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

On 2013年07月02日 22:29, Vlad Yasevich wrote:

On 07/02/2013 02:39 AM, Fan Du wrote:

quoted

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 <redacted>
---
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?

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

quoted

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;
}

-- 
浮沉随浪只记今朝笑

--fan