Subject: Re: [PATCH] sctp: check dst validity after IPsec operations

From: Nicolas Dichtel <[email-masked]>
Date: Thu, 06 Sep 2012 18:40:57 +0200

Le 06/09/2012 18:04, Vlad Yasevich a écrit :
> On 09/06/2012 01:40 PM, Nicolas Dichtel wrote:
>> dst stored in struct sctp_transport needs to be recalculated when ipsec policy
>> are updated. We use flow_cache_genid for that.
>>
>> For example, if a SCTP connection is established and then an IPsec policy is
>> set, the old SCTP flow will not be updated and thus will not use the new
>> IPsec policy.
>>
>> Signed-off-by: Nicolas Dichtel <[email-masked]>
>
> why doesn't this need to be done for TCP?  What makes SCTP special in this case?
Tests prove that the pb does not exist with TCP. I made the patch some times 
ago, I will look again deeply to find the difference.

>
> ip_queue_xmit does an __sk_dst_check() which is essentially what
> sctp_transport_dst_check() does.  That should determine if the currently cached
> route is valid or not.
The problem is that route will not be invalidated, because dst->check() has no 
xfrm path so xfrm_dst_check() will never be called.

Regards,
Nicolas

>
> Looks like sctp may need to change to using ip_route_output_ports() call
> as ip_route_output_key may not do all that is necessary
>
> -vlad
>
>> ---
>>   include/net/sctp/sctp.h    | 3 ++-
>>   include/net/sctp/structs.h | 3 +++
>>   net/sctp/ipv6.c            | 1 +
>>   net/sctp/protocol.c        | 1 +
>>   4 files changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
>> index 9c6414f..3267246 100644
>> --- a/include/net/sctp/sctp.h
>> +++ b/include/net/sctp/sctp.h
>> @@ -712,7 +712,8 @@ static inline void sctp_v4_map_v6(union sctp_addr *addr)
>>    */
>>   static inline struct dst_entry *sctp_transport_dst_check(struct
>> sctp_transport *t)
>>   {
>> -    if (t->dst && !dst_check(t->dst, 0)) {
>> +    if ((t->dst && !dst_check(t->dst, 0)) ||
>> +        (t->flow_cache_genid != atomic_read(&flow_cache_genid))) {
>>           dst_release(t->dst);
>>           t->dst = NULL;
>>       }
>> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
>> index 0fef00f..9dab882 100644
>> --- a/include/net/sctp/structs.h
>> +++ b/include/net/sctp/structs.h
>> @@ -948,6 +948,9 @@ struct sctp_transport {
>>
>>       /* 64-bit random number sent with heartbeat. */
>>       __u64 hb_nonce;
>> +
>> +    /* used to check validity of dst */
>> +    __u32 flow_cache_genid;
>>   };
>>
>>   struct sctp_transport *sctp_transport_new(struct net *, const union
>> sctp_addr *,
>> diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
>> index ea14cb4..2ed7410 100644
>> --- a/net/sctp/ipv6.c
>> +++ b/net/sctp/ipv6.c
>> @@ -349,6 +349,7 @@ out:
>>           struct rt6_info *rt;
>>           rt = (struct rt6_info *)dst;
>>           t->dst = dst;
>> +        t->flow_cache_genid = atomic_read(&flow_cache_genid);
>>           SCTP_DEBUG_PRINTK("rt6_dst:%pI6 rt6_src:%pI6\n",
>>               &rt->rt6i_dst.addr, &fl6->saddr);
>>       } else {
>> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
>> index 2d51842..4795a1a 100644
>> --- a/net/sctp/protocol.c
>> +++ b/net/sctp/protocol.c
>> @@ -512,6 +512,7 @@ out_unlock:
>>       rcu_read_unlock();
>>   out:
>>       t->dst = dst;
>> +    t->flow_cache_genid = atomic_read(&flow_cache_genid);
>>       if (dst)
>>           SCTP_DEBUG_PRINTK("rt_dst:%pI4, rt_src:%pI4\n",
>>                     &fl4->daddr, &fl4->saddr);
>>
>