[riot-notifications] [RIOT-OS/RIOT] gnrc_ipv6_nib/nc: remove from _next_removable on remove [backport 2019.01] (#10993)

Martine Lenders notifications at github.com
Mon Feb 11 17:41:56 CET 2019

# Backport of #10975

The RIOT community cares a lot about code quality.
Therefore, before describing what your contribution is about, we would like
you to make sure that your modifications are compliant with the RIOT
coding conventions, see https://github.com/RIOT-OS/RIOT/wiki/Coding-conventions.

### Contribution description
The `_next_removable` list manages the cache-out of the neighbor cache. However, when a neighbor cache entry is removed, it is not removed from that list, which may lead to a segmentation fault when that list is accessed, since the whole entry (including its list pointer) is zeroed
after removal.

With this change the entry is removed from that list accordingly before the zeroing happens.
Put here the description of your contribution:
- describe which part(s) of RIOT is (are) involved
- if it's a bug fix, describe the bug that it solves and how it is solved
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### Testing procedure
~~This is hard to unittests, since the removal needs to happen *while* another entry is added (so this is a race condition though I'm not 100% clear how this happens, since both operations are supposed to run in the `gnrc_ipv6` thread). I used https://gist.github.com/miri64/fac4df86be36f0a65d9bdb4d2f09d5c7#file-03-4-test-sh and obseverd `tap0` (you can do that by typing `tmux select-window -t tap0; tmux a` in another terminal). Without this PR a segfault will happen here~~


~~With this PR this segfault does not happen.~~

There is a unittest for this edge case in this PR ;-).

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- which test/example to compile for which board and is there a 'test' command
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-- Commit Summary --

  * gnrc_ipv6_nib/nc: remove from _next_removable on remove
  * tests: add unittest for state corruption in NC cache-out
  * tests/unittests: suppress cppcheck redundantAssignment warning

-- File Changes --

    M sys/net/gnrc/network_layer/ipv6/nib/_nib-internal.c (2)
    M tests/unittests/tests-gnrc_ipv6_nib/tests-gnrc_ipv6_nib-internal.c (39)

-- Patch Links --


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