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Subject: [PATCH RFC] svcrdma: Ignore source port when computing DRC hash
From:   Chuck Lever <chuck.lever@oracle.com>
To:     linux-rdma@vger.kernel.org, linux-nfs@vger.kernel.org
Date:   Wed, 05 Jun 2019 08:15:18 -0400
Message-ID: <20190605121518.2150.26479.stgit@klimt.1015granger.net>
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The DRC is not working at all after an RPC/RDMA transport reconnect.
The problem is that the new connection uses a different source port,
which defeats DRC hash.

An NFS/RDMA client's source port is meaningless for RDMA transports.
The transport layer typically sets the source port value on the
connection to a random ephemeral port. The server already ignores it
for the "secure port" check. See commit 16e4d93f6de7 ("NFSD: Ignore
client's source port on RDMA transports").

I'm not sure why I never noticed this before.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org
---
 net/sunrpc/xprtrdma/svc_rdma_transport.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 027a3b0..1b3700b 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -211,9 +211,14 @@ static void handle_connect_req(struct rdma_cm_id *new_cma_id,
 	/* Save client advertised inbound read limit for use later in accept. */
 	newxprt->sc_ord = param->initiator_depth;
 
-	/* Set the local and remote addresses in the transport */
 	sa = (struct sockaddr *)&newxprt->sc_cm_id->route.addr.dst_addr;
 	svc_xprt_set_remote(&newxprt->sc_xprt, sa, svc_addr_len(sa));
+	/* The remote port is arbitrary and not under the control of the
+	 * ULP. Set it to a fixed value so that the DRC continues to work
+	 * after a reconnect.
+	 */
+	rpc_set_port((struct sockaddr *)&newxprt->sc_xprt.xpt_remote, 0);
+
 	sa = (struct sockaddr *)&newxprt->sc_cm_id->route.addr.src_addr;
 	svc_xprt_set_local(&newxprt->sc_xprt, sa, svc_addr_len(sa));