Subject: [PATCH v2 net-next 1/4] net: bridge: add fdb flag to extent locked port feature

From: Hans Schultz <[email-masked]>
Date: Thu, 17 Mar 2022 10:38:59 +0100

Add an intermediate state for clients behind a locked port to allow for
possible opening of the port for said clients. This feature corresponds
to the Mac-Auth and MAC Authentication Bypass (MAB) named features. The
latter defined by Cisco.
Only the kernel can set this FDB entry flag, while userspace can read
the flag and remove it by deleting the FDB entry.

Signed-off-by: Hans Schultz <[email-masked]>
---
 include/uapi/linux/neighbour.h |  1 +
 net/bridge/br_fdb.c            |  6 ++++++
 net/bridge/br_input.c          | 10 +++++++++-
 net/bridge/br_private.h        |  3 ++-
 4 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/neighbour.h b/include/uapi/linux/neighbour.h
index db05fb55055e..a2df3b9b2f68 100644
--- a/include/uapi/linux/neighbour.h
+++ b/include/uapi/linux/neighbour.h
@@ -51,6 +51,7 @@ enum {
 #define NTF_ROUTER	(1 << 7)
 /* Extended flags under NDA_FLAGS_EXT: */
 #define NTF_EXT_MANAGED	(1 << 0)
+#define NTF_EXT_LOCKED	(1 << 1)
 
 /*
  *	Neighbor Cache Entry States.
diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 6ccda68bd473..57ec559a85a7 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -105,6 +105,7 @@ static int fdb_fill_info(struct sk_buff *skb, const struct net_bridge *br,
 	struct nda_cacheinfo ci;
 	struct nlmsghdr *nlh;
 	struct ndmsg *ndm;
+	u8 ext_flags = 0;
 
 	nlh = nlmsg_put(skb, portid, seq, type, sizeof(*ndm), flags);
 	if (nlh == NULL)
@@ -125,11 +126,16 @@ static int fdb_fill_info(struct sk_buff *skb, const struct net_bridge *br,
 		ndm->ndm_flags |= NTF_EXT_LEARNED;
 	if (test_bit(BR_FDB_STICKY, &fdb->flags))
 		ndm->ndm_flags |= NTF_STICKY;
+	if (test_bit(BR_FDB_ENTRY_LOCKED, &fdb->flags))
+		ext_flags |= NTF_EXT_LOCKED;
 
 	if (nla_put(skb, NDA_LLADDR, ETH_ALEN, &fdb->key.addr))
 		goto nla_put_failure;
 	if (nla_put_u32(skb, NDA_MASTER, br->dev->ifindex))
 		goto nla_put_failure;
+	if (nla_put_u8(skb, NDA_FLAGS_EXT, ext_flags))
+		goto nla_put_failure;
+
 	ci.ndm_used	 = jiffies_to_clock_t(now - fdb->used);
 	ci.ndm_confirmed = 0;
 	ci.ndm_updated	 = jiffies_to_clock_t(now - fdb->updated);
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index e0c13fcc50ed..5ef25a496806 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -94,8 +94,16 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 			br_fdb_find_rcu(br, eth_hdr(skb)->h_source, vid);
 
 		if (!fdb_src || READ_ONCE(fdb_src->dst) != p ||
-		    test_bit(BR_FDB_LOCAL, &fdb_src->flags))
+		    test_bit(BR_FDB_LOCAL, &fdb_src->flags) ||
+		    test_bit(BR_FDB_ENTRY_LOCKED, &fdb_src->flags)) {
+			if (!fdb_src) {
+				unsigned long flags = 0;
+
+				set_bit(BR_FDB_ENTRY_LOCKED, &flags);
+				br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, flags);
+			}
 			goto drop;
+		}
 	}
 
 	nbp_switchdev_frame_mark(p, skb);
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 48bc61ebc211..f5a0b68c4857 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -248,7 +248,8 @@ enum {
 	BR_FDB_ADDED_BY_EXT_LEARN,
 	BR_FDB_OFFLOADED,
 	BR_FDB_NOTIFY,
-	BR_FDB_NOTIFY_INACTIVE
+	BR_FDB_NOTIFY_INACTIVE,
+	BR_FDB_ENTRY_LOCKED,
 };
 
 struct net_bridge_fdb_key {
-- 
2.30.2