ipv6: fix incorrect route 'expires' value passed to userspace.

When userspace use RTM_GETROUTE to dump route table, with a already
expired route entry, we always got an 'expires' value(2147157)
calculated base on INT_MAX.

The reason of this problem is in the following satement:
	rt->dst.expires - jiffies < INT_MAX
gcc promoted the type of both sides of '<' to unsigned long, thus
a small negative value would be considered greater than INT_MAX.

This patch fix this by cast the result of subtraction to an 'int'
which I think is large enough for the expires.

Also we should do some fix in rtnl_put_cacheinfo() which use
jiffies_to_clock_t(which take an unsigned log as parameter) to
convert jiffies to clock_t to handle the negative expires.
---
 net/core/rtnetlink.c |    3 ++-
 net/ipv6/route.c     |    2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

Without a proper signoff, I won't apply your patch.
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On Mon, 16 Jul 2012 16:09:37 +0800
Li Wei <lw@cn.fujitsu.com> wrote:

> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index becb048..a7fec9d 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -2516,7 +2516,7 @@ static int rt6_fill_node(struct net *net,
>  		goto nla_put_failure;
>  	if (!(rt->rt6i_flags & RTF_EXPIRES))
>  		expires = 0;
> -	else if (rt->dst.expires - jiffies < INT_MAX)
> +	else if ((int)(rt->dst.expires - jiffies) < INT_MAX)
>  		expires = rt->dst.expires - jiffies;
>  	else
>  		expires = INT_MAX;

Why not use time_is_after_jiffies() macro?
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于 2012-7-17 0:41, Stephen Hemminger 写道:
> On Mon, 16 Jul 2012 16:09:37 +0800
> Li Wei <lw@cn.fujitsu.com> wrote:
> 
>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
>> index becb048..a7fec9d 100644
>> --- a/net/ipv6/route.c
>> +++ b/net/ipv6/route.c
>> @@ -2516,7 +2516,7 @@ static int rt6_fill_node(struct net *net,
>>  		goto nla_put_failure;
>>  	if (!(rt->rt6i_flags & RTF_EXPIRES))
>>  		expires = 0;
>> -	else if (rt->dst.expires - jiffies < INT_MAX)
>> +	else if ((int)(rt->dst.expires - jiffies) < INT_MAX)
>>  		expires = rt->dst.expires - jiffies;
>>  	else
>>  		expires = INT_MAX;
> 
> Why not use time_is_after_jiffies() macro?

time_is_after_jiffies() return a bool but we need "how much time
before/after jiffies" here.

> 
> 

However, I also think these code seems a little ugly, because we
need to store the result of two "unsigned long"'s subtraction into
an integer. Maybe we should distinguish expires before and after 
jiffies to proper process the overflows.

Thanks,
Wei

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于 2012-7-16 17:56, David Miller 写道:
> 
> Without a proper signoff, I won't apply your patch.
> 
> 

Sorry for that, I will append a signoff, do some code refactor
and send a V2.

Thanks,
Wei

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From: Stephen Hemminger <shemminger@vyatta.com>
Date: Mon, 16 Jul 2012 09:41:24 -0700

> On Mon, 16 Jul 2012 16:09:37 +0800
> Li Wei <lw@cn.fujitsu.com> wrote:
> 
>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
>> index becb048..a7fec9d 100644
>> --- a/net/ipv6/route.c
>> +++ b/net/ipv6/route.c
>> @@ -2516,7 +2516,7 @@ static int rt6_fill_node(struct net *net,
>>  		goto nla_put_failure;
>>  	if (!(rt->rt6i_flags & RTF_EXPIRES))
>>  		expires = 0;
>> -	else if (rt->dst.expires - jiffies < INT_MAX)
>> +	else if ((int)(rt->dst.expires - jiffies) < INT_MAX)
>>  		expires = rt->dst.expires - jiffies;
>>  	else
>>  		expires = INT_MAX;
> 
> Why not use time_is_after_jiffies() macro?

This test has a wider window of acceptance.
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