Comment 2 for bug 1810067

it is problematic that traceback created from Virt manager is not enough to debug virt manager.

but here it goes:

No guest, no guest network, i did not said there is a ui option called "on virtual network creation" just go to "virtual networks" on ui and push play button to start network. it throws up the posted Traceback on UI.

Package: virt-manager
Version: 1:1.3.2-3ubuntu1.16.04.4
Priority: optional
Section: universe/admin
Origin: Ubuntu
Maintainer: Ubuntu Developers <email address hidden>
Original-Maintainer: Debian Libvirt Maintainers <email address hidden>

there is no info that i can give you to solve this bug. because problem lies within code that is ugly filled with unreasonable assumptions. They should not code on assumptions they did not checked first.

here is the default one:

Error starting network 'default': internal error: Child process (VIR_BRIDGE_NAME=virbr0 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper) unexpected exit status 149: Segmentation fault

dnsmasq: lease-init script returned exit code 139

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 90, in cb_wrapper
    callback(asyncjob, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 126, in tmpcb
    callback(*args, **kwargs)
  File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 83, in newfn
    ret = fn(self, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/network.py", line 81, in start
    self._backend.create()
  File "/usr/lib/python2.7/dist-packages/libvirt.py", line 2952, in create
    if ret == -1: raise libvirtError ('virNetworkCreate() failed', net=self)
libvirtError: internal error: Child process (VIR_BRIDGE_NAME=virbr0 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper) unexpected exit status 149: Segmentation fault

dnsmasq: lease-init script returned exit code 139

content of default.conf:

##WARNING: THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
##OVERWRITTEN AND LOST. Changes to this configuration should be made using:
## virsh net-edit default
## or other application using the libvirt API.
##
## dnsmasq conf file created by libvirt
strict-order
user=libvirt-dnsmasq
pid-file=/var/run/libvirt/network/default.pid
except-interface=lo
bind-dynamic
interface=virbr0
dhcp-range=192.168.122.2,192.168.122.254
dhcp-no-override
dhcp-lease-max=253
dhcp-hostsfile=/var/lib/libvirt/dnsmasq/default.hostsfile
addn-hosts=/var/lib/libvirt/dnsmasq/default.addnhosts

it is a fresh install. i suspect if i run virt-manager with sudo it will go away but i won't.