MT#63298 AmB2BSession: introduce `getMediaPort()`

Introduce AmSdp port getter.
Just takes the first available port which is > 0.

Change-Id: I49a4b850219c64d4720dafb3684dc9d11fa4594f

core/AmB2BSession.cpp

@@ -302,6 +302,21 @@ void AmB2BSession::addFakeSDPbasedOnPort(const AmMimeBody *src_sdp, AmMimeBody &
   createFakeReply(&fake_mimebody, new_body);
 }
 
+unsigned int AmB2BSession::getMediaPort(const AmSdp& sdp)
+{
+  unsigned int result = 0;
+
+  for (auto it = sdp.media.begin(); it != sdp.media.end(); ++it)
+  {
+    /* must be a legal port which must also not be ICE dummy port */
+    if (it->port > 0 && it->port != 9) {
+      result = it->port;
+      break;
+    }
+  }
+  return result;
+}
+
 void AmB2BSession::acceptPendingInvite(AmSipRequest *invite)
 {
   // reply the INVITE with fake 200 reply

core/AmB2BSession.h

@@ -213,6 +213,9 @@ private:
   /** create fake AmSipReply. SDP body based on SDP offer, but with a desired port */
   void addFakeSDPbasedOnPort(const AmMimeBody *src_sdp, AmMimeBody &new_body, unsigned int& desired_port);
 
+  /** get the first available media port */
+  unsigned int getMediaPort(const AmSdp& sdp);
+
   /** generate 200 SIP reply on a pending INVITE (uses fake body) */
   virtual void acceptPendingInvite(AmSipRequest *invite);