339 void handle_session_info(JingleNode *jn)

   340 {

   341   JingleSession *sess;

   342   SessionContent *sc;

   343   GSList *el;

   344 

   345   if ((sess = session_find(jn)) == NULL) {

   346     jingle_send_iq_error(jn->message, "cancel", "item-not-found", "unknown-session");

   347     return;

   348   }

   349 

   350   /* "If either party receives an empty session-info message

   351    * for an active session, it MUST send an empty IQ result;

   352    * this usage functions as a "ping" to determine session

   353    * vitality via the XMPP signalling channel." */

   354   if (jn->node->children == NULL) {

   355     jingle_ack_iq(jn->message);

   356     return;

   357   }

   358 

   359   /* We don't know the app to which the message is addressed.

   360    * Only the app module itself may know, based on the element

   361    * name and its xmlns, so we need to try every app module. */

   362   for (el = sess->content; el; el = el->next) {

   363     sc = (SessionContent*)el->data;

   364     if (sc->appfuncs->handle == NULL)

   365       continue;

   366 

   367     if (sc->appfuncs->handle(JINGLE_SESSION_INFO, sc->description,

   368                              jn->node->children)) {

   369       jingle_ack_iq(jn->message);

   370       return;

   371 	}

   372   }

   373   /* "If the party that receives an informational message

   374    * does not understand the payload, it MUST return a

   375    * <feature-not-implemented/> error with a Jingle-specific

   376    * error condition of <unsupported-info/>." */

   377   jingle_send_iq_error(jn->message, "modify", "feature-not-implemented",

   378                        "unsupported-info");

   379 }

   380