Re: [iptables PATCH 00/18] nft: Sorted chain listing et al.

[Phil Sutter <phil@nwl.cc>]

Hi Pablo,

On Mon, Jul 27, 2020 at 12:20:16PM +0200, Pablo Neira Ayuso wrote:
> On Sat, Jul 25, 2020 at 01:55:41PM +0200, Phil Sutter wrote:
> > Hi Pablo,
> > 
> > On Thu, Jul 23, 2020 at 02:22:57PM +0200, Pablo Neira Ayuso wrote:
> > > On Sat, Jul 11, 2020 at 12:18:13PM +0200, Phil Sutter wrote:
> > > > Work in this series centered around Harald's complaint about seemingly
> > > > random custom chain ordering in iptables-nft-save output. nftables
> > > > returns chains in the order they were created which differs from
> > > > legacy iptables which sorts by name.
> > > > 
> > > > The intuitive approach of simply sorting chains in tables'
> > > > nftnl_chain_lists is problematic since base chains, which shall be
> > > > dumped first, are contained in there as well. Patch 15 solves this by
> > > > introducing a per-table array of nftnl_chain pointers to hold only base
> > > > chains (the hook values determine the array index). The old
> > > > nftnl_chain_list now contains merely non-base chains and is sorted upon
> > > > population by the new nftnl_chain_list_add_sorted() function.
> > > > 
> > > > Having dedicated slots for base chains allows for another neat trick,
> > > > namely to create only immediately required base chains. Apart from the
> > > > obvious case, where adding a rule to OUTPUT chain doesn't cause creation
> > > > of INPUT or FORWARD chains, this means ruleset modifications can be
> > > > avoided completely when listing, flushing or zeroing counters (unless
> > > > chains exist).
> > > 
> > > Patches from 1 to 7, they look good to me. Would it be possible to
> > > apply these patches independently from this batch or they are a strong
> > > dependency?
> > 
> > I just pushed them after making sure they don't break any of the
> > testsuites. Fingers crossed I didn't miss a detail which breaks without
> > the other patches. :)
> 
> Good.
> 
> > > I think it's better if we go slightly different direction?
> > > 
> > > https://patchwork.ozlabs.org/project/netfilter-devel/patch/20200723121553.7400-1-pablo@netfilter.org/
> > 
> > That's interesting. At least it would allow us to reorganize the
> > cache-related data structures, e.g. move the nft_cache->table array
> > items into nft_cache->table items.
> > 
> > > Instead of adding more functions into libnftnl for specific list
> > > handling, which are not used by nft, use linux list native handling.
> > 
> > OK.
> > 
> > > I think there is not need to cache the full nftnl_table object,
> > > probably it should be even possible to just use it to collect the
> > > attributes from the kernel to populate the nft_table object that I'm
> > > proposing.
> > 
> > Yes, for iptables-nft at least we should be completely fine with table
> > name alone.
> 
> Good.
> 
> > > IIRC embedded people complained on the size of libnftnl, going this
> > > direction I suggest, we can probably deprecated iterators for a number
> > > of objects and get it slimmer in the midrun.
> > 
> > OK. I'll keep that in mind.
> > 
> > So I'll rework my changes based on your nft_table idea and introduce an
> > nft_chain struct to be organized in a standard list_head list. This will
> > allow me to perform the sorting in iptables-nft itself.
> 
> Good.
> 
> > Should I base this onto your nft_table patch (and exploit it a bit
> > further) or keep them separate for now?
> 
> I'll push it out so you can rebase on top, OK?

Yes, that's fine with me!

Thanks, Phil