netdev - Re: ping6 packets high probability loss occurs by the default firewalld rule(rpfilter invert) with low traffic generated by iperf

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Message-ID: <243d02cf-2e36-5db5-5cdd-cb8a09b22e87@huawei.com>
Date:   Thu, 14 Nov 2019 21:04:23 +0800
From:   hujunwei <hujunwei4@...wei.com>
To:     David Ahern <dsahern@...il.com>,
        Eric Dumazet <eric.dumazet@...il.com>, <davem@...emloft.net>,
        <kafai@...com>, <weiwan@...gle.com>
CC:     <netdev@...r.kernel.org>, <wangxiaogang3@...wei.com>,
        <xuhanbing@...wei.com>
Subject: Re: ping6 packets high probability loss occurs by the default
 firewalld rule(rpfilter invert) with low traffic generated by iperf

Hi David,

On 2019/11/12 9:35, David Ahern wrote:
> On 11/11/19 6:26 PM, hujunwei wrote:
>>
>>
>> Hi Eric,
>> I applied the patch and find packetes still drop with default value of gc_thresh.
>> I will submit a patch later.
>>
>> Regards Junwei
>>
> 
> perhaps it is time to update IPv6's gc_thresh to match IPv4's - meaning
> it stays but gets set to -1 and is not used. Is there a reason to keep a
> limit these days?
> 
I think it is unnecessary to keep this limit, because the default gc_thresh will result in ipv6 packet loss in low ipv6 traffic.
There are two solutions:
1) Why not check the percpu route first in ip6_pol_route_lookup() when rt6_find_cached_rt() retrun NULL, just like ip6_pol_route(). Can anyone help to answer this?
2) like you said, set gc_thresh to -1.

Regards Junwei