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Message-Id: <20170508002512.GA6012@gwshan> Date: Mon, 8 May 2017 10:25:12 +1000 From: Gavin Shan <gwshan@...ux.vnet.ibm.com> To: Andrew Lunn <andrew@...n.ch> Cc: Gavin Shan <gwshan@...ux.vnet.ibm.com>, netdev@...r.kernel.org, joe@...ches.com, kubakici@...pl, f.fainelli@...il.com, davem@...emloft.net Subject: Re: [PATCH v4 net-next 08/10] net/ncsi: Support NCSI packet generation On Thu, May 04, 2017 at 02:00:35PM +0200, Andrew Lunn wrote: >On Thu, May 04, 2017 at 04:31:57PM +1000, Gavin Shan wrote: >> On Wed, May 03, 2017 at 02:52:54PM +0200, Andrew Lunn wrote: >> >On Wed, May 03, 2017 at 02:44:39PM +1000, Gavin Shan wrote: >> >> This introduces /sys/kernel/debug/ncsi/eth0/pkt. The debugfs entry >> >> can accept parameters to produce NCSI command packet. The received >> >> NCSI response packet is dumped on read. Below is an example to send >> >> CIS command and dump its response. >> >> >> >> # echo CIS,0,0 > /sys/kernel/debug/ncsi/eth0/pkt >> >> # cat /sys/kernel/debug/ncsi/eth0/pkt >> >> NCSI response [CIS] packet received >> >> >> >> 00 01 dd 80 00 0004 0000 0000 >> > >> >Could this be done with a raw socket for Tx and >> >libpcap/tcpdump/wireshart for Rx? >> > >> >> Andrew, it's really good question. Unfortunately, I don't think it can >> be done solely by raw socket to transmit NCSI command packet because the >> [packet sequence number] field in the packet can't be same to any used ones. >> Otherwise the remote NIC will be confused and start to reponse abnormally. > >Just to make sure i'm on the same page. We are talking about: > >https://www.dmtf.org/sites/default/files/standards/documents/DSP0222_1.0.1.pdf > >and the sequence number is the Instance ID. This is an 8-bit number, >and if it receives a message with the previously used IID, it should >assume it is a re-transmit of the request and send back the old >response. It is a very simple scheme, no windowing, only one >outstanding command/response, just one response buffered in case of a >re-transmit. > >> We could reserve some sequence number to be used by raw socket. > >I don't think that works. You can only have one command >'inflight'. Packets from a raw socket would have to go through your >state machine. Which makes it complex. > >libpcap should however still work. So you should probably do all the >receive side in user space. > Andrew, yeah, we're on same page about the sequence number. Yes, I agree it's going to make thing complex to transmit packet through raw socket. So lets keep using debugfs as we had. I need to dig how libpcap receives packets. It's appreciated if you can give some hints about that. However, I don't see the benefit to receive packets by libpcap, could you claim? Cheers, Gavin
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