Reviewed: https://review.opendev.org/c/openstack/neutron/+/926495
Committed:
https://opendev.org/openstack/neutron/commit/dbf53b7bbfa27cb74b1d0b0e47629bf3e1403645
Submitter: "Zuul (22348)"
Branch: master
commit dbf53b7bbfa27cb74b1d0b0e47629bf3e1403645
Author: Ihar Hrachyshka <ihrac...@redhat.com>
Date: Fri Aug 16 22:22:24 2024 +0000
Support nested SNAT for ml2/ovn
When ovn_router_indirect_snat = True, ml2/ovn will set a catch-all snat
rule for each external ip, instead of a snat rule per attached subnet.
NB: This option is global to cluster and cannot be controlled per
project or per router.
NB2: this patch assumes that 0.0.0.0/0 snat rules are properly handled
by OVN. Some (e.g. 22.03 and 24.03) OVN versions may have this scenario
broken. See: https://issues.redhat.com/browse/FDP-744 for details.
--
A long time ago, nested SNAT behavior was unconditionally enabled for
ml2/ovs, see: https://bugs.launchpad.net/neutron/+bug/1386041
Since this behavior has potential security implications, and since it
may not be desired in all environments, a new flag is introduced.
Since OVN was deployed without nested SNAT enabled in multiple
environments, the flag is set to False by default (meaning: no nested
SNAT).
In theory, instead of a config option, neutron could introduce a new API
to allow users to control the behavior per router. This would require
more work though. This granular API is left out of the patch. Interested
parties are welcome to start a discussion about adding the new API as a
new neutron extension to routers.
--
Before this patch, there was an alternative implementation proposed that
was not relying on 0.0.0.0/0 snat behavior implemented properly in OVN.
The implementation was abandoned because it introduced non-negligible
complexity in the neutron code and the OVN NB database.
See: https://review.opendev.org/c/openstack/neutron/+/907504
--
Closes-Bug: #2051935
Co-Authored-By: Brian Haley <haleyb....@gmail.com>
Change-Id: I28fae44edc122fae389916e25b3321550de001fd
** Changed in: neutron
Status: In Progress => Fix Released
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https://bugs.launchpad.net/bugs/2051935
Title:
[OVN] SNAT only happens for subnets directly connected to a router
Status in neutron:
Fix Released
Status in neutron package in Ubuntu:
New
Bug description:
I am trying to achieve the following scenario:
I have a VM attached to a router w/o external gateway (called project-
router) but with a default route which send all the traffic to another
router (transit router) which has an external gateway with snat
enabled and it is connected to a transit network 192.168.100.0/24
My VM is on 172.16.100.0/24, traffic hits the project-router thanks
to the default route gets redirected to the transit-router correctly,
here it gets into the external gateway but w/o being snat.
This is because in ovn I see that SNAT on this router is only enabled
for logical ip in 192.168.100.0/24 which is the subnet directly
connected to the router
# ovn-nbctl lr-nat-list neutron-6d1e6bb7-3949-43d1-8dac-dc55155b9ad8
TYPE EXTERNAL_IP EXTERNAL_PORT LOGICAL_IP
EXTERNAL_MAC LOGICAL_PORT
snat 147.22.16.207 192.168.100.0/24
But I would like that this router snat all the traffic that hits it,
even when coming from a subnet not directly connected to it.
I can achieve this by setting in ovn the snat for 0.0.0.0/0
# ovn-nbctl lr-nat-add neutron-6d1e6bb7-3949-43d1-8dac-dc55155b9ad8
snat 147.22.16.207 0.0.0.0/0
# ovn-nbctl lr-nat-list neutron-6d1e6bb7-3949-43d1-8dac-dc55155b9ad8
TYPE EXTERNAL_IP EXTERNAL_PORT LOGICAL_IP
EXTERNAL_MAC LOGICAL_PORT
snat 147.22.16.207 0.0.0.0/0
snat 147.22.16.207 192.168.100.0/24
But this workaround can be wiped if I run the neutron-ovn-db-sync-util
on any of the neutron-api unit.
Is there a way to achieve this via OpenStack? If not does it make
sense to have this as a new feature?
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