netdev - Re: [PATCH bpf-next 09/13] bpf: Add BPF_FUNC

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: <d34fddb1-4477-12e7-8391-368fdf8ab964@gmail.com>
Date:   Mon, 16 Dec 2019 16:34:08 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Alexei Starovoitov <ast@...com>, Martin Lau <kafai@...com>,
        Eric Dumazet <eric.dumazet@...il.com>
Cc:     "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        Kernel Team <Kernel-team@...com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next 09/13] bpf: Add BPF_FUNC_jiffies



On 12/16/19 3:08 PM, Alexei Starovoitov wrote:
> On 12/16/19 11:14 AM, Martin Lau wrote:
>> At least for bpf_dctcp.c, I did not expect it could be that close to tcp_dctcp.c
>> when I just started converted it.  tcp_cubic/bpf_cubic still has some TBD
>> on jiffies/msec.
>>
>> Agree that it is beneficial to have one copy.   It is likely
>> I need to make some changes on the tcp_*.c side also.  Hence, I prefer
>> to give it a try in a separate series, e.g. revert the kernel side
>> changes will be easier.
> 
> I've looked at bpf_cubic.c and bpf_dctcp.c as examples of what this
> patch set can do. They're selftests of the feature.
> What's the value of keeping them in sync with real kernel cc-s?
> I think it's fine if they quickly diverge.
> The value of them as selftests is important though. Quite a bit of BTF
> and verifier logic is being tested.
> May be add a comment saying that bpf_cubic.c is like cubic, but doesn't
> have to be exactly cubic ?
> 

The reason I mentioned this is that I am currently working on a fix of Hystart
logic, which is quite broken at the moment.

(hystart_train detection triggers in cases it should not)

But yes, if we add a comment warning potential users, this should be fine.