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Message-ID: <e3f57a64-4823-7cf3-0345-3777c44c2fe4@blackwall.org>
Date:   Thu, 10 Mar 2022 17:57:22 +0200
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Subject: Re: [PATCH net-next 1/3] net: bridge: add fdb flag to extent locked
 port feature
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To:     Hans Schultz <schultz.hans@gmail.com>, davem@davemloft.net,
        kuba@kernel.org
Cc:     netdev@vger.kernel.org, Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Vladimir Oltean <olteanv@gmail.com>,
        Jiri Pirko <jiri@resnulli.us>,
        Ivan Vecera <ivecera@redhat.com>,
        Roopa Prabhu <roopa@nvidia.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Ido Schimmel <idosch@nvidia.com>, linux-kernel@vger.kernel.org,
        bridge@lists.linux-foundation.org
References: <20220310142320.611738-1-schultz.hans+netdev@gmail.com>
 <20220310142320.611738-2-schultz.hans+netdev@gmail.com>
 <0eeaf59f-e7eb-7439-3c0a-17e7ac6741f0@blackwall.org>
 <86v8wles1g.fsf@gmail.com>
From:   Nikolay Aleksandrov <razor@blackwall.org>
In-Reply-To: <86v8wles1g.fsf@gmail.com>
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Precedence: bulk

On 10/03/2022 17:38, Hans Schultz wrote:
> On tor, mar 10, 2022 at 16:42, Nikolay Aleksandrov <razor@blackwall.org> 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 <schultz.hans+netdev@gmail.com>
>>> ---
>>>    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.

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 {