[sr-dev] What needs updating in Kamailio core/parser and modules for WebSockets

[Daniel-Constantin Mierla]

Hello,

On 6/22/12 11:13 AM, Peter Dunkley wrote:
> Hi,
>
> I am just trying to work out exactly what needs to be updated in the 
> Kamailio core/parser for WebSockets.
>
> I already know that the Via: parser needs to be updated to understand 
> the WS and WSS transports, and the URI parser needs to be updated to 
> understand the the WS transport, but is there anything else?
>
> I'd appreciate it if anyone has any ideas about what else might need 
> changed (and where in the code), as my guessing at this could be a bit 
> hit-and-miss...

indeed it might be hard to hit all at once, but it can be fixed as it 
goes on...

>
> I don't plan to add a forward_ws() function to core because I don't 
> think it'll work (or at least not in all cases as servers cannot 
> initiate WebSocket connections).  But are there updates needed in the 
> following areas (and any ideas where in the code I should look)?
>
>   * forward_no_connect()
>   * the proto core variable
>   * the snd_proto core variable
>

these are part of configuration file language, as special tokens -- the 
grammar of the config file is handled in cfg.lex and cfg.y. Then the 
interpretation is in action.c, with fixup and helpers in 
route_struct.{c,h} and route.{c,h}, and it may go through other files. I 
can help with flex/yacc part if needed.


>   * Is a WS keyword (like SCTP/TCP/TLS/UDP) needed
>
Yes, IMO, useful for detecting the incoming protocol
>
>   * Are the pseudo variables (for example, I know that the mutable
>     variable $du needs to do the right thing as this is fundamental to
>     being able to route requests), transformations, and selects that
>     need to be updated
>

The $du is practically just returning/setting a string, the 
interpretation is done by internal relay/forward functions. There are 
some pv/selects that return the protocol, they need updates, but should 
be trivial once the core part of defining the protocol types (e.g., like 
PROTO_WS/PROTO_WSS) and updating the uri parser and socket structures.

Btw, there will be dedicated sockets to listen for ws/wss or the tcp/tls 
will be used and the connection type upgraded to ws/wss?

>   * Are there any modules (rr, nathelper?) that need to be updated
>

There should be some helper functions that build URIs based on internal 
structures, where the protocol is used. Not sure all the modules use 
them or have own implementation. Perhaps searching on PROTO_TLS or 
another one will reveal the places where to add PROTO_WS/_WSS

Cheers,
Daniel

-- 
Daniel-Constantin Mierla - http://www.asipto.com
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
Kamailio Advanced Training, Seattle, USA, Sep 23-26, 2012 - http://asipto.com/u/katu
Kamailio Practical Workshop, Netherlands, Sep 10-12, 2012 - http://asipto.com/u/kpw

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