target/linux/generic/backport-5.15/794-v6.2-net-core-Allow-live-renaming-when-an-interface-is-up.patch

   1 From: Andy Ren <andy.ren@getcruise.com>
   2 Date: Mon, 7 Nov 2022 09:42:42 -0800
   3 Subject: [PATCH] net/core: Allow live renaming when an interface is up
   4
   5 Allow a network interface to be renamed when the interface
   6 is up.
   7
   8 As described in the netconsole documentation [1], when netconsole is
   9 used as a built-in, it will bring up the specified interface as soon as
  10 possible. As a result, user space will not be able to rename the
  11 interface since the kernel disallows renaming of interfaces that are
  12 administratively up unless the 'IFF_LIVE_RENAME_OK' private flag was set
  13 by the kernel.
  14
  15 The original solution [2] to this problem was to add a new parameter to
  16 the netconsole configuration parameters that allows renaming of
  17 the interface used by netconsole while it is administratively up.
  18 However, during the discussion that followed, it became apparent that we
  19 have no reason to keep the current restriction and instead we should
  20 allow user space to rename interfaces regardless of their administrative
  21 state:
  22
  23 1. The restriction was put in place over 20 years ago when renaming was
  24 only possible via IOCTL and before rtnetlink started notifying user
  25 space about such changes like it does today.
  26
  27 2. The 'IFF_LIVE_RENAME_OK' flag was added over 3 years ago in version
  28 5.2 and no regressions were reported.
  29
  30 3. In-kernel listeners to 'NETDEV_CHANGENAME' do not seem to care about
  31 the administrative state of interface.
  32
  33 Therefore, allow user space to rename running interfaces by removing the
  34 restriction and the associated 'IFF_LIVE_RENAME_OK' flag. Help in
  35 possible triage by emitting a message to the kernel log that an
  36 interface was renamed while UP.
  37
  38 [1] https://www.kernel.org/doc/Documentation/networking/netconsole.rst
  39 [2] https://lore.kernel.org/netdev/20221102002420.2613004-1-andy.ren@getcruise.com/
  40
  41 Signed-off-by: Andy Ren <andy.ren@getcruise.com>
  42 Reviewed-by: Ido Schimmel <idosch@nvidia.com>
  43 Reviewed-by: David Ahern <dsahern@kernel.org>
  44 Signed-off-by: David S. Miller <davem@davemloft.net>
  45 ---
  46
  47 --- a/include/linux/netdevice.h
  48 +++ b/include/linux/netdevice.h
  49 @@ -1642,7 +1642,6 @@ struct net_device_ops {
  50   * @IFF_FAILOVER: device is a failover master device
  51   * @IFF_FAILOVER_SLAVE: device is lower dev of a failover master device
  52   * @IFF_L3MDEV_RX_HANDLER: only invoke the rx handler of L3 master device
  53 - * @IFF_LIVE_RENAME_OK: rename is allowed while device is up and running
  54   * @IFF_TX_SKB_NO_LINEAR: device/driver is capable of xmitting frames with
  55   *     skb_headlen(skb) == 0 (data starts from frag0)
  56   */
  57 @@ -1677,7 +1676,7 @@ enum netdev_priv_flags {
  58         IFF_FAILOVER                    = 1<<27,
  59         IFF_FAILOVER_SLAVE              = 1<<28,
  60         IFF_L3MDEV_RX_HANDLER           = 1<<29,
  61 -       IFF_LIVE_RENAME_OK              = 1<<30,
  62 +       /* was IFF_LIVE_RENAME_OK */
  63         IFF_TX_SKB_NO_LINEAR            = BIT_ULL(31),
  64  };
  65
  66 @@ -1711,7 +1710,6 @@ enum netdev_priv_flags {
  67  #define IFF_FAILOVER                   IFF_FAILOVER
  68  #define IFF_FAILOVER_SLAVE             IFF_FAILOVER_SLAVE
  69  #define IFF_L3MDEV_RX_HANDLER          IFF_L3MDEV_RX_HANDLER
  70 -#define IFF_LIVE_RENAME_OK             IFF_LIVE_RENAME_OK
  71  #define IFF_TX_SKB_NO_LINEAR           IFF_TX_SKB_NO_LINEAR
  72
  73  /* Specifies the type of the struct net_device::ml_priv pointer */
  74 --- a/net/core/dev.c
  75 +++ b/net/core/dev.c
  76 @@ -1242,22 +1242,6 @@ int dev_change_name(struct net_device *d
  77
  78         net = dev_net(dev);
  79
  80 -       /* Some auto-enslaved devices e.g. failover slaves are
  81 -        * special, as userspace might rename the device after
  82 -        * the interface had been brought up and running since
  83 -        * the point kernel initiated auto-enslavement. Allow
  84 -        * live name change even when these slave devices are
  85 -        * up and running.
  86 -        *
  87 -        * Typically, users of these auto-enslaving devices
  88 -        * don't actually care about slave name change, as
  89 -        * they are supposed to operate on master interface
  90 -        * directly.
  91 -        */
  92 -       if (dev->flags & IFF_UP &&
  93 -           likely(!(dev->priv_flags & IFF_LIVE_RENAME_OK)))
  94 -               return -EBUSY;
  95 -
  96         down_write(&devnet_rename_sem);
  97
  98         if (strncmp(newname, dev->name, IFNAMSIZ) == 0) {
  99 @@ -1274,7 +1258,8 @@ int dev_change_name(struct net_device *d
 100         }
 101
 102         if (oldname[0] && !strchr(oldname, '%'))
 103 -               netdev_info(dev, "renamed from %s\n", oldname);
 104 +               netdev_info(dev, "renamed from %s%s\n", oldname,
 105 +                           dev->flags & IFF_UP ? " (while UP)" : "");
 106
 107         old_assign_type = dev->name_assign_type;
 108         dev->name_assign_type = NET_NAME_RENAMED;
 109 --- a/net/core/failover.c
 110 +++ b/net/core/failover.c
 111 @@ -80,14 +80,14 @@ static int failover_slave_register(struc
 112                 goto err_upper_link;
 113         }
 114
 115 -       slave_dev->priv_flags |= (IFF_FAILOVER_SLAVE | IFF_LIVE_RENAME_OK);
 116 +       slave_dev->priv_flags |= IFF_FAILOVER_SLAVE;
 117
 118         if (fops && fops->slave_register &&
 119             !fops->slave_register(slave_dev, failover_dev))
 120                 return NOTIFY_OK;
 121
 122         netdev_upper_dev_unlink(slave_dev, failover_dev);
 123 -       slave_dev->priv_flags &= ~(IFF_FAILOVER_SLAVE | IFF_LIVE_RENAME_OK);
 124 +       slave_dev->priv_flags &= ~IFF_FAILOVER_SLAVE;
 125  err_upper_link:
 126         netdev_rx_handler_unregister(slave_dev);
 127  done:
 128 @@ -121,7 +121,7 @@ int failover_slave_unregister(struct net
 129
 130         netdev_rx_handler_unregister(slave_dev);
 131         netdev_upper_dev_unlink(slave_dev, failover_dev);
 132 -       slave_dev->priv_flags &= ~(IFF_FAILOVER_SLAVE | IFF_LIVE_RENAME_OK);
 133 +       slave_dev->priv_flags &= ~IFF_FAILOVER_SLAVE;
 134
 135         if (fops && fops->slave_unregister &&
 136             !fops->slave_unregister(slave_dev, failover_dev))