Once upon a time, Garry Dolley <gdolley@xxxxxxxxxxxxxxx> said: > On Wed, Apr 15, 2009 at 07:53:04PM -0500, Chris Adams wrote: > > If I run tcpdump in the VM and ping from the VM, I see: > > > > 19:02:04.443160 00:04:61:4a:ee:27 > Broadcast, ethertype ARP (0x0806), length 42: arp who-has 172.24.54.14 tell 172.24.54.207 > > > > > > I swear I saw tagged packets within the VM earlier. :-( > > Are you running tcpdump in the VM on eth2? Yes. > If so, you won't see tagged packets on eth2. Huh, I didn't realize that. I set up a different test, and you are right (confusing, but correct). However, if I (in the host) tcpdump tap2 or br2, the packets are untagged there as well. So, either: - they are not being tagged in the VM - qemu-kvm is stripping the tag - the tap interface is stripping the tag > > Okay, if I watch eth2 and eth2.20 with the same tcpdump command as > > above, I see incoming packets correctly. On eth2, I see the tag, and > > then they show up on eth2.20 without the tag. It appears to only be a > > problem with outbound packets not getting tagged (I see the same > > untagged packets in the host with a tcpdump on tap2). > > Are you sure you see the tag on eth2? I woulda killed to see the > tag on the physical int when doing my setup a few weeks ago. I only see it on traffic from the LAN, but yes, I do see it there. > I wonder if VLAN hardware acceleration has anything to do with it. Is that something that can be turned on/off within the VM? > Can you show a tcpdump on the host when pinging from inside the VM? # tcpdump -s0 -e -n -i tap2 20:55:30.927645 00:04:61:4a:ee:27 > Broadcast, ethertype ARP (0x0806), length 42: arp who-has 172.24.54.13 tell 172.24.54.207 # tcpdump -s0 -e -n -i br2 20:56:11.474010 00:04:61:4a:ee:27 > Broadcast, ethertype ARP (0x0806), length 42: arp who-has 172.24.54.13 tell 172.24.54.207 Aha! Apparently, there's a fourth option to the above possible sources of the problem: - the 8139 driver (either in the VM kernel or qemu-kvm) is stripping the tag I switched qemu-kvm to emulate an Intel i82557b (using e100 driver in the VM), and it all works! Thanks for letting me know it _should_ work and helping me think through it. -- Chris Adams <cmadams@xxxxxxxxxx> Systems and Network Administrator - HiWAAY Internet Services I don't speak for anybody but myself - that's enough trouble. -- To unsubscribe from this list: send the line "unsubscribe linux-net" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
