[ovs-build] Passed: ovsrobot/ovn#1097 (series_208011 - 95b3e6f)

[Travis CI]

Build Update for ovsrobot/ovn
-------------------------------------

Build: #1097
Status: Passed

Duration: 23 mins and 52 secs
Commit: 95b3e6f (series_208011)
Author: Dumitru Ceara
Message: ofctrl.c: Add a predictable resolution for conflicting flow actions.

Until now, in case the ACL configuration generates openflows that have
the same match but different actions, ovn-controller was using the
following approach:
1. If the flow being added contains conjunctive actions, merge its
   actions with the already existing flow.
2. Otherwise, if the flow is being added incrementally
   (update_installed_flows_by_track), don't install the new flow but
   instead keep the old one.
3. Otherwise, (update_installed_flows_by_compare), don't install the
   new flow but instead keep the old one.

Even though one can argue that having an ACL with a match that includes
the match of another ACL is a misconfiguration, it can happen that the
users provision OVN like this.  Depending on the order of reading and
installing the logical flows, the above operations can yield
unpredictable results, e.g., allow specific traffic but then after
ovn-controller is restarted (or a recompute happens) that specific
traffic starts being dropped.

A simple example of ACL configuration is:
ovn-nbctl acl-add ls to-lport 3 '(ip4.src==10.0.0.1 ||
ip4.src==10.0.0.2) && (ip4.dst == 10.0.0.3 || ip4.dst == 10.0.0.4)' allow
ovn-nbctl acl-add ls to-lport 3 'ip4.src==10.0.0.1' allow
ovn-nbctl acl-add ls to-lport 2 'arp' allow
ovn-nbctl acl-add ls to-lport 1 'ip4' drop

This is a pattern used by most CMSs:
- define a default deny policy.
- punch holes in the default deny policy based on user specific
  configurations.

Without this commit the behavior for traffic from 10.0.0.1 to 10.0.0.5
is unpredictable.  Depending on the order of operations traffic might be
dropped or allowed.

It's also quite hard to force the CMS to ensure that such match overlaps
never occur.

To address this issue we now ensure that all desired flows refering the
same installed flow are partially sorted in the following way:
- first all flows with action "allow".
- then all flows with action "drop".
- then a single flow with action "conjunction" (resulting from merging
  all flows with the same match and action conjunction).

This ensures that "allow" flows have precedence over "drop" flows which
in turn have precedence over "conjunction" flows.  Essentially less
restrictive flows are always preferred over more restrictive flows whenever a match
conflict happens.

CC: Daniel Alvarez <dalvarez at redhat.com>
Reported-at: https://bugzilla.redhat.com/1871931
Signed-off-by: Dumitru Ceara <dceara at redhat.com>
Signed-off-by: 0-day Robot <robot at bytheb.org>

View the changeset: https://github.com/ovsrobot/ovn/commit/95b3e6f3ceee

View the full build log and details: https://travis-ci.com/github/ovsrobot/ovn/builds/190222595?utm_medium=notification&utm_source=email


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