Re: [PATCH net-next v3 4/5] net/ipv6: set expires in modify_prefix_route() if RTF_EXPIRES is set.

[Kui-Feng Lee <sinquersw@gmail.com>]

On 2/2/24 04:16, Hangbin Liu wrote:
> On Fri, Feb 02, 2024 at 12:21:59AM -0800, thinker.li@gmail.com wrote:
>> From: Kui-Feng Lee <thinker.li@gmail.com>
>>
>> Make the decision to set or clean the expires of a route based on the
>> RTF_EXPIRES flag, rather than the value of the "expires" argument.
>>
>> The function inet6_addr_modify() is the only caller of
>> modify_prefix_route(), and it passes the RTF_EXPIRES flag and an expiration
>> value. The RTF_EXPIRES flag is turned on or off based on the value of
>> valid_lft. The RTF_EXPIRES flag is turned on if valid_lft is a finite value
>> (not infinite, not 0xffffffff). Even if valid_lft is 0, the RTF_EXPIRES
>> flag remains on. The expiration value being passed is equal to the
>> valid_lft value if the flag is on. However, if the valid_lft value is
>> infinite, the expiration value becomes 0 and the RTF_EXPIRES flag is turned
>> off. Despite this, modify_prefix_route() decides to set the expiration
>> value if the received expiration value is not zero. This mixing of infinite
>> and zero cases creates an inconsistency.
>>
>> Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
>> ---
>>   net/ipv6/addrconf.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
>> index 36bfa987c314..2f6cf6314646 100644
>> --- a/net/ipv6/addrconf.c
>> +++ b/net/ipv6/addrconf.c
>> @@ -4788,7 +4788,7 @@ static int modify_prefix_route(struct inet6_ifaddr *ifp,
>>   	} else {
>>   		table = f6i->fib6_table;
>>   		spin_lock_bh(&table->tb6_lock);
>> -		if (!expires) {
>> +		if (!(flags & RTF_EXPIRES)) {
> 
> Hi Kui-Feng,
> 
> I may missed something. But I still could not get why we shouldn't use
> expires for checking? If expires == 0, but RTF_EXPIRES is on,
> shouldn't we call fib6_clean_expires()?


The case that expires == 0 and RTF_EXPIES is on never happens since
inet6_addr_modify() rejects valid_lft == 0 at the beginning. This
patch doesn't make difference logically, but make inet6_addr_modify()
and modify_prefix_route() consistent.

Does that make sense to you?


> 
> Thanks
> Hangbin
>>   			fib6_clean_expires(f6i);
>>   			fib6_remove_gc_list(f6i);
>>   		} else {
>> -- 
>> 2.34.1
>>