Prior to the commit below, dsa_master_ndo_setup() used to avoid overriding .ndo_get_phys_port_name() unless the callback was empty.
https://elixir.bootlin.com/linux/v5.7.7/source/net/dsa/master.c#L269 Now, it overrides it unconditionally. This matters for boards where DSA switches are hanging off of other DSA switches, or switchdev interfaces. Say a user has these udev rules for the top-level switch: ACTION=="add", SUBSYSTEM=="net", KERNELS=="0000:00:00.5", DRIVERS=="mscc_felix", ATTR{phys_port_name}=="p0", NAME="swp0" ACTION=="add", SUBSYSTEM=="net", KERNELS=="0000:00:00.5", DRIVERS=="mscc_felix", ATTR{phys_port_name}=="p1", NAME="swp1" ACTION=="add", SUBSYSTEM=="net", KERNELS=="0000:00:00.5", DRIVERS=="mscc_felix", ATTR{phys_port_name}=="p2", NAME="swp2" ACTION=="add", SUBSYSTEM=="net", KERNELS=="0000:00:00.5", DRIVERS=="mscc_felix", ATTR{phys_port_name}=="p3", NAME="swp3" ACTION=="add", SUBSYSTEM=="net", KERNELS=="0000:00:00.5", DRIVERS=="mscc_felix", ATTR{phys_port_name}=="p4", NAME="swp4" ACTION=="add", SUBSYSTEM=="net", KERNELS=="0000:00:00.5", DRIVERS=="mscc_felix", ATTR{phys_port_name}=="p5", NAME="swp5" If the DSA switches below start randomly overriding ndo_get_phys_port_name with their own CPU port, bad things can happen. Not only may the CPU port number be not unique among different downstream DSA switches, but one of the upstream switchdev interfaces may also happen to have a port with the same number. So, we may even end up in a situation where all interfaces of the top-level switch end up having a phys_port_name attribute of "p0". Clearly not ok if the purpose of the udev rules is to assign unique names. Fix this by restoring the old behavior, which did not overlay this operation on top of the DSA master logic, if there was one in place already. Fixes: 3369afba1e46 ("net: Call into DSA netdevice_ops wrappers") Signed-off-by: Vladimir Oltean <olte...@gmail.com> --- This is brain-dead, please consider killing this and retrieving the CPU port number from "devlink port"... pci/0000:00:00.5/0: type eth netdev swp0 flavour physical port 0 pci/0000:00:00.5/2: type eth netdev swp2 flavour physical port 2 pci/0000:00:00.5/4: type notset flavour cpu port 4 spi/spi2.0/0: type eth netdev sw0p0 flavour physical port 0 spi/spi2.0/1: type eth netdev sw0p1 flavour physical port 1 spi/spi2.0/2: type eth netdev sw0p2 flavour physical port 2 spi/spi2.0/4: type notset flavour cpu port 4 spi/spi2.1/0: type eth netdev sw1p0 flavour physical port 0 spi/spi2.1/1: type eth netdev sw1p1 flavour physical port 1 spi/spi2.1/2: type eth netdev sw1p2 flavour physical port 2 spi/spi2.1/3: type eth netdev sw1p3 flavour physical port 3 spi/spi2.1/4: type notset flavour cpu port 4 net/core/dev.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index 19f1abc26fcd..60778bd8c3b1 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -8603,15 +8603,20 @@ int dev_get_phys_port_name(struct net_device *dev, const struct net_device_ops *ops = dev->netdev_ops; int err; - err = dsa_ndo_get_phys_port_name(dev, name, len); - if (err == 0 || err != -EOPNOTSUPP) - return err; - if (ops->ndo_get_phys_port_name) { err = ops->ndo_get_phys_port_name(dev, name, len); if (err != -EOPNOTSUPP) return err; + } else { + /* DSA may override this operation, but only if the master + * isn't a switchdev or another DSA, in that case it breaks + * their port numbering. + */ + err = dsa_ndo_get_phys_port_name(dev, name, len); + if (err == 0 || err != -EOPNOTSUPP) + return err; } + return devlink_compat_phys_port_name_get(dev, name, len); } EXPORT_SYMBOL(dev_get_phys_port_name); -- 2.25.1
