On 7/8/26 11:52 AM, Pablo Neira Ayuso wrote:
> Hi,
>
> On Tue, Jul 07, 2026 at 11:10:45AM +0200, Eric Woudstra wrote:
>> Edit nft_flow_offload_eval() to make it possible to handle a flowtable of
>> the nft bridge family.
>>
>> Use nft_flow_offload_bridge_init() to fill the flow tuples. It uses
>> nft_dev_fill_bridge_path() in each direction.
>
> I decided to add a bit more boiler plate in my proposal to detach the
> inet and bridge flowtable dataplanes.
>
> More comments below.
>
>> Signed-off-by: Eric Woudstra <[email protected]>
>> ---
>> include/net/netfilter/nf_flow_table.h | 5 +
>> net/netfilter/nf_flow_table_path.c | 126 ++++++++++++++++++++++++++
>> net/netfilter/nft_flow_offload.c | 20 +++-
>> 3 files changed, 146 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/net/netfilter/nf_flow_table.h
>> b/include/net/netfilter/nf_flow_table.h
>> index 5c6e3b65ae85b..a109eda5250c7 100644
>> --- a/include/net/netfilter/nf_flow_table.h
>> +++ b/include/net/netfilter/nf_flow_table.h
>> @@ -305,6 +305,11 @@ nf_flow_table_offload_del_cb(struct nf_flowtable
>> *flow_table,
>> void flow_offload_route_init(struct flow_offload *flow,
>> struct nf_flow_route *route);
>>
>> +int flow_offload_bridge_init(struct flow_offload *flow,
>> + const struct nft_pktinfo *pkt,
>> + enum ip_conntrack_dir dir,
>> + struct nft_flowtable *ft);
>> +
>> int flow_offload_add(struct nf_flowtable *flow_table, struct flow_offload
>> *flow);
>> void flow_offload_refresh(struct nf_flowtable *flow_table,
>> struct flow_offload *flow, bool force);
>> diff --git a/net/netfilter/nf_flow_table_path.c
>> b/net/netfilter/nf_flow_table_path.c
>> index 2b6ebb594a9ee..cdd6a822cb811 100644
>> --- a/net/netfilter/nf_flow_table_path.c
>> +++ b/net/netfilter/nf_flow_table_path.c
>> @@ -1,6 +1,7 @@
>> // SPDX-License-Identifier: GPL-2.0-only
>> #include <linux/kernel.h>
>> #include <linux/module.h>
>> +#include <linux/if_vlan.h>
>> #include <linux/init.h>
>> #include <linux/etherdevice.h>
>> #include <linux/netlink.h>
>> @@ -365,3 +366,128 @@ int nft_flow_route(const struct nft_pktinfo *pkt,
>> const struct nf_conn *ct,
>> return -ENOENT;
>> }
>> EXPORT_SYMBOL_GPL(nft_flow_route);
>> +
>> +static int nft_dev_fill_bridge_path(struct flow_offload *flow,
>> + struct nft_flowtable *ft,
>> + enum ip_conntrack_dir dir,
>> + const struct net_device *src_dev,
>> + const struct net_device *dst_dev,
>> + unsigned char *src_ha,
>> + unsigned char *dst_ha)
>> +{
>> + struct flow_offload_tuple_rhash *th = flow->tuplehash;
>> + struct net_device_path_ctx ctx = {};
>> + struct net_device_path_stack stack;
>> + struct nft_forward_info info = {};
>> + int i, j = 0;
>> +
>> + for (i = th[dir].tuple.encap_num - 1; i >= 0 ; i--) {
>> + if (info.num_encaps >= NF_FLOW_TABLE_ENCAP_MAX)
>> + return -1;
>> +
>> + if (th[dir].tuple.in_vlan_ingress & BIT(i))
>> + continue;
>> +
>> + info.encap[info.num_encaps].id = th[dir].tuple.encap[i].id;
>> + info.encap[info.num_encaps].proto =
>> th[dir].tuple.encap[i].proto;
>> + info.num_encaps++;
>> +
>> + if (th[dir].tuple.encap[i].proto == htons(ETH_P_PPP_SES))
>> + continue;
>> +
>> + if (ctx.num_vlans >= NET_DEVICE_PATH_VLAN_MAX)
>> + return -1;
>> + ctx.vlan[ctx.num_vlans].id = th[dir].tuple.encap[i].id;
>> + ctx.vlan[ctx.num_vlans].proto = th[dir].tuple.encap[i].proto;
>> + ctx.num_vlans++;
>> + }
>
> I am not sure why this is needed, in my approach I simplified this,
> but maybe I broke bridge vlan filtering. I am not sure what test
> coverage you made.
>
This part is used for handling packets that are incoming with encaps.
Previously I got the encaps from the skb and stored them in
th[dir].tuple.encap. I understand you want to do this differently.
It is also why I'm starting in the opposite direction as in you patch-set.
The code above then reads th[dir].tuple.encap and starts filling info
and ctx with encaps. It also handles encaps marked with a
in_vlan_ingress bit. Once info and ctx are filled with the encaps from
the skb, it can continue with dev_fill_bridge_path().
My selftest script bridge_fastpath.sh tests this code thoroughly in many
different scenarios. Incoming vlan, q-in-q, ad, pppoe, pppoe-in-q. Also
on a dsa-port with the in_vlan_ingress bit set.
>> + ctx.dev = src_dev;
>> + ether_addr_copy(ctx.daddr, dst_ha);
>> +
>> + if (dev_fill_bridge_path(&ctx, &stack) < 0)
>> + return -1;
>> +
>> + nft_dev_path_info(&stack, &info, dst_ha, &ft->data);
>> +
>> + if (!info.indev || info.indev != dst_dev)
>> + return -1;
>> +
>> + th[!dir].tuple.iifidx = info.indev->ifindex;
>> + for (i = info.num_encaps - 1; i >= 0; i--) {
>> + th[!dir].tuple.encap[j].id = info.encap[i].id;
>> + th[!dir].tuple.encap[j].proto = info.encap[i].proto;
>> + if (info.ingress_vlans & BIT(i))
>> + th[!dir].tuple.in_vlan_ingress |= BIT(j);
>> + j++;
>> + }
>> + th[!dir].tuple.encap_num = info.num_encaps;
>> +
>> + th[dir].tuple.mtu = dst_dev->mtu;
>> + ether_addr_copy(th[dir].tuple.out.h_source, src_ha);
>> + ether_addr_copy(th[dir].tuple.out.h_dest, dst_ha);
>> + th[dir].tuple.out.ifidx = info.outdev->ifindex;
>> + th[dir].tuple.xmit_type = FLOW_OFFLOAD_XMIT_DIRECT;
>> +
>> + return 0;
>> +}
>> +
>> +int flow_offload_bridge_init(struct flow_offload *flow,
>> + const struct nft_pktinfo *pkt,
>> + enum ip_conntrack_dir dir,
>> + struct nft_flowtable *ft)
>> +{
>> + const struct net_device *in_dev, *out_dev;
>> + struct ethhdr *eth = eth_hdr(pkt->skb);
>> + struct flow_offload_tuple *tuple;
>> + int err, i = 0;
>> +
>> + in_dev = nft_in(pkt);
>> + if (!in_dev || !nft_flowtable_find_dev(in_dev, ft))
>> + return -1;
>> +
>> + out_dev = nft_out(pkt);
>> + if (!out_dev || !nft_flowtable_find_dev(out_dev, ft))
>> + return -1;
>> +
>> + tuple = &flow->tuplehash[!dir].tuple;
>> +
>> + if (skb_vlan_tag_present(pkt->skb)) {
>> + tuple->encap[i].id = skb_vlan_tag_get(pkt->skb);
>> + tuple->encap[i].proto = pkt->skb->vlan_proto;
>> + i++;
>> + }
>> +
>> + switch (eth_hdr(pkt->skb)->h_proto) {
>> + case htons(ETH_P_8021Q): {
>> + struct vlan_hdr *vhdr = (struct vlan_hdr
>> *)(skb_mac_header(pkt->skb)
>> + + sizeof(struct ethhdr));
>> + tuple->encap[i].id = ntohs(vhdr->h_vlan_TCI);
>> + tuple->encap[i].proto = htons(ETH_P_8021Q);
>> + i++;
>> + break;
>> + }
>> + case htons(ETH_P_PPP_SES): {
>> + struct pppoe_hdr *phdr = (struct pppoe_hdr
>> *)(skb_mac_header(pkt->skb)
>> + + sizeof(struct ethhdr));
>> +
>> + tuple->encap[i].id = ntohs(phdr->sid);
>> + tuple->encap[i].proto = htons(ETH_P_PPP_SES);
>> + i++;
>> + break;
>> + }
>> + }
>> + tuple->encap_num = i;
>
> I am not sure these lines above can work. The VLAN tag might be
> already gone by when the packet is observed from the bridge/forward
> hook. I think populating the encap fields of the tuple by using the
> observed packet is not good to go.
>
I have not experienced this, but I understand that this is no guarantee
that it does not happen at all.
>> + err = nft_dev_fill_bridge_path(flow, ft, !dir, out_dev, in_dev,
>> + eth->h_dest, eth->h_source);
>> + if (err < 0)
>> + return err;
>> +
>> + err = nft_dev_fill_bridge_path(flow, ft, dir, in_dev, out_dev,
>> + eth->h_source, eth->h_dest);
>> + if (err < 0)
>> + return err;
>> +
>> + return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(flow_offload_bridge_init);
>> diff --git a/net/netfilter/nft_flow_offload.c
>> b/net/netfilter/nft_flow_offload.c
>> index 0be62841155b6..d0d63ef7cecd5 100644
>> --- a/net/netfilter/nft_flow_offload.c
>> +++ b/net/netfilter/nft_flow_offload.c
>> @@ -53,6 +53,7 @@ static void nft_flow_offload_eval(const struct nft_expr
>> *expr,
>> {
>> struct nft_flow_offload *priv = nft_expr_priv(expr);
>> struct nf_flowtable *flowtable = &priv->flowtable->data;
>> + bool routing = flowtable->type->family != NFPROTO_BRIDGE;
>> struct tcphdr _tcph, *tcph = NULL;
>> struct nf_flow_route route = {};
>> enum ip_conntrack_info ctinfo;
>> @@ -109,14 +110,21 @@ static void nft_flow_offload_eval(const struct
>> nft_expr *expr,
>> goto out;
>>
>> dir = CTINFO2DIR(ctinfo);
>> - if (nft_flow_route(pkt, ct, &route, dir, priv->flowtable) < 0)
>> - goto err_flow_route;
>> + if (routing) {
>> + if (nft_flow_route(pkt, ct, &route, dir, priv->flowtable) < 0)
>> + goto err_flow_route;
>> + }
>
> As said, I am leaning towards adding a bit more boilerplate code to
> separate the bridge and inet flowtable datapaths.
>
>> flow = flow_offload_alloc(ct);
>> if (!flow)
>> goto err_flow_alloc;
>>
>> - flow_offload_route_init(flow, &route);
>> + if (routing)
>> + flow_offload_route_init(flow, &route);
>> + else
>> + if (flow_offload_bridge_init(flow, pkt, dir, priv->flowtable) <
>> 0)
>> + goto err_flow_add;
>> +
>> if (tcph)
>> flow_offload_ct_tcp(ct);
>>
>> @@ -164,8 +172,10 @@ static void nft_flow_offload_eval(const struct nft_expr
>> *expr,
>> err_flow_add:
>> flow_offload_free(flow);
>> err_flow_alloc:
>> - dst_release(route.tuple[dir].dst);
>> - dst_release(route.tuple[!dir].dst);
>> + if (routing) {
>> + dst_release(route.tuple[dir].dst);
>> + dst_release(route.tuple[!dir].dst);
>> + }
>> err_flow_route:
>> clear_bit(IPS_OFFLOAD_BIT, &ct->status);
>> out:
>> --
>> 2.53.0
>>
