Re: [Bridge] [PATCH net-next 2/6] net: bridge: fdb: add support for fine-grained flushing

[Ido Schimmel <idosch@idosch.org>]

On Sat, Apr 09, 2022 at 01:58:53PM +0300, Nikolay Aleksandrov wrote:
> Add the ability to specify exactly which fdbs to be flushed. They are
> described by a new structure - net_bridge_fdb_flush_desc. Currently it
> can match on port/bridge ifindex, vlan id and fdb flags. It is used to
> describe the existing dynamic fdb flush operation.
> 
> Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>
> ---
>  net/bridge/br_fdb.c      | 36 +++++++++++++++++++++++++++++-------
>  net/bridge/br_netlink.c  |  9 +++++++--
>  net/bridge/br_private.h  | 10 +++++++++-
>  net/bridge/br_sysfs_br.c |  6 +++++-
>  4 files changed, 50 insertions(+), 11 deletions(-)
> 
> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
> index 6ccda68bd473..4b0bf88c4121 100644
> --- a/net/bridge/br_fdb.c
> +++ b/net/bridge/br_fdb.c
> @@ -558,18 +558,40 @@ void br_fdb_cleanup(struct work_struct *work)
>  	mod_delayed_work(system_long_wq, &br->gc_work, work_delay);
>  }
>  
> -/* Completely flush all dynamic entries in forwarding database.*/
> -void br_fdb_flush(struct net_bridge *br)
> +static bool __fdb_flush_matches(const struct net_bridge *br,
> +				const struct net_bridge_fdb_entry *f,
> +				const struct net_bridge_fdb_flush_desc *desc)
> +{
> +	const struct net_bridge_port *dst = READ_ONCE(f->dst);
> +	int port_ifidx, br_ifidx = br->dev->ifindex;
> +
> +	port_ifidx = dst ? dst->dev->ifindex : 0;
> +
> +	return (!desc->vlan_id || desc->vlan_id == f->key.vlan_id) &&
> +	       (!desc->port_ifindex ||
> +		(desc->port_ifindex == port_ifidx ||
> +		 (!dst && desc->port_ifindex == br_ifidx))) &&
> +	       (!desc->flags_mask ||
> +		((f->flags & desc->flags_mask) == desc->flags));

I find this easier to read:

port_ifidx = dst ? dst->dev->ifindex : br_ifidx;

if (desc->vlan_id && desc->vlan_id != f->key.vlan_id)
	return false;
if (desc->port_ifindex && desc->port_ifindex != port_ifidx)
	return false;
if (desc->flags_mask && (f->flags & desc->flags_mask) != desc->flags)
	return false;

return true;

> +}
> +
> +/* Flush forwarding database entries matching the description */
> +void br_fdb_flush(struct net_bridge *br,
> +		  const struct net_bridge_fdb_flush_desc *desc)
>  {
>  	struct net_bridge_fdb_entry *f;
> -	struct hlist_node *tmp;
>  
> -	spin_lock_bh(&br->hash_lock);
> -	hlist_for_each_entry_safe(f, tmp, &br->fdb_list, fdb_node) {
> -		if (!test_bit(BR_FDB_STATIC, &f->flags))
> +	rcu_read_lock();
> +	hlist_for_each_entry_rcu(f, &br->fdb_list, fdb_node) {
> +		if (!__fdb_flush_matches(br, f, desc))
> +			continue;
> +
> +		spin_lock_bh(&br->hash_lock);
> +		if (!hlist_unhashed(&f->fdb_node))
>  			fdb_delete(br, f, true);
> +		spin_unlock_bh(&br->hash_lock);
>  	}
> -	spin_unlock_bh(&br->hash_lock);
> +	rcu_read_unlock();
>  }
>  
>  /* Flush all entries referring to a specific port.
> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
> index fe2211d4c0c7..6e6dce6880c9 100644
> --- a/net/bridge/br_netlink.c
> +++ b/net/bridge/br_netlink.c
> @@ -1366,8 +1366,13 @@ static int br_changelink(struct net_device *brdev, struct nlattr *tb[],
>  		br_recalculate_fwd_mask(br);
>  	}
>  
> -	if (data[IFLA_BR_FDB_FLUSH])
> -		br_fdb_flush(br);
> +	if (data[IFLA_BR_FDB_FLUSH]) {
> +		struct net_bridge_fdb_flush_desc desc = {
> +			.flags_mask = BR_FDB_STATIC
> +		};
> +
> +		br_fdb_flush(br, &desc);

I wanted to ask why you are not doing the same for IFLA_BRPORT_FLUSH,
but then I read the implementation of br_fdb_delete_by_port() and
remembered the comment in the cover letter regarding fdb_delete vs
fdb_delete_local. Probably best to note it in the commit message

> +	}
>  
>  #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
>  	if (data[IFLA_BR_MCAST_ROUTER]) {
> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
> index 6e62af2e07e9..e6930e9ee69d 100644
> --- a/net/bridge/br_private.h
> +++ b/net/bridge/br_private.h
> @@ -274,6 +274,13 @@ struct net_bridge_fdb_entry {
>  	struct rcu_head			rcu;
>  };
>  
> +struct net_bridge_fdb_flush_desc {
> +	unsigned long			flags;
> +	unsigned long			flags_mask;
> +	int				port_ifindex;
> +	u16				vlan_id;
> +};
> +
>  #define MDB_PG_FLAGS_PERMANENT	BIT(0)
>  #define MDB_PG_FLAGS_OFFLOAD	BIT(1)
>  #define MDB_PG_FLAGS_FAST_LEAVE	BIT(2)
> @@ -759,7 +766,8 @@ int br_fdb_init(void);
>  void br_fdb_fini(void);
>  int br_fdb_hash_init(struct net_bridge *br);
>  void br_fdb_hash_fini(struct net_bridge *br);
> -void br_fdb_flush(struct net_bridge *br);
> +void br_fdb_flush(struct net_bridge *br,
> +		  const struct net_bridge_fdb_flush_desc *desc);
>  void br_fdb_find_delete_local(struct net_bridge *br,
>  			      const struct net_bridge_port *p,
>  			      const unsigned char *addr, u16 vid);
> diff --git a/net/bridge/br_sysfs_br.c b/net/bridge/br_sysfs_br.c
> index 3f7ca88c2aa3..612e367fff20 100644
> --- a/net/bridge/br_sysfs_br.c
> +++ b/net/bridge/br_sysfs_br.c
> @@ -344,7 +344,11 @@ static DEVICE_ATTR_RW(group_addr);
>  static int set_flush(struct net_bridge *br, unsigned long val,
>  		     struct netlink_ext_ack *extack)
>  {
> -	br_fdb_flush(br);
> +	struct net_bridge_fdb_flush_desc desc = {
> +		.flags_mask = BR_FDB_STATIC
> +	};
> +
> +	br_fdb_flush(br, &desc);
>  	return 0;
>  }
>  
> -- 
> 2.35.1
>