On 7/20/20 12:38 PM, daggs wrote:
Greetings,
I've setup an vm with openwrt in it, defined a isolated lan between the vm and the host and booted the vm up.
I see the vm is up, made sure the vnic is visible in both the host and guest and added it to the br in the guest.
I've issued an dhcpd call on the vnic (labeled vnic0) in the host and got an ip, see:
dagg@NCC-5001D ~ $ dhcpcd vnet0
You didn't run "dhcpd" (which is a dhcp server) on the host, you ran
"dhcpcd", which is a dhcp *client*. So you've ended up assigning an IP
address to the tap device on the host. I guess the dhcp server that's
issuing this IP address is part of openwrt in the guest?
A tap device on the host that is attached to a bridge is merely a
conduit between the guest's emulated NIC and the bridge device on the
host, and should not have its own IP address (although it may work in
certain cases, yours apparently being one of them, since you say the
same setup works on a debian 10 host; hmm - maybe in the debian host you
had been running dhcpcd on the bridge device rather than the tap?). In
general when there is a bridged connection on the host, the IP address
for the guest should be on the emulated network device *in the guest*,
and the IP address for the host side of that connection should be on the
bridge device in the host, *not* the tap device.
Now if the openwrt guest and the host are the only two entities
communicating on this connection, then you could put an IP address on
the tap device directly, but in that case you wouldn't want the tap to
be attached to a bridge anyway. If that's the case, just define the
interface in the guest as something like this:
<interface type='ethernet'>
<mac address='52:54:00:10:20:bf'/>
<source>
<ip address='192.168.1.130' prefix='24'/>
</source>
<model type='virtio'/>
</interface>
The IP address inside <source> will set the IP of the *host* side of the
tap device. You can also add routes to the host's routing table inside
<source>. See https://libvirt.org/formatdomain.html#ipconfig for details
(it is very important to remember that the <ip>/<route> *inside the
<source> element* is used to set the IP address of the host side of the
tap. An <ip>/<route> as a toplevel subelement of <interface> is intended
to set those properties *in the guest*, and won't work at all in the
case of qemu, since the hypervisor in that case has no visibility into
the guest's IP network configuration).
DUID 00:01:00:01:23:dd:d8:5b:e0:d5:5e:d9:f2:e2
vnet0: IAID 00:10:20:bf
vnet0: rebinding lease of 192.168.1.130
vnet0: probing address 192.168.1.130/24
vnet0: soliciting an IPv6 router
vnet0: leased 192.168.1.130 for 43200 seconds
vnet0: adding route to 192.168.1.0/24
vnet0: adding default route via 192.168.1.1
forked to background, child pid 26279
dagg@NCC-5001D ~ $ ifconfig
virtsw0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether 52:54:00:3e:3f:88 txqueuelen 1000 (Ethernet)
RX packets 123098 bytes 16327962 (15.5 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 6 bytes 252 (252.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
vnet0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.130 netmask 255.255.255.0 broadcast 192.168.1.255
inet6 fe80::fc54:ff:fe10:20bf prefixlen 64 scopeid 0x20<link>
ether fe:54:00:10:20:bf txqueuelen 1000 (Ethernet)
RX packets 45 bytes 8002 (7.8 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 39 bytes 2676 (2.6 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
dagg@NCC-5001D ~ $ ping 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
^C
--- 192.168.1.1 ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 1018ms
the vm's xml can be found at https://pastebin.com/1gXBGcPb
virtsw0 is defined as follows:
<network connections='1'>
<name>virtsw0</name>
<uuid>c8eb15a3-cc5c-4bd6-8f3b-5790792ddccc</uuid>
<bridge name='virtsw0' stp='on' delay='0'/>
<mac address='52:54:00:3e:3f:88'/>
</network>
the os is gentoo, the versions are libvirt-6.2.0 qemu-5.0.0.
I have another server running debian 10 with the same virtsw0 definition, there the connection is working.
Check the iptables rules on both hosts and both guests to see if there
are any differences.
/var/lib/libvirt/dnsmasq/virtsw0.macs has only [] in it, can that be the issue?
Since in your case the host is a dhcp *client*, that is irrelevant. I'm
actually surprised that the file exists at all, since you have no <dhcp>
section in your network definition, so dnsmasq should even be run.
Thanks,
Dagg.
