Willy Tarreau wrote: > On Mon, Nov 12, 2007 at 03:19:23PM -0800, David Miller wrote: >> From: Willy Tarreau <[EMAIL PROTECTED]> >> Date: Tue, 13 Nov 2007 00:15:16 +0100 >> >>> I can say that sometimes you'd like to be aware that one of your >>> VLANs is wrong and you'd simply like to sniff the wire to guess the >>> correct tag. And on production, you simply cannot remove other >>> VLANs, otherwise you disrupt the service. >> If you were plugged into the wrong physical switch, how might >> you debug that problem in production? :-) > > tcpdump on an unfiltered RJ45 tells you a lot of things. Some switches > for instance send keepalive packets (ether proto 9000) with their own > MAC as source+dest, others send CDP packets, etc... I've very rarely > stayed plugged to the wrong switch for too long before discovering it. > But that requires the ability to sniff. > >> Really, it's the same issue, just virtualized, as in the name >> for the feature, VLAN. > > No, it's not the same, because as soon as you pass through a switch > which is not configured for VLANs, it does not make any distinction, > and the same DMAC is considered on a single port whatever the VLAN. > This is not true with multiple switches. Also, sometimes, being able > to see that your port gets flooded with traffic for a VLAN on which > you're not configured helps you understand why you cannot fill the > port. > > I'd like that we can use the hardware correctly without having to > buy TAPs. It reminds me the discussions about TOE. You claim > yourself that TOE is bad in part because you have little if any > control on the bugs on the TCP stack on the chip. This is the same > here. If I know that the chip does not send me what it receives > when configured in promiscuous mode, I can I swear it never received > the missing packet ? There's always a doubt. Maybe sometimes the > filter is buggy, maybe it only passes tags when the remaining bits > are all zero, etc... Promiscuous mode generally means that you're > the closest possible to the wire. We already do not receive pause > frames and sometimes that's annoying. But having no control over > what we want to see is frustrating. > > At least, being able to disable the feature at module load time > would be acceptable. Many people who often need to sniff on decent > machines would always keep it disabled.
I really do not want to add another module parameter to the driver for this. It seems bogus as well: if we can agree on one sane choice it's much better, and if we don't then we should use ethtool to provide a uniform way of implementing this for all drivers sanely. Auke - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
