The broker's amqps port is opened from anywhere so a node can enrol
before it has an overlay address — but only in the input chain. The
broker is a published container port, so a cross-node dial is DNAT'd
and forwarded, never reaching input; it survived on the first
connection's conntrack entry and no more. Adopting the foundation's own
broker restarts it, dropping that entry, after which a joined node
could never receive another declaration. The forward chain now carries
the foundation ports too, from anywhere, matching their input rule.
Intermittent in the built-store-cross-node bed: it passed whenever the
broker did not happen to restart after the joined node first connected.
jschoubben
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