res_pjsip: crash when using localnet and external_signaling_address options

There was a collision of mod_data use on the transaction between using a nat
hook and an session response callback.  During state change it was assumed
what was in the mod_data was nothing or the response callback.  However, it
was possible for it to also contain a nat hook thus resulting in a bad cast
and a crash.

Added the ability to store multiple data elements in mod_data via a hash table.
In this instance, mod_data now stores a hash table of the two values that can
be retrieved using an associated string key.

(closes issue ASTERISK-22394)
Reported by: Rusty Newton
Review: https://reviewboard.asterisk.org/r/2843/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@399990 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_pjsip.c

@@ -1836,6 +1836,29 @@ int ast_sip_thread_is_servant(void)
 	return *servant_id == SIP_SERVANT_ID;
 }
 
+void *ast_sip_dict_get(void *ht, const char *key)
+{
+	unsigned int hval;
+
+	if (!ht) {
+		return NULL;
+	}
+
+	return pj_hash_get(ht, key, PJ_HASH_KEY_STRING, &hval);
+}
+
+void *ast_sip_dict_set(pj_pool_t* pool, void *ht,
+		       const char *key, void *val)
+{
+	if (!ht) {
+		ht = pj_hash_create(pool, 11);
+	}
+
+	pj_hash_set(pool, ht, key, PJ_HASH_KEY_STRING, 0, val);
+
+	return ht;
+}
+
 static void remove_request_headers(pjsip_endpoint *endpt)
 {
 	const pjsip_hdr *request_headers = pjsip_endpt_get_request_headers(endpt);