Hi Pablo, On Thu, Jul 30, 2020 at 09:25:54PM +0200, Pablo Neira Ayuso wrote: > On Thu, Jul 30, 2020 at 03:57:10PM +0200, Phil Sutter wrote: > > The full list of tables in kernel is not relevant, only those used by > > iptables-nft and for those, knowing if they exist or not is sufficient. > > For holding that information, the already existing 'table' array in > > nft_cache suits well. > > > > Consequently, nft_table_find() merely checks if the new 'exists' boolean > > is true or not and nft_for_each_table() iterates over the builtin_table > > array in nft_handle, additionally checking the boolean in cache for > > whether to skip the entry or not. > > > > Signed-off-by: Phil Sutter <phil@xxxxxx> > > --- > > iptables/nft-cache.c | 73 +++++++++++--------------------------------- > > iptables/nft-cache.h | 9 ------ > > iptables/nft.c | 55 +++++++++------------------------ > > iptables/nft.h | 2 +- > > 4 files changed, 34 insertions(+), 105 deletions(-) > > This diffstat looks interesting :-) As promised, I wanted to leverage your change for further optimization, but ended up optimizing your code out along with the old one. :D > One question: > > c->table[i].exists = true; > > then we assume this table is still in the kernel and we don't recheck? Upon each COMMIT line, nft_action() calls nft_release_cache(). This will also reset the 'exists' value to false. > I mean, if you pipe command to an open process running > iptables-restore (which has been the recommended interface for years > to avoid of the overhead of system() invocation and to ensure atomic > updates), is there any cache this new approach might get out of sync? This is not just a problem of iptables-restore running in a pipe - restoring a large ruleset (or just pure coincidence) could lead to the same result. Playing with 'iptables-nft-restore --noflush' reading from stdin and calling 'nft flush ruleset' in a second shell right before entering 'COMMIT' leads to funny errors. This is not related to the table list elimination though. I'll investigate. Cheers, Phil
