[PATCH RFC net-next] net: bridge: add BRIDGE_VLAN_INFO_DYNAMIC flag

[Luke Howard <lukeh@padl.com>]

Dynamic VLAN entries as specified in IEEE Std 802.1Q-2022,
Clause 8.8.5. These allow a user-space VLAN registration
protocol such as MVRP to mark a bridge's VLAN entries as
dynamic, so they can be distinguished from administratively
configured static entries.

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Luke Howard <lukeh@padl.com>
---
This patch adds support for Dynamic VLAN Entries, as specified
in 802.1Q. I have marked it as RFC as a similar patch to add
support for Dynamic Reservation Entries to the FDB was rejected
on the argument that the dynamic bit should be stored separately.

Our MVRP implementation [1] will use this flag if available.

[1] https://github.com/PADL/OpenSRP
---
 include/uapi/linux/if_bridge.h |  1 +
 net/bridge/br_netlink.c        |  6 ++++++
 net/bridge/br_vlan.c           | 18 ++++++++++++++----
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
index 21a700c02ef76..a3abbfe79694b 100644
--- a/include/uapi/linux/if_bridge.h
+++ b/include/uapi/linux/if_bridge.h
@@ -134,6 +134,7 @@ enum {
 #define BRIDGE_VLAN_INFO_RANGE_END	(1<<4) /* VLAN is end of vlan range */
 #define BRIDGE_VLAN_INFO_BRENTRY	(1<<5) /* Global bridge VLAN entry */
 #define BRIDGE_VLAN_INFO_ONLY_OPTS	(1<<6) /* Skip create/delete/flags */
+#define BRIDGE_VLAN_INFO_DYNAMIC	(1<<7) /* 802.1Q Dynamic VLAN Registration Entry */
 
 struct bridge_vlan_info {
 	__u16 flags;
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index b2cd4e39326d0..90f2e103f53d5 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -388,6 +388,9 @@ static int br_fill_ifvlaninfo_compressed(struct sk_buff *skb,
 		if (v->flags & BRIDGE_VLAN_INFO_UNTAGGED)
 			flags |= BRIDGE_VLAN_INFO_UNTAGGED;
 
+		if (v->flags & BRIDGE_VLAN_INFO_DYNAMIC)
+			flags |= BRIDGE_VLAN_INFO_DYNAMIC;
+
 		if (vid_range_start == 0) {
 			goto initvars;
 		} else if ((v->vid - vid_range_end) == 1 &&
@@ -440,6 +443,9 @@ static int br_fill_ifvlaninfo(struct sk_buff *skb,
 		if (v->flags & BRIDGE_VLAN_INFO_UNTAGGED)
 			vinfo.flags |= BRIDGE_VLAN_INFO_UNTAGGED;
 
+		if (v->flags & BRIDGE_VLAN_INFO_DYNAMIC)
+			vinfo.flags |= BRIDGE_VLAN_INFO_DYNAMIC;
+
 		if (nla_put(skb, IFLA_BRIDGE_VLAN_INFO,
 			    sizeof(vinfo), &vinfo))
 			goto nla_put_failure;
diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 5560afcaaca32..e6bc59e3a4c4f 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -54,9 +54,11 @@ static void __vlan_delete_pvid(struct net_bridge_vlan_group *vg, u16 vid)
 	vg->pvid = 0;
 }
 
-/* Update the BRIDGE_VLAN_INFO_PVID and BRIDGE_VLAN_INFO_UNTAGGED flags of @v.
- * If @commit is false, return just whether the BRIDGE_VLAN_INFO_PVID and
- * BRIDGE_VLAN_INFO_UNTAGGED bits of @flags would produce any change onto @v.
+/* Update the BRIDGE_VLAN_INFO_PVID, BRIDGE_VLAN_INFO_UNTAGGED and
+ * BRIDGE_VLAN_INFO_DYNAMIC flags of @v.
+ * If @commit is false, return just whether the BRIDGE_VLAN_INFO_PVID,
+ * BRIDGE_VLAN_INFO_UNTAGGED and BRIDGE_VLAN_INFO_DYNAMIC bits of @flags
+ * would produce any change onto @v.
  */
 static bool __vlan_flags_update(struct net_bridge_vlan *v, u16 flags,
 				bool commit)
@@ -71,7 +73,8 @@ static bool __vlan_flags_update(struct net_bridge_vlan *v, u16 flags,
 
 	/* check if anything would be changed on commit */
 	change = !!(flags & BRIDGE_VLAN_INFO_PVID) == !!(vg->pvid != v->vid) ||
-		 ((flags ^ v->flags) & BRIDGE_VLAN_INFO_UNTAGGED);
+		 ((flags ^ v->flags) & (BRIDGE_VLAN_INFO_UNTAGGED |
+					BRIDGE_VLAN_INFO_DYNAMIC));
 
 	if (!commit)
 		goto out;
@@ -86,6 +89,11 @@ static bool __vlan_flags_update(struct net_bridge_vlan *v, u16 flags,
 	else
 		v->flags &= ~BRIDGE_VLAN_INFO_UNTAGGED;
 
+	if (flags & BRIDGE_VLAN_INFO_DYNAMIC)
+		v->flags |= BRIDGE_VLAN_INFO_DYNAMIC;
+	else
+		v->flags &= ~BRIDGE_VLAN_INFO_DYNAMIC;
+
 out:
 	return change;
 }
@@ -1874,6 +1882,8 @@ static bool br_vlan_fill_vids(struct sk_buff *skb, u16 vid, u16 vid_range,
 		info.flags |= BRIDGE_VLAN_INFO_UNTAGGED;
 	if (flags & BRIDGE_VLAN_INFO_PVID)
 		info.flags |= BRIDGE_VLAN_INFO_PVID;
+	if (flags & BRIDGE_VLAN_INFO_DYNAMIC)
+		info.flags |= BRIDGE_VLAN_INFO_DYNAMIC;
 
 	if (nla_put(skb, BRIDGE_VLANDB_ENTRY_INFO, sizeof(info), &info))
 		goto out_err;

---
base-commit: 2bb62a85aff6d4c14a62a476dfabaada3c1cc014
change-id: 20260703-vlan-dynamic-entry-56a028e8990e

Best regards,
--  
Luke Howard <lukeh@padl.com>