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

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Date:	Tue, 2 Jul 2013 11:55:45 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Vlad Yasevich <vyasevich@...il.com>
Cc:	Fan Du <fan.du@...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 Tue, Jul 02, 2013 at 10:29:28AM -0400, 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).
> 
Agreed, thats how we do it for ipv4, IIRC
Neil

> -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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