netdev - Re: Netxen packet loss with VLANs and LRO (was: [PATCH] netxen: fix LRO disable warning)

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Date:	Tue, 5 Apr 2011 14:41:58 +0200
From:	Marc Haber <mh+netdev@...schlus.de>
To:	Amit Salecha <amit.salecha@...gic.com>
Cc:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Ameen Rahman <ameen.rahman@...gic.com>,
	Rajesh Borundia <rajesh.borundia@...gic.com>
Subject: Re: Netxen packet loss with VLANs and LRO (was: [PATCH] netxen:
	fix LRO disable warning)

On Tue, Apr 05, 2011 at 12:38:11AM -0500, Amit Salecha wrote:
> > On Mon, Mar 21, 2011 at 03:37:08AM -0700, Amit Kumar Salecha wrote:
> > > netxen_nic_set_flags() rejects data if other flag than ETH_FLAG_LRO
> > is set.
> > > Driver also supports NETIF_F_HW_VLAN_TX.
> > > Now compare data with ethtool_op_get_flags(), to get all supported
> > features.
> >
> > Could that be the cause for packet loss on kernel 2.6.38.2 if:
> >
> >   - receiving card is NX3031 [4040:0100]
> >   - frames are received with VLAN tags
> >   - large received offload is on.
> 
> If ip_forwarding or routing is enable ....then you may see packet loss.

The box is intended to route, so disabling routing is
contraproductive. I just would like to download software updates to
the box with decent speed as well.

> > Packet Loss of this kind is noticed when doing TCP data transfers
> > towards the host with the Netxen Interface and the TCP session is
> > terminated on the Netxen host itself. TCP sessions routed through the
> > Netxen host are not affected.
> >
> > My ethtool doesn't allow me to influence the LRO setting alone - it is
> > disabled when I set rx off but doesn't come on again when rx is set to
> > on again. So, ethtool -K rx off, ethtool -K rx on fixes the issue.
> >
> If rx csum is disabled, LRO will be disable. LRO won't be enabled automatically if you enable rx csum.
> You need to explicitly enable LRO.

Explicitly enabling LRO does not work ("invalid argument", if I recall
correctly).

> > Is this a known bug, maybe with an available patch?
> >
> You need to retest with this patch
> http://patchwork.ozlabs.org/patch/88060/. This patch got applied
> instead of mine.

Will that patch fix the behavior of the interface regarding the packet
loss, or only its connection to ethtool?

Greetings
Marc

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