netdev - Re: [PATCH bpf-next v5 2/5] netfilter: bpf: Support BPF_F_NETFILTER_IP

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Date: Fri, 21 Jul 2023 01:19:04 +0200
From: Florian Westphal <fw@...len.de>
To: Daniel Xu <dxu@...uu.xyz>
Cc: daniel@...earbox.net, kadlec@...filter.org, ast@...nel.org,
	pablo@...filter.org, kuba@...nel.org, davem@...emloft.net,
	andrii@...nel.org, edumazet@...gle.com, pabeni@...hat.com,
	fw@...len.de, alexei.starovoitov@...il.com, martin.lau@...ux.dev,
	song@...nel.org, yhs@...com, john.fastabend@...il.com,
	kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com,
	jolsa@...nel.org, bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
	netfilter-devel@...r.kernel.org, coreteam@...filter.org,
	netdev@...r.kernel.org, dsahern@...nel.org
Subject: Re: [PATCH bpf-next v5 2/5] netfilter: bpf: Support
 BPF_F_NETFILTER_IP_DEFRAG in netfilter link

Daniel Xu <dxu@...uu.xyz> wrote:
> +	const struct nf_defrag_hook __maybe_unused *hook;
> +
> +	switch (link->hook_ops.pf) {
> +#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
> +	case NFPROTO_IPV4:
> +		hook = get_proto_defrag_hook(link, nf_defrag_v4_hook, "nf_defrag_ipv4");
> +		if (IS_ERR(hook))
> +			return PTR_ERR(hook);
> +
> +		link->defrag_hook = hook;
> +		return 0;
> +#endif
> +#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
> +	case NFPROTO_IPV6:
> +		hook = get_proto_defrag_hook(link, nf_defrag_v6_hook, "nf_defrag_ipv6");
> +		if (IS_ERR(hook))
> +			return PTR_ERR(hook);
> +
> +		link->defrag_hook = hook;
> +		return 0;
> +#endif
> +	default:
> +		return -EAFNOSUPPORT;
> +	}
> +}
> +
> +static void bpf_nf_disable_defrag(struct bpf_nf_link *link)
> +{
> +	const struct nf_defrag_hook *hook = link->defrag_hook;
> +
> +	if (!hook)
> +		return;
> +	hook->disable(link->net);
> +	module_put(hook->owner);
> +}
> +
>  static void bpf_nf_link_release(struct bpf_link *link)
>  {
>  	struct bpf_nf_link *nf_link = container_of(link, struct bpf_nf_link, link);
> @@ -37,6 +119,8 @@ static void bpf_nf_link_release(struct bpf_link *link)
>  	 */
>  	if (!cmpxchg(&nf_link->dead, 0, 1))
>  		nf_unregister_net_hook(nf_link->net, &nf_link->hook_ops);
> +
> +	bpf_nf_disable_defrag(nf_link);
>  }

I suspect this needs to be within the cmpxchg() branch to avoid
multiple ->disable() calls.

> +	if (attr->link_create.netfilter.flags & BPF_F_NETFILTER_IP_DEFRAG) {
> +		err = bpf_nf_enable_defrag(link);
> +		if (err) {
> +			bpf_link_cleanup(&link_primer);
> +			return err;
> +		}
> +	}
> +
>  	err = nf_register_net_hook(net, &link->hook_ops);
>  	if (err) {
		bpf_nf_disable_defrag(link);

Other than those nits this lgtm, thanks!