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Message #87742
[Bug 1951074] Re: [OVN] default setting leak nameserver config from the host to instances
Hello Jens:
This is the expected behaviour for OVN, as documented here [1]. When
building the DHCP options, the DNS servers option is populated first
with the subnet "dns_nameservers". If empty, the "OVN.dns_servers"
option will be used. If empty, the OVN mech driver will use the local
DNS resolver (reading from "/etc/resolv.conf") [2].
Admin/user can always provide a valid DNS nameserver if needed.
Regards.
[1]https://github.com/openstack/neutron/blob/90b5456b8c11011c41f2fcd53a8943cb45fb6479/neutron/conf/plugins/ml2/drivers/ovn/ovn_conf.py#L158-L164
[2]https://github.com/openstack/neutron/blob/90b5456b8c11011c41f2fcd53a8943cb45fb6479/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_client.py#L1916-L1918
** Changed in: neutron
Status: New => Opinion
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https://bugs.launchpad.net/bugs/1951074
Title:
[OVN] default setting leak nameserver config from the host to
instances
Status in neutron:
Opinion
Bug description:
Using the default settings, i.e. without [ovn]dns_servers being
specified in ml2_conf.ini, OVN will send the nameserver addresses that
are specified in /etc/resolv.conf on the host in DHCP responses. This
may lead to unexpected leaks about the host infrastructure and thus
should at least be well documented. In most cases it will also lead to
broken DNS resolution for the instances, since when systemd-resolve is
being used, the host's nameserver address will be 127.0.0.53, and an
instance will not be able to resolve anything using that address.
Possibly a better approach would be to not send any nameserver
information via DHCP in this scenario.
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References