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Message-ID: <aHVVTHLh-3uKZG9o@lore-desk>
Date: Mon, 14 Jul 2025 21:06:52 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Pablo Neira Ayuso <pablo@...filter.org>
Cc: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
David Ahern <dsahern@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>,
Jozsef Kadlecsik <kadlec@...filter.org>,
Shuah Khan <shuah@...nel.org>, netdev@...r.kernel.org,
netfilter-devel@...r.kernel.org, coreteam@...filter.org,
linux-kselftest@...r.kernel.org
Subject: Re: [PATCH nf-next v3 1/2] net: netfilter: Add IPIP flowtable SW
acceleration
> On Jul 07, Pablo Neira Ayuso wrote:
> > On Fri, Jul 04, 2025 at 03:00:40PM +0200, Lorenzo Bianconi wrote:
> > > > On Thu, Jul 03, 2025 at 04:16:02PM +0200, Lorenzo Bianconi wrote:
> > > > > Introduce SW acceleration for IPIP tunnels in the netfilter flowtable
> > > > > infrastructure.
> > > > > IPIP SW acceleration can be tested running the following scenario where
> > > > > the traffic is forwarded between two NICs (eth0 and eth1) and an IPIP
> > > > > tunnel is used to access a remote site (using eth1 as the underlay device):
> > > >
> > > > Question below.
> > > >
> > > > > ETH0 -- TUN0 <==> ETH1 -- [IP network] -- TUN1 (192.168.100.2)
> > > > >
> > > > > $ip addr show
> > > > > 6: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
> > > > > link/ether 00:00:22:33:11:55 brd ff:ff:ff:ff:ff:ff
> > > > > inet 192.168.0.2/24 scope global eth0
> > > > > valid_lft forever preferred_lft forever
> > > > > 7: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
> > > > > link/ether 00:11:22:33:11:55 brd ff:ff:ff:ff:ff:ff
> > > > > inet 192.168.1.1/24 scope global eth1
> > > > > valid_lft forever preferred_lft forever
> > > > > 8: tun0@...E: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1480 qdisc noqueue state UNKNOWN group default qlen 1000
> > > > > link/ipip 192.168.1.1 peer 192.168.1.2
> > > > > inet 192.168.100.1/24 scope global tun0
> > > > > valid_lft forever preferred_lft forever
> > > > >
> > > > > $ip route show
> > > > > default via 192.168.100.2 dev tun0
> > > > > 192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.2
> > > > > 192.168.1.0/24 dev eth1 proto kernel scope link src 192.168.1.1
> > > > > 192.168.100.0/24 dev tun0 proto kernel scope link src 192.168.100.1
> > > > >
> > > > > $nft list ruleset
> > > > > table inet filter {
> > > > > flowtable ft {
> > > > > hook ingress priority filter
> > > > > devices = { eth0, eth1 }
> > > > > }
> > > > >
> > > > > chain forward {
> > > > > type filter hook forward priority filter; policy accept;
> > > > > meta l4proto { tcp, udp } flow add @ft
> > > > > }
> > > > > }
> > > > >
> > > > > Reproducing the scenario described above using veths I got the following
> > > > > results:
> > > > > - TCP stream transmitted into the IPIP tunnel:
> > > > > - net-next: ~41Gbps
> > > > > - net-next + IPIP flowtbale support: ~40Gbps
> > > > ^^^^^^^^^
> > > > no gain on tx side.
> > >
> > > In this case the IPIP flowtable acceleration is effective just on the ACKs
> > > packets so I guess it is expected we have ~ the same results. The real gain is
> > > when the TCP stream is from the tunnel net_device to the NIC one.
> >
> > That is, only rx side follows the flowtable datapath.
> >
> > > > > - TCP stream received from the IPIP tunnel:
> > > > > - net-next: ~35Gbps
> > > > > - net-next + IPIP flowtbale support: ~49Gbps
> > > > >
> > > > > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > > > > ---
> > > > > net/ipv4/ipip.c | 21 +++++++++++++++++++++
> > > > > net/netfilter/nf_flow_table_ip.c | 34 ++++++++++++++++++++++++++++++++--
> > > > > 2 files changed, 53 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
> > > > > index 3e03af073a1ccc3d7597a998a515b6cfdded40b5..05fb1c859170d74009d693bc8513183bdec3ff90 100644
> > > > > --- a/net/ipv4/ipip.c
> > > > > +++ b/net/ipv4/ipip.c
> > > > > @@ -353,6 +353,26 @@ ipip_tunnel_ctl(struct net_device *dev, struct ip_tunnel_parm_kern *p, int cmd)
> > > > > return ip_tunnel_ctl(dev, p, cmd);
> > > > > }
> > > > >
> > > > > +static int ipip_fill_forward_path(struct net_device_path_ctx *ctx,
> > > > > + struct net_device_path *path)
> > > > > +{
> > > > > + struct ip_tunnel *tunnel = netdev_priv(ctx->dev);
> > > > > + const struct iphdr *tiph = &tunnel->parms.iph;
> > > > > + struct rtable *rt;
> > > > > +
> > > > > + rt = ip_route_output(dev_net(ctx->dev), tiph->daddr, 0, 0, 0,
> > > > > + RT_SCOPE_UNIVERSE);
> > > > > + if (IS_ERR(rt))
> > > > > + return PTR_ERR(rt);
> > > > > +
> > > > > + path->type = DEV_PATH_ETHERNET;
> > > > > + path->dev = ctx->dev;
> > > > > + ctx->dev = rt->dst.dev;
> > > > > + ip_rt_put(rt);
> > > > > +
> > > > > + return 0;
> > > > > +}
> > > > > +
> > > > > static const struct net_device_ops ipip_netdev_ops = {
> > > > > .ndo_init = ipip_tunnel_init,
> > > > > .ndo_uninit = ip_tunnel_uninit,
> > > > > @@ -362,6 +382,7 @@ static const struct net_device_ops ipip_netdev_ops = {
> > > > > .ndo_get_stats64 = dev_get_tstats64,
> > > > > .ndo_get_iflink = ip_tunnel_get_iflink,
> > > > > .ndo_tunnel_ctl = ipip_tunnel_ctl,
> > > > > + .ndo_fill_forward_path = ipip_fill_forward_path,
> > > > > };
> > > > >
> > > > > #define IPIP_FEATURES (NETIF_F_SG | \
> > > > > diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c
> > > > > index 8cd4cf7ae21120f1057c4fce5aaca4e3152ae76d..6b55e00b1022f0a2b02d9bfd1bd34bb55c1b83f7 100644
> > > > > --- a/net/netfilter/nf_flow_table_ip.c
> > > > > +++ b/net/netfilter/nf_flow_table_ip.c
> > > > > @@ -277,13 +277,37 @@ static unsigned int nf_flow_xmit_xfrm(struct sk_buff *skb,
> > > > > return NF_STOLEN;
> > > > > }
> > > > >
> > > > > +static bool nf_flow_ip4_encap_proto(struct sk_buff *skb, u16 *size)
> > > > > +{
> > > > > + struct iphdr *iph;
> > > > > +
> > > > > + if (!pskb_may_pull(skb, sizeof(*iph)))
> > > > > + return false;
> > > > > +
> > > > > + iph = (struct iphdr *)skb_network_header(skb);
> > > > > + *size = iph->ihl << 2;
> > > > > +
> > > > > + if (ip_is_fragment(iph) || unlikely(ip_has_options(*size)))
> > > > > + return false;
> > > > > +
> > > > > + if (iph->ttl <= 1)
> > > > > + return false;
> > > > > +
> > > > > + return iph->protocol == IPPROTO_IPIP;
> > > >
> > >
> > > what kind of sanity checks are we supposed to perform? Something similar to
> > > what we have in ip_rcv_core()?
> >
> > I am not referring to sanity checks.
> >
> > VLAN/PPP ID (layer 2 encapsulation) is part of the lookup in the
> > flowtable, why IPIP (layer 3 tunnel) does not get the same handling?
>
> ack, right. Do you have any suggestion about what field (or combination
> of fields) we can use from the outer IP header similar to the VLAN/PPP
> encapsulation?
What about a hash computed over some of the outer IP header fields? (e.g IP
saddr and daddr).
Regards,
Lorenzo
>
> >
> > > > Once the flow is in the flowtable, it is possible to inject traffic
> > > > with forged outer IP header, this is only looking at the inner IP
> > > > header.
> > >
> > > what is the difference with the plain IP/TCP use-case?
> >
> > Not referring to the generic packet forging scenario. I refer to the
> > scenario that would allow to forward packets for any IPIP outer header
> > given the inner header finds a matching in the flowtable. I think that
> > needs to be sorted out.
>
> ack.
>
> Regards,
> Lorenzo
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