Re: interface renaming of an running interface

From: Harti Brandt (novo_at_cs.tu-berlin.de)
Date: 04/08/04

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    Date: Thu, 8 Apr 2004 14:13:38 +0200 (CEST)
To: Robert Watson <rwatson@FreeBSD.ORG>

    On Wed, 7 Apr 2004, Robert Watson wrote:

    > On Wed, 7 Apr 2004, Harti Brandt wrote:
    >
    > > I'm currently trying to teach bsnmp to correctly handle interface
    > > renaming. One problem that I encounter is that a process listening on
    > > the routing socket sees an interface departure and an interface arrival
    > > message. This cause interfaces that run stateful protocols like SNMP on
    > > ATM interfaces to drop all connections which isn't really all that nice.
    > > The SNMP daemon would also loose all interface state and would report
    > > the renamed interface as a new interface with a new ifindex. This
    > > directly violates the IF-MIB RFC, because the daemon is required to
    > > understand that this is the same interface (the ifindex doesn't really
    > > help here, because unloading/loading the driver gives the same
    > > behaviour). I would like to do one of the following two things:
    > >
    > > 1) disallow renaming an interface while it is up, or 2) instead of
    > > emiting a departure/arrival pair of routing messages, generate a rename
    > > message.
    > >
    > > Additionally I would like to create new sysctls:
    > >
    > > net.link.generic.ifdata.<ifindex>.dname
    > > net.link.generic.ifdata.<ifindex>.dunit
    > >
    > > to access the driver's name of an interface.
    > >
    > > Comments?
    >
    > I was actually worried about this issue also -- FWIW, the issue already
    > exists even without generic interface renaming because some interfaces
    > (specifically, if_sl) already support renumbering on demand using ioctl().
    > I agree that what we need is a rename event -- the only real question is
    > whether and how to handle compatibility for applications that don't know
    > what to do with it. Presumably the only real question is for things like
    > SNMP and routing daemons, although we've also talked about event
    > monitoring for interfaces using devctl, in which case devd would need to
    > learn about the "rename" primitive as well.

    I don't know how to deal with devctl, but for the routing socket I'd
    introduce a new IFAN_RENAME for the ifan_what field of the RTM_IFANNOUNCE
    routing message. The interface name in the message would be the new one,
    so by tracking these message the daemon will understand what happens.
    I'll prepare a patch and try to get some testing on net@.

    harti
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