29 Jun
2011
29 Jun
'11
4:56 a.m.
Hello,
On 6/28/11 3:32 PM, Michael Hirschbichler wrote:
Hi all,
I am currently developing a module for offering overload control support
as proposed in
http://tools.ietf.org/html/draft-ietf-soc-overload-control-02 .
As background: the idea behind draft-ietf-soc-overload-control-02 is,
that the upstream node ads parameters to the own Via-header to signal
the next downstream node its ability to understand overload-control
signalling. In case of overload of the downstream node, this node
downstream node extends the own Via-Header (sent in replies to the
upstream node) with e.g., a droprate.
Well, and the job of the oc-module will be to
1) add "oc" to the Via-headers in requests (ok)
2) parse the Via-Header of the replies for oc-droprates and durations (ok)
3) keep a list of overloaded downstream-hosts, the droprate and the
duration of the droprate (failed - see below)
4) its own droprate and the duration communicated to other upstream
neighbors (failed - see below)
The module "oc" (currently) exports the following commands and params
static cmd_export_t cmds[]={
{"oc_check_enabled", ...
{"oc_check_downstream_overloaded", ...
{"oc_setdroprate", oc_setdroprate, ...
{0,0,0,0,0}
};
static param_export_t params[]={
{"oc_enabled", PARAM_INT,&OC_ENABLED},
{0,0,0}
};
and the rpc-methods
static rpc_export_t rpc_methods[] = {
{"oc.stats",...},
{"oc.set_oc"...},
{"oc.set_oc_duration",...},
{0, 0, 0, 0}
};
Well, and now my problem: Manipulating the own Via-Header is (in my
understanding) a very tricky part: in msg_translator.c the functions
"build_req_buf_from_sip_req()" and "build_res_bug_from_sip_res()"
are
responsible for adding the own Via-Header and its parameters.
When building the response there is no own via, the first via will be
the previous hop in the request path, do you need to update that one as
well?
So, I had
to add a function call to functions inside my oc-module:
oc_via_manipulation() and oc_builder().
And here is the problem: I cannot access the shared memory variables of
the oc-module like oc_duration and oc_droprate when I call the
oc_via_manipulation() and oc_builder()-functions from within
"build_req_buf_from_sip_req()" and "build_res_bug_from_sip_res()".
My
conclusion was, that when calling functions of the oc-module from within
the ser-"core", the shared-memory variables set by rpc_methods, cmds and
params are not accessible.
The shared memory is available in the core, so it should be no problem
to access it. The problem might be how you pass the pointers to the
share memory.
Normally, the core should not call the functions implemented by the
module directly, but via some interface. How do you get the pointers to
your module functions to be executed from the core?
Like an idea right now, we could think about a generic function to add
extra parameters to own via header to be offered by the core and called
from inside modules.
Cheers,
Daniel
Honestly, I have now no idea how to continue and would be happy on every
idea,
br
Michael
--
Daniel-Constantin Mierla -- http://www.asipto.com
http://linkedin.com/in/miconda -- http://twitter.com/miconda