netdev - [net][PATCH 5/5] rds: avoid version downgrade to legitimate newer peer connections

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Date:   Tue,  9 Jul 2019 22:32:44 -0700
From:   Santosh Shilimkar <santosh.shilimkar@...cle.com>
To:     netdev@...r.kernel.org, davem@...emloft.net
Cc:     santosh.shilimkar@...cle.com
Subject: [net][PATCH 5/5] 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@...cle.com>
Tested-by: Yanjun Zhu <yanjun.zhu@...cle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>
---
 net/rds/rdma_transport.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/rds/rdma_transport.c b/net/rds/rdma_transport.c
index 9db455d..ff74c4b 100644
--- 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",
-- 
1.9.1