On Wed, Jun 19, 2019 at 04:25:57PM -0400, Chuck Lever wrote:
>
> > On Jun 11, 2019, at 11:01 AM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
> >
> > The DRC appears to be effectively empty after an RPC/RDMA transport
> > reconnect. The problem is that each connection uses a different
> > source port, which defeats the DRC hash.
> >
> > Clients always have to disconnect before they send retransmissions
> > to reset the connection's credit accounting, thus every retransmit
> > on NFS/RDMA will miss the DRC.
> >
> > An NFS/RDMA client's IP 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").
> >
> > The Linux NFS server's DRC resolves XID collisions from the same
> > source IP address by using the checksum of the first 200 bytes of
> > the RPC call header.
> >
> > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx # v4.14+
> > ---
> > 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..0004535 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
> > + * client ULP. Set it to a fixed value so that the DRC continues
> > + * to be effective 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));
>
> Hi Bruce, what's the disposition of this patch?
I've queued it up locally for 5.2 and stable. Apologies, it got a
little buried in my inbox, thanks for the reminder.
--b.
