netdev - Re: [PATCH 2/3 nf-next] netfilter:nf_flow_table: Support bridge type flow offload

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Date:   Wed, 26 Jun 2019 20:38:16 +0200
From:   Florian Westphal <fw@...len.de>
To:     wenxu@...oud.cn
Cc:     pablo@...filter.org, fw@...len.de, netfilter-devel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 2/3 nf-next] netfilter:nf_flow_table: Support bridge type
 flow offload

wenxu@...oud.cn <wenxu@...oud.cn> wrote:
> diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c
> index 0016bb8..9af01ef 100644
> --- a/net/netfilter/nf_flow_table_ip.c
> +++ b/net/netfilter/nf_flow_table_ip.c
> -	neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
> +	if (family == NFPROTO_IPV4) {
> +		iph = ip_hdr(skb);
> +		ip_decrease_ttl(iph);
> +
> +		nexthop = rt_nexthop(rt, flow->tuplehash[!dir].tuple.src_v4.s_addr);
> +		skb_dst_set_noref(skb, &rt->dst);
> +		neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
> +	} else {
> +		const struct net_bridge_port *p;
> +
> +		if (vlan_tag && (p = br_port_get_rtnl_rcu(state->in)))
> +			__vlan_hwaccel_put_tag(skb, p->br->vlan_proto, vlan_tag);
> +		else
> +			__vlan_hwaccel_clear_tag(skb);
> +
> +		br_dev_queue_push_xmit(state->net, state->sk, skb);

Won't that result in a module dep on bridge?

Whats the idea with this patch?

Do you see a performance improvement when bypassing bridge layer? If so,
how much?

I just wonder if its really cheaper than not using bridge conntrack in
the first place :-)