Re: [PATCH] nf_flowtable: ensure dst.dev is not blackhole

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

On Sun, May 01, 2022 at 02:23:55AM +0900, Ritaro Takenaka wrote:
> On 2022/04/28 0:10, Pablo Neira Ayuso wrote:> On Tue, Apr 26, 2022 at 09:28:13PM +0900, Ritaro Takenaka wrote:
> >> Thanks for your reply.
> >>
> >>> In 5.4, this check is only enabled for xfrm.
> >> Packet loss occurs with xmit (xfrm is not confirmed).
> >> I also experienced packet loss with 5.10, which runs dst_check periodically.
> >> Route GC and flowtable GC are not synchronized, so it is
> >> necessary to check each packet.
> >>
> >>> dst_check() should deal with this.
> >> When dst_check is used, the performance degradation is not negligible.
> >> From 900 Mbps to 700 Mbps with QCA9563 simple firewall.
> > 
> > You mention 5.10 above.
> > 
> > Starting 5.12, dst_check() uses INDIRECT_CALL_INET.
> > 
> > Is dst_check() still slow with >= 5.12?
> > 
> > Asking this because my understanding (at this stage) is that this
> > check for blackhole_netdev is a faster way to check for stale cached
> > routes.
> 
> I did the performance tests with 5.15, confirmed dst_check() is not slower
> than checking for blackhole_netdev.
> 
> Good, dst_check() can be used.
> 
> Then, stale routes check should be moved from nf_flow_offload_gc_step() to
> nf_flow_offload(_ipv6)_hook(). Is it correct?

Then, the check from packet path needs to be restored.