Re: [PATCH net v4] failover: allow name change on IFF_UP slave interfaces
On Fri, Mar 29, 2019 at 12:50:25PM -0700, si-wei liu wrote:
>
>
> On 3/28/2019 10:55 PM, Samudrala, Sridhar wrote:
> >
> >
> > On 3/28/2019 4:47 PM, 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
> > >
> > > --
> > > v1 -> v2:
> > > - Drop configurable module parameter (Sridhar)
> > >
> > > v2 -> v3:
> > > - Drop additional IFF_SLAVE_RENAME_OK flag (Sridhar)
> > > - Send down and up events around rename (Michael S. Tsirkin)
> > >
> > > v3 -> v4:
> > > - Simplify notification to be sent (Stephen Hemminger)
> > > ---
> > > net/core/dev.c | 24 +++-
> > > 1 file changed, 23 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/net/core/dev.c b/net/core/dev.c
> > > index 722d50d..6ae5874 100644
> > > --- a/net/core/dev.c
> > > +++ b/net/core/dev.c
> > > @@ -1180,7 +1180,21 @@ int dev_change_name(struct net_device *dev,
> > > const char *newname)
> > > BUG_ON(!dev_net(dev));
> > > net = dev_net(dev);
> > > -if (dev->flags & IFF_UP)
> > > +
> > > +/* Allow failover slave to rename even when
> > > + * it is up and running.
> > > + *
> > > + * Failover slaves are special, since userspace
> > > + * might rename the slave after the interface
> > > + * has been brought up and running due to
> > > + * auto-enslavement.
> > > + *
> > > + * Failover users don't actually care about slave
> > > + * name change, as they are only expected to operate
> > > + * on master interface directly.
> > > + */
> > > +if (dev->flags & IFF_UP &&
> > > +likely(!(dev->priv_flags & IFF_FAILOVER_SLAVE)))
> > > return -EBUSY;
> > > write_seqcount_begin(&devnet_rename_seq);
> > > @@ -1227,6 +1241,14 @@ int dev_change_name(struct net_device *dev,
> > > const char *newname)
> > > hlist_add_head_rcu(&dev->name_hlist, dev_name_hash(net,
> > > dev->name));
> > > write_unlock_bh(&dev_base_lock);
> > > +if (unlikely(dev->flags & IFF_UP)) {
> > > +
Re: [PATCH net v4] failover: allow name change on IFF_UP slave interfaces
Fri, Mar 29, 2019 at 04:15:12PM CET, step...@networkplumber.org wrote:
>On Thu, 28 Mar 2019 19:47:27 -0400
>Si-Wei Liu wrote:
>
>> +if (unlikely(dev->flags & IFF_UP)) {
>> +struct netdev_notifier_change_info change_info;
>> +
>> +change_info.flags_changed = 0;
>
>Simpler to use structure initialization, which also avoid any chance
>of unititialized fields.
>
> struct netdev_notifier_change_info change_info
> = { .flags_changed = 0 };
In fact, you can do just:
struct netdev_notifier_change_info change_info = {};
to achieve the same.
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Re: [PATCH net v4] failover: allow name change on IFF_UP slave interfaces
On Thu, 28 Mar 2019 19:47:27 -0400
Si-Wei Liu wrote:
> + if (unlikely(dev->flags & IFF_UP)) {
> + struct netdev_notifier_change_info change_info;
> +
> + change_info.flags_changed = 0;
Simpler to use structure initialization, which also avoid any chance
of unititialized fields.
struct netdev_notifier_change_info change_info
= { .flags_changed = 0 };
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Re: [PATCH net v4] failover: allow name change on IFF_UP slave interfaces
Hi Si-Wei,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on net/master]
url:
https://github.com/0day-ci/linux/commits/Si-Wei-Liu/failover-allow-name-change-on-IFF_UP-slave-interfaces/20190329-195445
config: x86_64-lkp (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64
All errors (new ones prefixed by >>):
net/core/dev.c: In function 'dev_change_name':
>> net/core/dev.c:1252:48: error: passing argument 2 of
>> 'call_netdevice_notifiers_info' from incompatible pointer type
>> [-Werror=incompatible-pointer-types]
call_netdevice_notifiers_info(NETDEV_CHANGE, dev,
^~~
net/core/dev.c:164:12: note: expected 'struct netdev_notifier_info *' but
argument is of type 'struct net_device *'
static int call_netdevice_notifiers_info(unsigned long val,
^
>> net/core/dev.c:1252:3: error: too many arguments to function
>> 'call_netdevice_notifiers_info'
call_netdevice_notifiers_info(NETDEV_CHANGE, dev,
^
net/core/dev.c:164:12: note: declared here
static int call_netdevice_notifiers_info(unsigned long val,
^
cc1: some warnings being treated as errors
vim +/call_netdevice_notifiers_info +1252 net/core/dev.c
1166
1167 /**
1168 * dev_change_name - change name of a device
1169 * @dev: device
1170 * @newname: name (or format string) must be at least IFNAMSIZ
1171 *
1172 * Change name of a device, can pass format strings "eth%d".
1173 * for wildcarding.
1174 */
1175 int dev_change_name(struct net_device *dev, const char *newname)
1176 {
1177 unsigned char old_assign_type;
1178 char oldname[IFNAMSIZ];
1179 int err = 0;
1180 int ret;
1181 struct net *net;
1182
1183 ASSERT_RTNL();
1184 BUG_ON(!dev_net(dev));
1185
1186 net = dev_net(dev);
1187
1188 /* Allow failover slave to rename even when
1189 * it is up and running.
1190 *
1191 * Failover slaves are special, since userspace
1192 * might rename the slave after the interface
1193 * has been brought up and running due to
1194 * auto-enslavement.
1195 *
1196 * Failover users don't actually care about slave
1197 * name change, as they are only expected to operate
1198 * on master interface directly.
1199 */
1200 if (dev->flags & IFF_UP &&
1201 likely(!(dev->priv_flags & IFF_FAILOVER_SLAVE)))
1202 return -EBUSY;
1203
1204 write_seqcount_begin(&devnet_rename_seq);
1205
1206 if (strncmp(newname, dev->name, IFNAMSIZ) == 0) {
1207 write_seqcount_end(&devnet_rename_seq);
1208 return 0;
1209 }
1210
1211 memcpy(oldname, dev->name, IFNAMSIZ);
1212
1213 err = dev_get_valid_name(net, dev, newname);
1214 if (err < 0) {
1215 write_seqcount_end(&devnet_rename_seq);
1216 return err;
1217 }
1218
1219 if (oldname[0] && !strchr(oldname, '%'))
1220 netdev_info(dev, "renamed from %s\n", oldname);
1221
1222 old_assign_type = dev->name_assign_type;
1223 dev->name_assign_type = NET_NAME_RENAMED;
1224
1225 rollback:
1226 ret = device_rename(&dev->dev, dev->name);
1227 if (ret) {
1228 memcpy(dev->name, oldname, IFNAMSIZ);
1229 dev->name_assign_type = old_assign_type;
1230 write_seqcount_end(&devnet_rename_seq);
1231 return ret;
1232 }
1233
1234 write_seqcount_end(&devnet_rename_seq);
1235
1236 netdev_adjacent_rename_links(dev, oldname);
1237
1238 write_lock_bh(&dev_base_lock);
1239 hlist_del_rcu(&dev->name_hlist);
1240 write_unlock_bh(&dev_base_lock);
1241
1242 synchronize_rcu();
1243
1244 write_lock_bh(&dev_base_lock);
1245 hlist_add_head_rcu(&dev->name_hlist, dev_name_hash(net,
dev->name));
1246 write_unlock_bh(&dev_base_lock);
1247
1248 if (unlikely(dev->flags & IFF_UP)) {
1249 struct netdev_notifier_change_info change_info;
1250
1251 change_info.flags_changed = 0;
&g
