netdev - Re: [PATCH v7 0/6] Add eBPF hooks for cgroups

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Message-ID: <20161029045107.GA61294@ast-mbp.thefacebook.com>
Date:   Fri, 28 Oct 2016 21:51:09 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Lorenzo Colitti <lorenzo@...gle.com>
Cc:     Daniel Mack <daniel@...que.org>,
        Pablo Neira Ayuso <pablo@...filter.org>, htejun@...com,
        Daniel Borkmann <daniel@...earbox.net>, ast@...com,
        David Miller <davem@...emloft.net>, kafai@...com,
        Florian Westphal <fw@...len.de>, harald@...hat.com,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        sargun@...gun.me, cgroups@...r.kernel.org
Subject: Re: [PATCH v7 0/6] Add eBPF hooks for cgroups

On Sat, Oct 29, 2016 at 12:51:37PM +0900, Lorenzo Colitti wrote:
> On Thu, Oct 27, 2016 at 5:40 PM, Daniel Mack <daniel@...que.org> wrote:
> > It's not anything new. These hooks live on the very same level as
> > SO_ATTACH_FILTER. The only differences are that the BPF programs are
> > stored in the cgroup, and not in the socket, and that they exist for
> > egress as well.
> 
> What's the use case for egress?
> 
> We (android networking) are currently looking at implementing network
> accounting via eBPF in order to replace the out-of-tree xt_qtaguid
> code. A per-cgroup eBPF program run on all traffic would be great. But
> when we looked at this patchset we realized it would not be useful for
> accounting purposes because even if a packet is counted here, it might
> still be dropped by netfilter hooks.

don't use out-of-tree and instead drop using this mechanism or
any other in-kernel method? ;)
We (facebook infrastructure) have been using iptables and bpf networking
together with great success. They nicely co-exist and complement each other.
There is no need to reinvent the wheel if existing solution works.
iptables are great for their purpose.

> It seems like it would be much more useful to be able to do this in an
> iptables rule.

there is iptables+cBPF support. It's being used in some cases already.