Re: [exim-dev] DSCP for inbound connections

On 2012-06-02 at 18:05 -0400, Phil Pennock wrote:
> I'm thinking that the best way to have DSCP set for the packets outbound
> from Exim as a server, when a client connects, is to have a
> "control = dscp/$value"
> option which can be set in the acl_smtp_connect ACL.
>
> Thoughts? Does this seem sane?

Implemented that. Seems to work great. Easier to test than the
outbound too (we, er, won't mention how long I was scratching my head
for, forgetting that SMTP delivery re-execs Exim and that I hadn't set
exim_path in the test config).

> In discussion with a user who wants/needs DSCP, am looks like there's a
> need to be able to reference the DSCP value for inbound connections, so
> something like $received_initial_dscp as a variable.
>
> The _initial_ because theoretically I believe the DSCP/TOS/TCLASS can
> change during a connection, but I don't know if we want to support that
> in an ACL other than the initial one.
>
> Although, I suppose if a user authenticates, we might want to let the
> admin put them into a better traffic class, so perhaps it *should* be
> adjustable from any SMTP ACL ...

Variable: still not quite sure about exposing this, or if perhaps it
should be an expansion item rather than a variable, so that each time
it's expanded the value is fetched. Er, I'm also blanking on how to
*implement* this with a read()-based API, without switching our entire
SMTP read system to a readmsg()-based system, which I'm *very* reluctant
to do for such a minor feature.

ACL: I let this be adjusted from most ACLs, excluding only the non-SMTP
and the notquit.

-Phil