Re: [PATCH nf-next] netfilter: nf_tables: add ebpf expression
From: Alexei Starovoitov <hidden>
Date: 2022-09-02 17:06:45
Also in:
bpf, netfilter-devel
On Thu, Sep 1, 2022 at 3:14 AM Florian Westphal [off-list ref] wrote:
Daniel Borkmann [off-list ref] wrote:quoted
On 8/31/22 7:26 PM, Alexei Starovoitov wrote:quoted
On Wed, Aug 31, 2022 at 8:53 AM Florian Westphal [off-list ref] wrote: As a minimum we shouldn't step on the same rakes. xt_ebpf would be the same dead code as xt_bpf.+1, and on top, the user experience will just be horrible. :(Compared to what?quoted
quoted
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If you are open to BPF_PROG_TYPE_NETFILTER I can go that route as well, raw bpf program attachment via NF_HOOK and the bpf dispatcher, but it will take significantly longer to get there. It involves reviving https://lore.kernel.org/netfilter-devel/20211014121046.29329-1-fw@strlen.de/ (local)I missed it earlier. What is the end goal ? Optimize nft run-time with on the fly generation of bpf byte code ?Or rather to provide a pendant to nft given existence of xt_bpf, and the latter will be removed at some point? (If so, can't we just deprecate the old xt_bpf?)See my reply to Alexey, immediate goal was to get rid of the indirect calls by providing a tailored/jitted equivalent of nf_hook_slow(). The next step could be to allow implementation of netfilter hooks (i.e., kernel modules that call nf_register_net_hook()) in bpf but AFAIU it requires addition of BPF_PROG_TYPE_NETFILTER etc.
We were adding new prog and maps types in the past. Now new features are being added differently. All of the networking either works with sk_buff-s or xdp frames. We try hard not to add any new uapi helpers. Everything is moving to kfuncs. Other sub-systems should be able to use bpf without touching the bpf core. See hid-bpf as an example. It needs several verifier improvements, but doesn't need new prog types, helpers, etc.
After that, yes, one could think about how to jit nft_do_chain() and all the rest of the nft machinery.
Sounds like a ton of work. All that just to accelerate nft a bit? I think there are more impactful projects to work on. For example, accelerating classic iptables with bpf would immediately help a bunch of users.