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From: Martin Lau <kafai@fb.com>
To: Jakub Sitnicki <jakub@cloudflare.com>
Cc: "bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"kernel-team@cloudflare.com" <kernel-team@cloudflare.com>,
	Stanislav Fomichev <sdf@fomichev.me>
Subject: Re: [PATCH bpf-next v2 1/2] flow_dissector: Allow updating the flow dissector program atomically
Date: Thu, 10 Oct 2019 19:41:30 +0000
Message-ID: <20191010194127.h3j5jmqbspj4ewgt@kafai-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <20191010181750.5964-2-jakub@cloudflare.com>

On Thu, Oct 10, 2019 at 08:17:49PM +0200, Jakub Sitnicki wrote:
> It is currently not possible to detach the flow dissector program and
> attach a new one in an atomic fashion, that is with a single syscall.
> Attempts to do so will be met with EEXIST error.
> 
> This makes updates to flow dissector program hard. Traffic steering that
> relies on BPF-powered flow dissection gets disrupted while old program has
> been already detached but the new one has not been attached yet.
> 
> There is also a window of opportunity to attach a flow dissector to a
> non-root namespace while updating the root flow dissector, thus blocking
> the update.
> 
> Lastly, the behavior is inconsistent with cgroup BPF programs, which can be
> replaced with a single bpf(BPF_PROG_ATTACH, ...) syscall without any
> restrictions.
> 
> Allow attaching a new flow dissector program when another one is already
> present with a restriction that it can't be the same program.
Acked-by: Martin KaFai Lau <kafai@fb.com>

  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-10 18:17 [PATCH bpf-next v2 0/2] Atomic flow dissector updates Jakub Sitnicki
2019-10-10 18:17 ` [PATCH bpf-next v2 1/2] flow_dissector: Allow updating the flow dissector program atomically Jakub Sitnicki
2019-10-10 19:41   ` Martin Lau [this message]
2019-10-10 18:17 ` [PATCH bpf-next v2 2/2] selftests/bpf: Check that flow dissector can be re-attached Jakub Sitnicki
2019-10-10 19:42   ` Martin Lau
2019-10-10 19:57 ` [PATCH bpf-next v2 0/2] Atomic flow dissector updates Stanislav Fomichev
2019-10-10 23:38 ` Daniel Borkmann
2019-10-11  8:31   ` Jakub Sitnicki

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