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

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Date:	Mon, 23 Jul 2012 16:05:42 +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 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.
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