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[204.195.22.127]) by smtp.gmail.com with ESMTPSA id 17sm29050703pgz.52.2019.03.26.19.13.52 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 26 Mar 2019 19:13:52 -0700 (PDT) Date: Tue, 26 Mar 2019 19:13:42 -0700 From: Stephen Hemminger To: Si-Wei Liu Cc: mst@redhat.com, sridhar.samudrala@intel.com, davem@davemloft.net, kubakici@wp.pl, alexander.duyck@gmail.com, jiri@resnulli.us, netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, liran.alon@oracle.com, boris.ostrovsky@oracle.com, vijay.balakrishna@oracle.com Subject: Re: [PATCH net v3] failover: allow name change on IFF_UP slave interfaces Message-ID: <20190326191342.11f0cb55@shemminger-XPS-13-9360> In-Reply-To: <1553644093-10917-1-git-send-email-si-wei.liu@oracle.com> References: <1553644093-10917-1-git-send-email-si-wei.liu@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, 26 Mar 2019 19:48:13 -0400 Si-Wei Liu wrote: > When a netdev appears through hot plug then gets enslaved by a failover > master that is already up and running, the slave will be opened > right away after getting enslaved. Today there's a race that userspace > (udev) may fail to rename the slave if the kernel (net_failover) > opens the slave earlier than when the userspace rename happens. > Unlike bond or team, the primary slave of failover can't be renamed by > userspace ahead of time, since the kernel initiated auto-enslavement is > unable to, or rather, is never meant to be synchronized with the rename > request from userspace. > > As the failover slave interfaces are not designed to be operated > directly by userspace apps: IP configuration, filter rules with > regard to network traffic passing and etc., should all be done on master > interface. In general, userspace apps only care about the > name of master interface, while slave names are less important as long > as admin users can see reliable names that may carry > other information describing the netdev. For e.g., they can infer that > "ens3nsby" is a standby slave of "ens3", while for a > name like "eth0" they can't tell which master it belongs to. > > Historically the name of IFF_UP interface can't be changed because > there might be admin script or management software that is already > relying on such behavior and assumes that the slave name can't be > changed once UP. But failover is special: with the in-kernel > auto-enslavement mechanism, the userspace expectation for device > enumeration and bring-up order is already broken. Previously initramfs > and various userspace config tools were modified to bypass failover > slaves because of auto-enslavement and duplicate MAC address. Similarly, > in case that users care about seeing reliable slave name, the new type > of failover slaves needs to be taken care of specifically in userspace > anyway. > > It's less risky to lift up the rename restriction on failover slave > which is already UP. Although it's possible this change may potentially > break userspace component (most likely configuration scripts or > management software) that assumes slave name can't be changed while > UP, it's relatively a limited and controllable set among all userspace > components, which can be fixed specifically to listen for the rename > and/or link down/up events on failover slaves. Userspace component > interacting with slaves is expected to be changed to operate on failover > master interface instead, as the failover slave is dynamic in nature > which may come and go at any point. The goal is to make the role of > failover slaves less relevant, and userspace components should only > deal with failover master in the long run. > > Fixes: 30c8bd5aa8b2 ("net: Introduce generic failover module") > Signed-off-by: Si-Wei Liu > Reviewed-by: Liran Alon Why do you need to do dev_close/dev_open which will bounce the link?