doc: fix envvar documentation, fix references

Fix duplicate envvar documentation (envvars can only have one definition
in rst), and expand the description. Consistent formatting for envvar
documentation.
Move the description of the duration string format to the common
section, as it's referenced by multiple components (currently control
service and router).

Fix reference to spao.

doc/manuals/common.rst

@@ -345,6 +345,28 @@ of the individual fields below.
    .. option:: addr = <ip:port>, required
 
       See ``control_service.addr``, above.
+
+.. _common-conf-duration:
+
+Duration Format
+===============
+
+Where duration values are loaded from configuration options, the following format is expected:
+
+.. code-block::
+
+   [\-0-9]+(y|w|d|h|m|s|ms|us|µs|ns)
+
+The unit suffixes have their usual meaning of ``y`` year, ``w`` week, ``d`` day, ``h`` hour,
+``m`` minute, ``s`` second, ``ms`` millisecond, ``us`` or ``µs`` microsecond, and ``ns`` nanosecond.
+
+Mixed unit durations are not supported (e.g. ``1h10m10s`` is not supported).
+The long duration units are simple factors, not calendar offsets:
+
+- ``d`` is always 24 hours
+- ``w`` is always 7 days
+- ``y`` is always 365 days
+
 .. _common-http-api:
 
 HTTP API

doc/manuals/control.rst

@@ -76,7 +76,7 @@ Environment variables
    This can only work correctly if the same value is set for all connected control services in the
    test network.
 
-   The format is a :ref:`duration <control-conf-duration>` with unit suffix (e.g. ``10s``).
+   :Type: :ref:`duration <common-conf-duration>`
 
 Configuration
 =============
@@ -264,7 +264,7 @@ considers the following options.
 
       .. option:: ca.service.lifetime = <duration> (Default: "10m")
 
-         Validity period (a :ref:`duration <control-conf-duration>`) of JWT authorization tokens
+         Validity period (a :ref:`duration <common-conf-duration>`) of JWT authorization tokens
          for the CA service.
 
       .. option:: ca.service.client_id = <string> (Default: general.id)
@@ -315,7 +315,7 @@ considers the following options.
 
       Expiration of cached entries in nanoseconds.
 
-      **TODO:** this should be changed to accept values in :ref:`duration format <control-conf-duration>`.
+      **TODO:** this should be changed to accept values in :ref:`duration format <common-conf-duration>`.
 
 .. object:: drkey
 
@@ -775,29 +775,6 @@ There is one top-level entry for each type of metadata, all of which are optiona
 
    A free form string to communicate interesting/important information to other network operators.
 
-
-.. _control-conf-duration:
-
-Duration Format
----------------
-
-Where duration values are loaded from configuration options, the following format is expected:
-
-.. code-block::
-
-   [\-0-9]+(y|w|d|h|m|s|ms|us|µs|ns)
-
-The unit suffixes have their usual meaning of ``y`` year, ``w`` week, ``d`` day, ``h`` hour,
-``m`` minute, ``s`` second, ``ms`` millisecond, ``us`` or ``µs`` microsecond, and ``ns`` nanosecond.
-
-Mixed unit durations are not supported (e.g. ``1h10m10s`` is not supported).
-The long duration units are simple factors, not calendar offsets:
-
-- ``d`` is always 24 hours
-- ``w`` is always 7 days
-- ``y`` is always 365 days
-
-
 Port table
 ==========
 

doc/manuals/router.rst

@@ -62,40 +62,61 @@ Environment Variables
    Can be overridden for specific inter-AS BFD sessions with :option:`bfd.disable <topology-json disable>`
    in an interface entry in the ``topology.json`` configuration.
 
+   :Type: bool (``0``/``f``/``F``/``FALSE``/``false``/``False``,  ``1``/``t``/``T``/``TRUE``/``true``/``True``)
+   :Default: ``false``
+
 .. envvar:: SCION_EXPERIMENTAL_BFD_DETECT_MULT
 
    Set the :term:`BFD` detection time multiplier.
 
-   Default 3
-
    Same applicability as above; can be overridden for specific inter-AS BFD sessions with
    :option:`bfd.detect_mult <topology-json detect_mult>`.
 
+   :Type: unsigned integer
+   :Default: ``3``
+
 .. envvar:: SCION_EXPERIMENTAL_BFD_DESIRED_MIN_TX
 
    Defines the frequence at which this router should send :term:`BFD` control messages.
 
-   Default 200ms
-
    Same applicability as above; can be overridden for specific inter-AS BFD sessions with
    :option:`bfd.desired_min_tx_interval <topology-json desired_min_tx_interval>`.
 
+   :Type: :ref:`duration <common-conf-duration>`
+   :Default: ``200ms``
+
 .. envvar:: SCION_EXPERIMENTAL_BFD_REQUIRED_MIN_RX
 
    Defines an frequence at which this router should send :term:`BFD` control messages.
 
-   Default 200ms
-
    Same applicability as above; can be overridden for specific inter-AS BFD sessions with
    :option:`bfd.required_min_rx_interval <topology-json required_min_rx_interval>`.
-.. envvar:: SCION_TESTING_DRKEY_EPOCH_DURATION
 
-   Defines the global DRKey :ref:`Epoch<drkey-epoch>` duration that the border router
-   assumes.
+   :Type: :ref:`duration <common-conf-duration>`
+   :Default: ``200ms``
+
+.. object:: SCION_TESTING_DRKEY_EPOCH_DURATION
+
+   For **testing only**.
+   This option relates to :ref:`DRKey-based authentication of SCMPs <scmp-authentication>` in the
+   router, which is **experimental** and currently **incomplete**.
+
+   Override the global duration for :doc:`/cryptography/drkey` epochs.
+   This environment variable also applies to :program:`control`, see :envvar:`SCION_TESTING_DRKEY_EPOCH_DURATION`.
+
+   :Type: :ref:`duration <common-conf-duration>`
 
 .. envvar:: SCION_TESTING_ACCEPTANCE_WINDOW
 
-   Defines the acceptance window following the :ref:`SPAO specification<spao-absTime>`.
+   For **testing only**.
+   This option relates to :ref:`DRKey-based authentication of SCMPs <scmp-authentication>` in the
+   router, which is **experimental** and currently **incomplete**.
+
+   Defines the length of the window around the current time for which SCMP authentication timestamps
+   are accepted. See :ref:`SPAO specification <spao-absTime>`.
+
+   :Type: :ref:`duration <common-conf-duration>`
+   :Default: 5m
 
 Configuration
 =============

doc/protocols/authenticator-option.rst

@@ -60,7 +60,7 @@ Timestamp / Sequence Number:
   (See :ref:`Appendix<spao-appendix>` for a more detailed explanation about the field interpretation).
   The timestamp MAY be used to compute the absolute time (*AbsTime*) value,
   which corresponds to the time when the packet was sent.
-  The section :ref:`Absolute time derivation<spao-timestamp>` describes the derivation of *AbsTime* and
+  The section :ref:`Absolute time derivation<spao-absTime>` describes the derivation of *AbsTime* and
   the associated DRKey.
 
   The receiver SHOULD drop packets with *AbsTime* outside of a locally chosen