Shaun Brady <brady.1345@xxxxxxxxx> wrote: > > Furthermore, the largest ruleset I have archived here (iptables-save > > kubernetes ruleset dump) has 27k jumps (many who are mutually exclusive > > and user-defined chains that are always terminal), but nf_tables_api.c > > lacks the ability to detect either of these cases). > > > > With the proposed change, the ruleset won't load anymore. > > Much of my testing was omitted from the commit message. 8192 was > chosen as to what seemed significantly above normal usage; I was way > off. 8k is brain damaged^W^W very high for nftables thanks to the existence of verdict maps. The problem is iptables(-nft) and its linear rules. > What I did observe was that machines (both big and small) start > to act up around 16M. Would it ease minds to simply increase this to > something like 4M or 8M? What about going with 64k and NOT applying that limit in the init_netns? The rationale would be that if you have the priviliges to ramp up the limitation threshold that limit doesn't exist in practice anyway. > > Possible solutions to soften the impact/breakage potential: > > - make the sysctl only affect non-init-net namespaces. > > - make the sysctl only affect non-init-user-ns owned namespaces. > > I may be misunderstanding how limiting control to (only) non-init-* > namespaces would help. It certainly would keep a namespace from taking > the whole system down, but it would leave the original problem of > being able to create the deadly jump configuration purely in the > init-net. Sure, but why do you need to protect init_net? > Maybe protecting from a namespace is more fruitful than an > operator making mistakes (the initial revisions intent). I don't see how you can make such rulesets on accident. > > - Add the obseved total jump count to the table structure > > Then, when validating, do not start from 0 but from the sum > > of the total jump count of all registered tables in the same family. > > netdev family will need to be counted unconditionally. > > I had not considered one could spread the problem across multiple > tables (even if you can't jump between them). This is a good insight, > and I will account for this. Thanks!
