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Re: Parsing diversion headers with osip

From: Aymeric Moizard
Subject: Re: Parsing diversion headers with osip
Date: Thu, 8 Jun 2023 15:35:06 +0200

Hi David,

Good to hear from you!

Instead of using osip_contact_t, I advise to use osip_from_t. They are very close, but the "Contact" header can have a special value which is the STAR character.

I searched for the definition of Diversion and I can see it was first defined in rfc5806. Later it was redefined in a proper way (using ABNF, as in rfc3261)

The big difference is the following:
1/ From header can have a name-addr OR addr-spec
2/ Diversion can only have a name-addr

Here is the definition of name-addr:

name-addr = [ display-name ] LAQUOT addr-spec RAQUOT

This means that the diversion sip address must always be inside < and > characters.

I've read my code and I think osip_from_to_str API is always using the name-addr form
even when it's not required. So it should be 100% compatible with the Diversion header.

The only mistake would be to accept Diversion with non standard format.

Best Regards!

Le jeu. 8 juin 2023 à 12:58, David Sugar <tychosoft@gmail.com> a écrit :

Diversion headers are sometimes used for call forwarding to voice mail and things like that.


It is in essence a uri with optional params, like to, from, contact objects, etc. Since contact seems the closest type, I currently try breaking it down into a osip_contact_t, which really is just a set of macros for underlying osip “generic” uri/param parsing  functions. My question is, should I really do that, should I call the underlying generic functions, or should I try creating osip_divert… macros and an osip_divert_t?


osip_header_t *divert{nullptr};

osip_message_header_get_byname(request, “Diversion”, 0, &divert);

if(divert && divert->hvalue) {

        osip_contact_t *fwd{nullptr};


        osip_contact_parse(fwd, divert->hvalue);


            leg->make_const({{"DIVERT_ID", fwd->displayname}});

        if(fwd->url && fwd->url->username)

            leg->make_const({{"DIVERT_FROM", fwd->url->username}});


        osip_uri_param_t *reason{nullptr};

        osip_contact_param_get_byname(fwd, const_cast<char *>("reason"), &reason);

        if(reason && reason->gvalue)

            leg->make_const({{"DIVERT_REASON", reason->gvalue}});


        osip_uri_param_t *privacy{nullptr};

        osip_contact_param_get_byname(fwd, const_cast<char *>("privacy"), &reason);

        if(privacy && privacy->gvalue)

            leg->make_const({{"DIVERT_PRIVACY", privacy->gvalue}});   

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