netdev - Re: [PATCH RFC,WIP 2/5] netfilter: add software flow offload infrastructure

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Message-ID: <20171103203249.GA25602@breakpoint.cc>
Date:   Fri, 3 Nov 2017 21:32:49 +0100
From:   Florian Westphal <fw@...len.de>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH RFC,WIP 2/5] netfilter: add software flow offload
 infrastructure

Pablo Neira Ayuso <pablo@...filter.org> wrote:
> +static int __init nf_flow_offload_module_init(void)
> +{
> +	struct rhashtable_params params = flow_offload_rhash_params;
> +	struct nf_hook_ops flow_offload_hook = {
> +		.hook		= nf_flow_offload_hook,
> +		.pf		= NFPROTO_NETDEV,
> +		.hooknum	= NF_NETDEV_INGRESS,
> +		.priority	= -100,

Magic number.  Should this be documented in nft?

Alternatively we could reject NETDEV_INGRESS base chains from
userspace if prio < 0 to prevent userspace rules from messing
with this flow offlaod infrastructure.

I guess the rationale of using auto-builtin hook is to avoid
forcing users to configure this with nftables rules?

> +	rtnl_lock();
> +	for_each_netdev(&init_net, dev) {
> +		entry = kmalloc(sizeof(*entry), GFP_KERNEL);
> +		if (!entry) {
> +			rtnl_unlock();
> +			return -ENOMEM;

This would need error unwinding (Unregistering the already-registered
hooks).

> +		err = nf_register_net_hook(&init_net, &entry->ops);
> +		if (err < 0)
> +			return err;

And here as well.