[PATCH] Fix SCTP failure with ipv6 source address routing

[Paul Gortmaker <paul.gortmaker@windriver.com>]

From: Weixing Shi <Weixing.Shi@windriver.com>

Given the below test case, using source address routing, SCTP
does not work.

Node-A:
  1)ifconfig eth0 inet6 add 2001:1::1/64
  2)ip -6 rule add from 2001:1::1 table 100 pref 100
  3)ip -6 route add 2001:2::1 dev eth0 table 100
  4)sctp_darn -H 2001:1::1 -P 250 -l &

Node-B:
  1)ifconfig eth0 inet6 add 2001:2::1/64
  2)ip -6 rule add from 2001:2::1 table 100 pref 100
  3)ip -6 route add 2001:1::1 dev eth0 table 100
  4)sctp_darn -H 2001:2::1 -P 250 -h 2001:1::1 -p 250 -s

Root cause:
  Node-A and Node-B use source address routing, and in the
  begining, the source address will be NULL.  So SCTP will search
  the routing table by the destination address (because it is using
  the source address routing table), and hence the resulting dst_entry
  will be NULL.

Solution:
  After SCTP gets the correct source address, then we search for
  dst_entry again, and then we will get the correct value.

Signed-off-by: Weixing Shi <Weixing.Shi@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 net/sctp/transport.c |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index be4d63d..b5ae18c 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -295,9 +295,16 @@ void sctp_transport_route(struct sctp_transport *transport,
 
 	if (saddr)
 		memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
-	else
+	else {
 		af->get_saddr(opt, asoc, dst, daddr, &transport->saddr);
-
+		/* When using source address routing, since dst was
+		 * looked up prior to filling in the source address, dst
+		 * needs to be looked up again to get the correct dst
+		 */
+		if (dst)
+			dst_release(dst);
+		dst = af->get_dst(asoc, daddr, &transport->saddr);
+	}
 	transport->dst = dst;
 	if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
 		return;
-- 
1.6.5.2