Date: Tue, 4 Jul 2006 19:56:14 +0200 (CEST) From: Harti Brandt <hartmut.brandt@dlr.de> To: Brooks Davis <brooks@one-eyed-alien.net> Cc: src-committers@FreeBSD.org, yar@comp.chem.msu.su, rwatson@FreeBSD.org, julian@elischer.org, freebsd-net@FreeBSD.org, "M. Warner Losh" <imp@bsdimp.com> Subject: Re: cvs commit: src/sys/net if_vlan.c Message-ID: <20060704195220.K74584@beagle.kn.op.dlr.de> In-Reply-To: <20060704174208.GA1734@odin.ac.hmc.edu> References: <44A40C25.904@elischer.org> <20060630115749.G3964@fledge.watson.org> <20060703202803.GA22556@odin.ac.hmc.edu> <20060704.102539.-494099438.imp@bsdimp.com> <20060704174208.GA1734@odin.ac.hmc.edu>
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On Tue, 4 Jul 2006, Brooks Davis wrote: BD>On Tue, Jul 04, 2006 at 10:25:39AM -0600, M. Warner Losh wrote: BD>> In message: <20060703202803.GA22556@odin.ac.hmc.edu> BD>> Brooks Davis <brooks@one-eyed-alien.net> writes: BD>> : and act as though the interface is not there. We could then consider BD>> : either holding the interface for a configurable or computed length BD>> : of time or adding some sort of refcounting (probably impractical). BD>> BD>> Refcounting would be good for the 'macro' things (coming and going) BD>> that are infrequent, but we might have mulitple people doing. You are BD>> right it likely is too inefficient to do with mbugs. One other option BD>> might be to have a configurable time after the last time that it was BD>> accessed via the 'safe' routines that were setup. This way we'd tie BD>> the removal of the interface to a period of time after it was last BD>> used, rather than after it was removed. I don't know if such a BD>> difference would matter much in practice. BD> BD>We might get some mielage out of last used, but then we'd have to keep BD>that timestamp updated. For normal applications, once we've torn down BD>the sockets and drained their queues, I believe we should not have to BD>wait more than a few seconds unless dummynet or some other mechanism BD>that queues mbufs for a significant period of time is enabled. If BD>dummynet is enabled we need to wait a bit longer, but it isn't outside BD>the relm of possibility for dummynet to be modified to tell us how long BD>it will be until the last mbuf it currenly holds will be released. In BD>practice, 121 seconds is probably a good default number since a 60 BD>second max RTT is assumed in TCP and thus delays longer than that BD>would break everything anyway. BD> BD>> The only other 'issue' that I see with this approach is if I remove a BD>> card, and then insert it again before the timeout happens. Does that BD>> card get a new interface name? And would people care or not... BD> BD>The name is unregistered with the call to if_detach because if_detach BD>removes the interface from the ifnet list. My guess is that BD>we'll either zero the name field or set to something like _zombie. The BD>unit will remain reserved until later. We'll need to add an SNMP index BD>mananaged in userland to satisfy come current if_index consumers. bsnmp does this anyway because of the rules for ifIndex. It has some heuristic to guess whether an interface is a physical one or not and if it is, it uses the same index again. The downside of this is that the interface index you see via SNMP has nothing to do with the interface index you see in the system and this does not work accross reboots and daemon restarts as required by the RFC. harti
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