[Kamailio-Devel] [ openser-Feature Requests-2135690 ] Improve $(hdr[N]) handling of comma-separated header bodies

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Feature Requests item #2135690, was opened at 2008-09-29 11:26
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Jerome Martin (tramjoe)
Assigned to: Nobody/Anonymous (nobody)
Summary: Improve $(hdr[N]) handling of comma-separated header bodies

Initial Comment:
The SIP headers can have two different forms allowing multiple header bodies in a messages: either multiple comma-separated bodies in a single header line, or many header lines containing a single body. Those two forms can be combined in the same message and are semantically strictly equivalent. Kamailio internals do a proper job in handling this AFAIK (i.e. for Via: header), but user-side $(hdr(foobar)[N]) form requires additionnal user-side parsing to acheive this. Here is an example of what is required to currently extract the 2nd Via: body in a SIP message and stay compatible with both forms:

# If we have a comma-separated list of via bodies in 
# the first Via header, extract the destination 
# address from there
$avp(s:destination_address) = $(hdr(Via)[0]{s.select,1,,}{s.select,0,;}{s.select,2, });
 
if (!$avp(s:destination_address)) {
    # Else, extract it from the second Via header
    $avp(s:destination_address) = $(hdr(Via)[1]{s.select,0,;}{s.select,1, });
    # We used single-body Via headers
} else {
    # Using multi-body Via headers
}

# Now $avp(s:destination_address) holds the relay address for the reply

This proposal aims at adding handling of comma-separated bodies in a single header line while still staying fully backward compatible with multi-line headers (aka 1 body per header, multiple headers.).

In order to do so, I suggest to keep the exact same syntax on the script-side: $(avp(foobar)[N]), but instead of having N mean "the N-th occurence of header line foobar", I would like N to mean "the N-th body of header foobar".

Examples :

1/ Only single body headers:

Foobar: body1
Foobar: body2

This would be handled the same as currently:
$(avp(Foobar)[1]) == "body1"
$(avp(Foobar)[2]) == "body2"

2/ Only multibody header:

Foobar: body1, body2

Currently, we have:
$(avp(Foobar)[1]) == "body1,body2"
$(avp(Foobar)[2]) == <null>

I suggest we return instead:
$(avp(Foobar)[1]) == "body1"
$(avp(Foobar)[2]) == "body2"

The effect here is that the same code works for example 1 AND example 2 no matter what form is used by the sending UA.

3/ Mixed header forms:

Foobar: body1
Foobar: body2, body3
Foobar: body4

$(avp(Foobar)[1]) == "body1"
$(avp(Foobar)[2]) == "body2"
$(avp(Foobar)[3]) == "body3"
$(avp(Foobar)[4]) == "body4"




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