Subject: Re: [PATCH 1/2] dst: take into account policy update on check()

From: Vlad Yasevich <[email-masked]>
Date: Fri, 07 Sep 2012 10:51:41 -0400

On 09/07/2012 10:35 AM, Eric Dumazet wrote:
> On Fri, 2012-09-07 at 17:57 +0200, Nicolas Dichtel wrote:
>> When a xfrm policy is inserted or deleted, we must invalidate
>> all dst and recalculate the route.
>>
>> Signed-off-by: Nicolas Dichtel <[email-masked]>
>> ---
>>   include/net/dst.h     | 7 +++++++
>>   net/core/dst.c        | 1 +
>>   net/core/sock.c       | 4 ++--
>>   net/ipv6/ip6_tunnel.c | 3 +--
>>   4 files changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/net/dst.h b/include/net/dst.h
>> index 9a78810..478e55a 100644
>> --- a/include/net/dst.h
>> +++ b/include/net/dst.h
>> @@ -101,6 +101,9 @@ struct dst_entry {
>>   	atomic_t		__refcnt;	/* client references	*/
>>   	int			__use;
>>   	unsigned long		lastuse;
>> +#ifdef CONFIG_XFRM
>> +	u32			flow_cache_genid;
>> +#endif
>>   	union {
>>   		struct dst_entry	*next;
>>   		struct rtable __rcu	*rt_next;
>> @@ -457,6 +460,10 @@ static inline int dst_input(struct sk_buff *skb)
>>
>>   static inline struct dst_entry *dst_check(struct dst_entry *dst, u32 cookie)
>>   {
>> +#ifdef CONFIG_XFRM
>> +	if (dst->flow_cache_genid != atomic_read(&flow_cache_genid))
>> +		return NULL;
>> +#endif
>
> Hmm... cant we reuse rt_genid ?
>
> (When changing flow_cache_genid, change &net->ipv4.rt_genid)
>

I thought of that too, but that requires hacking xfrm to know the 
namespace at the time it changes the flow_cache_genid.  This one seems 
simpler to do.

-vlad