Mapping network device names to their kernel modules?

From: JoSH Lehan (krellan_at_gmail.com)
Date: 10/26/04

  • Next message: John Fusco: "Re: LILO question" 
    Date: 25 Oct 2004 16:19:30 -0700

    Is there a reliable way to map network device names (for instance
    eth0, eth1, eth2, etc.) to the kernel modules responsible for loading
    them?

    There are user configuration files that can be set to manually keep
    track of this information, such as "alias eth0 3c59x" in
    /etc/modules.conf, but this must be manually maintained by the user
    (or configuration utility) and is subject to breakage when the user
    adds/removes various network cards.

    What about at system installation time -- how would an installer
    program know which kernel modules are responsible for creating various
    network device names?

    My guess is that a system installer will just attempt to load every
    network device module in order, and query the table of device names
    (/proc/net/dev) after *each* module has finished attempting to load.
    The installer will watch for new devices appearing in this table, and
    associate each new device with the module that was most recently
    loaded. That way, a table will be built up over time, and the
    information can be written out to /etc/modules.conf in the usual way.

    The problem with this is that it breaks whenever the user adds or
    removes (or even rearranges!) network cards after system installation.
     If a new eth3 device were to suddenly appear in the system, for
    instance, it would have no information. The user would need to know
    which kernel module was responsible for recognizing it, and
    automatically add it to the table in /etc/modules.conf so that the
    kernel would load it upon demand. It could get very confusing if the
    addition of the card changed the loading order of the modules, so that
    eth0/eth1/eth2 were now pointing to different cards! This could even
    be a security issue, for instance if a firewall were to become
    misconfigured to allow packets through the wrong interfaces.

    Are there any files in the /proc directory that contains this
    information? /proc/modules has the names of modules that are
    currently loaded and their usage count (e.g. the number of cards that
    were recognized by each Ethernet device driver module). /proc/net/dev
    has a list of user-visible network device names (eth0, eth1, and so
    on). I couldn't find a file that relates these device names to their
    relevant kernel modules. It would be wonderful if there was a way of
    gathering this information and putting it all together.

    Does anybody also see a useful need for this feature? Has such a
    thing been already implemented, and if so, where?

    Thanks!

    Josh
    krellan -at- gmail -dot- com

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