Re: [libvirt-users] connecting host and guest vm using a dummy nic

Greetings Laine, > Sent: Monday, April 30, 2018 at 8:31 PM > From: "Laine Stump" <laine(a)redhat.com&gt; > To: libvirt-users(a)redhat.com > Cc: daggs <daggs(a)gmx.com&gt; > Subject: Re: [libvirt-users] connecting host and guest vm using a dummy nic > > On 04/27/2018 06:39 PM, daggs wrote: >> Greetings all, >> >> I have a host machine that runs a router within a vm. >> I want to allow a connection between the host and the guest so the host can connect to the lan provided by the router vm. >> I've created a dummy interface with these commands: >> $ ip link add ens99-dummy type dummy >> $ ip link set ens99-dummy address 52:54:00:1f:d0:ff >> >> this resulted with this output: >> $ ifconfig ens99-dummy >> ens99-dummy Link encap:Ethernet HWaddr 52:54:00:1F:D0:FF >> inet6 addr: fe80::84b5:24ff:fe62:c16d/64 Scope:Link >> UP BROADCAST RUNNING NOARP MTU:1500 Metric:1 >> RX packets:0 errors:0 dropped:0 overruns:0 frame:0 >> TX packets:899 errors:0 dropped:0 overruns:0 carrier:0 >> collisions:0 txqueuelen:1000 >> RX bytes:0 (0.0 B) TX bytes:321727 (314.1 KiB) >> >> >> in my libvirt's xml file I have this entry: >> <interface type='direct'> >> <mac address='52:54:00:0c:cb:3e'/> >> <source dev='ens99-dummy' mode='private'/> >> <target dev='macvtap0'/> >> <model type='e1000'/> >> <alias name='net0'/> >> <address type='pci' domain='0x0000' bus='0x02' slot='0x01' function='0x0'/> >> </interface> > > MY first question would be "Why are you using macvtap?" This > unnecessarily complicates the plumbing, leading to more potential places > where it could fail. misconfiguration, question is, what should be the exact config for this. > > The 2nd question is - Have you looked at the dhcp server running on the > guest to verify that it is indeed listening for DHCP requests on the > guest-side interface associated with the macvtap interface, and that it > is receiving those requests and sending a reply? will test it. as said before, I'm not sure what should be the proper config in libvirt. > >> >> after the vm is up, I see the adapter in the vm and the host has one more entry: >> $ ifconfig macvtap0 >> macvtap0 Link encap:Ethernet HWaddr 52:54:00:0C:CB:3E >> inet6 addr: fe80::5054:ff:fe0c:cb3e/64 Scope:Link >> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 >> RX packets:0 errors:0 dropped:0 overruns:0 frame:0 >> TX packets:889 errors:0 dropped:0 overruns:0 carrier:0 >> collisions:0 txqueuelen:500 >> RX bytes:0 (0.0 B) TX bytes:320523 (313.0 KiB) >> >> but when I try to request ip via dhcp from both macvtap0 and ens99-dummy I don't get any. >> any idea why? > > Definitely you wouldn't be able to use the macvtap0 device, so if > anything you would want to be using ens99-dummy, but I'm not even > certain *that* would work, as I've never tried it. so use ens99-dummy directly?

> > You've provided no visibility into the configuration of the guest OS in > your virtual machine, but in general if you want a simple connection > between the host and guest that has *no other connections*, you can do > this with a bare tap device:

> > <interface type='ethernet'> > <model type='e1000'/> > </interface> > > This will show up as a single device on the host and a single device in > the guest, not connected to a bridge or a macvtap device or anything, > and will not need any other "ip link blah blah" type setup on the host. > Simplifying your setup in this manner may make it easier to find the > source of your problem. > ok, here is the entire xml file:

<domain type='kvm'> <name>router</name> <uuid>ed8eabe2-ced3-4224-aa12-60fb31dd3fd4</uuid> <memory unit='KiB'>1048576</memory> <currentMemory unit='KiB'>1048576</currentMemory> <vcpu placement='static'>2</vcpu> <os> <type arch='x86_64' machine='pc-q35-2.8'>hvm</type> <boot dev='hd'/> </os> <features> <acpi/> <apic/> </features> <cpu mode='host-passthrough'/> <clock offset='utc'> <timer name='rtc' tickpolicy='catchup'/> <timer name='pit' tickpolicy='delay'/> <timer name='hpet' present='no'/> </clock> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> <pm> <suspend-to-mem enabled='no'/> <suspend-to-disk enabled='no'/> </pm> <devices> <emulator>/usr/bin/kvm</emulator> <disk type='file' device='disk'> <driver name='qemu' type='raw'/> <source file='/home/router/lede-x86-64-combined-ext4.img'/> <target dev='vda' bus='virtio'/> <address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x0'/> </disk> <controller type='usb' index='0' model='ich9-ehci1'> <address type='pci' domain='0x0000' bus='0x00' slot='0x1d' function='0x7'/> </controller> <controller type='usb' index='0' model='ich9-uhci1'> <master startport='0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x1d' function='0x0' multifunction='on'/> </controller> <controller type='usb' index='0' model='ich9-uhci2'> <master startport='2'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x1d' function='0x1'/> </controller> <controller type='usb' index='0' model='ich9-uhci3'> <master startport='4'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x1d' function='0x2'/> </controller> <controller type='sata' index='0'> <address type='pci' domain='0x0000' bus='0x00' slot='0x1f' function='0x2'/> </controller> <controller type='pci' index='0' model='pcie-root'/> <controller type='pci' index='1' model='dmi-to-pci-bridge'> <model name='i82801b11-bridge'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x1e' function='0x0'/> </controller> <controller type='pci' index='2' model='pci-bridge'> <model name='pci-bridge'/> <target chassisNr='2'/> <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/> </controller> <controller type='pci' index='3' model='pcie-root-port'> <model name='ioh3420'/> <target chassis='3' port='0x8'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0' multifunction='on'/> </controller> <controller type='pci' index='4' model='pcie-root-port'> <model name='ioh3420'/> <target chassis='4' port='0x9'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/> </controller> <controller type='pci' index='5' model='pcie-root-port'> <model name='ioh3420'/> <target chassis='5' port='0xa'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/> </controller> <controller type='pci' index='6' model='pcie-root-port'> <model name='ioh3420'/> <target chassis='6' port='0xb'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x3'/> </controller> <controller type='pci' index='7' model='pcie-root-port'> <model name='ioh3420'/> <target chassis='7' port='0xc'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x4'/> </controller> <controller type='pci' index='8' model='pcie-root-port'> <model name='ioh3420'/> <target chassis='8' port='0xd'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x5'/> </controller> <interface type='direct'> <mac address='52:54:00:e7:90:bc'/> <source dev='ens99-dummy' mode='vepa'/> <model type='rtl8139'/> <address type='pci' domain='0x0000' bus='0x02' slot='0x01' function='0x0'/> </interface> <serial type='pty'> <target type='isa-serial' port='0'/> </serial> <console type='pty'> <target type='serial' port='0'/> </console> <input type='mouse' bus='ps2'/> <input type='keyboard' bus='ps2'/> <hostdev mode='subsystem' type='usb' managed='yes'> <source> <vendor id='0x148f'/> <product id='0x5572'/> </source> <address type='usb' bus='0' port='1'/> </hostdev> <hostdev mode='subsystem' type='pci' managed='yes'> <source> <address domain='0x0000' bus='0x01' slot='0x00' function='0x0'/> </source> <address type='pci' domain='0x0000' bus='0x03' slot='0x00' function='0x0'/> </hostdev> <hostdev mode='subsystem' type='pci' managed='yes'> <source> <address domain='0x0000' bus='0x03' slot='0x00' function='0x0'/> </source> <address type='pci' domain='0x0000' bus='0x06' slot='0x00' function='0x0'/> </hostdev> <hostdev mode='subsystem' type='pci' managed='yes'> <source> <address domain='0x0000' bus='0x04' slot='0x00' function='0x0'/> </source> <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/> </hostdev> <memballoon model='virtio'> <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/> </memballoon> </devices> </domain> what I don't get is how to connect the interface above to the dummy one I've created.