Subject: Re: PATCH: ipv6: avoid wraparound for expired lifetimes

From: Wei Yongjun <[email-masked]>
Date: Thu, 25 Jun 2009 17:25:17 +0800

Jens Rosenboom wrote:
> On Thu, Jun 25, 2009 at 11:40:19AM +0300, Ilpo Järvinen wrote:
>   
>> On Thu, 25 Jun 2009, Jens Rosenboom wrote:
>>
>>     
>>> If the valid or preferred lifetime for an address expires, the kernel
>>> shows huge values for these due to a counter wrap,
>>>       
>> I suspect we have plenty of potentially counter-wrapped printouts all 
>> around the kernel. So you're fixing just a tip of the iceberg.
>>     
>
> So are you implying that because I don't fix all of them at once, I
> shouldn't bother to start at all?
>
> On Thu, 2009-06-25 at 01:42 -0700, David Miller wrote:
> ...
>   
>> Jens, don't even bother posting patches that fail to
>> build.
>>     
>
> Sorry for that, here is the correct version.
>
> --- linux-2.6.30.orig/net/ipv6/addrconf.c	2009-06-10 05:05:27.000000000 +0200
> +++ linux-2.6.30/net/ipv6/addrconf.c	2009-06-25 10:52:27.000000000 +0200
> @@ -3361,9 +3361,18 @@
>  		valid = ifa->valid_lft;
>  		if (preferred != INFINITY_LIFE_TIME) {
>  			long tval = (jiffies - ifa->tstamp)/HZ;
> -			preferred -= tval;
> -			if (valid != INFINITY_LIFE_TIME)
> -				valid -= tval;
> +			if (preferred > tval) {
> +				preferred -= tval;
> +			} else {
> +				preferred = 0;
> +			}
> +			if (valid != INFINITY_LIFE_TIME) {
> +				if (valid > tval) {
> +					valid -= tval;
> +				} else {
> +					valid = 0;
> +				}
> +			}
>  		}
>  	} else {
>  		preferred = INFINITY_LIFE_TIME;
>
>   

checkpatch tell me the following errors:

# ./scripts/checkpatch.pl /root/PATCH\ \ ipv6\ \ avoid\ wraparound\ for\ expired\ lifetimes.eml

WARNING: braces {} are not necessary for any arm of this statement
#90: FILE: net/ipv6/addrconf.c:3364:
+                       if (preferred > tval) {
[...]
+                       } else {
[...]

ERROR: spaces required around that '-=' (ctx:WxV)
#91: FILE: net/ipv6/addrconf.c:3365:
+                               preferred -=3D tval;
                                          ^

ERROR: spaces required around that '=' (ctx:WxV)
#93: FILE: net/ipv6/addrconf.c:3367:
+                               preferred =3D 0;
                                          ^

ERROR: spaces required around that '!=' (ctx:WxV)
#95: FILE: net/ipv6/addrconf.c:3369:
+                       if (valid !=3D INFINITY_LIFE_TIME) {
                                  ^

ERROR: spaces required around that '-=' (ctx:WxV)
#97: FILE: net/ipv6/addrconf.c:3371:
+                                       valid -=3D tval;
                                              ^

ERROR: spaces required around that '=' (ctx:WxV)
#99: FILE: net/ipv6/addrconf.c:3373:
+                                       valid =3D 0;
                                              ^

ERROR: Missing Signed-off-by: line(s)

total: 6 errors, 1 warnings, 21 lines checked

/root/PATCH  ipv6  avoid wraparound for expired lifetimes.eml has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.

> And to show you where this appears:
>
> Output with plain 2.6.30
>
> # ip -6 addr show dev eth0
> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
>     inet6 2001:db8::202:a5ff:fee8:20be/64 scope global dynamic 
>        valid_lft 870sec preferred_lft 7sec
>     inet6 fe80::202:a5ff:fee8:20be/64 scope link 
>        valid_lft forever preferred_lft forever
> # sleep 30
> # ip -6 addr show dev eth0
> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
>     inet6 2001:db8::202:a5ff:fee8:20be/64 scope global deprecated dynamic 
>        valid_lft 840sec preferred_lft 4294967266sec
>     inet6 fe80::202:a5ff:fee8:20be/64 scope link 
>        valid_lft forever preferred_lft forever
>
> Output with patched 2.6.30
>
> # ip -6 addr show dev eth0
> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
>     inet6 2001:db8::202:a5ff:fee8:12e1/64 scope global dynamic 
>        valid_lft 897sec preferred_lft 27sec
>     inet6 fe80::202:a5ff:fee8:12e1/64 scope link 
>        valid_lft forever preferred_lft forever
> # sleep 30
> # ip -6 addr show dev eth0
> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
>     inet6 2001:db8::202:a5ff:fee8:12e1/64 scope global deprecated dynamic 
>        valid_lft 862sec preferred_lft 0sec
>     inet6 fe80::202:a5ff:fee8:12e1/64 scope link 
>        valid_lft forever preferred_lft forever
>
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