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 <[email protected]>
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 <[email protected]>
    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

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