The RFCs are correct; strictly speaking, a proxy should not alter the encapsulated message
body, or most other SIP message attributes.
Kamailio is a huge toolbox with many capabilities, not unlike a programming language. It
gives one the power to do a great many things.
Some of these things aren't standards-compliant, and that's okay. The ends justify
the means. Other times--many times--call for judicious restraint, as just because Kamailio
can do something doesn't mean that you should do it, or that using a tool Kamailio
offers to do something bluntly is a good substitute for doing something delicately.
Knowing the difference is the soul of experience. :-)
-- Alex
On 6 Mar 2024, at 06:19, Valentin Christoph via
sr-users <sr-users(a)lists.kamailio.org> wrote:
Hi all,
it might be a minor issue, or it might not be an issue at all, but I stumbled over
following statements in RFC 3261:
Chapter 16.6 Request Forwarding (of a proxy)
1. Copy request
The proxy starts with a copy of the received request. The copy
MUST initially contain all of the header fields from the
received request. Fields not detailed in the processing
described below MUST NOT be removed. The copy SHOULD maintain
the ordering of the header fields as in the received request.
The proxy MUST NOT reorder field values with a common field
name (See Section 7.3.1). The proxy MUST NOT add to, modify,
or remove the message body.
An actual implementation need not perform a copy; the primary
requirement is that the processing for each next hop begin with
the same request.
Chapter 16.7 Response Processing (at a proxy)
9. Forward response
After performing the processing described in steps "Aggregate
Authorization Header Field Values" through "Record-Route", the
proxy MAY perform any feature specific manipulations on the
selected response. The proxy MUST NOT add to, modify, or
remove the message body. Unless otherwise specified, the proxy
MUST NOT remove any header field values other than the Via
header field value discussed in Section 16.7 Item 3. In
particular, the proxy MUST NOT remove any "received" parameter
On the other hand, everywhere in the Internet (starting with stackoverflow), you can
read it is OK, if a SIP proxy modifies a body, and also kamailio allows it.
Might be a question for the coffee break.
All the best
Christoph
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Alex Balashov
Principal Consultant
Evariste Systems LLC
Web:
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Tel: +1-706-510-6800