Re: [PATCH v2] svcrdma: Ignore source port when computing DRC hash

[Chuck Lever <chuck.lever@oracle.com>]

> On Jun 19, 2019, at 4:43 PM, Bruce Fields <bfields@fieldses.org> wrote:
> 
> 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@oracle.com> 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@oracle.com>
>>> Cc: stable@vger.kernel.org # 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.

Great, thank you!


> Apologies, it got a
> little buried in my inbox, thanks for the reminder.
> 
> --b.

--
Chuck Lever