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

[Ritaro Takenaka <ritarot634@gmail.com>]

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?