netdev - Re: flush cache according to 'preferred life time'

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Message-ID: <500D0A24.6060200@cn.fujitsu.com>
Date:	Mon, 23 Jul 2012 16:24:04 +0800
From:	Gao feng <gaofeng@...fujitsu.com>
To:	BALAKUMARAN KANNAN <balakumarank@...aelxsi.co.in>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: flush cache according to 'preferred life time'

于 2012年07月23日 16:12, BALAKUMARAN KANNAN 写道:
> 
> ________________________________________
> From: netdev-owner@...r.kernel.org [netdev-owner@...r.kernel.org] on behalf of Gao feng [gaofeng@...fujitsu.com]
> Sent: Monday, July 23, 2012 1:35 PM
> To: BALAKUMARAN KANNAN
> Cc: netdev@...r.kernel.org
> Subject: Re: flush cache according to 'preferred life time'
> 
> 于 2012年07月23日 15:36, BALAKUMARAN KANNAN 写道:
>> Hello all,
>>     I am running test casees for IPv6 conformation on linux-3.0.26 kernel. Here I am facing a problem in routing advertisement. Once test case sets the 'preferred life time' to 20 seconds for a particular destination. And continuously sending ICMP REQUEST. It is expected that the ICMP_REPLY should stop in 20 seconds. But as because the default gc_interval is 30seconds, even after the timer expiry of the route, it is staying in the router cache. So even after 20 seconds, the nut(node under test) sends ICMP_REPLY. So if I changes gc_interval to 1, the test is getting passed.
>>
>>     But if I changes gc_interval to 1 seconds another test case in pmtu section fails. It expects that the nut should hold pmtu(path mtu) information for different value. So if I flushes the cache, the pmtu value is turning back to default.
>>
>>     So I made the kernel to alter its gc_interval value according to the 'preferred life time' of the path. Here is my path. Kindly tell me whether my idea is correct. Am I missing something?
>>
> 
> Is this commit 1716a96101c49186bb0b8491922fd3e69030235f what you need?
> 
>> --------------------------------------------------------------------------------------
>> --- ../linux-3.0.y-BRANCH_SS-RT.git.fresh/net/ipv6/ndisc.c.bak  2012-07-23 12:50:46.000000000 +0530
>> +++ ../linux-3.0.y-BRANCH_SS-RT.git.fresh/net/ipv6/ndisc.c      2012-07-23 12:54:17.000000000 +0530
>> @@ -1160,6 +1160,9 @@
>>
>>         __u8 * opt = (__u8 *)(ra_msg + 1);
>>
>> +        struct net *net = dev_net(skb->dev);
>> +        fib6_run_gc(1, net);
>> +
>>         optlen = (skb->tail - skb->transport_header) - sizeof(struct ra_msg);
>>
>>         if (!(ipv6_addr_type(&ipv6_hdr(skb)->saddr) & IPV6_ADDR_LINKLOCAL)) {
>> @@ -1200,6 +1203,22 @@
>>                 return;
>>         }
>>
>> +        if (*opt == 3) {
>> +                printk("<8> IN OPT 3\n");
>> +                struct net *net = dev_net(skb->dev);
>> +                fib6_run_gc(1, net);
>> +                int pref_life_time =  ntohl(*((int *) (((char *) (opt)) + 8)));
>> +                if ((pref_life_time != 0) && (pref_life_time < 50)) {
>> +                        printk("<8> gc_interval CHANGED\n");
>> +                        //init_net.ipv6.sysctl.flush_delay = 1;
>> +                        init_net.ipv6.sysctl.ip6_rt_gc_interval = 1 * HZ;
>> +                }
>> +                else {
>> +                        init_net.ipv6.sysctl.ip6_rt_gc_interval = 30 * HZ;
>> +                }
>> +
>> +        }
>> +
>>         if (!accept_ra(in6_dev))
>>                 goto skip_linkparms;
>> --------------------------------------------------------------------------------------
>>
>> Note: This is not well structured. I just created it for temparory solution. Just clarify me whether this idea is right.
>>
>> And Please let me know why pmtu value is not stored in routing table but only in cache.
> 
> I think the pmtu should be belong to destination.the different destinations may have
> different pmtu,even they use same route entry.
> 
> So what you are comming to say, there will not be any entry in routing table for each destination but only in routing cache. So the pmtu value is updated in the cache not in the routing table. thank you. Also I have one more doubt. Is there a way to delete an entry (particular entry) from cache once the corresponding entry in the routing table is expired. As in my case, the routing table entry is expired in 20 seconds. but the cache entry is available till next cache flush. But I want to delete the entry from cache once the entry in routing table is expired. I believe you understand.
> 

Yes,I think so too.

> Thank you Geo feng-san for Interest.

I don't know if this commit is what you are finding.
1716a96101c49186bb0b8491922fd3e69030235f

You can test again with this commit.

Thanks
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