Hi Paolo: Apparently I was unclear in my last email. I was not trying to claim that "uml_switch -hub" was delivering promiscuously when "ifconfig promisc" was not set, but rather that it was (correctly) delivering non-promiscuously -- meaning I didn't have to trick my protocol software into filtering out the unwanted packets using the "ifconfig promisc" approach that was required with "ethX=mcast".
In short, I think everything is now working as it should. But if I see anything else that looks strange I'll be sure to mention it! Regards, Al Stephens Wind River > -----Original Message----- > From: Paolo Giarrusso [mailto:[EMAIL PROTECTED] > Sent: Tuesday, August 01, 2006 12:56 PM > To: Stephens, Allan; user-mode-linux-user@lists.sourceforge.net > Subject: RE: [uml-user] Promiscuous mode interface bug? > > "Stephens, Allan" <[EMAIL PROTECTED]> ha scritto: > > > Hi Paolo: > > > > I tried configuring the Ethernet interfaces as > "promiscuous" and this > > did indeed provide a workaround for the issue I raised. The root > > cause of my problems seems to have been a lack of > understanding on my > > part as to what I was really asking UML to do for me; your > explanation > > has helped clear things up significantly. It appears that > I was using > > interfaces of the form "ethX=mcast" expecting them to > behave like ones > > of the form "ethX=daemon" used with "uml_switch -hub". > > I.e. when you use "uml_switch -hub" even without "ifconfig promisc" > all packets arrive as if the interface were in promiscuos mode? > Compliments, if this is true you have found a bug! I'll > verify this ASAP - it could be born from the fact that > uml_switch is normally a switch so maybe the code coping with > it thinks there's no need to filter MAC destination address. > I'll verify this (if I don't forget). > > > I've now > > reconfigured things to use the latter type of interface, and things > > are working as I expected. > > > > Thanks so much for your help! > > > > Regards, > > Al Stephens > > Wind River > > > > > -----Original Message----- > > > From: Blaisorblade [mailto:[EMAIL PROTECTED] > > > Sent: Saturday, July 29, 2006 4:20 AM > > > To: user-mode-linux-user@lists.sourceforge.net > > > Cc: Stephens, Allan > > > Subject: Re: [uml-user] Promiscuous mode interface bug? > > > > > > On Wednesday 26 July 2006 16:34, Stephens, Allan wrote: > > > > Hi there: > > > > > > > > I've been running UML using Linux 2.6.17 (guest) and 2.6.12 > > > (host) and > > > > configured a guest with a pair of Ethernet multicast interfaces > > as > > > > shown below. (Note that I didn't configure any IP > > > addresses, as I'm > > > > not trying to use them to carry IP traffic.) > > > > > > > > uml_mconsole <session> config eth1=mcast,00:00:00:00:01:01 > > > > uml_mconsole <session> config eth2=mcast,00:00:00:00:02:02 > > > > > > > > When a second guest transmitted traffic using a destination > > > address of > > > > 00:00:00:00:01:01, the message showed up on both interfaces (as > > > > > > expected). However, the kernel protocol handled incoming > > > messages did > > > > not recognize and discard the unwanted copy that showed up at > > "eth2" > > > > because the associated "struct net_device" object did not have > > the > > > > "promiscuity" field set to indicate that the interface > > > might receive > > > > traffic other than its own. > > > > > > That's a slightly wrong interpretation of the flag (it actually > > > means that the interface should accept others' > > > packets; whether it may receive them or not is indicated by the > > > BROADCAST/POINTTOPOINT flag in ifconfig output). > > > > > > It's also a slightly complex way to check it: > > > > > > ifconfig eth2 |grep PROMISC would be simpler. > > > and ifconfig eth2 promisc would enable it. > > > > > > > It seems to me that any UML interface configured to use > > multicast > > > > should cause the promiscuity field of the associated > > > net_device to be > > > > set -- but maybe I'm missing something here. Is the scenario I > > > > > > encountered really a bug? > > > > > > No, it's a feature; I understand your point of view and > what you say > > > makes sense from that, but you're looking from an unusual > point of > > > view (and you went very fast up the knowledge hill so it's not a > > > problem, you must be a smart guy). > > > > > > You're more or less claiming that if you have a hub-based > Ethernet > > > LAN (multicast networking has the same properties, it's a > broadcast > > > LAN implemented over multicast IP) all PCs should auto-configure > > > their interfaces to work in promiscuos > > mode. > > > > > > That's wrong, as promiscuos mode only makes sense in hub-based > > > networks and reduces overhead. > > > > > > You can still configure your interface to work in > promiscuos mode as > > > said above. > > > > > > All this said, if when trying what I suggested you see unexpected > > > behaviour, it _may_ be a bug (especially in UML network support > > > and/or UML multicast transport). > > > -- > > > Inform me of my mistakes, so I can keep imitating Homer Simpson's > > > "Doh!". > > > Paolo Giarrusso, aka Blaisorblade > > > http://www.user-mode-linux.org/~blaisorblade > > > Chiacchiera con i tuoi amici in tempo reale! > > > http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com > > > > > > > > > > > Chiacchiera con i tuoi amici in tempo reale! > http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com > ------------------------------------------------------------------------- Take Surveys. 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