> On Fri, Jun 27, 2025 at 02:45:28PM +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):
> >
> > 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@NONE: <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
> > }
> > }
>
> Is there a proof that this accelerates forwarding?
I reproduced the scenario described above using veths (something similar to
what is done in nft_flowtable.sh) and I got the following results:
- flowtable configured as above between the two router interfaces
- TCP stream between client and server going via the IPIP tunnel
- TCP stream transmitted into the IPIP tunnel:
- net-next: ~41Gbps
- net-next + IPIP flowtbale support: ~40Gbps
- TCP stream received from the IPIP tunnel:
- net-next: ~35Gbps
- net-next + IPIP flowtbale support: ~49Gbps
>
> > Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
> > ---
> > net/ipv4/ipip.c | 21 +++++++++++++++++++++
> > net/netfilter/nf_flow_table_ip.c | 28 ++++++++++++++++++++++++++--
> > 2 files changed, 47 insertions(+), 2 deletions(-)
> >
[...]
> > static bool nf_flow_skb_encap_protocol(struct sk_buff *skb, __be16 proto,
> > u32 *offset)
> > {
> > struct vlan_ethhdr *veth;
> > __be16 inner_proto;
> > + u16 size;
> >
> > switch (skb->protocol) {
> > + case htons(ETH_P_IP):
> > + if (nf_flow_ip4_encap_proto(skb, &size))
> > + *offset += size;
>
> This is blindly skipping the outer IP header.
Do you mean we are supposed to validate the outer IP header performing the
sanity checks done in nf_flow_tuple_ip()?
Regards,
Lorenzo
>
> > + return true;
> > case htons(ETH_P_8021Q):
> > if (!pskb_may_pull(skb, skb_mac_offset(skb) + sizeof(*veth)))
> > return false;
> > @@ -310,6 +328,7 @@ static void nf_flow_encap_pop(struct sk_buff *skb,
> > struct flow_offload_tuple_rhash *tuplehash)
> > {
> > struct vlan_hdr *vlan_hdr;
> > + u16 size;
> > int i;
> >
> > for (i = 0; i < tuplehash->tuple.encap_num; i++) {
> > @@ -331,6 +350,12 @@ static void nf_flow_encap_pop(struct sk_buff *skb,
> > break;
> > }
> > }
> > +
> > + if (skb->protocol == htons(ETH_P_IP) &&
> > + nf_flow_ip4_encap_proto(skb, &size)) {
> > + skb_pull(skb, size);
> > + skb_reset_network_header(skb);
> > + }
>
> I have a similar patch from 2023, I think I keep somewhere in my trees.
>
> > }
> >
> > static unsigned int nf_flow_queue_xmit(struct net *net, struct sk_buff *skb,
> > @@ -357,8 +382,7 @@ nf_flow_offload_lookup(struct nf_flowtable_ctx *ctx,
> > {
> > struct flow_offload_tuple tuple = {};
> >
> > - if (skb->protocol != htons(ETH_P_IP) &&
> > - !nf_flow_skb_encap_protocol(skb, htons(ETH_P_IP), &ctx->offset))
> > + if (!nf_flow_skb_encap_protocol(skb, htons(ETH_P_IP), &ctx->offset))
> > return NULL;
> >
> > if (nf_flow_tuple_ip(ctx, skb, &tuple) < 0)
> >
> > --
> > 2.50.0
> >
>
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