IP_RECVTOS

[Philip Prindeville]

On 6/6/12 11:54 AM, Michael Tuexen wrote:
> On Jun 6, 2012, at 7:17 PM, Adrian Chadd wrote:
> 
>> Hi,
>>
>> For TCP, I've seen the network layer change things (eg setting bits on
>> incoming traffic to mark which interface it came in on), so you can't
>> guarantee the outbound ToS == inbound ToS.
> I've not said that inbound == outbound... I just wanted to make clear
> that there is a socket option of setting the TOS byte for outgoing
> traffic. The TCP stack might overwrite the ECN bits...
> 
> I need the IP_RECVTOS functionality for implementing a transport stack supporting
> ECN in userland, actually running the SCTP kernel sources (with some glue code)
> in userland on top of UDP...
> 
> Best regards
> Michael

What about UDT? Can you patch that as well?

For certain services (like backups or AFP), it might be useful for a server to be able to detect a QoS-friendly client and reciprocate in kind.

-Philip