From 68cd8dde3edb37012eea5c2e8aec831617325fa3 Mon Sep 17 00:00:00 2001
From: Donat Zenichev <dzenichev@sipwise.com>
Date: Thu, 30 Jul 2026 15:15:32 +0200
Subject: [PATCH] MT#65357 OA: don't change state on empty 183

If 183 has empty body, don't change the state,
because otherwise it will break the OA model exchange
in later updates during the continued early dialog stage.

Keep pretending to remain in the `Completed` state.

Change-Id: I1053740a179c8589b54a0c856caa438a92521fda
---
 core/AmOfferAnswer.cpp | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/core/AmOfferAnswer.cpp b/core/AmOfferAnswer.cpp
index 60334cca..39faf048 100644
--- a/core/AmOfferAnswer.cpp
+++ b/core/AmOfferAnswer.cpp
@@ -349,8 +349,10 @@ int AmOfferAnswer::onRxSdp(unsigned int m_cseq, const string& m_remote_tag,
   return err_code;
 }
 
-int AmOfferAnswer::onTxSdp(unsigned int m_cseq, bool is_reliable,
-                           const AmMimeBody& body, bool force_no_sdp_update)
+int AmOfferAnswer::onTxSdp(unsigned int m_cseq,
+                            bool is_reliable,
+                            const AmMimeBody& body,
+                            bool force_no_sdp_update)
 {
   ILOG_DLG(L_DBG, "AmOfferAnswer::onTxSdp()\n");
 
@@ -444,7 +446,7 @@ int AmOfferAnswer::onRequestOut(AmSipRequest& req)
   }
 
   if ((has_sdp || (has_csta && req.method != SIP_METH_INFO)) &&
-      (onTxSdp(req.cseq, true, req.body) != 0))
+      (onTxSdp(req.cseq, true, req.body, false) != 0))
   {
     ILOG_DLG(L_WARN, "onTxSdp() failed\n");
     return -1;
@@ -458,7 +460,10 @@ int AmOfferAnswer::onReplyOut(AmSipReply& reply, int &flags, AmMimeBody &ret_bod
   AmMimeBody* sdp_body = reply.body.hasContentType(SIP_APPLICATION_SDP);
   AmMimeBody* csta_body = reply.body.hasContentType(SIP_APPLICATION_CSTA_XML);
 
-  bool force_no_sdp_update = false;   /* for sequential 183 responses with similar SDP body (version)  */
+  /* for sequential 183 responses with similar SDP body (version)
+   * or 183 with no SDP body */
+  bool force_no_sdp_update = false;
+
   bool generate_sdp = sdp_body && !sdp_body->getLen();
   bool has_sdp = sdp_body && sdp_body->getLen();
   bool has_csta = csta_body && csta_body->getLen();
@@ -507,6 +512,13 @@ int AmOfferAnswer::onReplyOut(AmSipReply& reply, int &flags, AmMimeBody &ret_bod
         has_sdp = true;
         ILOG_DLG(L_DBG, "Now has_sdp has been reset to true.\n");
 
+        /* for empty body 183, don't change the state,
+         * otherwise breaks the OA model exchange
+         * in later updates during the continued early dialog stage */
+        force_no_sdp_update = true;
+
+        ILOG_DLG(L_DBG, "Forcing no OA state update, because this 183 has no SDP.\n");
+
       /* - 183 reply without SDP body, but is very first one (no SDP saved before)
          - 200-299 responses with no SDP */
       } else if ((reply.code == 183) || ((reply.code >= 200) && (reply.code < 300))) {
@@ -582,7 +594,11 @@ int AmOfferAnswer::onReplyOut(AmSipReply& reply, int &flags, AmMimeBody &ret_bod
   if (has_sdp || (has_csta && reply.cseq_method != SIP_METH_INFO)) {
     bool is_reliable = dlg->willBeReliable(reply);
 
-    if ((onTxSdp(reply.cseq, is_reliable, reply.body, force_no_sdp_update) != 0)) {
+    if ((onTxSdp(reply.cseq,
+                 is_reliable,
+                 reply.body,
+                 force_no_sdp_update) != 0))
+    {
       ILOG_DLG(L_WARN, "onTxSdp() failed\n");
       return -1;
     }