[PATCH RFC nf-next] netfilter: flowtable_offload: propagate CT mark to hardware offload path

[Lorenzo Bianconi <lorenzo@kernel.org>]

When a user-space process sets the Connection Tracking (CT) mark on a
flow via nft_ct or xt_CONNMARK, that mark should be visible to the
hardware offload path when the flow is accelerated through the flowtable
infrastructure.
Extend the flowtable offload attribute set to include the ct mark field
when it has been explicitly set on the conntrack entry.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 net/netfilter/nf_flow_table_offload.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index 002ec15d988b..d5fe35b1a647 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -679,6 +679,22 @@ static int flow_offload_decap_tunnel(const struct flow_offload *flow,
 	return 0;
 }
 
+static void nf_flow_rule_ct_meta_mark(const struct flow_offload *flow,
+				      struct nf_flow_rule *flow_rule)
+{
+#if IS_ENABLED(CONFIG_NF_CONNTRACK_MARK)
+	u32 mark = flow->ct ? READ_ONCE(flow->ct->mark) : 0;
+
+	if (mark) {
+		struct flow_action_entry *entry;
+
+		entry = flow_action_entry_next(flow_rule);
+		entry->id = FLOW_ACTION_CT_METADATA;
+		entry->ct_metadata.mark = mark;
+	}
+#endif /* IS_ENABLED(CONFIG_NF_CONNTRACK_MARK) */
+}
+
 static int
 nf_flow_rule_route_common(struct net *net, const struct flow_offload *flow,
 			  enum flow_offload_tuple_dir dir,
@@ -747,6 +763,8 @@ int nf_flow_rule_route_ipv4(struct net *net, struct flow_offload *flow,
 	if (nf_flow_rule_route_common(net, flow, dir, flow_rule) < 0)
 		return -1;
 
+	nf_flow_rule_ct_meta_mark(flow, flow_rule);
+
 	if (test_bit(NF_FLOW_SNAT, &flow->flags)) {
 		if (flow_offload_ipv4_snat(net, flow, dir, flow_rule) < 0 ||
 		    flow_offload_port_snat(net, flow, dir, flow_rule) < 0)
@@ -776,6 +794,8 @@ int nf_flow_rule_route_ipv6(struct net *net, struct flow_offload *flow,
 	if (nf_flow_rule_route_common(net, flow, dir, flow_rule) < 0)
 		return -1;
 
+	nf_flow_rule_ct_meta_mark(flow, flow_rule);
+
 	if (test_bit(NF_FLOW_SNAT, &flow->flags)) {
 		if (flow_offload_ipv6_snat(net, flow, dir, flow_rule) < 0 ||
 		    flow_offload_port_snat(net, flow, dir, flow_rule) < 0)

---
base-commit: 3f3a2aefbc661b837c8e344f944982d61c2ae037
change-id: 20260420-nft-flowtable-priority-6eef902d255a

Best regards,
-- 
Lorenzo Bianconi <lorenzo@kernel.org>