Subject: Re: [PATCH net-next 1/3] net: bridge: add fdb flag to extent locked port feature

From: Hans Schultz <[email-masked]>
Date: Thu, 10 Mar 2022 17:11:32 +0100

On tor, mar 10, 2022 at 17:57, Nikolay Aleksandrov <[email-masked]> wrote:
> On 10/03/2022 17:38, Hans Schultz wrote:
>> On tor, mar 10, 2022 at 16:42, Nikolay Aleksandrov <[email-masked]> wrote:
>>> On 10/03/2022 16:23, Hans Schultz wrote:
>>>> 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.
>>>>
>>>> Signed-off-by: Hans Schultz <[email-masked]>
>>>> ---
>>>>    include/uapi/linux/neighbour.h |  1 +
>>>>    net/bridge/br_fdb.c            |  6 ++++++
>>>>    net/bridge/br_input.c          | 11 ++++++++++-
>>>>    net/bridge/br_private.h        |  3 ++-
>>>>    4 files changed, 19 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/include/uapi/linux/neighbour.h b/include/uapi/linux/neighbour.h
>>>> index db05fb55055e..83115a592d58 100644
>>>> --- a/include/uapi/linux/neighbour.h
>>>> +++ b/include/uapi/linux/neighbour.h
>>>> @@ -208,6 +208,7 @@ enum {
>>>>    	NFEA_UNSPEC,
>>>>    	NFEA_ACTIVITY_NOTIFY,
>>>>    	NFEA_DONT_REFRESH,
>>>> +	NFEA_LOCKED,
>>>>    	__NFEA_MAX
>>>>    };
>>>
>>> Hmm, can you use NDA_FLAGS_EXT instead ?
>>> That should simplify things and reduce the nl size.
>>>
>> 
>> I am using NDA_FDB_EXT_ATTRS. NFEA_LOCKED is just the
>> flag as the other flags section is full wrt the normal flags, but maybe it
>> doesn't fit in that section?
>> 
>
> Actually wait a second, this is completely wrong use of NDA_FDB_EXT_ATTRS.
> That is a nested attribute, so the code below is wrong. More below..
>
>> I will just note that iproute2 support for parsing nested attributes
>> does not work, thus the BR_FDB_NOTIFY section (lines 150-165) are
>> obsolete with respect to iproute2 as it is now. I cannot rule out that
>> someone has some other tool that can handle this BR_FDB_NOTIFY, but I
>> could not make iproute2 as it stands handle nested attributes. And of
>> course there is no handling of NDA_FDB_EXT_ATTRS in iproute2 now.
>> >>>    #define NFEA_MAX (__NFEA_MAX - 1)
>>>> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
>>>> index 6ccda68bd473..396dcf3084cf 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 |= 1 << NFEA_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_FDB_EXT_ATTRS, ext_flags))
>>>> +		goto nla_put_failure;
>>>> +
>
> This is wrong. NDA_FDB_EXT_ATTRS is a nested attribute, you can't use it as a u8.
> You need to have this structure:
>   [ NDA_FDB_EXT_ATTRS ]
>    ` [ NFEA_LOCKED ]
>
> But that's why I asked if you could use the NDA_FLAGS_EXT attribute. You can see
> the logic from the neigh code.

Ahh yes, NDA_FLAGS_EXT was not there in the 5.15.x kernel I have
originally being making the patches in.

I hope that the handling of nested attributes has been fixed in
iproute2. ;-)

>
> Also note that you need to account for the new attribute's size in fdb_nlmsg_size().
>
>
>>>>    	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..897908484b18 100644
>>>> --- a/net/bridge/br_input.c
>>>> +++ b/net/bridge/br_input.c
>>>> @@ -75,6 +75,7 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
>>>>    	struct net_bridge_mcast *brmctx;
>>>>    	struct net_bridge_vlan *vlan;
>>>>    	struct net_bridge *br;
>>>> +	unsigned long flags = 0;
>>>
>>> Please move this below...
>>>
>>>>    	u16 vid = 0;
>>>>    	u8 state;
>>>>    
>>>> @@ -94,8 +95,16 @@ 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)) {
>>>> +			if (!fdb_src) {
>>>
>>> ... here where it's only used.
>>>
>> 
>> Forgot that one. Shall do!
>> 
>>>> +				set_bit(BR_FDB_ENTRY_LOCKED, &flags);
>>>> +				br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, flags);
>>>> +			}
>>>>    			goto drop;
>>>> +		} else {
>>>> +			if (test_bit(BR_FDB_ENTRY_LOCKED, &fdb_src->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 {