h>
> +#include "bpf_experimental.h"
> +#include "bpf_qdisc_common.h"
> +
> +char _license[] SEC("license") = "GPL";
> +
> +#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))
> +
> +private(B) struct bpf_spin_lock q_fifo_lock;
> +private(B) struct bpf_list_head q_fifo __contains_kptr(sk_buff, bpf_list);
> +
> +unsigned int q_limit = 1000;
> +unsigned int q_qlen = 0;
> +
> +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)
> +{
> + q_qlen++;
> + if (q_qlen > q_limit) {
> + bpf_qdisc_skb_drop(skb, to_free);
> + return NET_XMIT_DROP;
> + }
[..]
> + bpf_spin_lock(&q_fifo_lock);
> + bpf_list_excl_push_back(&q_fifo, &skb->bpf_list);
> + bpf_spin_unlock(&q_fifo_lock);
Can you also expand a bit on the locking here and elsewhere? And how it
interplays with TCQ_F_NOLOCK?
As I mentioned at lsfmmbpf, I don't think there is a lot of similar
locking in the existing C implementations? So why do we need it here?
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