From: Daniel Borkmann <daniel-FeC+5ew28dpmcu3hnIyYJQ@public•gmane.org>
To: Alexei Starovoitov <ast-uqk4Ao+rVK5Wk0Htik3J/w@public•gmane.org>,
Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public•gmane.org>
Cc: "David S. Miller" <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public•gmane.org>,
Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public•gmane.org>,
Hannes Frederic Sowa
<hannes-tFNcAqjVMyqKXQKiL6tip0B+6BGkLq7r@public•gmane.org>,
Eric Dumazet <edumazet-hpIqsD4AKlfQT0dZR+AlfA@public•gmane.org>,
Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public•gmane.org>,
linux-api-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public•gmane.org
Subject: Re: [PATCH net-next 1/2] bpf: enable non-root eBPF programs
Date: Tue, 06 Oct 2015 20:03:55 +0200 [thread overview]
Message-ID: <56140D0B.2040504@iogearbox.net> (raw)
In-Reply-To: <561409EC.5050005-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org>
On 10/06/2015 07:50 PM, Alexei Starovoitov wrote:
> On 10/6/15 1:39 AM, Daniel Borkmann wrote:
>>>> [...] Also classic BPF would then need to test for it, since a socket
>>>> filter
>>>> doesn't really know whether native eBPF is loaded there or a
>>>> classic-to-eBPF
>>>> transformed one, and classic never makes use of this. Anyway, it
>>>> could be done
>>>> by adding a bit flag cb_access:1 to the bpf_prog, set it during eBPF
>>>> verification phase, and test it inside sk_filter() if I see it
>>>> correctly.
>>>
>>> That could also be done in an unlikely() branch, to keep the cost to
>>> the non-eBPF
>>> case near zero.
>>
>> Yes, agreed. For the time being, the majority of users are coming from the
>> classic BPF side anyway and the unlikely() could still be changed later on
>> if it should not be the case anymore. The flag and bpf_func would share the
>> same cacheline as well.
>
> was also thinking that we can do it only in paths that actually
> have multiple protocol layers, since today bpf is mainly used with
> tcpdump(raw_socket) and new af_packet fanout both have cb cleared
> on RX, because it just came out of alloc_skb and no layers were called,
> and on TX we can clear 20 bytes in dev_queue_xmit_nit().
> af_unix/netlink also have clean skb. Need to analyze tun and sctp...
> but it feels overly fragile to save a branch in sk_filter,
> so planning to go with
> if(unlikely(prog->cb_access)) memset in sk_filter().
I was also thinking that for dev_queue_xmit_nit(), since we do the skb_clone()
there, to have a clone version (w/o affecting performance of the current one)
that instead of copying cb[] over, it would just do a memset(). But that would
just be limited to AF_PACKET, and doesn't catch all sk_filter() users.
Thanks,
Daniel
next prev parent reply other threads:[~2015-10-06 18:03 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-05 20:48 [PATCH net-next 0/2] bpf: unprivileged Alexei Starovoitov
2015-10-05 20:48 ` [PATCH net-next 1/2] bpf: enable non-root eBPF programs Alexei Starovoitov
[not found] ` <1444078101-29060-2-git-send-email-ast-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org>
2015-10-05 21:00 ` Kees Cook
2015-10-05 21:12 ` Alexei Starovoitov
[not found] ` <5612E7C4.1010306-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org>
2015-10-05 21:16 ` Andy Lutomirski
2015-10-05 21:32 ` Alexei Starovoitov
2015-10-05 22:02 ` Kees Cook
2015-10-06 0:28 ` Alexei Starovoitov
2015-10-08 2:29 ` Alexei Starovoitov
2015-10-05 22:14 ` Daniel Borkmann
[not found] ` <5612F639.2050305-FeC+5ew28dpmcu3hnIyYJQ@public.gmane.org>
2015-10-06 0:51 ` Alexei Starovoitov
[not found] ` <56131B1F.80002-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org>
2015-10-06 7:13 ` Ingo Molnar
2015-10-06 8:05 ` Daniel Borkmann
2015-10-06 8:20 ` Ingo Molnar
[not found] ` <20151006082048.GA18287-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2015-10-06 8:39 ` Daniel Borkmann
[not found] ` <561388D1.30406-FeC+5ew28dpmcu3hnIyYJQ@public.gmane.org>
2015-10-06 17:50 ` Alexei Starovoitov
2015-10-06 17:56 ` Eric Dumazet
[not found] ` <1444154160.9555.5.camel-XN9IlZ5yJG9HTL0Zs8A6p/gx64E7kk8eUsxypvmhUTTZJqsBc5GL+g@public.gmane.org>
2015-10-06 18:05 ` Andy Lutomirski
2015-10-07 6:05 ` Ingo Molnar
2015-10-06 19:26 ` Alexei Starovoitov
[not found] ` <561409EC.5050005-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org>
2015-10-06 18:03 ` Daniel Borkmann [this message]
2015-10-06 12:45 ` Daniel Borkmann
2015-10-07 21:20 ` Alexei Starovoitov
[not found] ` <56158CAF.9030209-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org>
2015-10-07 22:07 ` Daniel Borkmann
2015-10-07 22:22 ` Kees Cook
2015-10-07 23:49 ` Alexei Starovoitov
[not found] ` <5615AF92.50402-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org>
2015-10-08 6:21 ` Ingo Molnar
2015-10-08 6:30 ` Alexei Starovoitov
2015-10-08 17:42 ` Kees Cook
2015-10-05 20:48 ` [PATCH net-next 2/2] bpf: charge user for creation of BPF maps and programs Alexei Starovoitov
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