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    SubjectPreferred method to export info to userspace
    Hello everybody:

    I am writing a module for analyzing packets in kernel space. In SMP
    systems, the module creates as many kernel threads as CPUs, each bound
    to a processor. When a new packet arrives, if it comes from the
    capture interface, it is enqueued in a global skb queue (this is done
    from netif_receive_skb()). The kernel threads will thereafter get the
    packets from that queue and analyze them.

    To test the module, as well as to gain some flexibility in its working
    mode, the module has to communicate with user space. Configuration
    options are:

    * Turn ON/OFF the packet capturing, as well as change the way it captures them
    [I do this with a "flags" variable, which is changed from userspace
    via ioctl]
    * Change some configuration parameters: maximum length of the skb queue,
    capture interface i.e. eth0
    [I do this via read-write /proc files]
    * Export statistics to userspace
    [I do this via a read-only /proc file]

    This all works, but I would like to code it more ellegantly. I've been
    reading some kernel code, and people use to do this kind of things in
    different ways. For example, in the packet generator module (pktgen),
    it uses some /proc files for all the configuration, for example, to
    set/clear a flag:

    set a flag: echo "flag IPDST_RND" > /proc/net/pktgen/eth1
    clear a flag: echo "flag !IPDST_RND" > /proc/net/pktgen/eth1

    In contrast, in dev_ioctl() (net/core/dev.c), flags are set or cleared
    via two ioctl commands (set: SIOCSIFFLAGS, get: SIOCGIFFLAGS).

    If this weren't enough, it seems that there is a new filesystem for
    exporting information to userspace: sysfs. This is similar to /proc
    but with more constraints.
    I mean, each file (attribute) should contain just one value. In my
    module I export quite a lot information just calling

    $ cat /proc/ksensor/stats:
    iface: eth1
    captured: 18233
    processed: 3334
    dropped: 15003
    errors: 34
    cur_queue_len: 56
    max_queue_len: 1024

    So, I would have to create as many files as values I want to export in
    sysfs? that would be quite a lot files, no?

    And the last question, how should I configure the "flags" variable I
    told before? Currently, I have three flags:

    KSF_UP: whether the capture device is running or not
    KSF_CONCTRL: whether it is used congestion control for incoming packets
    KSF_TRANSP: whether it is made a copy of the packet so that the kernel
    can continue processing the packet later (if not, the packet is
    captured, analyzed and dropped).

    Possible options are:

    * I do this with a ioctl command for setting the flags and another one
    for getting them.
    * Another possibility would be to create as many files as flags in
    /proc/ksensor and echo 1 to turn it on or echo 0 to turn it off.
    * Another more possibility would be to use a command as I told before
    what is done with pktgen module.
    * And the last one, would be to do this in sysfs.

    Which option do you think is better? I would thank any replies, or
    ideas to these questions.

    Aritz Bastida
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      Last update: 2005-12-08 15:30    [W:0.041 / U:43.488 seconds]
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