[SR-Users] Re: Question for RFC junkies / kamailio modifying message bodies

Hello Christoph, Kamailio is providing a lot of different functions. Some of these functions could be used to implement a network element with features which are forbidden in the RFC 3261 and/or other relevant RFCs. One of the most prominent examples is e.g., rewriting of From and To headers. It is in the end the responsibility of the implementing person to ensure that the relevant standards in the specific environments are observed. Cheers, Henning From: Valentin Christoph via sr-users &lt;sr-users(a)lists.kamailio.org&gt; Sent: Mittwoch, 6. März 2024 12:20 To: Kamailio (SER) - Users Mailing List &lt;sr-users(a)lists.kamailio.org&gt; Cc: Onic Roman &lt;Roman.Onic(a)kontron.com&gt;om>; Scherney Theodor &lt;Theodor.Scherney(a)kontron.com&gt;om>; Friedrich Peter &lt;Peter.Friedrich(a)kontron.com&gt;om>; Wolfgang Gleinser &lt;Wolfgang.Gleinser(a)kontron.com&gt;om>; Valentin Christoph &lt;Christoph.Valentin(a)kontron.com&gt; Subject: [SR-Users] Question for RFC junkies / kamailio modifying message bodies 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<https://www.rfc-editor.org/rfc/rfc3261.html#section-7.3.1>)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<https://www.rfc-editor.org/rfc/rfc3261.html#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