MT#61574 AmOfferAnswer: don't generate SDP answer if offer empty

When replying with 200OK generated by SEMS to INVITE requests,
which have no SDP body included, just answer with empty 200OK.

This sets the `OAState` of the call leg to `OA_None`.

Change-Id: Ic28e80d670ba4ce98be6abac9d17689688f99f71

core/AmOfferAnswer.cpp

@@ -361,7 +361,7 @@ int AmOfferAnswer::onRequestOut(AmSipRequest& req)
   return 0;
 }
 
-int AmOfferAnswer::onReplyOut(AmSipReply& reply)
+int AmOfferAnswer::onReplyOut(AmSipReply& reply, bool no_sdp_generation)
 {
   AmMimeBody* sdp_body = reply.body.hasContentType(SIP_APPLICATION_SDP);
   AmMimeBody* csta_body = reply.body.hasContentType(SIP_APPLICATION_CSTA_XML);
@@ -418,9 +418,10 @@ int AmOfferAnswer::onReplyOut(AmSipReply& reply)
       } else if ((reply.code == 183) || ((reply.code >= 200) && (reply.code < 300))) {
 
         /* either offer received or no offer at all: -> force SDP */
-        generate_sdp = (state == OA_OfferRecved)
+        generate_sdp =  !no_sdp_generation &&
+                        ((state == OA_OfferRecved)
                         || (state == OA_None)
-                        || (state == OA_Completed);
+                        || (state == OA_Completed));
       }
 
     } else if (reply.cseq_method == SIP_METH_UPDATE) {
@@ -473,7 +474,7 @@ int AmOfferAnswer::onReplyOut(AmSipReply& reply)
   } else if (sdp_body && has_sdp) {
     /* update local SDP copy */
     if (sdp_local.parse((const char*)sdp_body->getPayload())) {
-      ERROR("parser failed on Tx SDP: '%s'\n", (const char*)sdp_body->getPayload());
+      WARN("parser failed on Tx SDP: '%s'\n", (const char*)sdp_body->getPayload());
     }
   }
 

core/AmOfferAnswer.h

@@ -85,7 +85,8 @@ public:
   int onRequestIn(const AmSipRequest& req);
   int onReplyIn(const AmSipReply& reply);
   int onRequestOut(AmSipRequest& req);
-  int onReplyOut(AmSipReply& reply);
+  /* `no_sdp_generation` - can be used for cases like absent SDP in coming INVITE */
+  int onReplyOut(AmSipReply& reply, bool no_sdp_generation = false);
   int onRequestSent(const AmSipRequest& req);
   int onReplySent(const AmSipReply& reply);
   void onNoAck(unsigned int ack_cseq);

core/AmSipDialog.cpp

@@ -271,7 +271,7 @@ int AmSipDialog::onTxRequest(AmSipRequest& req, int& flags)
 int AmSipDialog::onTxReply(const AmSipRequest& req, AmSipReply& reply, int& flags)
 {
   if (offeranswer_enabled) {
-    if(oa.onReplyOut(reply) < 0)
+    if(oa.onReplyOut(reply, req.body.empty()) < 0)
       return -1;
   }