From: Cong Wang <xiyou.wangcong@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: David Miller <davem@davemloft.net>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
Lorenz Bauer <lmb@cloudflare.com>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
bpf <bpf@vger.kernel.org>, kernel-team <kernel-team@fb.com>
Subject: Re: [RFC PATCH bpf-next] bpf: Introduce bpf_timer
Date: Mon, 24 May 2021 21:59:31 -0700 [thread overview]
Message-ID: <CAM_iQpVYBNkjDeo+2CzD-qMnR4-2uW+QdMSf_7ohwr0NjgipaQ@mail.gmail.com> (raw)
In-Reply-To: <CAM_iQpU-Cvpf-+9R0ZdZY+5Dv+stfodrH0MhvSgryv_tGiX7pA@mail.gmail.com>
On Mon, May 24, 2021 at 8:16 PM Cong Wang <xiyou.wangcong@gmail.com> wrote:
>
> On Sun, May 23, 2021 at 9:01 AM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> >
> > On Fri, May 21, 2021 at 2:37 PM Cong Wang <xiyou.wangcong@gmail.com> wrote:
> > >
> > > Hi, Alexei
> > >
> > > On Thu, May 20, 2021 at 11:52 PM Alexei Starovoitov
> > > <alexei.starovoitov@gmail.com> wrote:
> > > >
> > > > Introduce 'struct bpf_timer' that can be embedded in most BPF map types
> > > > and helpers to operate on it:
> > > > long bpf_timer_init(struct bpf_timer *timer, void *callback, int flags)
> > > > long bpf_timer_mod(struct bpf_timer *timer, u64 msecs)
> > > > long bpf_timer_del(struct bpf_timer *timer)
> > >
> > > Like we discussed, this approach would make the timer harder
> > > to be independent of other eBPF programs, which is a must-have
> > > for both of our use cases (mine and Jamal's). Like you explained,
> > > this requires at least another program array, a tail call, a mandatory
> > > prog pinning to work.
> >
> > That is simply not true.
>
> Which part is not true? The above is what I got from your explanation.
I tried to write some code sketches to use your timer to implement
our conntrack logic, below shows how difficult it is to use, it does not
even include the user-space part where eBPF programs are put
into the program array.
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 1000);
__type(key, struct tuple);
__type(value, struct foo);
} conntrack SEC(".maps");
struct map_elem {
struct bpf_timer timer;
struct bpf_map *target;
u32 expires;
};
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 1000);
__type(key, int);
__type(value, struct map_elem);
} timers SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
__uint(key_size, sizeof(u32));
__uint(value_size, sizeof(u32));
__uint(max_entries, 8);
} jmp_table SEC(".maps");
static __u64
cleanup_conntrack(struct bpf_map *map, struct tuple *key, struct foo *val,
struct callback_ctx *data)
{
if (val.expires < now)
bpf_map_delete_elem(conntrack, key);
}
static int timer_cb(struct bpf_map *map, int *key, struct map_elem *val)
{
bpf_for_each_map_elem(val->target, cleanup_conntrack, ....);
/* re-arm the timer again to execute after 1 msec */
bpf_timer_mod(&val->timer, 1);
return 0;
}
SEC("prog/0")
int install_timer(void)
{
struct map_elem *val;
int key = 0;
val = bpf_map_lookup_elem(&timers, &key);
if (val) {
bpf_timer_init(&val->timer, timer_cb, 0);
bpf_timer_mod(&val->timer, val->expires);
}
}
SEC("prog/1")
int mod_timer(void)
{
struct map_elem *val;
int key = 0;
val = bpf_map_lookup_elem(&timers, &key);
if (val) {
// XXX: how do we know if a timer has been installed?
bpf_timer_mod(&val->timer, val->expires);
}
}
SEC("ingress")
void ingress(struct __sk_buff *skb)
{
struct tuple tuple;
// extract tuple from skb
if (bpf_map_lookup_elem(&timers, &key) == NULL)
bpf_tail_call(NULL, &jmp_table, 0);
// here is not reachable unless failure
val = bpf_map_lookup_elem(&conntrack, &tuple);
if (val && val->expires < now) {
bpf_tail_call(NULL, &jmp_table, 1);
// here is not reachable unless failure
}
}
SEC("egress")
void egress(struct __sk_buff *skb)
{
struct tuple tuple;
// extract tuple from skb
if (bpf_map_lookup_elem(&timers, &key) == NULL)
bpf_tail_call(NULL, &jmp_table, 0);
// here is not reachable unless failure
val = bpf_map_lookup_elem(&conntrack, &tuple);
if (val && val->expires < now) {
bpf_tail_call(NULL, &jmp_table, 1);
// here is not reachable unless failure
}
}
next prev parent reply other threads:[~2021-05-25 4:59 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-20 18:55 [RFC PATCH bpf-next] bpf: Introduce bpf_timer Alexei Starovoitov
2021-05-21 14:38 ` Alexei Starovoitov
2021-05-21 21:37 ` Cong Wang
2021-05-23 16:01 ` Alexei Starovoitov
2021-05-24 8:45 ` Lorenz Bauer
2021-05-25 3:16 ` Cong Wang
2021-05-25 4:59 ` Cong Wang [this message]
2021-05-25 18:21 ` Alexei Starovoitov
2021-05-25 19:35 ` Jamal Hadi Salim
2021-05-25 19:57 ` Alexei Starovoitov
2021-05-25 21:09 ` Jamal Hadi Salim
2021-05-25 22:08 ` Alexei Starovoitov
2021-05-26 15:34 ` Jamal Hadi Salim
2021-05-26 16:58 ` Alexei Starovoitov
2021-05-26 18:25 ` Jamal Hadi Salim
2021-05-30 6:36 ` Cong Wang
2021-06-02 2:00 ` Alexei Starovoitov
2021-06-02 8:48 ` Toke Høiland-Jørgensen
2021-06-02 17:54 ` Martin KaFai Lau
2021-06-02 18:13 ` Kumar Kartikeya Dwivedi
2021-06-02 18:26 ` Alexei Starovoitov
2021-06-02 18:30 ` Kumar Kartikeya Dwivedi
2021-06-02 18:46 ` John Fastabend
2021-05-23 11:48 ` Toke Høiland-Jørgensen
2021-05-23 15:58 ` Alexei Starovoitov
2021-05-24 8:42 ` Lorenz Bauer
2021-05-24 14:48 ` Alexei Starovoitov
2021-05-24 17:33 ` Alexei Starovoitov
2021-05-24 18:39 ` Toke Høiland-Jørgensen
2021-05-24 18:38 ` Toke Høiland-Jørgensen
2021-05-24 11:49 ` Lorenz Bauer
2021-05-24 14:56 ` Alexei Starovoitov
2021-05-24 19:13 ` Andrii Nakryiko
2021-05-25 5:22 ` Cong Wang
2021-05-25 19:47 ` Andrii Nakryiko
-- strict thread matches above, loose matches on Subject: below --
2021-04-01 4:26 [RFC Patch bpf-next] bpf: introduce bpf timer Cong Wang
2021-04-01 6:38 ` Song Liu
2021-04-01 17:28 ` Cong Wang
2021-04-01 20:17 ` Song Liu
2021-04-02 17:34 ` Cong Wang
2021-04-02 17:57 ` Song Liu
2021-04-02 19:08 ` Cong Wang
2021-04-02 19:43 ` Song Liu
2021-04-02 20:57 ` Cong Wang
2021-04-02 23:31 ` Song Liu
2021-04-05 23:49 ` Cong Wang
2021-04-06 1:07 ` Song Liu
2021-04-06 1:24 ` Cong Wang
2021-04-06 6:17 ` Song Liu
2021-04-06 16:48 ` Cong Wang
2021-04-06 23:36 ` Song Liu
2021-04-08 22:45 ` Cong Wang
2021-04-02 19:28 ` Alexei Starovoitov
2021-04-02 21:24 ` Cong Wang
2021-04-02 23:45 ` Alexei Starovoitov
2021-04-06 0:36 ` Cong Wang
2021-04-12 23:01 ` Alexei Starovoitov
2021-04-15 4:02 ` Cong Wang
2021-04-15 4:25 ` Alexei Starovoitov
2021-04-15 15:51 ` Cong Wang
2021-04-26 23:00 ` Cong Wang
2021-04-26 23:05 ` Alexei Starovoitov
2021-04-26 23:37 ` Cong Wang
2021-04-27 2:01 ` Alexei Starovoitov
2021-04-27 11:52 ` Jamal Hadi Salim
2021-04-27 16:36 ` Cong Wang
2021-04-27 18:33 ` Alexei Starovoitov
2021-05-09 5:37 ` Cong Wang
2021-05-10 20:55 ` Jamal Hadi Salim
2021-05-11 21:29 ` Cong Wang
2021-05-12 22:56 ` Jamal Hadi Salim
2021-05-11 5:05 ` Joe Stringer
2021-05-11 21:08 ` Cong Wang
2021-05-12 22:43 ` Jamal Hadi Salim
2021-05-13 18:45 ` Jamal Hadi Salim
2021-05-14 2:53 ` Cong Wang
2021-08-11 21:03 ` Joe Stringer
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