[riot-notifications] [RIOT-OS/RIOT] gnrc_ipv6_nib/nc: remove from _next_removable on remove (#10975)

Martine Lenders notifications at github.com
Fri Feb 8 17:00:52 CET 2019


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### 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.
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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

https://github.com/RIOT-OS/RIOT/blob/master/sys/net/gnrc/network_layer/ipv6/nib/_nib-internal.c#L153

With this PR this segfault does not happen.
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You can view, comment on, or merge this pull request online at:

  https://github.com/RIOT-OS/RIOT/pull/10975

-- Commit Summary --

  * gnrc_ipv6_nib/nc: remove from _next_removable on remove

-- File Changes --

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

-- Patch Links --

https://github.com/RIOT-OS/RIOT/pull/10975.patch
https://github.com/RIOT-OS/RIOT/pull/10975.diff

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