Linux Ethernet Bridging - Sep 2022 - [Bridge] [PATCH iproute2-next 2/2] bridge: fdb: enable FDB blackhole feature

The MAB feature can be enabled on a locked port with the command:
bridge link set dev <DEV> mab on

Signed-off-by: Hans Schultz <netdev at kapio-technology.com>
---
 bridge/fdb.c                   | 17 +++++++++++++++--
 bridge/link.c                  | 21 ++++++++++++++++++---
 include/uapi/linux/if_link.h   |  1 +
 include/uapi/linux/neighbour.h |  7 ++++++-
 ip/iplink_bridge_slave.c       | 16 +++++++++++++---
 man/man8/bridge.8              | 10 ++++++++++
 man/man8/ip-link.8.in          |  8 ++++++++
 7 files changed, 71 insertions(+), 9 deletions(-)

diff --git a/bridge/fdb.c b/bridge/fdb.c
index 5f71bde0..0fbe9bd3 100644
--- a/bridge/fdb.c
+++ b/bridge/fdb.c
@@ -93,7 +93,7 @@ static int state_a2n(unsigned int *s, const char *arg)
 	return 0;
 }
 
-static void fdb_print_flags(FILE *fp, unsigned int flags)
+static void fdb_print_flags(FILE *fp, unsigned int flags, __u8 ext_flags)
 {
 	open_json_array(PRINT_JSON,
 			is_json_context() ?  "flags" : "");
@@ -116,6 +116,9 @@ static void fdb_print_flags(FILE *fp, unsigned int flags)
 	if (flags & NTF_STICKY)
 		print_string(PRINT_ANY, NULL, "%s ", "sticky");
 
+	if (ext_flags & NTF_EXT_LOCKED)
+		print_string(PRINT_ANY, NULL, "%s ", "locked");
+
 	close_json_array(PRINT_JSON, NULL);
 }
 
@@ -144,6 +147,7 @@ int print_fdb(struct nlmsghdr *n, void *arg)
 	struct ndmsg *r = NLMSG_DATA(n);
 	int len = n->nlmsg_len;
 	struct rtattr *tb[NDA_MAX+1];
+	__u32 ext_flags = 0;
 	__u16 vid = 0;
 
 	if (n->nlmsg_type != RTM_NEWNEIGH && n->nlmsg_type !=
RTM_DELNEIGH) {
@@ -170,6 +174,9 @@ int print_fdb(struct nlmsghdr *n, void *arg)
 	parse_rtattr(tb, NDA_MAX, NDA_RTA(r),
 		     n->nlmsg_len - NLMSG_LENGTH(sizeof(*r)));
 
+	if (tb[NDA_FLAGS_EXT])
+		ext_flags = rta_getattr_u32(tb[NDA_FLAGS_EXT]);
+
 	if (tb[NDA_VLAN])
 		vid = rta_getattr_u16(tb[NDA_VLAN]);
 
@@ -266,7 +273,7 @@ int print_fdb(struct nlmsghdr *n, void *arg)
 	if (show_stats && tb[NDA_CACHEINFO])
 		fdb_print_stats(fp, RTA_DATA(tb[NDA_CACHEINFO]));
 
-	fdb_print_flags(fp, r->ndm_flags);
+	fdb_print_flags(fp, r->ndm_flags, ext_flags);
 
 
 	if (tb[NDA_MASTER])
@@ -414,6 +421,7 @@ static int fdb_modify(int cmd, int flags, int argc, char
**argv)
 	char *endptr;
 	short vid = -1;
 	__u32 nhid = 0;
+	__u32 ext_flags = 0;
 
 	while (argc > 0) {
 		if (strcmp(*argv, "dev") == 0) {
@@ -527,6 +535,11 @@ static int fdb_modify(int cmd, int flags, int argc, char
**argv)
 	if (dst_ok)
 		addattr_l(&req.n, sizeof(req), NDA_DST, &dst.data, dst.bytelen);
 
+	if (ext_flags &&
+	    addattr_l(&req.n, sizeof(req), NDA_FLAGS_EXT, &ext_flags,
+		      sizeof(ext_flags)) < 0)
+		return -1;
+
 	if (vid >= 0)
 		addattr16(&req.n, sizeof(req), NDA_VLAN, vid);
 	if (nhid > 0)
diff --git a/bridge/link.c b/bridge/link.c
index 3810fa04..dd69d7c3 100644
--- a/bridge/link.c
+++ b/bridge/link.c
@@ -181,9 +181,14 @@ static void print_protinfo(FILE *fp, struct rtattr *attr)
 		if (prtb[IFLA_BRPORT_ISOLATED])
 			print_on_off(PRINT_ANY, "isolated", "isolated %s ",
 				     rta_getattr_u8(prtb[IFLA_BRPORT_ISOLATED]));
-		if (prtb[IFLA_BRPORT_LOCKED])
-			print_on_off(PRINT_ANY, "locked", "locked %s ",
-				     rta_getattr_u8(prtb[IFLA_BRPORT_LOCKED]));
+		if (prtb[IFLA_BRPORT_LOCKED]) {
+			if (prtb[IFLA_BRPORT_MAB] && rta_getattr_u8(prtb[IFLA_BRPORT_MAB]))
+				print_on_off(PRINT_ANY, "locked mab", "locked mab %s ",
+					     rta_getattr_u8(prtb[IFLA_BRPORT_LOCKED]));
+			else
+				print_on_off(PRINT_ANY, "locked", "locked %s ",
+					     rta_getattr_u8(prtb[IFLA_BRPORT_LOCKED]));
+		}
 	} else
 		print_stp_state(rta_getattr_u8(attr));
 }
@@ -281,6 +286,7 @@ static void usage(void)
 		"                               [ vlan_tunnel {on | off} ]\n"
 		"                               [ isolated {on | off} ]\n"
 		"                               [ locked {on | off} ]\n"
+		"                               [ mab {on | off} ]\n"
 		"                               [ hwmode {vepa | veb} ]\n"
 		"                               [ backup_port DEVICE ] [ nobackup_port
]\n"
 		"                               [ self ] [ master ]\n"
@@ -312,6 +318,7 @@ static int brlink_modify(int argc, char **argv)
 	__s8 bcast_flood = -1;
 	__s8 mcast_to_unicast = -1;
 	__s8 locked = -1;
+	__s8 macauth = -1;
 	__s8 isolated = -1;
 	__s8 hairpin = -1;
 	__s8 bpdu_guard = -1;
@@ -437,6 +444,11 @@ static int brlink_modify(int argc, char **argv)
 			locked = parse_on_off("locked", *argv, &ret);
 			if (ret)
 				return ret;
+		} else if (strcmp(*argv, "mab") == 0) {
+			NEXT_ARG();
+			macauth = parse_on_off("mab", *argv, &ret);
+			if (ret)
+				return ret;
 		} else if (strcmp(*argv, "backup_port") == 0) {
 			NEXT_ARG();
 			backup_port_idx = ll_name_to_index(*argv);
@@ -520,6 +532,9 @@ static int brlink_modify(int argc, char **argv)
 	if (locked >= 0)
 		addattr8(&req.n, sizeof(req), IFLA_BRPORT_LOCKED, locked);
 
+	if (macauth >= 0)
+		addattr8(&req.n, sizeof(req), IFLA_BRPORT_MAB, macauth);
+
 	if (backup_port_idx != -1)
 		addattr32(&req.n, sizeof(req), IFLA_BRPORT_BACKUP_PORT,
 			  backup_port_idx);
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 7494cffb..58a002de 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -559,6 +559,7 @@ 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 a998bf76..4dda051b 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/ip/iplink_bridge_slave.c b/ip/iplink_bridge_slave.c
index 98d17213..0c0894eb 100644
--- a/ip/iplink_bridge_slave.c
+++ b/ip/iplink_bridge_slave.c
@@ -44,6 +44,7 @@ static void print_explain(FILE *f)
 		"			[ vlan_tunnel {on | off} ]\n"
 		"			[ isolated {on | off} ]\n"
 		"			[ locked {on | off} ]\n"
+		"                       [ mab {on | off} ]\n"
 		"			[ backup_port DEVICE ] [ nobackup_port ]\n"
 	);
 }
@@ -284,9 +285,14 @@ static void bridge_slave_print_opt(struct link_util *lu,
FILE *f,
 		print_on_off(PRINT_ANY, "isolated", "isolated %s ",
 			     rta_getattr_u8(tb[IFLA_BRPORT_ISOLATED]));
 
-	if (tb[IFLA_BRPORT_LOCKED])
-		print_on_off(PRINT_ANY, "locked", "locked %s ",
-			     rta_getattr_u8(tb[IFLA_BRPORT_LOCKED]));
+	if (tb[IFLA_BRPORT_LOCKED]) {
+		if (tb[IFLA_BRPORT_MAB] && rta_getattr_u8(tb[IFLA_BRPORT_MAB]))
+			print_on_off(PRINT_ANY, "locked mab", "locked mab %s ",
+				     rta_getattr_u8(tb[IFLA_BRPORT_LOCKED]));
+		else
+			print_on_off(PRINT_ANY, "locked", "locked %s ",
+				     rta_getattr_u8(tb[IFLA_BRPORT_LOCKED]));
+	}
 
 	if (tb[IFLA_BRPORT_BACKUP_PORT]) {
 		int backup_p = rta_getattr_u32(tb[IFLA_BRPORT_BACKUP_PORT]);
@@ -411,6 +417,10 @@ static int bridge_slave_parse_opt(struct link_util *lu, int
argc, char **argv,
 			NEXT_ARG();
 			bridge_slave_parse_on_off("locked", *argv, n,
 						  IFLA_BRPORT_LOCKED);
+		} else if (matches(*argv, "mab") == 0) {
+			NEXT_ARG();
+			bridge_slave_parse_on_off("mab", *argv, n,
+						  IFLA_BRPORT_MAB);
 		} else if (matches(*argv, "backup_port") == 0) {
 			int ifindex;
 
diff --git a/man/man8/bridge.8 b/man/man8/bridge.8
index d4df772e..40250477 100644
--- a/man/man8/bridge.8
+++ b/man/man8/bridge.8
@@ -54,6 +54,7 @@ bridge \- show / manipulate bridge addresses and devices
 .BR vlan_tunnel " { " on " | " off " } ] [ "
 .BR isolated " { " on " | " off " } ] [ "
 .BR locked " { " on " | " off " } ] [ "
+.BR mab " { " on " | " off " } ] [ "
 .B backup_port
 .IR  DEVICE " ] ["
 .BR nobackup_port " ] [ "
@@ -580,6 +581,15 @@ The common use is that hosts are allowed access through
authentication
 with the IEEE 802.1X protocol or based on whitelists or like setups.
 By default this flag is off.
 
+.TP
+.RB "mab on " or " mab off "
+Enables or disables the MAB/MacAuth feature. This feature can only be
+activated on a port that is in locked mode, and when enabled it extends the
+locked port feature so that MAC address can get access through a locked
+port based on acceptlists, thus it is a much simpler procedure for a
+device to become authorized than f.ex. the 802.1X protocol, and is used
+for devices that are not capable of password or crypto based authorization
+methods.
 
 .TP
 .BI backup_port " DEVICE"
diff --git a/man/man8/ip-link.8.in b/man/man8/ip-link.8.in
index fc9d62fc..187ca7ca 100644
--- a/man/man8/ip-link.8.in
+++ b/man/man8/ip-link.8.in
@@ -2454,6 +2454,9 @@ the following additional arguments are supported:
 .BR isolated " { " on " | " off " }"
 ] [
 .BR locked " { " on " | " off " }"
+] [
+.BR mab " { " on " | " off " }"
+] [
 .BR backup_port " DEVICE"
 ] [
 .BR nobackup_port " ]"
@@ -2560,6 +2563,11 @@ default this flag is off.
 behind the port cannot communicate through the port unless a FDB entry
 representing the host is in the FDB. By default this flag is off.
 
+.BR mab " { " on " | " off " }"
+- enables or disables the MAB/MacAuth feature on a locked port. It is
+thus possible for a device to gain authorization on a locked port based
+on acceptlists.
+
 .BI backup_port " DEVICE"
 - if the port loses carrier all traffic will be redirected to the
 configured backup port
-- 
2.34.1

Block traffic to a specific host with the command:
bridge fdb add <MAC> vlan <vid> dev br0 blackhole

The blackhole FDB entries can be added, deleted and replaced with
ordinary FDB entries.

Signed-off-by: Hans Schultz <netdev at kapio-technology.com>
---
 bridge/fdb.c                   | 7 ++++++-
 include/uapi/linux/neighbour.h | 4 ++++
 man/man8/bridge.8              | 6 ++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/bridge/fdb.c b/bridge/fdb.c
index 0fbe9bd3..2160f1c2 100644
--- a/bridge/fdb.c
+++ b/bridge/fdb.c
@@ -38,7 +38,7 @@ static void usage(void)
 	fprintf(stderr,
 		"Usage: bridge fdb { add | append | del | replace } ADDR dev DEV\n"
 		"              [ self ] [ master ] [ use ] [ router ] [ extern_learn
]\n"
-		"              [ sticky ] [ local | static | dynamic ] [ vlan VID
]\n"
+		"              [ sticky ] [ local | static | dynamic ] [blackhole] [
vlan VID ]\n"
 		"              { [ dst IPADDR ] [ port PORT] [ vni VNI ] | [ nhid NHID ]
}\n"
 		"	       [ via DEV ] [ src_vni VNI ]\n"
 		"       bridge fdb [ show [ br BRDEV ] [ brport DEV ] [ vlan VID
]\n"
@@ -116,6 +116,9 @@ static void fdb_print_flags(FILE *fp, unsigned int flags,
__u8 ext_flags)
 	if (flags & NTF_STICKY)
 		print_string(PRINT_ANY, NULL, "%s ", "sticky");
 
+	if (ext_flags & NTF_EXT_BLACKHOLE)
+		print_string(PRINT_ANY, NULL, "%s ", "blackhole");
+
 	if (ext_flags & NTF_EXT_LOCKED)
 		print_string(PRINT_ANY, NULL, "%s ", "locked");
 
@@ -493,6 +496,8 @@ static int fdb_modify(int cmd, int flags, int argc, char
**argv)
 			req.ndm.ndm_flags |= NTF_EXT_LEARNED;
 		} else if (matches(*argv, "sticky") == 0) {
 			req.ndm.ndm_flags |= NTF_STICKY;
+		} else if (matches(*argv, "blackhole") == 0) {
+			ext_flags |= NTF_EXT_BLACKHOLE;
 		} else {
 			if (strcmp(*argv, "to") == 0)
 				NEXT_ARG();
diff --git a/include/uapi/linux/neighbour.h b/include/uapi/linux/neighbour.h
index 4dda051b..cc7d540e 100644
--- a/include/uapi/linux/neighbour.h
+++ b/include/uapi/linux/neighbour.h
@@ -54,6 +54,7 @@ enum {
 /* Extended flags under NDA_FLAGS_EXT: */
 #define NTF_EXT_MANAGED		(1 << 0)
 #define NTF_EXT_LOCKED		(1 << 1)
+#define NTF_EXT_BLACKHOLE	(1 << 2)
 
 /*
  *	Neighbor Cache Entry States.
@@ -91,6 +92,9 @@ enum {
  * 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.
+ *
+ * NTF_EXT_BLACKHOLE flagged FDB entries ensure that no forwarding is allowed
+ * from any port to the destination MAC, VID pair associated with it.
  */
 
 struct nda_cacheinfo {
diff --git a/man/man8/bridge.8 b/man/man8/bridge.8
index 40250477..af2e7db2 100644
--- a/man/man8/bridge.8
+++ b/man/man8/bridge.8
@@ -699,6 +699,12 @@ controller learnt dynamic entry. Kernel will not age such
an entry.
 - this entry will not change its port due to learning.
 .sp
 
+.B blackhole
+- this is an entry that denies all forwarding from any port to a destination
+matching the entry. It can be added by userspace, but the flag is mostly set
+from a hardware driver.
+.sp
+
 .in -8
 The next command line parameters apply only
 when the specified device
-- 
2.34.1

On Thu, Sep 29, 2022 at 05:21:36PM +0200, Hans Schultz
wrote:
> The MAB feature can be enabled on a locked port with the command:
> bridge link set dev <DEV> mab on
Please provide regular and JSON output in the commit message.
> 
> Signed-off-by: Hans Schultz <netdev at kapio-technology.com>
> ---
>  bridge/fdb.c                   | 17 +++++++++++++++--
>  bridge/link.c                  | 21 ++++++++++++++++++---
>  include/uapi/linux/if_link.h   |  1 +
>  include/uapi/linux/neighbour.h |  7 ++++++-
IIRC, in the past David asked to either not send the uAPI files or send
them as a first patch which he then uses as a hint to sync the files
himself.
>  ip/iplink_bridge_slave.c       | 16 +++++++++++++---
>  man/man8/bridge.8              | 10 ++++++++++
>  man/man8/ip-link.8.in          |  8 ++++++++
>  7 files changed, 71 insertions(+), 9 deletions(-)
> 
> diff --git a/bridge/fdb.c b/bridge/fdb.c
> index 5f71bde0..0fbe9bd3 100644
> --- a/bridge/fdb.c
> +++ b/bridge/fdb.c
> @@ -93,7 +93,7 @@ static int state_a2n(unsigned int *s, const char *arg)
>  	return 0;
>  }
>  
> -static void fdb_print_flags(FILE *fp, unsigned int flags)
> +static void fdb_print_flags(FILE *fp, unsigned int flags, __u8 ext_flags)
>  {
>  	open_json_array(PRINT_JSON,
>  			is_json_context() ?  "flags" : "");
> @@ -116,6 +116,9 @@ static void fdb_print_flags(FILE *fp, unsigned int
flags)
>  	if (flags & NTF_STICKY)
>  		print_string(PRINT_ANY, NULL, "%s ", "sticky");
>  
> +	if (ext_flags & NTF_EXT_LOCKED)
> +		print_string(PRINT_ANY, NULL, "%s ", "locked");
> +
>  	close_json_array(PRINT_JSON, NULL);
>  }
This is a separate change. Make one patch for the MAB option and another
for the new "locked" FDB flag.
>  
> @@ -144,6 +147,7 @@ int print_fdb(struct nlmsghdr *n, void *arg)
>  	struct ndmsg *r = NLMSG_DATA(n);
>  	int len = n->nlmsg_len;
>  	struct rtattr *tb[NDA_MAX+1];
> +	__u32 ext_flags = 0;
>  	__u16 vid = 0;
>  
>  	if (n->nlmsg_type != RTM_NEWNEIGH && n->nlmsg_type !=
RTM_DELNEIGH) {
> @@ -170,6 +174,9 @@ int print_fdb(struct nlmsghdr *n, void *arg)
>  	parse_rtattr(tb, NDA_MAX, NDA_RTA(r),
>  		     n->nlmsg_len - NLMSG_LENGTH(sizeof(*r)));
>  
> +	if (tb[NDA_FLAGS_EXT])
> +		ext_flags = rta_getattr_u32(tb[NDA_FLAGS_EXT]);
> +
>  	if (tb[NDA_VLAN])
>  		vid = rta_getattr_u16(tb[NDA_VLAN]);
>  
> @@ -266,7 +273,7 @@ int print_fdb(struct nlmsghdr *n, void *arg)
>  	if (show_stats && tb[NDA_CACHEINFO])
>  		fdb_print_stats(fp, RTA_DATA(tb[NDA_CACHEINFO]));
>  
> -	fdb_print_flags(fp, r->ndm_flags);
> +	fdb_print_flags(fp, r->ndm_flags, ext_flags);
>  
>  
>  	if (tb[NDA_MASTER])
> @@ -414,6 +421,7 @@ static int fdb_modify(int cmd, int flags, int argc,
char **argv)
>  	char *endptr;
>  	short vid = -1;
>  	__u32 nhid = 0;
> +	__u32 ext_flags = 0;
>  
>  	while (argc > 0) {
>  		if (strcmp(*argv, "dev") == 0) {
> @@ -527,6 +535,11 @@ static int fdb_modify(int cmd, int flags, int argc,
char **argv)
>  	if (dst_ok)
>  		addattr_l(&req.n, sizeof(req), NDA_DST, &dst.data, dst.bytelen);
>  
> +	if (ext_flags &&
> +	    addattr_l(&req.n, sizeof(req), NDA_FLAGS_EXT, &ext_flags,
> +		      sizeof(ext_flags)) < 0)
> +		return -1;
> +
I believe this belongs with the "blackhole" patch.
>  	if (vid >= 0)
>  		addattr16(&req.n, sizeof(req), NDA_VLAN, vid);
>  	if (nhid > 0)
> diff --git a/bridge/link.c b/bridge/link.c
> index 3810fa04..dd69d7c3 100644
> --- a/bridge/link.c
> +++ b/bridge/link.c
> @@ -181,9 +181,14 @@ static void print_protinfo(FILE *fp, struct rtattr
*attr)
>  		if (prtb[IFLA_BRPORT_ISOLATED])
>  			print_on_off(PRINT_ANY, "isolated", "isolated %s ",
>  				     rta_getattr_u8(prtb[IFLA_BRPORT_ISOLATED]));
> -		if (prtb[IFLA_BRPORT_LOCKED])
> -			print_on_off(PRINT_ANY, "locked", "locked %s ",
> -				     rta_getattr_u8(prtb[IFLA_BRPORT_LOCKED]));
> +		if (prtb[IFLA_BRPORT_LOCKED]) {
> +			if (prtb[IFLA_BRPORT_MAB] &&
rta_getattr_u8(prtb[IFLA_BRPORT_MAB]))
> +				print_on_off(PRINT_ANY, "locked mab", "locked mab %s
",
> +					     rta_getattr_u8(prtb[IFLA_BRPORT_LOCKED]));
> +			else
> +				print_on_off(PRINT_ANY, "locked", "locked %s ",
> +					     rta_getattr_u8(prtb[IFLA_BRPORT_LOCKED]));
> +		}
These a separate flags and need to be dumped independently. The fact
that MAB can only be enabled when the port is locked is enforced by the
kernel.
>  	} else
>  		print_stp_state(rta_getattr_u8(attr));
>  }
> @@ -281,6 +286,7 @@ static void usage(void)
>  		"                               [ vlan_tunnel {on | off} ]\n"
>  		"                               [ isolated {on | off} ]\n"
>  		"                               [ locked {on | off} ]\n"
> +		"                               [ mab {on | off} ]\n"
>  		"                               [ hwmode {vepa | veb} ]\n"
>  		"                               [ backup_port DEVICE ] [
nobackup_port ]\n"
>  		"                               [ self ] [ master ]\n"
> @@ -312,6 +318,7 @@ static int brlink_modify(int argc, char **argv)
>  	__s8 bcast_flood = -1;
>  	__s8 mcast_to_unicast = -1;
>  	__s8 locked = -1;
> +	__s8 macauth = -1;
>  	__s8 isolated = -1;
>  	__s8 hairpin = -1;
>  	__s8 bpdu_guard = -1;
> @@ -437,6 +444,11 @@ static int brlink_modify(int argc, char **argv)
>  			locked = parse_on_off("locked", *argv, &ret);
>  			if (ret)
>  				return ret;
> +		} else if (strcmp(*argv, "mab") == 0) {
> +			NEXT_ARG();
> +			macauth = parse_on_off("mab", *argv, &ret);
> +			if (ret)
> +				return ret;
>  		} else if (strcmp(*argv, "backup_port") == 0) {
>  			NEXT_ARG();
>  			backup_port_idx = ll_name_to_index(*argv);
> @@ -520,6 +532,9 @@ static int brlink_modify(int argc, char **argv)
>  	if (locked >= 0)
>  		addattr8(&req.n, sizeof(req), IFLA_BRPORT_LOCKED, locked);
>  
> +	if (macauth >= 0)
> +		addattr8(&req.n, sizeof(req), IFLA_BRPORT_MAB, macauth);
> +
>  	if (backup_port_idx != -1)
>  		addattr32(&req.n, sizeof(req), IFLA_BRPORT_BACKUP_PORT,
>  			  backup_port_idx);
> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index 7494cffb..58a002de 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
> @@ -559,6 +559,7 @@ 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 a998bf76..4dda051b 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/ip/iplink_bridge_slave.c b/ip/iplink_bridge_slave.c
> index 98d17213..0c0894eb 100644
> --- a/ip/iplink_bridge_slave.c
> +++ b/ip/iplink_bridge_slave.c
> @@ -44,6 +44,7 @@ static void print_explain(FILE *f)
>  		"			[ vlan_tunnel {on | off} ]\n"
>  		"			[ isolated {on | off} ]\n"
>  		"			[ locked {on | off} ]\n"
> +		"                       [ mab {on | off} ]\n"
>  		"			[ backup_port DEVICE ] [ nobackup_port ]\n"
>  	);
>  }
> @@ -284,9 +285,14 @@ static void bridge_slave_print_opt(struct link_util
*lu, FILE *f,
>  		print_on_off(PRINT_ANY, "isolated", "isolated %s ",
>  			     rta_getattr_u8(tb[IFLA_BRPORT_ISOLATED]));
>  
> -	if (tb[IFLA_BRPORT_LOCKED])
> -		print_on_off(PRINT_ANY, "locked", "locked %s ",
> -			     rta_getattr_u8(tb[IFLA_BRPORT_LOCKED]));
> +	if (tb[IFLA_BRPORT_LOCKED]) {
> +		if (tb[IFLA_BRPORT_MAB] && rta_getattr_u8(tb[IFLA_BRPORT_MAB]))
> +			print_on_off(PRINT_ANY, "locked mab", "locked mab %s
",
> +				     rta_getattr_u8(tb[IFLA_BRPORT_LOCKED]));
> +		else
> +			print_on_off(PRINT_ANY, "locked", "locked %s ",
> +				     rta_getattr_u8(tb[IFLA_BRPORT_LOCKED]));
> +	}
Same comment as before.
>  
>  	if (tb[IFLA_BRPORT_BACKUP_PORT]) {
>  		int backup_p = rta_getattr_u32(tb[IFLA_BRPORT_BACKUP_PORT]);
> @@ -411,6 +417,10 @@ static int bridge_slave_parse_opt(struct link_util
*lu, int argc, char **argv,
>  			NEXT_ARG();
>  			bridge_slave_parse_on_off("locked", *argv, n,
>  						  IFLA_BRPORT_LOCKED);
> +		} else if (matches(*argv, "mab") == 0) {
> +			NEXT_ARG();
> +			bridge_slave_parse_on_off("mab", *argv, n,
> +						  IFLA_BRPORT_MAB);
>  		} else if (matches(*argv, "backup_port") == 0) {
>  			int ifindex;
>  
> diff --git a/man/man8/bridge.8 b/man/man8/bridge.8
> index d4df772e..40250477 100644
> --- a/man/man8/bridge.8
> +++ b/man/man8/bridge.8
> @@ -54,6 +54,7 @@ bridge \- show / manipulate bridge addresses and devices
>  .BR vlan_tunnel " { " on " | " off " } ] [ "
>  .BR isolated " { " on " | " off " } ] [ "
>  .BR locked " { " on " | " off " } ] [ "
> +.BR mab " { " on " | " off " } ] [ "
>  .B backup_port
>  .IR  DEVICE " ] ["
>  .BR nobackup_port " ] [ "
> @@ -580,6 +581,15 @@ The common use is that hosts are allowed access
through authentication
>  with the IEEE 802.1X protocol or based on whitelists or like setups.
>  By default this flag is off.
>  
> +.TP
> +.RB "mab on " or " mab off "
> +Enables or disables the MAB/MacAuth feature. This feature can only be
> +activated on a port that is in locked mode, and when enabled it extends
the
s/activated/enabled/
> +locked port feature so that MAC address can get access through a locked
s/MAC address/a host/ ?
> +port based on acceptlists, thus it is a much simpler procedure for a
> +device to become authorized than f.ex. the 802.1X protocol, and is used
> +for devices that are not capable of password or crypto based authorization
> +methods.
This is a high level description of the option, but it is missing the
part that ties it to the "locked" FDB entries.

Speaking of which, the "locked" flag needs to be described in
man/man8/bridge.8 (in a different patch)
>  
>  .TP
>  .BI backup_port " DEVICE"
> diff --git a/man/man8/ip-link.8.in b/man/man8/ip-link.8.in
> index fc9d62fc..187ca7ca 100644
> --- a/man/man8/ip-link.8.in
> +++ b/man/man8/ip-link.8.in
> @@ -2454,6 +2454,9 @@ the following additional arguments are supported:
>  .BR isolated " { " on " | " off " }"
>  ] [
>  .BR locked " { " on " | " off " }"
> +] [
> +.BR mab " { " on " | " off " }"
> +] [
>  .BR backup_port " DEVICE"
>  ] [
>  .BR nobackup_port " ]"
> @@ -2560,6 +2563,11 @@ default this flag is off.
>  behind the port cannot communicate through the port unless a FDB entry
>  representing the host is in the FDB. By default this flag is off.
>  
> +.BR mab " { " on " | " off " }"
> +- enables or disables the MAB/MacAuth feature on a locked port. It is
> +thus possible for a device to gain authorization on a locked port based
> +on acceptlists.
Why not just copy-paste the previous description?
> +
>  .BI backup_port " DEVICE"
>  - if the port loses carrier all traffic will be redirected to the
>  configured backup port
> -- 
> 2.34.1
>