Re: [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@xxxxxxxxxxxxxxxxxxxx>
> ---
>  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@xxxxxxxxx/

>  		} 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
>