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[146.241.68.231]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43ea978378esm51169005e9.1.2025.04.03.07.02.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Apr 2025 07:02:35 -0700 (PDT) Message-ID: Date: Thu, 3 Apr 2025 16:02:33 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] bonding: use permanent address for MAC swapping if device address is same To: Hangbin Liu , netdev@vger.kernel.org Cc: Jay Vosburgh , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Nikolay Aleksandrov , Simon Horman , Cosmin Ratiu , linux-kernel@vger.kernel.org, Liang Li References: <20250319080947.2001-1-liuhangbin@gmail.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20250319080947.2001-1-liuhangbin@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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?) 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