Re: what is the story on if_index allocation ?

From: Bill Fumerola (billf_at_FreeBSD.org)
Date: 04/20/04

  • Next message: Luigi Rizzo: "Re: what is the story on if_index allocation ?" 
    Date: Mon, 19 Apr 2004 15:43:30 -0700
To: Julian Elischer <julian@elischer.org>

    On Mon, Apr 19, 2004 at 12:28:23PM -0700, Julian Elischer wrote:
    > It's completely un-needed except that some standards want to access
    > interfaces by index for statitics purposes.

    they're "un-needed" in much the same way that statically assigning disk
    numbers is "un-needed". sure, the disks don't light on fire without it,
    but some consistancy and persistance does make things nice.

    for comparison: vendor C has a default-to-off option for this (''snmp
    ifindex persist'') which pre-allocates numbers loosely based on max_modules
    * max_ports_in_modules and dumps this mapping into the filesystem. vendor
    J allocates dynamically and won't reuse ifIndex numbers over the life
    of a router.

    a way of keeping indexes consistant for a given named interface (even
    across creation/destruction via cloning, kld, etc) is most certainly a
    desirable feature. the more persistant this can be made (life of the
    module all the way up to life of device) the better.

    i disagree that this logic belongs outside the kernel in the snmp agent.
    an inconsistant if_index makes it difficult and error prone for using
    the index in multiple utilities whose data may be combined/joined/scaled
    with information from the snmp agent's IF-MIB/ifXTable tables. 

    -- 
- bill fumerola / fumerola@yahoo-inc.com / billf@FreeBSD.org
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  • Next message: Luigi Rizzo: "Re: what is the story on if_index allocation ?"