On Fri, 2015-09-11 at 12:38 +0100, Russell King - ARM Linux wrote:
> I have a recent Marvell Armada 388 board here which uses the mvneta
> driver. I'm seeing some weird effects with NFS with it acting as a
> client. Unfortunately, the board does not have a functional RTC.
>
> The NFS server is the same NFS server that I've used for years with
> multiple other clients (it's my main NFS server) and it continues to
> support all other clients without any ill effect. The NFS server
> kernel is rather old now, being a 3.x kernel.
>
> The NFS client appears to connect using TCP/IPv6 and initially is
> accessible. Everything appears to work normally, and then the NFS
> server appears to stop responding.
>
> Running tcpdump on the NFS server, and then dumping the captured
> packets
> with tshark (because tcpdump appears not to understand IPv6 SYNs on
> the
> NFS port) shows:
>
> 3 0.030036 armada388 -> n2100 TCP 843→nfs [SYN] Seq=936803106
> Win=28800 Len=0 MSS=1440 SACK_PERM=1 TSval=892366 TSecr=0 WS=128
> 4 0.030409 n2100 -> armada388 TCP nfs→843 [SYN, ACK] Seq=409465870
> Ack=936803107 Win=28560 Len=0 MSS=1440 SACK_PERM=1
> TSval=818169117 TSecr=892366 WS=64
> 5 0.030493 armada388 -> n2100 TCP [TCP Port numbers reused]
> 843→nfs [SYN] Seq=936803633 Win=28800 Len=0 MSS=1440 SACK_PERM=1
> TSval=892366 TSecr=0 WS=128
Yes, this packet looks very wrong. Like two simultaneous connect with
same source port. It is not a retransmit (Seq numbers differ)
> 6 0.030699 n2100 -> armada388 TCP nfs→843 [RST, ACK] Seq=0
> Ack=936803634 Win=0 Len=0
> 7 0.030766 armada388 -> n2100 TCP 843→nfs [RST] Seq=936803107
> Win=0 Len=0
I suspect port reuse in NFS being broken.
Have you tried to apply
commit 099392048cd443349c50310f7fdc96070e40f4e7
Author: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Date: Sat Aug 29 19:11:21 2015 -0700
SUNRPC: Prevent SYN+SYNACK+RST storms
Add a shutdown() call before we release the socket in order to ensure the
reset is sent before we try to reconnect.
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 214ca9dfb14e..7be90bc1a7c2 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -822,6 +822,8 @@ static void xs_reset_transport(struct sock_xprt *transport)
if (atomic_read(&transport->xprt.swapper))
sk_clear_memalloc(sk);
+ kernel_sock_shutdown(sock, SHUT_RDWR);
+
write_lock_bh(&sk->sk_callback_lock);
transport->inet = NULL;
transport->sock = NULL;
--
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