On Fri, 2014-02-07 at 09:31 -0700, Stephen Hemminger wrote:

On Fri,  7 Feb 2014 16:48:19 +0900
Toshiaki Makita [off-list ref] wrote:

quoted

Since commit bc9a25d21ef8 ("bridge: Add vlan support for local fdb entries"),
br_fdb_changeaddr() has inserted a new local fdb entry only if it can
find old one. But if we have two ports where they have the same address
or user has deleted a local entry, there will be no entry for one of the
ports.

Example of problematic case:
  ip link set eth0 address aa:bb:cc:dd:ee:ff
  ip link set eth1 address aa:bb:cc:dd:ee:ff
  brctl addif br0 eth0
  brctl addif br0 eth1 # eth1 will not have a local entry due to dup.

I think the second addif should fail, it doesn't seem valid to have
two interfaces on same bridge with same address. Most hardware switches
would disable the port in that case.

Thank you for your comment, but I don't think so for several reasons.

- From other network elements on the same network, bridge ports don't
appear to have a mac address, but the bridge appears to have several mac
addresses that can reach to the bridge. The duplicated address is simply
seen as one of those addresses. I don't think it is a problem.

- This operation (add a port that has duplicated address) has allowed
for several years, and it is obviously intended, as commented in
fdb_insert().

417                 /* it is okay to have multiple ports with same
418                  * address, just use the first one.
419                  */

- Hardware switches usually have one mac address per one switch. Their
ports don't have mac addresses. It is not reasonable to compare hardware
switches.

Thanks,
Toshiaki Makita