[ofa-general] OFED-1.3beta IPoIB testing questions

[Eli Cohen]

On Fri, 2007-11-30 at 15:28 -0800, Shirley Ma wrote:
> I just touch tested ofed-1.3 beta IPoIB. And found there was a kernel 
> parameter hw_csum being added in IPoIB. I have several questions here:
> 1. Why not using ethtool to set up these HW_CSUM flags?
There is no adequate interface in Ethtool for doing it so we use a
module parameter. This is because we see this as a static configuration
per host.

> 2. I haven't looked at the detailed code yet, is that possible with this 
> flag, TCP/IP will not do CSUM for HCA which has no TCP/IP offload support? 
Yes, the HCA need not have checksum offload support. the idea is the IB
ICRC provides the insurance that the packets are not corrupt.

> If so, then these packets should be limited to be IB network. Routing to 
> ethernet network, the packets would be dropped. If not, I tested IPoIB-UD, 
> why I saw 30% improvement with hw_csum set in none connectX mthca SDR 
> environment?
> 3. I saw switching between IPoIB-cm and IPoIB-ud corrupted interface IP 
> address (unicast address, subnet mask, broadcast address. Anybody saw the 
> same problem?
I did not notice this but it happened to me a few times that when I
wanted to change the mtu and forgot to specify "mtu" in if config, then
ifconfig interpreted the mtu as the IP address and ended up in a wrong
IP address.

> 
> Thanks
> Shirley
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