router: feature toggle for experimental SCMP authentication

[matzf]

The experimental implementation of DRKey-based authentication for SCMP messages is incomplete and, in the current form, not practically useful. Add a feature flag to explicitly opt-in to the experimental SCMP authentication in the router.

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This change is 

[JordiSubira]

Reviewed 5 of 5 files at r1, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @matzf)

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doc/manuals/router.rst line 98 at r1 (raw file):

   Override the global duration for :doc:`/cryptography/drkey` epochs.
   This environment variable also applies to :program:`control`, see :envvar:`SCION_TESTING_DRKEY_EPOCH_DURATION`.

Perhaps include also cross-reference from manuals/control.html#envvar-SCION_TESTING_DRKEY_EPOCH_DURATION?

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doc/manuals/router.rst line 101 at r1 (raw file):

   :Type: :ref:`duration <control-conf-duration>`

:Default: 24h?

[matzf]

Reviewable status: 4 of 6 files reviewed, 2 unresolved discussions (waiting on @JordiSubira)

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doc/manuals/router.rst line 98 at r1 (raw file):

Previously, JordiSubira wrote…

Perhaps include also cross-reference from manuals/control.html#envvar-SCION_TESTING_DRKEY_EPOCH_DURATION?

Done. I've opted to make cross-references to the "Environment Variable" section instead of the individual envvar. It'd could be made to work with references to the individual envvar block, but it would likely become a bit unwieldy once this should be done with envvars that are shared between more than two components.

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doc/manuals/router.rst line 101 at r1 (raw file):

Previously, JordiSubira wrote…

:Default: 24h?

Done.

[JordiSubira]

Reviewed 2 of 2 files at r2, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @matzf)

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doc/manuals/router.rst line 103 at r2 (raw file):

   Also applies to the :ref:`control service <control-envvars>`.

   :Type: :ref:`duration <common-conf-duration>`

control

Code quote:

common

[matzf]

Reviewable status: 4 of 6 files reviewed, 1 unresolved discussion (waiting on @JordiSubira)

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doc/manuals/router.rst line 103 at r2 (raw file):

Previously, JordiSubira wrote…

control

Done (was overlapping change from #4416 and oversight when applying that change to this branch -- no longer relevant after merging 4416).

[JordiSubira]

Reviewed 2 of 2 files at r3, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @matzf)