[Openib-windows] Added ability to change IPoIB mtu size

[Alex Estrin]

Hi Yossi,

This patch would allow IPoIB to run even if for any reason
payload mtu parameter is missing.
Please review.

Thanks,
Alex

Index: ipoib_driver.c
===================================================================
--- ipoib_driver.c	(revision 552)
+++ ipoib_driver.c	(working copy)
@@ -533,9 +533,13 @@
 	{
 		IPOIB_PRINT_EXIT( TRACE_LEVEL_ERROR, IPOIB_DBG_ERROR,
 			("PayloadMtu parameter missing. Use the default.\n") );
-		return status;
+		p_adapter->params.payload_mtu = MAX_PAYLOAD_MTU;
+		status = NDIS_STATUS_SUCCESS;
 	}
-	p_adapter->params.payload_mtu = p_param->ParameterData.IntegerData;
+	else
+	{
+		p_adapter->params.payload_mtu = p_param->ParameterData.IntegerData;
+	}
 	p_adapter->params.xfer_block_size = (sizeof(eth_hdr_t) + p_adapter->params.payload_mtu);
 	NdisReadNetworkAddress( &status, &mac, &len, h_config );

> -----Original Message-----
> From: openib-windows-bounces at openib.org
> [mailto:openib-windows-bounces at openib.org]On Behalf Of Yossi Leybovich
> Sent: Wednesday, November 22, 2006 3:29 AM
> To: Fabian Tillier; Anatoly Lisenko
> Cc: openib-windows at openib.org
> Subject: Re: [Openib-windows] Added ability to change IPoIB mtu size
> 
> 
>  
> 
> > -----Original Message-----
> > From: Fabian Tillier [mailto:ftillier.sst at gmail.com] 
> > Sent: Wednesday, November 22, 2006 9:13 AM
> > To: Anatoly Lisenko
> > Cc: Yossi Leybovich; openib-windows at openib.org
> > Subject: Re: [Openib-windows] Added ability to change IPoIB mtu size
> > 
> > Hi folks,
> > 
> > On 11/19/06, Anatoly Lisenko <anatolyl at voltaire.com> wrote:
> > >
> > > Hi Yossi,
> > >
> > > This patch add the ability to change MTU size in IPoIB.
> > >
> > > Please review.
> > >
> > > Thanks,
> > >
> > > Anatoly
> > 
> > It would be nice to have an explanation of what problem 
> > patches are trying to solve.  I assume this is done to enable 
> > virtualization over IPoIB, which requires network packets to 
> > be ethernet MTU-sized.
> > 
> > I didn't have a chance to look at the patch, but have these 
> thoughts.
> > Limiting the MTU reported to the OS works fine for outbound 
> > packets, but care must be exercised for inbound packets.
> > 
> > 1. The buffers posted to the receive queue must be the full 
> > 2048 byte IB MTU so that the IPoIB driver can receive any 
> > packets sent to it without hitting a protection error due to 
> > overrunning the receive buffers.
> > 2. If a buffer larger than the configured MTU is received, it 
> > must be reported to the OS somehow.  I don't know what's 
> > required to do this, whether you create a new IP header for 
> > the data beyond the first, or whatnot, but it must be done in 
> > such a way that subsequent packets don't cause issues with 
> > sequence numbers.  This doesn't seem like a simple thing to 
> > do right, let alone in a performant way.
> > 
> Cant we just drop the packets and add that to the statiscs of packet
> discards?
> Wny how I will check that in the code.
> 
> > Cheers,
> > 
> > - Fab
> > 
> 
> _______________________________________________
> openib-windows mailing list
> openib-windows at openib.org
> http://openib.org/mailman/listinfo/openib-windows
> 
> 
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