[RFC 0/1] Move IFF_LIVE_ADDR_CHANGE to public flag

[RFC 0/1] Move IFF_LIVE_ADDR_CHANGE to public flag

[James Prestwood]

Most of the motivation behind this is in the commit description, but
I'm sending this as an RFC since I'm not fully sure messing with these
flags is ok in terms of backwards compatibility. There is also a bit
more info thats out of scope of a commit description.

Originally I tried to achieve this same behavior but only touching
the wireless subsystem. This was easy enough but the critical piece
was exposing some userspace flag. Without this there isn't much
point in allowing a live address change from userspace since there
is no way of knowing if its possible ahead of time. The original
motivation was also time savings, not related to address randomization.

The wireless maintainers weren't keen on adding a flag in nl80211
since this functionality isn't wireless specific.

Now with the addition of 6GHz we ran into this issue with address
randomization and I'm now reviving the old patches, but taking
the comments from the wireless maintainers and putting this
userspace flag into RTNL rather than nl80211.

Here are the archives to the original thread:
https://lore.kernel.org/linux-wireless/20190913195908.7871-1-prestwoj@gmail.com/

Before I CC a ton of maintainers (since I'm touching so many drivers)
I wanted to get a general answer to whether or not this patch would
be accepted, or if we need to go another route like push back on
wireless or maybe another suggestion.

James Prestwood (1):
  net: move IFF_LIVE_ADDR_CHANGE to public flag

 drivers/infiniband/ulp/ipoib/ipoib_main.c     |  2 +-
 .../infiniband/ulp/opa_vnic/opa_vnic_netdev.c |  2 +-
 drivers/net/dummy.c                           |  4 +--
 .../net/ethernet/aquantia/atlantic/aq_nic.c   |  2 +-
 .../net/ethernet/freescale/dpaa/dpaa_eth.c    |  2 +-
 .../net/ethernet/freescale/dpaa2/dpaa2-eth.c  |  3 +-
 drivers/net/ethernet/freescale/gianfar.c      |  2 +-
 drivers/net/ethernet/marvell/mvneta.c         |  2 +-
 .../ethernet/netronome/nfp/nfp_net_common.c   |  2 +-
 .../net/ethernet/netronome/nfp/nfp_net_repr.c |  2 +-
 .../net/ethernet/pensando/ionic/ionic_lif.c   |  5 +--
 drivers/net/ethernet/realtek/r8169_main.c     |  2 +-
 drivers/net/geneve.c                          |  3 +-
 drivers/net/loopback.c                        |  4 +--
 drivers/net/netdevsim/netdev.c                |  5 ++-
 drivers/net/ntb_netdev.c                      |  2 +-
 drivers/net/team/team.c                       |  3 +-
 drivers/net/tun.c                             |  2 +-
 drivers/net/veth.c                            |  2 +-
 drivers/net/virtio_net.c                      |  4 +--
 drivers/net/vrf.c                             |  2 +-
 drivers/net/vxlan/vxlan_core.c                |  2 +-
 include/linux/netdevice.h                     | 36 +++++++++----------
 include/uapi/linux/if.h                       |  7 +++-
 net/ethernet/eth.c                            |  2 +-
 net/ipv4/ip_gre.c                             |  8 ++---
 net/ipv6/ip6_gre.c                            |  8 ++---
 net/ncsi/ncsi-rsp.c                           |  6 ++--
 net/openvswitch/vport-internal_dev.c          |  4 +--
 29 files changed, 67 insertions(+), 63 deletions(-)

-- 
2.34.3

[RFC 1/1] net: move IFF_LIVE_ADDR_CHANGE to public flag

[James Prestwood]

Devices which do not support this flag need to be brought down prior
to changing their address. Internally the kernel can access the private
flags to check whether or not a power down is required, but from
userspace there is no such flag. Without some way of knowing the
device capability userspace cannot efficiently change the address. The
safest route is to always power down.

The motivation for this change is aimed at the wireless subsystem due
to the consequences of a firmware reboot. When the firmware reboots it
clears all wireless regulatory information (for self-managed devices)
and upon startup again the regulatory domain is set to OO/XX. This
disables frequencies which were once available, and will not be allowed
to use until the regulatory domain is set again. Doing this is out of
userspace control, and actually requires a time-intensive scan to
collect enough wireless beacons to determine the country.

This poses a major problem if the device needs to randomize its MAC
address for a connection. If that connection is on a frequency which
is not allowed in the world domain (6GHz is 100% disallowed, and many
other 5/2.4GHz frequencies are also disabled in world roaming) you
essentially cannot randomize you're address since a firmware reboot
would disallow the connection once it came back up.

By exposing IFF_LIVE_ADDR_CHANGE to userspace it at least gives an
indication that we can successfully randomize the address and
connect. In the worst case address randomization can be avoided
ahead of time. A secondary win is also time, since userspace can
avoid a power down unless its required which saves some time.

Signed-off-by: James Prestwood <prestwoj@gmail.com>
---
 drivers/infiniband/ulp/ipoib/ipoib_main.c     |  2 +-
 .../infiniband/ulp/opa_vnic/opa_vnic_netdev.c |  2 +-
 drivers/net/dummy.c                           |  4 +--
 .../net/ethernet/aquantia/atlantic/aq_nic.c   |  2 +-
 .../net/ethernet/freescale/dpaa/dpaa_eth.c    |  2 +-
 .../net/ethernet/freescale/dpaa2/dpaa2-eth.c  |  3 +-
 drivers/net/ethernet/freescale/gianfar.c      |  2 +-
 drivers/net/ethernet/marvell/mvneta.c         |  2 +-
 .../ethernet/netronome/nfp/nfp_net_common.c   |  2 +-
 .../net/ethernet/netronome/nfp/nfp_net_repr.c |  2 +-
 .../net/ethernet/pensando/ionic/ionic_lif.c   |  5 +--
 drivers/net/ethernet/realtek/r8169_main.c     |  2 +-
 drivers/net/geneve.c                          |  3 +-
 drivers/net/loopback.c                        |  4 +--
 drivers/net/netdevsim/netdev.c                |  5 ++-
 drivers/net/ntb_netdev.c                      |  2 +-
 drivers/net/team/team.c                       |  3 +-
 drivers/net/tun.c                             |  2 +-
 drivers/net/veth.c                            |  2 +-
 drivers/net/virtio_net.c                      |  4 +--
 drivers/net/vrf.c                             |  2 +-
 drivers/net/vxlan/vxlan_core.c                |  2 +-
 include/linux/netdevice.h                     | 36 +++++++++----------
 include/uapi/linux/if.h                       |  7 +++-
 net/ethernet/eth.c                            |  2 +-
 net/ipv4/ip_gre.c                             |  8 ++---
 net/ipv6/ip6_gre.c                            |  8 ++---
 net/ncsi/ncsi-rsp.c                           |  6 ++--
 net/openvswitch/vport-internal_dev.c          |  4 +--
 29 files changed, 67 insertions(+), 63 deletions(-)

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index 9934b8bd7f56..5de29c2f8261 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -2367,7 +2367,7 @@ static int ipoib_set_mac(struct net_device *dev, void *addr)
 	struct sockaddr_storage *ss = addr;
 	int ret;
 
-	if (!(dev->priv_flags & IFF_LIVE_ADDR_CHANGE) && netif_running(dev))
+	if (!(dev->flags & IFF_LIVE_ADDR_CHANGE) && netif_running(dev))
 		return -EBUSY;
 
 	ret = ipoib_check_lladdr(dev, ss);
diff --git a/drivers/infiniband/ulp/opa_vnic/opa_vnic_netdev.c b/drivers/infiniband/ulp/opa_vnic/opa_vnic_netdev.c
index 071f35711468..87c7d1042fc5 100644
--- a/drivers/infiniband/ulp/opa_vnic/opa_vnic_netdev.c
+++ b/drivers/infiniband/ulp/opa_vnic/opa_vnic_netdev.c
@@ -353,7 +353,7 @@ struct opa_vnic_adapter *opa_vnic_add_netdev(struct ib_device *ibdev,
 	adapter->rn_ops = netdev->netdev_ops;
 
 	netdev->netdev_ops = &opa_netdev_ops;
-	netdev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	netdev->flags |= IFF_LIVE_ADDR_CHANGE;
 	netdev->hard_header_len += OPA_VNIC_SKB_HEADROOM;
 	mutex_init(&adapter->lock);
 	mutex_init(&adapter->mactbl_lock);
diff --git a/drivers/net/dummy.c b/drivers/net/dummy.c
index f82ad7419508..f02bc360ce7d 100644
--- a/drivers/net/dummy.c
+++ b/drivers/net/dummy.c
@@ -120,9 +120,9 @@ static void dummy_setup(struct net_device *dev)
 	dev->needs_free_netdev = true;
 
 	/* Fill in device structure with ethernet-generic values. */
-	dev->flags |= IFF_NOARP;
+	dev->flags |= IFF_NOARP | IFF_LIVE_ADDR_CHANGE;
 	dev->flags &= ~IFF_MULTICAST;
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
+	dev->priv_flags |= IFF_NO_QUEUE;
 	dev->features	|= NETIF_F_SG | NETIF_F_FRAGLIST;
 	dev->features	|= NETIF_F_GSO_SOFTWARE;
 	dev->features	|= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
diff --git a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
index 24d715c28a35..46b8135f67ea 100644
--- a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
+++ b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
@@ -380,7 +380,7 @@ void aq_nic_ndev_init(struct aq_nic_s *self)
 				     NETIF_F_LRO | NETIF_F_TSO | NETIF_F_TSO6;
 	self->ndev->gso_partial_features = NETIF_F_GSO_UDP_L4;
 	self->ndev->priv_flags = aq_hw_caps->hw_priv_flags;
-	self->ndev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	self->ndev->flags |= IFF_LIVE_ADDR_CHANGE;
 
 	self->msg_enable = NETIF_MSG_DRV | NETIF_MSG_LINK;
 	self->ndev->mtu = aq_nic_cfg->mtu - ETH_HLEN;
diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
index c78883c3a2c8..bd278f14f814 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
@@ -259,7 +259,7 @@ static int dpaa_netdev_init(struct net_device *net_dev,
 	net_dev->features |= NETIF_F_GSO;
 	net_dev->features |= NETIF_F_RXCSUM;
 
-	net_dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	net_dev->flags |= IFF_LIVE_ADDR_CHANGE;
 	/* we do not want shared skbs on TX */
 	net_dev->priv_flags &= ~IFF_TX_SKB_SHARING;
 
diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
index 4b047255d928..7b5f6730008f 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
@@ -4375,8 +4375,6 @@ static int dpaa2_eth_netdev_init(struct net_device *net_dev)
 	dpaa2_eth_detect_features(priv);
 
 	/* Capabilities listing */
-	supported |= IFF_LIVE_ADDR_CHANGE;
-
 	if (options & DPNI_OPT_NO_MAC_FILTER)
 		not_supported |= IFF_UNICAST_FLT;
 	else
@@ -4384,6 +4382,7 @@ static int dpaa2_eth_netdev_init(struct net_device *net_dev)
 
 	net_dev->priv_flags |= supported;
 	net_dev->priv_flags &= ~not_supported;
+	net_dev->flags |= IFF_LIVE_ADDR_CHANGE;
 
 	/* Features */
 	net_dev->features = NETIF_F_RXCSUM |
diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index 206b7a35eaf5..01f644853fda 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -3250,7 +3250,7 @@ static int gfar_probe(struct platform_device *ofdev)
 		dev->features |= NETIF_F_HW_VLAN_CTAG_RX;
 	}
 
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 
 	gfar_init_addr_hash_table(priv);
 
diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 934f6dd90992..c1b4374ffe76 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -5598,7 +5598,7 @@ static int mvneta_probe(struct platform_device *pdev)
 			NETIF_F_TSO | NETIF_F_RXCSUM;
 	dev->hw_features |= dev->features;
 	dev->vlan_features |= dev->features;
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 	netif_set_gso_max_segs(dev, MVNETA_MAX_TSO_SEGS);
 
 	/* MTU range: 68 - 9676 */
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
index b412670d89b2..a79d2d1ca0ca 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
@@ -2235,7 +2235,7 @@ static void nfp_net_netdev_init(struct nfp_net *nn)
 	 * supported.  By default we enable most features.
 	 */
 	if (nn->cap & NFP_NET_CFG_CTRL_LIVE_ADDR)
-		netdev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+		netdev->flags |= IFF_LIVE_ADDR_CHANGE;
 
 	netdev->hw_features = NETIF_F_HIGHDMA;
 	if (nn->cap & NFP_NET_CFG_CTRL_RXCSUM_ANY) {
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
index ba3fa7eac98d..6b65aa9220c9 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
@@ -339,7 +339,7 @@ int nfp_repr_init(struct nfp_app *app, struct net_device *netdev,
 
 	/* Set features the lower device can support with representors */
 	if (repr_cap & NFP_NET_CFG_CTRL_LIVE_ADDR)
-		netdev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+		netdev->flags |= IFF_LIVE_ADDR_CHANGE;
 
 	netdev->hw_features = NETIF_F_HIGHDMA;
 	if (repr_cap & NFP_NET_CFG_CTRL_RXCSUM_ANY)
diff --git a/drivers/net/ethernet/pensando/ionic/ionic_lif.c b/drivers/net/ethernet/pensando/ionic/ionic_lif.c
index f3568901eb91..8a285a1149ab 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_lif.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_lif.c
@@ -1544,8 +1544,9 @@ static int ionic_init_nic_features(struct ionic_lif *lif)
 	netdev->features |= netdev->hw_features;
 	netdev->vlan_features |= netdev->features & ~NETIF_F_VLAN_FEATURES;
 
-	netdev->priv_flags |= IFF_UNICAST_FLT |
-			      IFF_LIVE_ADDR_CHANGE;
+	netdev->priv_flags |= IFF_UNICAST_FLT;
+	netdev->flags |= IFF_LIVE_ADDR_CHANGE;
+
 
 	return 0;
 }
diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
index 33f5c5698ccb..ac26b9e97513 100644
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -5420,7 +5420,7 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	dev->hw_features = NETIF_F_IP_CSUM | NETIF_F_RXCSUM |
 			   NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_CTAG_RX;
 	dev->vlan_features = NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_TSO;
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 
 	/*
 	 * Pretend we are using VLANs; This bypasses a nasty bug where
diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index 7db6c135ac6c..03ea394f6b85 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -1257,7 +1257,8 @@ static void geneve_setup(struct net_device *dev)
 
 	netif_keep_dst(dev);
 	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
+	dev->priv_flags |= IFF_NO_QUEUE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 	eth_hw_addr_random(dev);
 }
 
diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index 720394c0639b..355edd31a4d2 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -172,8 +172,8 @@ static void gen_lo_setup(struct net_device *dev,
 	dev->min_header_len	= ETH_HLEN;	/* 14	*/
 	dev->addr_len		= ETH_ALEN;	/* 6	*/
 	dev->type		= ARPHRD_LOOPBACK;	/* 0x0001*/
-	dev->flags		= IFF_LOOPBACK;
-	dev->priv_flags		|= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
+	dev->flags		= IFF_LOOPBACK | IFF_LIVE_ADDR_CHANGE;
+	dev->priv_flags		|= IFF_NO_QUEUE;
 	netif_keep_dst(dev);
 	dev->hw_features	= NETIF_F_GSO_SOFTWARE;
 	dev->features		= NETIF_F_SG | NETIF_F_FRAGLIST
diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index e470e3398abc..cdf18078f002 100644
--- a/drivers/net/netdevsim/netdev.c
+++ b/drivers/net/netdevsim/netdev.c
@@ -284,10 +284,9 @@ static void nsim_setup(struct net_device *dev)
 	eth_hw_addr_random(dev);
 
 	dev->tx_queue_len = 0;
-	dev->flags |= IFF_NOARP;
+	dev->flags |= IFF_NOARP | IFF_LIVE_ADDR_CHANGE;
 	dev->flags &= ~IFF_MULTICAST;
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE |
-			   IFF_NO_QUEUE;
+	dev->priv_flags |= IFF_NO_QUEUE;
 	dev->features |= NETIF_F_HIGHDMA |
 			 NETIF_F_SG |
 			 NETIF_F_FRAGLIST |
diff --git a/drivers/net/ntb_netdev.c b/drivers/net/ntb_netdev.c
index 80bdc07f2cd3..103bca43fd4d 100644
--- a/drivers/net/ntb_netdev.c
+++ b/drivers/net/ntb_netdev.c
@@ -422,7 +422,7 @@ static int ntb_netdev_probe(struct device *client_dev)
 	dev->pdev = pdev;
 	ndev->features = NETIF_F_HIGHDMA;
 
-	ndev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	ndev->flags |= IFF_LIVE_ADDR_CHANGE;
 
 	ndev->hw_features = ndev->features;
 	ndev->watchdog_timeo = msecs_to_jiffies(NTB_TX_TIMEOUT_MS);
diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c
index b07dde6f0abf..1d82f0130831 100644
--- a/drivers/net/team/team.c
+++ b/drivers/net/team/team.c
@@ -2168,7 +2168,8 @@ static void team_setup(struct net_device *dev)
 	 * bring us to promisc mode in case a unicast addr is added.
 	 * Let this up to underlay drivers.
 	 */
-	dev->priv_flags |= IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->priv_flags |= IFF_UNICAST_FLT;
 
 	dev->features |= NETIF_F_LLTX;
 	dev->features |= NETIF_F_GRO;
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index dbe4c0a4be2c..53bd5dac0551 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1385,7 +1385,7 @@ static void tun_net_initialize(struct net_device *dev)
 		/* Ethernet TAP Device */
 		ether_setup(dev);
 		dev->priv_flags &= ~IFF_TX_SKB_SHARING;
-		dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+		dev->flags |= IFF_LIVE_ADDR_CHANGE;
 
 		eth_hw_addr_random(dev);
 
diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index eb0121a64d6d..30366c4964bb 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -1627,9 +1627,9 @@ static void veth_setup(struct net_device *dev)
 	ether_setup(dev);
 
 	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
 	dev->priv_flags |= IFF_NO_QUEUE;
 	dev->priv_flags |= IFF_PHONY_HEADROOM;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 
 	dev->netdev_ops = &veth_netdev_ops;
 	dev->ethtool_ops = &veth_ethtool_ops;
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index cbba9d2e8f32..bf836450c468 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3481,8 +3481,8 @@ static int virtnet_probe(struct virtio_device *vdev)
 		return -ENOMEM;
 
 	/* Set up network device as normal. */
-	dev->priv_flags |= IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE |
-			   IFF_TX_SKB_NO_LINEAR;
+	dev->priv_flags |= IFF_UNICAST_FLT | IFF_TX_SKB_NO_LINEAR;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 	dev->netdev_ops = &virtnet_netdev;
 	dev->features = NETIF_F_HIGHDMA;
 
diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
index cfc30ce4c6e1..0900bacff9b5 100644
--- a/drivers/net/vrf.c
+++ b/drivers/net/vrf.c
@@ -1697,7 +1697,7 @@ static void vrf_setup(struct net_device *dev)
 	/* default to no qdisc; user can add if desired */
 	dev->priv_flags |= IFF_NO_QUEUE;
 	dev->priv_flags |= IFF_NO_RX_HANDLER;
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 
 	/* VRF devices do not care about MTU, but if the MTU is set
 	 * too low then the ipv4 and ipv6 protocols are disabled
diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index 8a5e3a6d32d7..16dda95d9c6e 100644
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -3177,7 +3177,7 @@ static void vxlan_setup(struct net_device *dev)
 static void vxlan_ether_setup(struct net_device *dev)
 {
 	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 	dev->netdev_ops = &vxlan_netdev_ether_ops;
 }
 
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index f736c020cde2..6b75d813f4af 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1637,24 +1637,23 @@ enum netdev_priv_flags {
 	IFF_UNICAST_FLT			= 1<<12,
 	IFF_TEAM_PORT			= 1<<13,
 	IFF_SUPP_NOFCS			= 1<<14,
-	IFF_LIVE_ADDR_CHANGE		= 1<<15,
-	IFF_MACVLAN			= 1<<16,
-	IFF_XMIT_DST_RELEASE_PERM	= 1<<17,
-	IFF_L3MDEV_MASTER		= 1<<18,
-	IFF_NO_QUEUE			= 1<<19,
-	IFF_OPENVSWITCH			= 1<<20,
-	IFF_L3MDEV_SLAVE		= 1<<21,
-	IFF_TEAM			= 1<<22,
-	IFF_RXFH_CONFIGURED		= 1<<23,
-	IFF_PHONY_HEADROOM		= 1<<24,
-	IFF_MACSEC			= 1<<25,
-	IFF_NO_RX_HANDLER		= 1<<26,
-	IFF_FAILOVER			= 1<<27,
-	IFF_FAILOVER_SLAVE		= 1<<28,
-	IFF_L3MDEV_RX_HANDLER		= 1<<29,
-	IFF_LIVE_RENAME_OK		= 1<<30,
-	IFF_TX_SKB_NO_LINEAR		= 1<<31,
-	IFF_CHANGE_PROTO_DOWN		= BIT_ULL(32),
+	IFF_MACVLAN			= 1<<15,
+	IFF_XMIT_DST_RELEASE_PERM	= 1<<16,
+	IFF_L3MDEV_MASTER		= 1<<17,
+	IFF_NO_QUEUE			= 1<<18,
+	IFF_OPENVSWITCH			= 1<<19,
+	IFF_L3MDEV_SLAVE		= 1<<20,
+	IFF_TEAM			= 1<<21,
+	IFF_RXFH_CONFIGURED		= 1<<22,
+	IFF_PHONY_HEADROOM		= 1<<23,
+	IFF_MACSEC			= 1<<24,
+	IFF_NO_RX_HANDLER		= 1<<25,
+	IFF_FAILOVER			= 1<<26,
+	IFF_FAILOVER_SLAVE		= 1<<27,
+	IFF_L3MDEV_RX_HANDLER		= 1<<28,
+	IFF_LIVE_RENAME_OK		= 1<<29,
+	IFF_TX_SKB_NO_LINEAR		= 1<<30,
+	IFF_CHANGE_PROTO_DOWN		= BIT_ULL(31),
 };
 
 #define IFF_802_1Q_VLAN			IFF_802_1Q_VLAN
@@ -1672,7 +1671,6 @@ enum netdev_priv_flags {
 #define IFF_UNICAST_FLT			IFF_UNICAST_FLT
 #define IFF_TEAM_PORT			IFF_TEAM_PORT
 #define IFF_SUPP_NOFCS			IFF_SUPP_NOFCS
-#define IFF_LIVE_ADDR_CHANGE		IFF_LIVE_ADDR_CHANGE
 #define IFF_MACVLAN			IFF_MACVLAN
 #define IFF_XMIT_DST_RELEASE_PERM	IFF_XMIT_DST_RELEASE_PERM
 #define IFF_L3MDEV_MASTER		IFF_L3MDEV_MASTER
diff --git a/include/uapi/linux/if.h b/include/uapi/linux/if.h
index 797ba2c1562a..111b077b2d4e 100644
--- a/include/uapi/linux/if.h
+++ b/include/uapi/linux/if.h
@@ -78,6 +78,8 @@
  * @IFF_LOWER_UP: driver signals L1 up. Volatile.
  * @IFF_DORMANT: driver signals dormant. Volatile.
  * @IFF_ECHO: echo sent packets. Volatile.
+ * @IFF_LIVE_ADDR_CHANGE: device supports hardware address
+ *	change when it's running. Volatile
  */
 enum net_device_flags {
 /* for compatibility with glibc net/if.h */
@@ -103,6 +105,7 @@ enum net_device_flags {
 	IFF_LOWER_UP			= 1<<16, /* volatile */
 	IFF_DORMANT			= 1<<17, /* volatile */
 	IFF_ECHO			= 1<<18, /* volatile */
+	IFF_LIVE_ADDR_CHANGE		= 1<<19, /* volatile */
 #endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */
 };
 #endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO != 0 || __UAPI_DEF_IF_NET_DEVICE_FLAGS != 0 */
@@ -131,10 +134,12 @@ enum net_device_flags {
 #define IFF_LOWER_UP			IFF_LOWER_UP
 #define IFF_DORMANT			IFF_DORMANT
 #define IFF_ECHO			IFF_ECHO
+#define IFF_LIVE_ADDR_CHANGE		IFF_LIVE_ADDR_CHANGE
 #endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */
 
 #define IFF_VOLATILE	(IFF_LOOPBACK|IFF_POINTOPOINT|IFF_BROADCAST|IFF_ECHO|\
-		IFF_MASTER|IFF_SLAVE|IFF_RUNNING|IFF_LOWER_UP|IFF_DORMANT)
+		IFF_MASTER|IFF_SLAVE|IFF_RUNNING|IFF_LOWER_UP|IFF_DORMANT|\
+		IFF_LIVE_ADDR_CHANGE)
 
 #define IF_GET_IFACE	0x0001		/* for querying only */
 #define IF_GET_PROTO	0x0002
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index ebcc812735a4..b32301b72070 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -288,7 +288,7 @@ int eth_prepare_mac_addr_change(struct net_device *dev, void *p)
 {
 	struct sockaddr *addr = p;
 
-	if (!(dev->priv_flags & IFF_LIVE_ADDR_CHANGE) && netif_running(dev))
+	if (!(dev->flags & IFF_LIVE_ADDR_CHANGE) && netif_running(dev))
 		return -EBUSY;
 	if (!is_valid_ether_addr(addr->sa_data))
 		return -EADDRNOTAVAIL;
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index aacee9dd771b..cc0c977b36a9 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1271,7 +1271,7 @@ static bool ipgre_netlink_encap_parms(struct nlattr *data[],
 static int gre_tap_init(struct net_device *dev)
 {
 	__gre_tunnel_init(dev);
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 	netif_keep_dst(dev);
 
 	return ip_tunnel_init(dev);
@@ -1304,7 +1304,7 @@ static int erspan_tunnel_init(struct net_device *dev)
 
 	dev->features		|= GRE_FEATURES;
 	dev->hw_features	|= GRE_FEATURES;
-	dev->priv_flags		|= IFF_LIVE_ADDR_CHANGE;
+	dev->flags		|= IFF_LIVE_ADDR_CHANGE;
 	netif_keep_dst(dev);
 
 	return ip_tunnel_init(dev);
@@ -1328,7 +1328,7 @@ static void ipgre_tap_setup(struct net_device *dev)
 	dev->max_mtu = 0;
 	dev->netdev_ops	= &gre_tap_netdev_ops;
 	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
-	dev->priv_flags	|= IFF_LIVE_ADDR_CHANGE;
+	dev->flags	|= IFF_LIVE_ADDR_CHANGE;
 	ip_tunnel_setup(dev, gre_tap_net_id);
 }
 
@@ -1560,7 +1560,7 @@ static void erspan_setup(struct net_device *dev)
 	dev->max_mtu = 0;
 	dev->netdev_ops = &erspan_netdev_ops;
 	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 	ip_tunnel_setup(dev, erspan_net_id);
 	t->erspan_ver = 1;
 }
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 5136959b3dc5..ab81445b1954 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -1832,7 +1832,7 @@ static int ip6gre_tap_init(struct net_device *dev)
 	if (ret)
 		return ret;
 
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 
 	return 0;
 }
@@ -1892,7 +1892,7 @@ static int ip6erspan_tap_init(struct net_device *dev)
 	if (!(tunnel->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
 		dev->mtu -= 8;
 
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 	ip6erspan_tnl_link_config(tunnel, 1);
 
 	dev_hold_track(dev, &tunnel->dev_tracker, GFP_KERNEL);
@@ -1928,7 +1928,7 @@ static void ip6gre_tap_setup(struct net_device *dev)
 	dev->priv_destructor = ip6gre_dev_free;
 
 	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 	netif_keep_dst(dev);
 }
 
@@ -2228,7 +2228,7 @@ static void ip6erspan_tap_setup(struct net_device *dev)
 	dev->priv_destructor = ip6gre_dev_free;
 
 	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
-	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	dev->flags |= IFF_LIVE_ADDR_CHANGE;
 	netif_keep_dst(dev);
 }
 
diff --git a/net/ncsi/ncsi-rsp.c b/net/ncsi/ncsi-rsp.c
index 6447a09932f5..05e93e4e131b 100644
--- a/net/ncsi/ncsi-rsp.c
+++ b/net/ncsi/ncsi-rsp.c
@@ -625,7 +625,7 @@ static int ncsi_rsp_handler_oem_mlx_gma(struct ncsi_request *nr)
 	rsp = (struct ncsi_rsp_oem_pkt *)skb_network_header(nr->rsp);
 
 	saddr.sa_family = ndev->type;
-	ndev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	ndev->flags |= IFF_LIVE_ADDR_CHANGE;
 	memcpy(saddr.sa_data, &rsp->data[MLX_MAC_ADDR_OFFSET], ETH_ALEN);
 	/* Set the flag for GMA command which should only be called once */
 	ndp->gma_flag = 1;
@@ -667,7 +667,7 @@ static int ncsi_rsp_handler_oem_bcm_gma(struct ncsi_request *nr)
 	rsp = (struct ncsi_rsp_oem_pkt *)skb_network_header(nr->rsp);
 
 	saddr.sa_family = ndev->type;
-	ndev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	ndev->flags |= IFF_LIVE_ADDR_CHANGE;
 	memcpy(saddr.sa_data, &rsp->data[BCM_MAC_ADDR_OFFSET], ETH_ALEN);
 	/* Increase mac address by 1 for BMC's address */
 	eth_addr_inc((u8 *)saddr.sa_data);
@@ -713,7 +713,7 @@ static int ncsi_rsp_handler_oem_intel_gma(struct ncsi_request *nr)
 	rsp = (struct ncsi_rsp_oem_pkt *)skb_network_header(nr->rsp);
 
 	saddr.sa_family = ndev->type;
-	ndev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+	ndev->flags |= IFF_LIVE_ADDR_CHANGE;
 	memcpy(saddr.sa_data, &rsp->data[INTEL_MAC_ADDR_OFFSET], ETH_ALEN);
 	/* Increase mac address by 1 for BMC's address */
 	eth_addr_inc((u8 *)saddr.sa_data);
diff --git a/net/openvswitch/vport-internal_dev.c b/net/openvswitch/vport-internal_dev.c
index 5b2ee9c1c00b..dbe39b6ddddb 100644
--- a/net/openvswitch/vport-internal_dev.c
+++ b/net/openvswitch/vport-internal_dev.c
@@ -101,8 +101,8 @@ static void do_setup(struct net_device *netdev)
 	netdev->netdev_ops = &internal_dev_netdev_ops;
 
 	netdev->priv_flags &= ~IFF_TX_SKB_SHARING;
-	netdev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_OPENVSWITCH |
-			      IFF_NO_QUEUE;
+	netdev->priv_flags |= IFF_OPENVSWITCH | IFF_NO_QUEUE;
+	netdev->flags |= IFF_LIVE_ADDR_CHANGE;
 	netdev->needs_free_netdev = true;
 	netdev->priv_destructor = NULL;
 	netdev->ethtool_ops = &internal_dev_ethtool_ops;
-- 
2.34.3

Re: [RFC 1/1] net: move IFF_LIVE_ADDR_CHANGE to public flag

[Stephen Hemminger]

On Thu,  4 Aug 2022 10:43:07 -0700
James Prestwood <prestwoj@gmail.com> wrote:

> + * @IFF_LIVE_ADDR_CHANGE: device supports hardware address
> + *	change when it's running. Volatile

Since this is a property of the device driver, why is it volatile?

When you make it part of uapi, you also want to restrict userspace
from changing the value via sysfs?

Re: [RFC 1/1] net: move IFF_LIVE_ADDR_CHANGE to public flag

[Jakub Kicinski]

On Thu,  4 Aug 2022 10:43:07 -0700 James Prestwood wrote:
> By exposing IFF_LIVE_ADDR_CHANGE to userspace it at least gives an
> indication that we can successfully randomize the address and
> connect. In the worst case address randomization can be avoided
> ahead of time. A secondary win is also time, since userspace can
> avoid a power down unless its required which saves some time.

It's not a generic thing tho, it's most of an implicit argument 
to eth_mac_addr(). Not all netdevs are Ethernet.

The semantics in wireless are also a little stretched because normally
if the flag is not set the netdev will _refuse_ (-EBUSY) to change the
address while running, not do some crazy fw reset.

Perhaps we should wait for Johannes to return form vacation but my
immediate reaction would be to add a knob (in wireless?) that controls
whether the reset dance is allowed.

Re: [RFC 1/1] net: move IFF_LIVE_ADDR_CHANGE to public flag

[James Prestwood]

On Thu, 2022-08-04 at 11:43 -0700, Jakub Kicinski wrote:
> On Thu,  4 Aug 2022 10:43:07 -0700 James Prestwood wrote:
> > By exposing IFF_LIVE_ADDR_CHANGE to userspace it at least gives an
> > indication that we can successfully randomize the address and
> > connect. In the worst case address randomization can be avoided
> > ahead of time. A secondary win is also time, since userspace can
> > avoid a power down unless its required which saves some time.
> 
> It's not a generic thing tho, it's most of an implicit argument 
> to eth_mac_addr(). Not all netdevs are Ethernet.
> 
> The semantics in wireless are also a little stretched because
> normally
> if the flag is not set the netdev will _refuse_ (-EBUSY) to change
> the
> address while running, not do some crazy fw reset.

Sorry if I wasn't clear, but its not nl80211 doing the fw reset
automatically. The wireless subsystem actually completely disallows a
MAC change if the device is running, this flag isn't even checked. This
means userspace has to bring the device down itself, then change the
MAC.

I plan on also modifying mac80211 to first check this flag and allow a
live MAC change if possible. But ultimately userspace still needs to be
aware of the support.

> 
> Perhaps we should wait for Johannes to return form vacation but my
> immediate reaction would be to add a knob (in wireless?) that
> controls
> whether the reset dance is allowed.

Ok sounds good. Lets see what Johannes has to say.

Re: [RFC 1/1] net: move IFF_LIVE_ADDR_CHANGE to public flag

[James Prestwood]

Hi,

On Thu, 2022-08-04 at 10:59 -0700, Stephen Hemminger wrote:
> On Thu,  4 Aug 2022 10:43:07 -0700
> James Prestwood <prestwoj@gmail.com> wrote:
> 
> > + * @IFF_LIVE_ADDR_CHANGE: device supports hardware address
> > + *     change when it's running. Volatile
> 
> Since this is a property of the device driver, why is it volatile?

Its not intended to be changed since its a device capability.


> When you make it part of uapi, you also want to restrict userspace
> from changing the value via sysfs?
> 

Yeah, this is what I intended to do. Similar to the other volatile
options. Basically following this comment:

"...few flags can be toggled and some other flags are always preserved
from the original net_device flags even if you try to set them via
sysfs. Flags which are always preserved are kept under the flag
grouping @IFF_VOLATILE. Flags which are volatile are annotated below as
such."

Thanks,
James

Re: [RFC 1/1] net: move IFF_LIVE_ADDR_CHANGE to public flag

[James Prestwood]

Forgot to CC Johannes.

Thanks

On Thu, 2022-08-04 at 12:23 -0700, James Prestwood wrote:
> On Thu, 2022-08-04 at 11:43 -0700, Jakub Kicinski wrote:
> > On Thu,  4 Aug 2022 10:43:07 -0700 James Prestwood wrote:
> > > By exposing IFF_LIVE_ADDR_CHANGE to userspace it at least gives
> > > an
> > > indication that we can successfully randomize the address and
> > > connect. In the worst case address randomization can be avoided
> > > ahead of time. A secondary win is also time, since userspace can
> > > avoid a power down unless its required which saves some time.
> > 
> > It's not a generic thing tho, it's most of an implicit argument 
> > to eth_mac_addr(). Not all netdevs are Ethernet.
> > 
> > The semantics in wireless are also a little stretched because
> > normally
> > if the flag is not set the netdev will _refuse_ (-EBUSY) to change
> > the
> > address while running, not do some crazy fw reset.
> 
> Sorry if I wasn't clear, but its not nl80211 doing the fw reset
> automatically. The wireless subsystem actually completely disallows a
> MAC change if the device is running, this flag isn't even checked.
> This
> means userspace has to bring the device down itself, then change the
> MAC.
> 
> I plan on also modifying mac80211 to first check this flag and allow
> a
> live MAC change if possible. But ultimately userspace still needs to
> be
> aware of the support.
> 
> > 
> > Perhaps we should wait for Johannes to return form vacation but my
> > immediate reaction would be to add a knob (in wireless?) that
> > controls
> > whether the reset dance is allowed.
> 
> Ok sounds good. Lets see what Johannes has to say.
> 

Re: [RFC 0/1] Move IFF_LIVE_ADDR_CHANGE to public flag

[Andrew Lunn]

>   net: move IFF_LIVE_ADDR_CHANGE to public flag

If this concept is accepted, i would actually change the flag name a
little. That will help developers know the semantics of the flag have
changed when their code fails to compile. Maybe make the public flag
IFF_ADDR_CHANGE_LIVE?

	Andrew

Re: [RFC 1/1] net: move IFF_LIVE_ADDR_CHANGE to public flag

[Johannes Berg]

On Thu, 2022-08-04 at 12:49 -0700, James Prestwood wrote:
> > > 
> > > The semantics in wireless are also a little stretched because
> > > normally
> > > if the flag is not set the netdev will _refuse_ (-EBUSY) to change
> > > the
> > > address while running, not do some crazy fw reset.
> > 
> > Sorry if I wasn't clear, but its not nl80211 doing the fw reset
> > automatically. The wireless subsystem actually completely disallows a
> > MAC change if the device is running, this flag isn't even checked.
> > This
> > means userspace has to bring the device down itself, then change the
> > MAC.
> > 
> > I plan on also modifying mac80211 to first check this flag and allow
> > a
> > live MAC change if possible. But ultimately userspace still needs to
> > be
> > aware of the support.
> > 

I'm not sure this is the right approach.

For the stated purpose (not powering down the NIC), with most mac80211
drivers the following would work:

 - add a new virtual interface of any supported type, and bring it up
 - bring down the other interface, change MAC address, bring it up again
 - remove the interface added in step 1

though obviously that's not a good way to do it!

But internally in mac80211, there's a distinction between

 ->stop() to turn off the NIC, and
 ->remove_interface() to remove the interface.

Changing the MAC address should always be possible when the interface
doesn't exist in the driver (remove_interface), but without stop()ing
the NIC.

However, obviously remove_interface() implies that you break the
connection first, and obviously you cannot change the MAC address
without breaking the connection (stopping AP, etc.)

Therefore, the semantics of this flag don't make sense - you cannot
change the MAC address in a "live" way while there's a connection, and
at least internally you need not stop the NIC to change it. Since
ethernet has no concept of a "connection" in the same way, things are
different there.

Not sure how to really solve this - perhaps a wireless-specific way of
changing the MAC address could be added, though that's quite ugly, or we
might be able to permit changing the MAC address while not active in any
way (connected, scanning etc.) by removing from/re-adding to the driver
at least as far as mac80211 is concerned.

johannes

Re: [RFC 1/1] net: move IFF_LIVE_ADDR_CHANGE to public flag

[James Prestwood]

Hi Johannes,

On Tue, 2022-08-09 at 21:04 +0200, Johannes Berg wrote:
> On Thu, 2022-08-04 at 12:49 -0700, James Prestwood wrote:
> > > > 
> > > > The semantics in wireless are also a little stretched because
> > > > normally
> > > > if the flag is not set the netdev will _refuse_ (-EBUSY) to
> > > > change
> > > > the
> > > > address while running, not do some crazy fw reset.
> > > 
> > > Sorry if I wasn't clear, but its not nl80211 doing the fw reset
> > > automatically. The wireless subsystem actually completely disallows
> > > a
> > > MAC change if the device is running, this flag isn't even checked.
> > > This
> > > means userspace has to bring the device down itself, then change
> > > the
> > > MAC.
> > > 
> > > I plan on also modifying mac80211 to first check this flag and
> > > allow
> > > a
> > > live MAC change if possible. But ultimately userspace still needs
> > > to
> > > be
> > > aware of the support.
> > > 
> 
> I'm not sure this is the right approach.
> 
> For the stated purpose (not powering down the NIC), with most mac80211
> drivers the following would work:
> 
>  - add a new virtual interface of any supported type, and bring it up
>  - bring down the other interface, change MAC address, bring it up
> again
>  - remove the interface added in step 1
> 
> though obviously that's not a good way to do it!
> 
> But internally in mac80211, there's a distinction between
> 
>  ->stop() to turn off the NIC, and
>  ->remove_interface() to remove the interface.
> 
> Changing the MAC address should always be possible when the interface
> doesn't exist in the driver (remove_interface), but without stop()ing
> the NIC.
> 
> However, obviously remove_interface() implies that you break the
> connection first, and obviously you cannot change the MAC address
> without breaking the connection (stopping AP, etc.)

> Therefore, the semantics of this flag don't make sense - you cannot
> change the MAC address in a "live" way while there's a connection, and
> at least internally you need not stop the NIC to change it. Since
> ethernet has no concept of a "connection" in the same way, things are
> different there.

There isn't a need for changing the MAC when connected/scanning, as
this doesn't make much sense. I guess "live" can be interpreted
differently, but my interpretation is simply changing the MAC when the
device isn't powered off. IFF_POWERED_ADDR_CHANGE, maybe, is better
suited.

> 
> Not sure how to really solve this - perhaps a wireless-specific way of
> changing the MAC address could be added, though that's quite ugly, or
> we
> might be able to permit changing the MAC address while not active in
> any
> way (connected, scanning etc.) by removing from/re-adding to the driver
> at least as far as mac80211 is concerned.

Ok, so this is how I originally did it in those old patches:

https://lore.kernel.org/linux-wireless/20190913195908.7871-2-prestwoj@gmail.com/

i.e. remove_interface, change the mac, add_interface. 

But before I revive those I want to make sure a flag can be advertised
to userspace e.g. NL80211_EXT_FEATURE_LIVE_ADDRESS_CHANGE. (or
POWERED). Since this was the reason the patches got dropped in the
first place.

> 
> johannes

Re: [RFC 1/1] net: move IFF_LIVE_ADDR_CHANGE to public flag

[Johannes Berg]

On Wed, 2022-08-10 at 09:26 -0700, James Prestwood wrote:
> 
> Ok, so this is how I originally did it in those old patches:
> 
> https://lore.kernel.org/linux-wireless/20190913195908.7871-2-prestwoj@gmail.com/
> 
> i.e. remove_interface, change the mac, add_interface. 

Hah, I didn't even remember that ... sorry.

> But before I revive those I want to make sure a flag can be advertised
> to userspace e.g. NL80211_EXT_FEATURE_LIVE_ADDRESS_CHANGE. (or
> POWERED). Since this was the reason the patches got dropped in the
> first place.
> 

Well it seems that my objection then was basically that you have a
feature flag in nl80211, but it affects an RT netlink operation ...
which is a bit strange.

Thinking about that now, maybe it's not _that_ bad? Especially given
that "live" can mean different things (as discussed here), and for
wireless that doesn't necessarily mean IFF_UP, but rather something like
"IFF_UP + not active".

Jakub, what do you think?


(I'll also note you also have error handling problems in your patch, so
if/when you revive, please take a look at handling errors from add and
remove interface. Also indentation, and a comment on station/p2p-client
might be good, and the scanning check is wrong, can check scan_sdata
regardless of the iftype.)

johannes

Re: [RFC 1/1] net: move IFF_LIVE_ADDR_CHANGE to public flag

[Jakub Kicinski]

On Wed, 10 Aug 2022 19:17:19 +0200 Johannes Berg wrote:
> Thinking about that now, maybe it's not _that_ bad? Especially given
> that "live" can mean different things (as discussed here), and for
> wireless that doesn't necessarily mean IFF_UP, but rather something like
> "IFF_UP + not active".
> 
> Jakub, what do you think?

Agreed, even tho the concept of a live address change seems generic 
the implications and definition of "live" are very area specific.
Let's handwave that nl80211 is a subordinate API of RT netlink :)

Re: [RFC 1/1] net: move IFF_LIVE_ADDR_CHANGE to public flag

[James Prestwood]

Hi Johannes,

On Wed, 2022-08-10 at 19:17 +0200, Johannes Berg wrote:
> On Wed, 2022-08-10 at 09:26 -0700, James Prestwood wrote:
> > 
> > Ok, so this is how I originally did it in those old patches:
> > 
> > https://lore.kernel.org/linux-wireless/20190913195908.7871-2-prestwoj@gmail.com/
> > 
> > i.e. remove_interface, change the mac, add_interface. 
> 
> Hah, I didn't even remember that ... sorry.

No worries, it was a long time ago.

> 
> > But before I revive those I want to make sure a flag can be
> > advertised
> > to userspace e.g. NL80211_EXT_FEATURE_LIVE_ADDRESS_CHANGE. (or
> > POWERED). Since this was the reason the patches got dropped in the
> > first place.
> > 
> 
> Well it seems that my objection then was basically that you have a
> feature flag in nl80211, but it affects an RT netlink operation ...
> which is a bit strange.
> 
> Thinking about that now, maybe it's not _that_ bad? Especially given
> that "live" can mean different things (as discussed here), and for
> wireless that doesn't necessarily mean IFF_UP, but rather something
> like
> "IFF_UP + not active".
> 
> Jakub, what do you think?
> 
> 
> (I'll also note you also have error handling problems in your patch,
> so
> if/when you revive, please take a look at handling errors from add
> and
> remove interface. Also indentation, and a comment on station/p2p-
> client
> might be good, and the scanning check is wrong, can check scan_sdata
> regardless of the iftype.)

Yep, I'll get that fixed up for v2.

Thanks,
James
> 
> johannes