[SCTP]: extend exported data in /proc/net/sctp/assoc

RFC 3873 specifies several MIB objects that can't be obtained by the
current data set exported by /proc/sys/net/sctp/assoc.  This patch
adds the missing pieces of data that allow us to compute all the
objects in the sctpAssocTable object.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index f2ed647..ade0cbd 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -5312,6 +5312,8 @@
 	SCTP_DEBUG_PRINTK("Timer T2 expired.\n");
 	SCTP_INC_STATS(SCTP_MIB_T2_SHUTDOWN_EXPIREDS);
 
+	((struct sctp_association *)asoc)->shutdown_retries++;
+
 	if (asoc->overall_error_count >= asoc->max_retrans) {
 		sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
 				SCTP_ERROR(ETIMEDOUT));