add sip_force_nat_mode so you can engange nat mode manually

src/mod/endpoints/mod_sofia/mod_sofia.c

@@ -1200,6 +1200,12 @@ static switch_status_t sofia_receive_message(switch_core_session_t *session, swi
 			const char *presence_id = switch_channel_get_variable(channel, "presence_id");
 
 
+			if ((var = switch_channel_get_variable(channel, "sip_force_nat_mode")) && switch_true(var)) {
+				sofia_set_flag(tech_pvt, TFLAG_NAT);
+				switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(session), SWITCH_LOG_DEBUG, "Setting NAT mode based on manual variable\n");
+				switch_channel_set_variable(channel, "sip_nat_detected", "true");
+			}
+
 			if ((var = switch_channel_get_variable(channel, "sip_enable_soa"))) {
 				if (switch_true(var)) {
 					sofia_set_flag(tech_pvt, TFLAG_ENABLE_SOA);