netdev - RE: timer expiry check at icmp.c in ipv6

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Date:	Tue, 17 Jul 2012 07:39:23 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	BALAKUMARAN KANNAN <balakumarank@...aelxsi.co.in>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: timer expiry check at icmp.c in ipv6

On Tue, 2012-07-17 at 05:11 +0000, BALAKUMARAN KANNAN wrote:
> Dear Eric,
>     Can you please explain it into bit further. Actually what I want
> to know is how the preferred lifetime value of a router advertisement
> is processed?, Where it is stored? and while sending the ICMP_REPLY
> how that preferred lifetime value considered before actually sending
> the packet? I cannot able to find the relation between
> icmpv6_echo_reply and fib6_run_gc(). I am very new to kernel source.
> Kindly help me.

# find net/ipv6|xargs grep -n RTF_EXPIRES
net/ipv6/ip6_fib.c:675:				if (!(iter->rt6i_flags & RTF_EXPIRES))
net/ipv6/ip6_fib.c:677:				if (!(rt->rt6i_flags & RTF_EXPIRES))
net/ipv6/ip6_fib.c:740:	    (rt->rt6i_flags & (RTF_EXPIRES | RTF_CACHE)))
net/ipv6/ip6_fib.c:1545:	if (rt->rt6i_flags & RTF_EXPIRES && rt->dst.expires) {
net/ipv6/route.c:307:	if (!(rt->rt6i_flags & RTF_EXPIRES) && dst->from)
net/ipv6/route.c:370:	if (rt->rt6i_flags & RTF_EXPIRES) {
net/ipv6/route.c:375:		return (ort->rt6i_flags & RTF_EXPIRES) &&
net/ipv6/route.c:1397:	if (cfg->fc_flags & RTF_EXPIRES)
net/ipv6/route.c:1908:				  RTF_UP | RTF_EXPIRES | RTF_PREF(pref),
net/ipv6/route.c:2476:	if (!(rt->rt6i_flags & RTF_EXPIRES))
net/ipv6/addrconf.c:805:			} else if (!(rt->rt6i_flags & RTF_EXPIRES)) {
net/ipv6/addrconf.c:1902:				flags |= RTF_EXPIRES;
net/ipv6/addrconf.c:2212:		flags = RTF_EXPIRES;
net/ipv6/addrconf.c:3420:		flags = RTF_EXPIRES;
net/ipv6/ip6_fib.c.orig:675:				if (!(iter->rt6i_flags & RTF_EXPIRES))
net/ipv6/ip6_fib.c.orig:677:				if (!(rt->rt6i_flags & RTF_EXPIRES))
net/ipv6/ip6_fib.c.orig:740:	    (rt->rt6i_flags & (RTF_EXPIRES | RTF_CACHE)))
net/ipv6/ip6_fib.c.orig:1545:	if (rt->rt6i_flags & RTF_EXPIRES && rt->dst.expires) {



What are the expected preferred lifetimes of a router ?

If granularity is one second, the garbage collection done every 30
seconds is not good.

But if its one hour, or one day, having a 30 seconds delay at the end of
the period isnt critical.



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