Re: [SR-Users] Can't work around double SDP rewrite issue with rtpengine and config script SDP manipulation

[Daniel-Constantin Mierla]

The loose_route() is marking local Route headers for deletion, so after
the msg_apply_changes() you don't see them. It should work fine if you
do not need to inspect them afterwards, but if you are not sure, it is
recommended do it before.

Cheers,
Daniel

On 02.06.20 09:49, George Diamantopoulos wrote:
> Daniel, that worked instantly, thank you!
>
> Care to elaborate on how msg_apply_changes() interferes with
> loose_route? I also remember msg_apply_changes() complaining if called
> after record_route(), is it related?
>
> On Mon, 1 Jun 2020 at 21:24, Daniel-Constantin Mierla
> mailto:mico...@gmail.com>> wrote:
>
> Hello,
>
> use msg_apply_changes just after replace_body_str(), eventually
> before loose routing processing for requests within dialog.
>
> Cheers,
> Daniel
>
> On 01.06.20 13:34, George Diamantopoulos wrote:
>> Hello all,
>>
>> I'm facing one of those cases where I need to edit the body of a
>> SIP message, which is then to be fed to rtpengine for processing.
>> Although I've taken every precaution I've read about on this list
>> and elsewhere, I can't prevent the edited line from appearing
>> twice in the outgoing message.
>>
>> The configuration file used is huge, so I'm going to try to
>> provide a high-level overview here. But first, the things (I
>> think) I know to be requirements, and which I have striven to meet:
>>
>>   * If SDP is to be edited, then all such processing is to be
>> carried out in such a way in the script, so that
>> msg_apply_changes() is run as many times as needed before
>> rtpengine offer/answer/manage is called.
>>   * rtpengine offer/answer/manage is to be called only once per
>> script iteration
>>   * msg_apply_changes can only be called in a request route, or
>> in the core reply_route (i.e. *not* in tm-managed
>> on_reply_route[XXX] blocks)
>>
>> In my case, additionally the following are true:
>>
>>   * SDP processing (other than the one performed by rtpengine)
>> takes place in one common route for all cases where it needs
>> to happen. These are two at the moment in my scenario:
>>   o Early in the WITHINDLG route (of the example config file)
>>   o After the sanity checks in the reply_route (of the
>> example config file)
>>   * msg_apply changes() is called once, for each script iteration:
>>   o right before rtpengine_manage() is called, provided that
>> t_is_request_route() returns true (so that I don't
>> accidentally call it from a branch route or anything)
>>   + rtpengine_manage() is called in its own route, which
>> is very similar to the example config file's
>> "NATMANAGE" route. Since NATMANAGE is called in all
>> branch and on_reply_routes, I employ
>> t_is_request_route() here to make sure it won't
>> execute in those cases.
>>   o at the end of the "core" reply_route
>>
>> Now regarding the actual config-file-controlled SDP manipulation,
>> it only consists of a single call to replace_body_str(). The
>> purpose is to edit a line in the message body from something like:
>>
>>   * a=fmtp:101 0-16
>>
>> to something along the lines of:
>>
>>   * a=fmtp:101 0-15
>>
>> For replies, this works as expected.
>>
>> For in-dialog requests, however, I end up with both the original
>> and the edited lines:
>> a=fmtp:101 0-16 (the original line)
>> ... other SDP stuff ...
>> a=fmtp:101 0-15 (the edited line)
>>
>> If anyone could point out any misconceptions I have about
>> msg_apply_changes, SDP rewriting from the script and
>> rtp_engine_X() interoperability, I would be more than grateful.
>>
>> Thank you in advance and I apologize for the long read.
>>
>> Best regards,
>> George Diamantopoulos
>>
>> ___
>> Kamailio (SER) - Users Mailing List
>> sr-users@lists.kamailio.org 
>> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
>
> -- 
> Daniel-Constantin Mierla -- www.asipto.com 
> www.twitter.com/miconda  -- 
> www.linkedin.com/in/miconda 
> Funding: https://www.paypal.me/dcmierla
>
-- 
Daniel-Constantin Mierla -- www.asipto.com
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Funding: https://www.paypal.me/dcmierla

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Re: [SR-Users] Can't work around double SDP rewrite issue with rtpengine and config script SDP manipulation

[George Diamantopoulos]

Daniel, that worked instantly, thank you!

Care to elaborate on how msg_apply_changes() interferes with loose_route? I
also remember msg_apply_changes() complaining if called after
record_route(), is it related?

On Mon, 1 Jun 2020 at 21:24, Daniel-Constantin Mierla 
wrote:

> Hello,
>
> use msg_apply_changes just after replace_body_str(), eventually before
> loose routing processing for requests within dialog.
>
> Cheers,
> Daniel
> On 01.06.20 13:34, George Diamantopoulos wrote:
>
> Hello all,
>
> I'm facing one of those cases where I need to edit the body of a SIP
> message, which is then to be fed to rtpengine for processing. Although I've
> taken every precaution I've read about on this list and elsewhere, I can't
> prevent the edited line from appearing twice in the outgoing message.
>
> The configuration file used is huge, so I'm going to try to provide a
> high-level overview here. But first, the things (I think) I know to be
> requirements, and which I have striven to meet:
>
>- If SDP is to be edited, then all such processing is to be carried
>out in such a way in the script, so that msg_apply_changes() is run as many
>times as needed before rtpengine offer/answer/manage is called.
>- rtpengine offer/answer/manage is to be called only once per script
>iteration
>- msg_apply_changes can only be called in a request route, or in the
>core reply_route (i.e. *not* in tm-managed on_reply_route[XXX] blocks)
>
> In my case, additionally the following are true:
>
>- SDP processing (other than the one performed by rtpengine) takes
>place in one common route for all cases where it needs to happen. These are
>two at the moment in my scenario:
>- Early in the WITHINDLG route (of the example config file)
>   - After the sanity checks in the reply_route (of the example config
>   file)
>- msg_apply changes() is called once, for each script iteration:
>   - right before rtpengine_manage() is called, provided that
>   t_is_request_route() returns true (so that I don't accidentally call it
>   from a branch route or anything)
>  - rtpengine_manage() is called in its own route, which is very
>  similar to the example config file's "NATMANAGE" route. Since 
> NATMANAGE is
>  called in all branch and on_reply_routes, I employ 
> t_is_request_route()
>  here to make sure it won't execute in those cases.
>   - at the end of the "core" reply_route
>
> Now regarding the actual config-file-controlled SDP manipulation, it only
> consists of a single call to replace_body_str(). The purpose is to edit a
> line in the message body from something like:
>
>- a=fmtp:101 0-16
>
> to something along the lines of:
>
>- a=fmtp:101 0-15
>
> For replies, this works as expected.
>
> For in-dialog requests, however, I end up with both the original and the
> edited lines:
> a=fmtp:101 0-16 (the original line)
> ... other SDP stuff ...
> a=fmtp:101 0-15 (the edited line)
>
> If anyone could point out any misconceptions I have about
> msg_apply_changes, SDP rewriting from the script and rtp_engine_X()
> interoperability, I would be more than grateful.
>
> Thank you in advance and I apologize for the long read.
>
> Best regards,
> George Diamantopoulos
>
> ___
> Kamailio (SER) - Users Mailing 
> Listsr-users@lists.kamailio.orghttps://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
>
> --
> Daniel-Constantin Mierla -- www.asipto.comwww.twitter.com/miconda -- 
> www.linkedin.com/in/miconda
> Funding: https://www.paypal.me/dcmierla
>
>
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Re: [SR-Users] Can't work around double SDP rewrite issue with rtpengine and config script SDP manipulation

[Alex Balashov]

George,

I understand. Have you considered begrudgingly adding a lightweight B2BUA such 
as SEMS in the middle? 

I understand it greatly increases the operational complexity and moving parts 
of your setup, to say nothing of infrastructural costs. I am all for using 
Kamailio alone to solve problems that the disinformation/spam of the SBC 
industry tells us we need a conventional SBC to solve. I gave a presentation at 
the last Kamailio World[1] whose general tenor was that all one needs is a 
little Kamailio, and which could be interpreted as a winding, circumlocutory 
middle finger to the SBC industry. :-)

But this really does strike me as a valid use-case for an “SBC” type setup as 
we’ve been made to understand the term — that is, in what 
Oracle/Metaswitch/Sansay/Sonus/etc would like to have you think of as “the 
ordinary sense”. 

RTPEngine is minimally invasive and, outside of its mandate to change the media 
endpoint addresses, is designed for additive capabilities, not to fix problems 
or maladaptive behaviours. Meanwhile, tweaking the SDP body, despite the 
existence of extensive technical capability on the part of Kamailio, is not 
something a proxy should be doing; it’s just not faithful to the endpoints’ 
tacit assumption that the SDP offer/answer they send is the one being operated 
upon by the other party. And, as you’ve noted, it is problematic to both tweak 
the SDP body and press RTPEngine into service simultaneously.

There may be — in fact, it’s likely — a solution to your most immediate 
technical problem, though I’m not sure offhand. But for the sake of 
manageability and conceptual integrity to your voice architecture going 
forward, I would urge you to reconsider whether this is the best way of doing 
things overall.

... unless you’re already well past that point, to which I think your 
references to the size and complexity of your config allude. :-) In that case, 
a nihilistic attitude may better suit the dark, ghastly hue of the situation.

— Alex

[1] https://youtu.be/j-0C6eHfocI

—
Sent from mobile, with due apologies for brevity and errors.

> On Jun 1, 2020, at 8:15 AM, George Diamantopoulos  
> wrote:
> 
> 
> Hello Alex,
> 
> Thank you for your reply. Well, I'm interfacing with several PSTN operators, 
> and some of their networks' SIP endpoints (or other obscure IMS entity there) 
> are very picky in that if they don't like the capabilities you serve for 
> telephone-event (which is if they don't match theirs), then the transaction 
> is rejected with "488 SDP Parameter Error In SIP Request" (or if it's a reply 
> I'm sending, they will send a BYE immediately).
> 
> Trying to reason with them (the operators) has failed, my SIP UA provides no 
> way to choose these values when the SDP is created (and since it apparently 
> has to match the other side some static configuration wouldn't do much here), 
> so all I'm left with is the option of growing my config file by yet another 
> 50 lines... :-\
> 
> BR,
> George
> 
>> On Mon, 1 Jun 2020 at 14:41, Alex Balashov  wrote:
>> George,
>> 
>> It may be orthogonal to the answer that you seek, but I’m going to ask 
>> anyway: what is the overall motive underlying your SDP manipulation?
>> 
>> It seems to me that one should reason backward from that root cause. The 
>> kind of SDP manipulation you are doing is seldom necessary in ordinarily 
>> imaginable contexts...
>> 
>> — Alex
>> 
>> —
>> Sent from mobile, with due apologies for brevity and errors.
>> 
 On Jun 1, 2020, at 7:35 AM, George Diamantopoulos  
 wrote:
 
>>> 
>>> Hello all,
>>> 
>>> I'm facing one of those cases where I need to edit the body of a SIP 
>>> message, which is then to be fed to rtpengine for processing. Although I've 
>>> taken every precaution I've read about on this list and elsewhere, I can't 
>>> prevent the edited line from appearing twice in the outgoing message.
>>> 
>>> The configuration file used is huge, so I'm going to try to provide a 
>>> high-level overview here. But first, the things (I think) I know to be 
>>> requirements, and which I have striven to meet:
>>> If SDP is to be edited, then all such processing is to be carried out in 
>>> such a way in the script, so that msg_apply_changes() is run as many times 
>>> as needed before rtpengine offer/answer/manage is called.
>>> rtpengine offer/answer/manage is to be called only once per script iteration
>>> msg_apply_changes can only be called in a request route, or in the core 
>>> reply_route (i.e. not in tm-managed on_reply_route[XXX] blocks)
>>> In my case, additionally the following are true:
>>> SDP processing (other than the one performed by rtpengine) takes place in 
>>> one common route for all cases where it needs to happen. These are two at 
>>> the moment in my scenario:
>>> Early in the WITHINDLG route (of the example config file)
>>> After the sanity checks in the reply_route (of the example config file)
>>> msg_apply changes() is called once, for each script 

Re: [SR-Users] Can't work around double SDP rewrite issue with rtpengine and config script SDP manipulation

[George Diamantopoulos]

Hello Alex,

Thank you for your reply. Well, I'm interfacing with several PSTN
operators, and some of their networks' SIP endpoints (or other obscure IMS
entity there) are very picky in that if they don't like the capabilities
you serve for telephone-event (which is if they don't match theirs), then
the transaction is rejected with "488 SDP Parameter Error In SIP Request"
(or if it's a reply I'm sending, they will send a BYE immediately).

Trying to reason with them (the operators) has failed, my SIP UA provides
no way to choose these values when the SDP is created (and since it
apparently has to match the other side some static configuration wouldn't
do much here), so all I'm left with is the option of growing my config file
by yet another 50 lines... :-\

BR,
George

On Mon, 1 Jun 2020 at 14:41, Alex Balashov 
wrote:

> George,
>
> It may be orthogonal to the answer that you seek, but I’m going to ask
> anyway: what is the overall motive underlying your SDP manipulation?
>
> It seems to me that one should reason backward from that root cause. The
> kind of SDP manipulation you are doing is seldom necessary in ordinarily
> imaginable contexts...
>
> — Alex
>
> —
> Sent from mobile, with due apologies for brevity and errors.
>
> On Jun 1, 2020, at 7:35 AM, George Diamantopoulos 
> wrote:
>
> 
> Hello all,
>
> I'm facing one of those cases where I need to edit the body of a SIP
> message, which is then to be fed to rtpengine for processing. Although I've
> taken every precaution I've read about on this list and elsewhere, I can't
> prevent the edited line from appearing twice in the outgoing message.
>
> The configuration file used is huge, so I'm going to try to provide a
> high-level overview here. But first, the things (I think) I know to be
> requirements, and which I have striven to meet:
>
>- If SDP is to be edited, then all such processing is to be carried
>out in such a way in the script, so that msg_apply_changes() is run as many
>times as needed before rtpengine offer/answer/manage is called.
>- rtpengine offer/answer/manage is to be called only once per script
>iteration
>- msg_apply_changes can only be called in a request route, or in the
>core reply_route (i.e. *not* in tm-managed on_reply_route[XXX] blocks)
>
> In my case, additionally the following are true:
>
>- SDP processing (other than the one performed by rtpengine) takes
>place in one common route for all cases where it needs to happen. These are
>two at the moment in my scenario:
>- Early in the WITHINDLG route (of the example config file)
>   - After the sanity checks in the reply_route (of the example config
>   file)
>- msg_apply changes() is called once, for each script iteration:
>   - right before rtpengine_manage() is called, provided that
>   t_is_request_route() returns true (so that I don't accidentally call it
>   from a branch route or anything)
>  - rtpengine_manage() is called in its own route, which is very
>  similar to the example config file's "NATMANAGE" route. Since 
> NATMANAGE is
>  called in all branch and on_reply_routes, I employ 
> t_is_request_route()
>  here to make sure it won't execute in those cases.
>   - at the end of the "core" reply_route
>
> Now regarding the actual config-file-controlled SDP manipulation, it only
> consists of a single call to replace_body_str(). The purpose is to edit a
> line in the message body from something like:
>
>- a=fmtp:101 0-16
>
> to something along the lines of:
>
>- a=fmtp:101 0-15
>
> For replies, this works as expected.
>
> For in-dialog requests, however, I end up with both the original and the
> edited lines:
> a=fmtp:101 0-16 (the original line)
> ... other SDP stuff ...
> a=fmtp:101 0-15 (the edited line)
>
> If anyone could point out any misconceptions I have about
> msg_apply_changes, SDP rewriting from the script and rtp_engine_X()
> interoperability, I would be more than grateful.
>
> Thank you in advance and I apologize for the long read.
>
> Best regards,
> George Diamantopoulos
> ___
> Kamailio (SER) - Users Mailing List
> sr-users@lists.kamailio.org
> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
>
> ___
> Kamailio (SER) - Users Mailing List
> sr-users@lists.kamailio.org
> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
>
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Re: [SR-Users] Can't work around double SDP rewrite issue with rtpengine and config script SDP manipulation

[Alex Balashov]

George,

It may be orthogonal to the answer that you seek, but I’m going to ask anyway: 
what is the overall motive underlying your SDP manipulation?

It seems to me that one should reason backward from that root cause. The kind 
of SDP manipulation you are doing is seldom necessary in ordinarily imaginable 
contexts...

— Alex

—
Sent from mobile, with due apologies for brevity and errors.

> On Jun 1, 2020, at 7:35 AM, George Diamantopoulos  
> wrote:
> 
> 
> Hello all,
> 
> I'm facing one of those cases where I need to edit the body of a SIP message, 
> which is then to be fed to rtpengine for processing. Although I've taken 
> every precaution I've read about on this list and elsewhere, I can't prevent 
> the edited line from appearing twice in the outgoing message.
> 
> The configuration file used is huge, so I'm going to try to provide a 
> high-level overview here. But first, the things (I think) I know to be 
> requirements, and which I have striven to meet:
> If SDP is to be edited, then all such processing is to be carried out in such 
> a way in the script, so that msg_apply_changes() is run as many times as 
> needed before rtpengine offer/answer/manage is called.
> rtpengine offer/answer/manage is to be called only once per script iteration
> msg_apply_changes can only be called in a request route, or in the core 
> reply_route (i.e. not in tm-managed on_reply_route[XXX] blocks)
> In my case, additionally the following are true:
> SDP processing (other than the one performed by rtpengine) takes place in one 
> common route for all cases where it needs to happen. These are two at the 
> moment in my scenario:
> Early in the WITHINDLG route (of the example config file)
> After the sanity checks in the reply_route (of the example config file)
> msg_apply changes() is called once, for each script iteration:
> right before rtpengine_manage() is called, provided that t_is_request_route() 
> returns true (so that I don't accidentally call it from a branch route or 
> anything)
> rtpengine_manage() is called in its own route, which is very similar to the 
> example config file's "NATMANAGE" route. Since NATMANAGE is called in all 
> branch and on_reply_routes, I employ t_is_request_route() here to make sure 
> it won't execute in those cases.
> at the end of the "core" reply_route
> Now regarding the actual config-file-controlled SDP manipulation, it only 
> consists of a single call to replace_body_str(). The purpose is to edit a 
> line in the message body from something like:
> a=fmtp:101 0-16
> to something along the lines of:
> a=fmtp:101 0-15
> For replies, this works as expected.
> 
> For in-dialog requests, however, I end up with both the original and the 
> edited lines:
> a=fmtp:101 0-16 (the original line)
> ... other SDP stuff ...
> a=fmtp:101 0-15 (the edited line)
> 
> If anyone could point out any misconceptions I have about msg_apply_changes, 
> SDP rewriting from the script and rtp_engine_X() interoperability, I would be 
> more than grateful.
> 
> Thank you in advance and I apologize for the long read.
> 
> Best regards,
> George Diamantopoulos
> ___
> Kamailio (SER) - Users Mailing List
> sr-users@lists.kamailio.org
> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
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