Subject: [bug#72337] Add /etc/subuid and /etc/subgid support

From: paul <[email-masked]>
Date: Tue, 8 Oct 2024 00:35:10 +0200

Hi Ludo’ ,

I think I have addressed your comments. I have now implemented two 
separate code paths: - when the request is specific (i.e. the subid 
range has a start) we can traverse the tree logarithmically

- when the request is generic (i.e. the subid range does not have a 
start) the search is linear since all the nodes have to be visited worst 
case to avoid leaving empty spaces interleaved, that could actually 
evade requests

As for estimating the size of the input, I'm not sure I know enough to 
answer this. My reasoning has been: in general the number of possible 
subids (i.e. %subordinate-id-max - %subordinate-id-min) is huge. The use 
case I have in mind for subids is rootless podman, so how many users in 
average need to use rootless containers on a system and how many subids 
are they to request in average are two very good questions I don't know 
how to answer yet, or where I could find data for. Let me know if you 
have any idea.

Please let me know if this v5 looks ok, thank you a lot for your help. 
giacomo