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

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Message-ID: <20190626191945.2mktaqrcrfcrfc66@breakpoint.cc>
Date:   Wed, 26 Jun 2019 21:19:45 +0200
From:   Florian Westphal <fw@...len.de>
To:     Florian Westphal <fw@...len.de>
Cc:     wenxu@...oud.cn, pablo@...filter.org,
        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

Florian Westphal <fw@...len.de> wrote:
> 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 :-)

Addendum: Did you look at the nftables fwd expression?  Maybe you can use
it as a simpler way to speed things up?