netdev - Re: [RFC Patch bpf-next] bpf: introduce bpf timer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAADnVQLFehCeQRbwEQ9VM-=Y3V3es2Ze8gFPs6cZHwNH0Ct7vw@mail.gmail.com>
Date:   Mon, 26 Apr 2021 16:05:16 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>,
        Xiongchun Duan <duanxiongchun@...edance.com>,
        Dongdong Wang <wangdongdong.6@...edance.com>,
        Muchun Song <songmuchun@...edance.com>,
        Cong Wang <cong.wang@...edance.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Pedro Tammela <pctammela@...atatu.com>,
        Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [RFC Patch bpf-next] bpf: introduce bpf timer

On Mon, Apr 26, 2021 at 4:00 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> Hi, Alexei
>
> On Wed, Apr 14, 2021 at 9:25 PM Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> >
> > On Wed, Apr 14, 2021 at 9:02 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
> > >
> > > Then how do you prevent prog being unloaded when the timer callback
> > > is still active?
> >
> > As I said earlier:
> > "
> > If prog refers such hmap as above during prog free the kernel does
> > for_each_map_elem {if (elem->opaque) del_timer().}
> > "
>
> I have discussed this with my colleagues, sharing timers among different
> eBPF programs is a must-have feature for conntrack.
>
> For conntrack, we need to attach two eBPF programs, one on egress and
> one on ingress. They share a conntrack table (an eBPF map), and no matter
> we use a per-map or per-entry timer, updating the timer(s) could happen
> on both sides, hence timers must be shared for both.
>
> So, your proposal we discussed does not work well for this scenario.

why? The timer inside the map element will be shared just fine.
Just like different progs can see the same map value.

Also if your colleagues have something to share they should be
posting to the mailing list. Right now you're acting as a broken phone
passing info back and forth and the knowledge gets lost.
Please ask your colleagues to participate online.