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Miller" , Eric Dumazet , Jakub Kicinski , Nikolay Aleksandrov , Simon Horman , Cosmin Ratiu , linux-kernel@vger.kernel.org, Liang Li Subject: Re: [PATCH net] bonding: use permanent address for MAC swapping if device address is same Message-ID: References: <20250319080947.2001-1-liuhangbin@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Apr 03, 2025 at 04:02:33PM +0200, Paolo Abeni wrote: > On 3/19/25 9:09 AM, Hangbin Liu wrote: > > Similar with a951bc1e6ba5 ("bonding: correct the MAC address for "follow" > > fail_over_mac policy"). The fail_over_mac follow mode requires the formerly > > active slave to swap MAC addresses with the newly active slave during > > failover. However, the slave's MAC address can be same under certain > > conditions: > > > > 1) ip link set eth0 master bond0 > > bond0 adopts eth0's MAC address (MAC0). > > > > 1) ip link set eth1 master bond0 > > eth1 is added as a backup with its own MAC (MAC1). > > > > 3) ip link set eth0 nomaster > > eth0 is released and restores its MAC (MAC0). > > eth1 becomes the active slave, and bond0 assigns MAC0 to eth1. > > It was not immediately clear to me that the mac-dance in the code below > happens only at failover time. > > I second Jakub's doubt, I think it would be better to change eth0 mac > address here (possibly to permanent eth1 mac, to preserve some consistency?) I have talked about one of the duplicate mac issue with Jay before [1]. We decided to print a warning for that. I will discuss with Jay for this one in one new patch thread. [1] https://lore.kernel.org/netdev/Z49yXz1dx2ZzqhC1@fedora Thanks Hangbin > > Doing that in ndo_del_slave() should allow bonding to change the mac > while still owning the old slave and avoid races with user-space. > > WDYT? > > Thanks, > > Paolo >