[ovs-dev] [PATCH ovn 2/2] northd: Remove "reachable" functions and users of them.

[Ben Pfaff]

On Wed, Mar 10, 2021 at 09:28:43AM -0500, Mark Michelson wrote:
> Self-originated ARPs are intended to be sent to the "owning" router for
> a given IP address, as well as flooded to non-router ports on a logical
> switch.
> 
> When trying to determine the owning router for an IP address, we would
> iterate through load balancer and NAT addresses, and check if these IP
> addresses were "reachable" on this particular router. Reachable here
> means that the NAT external IP or load balancer VIP falls within any of
> the networks served by this router. If an IP address were determined not
> to be reachable, then we would not try to send ARPs for that particular
> address to the router.
> 
> However, it is possible (and sometimes desired) to configure NAT floating
> IPs on a router that are not in any subnet handled by that router.
> In this case, OVN refuses to send ARP requests to the router on which the
> floating IP has been configured. The result is that internally-generated
> traffic that targets the floating IP cannot reach its destination,
> since the router on which the floating IP is configured never receives ARPs
> for the floating IP.
> 
> This patch fixes the issue by removing the reachability checks
> altogether. If a router has a NAT external IP or load balancer VIP that
> is outside the range of any of its configured subnets, we still should
> send ARPs to that router for those requested addresses.
> 
> Reported at: https://bugzilla.redhat.com/show_bug.cgi?id=1929901
> 
> Signed-off-by: Mark Michelson <mmichels at redhat.com>

I compared the C and DDlog changes and they match.  I didn't otherwise
review this:
Acked-by: Ben Pfaff <blp at ovn.org>