Everything should be able to call what runs on the same machine, another machine's
service exposed to the private network, and another machine's service exposed
publicly. Three cases; the filter had two.
The first was expressed as the machines' own addresses on the private network. A
caller on the machine carries such an address; a caller in one of its containers
carries a bridge address and matched nothing — measured, same destination and same
machine: src 10.10.0.1 against src 172.17.0.8. The second case worked by accident,
because the tunnel rewrites a caller's address to the sending machine's. Two of
three working is why it read as correct.
0143 answered the wrong question. It proposed verifying each grant from the
consumer's own network position and went to length about which position, because
whether a caller sat in a container changed the answer — and that difference was the
bug. Observing a configuration error is not its remedy. Superseded, and nothing
replaces it; whether the mesh should check a grant is still open in issue 145 and
must stand on its own.
And a module is not a container: 61 of 72 happen to use one, 11 do not, and a rule
reasoning about containers describes most of the mesh rather than the mesh.
A grant is four facts and a credential — the provision, the machine, the port, and
who the consumer is when it connects — and it is the whole mechanism by which
anything in the mesh reaches anything else. The mesh asserted it and never found
out whether it was true. Issue 145 is what that cost: eleven hours of 'every module
current with its source' while a module could not reach its database.
The consumer verifies it, from its own network position. Not the control plane,
which reaches the address by a path no consumer uses. Not the machine, whose own
packets carried a source address the filter admitted while every container's was
refused — so a host-side check would have passed throughout the outage it exists to
catch. That is inference from the rule that was loaded, stated as such.
A connection and nothing more; speaking each provision's protocol would be a second
implementation of every provision. One failure is not news, only consecutive ones,
and the count is reported rather than the last attempt. A consumer that is not
running reads unchecked, which is a different sentence from broken.
What it costs to be wrong is the constraint on all of it: a check that calls a
working provision broken trains a reader to ignore the report.
jschoubben