netdev - Re: [RFC PATCH] sctp: Don't lookup dst if transport dst is still valid

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Date:	Wed, 03 Jul 2013 09:23:03 -0400
From:	Vlad Yasevich <vyasevich@...il.com>
To:	Fan Du <fan.du@...driver.com>
CC:	nhorman@...driver.com, nicolas.dichtel@...nd.com,
	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [RFC PATCH] sctp: Don't lookup dst if transport dst is still
 valid

On 07/02/2013 10:18 PM, Fan Du wrote:
>
>
> On 2013年07月02日 22:29, Vlad Yasevich wrote:
>> On 07/02/2013 02:39 AM, Fan Du wrote:
>>> When sctp sits on IPv6, sctp_transport_dst_check pass cookie as ZERO,
>>> as a result ip6_dst_check always fail out. This behaviour makes
>>> transport->dst useless, because every sctp_packet_transmit must look
>>> for valid dst(Is this what supposed to be?)
>>>
>>> One aggressive way is to call rt_genid_bump which invalid all dst to
>>> make new dst for transport, apparently it also hurts others.
>>> I'm sure this may not be the best for all, so any commnets?
>>>
>>> Signed-off-by: Fan Du <fan.du@...driver.com>
>>> ---
>>> include/net/sctp/sctp.h | 18 ++++++++++++------
>>> net/sctp/ipv6.c | 2 ++
>>> 2 files changed, 14 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
>>> index cd89510..f05af01 100644
>>> --- a/include/net/sctp/sctp.h
>>> +++ b/include/net/sctp/sctp.h
>>> @@ -719,14 +719,20 @@ static inline void sctp_v4_map_v6(union
>>> sctp_addr *addr)
>>> addr->v6.sin6_addr.s6_addr32[2] = htonl(0x0000ffff);
>>> }
>>>
>>> -/* The cookie is always 0 since this is how it's used in the
>>> - * pmtu code.
>>> - */
>>> +/* Set cookie with the right one for IPv6 and zero for others */
>>> static inline struct dst_entry *sctp_transport_dst_check(struct
>>> sctp_transport *t)
>>> {
>>> - if (t->dst && !dst_check(t->dst, 0)) {
>>> - dst_release(t->dst);
>>> - t->dst = NULL;
>>> +
>>> + if (t->dst) {
>>> + struct rt6_info *rt = (struct rt6_info *)t->dst;
>>> + u32 cookie = 0;
>>> +
>>> + if ((t->af_specific->sa_family == AF_INET6) && rt->rt6i_node)
>>> + cookie = rt->rt6i_node->fn_sernum;
>>> + if (!dst_check(t->dst, cookie)) {
>>> + dst_release(t->dst);
>>> + t->dst = NULL;
>>> + }
>>> }
>>
>> I think it would be better if we stored the dst_cookie in the
>> transport structure and initialized it at lookup time. If you do that,
>> then if the route table changes, we'd correctly detect it without
>> artificially bumping rt_genid (and hurting ipv4).
>
> Hi Vlad/Neil
>
> Is this what you mean?

Yes, exactly.

-vlad

>
> diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
> index cd89510..0a646a5 100644
> --- a/include/net/sctp/sctp.h
> +++ b/include/net/sctp/sctp.h
> @@ -724,7 +724,7 @@ 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, t->dst_cookie)) {
>                  dst_release(t->dst);
>                  t->dst = NULL;
>          }
> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> index 1bd4c41..cafdd19 100644
> --- a/include/net/sctp/structs.h
> +++ b/include/net/sctp/structs.h
> @@ -946,6 +946,8 @@ struct sctp_transport {
>          __u64 hb_nonce;
>
>          struct rcu_head rcu;
> +
> +       u32 dst_cookie;
>   };
>
>   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 8ee553b..82a420f 100644
> --- a/net/sctp/ipv6.c
> +++ b/net/sctp/ipv6.c
> @@ -350,6 +350,7 @@ out:
>                  struct rt6_info *rt;
>                  rt = (struct rt6_info *)dst;
>                  t->dst = dst;
> +               t->dst_cookie = rt->rt6i_node ? rt->rt6i_node->fn_sernum
> : 0;
>                  SCTP_DEBUG_PRINTK("rt6_dst:%pI6 rt6_src:%pI6\n",
>                          &rt->rt6i_dst.addr, &fl6->saddr);
>          } else {
>
>
>
>
>
>> -vlad
>>
>>>
>>> return t->dst;
>>> diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
>>> index 8ee553b..cfae77e 100644
>>> --- a/net/sctp/ipv6.c
>>> +++ b/net/sctp/ipv6.c
>>> @@ -137,6 +137,8 @@ static int sctp_inet6addr_event(struct
>>> notifier_block *this, unsigned long ev,
>>> break;
>>> }
>>>
>>> + /* invalid all transport dst forcing to look up new dst */
>>> + rt_genid_bump(net);
>>> return NOTIFY_DONE;
>>> }
>>>
>>>
>>
>>
>

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