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Message-ID: <529CBE61.8030402@redhat.com>
Date: Mon, 02 Dec 2013 12:07:45 -0500
From: Vlad Yasevich <vyasevic@...hat.com>
To: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>,
"David S . Miller" <davem@...emloft.net>,
Stephen Hemminger <stephen@...workplumber.org>,
netdev@...r.kernel.org
Subject: Re: [PATCH net 4/7] bridge: Fix the way checking if a local fdb entry
can be deleted
On 12/02/2013 01:40 AM, Toshiaki Makita wrote:
> We should take into account the followings when deleting a local fdb entry.
>
> - nbp_vlan_find() can be used only when vid != 0 to check if an entry is
> deletable, because a fdb entry with vid 0 can exist at any time but
> nbp_vlan_find() always return false with vid 0.
>
> Example of problematic case:
> ip link set eth0 address 12:34:56:78:90:ab
> ip link set eth1 address 12:34:56:78:90:ab
> brctl addif br0 eth0
> brctl addif br0 eth1
> ip link set eth0 address aa:bb:cc:dd:ee:ff
> Then, the fdb entry 12:34:56:78:90:ab will be deleted even though the
> bridge port eth1 still has that address.
>
> - The port to which the bridge device is attached might needs a local entry
> if its mac address is set manually.
>
> Example of problematic case:
> ip link set eth0 address 12:34:56:78:90:ab
> brctl addif br0 eth0
> ip link set br0 address 12:34:56:78:90:ab
> ip link set eth0 address aa:bb:cc:dd:ee:ff
> Then, the fdb still must have the entry 12:34:56:78:90:ab, but it will be
> deleted.
>
> We can use br->dev->addr_assign_type to check if the address is manually
> set or not, but I propose another approach.
>
> Since we delete and insert local entries whenever changing mac address
> of the bridge device, we can change dst of the entry to NULL regardless of
> addr_assign_type when deleting an entry associated with a certain port,
> and if it is found to be unnecessary later, then delete it.
> That is, if changing mac address of a port, the entry might be changed
> to its dst being NULL first, but is eventually deleted when recalculating
> and changing bridge id.
>
> This approach is useful when we want to share the code with deleting
> vlan in which the bridge device might want such an entry regardless of
> addr_assign_type, and makes things easy because we don't have to consider
> if mac address of the bridge device will be changed or not at
> fdb_delete_local().
This is a nifty approach, but it does have one side-effect that I am not
sure is correct. In the case where bridge mac address is not manually
set, a fdb entry for the removed address survives past the
synchronize_net() call. This would result in a behavioral change where
packets that always used to flood, would now sometimes be delivered
only to the bridge.
-vlad
>
> Signed-off-by: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
> ---
> net/bridge/br_fdb.c | 9 ++++++++-
> net/bridge/br_private.h | 6 ++++++
> net/bridge/br_vlan.c | 19 +++++++++++++++++++
> 3 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
> index d29e184..2c79b1b 100644
> --- a/net/bridge/br_fdb.c
> +++ b/net/bridge/br_fdb.c
> @@ -108,12 +108,19 @@ static void fdb_delete_local(struct net_bridge *br,
> /* Maybe another port has same hw addr? */
> list_for_each_entry(op, &br->port_list, list) {
> if (op != p && ether_addr_equal(op->dev->dev_addr, addr) &&
> - nbp_vlan_find(op, vid)) {
> + (!vid || nbp_vlan_find(op, vid))) {
> f->dst = op;
> return;
> }
> }
>
> + /* Maybe bridge device has same hw addr? */
> + if (p && ether_addr_equal(br->dev->dev_addr, addr) &&
> + (!vid || br_vlan_find(br, vid))) {
> + f->dst = NULL;
> + return;
> + }
> +
> fdb_delete(br, f);
> }
>
> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
> index 0902658..673ef9d 100644
> --- a/net/bridge/br_private.h
> +++ b/net/bridge/br_private.h
> @@ -584,6 +584,7 @@ struct sk_buff *br_handle_vlan(struct net_bridge *br,
> int br_vlan_add(struct net_bridge *br, u16 vid, u16 flags);
> int br_vlan_delete(struct net_bridge *br, u16 vid);
> void br_vlan_flush(struct net_bridge *br);
> +bool br_vlan_find(struct net_bridge *br, u16 vid);
> int br_vlan_filter_toggle(struct net_bridge *br, unsigned long val);
> int nbp_vlan_add(struct net_bridge_port *port, u16 vid, u16 flags);
> int nbp_vlan_delete(struct net_bridge_port *port, u16 vid);
> @@ -665,6 +666,11 @@ static inline void br_vlan_flush(struct net_bridge *br)
> {
> }
>
> +static inline bool br_vlan_find(struct net_bridge *br, u16 vid)
> +{
> + return false;
> +}
> +
> static inline int nbp_vlan_add(struct net_bridge_port *port, u16 vid, u16 flags)
> {
> return -EOPNOTSUPP;
> diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
> index af5ebd1..f87ab88f 100644
> --- a/net/bridge/br_vlan.c
> +++ b/net/bridge/br_vlan.c
> @@ -316,6 +316,25 @@ void br_vlan_flush(struct net_bridge *br)
> __vlan_flush(pv);
> }
>
> +bool br_vlan_find(struct net_bridge *br, u16 vid)
> +{
> + struct net_port_vlans *pv;
> + bool found = false;
> +
> + rcu_read_lock();
> + pv = rcu_dereference(br->vlan_info);
> +
> + if (!pv)
> + goto out;
> +
> + if (test_bit(vid, pv->vlan_bitmap))
> + found = true;
> +
> +out:
> + rcu_read_unlock();
> + return found;
> +}
> +
> int br_vlan_filter_toggle(struct net_bridge *br, unsigned long val)
> {
> if (!rtnl_trylock())
>
--
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