Re: [nft PATCH 3/7] libnftables: Introduce nft_ctx_flush_cache()

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Fri, Oct 20, 2017 at 07:05:13PM +0200, Phil Sutter wrote:
> Hi,
> 
> On Fri, Oct 20, 2017 at 02:13:26PM +0200, Pablo Neira Ayuso wrote:
> > On Thu, Oct 19, 2017 at 10:18:43AM +0200, Phil Sutter wrote:
> [...]
> > > +void nft_ctx_flush_cache(struct nft_ctx *ctx)
> > > +{
> > > +	iface_cache_release();
> > > +	cache_release(&ctx->cache);
> > > +}
> > 
> > This flush allows us to release the cache, but nft_ctx_alloc()
> > populates it. I'm missing something here, can we force a context
> > repopulation?
> 
> No, nft_ctx_alloc() does not populate the cache, but just initialize
> cache list head (which is not undone by cache_release()). Cache
> population happens during command execution depending on whether a cache
> is needed or not.

I see.

I think cache population should happen from nft_ctx_alloc(), caches
are context after all.

> > If there is no usecase for this yet, I would keep this behind by now.
> 
> The use-case for the above is cli_complete(), which
> explicitly drops the cache after execution of every command (probably
> because it's potentially long-lived and therefore things might change in
> background).

I see. If we follow the approach I'm describe above, then we need
something like nft_ctx_reset(), where we reset all context and we get
a fresh cache.

Makes sense to you?