16 Jul
2007
16 Jul
'07
10:53 a.m.
On Monday 16 July 2007 14:04:31 Greger V. Teigre wrote:
Ok, let me try to take a step back. This discussion is
an example of why
ser.cfg sometimes seems like black magic for most users. It's very
complicated to get a generic config that works in most scenarios. What
we really need to make sure is that people can use the recommended black
magic in most cases, that it is intuitive how to add their own stuff,
and that we make it difficult to "break".. phew...
What would a "normal" user like to know in ser.cfg?
1. Do I need to process like an INVITE or do I t_relay?
2. How do I open or prevent relaying?
Ex. I am sure quite a lot of configs will let an INVITE with a
pre-loaded Route go through without authentication...
Which is not an issue as long as the RURI points to you. Because then you
simply route the request to yourself with no Route header any more, and then
it should be processed like a request without pre-loaded Route.
I still feel that preloaded_route() and in_dialog()
would be simpler to
understand for most people.
Just to state it clearly: the names of these two function can not be
implemented technically correct! Thus I would vote at least against the
names.
If you use has_to_tag(), fine you should know what you are doing. But
in_dialog() without being dialog statefull promisses to much.
I agree with Martin that maybe having a
separate function checking/removing/failing a pre-loaded route is
cleaner than letting loose_route() do it.
Ok. I'm still trying to evaluate if this is possible or not. See below for
more details. But we are talking here about > 2.0 any way, right?
The problem of "non-2xx ACK with a preloaded
route looks exactly the
same then a 2xx ACK" is a corner-case, and I don't see any solution
either, than the suggest uri param in the rr.
Just to make it clear to everybody: this "corner case" occurs in all setups
with a stateless load balancer and where the INVITE gets challenged!
So, could we
automaticlly add the rr param if and only if the original INVITE is
forwarded statelessly?
I don't think so, because the rr module has no idea when you call
record_route() how the request is going to be tramsitted.
I would prefer to have a general option for adding (or not adding) such a
Route cookie. The only question would be then, what should be the default
setting for this option.
The above functions could thus look for the rr param
to detect the
corner-case and thus behave consistently.
g-)
Martin Hoffmann wrote:
> Nils Ohlmeier wrote:
>> On Friday 13 July 2007 14:12:52 Martin Hoffmann wrote:
[...]
>> Sure, they are. But I currently do not really
see any option for this
>> problem.
>
> Possibly, the problem is that loose_route() is trying to be smart. Maybe
> it should be split in two. One function removes the topmost Route if
> present and pointing to this proxy (it can return false if the Route is
> all wrong and we can reply 4xx then), another one that allows to check
> if there is a Route left. The rest is done in config.
>
> Without reading 3261 again, I think this can be done in a way compatible
> with strict routing.
Yes probably it could. The only problem with this approach is that you need to
store some state between the calls of these two functions.
And I guess it should be allowed to call e.g. functions from the select
framework in between. I'm assuming for example that would simply check with
the select framework if their are still route headers present after you
called the "remove topmost route" function, to see if it is necessary to call
the second route function. This would mean that the changes of the
first "remove topmost route" function would have to be applied to the
message. And you hopefully know that this is not easily possible in SER.
Don't get me wrong. The approach sounds interesting. But currently the
implementation looks tricky to me.
Nils