Re: Dummy Network Interface

From: Michael W. Oliver (michael_at_gargantuan.com)
Date: 01/15/04

  • Next message: David Gilbert: "Re: kern/61215: off-by-one error likely in ip_fragment()" 
    Date: Thu, 15 Jan 2004 15:47:34 -0500
To: Robert Watson <rwatson@freebsd.org>

    On Thu, Jan 15, 2004 at 03:07:20PM -0500, Robert Watson wrote:
    >
    > On Thu, 15 Jan 2004, Vlad Galu wrote:
    >
    > > |On Tue, 13 Jan 2004 ms419@freezone.co.uk wrote:
    > > |
    > > |> How does one create a dummy network interface in FreeBSD?
    > > |
    > > |Dummy in what sense? An interface where the packets are simply
    > > |dropped? if_tap and if_tun both provide pseudo-device in /dev that a
    > > |userspace process can attach to in order to emulate a network interface
    > > |(used by VMWare, ppp, various tunneling bits, ...) In the absense of a
    > > |process sitting on the device, they simply drop the packets. Although
    > > |they may get garbage-collected if unused on -CURRENT... You can also
    > > |use netgraph to bring pseudo-interfaces, perhaps without anywhere for
    > > |packets to go.
    > > |
    > > |And, I suppose, create in what sense? Are you looking at this from a
    > > |developer perspective, or you just need one from a user perspective.
    > > |If writing a device driver (and hence needing a starting point), if_tap
    > > |and if_tun are fairly decent models for a pseudo-interface.
    > >
    > > I think he could use the discard interface smoothly. On Linux
    > > (from which the dummy interface notion is taken from) it is simply used
    > > for testing purposes, as in routing, or perhaps socket programming. I
    > > personally have used it for a while, but then I used interface aliasing,
    > > which became a habit.
    >
    > Does the discard interface in Linux "act like" another type of interface,
    > such as point-to-point, ethernet, etc?

    I believe that he was referring to the discard interface in FreeBSD. I
    don't know about Linux at all, but I have used the discard interface in
    a FreeBSD router much like a Null interface in a cisco router.

    pseudo-device disc

    man 4 disc 

    -- 
Mike
perl -e 'print unpack("u","88V]N=&%C=\"!I;F9O(&EN(&AE861E<G,*");'

  • Next message: David Gilbert: "Re: kern/61215: off-by-one error likely in ip_fragment()"

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