rds: avoid version downgrade to legitimate newer peer connections

Connections with legitimate tos values can get into usual connection
race. It can result in consumer reject. We don't want tos value or
protocol version to be demoted for such connections otherwise
piers would end up different tos values which can results in
no connection. Example a peer initiated connection with say
tos 8 while usual connection racing can get downgraded to tos 0
which is not desirable.

Patch fixes above issue introduced by commit
commit d021fabf525f ("rds: rdma: add consumer reject")

Reported-by: Yanjun Zhu <yanjun.zhu@oracle.com>
Tested-by: Yanjun Zhu <yanjun.zhu@oracle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

diff --git a/net/rds/rdma_transport.c b/net/rds/rdma_transport.c
index 9db455d022559fa0a11e31e92ca3b191541afa58..ff74c4bbb9fc883f4107432c11a47f3d6f840137 100644 (file)
--- a/net/rds/rdma_transport.c
+++ b/net/rds/rdma_transport.c
@@ -117,8 +117,10 @@ static int rds_rdma_cm_event_handler_cmn(struct rdma_cm_id *cm_id,
                     ((*err) <= RDS_RDMA_REJ_INCOMPAT))) {
                        pr_warn("RDS/RDMA: conn <%pI6c, %pI6c> rejected, dropping connection\n",
                                &conn->c_laddr, &conn->c_faddr);
-                       conn->c_proposed_version = RDS_PROTOCOL_COMPAT_VERSION;
-                       conn->c_tos = 0;
+
+                       if (!conn->c_tos)
+                               conn->c_proposed_version = RDS_PROTOCOL_COMPAT_VERSION;
+
                        rds_conn_drop(conn);
                }
                rdsdebug("Connection rejected: %s\n",