Thanks for the review!

On 16/03/2023 14:59, Wolfgang Bumiller wrote:
Both seem a bit excessive to me.

Let's look at the data:
We have a set of ranges consisting of a type, 2 starts and a count.
The types are uids and gids, so we can view those as 2 separate
instances of sets of [ct_start, host_start, count].
Since neither the container nor the host sides must overlap we can -
again - view these as separate sets of container side [start, count] and
host side [start, count].
In other words, we can see the entire id map as just 4 sets of [start,
count] ranges which must not overlap.

So I think all we need to do is sort these by the 'start' value, and for
each element make sure that

     prevous_start + previous_count <= current_start

And yes, that means we need to sort $id_maps twice, once by ct id, once
by host id, and then iterate and do the above check.

Should be much shorter (and faster).

Yeah, good point, splitting $id_maps into separate uid/gid maps, and then sorting+iterating twice (I'll call this the "sorting algorithm" below) does sound more understandable than the current ad-hoc approach, and faster too.

However, one small benefit of iterating over $id_maps in its original order (instead of sorting) is that the error message always references the *first* invalid map entry in the config, e.g. (omitting host uids for clarity)

  1) u 1000 <...> 100
  2) u 950 <...> 100
  3) u 900 <...> 100
  4) u 850 <...> 100

The sorting algorithm would error on entry 3, which might suggest to users that entries 1-2 are okay (which they are not). The current algorithm errors on line 2 already. Similar things would happen with interleaved uid/gid mappings, I guess.

But I'm not sure if this really matters to users. What do you think?


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