Hi Nikhil,

On Tue, Oct 08, 2019 at 04:09:49PM +0530, Nikhil Agrawal wrote:
> Hi,
> I have a use case where i need http response from haproxy with same
> tos/dscp value as incoming packet.
> I found the set-tos in haproxy but no option to dynamically set the same as
> incoming request.
> Is there any way to do the same in haproxy.

No indeed we do not have this in the other way around. I suggest you
try to experiment a bit with getsockopt(IP_TOS) to see what is
reported. Indeed, I don't know what the kernel will report, if it is
the last known TOS for a connection, the first one seen on the SYN
packet or anything else. If you figure we can get any useful information
then I think it makes sense to slightly modify the set-tos action so
that in addition to taking a numeric value it also accepts an expression.

In this case we could have fc_tos() and bc_tos() to get the TOS field
from either the front or the back connection, and use it in set-tos
to adjust the TOS in responses to the client.

Given that it's not something critical I'm fine with getting this
merged at the last minute before the 2.1 release if needed.


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