DNP3 Master comms point defect about opendatacon HOT 4 CLOSED

Another possible solution might be to disable and re-enable the stack on a link timeout.

from opendatacon.

After some investigation:

• There's no way to close the connection directly. The opendnp3 API only exposes a Shutdown() interface on the channel which destroys everything. The only way to get it to close is to disable all the stations on the channel together, and that's not feasible with the current architecture.
• Disabling and enabling the stack should solve the immediate issue of ensuring the startup integrity scan is triggered, and for the single drop case the connection will close, but it leaves the issue of broken connections remaining open for multidrop...

So I'll implement the disable/enable workaround and open a separate issue for the underlying broken connection issue.

from opendatacon.

Commits
c0dac2f
3b36018
07208b6
should solve this issue.
A summary of the changes:

• Refactored the link state logic and channel handling in general
  • This exposed a regression that appeared in June 2018 on multidrop channel listening - fixed
  • It also exposed a logical error or false assumption about the link layer callbacks from opendnp3
    • There's not always a callback when a link recovers, because there isn't always a keepalive success or link status change
      • Fixed by setting the link up on IIN callback for master and time without a keepalive failure for outstation
• Added a watchdog for each channel to coordinate a synchronised restart of protocol stacks if all links on a channel go down

This all means that multidrop station failures don't affect the other stations on a channel, but channels still get reset if all station are affected.

TODO: add test cases

• For both Outstations and Masters, and both directions (and a mix) of TCP client/server
  • single drop link failure = channel closed and re-established
  • multidrop partial links failure = links fail and re-establish without channel close (comms point behaves)
  • multidrop all links failure = channel closed and re-established

from opendatacon.

Tests added

from opendatacon.