On Thu, 4 Mar 2021 07:24:50 +0100 aitor <aitor_...@gnuinos.org> wrote:
> Hi tito, > > On 4/3/21 0:47, tito via Dng wrote: > > In my young years I used to tinker with linux distros on floppy > > disks and there still where eth0, eth1 and so on but no udev, > > so where did the names came from? > > They were assigned by the kernel, i think. > > Aitor. > > Exactly, therefore udev only can modify the kernel assigned names, How Linux assigns network interface names The default name for Ethernet interfaces is based upon how Linux initializes them during device discovery. As Linux finds the network devices it will start numbering them starting with 0 and increasing sequentially. Device discovery is dependent on the device driver load order, PCI bus topology and the device driver code. On RHEL4, the device driver load order is determined by the /etc/modprobe.conf file. Device drivers assigned lower interface numbers in that file are loaded first. On RHEL5 device drivers are loaded by thehotplug subsystem, i.e. by udev, in parallel and it affects the assignment of names. When Linux loads a single device driver it will initialize and find all devices supported by that single driver first. On SLES, device drivers are loaded based on the PCI bus topology as discovered by the kernel. The PCI bus topology is composed of buses, bridges and devices. PCI devices must be connected to a PCI bus. The PCI buses are connected by PCI bridges to either other buses or to the system. The topology of the system can be viewed as a tree. Using this analogy, the devices are leaves, the system is the trunk, buses are branches and bridges exist where branches meet each other or the trunk. Searching for PCI devices in a system is accomplished by "walking the tree". The method of walking the tree was modified in the 2.6 and later kernels, thus changing the order in which devices are found. And last, each device driver will search the PCI tree for all the devices it supports. Some drivers have a list of different devices it will support and search the tree for each device in the list. Other drivers will scan the tree and, for each device, see if it is in its list of supported devices. This will also change order of how devices are found and thus its interface name. Changes in system configuration will also result in a different enumeration order. If a new network card is inserted into a PCI slot, its new position could be between two previous network devices. This may result in the new card taking over the name of a previous card in the system. The root cause of NIC enumeration mismatches is that there is currently no industry standard to enable the OS to determine the physical labeling of Ethernet ports on the motherboard. _______________________________________________ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng