Re: [RFC] Add support for changing the flow ID of TCP connections

On 07/08/14 21:17, Navdeep Parhar wrote:
> On 07/08/14 10:46, Hans Petter Selasky wrote:
>> Hi,
>>
>> I'm working on a new feature which will allow TCP connections to be
>> timing controlled by the ethernet hardware driver, actually the mlxen
>> driver. The main missing piece in the kernel is to allow the mbuf's
>> flowid value to be overwritten in "struct inpcb" once the connection is
>> established and to have a callback once the TCP connection is gone so
>> that the assigned "flowid" can be freed by the ethernet hardware driver.
>>
>> The "flowid" will be used to assign the outgoing data traffic of a
>> specific TCP connections to a hardware controlled queue, which in
>> advance contain certain parameters about the timing for the transmitted
>> packets.
>>
>> To be able to set the flowid I'm using existing functions in the kernel
>> TCP code to lookup the "inpcb" structure based on the 4-tuple, via the
>> "ifp->if_ioctl()" callback of the network adapter. I'm also registering
>> a function method table so that I get a callback when the TCP connection
>> is gone.
>>
>> A this point of development I would like to get some feedback from
>> FreeBSD network guys about my attached patch proposal.
>>
>> The motivation for this work is to have a more reliable TCP
>> transmissions typically for fixed-rate media content going some
>> distance. To illustrate this I will give you an example from the world
>> of VoIP, which is using UDP. When doing long-distance VoIP calls through
>> various unknown networks and routers it makes a very big difference if
>> you are sending data 20ms apart or 40ms apart, even at the exact same
>> rate. In the one case you might experience a bunch of packet drops, and
>> in the other case, everything is fine. Why? Because the number of
>> packets you send per second, and the timing is important. The goal is to
>> apply some timing rules for TCP, to increase the factor of successful
>> transmission, and to reduce the amount of data loss. For high throughput
>> applications we want to do this by means of hardware.
>>
>>
>> While at it I would like to "typedef" the flowid used by mbufs, "struct
>> inpcb" and many more places.  Where would the right place be to put such
>> a definition? In "sys/mbuf.h"?
>>
>>
>> Comments are appreciated!
>
> I think we need to design this to be as generic as possible.  I have
> quite a bit of code that does this stuff but I haven't pushed it
> upstream or even offered it for review (yet).
>

Hi,

When will the non hardware related patches be available for review? I 
understand there are multiple ways to reach the same goal, and I think 
it would be great if we could agree on a common API for applications.

--HPS