[Bridge] [PATCH v2 iproute2-next 1/4] include: uapi: MacAuth and Blackhole feature header changes

[Bridge] [PATCH v2 iproute2-next 1/4] include: uapi: MacAuth and Blackhole feature header changes

[Hans Schultz]

Signed-off-by: Hans Schultz <netdev@kapio-technology.com>
---
 include/uapi/linux/if_link.h   |  1 +
 include/uapi/linux/neighbour.h | 11 ++++++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

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..cc7d540e 100644
--- a/include/uapi/linux/neighbour.h
+++ b/include/uapi/linux/neighbour.h
@@ -52,7 +52,9 @@ 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)
+#define NTF_EXT_BLACKHOLE	(1 << 2)
 
 /*
  *	Neighbor Cache Entry States.
@@ -86,6 +88,13 @@ 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.
+ *
+ * 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 {
-- 
2.34.1

[Bridge] [PATCH v2 iproute2-next 2/4] bridge: fdb: show locked FDB entries flag in output

[Hans Schultz]

Signed-off-by: Hans Schultz <netdev@kapio-technology.com>
---
 bridge/fdb.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/bridge/fdb.c b/bridge/fdb.c
index 5f71bde0..f1f0a5bb 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])
-- 
2.34.1

Re: [Bridge] [PATCH v2 iproute2-next 2/4] bridge: fdb: show locked FDB entries flag in output

[Ido Schimmel]

On Tue, Oct 04, 2022 at 05:20:34PM +0200, Hans Schultz wrote:
> Signed-off-by: Hans Schultz <netdev@kapio-technology.com>

Don't leave the commit message empty. Explain the change and include an
example output showing the "locked" flag.

> ---
>  bridge/fdb.c | 11 +++++++++--

Still missing a description of the "locked" flag from the man page.
Something like:

"
locked - this entry was added by the kernel in response to a host trying
to communicate behind a bridge port with MAB enabled. User space can
authenticate the host by clearing the flag. The flag cannot be set by
user space.
"

>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/bridge/fdb.c b/bridge/fdb.c
> index 5f71bde0..f1f0a5bb 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)

s/__u8/__u32/

>  {
>  	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])
> -- 
> 2.34.1
> 

[Bridge] [PATCH v2 iproute2-next 3/4] bridge: link: enable MacAuth/MAB feature

[Hans Schultz]

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

Examples of output when the feature is enabled:

$ bridge -d link show dev eth1
1: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master testbr state forwarding priority 32 cost 2
    hairpin off guard off root_block off fastleave off learning on flood on mcast_flood on bcast_flood on mcast_router 1 mcast_to_unicast off neigh_suppress off vlan_tunnel off isolated off locked on mab on
$ bridge -d -j -p link show dev eth1
[ {
        "ifindex": 1,
        "ifname": "eth1",
        "flags": [ "BROADCAST","MULTICAST","UP","LOWER_UP" ],
        "mtu": 1500,
        "master": "br0",
        "state": "forwarding",
        "priority": 32,
        "cost": 2,
        "hairpin": false,
        "guard": false,
        "root_block": false,
        "fastleave": false,
        "learning": true,
        "flood": true,
        "mcast_flood": true,
        "bcast_flood": true,
        "mcast_router": 1,
        "mcast_to_unicast": false,
        "neigh_suppress": false,
        "vlan_tunnel": false,
        "isolated": false,
        "locked": true,
        "mab": true
    } ]

Signed-off-by: Hans Schultz <netdev@kapio-technology.com>
---
 bridge/link.c            | 13 +++++++++++++
 ip/iplink_bridge_slave.c |  9 +++++++++
 man/man8/bridge.8        | 12 ++++++++++++
 man/man8/ip-link.8.in    | 14 ++++++++++++++
 4 files changed, 48 insertions(+)

diff --git a/bridge/link.c b/bridge/link.c
index 3810fa04..25a45860 100644
--- a/bridge/link.c
+++ b/bridge/link.c
@@ -184,6 +184,9 @@ static void print_protinfo(FILE *fp, struct rtattr *attr)
 		if (prtb[IFLA_BRPORT_LOCKED])
 			print_on_off(PRINT_ANY, "locked", "locked %s ",
 				     rta_getattr_u8(prtb[IFLA_BRPORT_LOCKED]));
+		if (prtb[IFLA_BRPORT_MAB])
+			print_on_off(PRINT_ANY, "mab", "mab %s ",
+				     rta_getattr_u8(prtb[IFLA_BRPORT_MAB]));
 	} else
 		print_stp_state(rta_getattr_u8(attr));
 }
@@ -281,6 +284,7 @@ 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 +316,7 @@ 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 +442,11 @@ 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 +530,9 @@ 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/ip/iplink_bridge_slave.c b/ip/iplink_bridge_slave.c
index 98d17213..e5262bdb 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"
 	);
 }
@@ -288,6 +289,10 @@ static void bridge_slave_print_opt(struct link_util *lu, FILE *f,
 		print_on_off(PRINT_ANY, "locked", "locked %s ",
 			     rta_getattr_u8(tb[IFLA_BRPORT_LOCKED]));
 
+	if (tb[IFLA_BRPORT_MAB])
+		print_on_off(PRINT_ANY, "mab", "mab %s ",
+			     rta_getattr_u8(tb[IFLA_BRPORT_MAB]));
+
 	if (tb[IFLA_BRPORT_BACKUP_PORT]) {
 		int backup_p = rta_getattr_u32(tb[IFLA_BRPORT_BACKUP_PORT]);
 
@@ -411,6 +416,10 @@ 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..f4f1d807 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 +581,17 @@ 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
+.BR "mab on " or " mab off "
+Enables or disables the MAB/MacAuth feature. This feature can only be
+enabled on a port that is in locked mode, and when enabled it extends the
+locked port feature so that a host 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.
+The feature triggers a 'locked' FDB entry when a host tries to communicate
+through the MAB enabled port.
 
 .TP
 .BI backup_port " DEVICE"
diff --git a/man/man8/ip-link.8.in b/man/man8/ip-link.8.in
index fc9d62fc..5f31f80a 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 +2563,17 @@ 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. This feature can only be
+enabled on a port that is in locked mode, and when enabled it extends the
+locked port feature so that a host 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.
+The feature triggers a 'locked' FDB entry when a host tries to communicate
+through the MAB enabled port.
+
 .BI backup_port " DEVICE"
 - if the port loses carrier all traffic will be redirected to the
 configured backup port
-- 
2.34.1

[Bridge] [PATCH v2 iproute2-next 4/4] bridge: fdb: enable FDB blackhole feature

[Hans Schultz]

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

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

Example with output:

$ bridge fdb add 10:10:10:10:10:10 dev br0 blackhole
$ bridge -d fdb show dev br0
10:10:10:10:10:10 vlan 1 blackhole master br0 permanent
10:10:10:10:10:10 blackhole master br0 permanent
$ bridge -d -j -p fdb show dev br0
[ {
        "mac": "10:10:10:10:10:10",
        "vlan": 1,
        "flags": [ "blackhole" ],
        "master": "br0",
        "state": "permanent"
    },{
        "mac": "10:10:10:10:10:10",
        "flags": [ "blackhole" ],
        "master": "br0",
        "state": "permanent"
    } ]

Signed-off-by: Hans Schultz <netdev@kapio-technology.com>
---
 bridge/fdb.c      | 13 ++++++++++++-
 man/man8/bridge.8 | 12 ++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/bridge/fdb.c b/bridge/fdb.c
index f1f0a5bb..1c8c50a8 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");
 
@@ -421,6 +424,7 @@ 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) {
@@ -492,6 +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();
@@ -534,6 +540,11 @@ 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/man/man8/bridge.8 b/man/man8/bridge.8
index f4f1d807..0119a2a9 100644
--- a/man/man8/bridge.8
+++ b/man/man8/bridge.8
@@ -85,6 +85,13 @@ bridge \- show / manipulate bridge addresses and devices
 .B nhid
 .IR NHID " } "
 
+.ti -8
+.BR "bridge fdb" " { " add " | " del " } "
+.I LLADR
+.B dev
+.IR BRDEV " [ "
+.BR self " ] [ " local " ] [ " blackhole " ] "
+
 .ti -8
 .BR "bridge fdb" " [ [ " show " ] [ "
 .B br
@@ -701,6 +708,11 @@ 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 entry will silently discard all matching packets. The entry must
+be added as a local permanent entry.
+.sp
+
 .in -8
 The next command line parameters apply only
 when the specified device
-- 
2.34.1

Re: [Bridge] [PATCH v2 iproute2-next 4/4] bridge: fdb: enable FDB blackhole feature

[Ido Schimmel]

On Tue, Oct 04, 2022 at 05:20:36PM +0200, Hans Schultz wrote:
> Block traffic to a specific host with the command:
> bridge fdb add <MAC> vlan <vid> dev br0 blackhole
> 
> Blackhole FDB entries can be added, deleted and replaced with
> ordinary FDB entries.
> 
> Example with output:
> 
> $ bridge fdb add 10:10:10:10:10:10 dev br0 blackhole
> $ bridge -d fdb show dev br0
> 10:10:10:10:10:10 vlan 1 blackhole master br0 permanent
> 10:10:10:10:10:10 blackhole master br0 permanent
> $ bridge -d -j -p fdb show dev br0
> [ {
>         "mac": "10:10:10:10:10:10",
>         "vlan": 1,
>         "flags": [ "blackhole" ],
>         "master": "br0",
>         "state": "permanent"
>     },{
>         "mac": "10:10:10:10:10:10",
>         "flags": [ "blackhole" ],
>         "master": "br0",
>         "state": "permanent"
>     } ]
> 
> Signed-off-by: Hans Schultz <netdev@kapio-technology.com>
> ---
>  bridge/fdb.c      | 13 ++++++++++++-
>  man/man8/bridge.8 | 12 ++++++++++++
>  2 files changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/bridge/fdb.c b/bridge/fdb.c
> index f1f0a5bb..1c8c50a8 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");
>  
> @@ -421,6 +424,7 @@ 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) {
> @@ -492,6 +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;

The policy seems to be to use strcmp() instead of matches() in new code:

https://lore.kernel.org/netdev/f7251b13-dbf2-f86c-6c2a-2c037b208017@gmail.com/

>  		} else {
>  			if (strcmp(*argv, "to") == 0)
>  				NEXT_ARG();
> @@ -534,6 +540,11 @@ 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)

addattr32() ?

I will check the kernel patches now. I wouldn't submit a new version to
iproute2-next until the kernel patches are accepted.

> +		return -1;
> +
>  	if (vid >= 0)
>  		addattr16(&req.n, sizeof(req), NDA_VLAN, vid);
>  	if (nhid > 0)
> diff --git a/man/man8/bridge.8 b/man/man8/bridge.8
> index f4f1d807..0119a2a9 100644
> --- a/man/man8/bridge.8
> +++ b/man/man8/bridge.8
> @@ -85,6 +85,13 @@ bridge \- show / manipulate bridge addresses and devices
>  .B nhid
>  .IR NHID " } "
>  
> +.ti -8
> +.BR "bridge fdb" " { " add " | " del " } "
> +.I LLADR
> +.B dev
> +.IR BRDEV " [ "
> +.BR self " ] [ " local " ] [ " blackhole " ] "
> +
>  .ti -8
>  .BR "bridge fdb" " [ [ " show " ] [ "
>  .B br
> @@ -701,6 +708,11 @@ 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 entry will silently discard all matching packets. The entry must
> +be added as a local permanent entry.
> +.sp
> +
>  .in -8
>  The next command line parameters apply only
>  when the specified device
> -- 
> 2.34.1
>