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From:   Olga Kornievskaia <aglo@umich.edu>
Date:   Wed, 5 Jun 2019 11:57:56 -0400
Message-ID: <CAN-5tyH5r_cq9qYF3E2BaNK1Xr0RLsxQFCOGQqXhGb8Rk2xMXw@mail.gmail.com>
Subject: Re: [PATCH RFC] svcrdma: Ignore source port when computing DRC hash
To:     Chuck Lever <chuck.lever@oracle.com>
Cc:     linux-rdma <linux-rdma@vger.kernel.org>,
        linux-nfs <linux-nfs@vger.kernel.org>
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On Wed, Jun 5, 2019 at 8:15 AM Chuck Lever <chuck.lever@oracle.com> wrote:
>
> 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.

Hi Chuck,

I have a question: is the reason for choosing this fix as oppose to
fixing the client because it's server's responsibility to design a DRC
differently for the NFSoRDMA?

>
> 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));
>
>