linux-kernel - Re: [PATCH v2 04/13] Connection Manager

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Date:	Tue, 05 Dec 2006 10:47:25 -0600
From:	Steve Wise <swise@...ngridcomputing.com>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
Cc:	Roland Dreier <rdreier@...co.com>, netdev@...r.kernel.org,
	openib-general@...nib.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH  v2 04/13] Connection Manager

On Tue, 2006-12-05 at 19:31 +0300, Evgeniy Polyakov wrote:
> On Tue, Dec 05, 2006 at 10:12:42AM -0600, Steve Wise (swise@...ngridcomputing.com) wrote:
> > Ah.  Data from an offloaded connection cannot leak into the main stack
> > nor vice-verse.  We can take an active RDMA connection establishment as
> > an example if you want:  Once the message is sent to the HW to "setup a
> > TCP connection from addr/port a.b to addr/port c.d", then packets on
> > that connection (that 4-tuple) will always be delivered to the RDMA
> > driver, not the native stack.  If the the packet received after the
> > connection is setup is -not- an MPA reply (in this example), then the
> > connection is aborted.  Once the connection is aborted.  So no leaking
> > can happen.
>  
> And if there were a dataflow between addr/port a.b to addr/port c.d
> already, it will either terminated?
> 
> Considering the following sequence:
> handlers->t3c_handlers->sched()->work_queue->work_handlers()->for
> example CPL_PASS_ACCEPT_REQ->pass_accept_req() - it just parses incoming
> skb and sets port/addr/route and other fields to be used as a base for rdma
> connection. What if it just a usual network packet from kernelspace or 
> userspace with the same payload as should be sent by remote rdma system?
> 

That skb isn't a network packet.  Its a CPL_PASS_ACCEPT_REQ message (see
struct cpl_pass_accept_req in the Ethernet driver t3_cpl.h).  If the
RDMA driver hadn't registered to listen on that addr/port, it would
never get this skb.  Once a connection is established, the MPA messages
(and any TCP payload data) is delivered to the RDMA driver in the form
of skb's containing struct cpl_rx_data.  So these skbs aren't just TCP
packets at all.  They either control messages or TCP payload. Either way
they are encapsulated in CPL message structures.

Does this make sense?



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