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 00:38:11 -0500
From:	Amit Salecha <amit.salecha@...gic.com>
To:	Marc Haber <mh+netdev@...schlus.de>
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)

>
> Hi,
>
> 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.

> 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.

> 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.


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