Re: iptables-nft fails to restore huge rulesets

[Phil Sutter <phil@nwl.cc>]

On Wed, Mar 31, 2021 at 03:35:10PM +0200, Florian Westphal wrote:
> Phil Sutter <phil@nwl.cc> wrote:
> > I'm currently trying to fix for an issue in Kubernetes realm[1]:
> > Baseline is they are trying to restore a ruleset with ~700k lines and it
> > fails. Needless to say, legacy iptables handles it just fine.
> > 
> > Meanwhile I found out there's a limit of 1024 iovecs when submitting the
> > batch to kernel, and this is what they're hitting.
> > 
> > I can work around that limit by increasing each iovec (via
> > BATCH_PAGE_SIZE) but keeping pace with legacy seems ridiculous:
> > 
> > With a scripted binary-search I checked the maximum working number of
> > restore items of:
> > 
> > (1) User-defined chains
> > (2) rules with merely comment match present
> > (3) rules matching on saddr, daddr, iniface and outiface
> > 
> > Here's legacy compared to nft with different factors in BATCH_PAGE_SIZE:
> > 
> > legacy		32 (stock)	  64		   128          256
> > ----------------------------------------------------------------------
> > 1'636'799	1'602'202	- NC -		  - NC -       - NC -
> > 1'220'159	  302'079	604'160		1'208'320      - NC -
> > 3'532'040	  242'688	485'376		  971'776    1'944'576
> 
> Can you explain that table? What does 1'636'799 mean? NC?

Ah, sorry: NC is "not care", I didn't consider those numbers relevant
given that iptables-nft has caught up to legacy previously already.

1'636'799 is the max number of user-defined chains I can successfully
restore using iptables-legacy-restore. Looks like I dropped the rows'
description while reformatting by accident: the first row of that table
corresponds with test (1), second with test (2) and third with test (3).

So legacy may restore at once ~1.6M chains or ~1.2M comment rules or
~3.5M rules with {s,d}{addr,iface} matches.

The following columns are for iptables-nft with varying BATCH_PAGE_SIZE
values. Each of the (max 1024) iovecs passed to kernel via sendmsg() is
'N * getpagesize()' large.

Cheers, Phil