[PATCH v7 net-next 1/9] net: bridge: add locked entry fdb flag to extend locked port feature

From: Hans J. Schultz
Date: Sun Oct 09 2022 - 13:41:38 EST

Add an intermediate state for clients behind a locked port to allow for
possible opening of the port for said clients. The clients mac address
will be added with the locked flag set, denying access through the port
for the mac address, but also creating a new FDB add event giving
userspace daemons the ability to unlock the mac address. 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 replacing or deleting the FDB entry.

Locked entries will age out with the set bridge ageing time.

Signed-off-by: Hans J. Schultz <netdev@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/if_bridge.h | 1 +
include/uapi/linux/if_link.h | 1 +
include/uapi/linux/neighbour.h | 7 ++++++-
net/bridge/br_fdb.c | 22 ++++++++++++++++++++++
net/bridge/br_input.c | 15 +++++++++++++--
net/bridge/br_netlink.c | 12 +++++++++++-
net/bridge/br_private.h | 3 ++-
net/core/rtnetlink.c | 9 +++++++++
8 files changed, 65 insertions(+), 5 deletions(-)

diff --git a/include/linux/if_bridge.h b/include/linux/if_bridge.h
index d62ef428e3aa..1668ac4d7adc 100644
--- a/include/linux/if_bridge.h
+++ b/include/linux/if_bridge.h
@@ -59,6 +59,7 @@ struct br_ip_list {
#define BR_MRP_LOST_IN_CONT BIT(19)
#define BR_TX_FWD_OFFLOAD BIT(20)
#define BR_PORT_LOCKED BIT(21)
+#define BR_PORT_MAB BIT(22)

#define BR_DEFAULT_AGEING_TIME (300 * HZ)

diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 5e7a1041df3a..d92b3f79eba3 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -561,6 +561,7 @@ enum {
IFLA_BRPORT_MCAST_EHT_HOSTS_LIMIT,
IFLA_BRPORT_MCAST_EHT_HOSTS_CNT,
IFLA_BRPORT_LOCKED,
+ IFLA_BRPORT_MAB,
__IFLA_BRPORT_MAX
};
#define IFLA_BRPORT_MAX (__IFLA_BRPORT_MAX - 1)
diff --git a/include/uapi/linux/neighbour.h b/include/uapi/linux/neighbour.h
index a998bf761635..4dda051b0ba8 100644
--- a/include/uapi/linux/neighbour.h
+++ b/include/uapi/linux/neighbour.h
@@ -52,7 +52,8 @@ enum {
#define NTF_STICKY (1 << 6)
#define NTF_ROUTER (1 << 7)
/* Extended flags under NDA_FLAGS_EXT: */
-#define NTF_EXT_MANAGED (1 << 0)
+#define NTF_EXT_MANAGED (1 << 0)
+#define NTF_EXT_LOCKED (1 << 1)

/*
* Neighbor Cache Entry States.
@@ -86,6 +87,10 @@ enum {
* NTF_EXT_MANAGED flagged neigbor entries are managed by the kernel on behalf
* of a user space control plane, and automatically refreshed so that (if
* possible) they remain in NUD_REACHABLE state.
+ *
+ * NTF_EXT_LOCKED flagged FDB entries are placeholder entries used with the
+ * locked port feature, that ensures that an entry exists while at the same
+ * time dropping packets on ingress with src MAC and VID matching the entry.
*/

struct nda_cacheinfo {
diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index e7f4fccb6adb..2cf695ee61c5 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;
+ u32 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_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_u32(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);
@@ -171,6 +177,7 @@ static inline size_t fdb_nlmsg_size(void)
return NLMSG_ALIGN(sizeof(struct ndmsg))
+ nla_total_size(ETH_ALEN) /* NDA_LLADDR */
+ nla_total_size(sizeof(u32)) /* NDA_MASTER */
+ + nla_total_size(sizeof(u32)) /* NDA_FLAGS_EXT */
+ nla_total_size(sizeof(u16)) /* NDA_VLAN */
+ nla_total_size(sizeof(struct nda_cacheinfo))
+ nla_total_size(0) /* NDA_FDB_EXT_ATTRS */
@@ -879,6 +886,9 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
&fdb->flags)))
clear_bit(BR_FDB_ADDED_BY_EXT_LEARN,
&fdb->flags);
+ /* Allow roaming from unauthorized port to authorized port */
+ if (unlikely(test_bit(BR_FDB_LOCKED, &fdb->flags)))
+ clear_bit(BR_FDB_LOCKED, &fdb->flags);
}

if (unlikely(test_bit(BR_FDB_ADDED_BY_USER, &flags)))
@@ -1082,6 +1092,9 @@ static int fdb_add_entry(struct net_bridge *br, struct net_bridge_port *source,
modified = true;
}

+ if (test_and_clear_bit(BR_FDB_LOCKED, &fdb->flags))
+ modified = true;
+
if (fdb_handle_notify(fdb, notify))
modified = true;

@@ -1150,6 +1163,7 @@ int br_fdb_add(struct ndmsg *ndm, struct nlattr *tb[],
struct net_bridge_port *p = NULL;
struct net_bridge_vlan *v;
struct net_bridge *br = NULL;
+ u32 ext_flags = 0;
int err = 0;

trace_br_fdb_add(ndm, dev, addr, vid, nlh_flags);
@@ -1178,6 +1192,14 @@ int br_fdb_add(struct ndmsg *ndm, struct nlattr *tb[],
vg = nbp_vlan_group(p);
}

+ if (tb[NDA_FLAGS_EXT])
+ ext_flags = nla_get_u32(tb[NDA_FLAGS_EXT]);
+
+ if (ext_flags & NTF_EXT_LOCKED) {
+ pr_info("bridge: RTM_NEWNEIGH has invalid extended flags\n");
+ return -EINVAL;
+ }
+
if (tb[NDA_FDB_EXT_ATTRS]) {
attr = tb[NDA_FDB_EXT_ATTRS];
err = nla_parse_nested(nfea_tb, NFEA_MAX, attr,
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 68b3e850bcb9..068fced7693c 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -109,9 +109,20 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
struct net_bridge_fdb_entry *fdb_src =
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))
+ if (!fdb_src) {
+ unsigned long flags = 0;
+
+ if (p->flags & BR_PORT_MAB) {
+ __set_bit(BR_FDB_LOCKED, &flags);
+ br_fdb_update(br, p, eth_hdr(skb)->h_source,
+ vid, flags);
+ }
goto drop;
+ } else if (READ_ONCE(fdb_src->dst) != p ||
+ test_bit(BR_FDB_LOCAL, &fdb_src->flags) ||
+ test_bit(BR_FDB_LOCKED, &fdb_src->flags)) {
+ goto drop;
+ }
}

nbp_switchdev_frame_mark(p, skb);
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 5aeb3646e74c..4b190abc11bb 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -188,6 +188,7 @@ static inline size_t br_port_info_size(void)
+ nla_total_size(1) /* IFLA_BRPORT_NEIGH_SUPPRESS */
+ nla_total_size(1) /* IFLA_BRPORT_ISOLATED */
+ nla_total_size(1) /* IFLA_BRPORT_LOCKED */
+ + nla_total_size(1) /* IFLA_BRPORT_MAB */
+ nla_total_size(sizeof(struct ifla_bridge_id)) /* IFLA_BRPORT_ROOT_ID */
+ nla_total_size(sizeof(struct ifla_bridge_id)) /* IFLA_BRPORT_BRIDGE_ID */
+ nla_total_size(sizeof(u16)) /* IFLA_BRPORT_DESIGNATED_PORT */
@@ -274,7 +275,8 @@ static int br_port_fill_attrs(struct sk_buff *skb,
nla_put_u8(skb, IFLA_BRPORT_MRP_IN_OPEN,
!!(p->flags & BR_MRP_LOST_IN_CONT)) ||
nla_put_u8(skb, IFLA_BRPORT_ISOLATED, !!(p->flags & BR_ISOLATED)) ||
- nla_put_u8(skb, IFLA_BRPORT_LOCKED, !!(p->flags & BR_PORT_LOCKED)))
+ nla_put_u8(skb, IFLA_BRPORT_LOCKED, !!(p->flags & BR_PORT_LOCKED)) ||
+ nla_put_u8(skb, IFLA_BRPORT_MAB, !!(p->flags & BR_PORT_MAB)))
return -EMSGSIZE;

timerval = br_timer_value(&p->message_age_timer);
@@ -876,6 +878,7 @@ static const struct nla_policy br_port_policy[IFLA_BRPORT_MAX + 1] = {
[IFLA_BRPORT_NEIGH_SUPPRESS] = { .type = NLA_U8 },
[IFLA_BRPORT_ISOLATED] = { .type = NLA_U8 },
[IFLA_BRPORT_LOCKED] = { .type = NLA_U8 },
+ [IFLA_BRPORT_MAB] = { .type = NLA_U8 },
[IFLA_BRPORT_BACKUP_PORT] = { .type = NLA_U32 },
[IFLA_BRPORT_MCAST_EHT_HOSTS_LIMIT] = { .type = NLA_U32 },
};
@@ -943,6 +946,13 @@ static int br_setport(struct net_bridge_port *p, struct nlattr *tb[],
br_set_port_flag(p, tb, IFLA_BRPORT_NEIGH_SUPPRESS, BR_NEIGH_SUPPRESS);
br_set_port_flag(p, tb, IFLA_BRPORT_ISOLATED, BR_ISOLATED);
br_set_port_flag(p, tb, IFLA_BRPORT_LOCKED, BR_PORT_LOCKED);
+ br_set_port_flag(p, tb, IFLA_BRPORT_MAB, BR_PORT_MAB);
+
+ if (!(p->flags & BR_PORT_LOCKED) && (p->flags & BR_PORT_MAB)) {
+ NL_SET_ERR_MSG(extack, "MAB cannot be enabled when port is unlocked");
+ p->flags = old_flags;
+ return -EINVAL;
+ }

changed_mask = old_flags ^ p->flags;

diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 06e5f6faa431..4ce8b8e5ae0b 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -251,7 +251,8 @@ enum {
BR_FDB_ADDED_BY_EXT_LEARN,
BR_FDB_OFFLOADED,
BR_FDB_NOTIFY,
- BR_FDB_NOTIFY_INACTIVE
+ BR_FDB_NOTIFY_INACTIVE,
+ BR_FDB_LOCKED,
};

struct net_bridge_fdb_key {
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 74864dc46a7e..8008ceb45605 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -4035,6 +4035,7 @@ int ndo_dflt_fdb_add(struct ndmsg *ndm,
const unsigned char *addr, u16 vid,
u16 flags)
{
+ __u32 ext_flags = 0;
int err = -EINVAL;

/* If aging addresses are supported device will need to
@@ -4050,6 +4051,14 @@ int ndo_dflt_fdb_add(struct ndmsg *ndm,
return err;
}

+ if (tb[NDA_FLAGS_EXT])
+ ext_flags = nla_get_u32(tb[NDA_FLAGS_EXT]);
+
+ if (ext_flags & NTF_EXT_LOCKED) {
+ netdev_info(dev, "invalid flags given to default FDB implementation\n");
+ return err;
+ }
+
if (is_unicast_ether_addr(addr) || is_link_local_ether_addr(addr))
err = dev_uc_add_excl(dev, addr);
else if (is_multicast_ether_addr(addr))
--
2.34.1