Re: [PATCH v12 nf-next 7/7] netfilter: nft_flow_offload: Add bridgeflow to nft_flow_offload_eval()
From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: 2026-07-08 09:52:56
Also in:
bridge, netfilter-devel
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.
quoted hunk ↗ jump to hunk
Signed-off-by: Eric Woudstra <redacted> --- 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.
+ 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.
quoted hunk ↗ jump to hunk
+ 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.
quoted hunk ↗ jump to hunk
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