More work on stateful proxy sample

git-svn-id: http://svn.pjsip.org/repos/pjproject/branches/pjproject-0.5-stable@1123 74dad513-b988-da41-8d7b-12977e46ad98

3 files changed, 482 insertions, 164 deletions

diff --git a/pjsip-apps/src/samples/proxy.h b/pjsip-apps/src/samples/proxy.h
index a7cba80c..5f62a503 100644
--- a/pjsip-apps/src/samples/proxy.h
+++ b/pjsip-apps/src/samples/proxy.h
@@ -53,9 +53,10 @@ static void usage(void)
 {
     puts("Options:\n"
 	 "\n"
-	 " -p, --port N    Set local listener port to N\n"
-	 " -R, --rr        Perform record routing\n"
-	 " -h, --help      Show this help screen\n"
+	 " --port N       Set local listener port to N\n"
+	 " --rr           Perform record routing\n"
+	 " --log-level N  Set log level to N (default: 4)\n"
+	 " --help         Show this help screen\n"
 	 );
 }
 
@@ -63,15 +64,16 @@ static void usage(void)
 static pj_status_t init_options(int argc, char *argv[])
 {
     struct pj_getopt_option long_opt[] = {
-	{ "port",1, 0, 'p'},
-	{ "rr",  1, 0, 'R'},
-	{ "help",1, 0, 'h'},
+	{ "port",	1, 0, 'p'},
+	{ "rr",		0, 0, 'R'},
+	{ "log-level",	1, 0, 'L'},
+	{ "help",	0, 0, 'h'},
     };
     int c;
     int opt_ind;
 
     pj_optind = 0;
-    while((c=pj_getopt_long(argc, argv, "pRh", long_opt, &opt_ind))!=-1) {
+    while((c=pj_getopt_long(argc, argv, "", long_opt, &opt_ind))!=-1) {
 	switch (c) {
 	case 'p':
 	    global.port = atoi(pj_optarg);
@@ -83,13 +85,17 @@ static pj_status_t init_options(int argc, char *argv[])
 	    printf("Using record route mode\n");
 	    break;
 
+	case 'L':
+	    pj_log_set_level(atoi(pj_optarg));
+	    break;
+
 	case 'h':
 	    usage();
 	    return -1;
 
 	default:
-	    puts("Unknown option ignored");
-	    break;
+	    puts("Unknown option. Run with --help for help.");
+	    return -1;
 	}
     }
 
@@ -97,6 +103,83 @@ static pj_status_t init_options(int argc, char *argv[])
 }
 
 
+/*****************************************************************************
+ * This is a very simple PJSIP module, whose sole purpose is to display
+ * incoming and outgoing messages to log. This module will have priority
+ * higher than transport layer, which means:
+ *
+ *  - incoming messages will come to this module first before reaching
+ *    transaction layer.
+ *
+ *  - outgoing messages will come to this module last, after the message
+ *    has been 'printed' to contiguous buffer by transport layer and
+ *    appropriate transport instance has been decided for this message.
+ *
+ */
+
+/* Notification on incoming messages */
+static pj_bool_t logging_on_rx_msg(pjsip_rx_data *rdata)
+{
+    PJ_LOG(5,(THIS_FILE, "RX %d bytes %s from %s %s:%d:\n"
+			 "%.*s\n"
+			 "--end msg--",
+			 rdata->msg_info.len,
+			 pjsip_rx_data_get_info(rdata),
+			 rdata->tp_info.transport->type_name,
+			 rdata->pkt_info.src_name,
+			 rdata->pkt_info.src_port,
+			 (int)rdata->msg_info.len,
+			 rdata->msg_info.msg_buf));
+    
+    /* Always return false, otherwise messages will not get processed! */
+    return PJ_FALSE;
+}
+
+/* Notification on outgoing messages */
+static pj_status_t logging_on_tx_msg(pjsip_tx_data *tdata)
+{
+    
+    /* Important note:
+     *	tp_info field is only valid after outgoing messages has passed
+     *	transport layer. So don't try to access tp_info when the module
+     *	has lower priority than transport layer.
+     */
+
+    PJ_LOG(5,(THIS_FILE, "TX %d bytes %s to %s %s:%d:\n"
+			 "%.*s\n"
+			 "--end msg--",
+			 (tdata->buf.cur - tdata->buf.start),
+			 pjsip_tx_data_get_info(tdata),
+			 tdata->tp_info.transport->type_name,
+			 tdata->tp_info.dst_name,
+			 tdata->tp_info.dst_port,
+			 (int)(tdata->buf.cur - tdata->buf.start),
+			 tdata->buf.start));
+
+    /* Always return success, otherwise message will not get sent! */
+    return PJ_SUCCESS;
+}
+
+/* The module instance. */
+static pjsip_module mod_msg_logger = 
+{
+    NULL, NULL,				/* prev, next.		*/
+    { "mod-msg-logger", 14 },		/* Name.		*/
+    -1,					/* Id			*/
+    PJSIP_MOD_PRIORITY_TRANSPORT_LAYER-1,/* Priority	        */
+    NULL,				/* load()		*/
+    NULL,				/* start()		*/
+    NULL,				/* stop()		*/
+    NULL,				/* unload()		*/
+    &logging_on_rx_msg,			/* on_rx_request()	*/
+    &logging_on_rx_msg,			/* on_rx_response()	*/
+    &logging_on_tx_msg,			/* on_tx_request.	*/
+    &logging_on_tx_msg,			/* on_tx_response()	*/
+    NULL,				/* on_tsx_state()	*/
+
+};
+
+
 static pj_status_t init_stack(void)
 {
     pj_status_t status;
@@ -142,6 +225,9 @@ static pj_status_t init_stack(void)
     global.pool = pj_pool_create(&global.cp.factory, "proxyapp", 
 				 4000, 4000, NULL);
 
+    /* Register the logger module */
+    pjsip_endpt_register_module(global.endpt, &mod_msg_logger);
+
     return PJ_SUCCESS;
 }
 
@@ -412,11 +498,13 @@ static pj_status_t proxy_calculate_target(pjsip_rx_data *rdata,
      */
 
     /* We're not interested to receive request destined to us, so
-     * respond with 404/Not Found.
+     * respond with 404/Not Found (only if request is not ACK!).
      */
-    pjsip_endpt_respond_stateless(global.endpt, rdata,
-				  PJSIP_SC_NOT_FOUND, NULL,
-				  NULL, NULL);
+    if (rdata->msg_info.msg->line.req.method.id != PJSIP_ACK_METHOD) {
+	pjsip_endpt_respond_stateless(global.endpt, rdata,
+				      PJSIP_SC_NOT_FOUND, NULL,
+				      NULL, NULL);
+    }
 
     /* Delete the request since we're not forwarding it */
     pjsip_tx_data_dec_ref(tdata);
diff --git a/pjsip-apps/src/samples/stateful_proxy.c b/pjsip-apps/src/samples/stateful_proxy.c
index 2bce9188..d83ec91c 100644
--- a/pjsip-apps/src/samples/stateful_proxy.c
+++ b/pjsip-apps/src/samples/stateful_proxy.c
@@ -23,172 +23,280 @@
 #include "proxy.h"
 
 
-/* Callback to be called to handle incoming requests. */
-static pj_bool_t on_rx_request( pjsip_rx_data *rdata );
-
-/* Callback to be called to handle incoming response. */
-static pj_bool_t on_rx_response( pjsip_rx_data *rdata );
-
+/*
+ * mod_stateful_proxy is the module to receive SIP request and
+ * response message that is outside any transaction context.
+ */
+static pj_bool_t proxy_on_rx_request(pjsip_rx_data *rdata );
+static pj_bool_t proxy_on_rx_response(pjsip_rx_data *rdata );
 
-/* This is the data that is attached to the UAC transaction */
-struct tsx_data
+static pjsip_module mod_stateful_proxy =
 {
-    pjsip_transaction	*uas_tsx;
-    pj_timer_entry	 timer;
+    NULL, NULL,				/* prev, next.		*/
+    { "mod-stateful-proxy", 18 },	/* Name.		*/
+    -1,					/* Id			*/
+    PJSIP_MOD_PRIORITY_UA_PROXY_LAYER,	/* Priority		*/
+    NULL,				/* load()		*/
+    NULL,				/* start()		*/
+    NULL,				/* stop()		*/
+    NULL,				/* unload()		*/
+    &proxy_on_rx_request,		/* on_rx_request()	*/
+    &proxy_on_rx_response,		/* on_rx_response()	*/
+    NULL,				/* on_tx_request.	*/
+    NULL,				/* on_tx_response()	*/
+    NULL,				/* on_tsx_state()	*/
 };
 
 
-static pjsip_module mod_stateful_proxy =
+/*
+ * mod_tu (tu=Transaction User) is the module to receive notification
+ * from transaction when the transaction state has changed.
+ */
+static void tu_on_tsx_state(pjsip_transaction *tsx, pjsip_event *event);
+
+static pjsip_module mod_tu =
 {
-    NULL, NULL,		        /* prev, next.		*/
-    { "mod-stateful-proxy", 18 },	/* Name.		*/
-    -1,			        /* Id			*/
-    PJSIP_MOD_PRIORITY_APPLICATION, /* Priority		*/
+    NULL, NULL,				/* prev, next.		*/
+    { "mod-transaction-user", 20 },	/* Name.		*/
+    -1,					/* Id			*/
+    PJSIP_MOD_PRIORITY_APPLICATION,	/* Priority		*/
     NULL,				/* load()		*/
     NULL,				/* start()		*/
     NULL,				/* stop()		*/
     NULL,				/* unload()		*/
-    &on_rx_request,			/* on_rx_request()	*/
-    &on_rx_response,	        /* on_rx_response()	*/
+    NULL,				/* on_rx_request()	*/
+    NULL,				/* on_rx_response()	*/
     NULL,				/* on_tx_request.	*/
     NULL,				/* on_tx_response()	*/
-    NULL,				/* on_tsx_state()	*/
+    &tu_on_tsx_state,			/* on_tsx_state()	*/
 };
 
 
+/* This is the data that is attached to the UAC transaction */
+struct uac_data
+{
+    pjsip_transaction	*uas_tsx;
+    pj_timer_entry	 timer;
+};
+
+
+/* This is the data that is attached to the UAS transaction */
+struct uas_data
+{
+    pjsip_transaction	*uac_tsx;
+};
+
+
+
 static pj_status_t init_stateful_proxy(void)
 {
     pj_status_t status;
 
-    /* Register our module to receive incoming requests. */
     status = pjsip_endpt_register_module( global.endpt, &mod_stateful_proxy);
     PJ_ASSERT_RETURN(status == PJ_SUCCESS, 1);
 
+    status = pjsip_endpt_register_module( global.endpt, &mod_tu);
+    PJ_ASSERT_RETURN(status == PJ_SUCCESS, 1);
+
     return PJ_SUCCESS;
 }
 
 
-/* Callback to be called to handle incoming requests. */
-static pj_bool_t on_rx_request( pjsip_rx_data *rdata )
+/* Callback to be called to handle new incoming requests. */
+static pj_bool_t proxy_on_rx_request( pjsip_rx_data *rdata )
 {
     pjsip_transaction *uas_tsx, *uac_tsx;
-    struct tsx_data *tsx_data;
+    struct uac_data *uac_data;
+    struct uas_data *uas_data;
     pjsip_tx_data *tdata;
     pj_status_t status;
 
-    /* Verify incoming request */
-    status = proxy_verify_request(rdata);
-    if (status != PJ_SUCCESS) {
-	app_perror("RX invalid request", status);
-	return PJ_TRUE;
-    }
+    if (rdata->msg_info.msg->line.req.method.id != PJSIP_CANCEL_METHOD) {
 
-    /*
-     * Request looks sane, next clone the request to create transmit data.
-     */
-    status = pjsip_endpt_create_request_fwd(global.endpt, rdata, NULL,
-					    NULL, 0, &tdata);
-    if (status != PJ_SUCCESS) {
-	pjsip_endpt_respond_stateless(global.endpt, rdata,
-				      PJSIP_SC_INTERNAL_SERVER_ERROR, NULL, 
-				      NULL, NULL);
-	return PJ_TRUE;
-    }
+	/* Verify incoming request */
+	status = proxy_verify_request(rdata);
+	if (status != PJ_SUCCESS) {
+	    app_perror("RX invalid request", status);
+	    return PJ_TRUE;
+	}
 
+	/*
+	 * Request looks sane, next clone the request to create transmit data.
+	 */
+	status = pjsip_endpt_create_request_fwd(global.endpt, rdata, NULL,
+						NULL, 0, &tdata);
+	if (status != PJ_SUCCESS) {
+	    pjsip_endpt_respond_stateless(global.endpt, rdata,
+					  PJSIP_SC_INTERNAL_SERVER_ERROR, 
+					  NULL, NULL, NULL);
+	    return PJ_TRUE;
+	}
 
-    /* Process routing */
-    status = proxy_process_routing(tdata);
-    if (status != PJ_SUCCESS) {
-	app_perror("Error processing route", status);
-	return PJ_TRUE;
-    }
 
-    /* Calculate target */
-    status = proxy_calculate_target(rdata, tdata);
-    if (status != PJ_SUCCESS) {
-	app_perror("Error calculating target", status);
-	return PJ_TRUE;
-    }
+	/* Process routing */
+	status = proxy_process_routing(tdata);
+	if (status != PJ_SUCCESS) {
+	    app_perror("Error processing route", status);
+	    return PJ_TRUE;
+	}
+
+	/* Calculate target */
+	status = proxy_calculate_target(rdata, tdata);
+	if (status != PJ_SUCCESS) {
+	    app_perror("Error calculating target", status);
+	    return PJ_TRUE;
+	}
 
-    /* Everything is set to forward the request. */
+	/* Everything is set to forward the request. */
 
-    /* If this is an ACK request, forward statelessly */
-    if (tdata->msg->line.req.method.id == PJSIP_ACK_METHOD) {
-	status = pjsip_endpt_send_request_stateless(global.endpt, tdata, 
-						    NULL, NULL);
+	/* If this is an ACK request, forward statelessly.
+	 * This happens if the proxy records route and this ACK
+	 * is sent for 2xx response. An ACK that is sent for non-2xx
+	 * final response will be absorbed by transaction layer, and
+	 * it will not be received by on_rx_request() callback.
+	 */
+	if (tdata->msg->line.req.method.id == PJSIP_ACK_METHOD) {
+	    status = pjsip_endpt_send_request_stateless(global.endpt, tdata, 
+							NULL, NULL);
+	    if (status != PJ_SUCCESS) {
+		app_perror("Error forwarding request", status);
+		return PJ_TRUE;
+	    }
+
+	    return PJ_TRUE;
+	}
+
+	/* Create UAC transaction for forwarding the request. 
+	 * Set our module as the transaction user to receive further
+	 * events from this transaction.
+	 */
+	status = pjsip_tsx_create_uac(&mod_tu, tdata, &uac_tsx);
 	if (status != PJ_SUCCESS) {
-	    app_perror("Error forwarding request", status);
+	    pjsip_tx_data_dec_ref(tdata);
+	    pjsip_endpt_respond_stateless(global.endpt, rdata, 
+					  PJSIP_SC_INTERNAL_SERVER_ERROR, 
+					  NULL, NULL, NULL);
 	    return PJ_TRUE;
 	}
 
-	return PJ_TRUE;
-    }
+	/* Create UAS transaction to handle incoming request */
+	status = pjsip_tsx_create_uas(&mod_tu, rdata, &uas_tsx);
+	if (status != PJ_SUCCESS) {
+	    pjsip_tx_data_dec_ref(tdata);
+	    pjsip_endpt_respond_stateless(global.endpt, rdata, 
+					  PJSIP_SC_INTERNAL_SERVER_ERROR, 
+					  NULL, NULL, NULL);
+	    pjsip_tsx_terminate(uac_tsx, PJSIP_SC_INTERNAL_SERVER_ERROR);
+	    return PJ_TRUE;
+	}
 
-    /* Create UAC transaction for forwarding the request */
-    status = pjsip_tsx_create_uac(&mod_stateful_proxy, tdata, &uac_tsx);
-    if (status != PJ_SUCCESS) {
-	pjsip_tx_data_dec_ref(tdata);
-	pjsip_endpt_respond_stateless(global.endpt, rdata, 
-				      PJSIP_SC_INTERNAL_SERVER_ERROR, NULL,
-				      NULL, NULL);
-	return PJ_TRUE;
-    }
+	/* Feed the request to the UAS transaction to drive it's state 
+	 * out of NULL state. 
+	 */
+	pjsip_tsx_recv_msg(uas_tsx, rdata);
 
-    /* Create UAS transaction to handle incoming request */
-    status = pjsip_tsx_create_uas(&mod_stateful_proxy, rdata, &uas_tsx);
-    if (status != PJ_SUCCESS) {
-	pjsip_tx_data_dec_ref(tdata);
-	pjsip_endpt_respond_stateless(global.endpt, rdata, 
-				      PJSIP_SC_INTERNAL_SERVER_ERROR, NULL,
-				      NULL, NULL);
-	pjsip_tsx_terminate(uac_tsx, PJSIP_SC_INTERNAL_SERVER_ERROR);
-	return PJ_TRUE;
-    }
+	/* Attach a data to the UAC transaction, to be used to find the
+	 * UAS transaction when we receive response in the UAC side.
+	 */
+	uac_data = (struct uac_data*)
+		   pj_pool_alloc(uac_tsx->pool, sizeof(struct uac_data));
+	uac_data->uas_tsx = uas_tsx;
+	uac_tsx->mod_data[mod_tu.id] = (void*)uac_data;
 
-    /* Feed the request to the UAS transaction to drive it's state 
-     * out of NULL state. 
-     */
-    pjsip_tsx_recv_msg(uas_tsx, rdata);
+	/* Attach data to the UAS transaction, to find the UAC transaction
+	 * when cancelling INVITE request.
+	 */
+	uas_data = (struct uas_data*)
+		    pj_pool_alloc(uas_tsx->pool, sizeof(struct uas_data));
+	uas_data->uac_tsx = uac_tsx;
+	uas_tsx->mod_data[mod_tu.id] = (void*)uas_data;
 
-    /* Attach a data to the UAC transaction, to be used to find the
-     * UAS transaction when we receive response in the UAC side.
-     */
-    tsx_data = pj_pool_alloc(uac_tsx->pool, sizeof(struct tsx_data));
-    tsx_data->uas_tsx = uas_tsx;
-    
-    uac_tsx->mod_data[mod_stateful_proxy.id] = (void*)tsx_data;
+	/* Everything is setup, forward the request */
+	status = pjsip_tsx_send_msg(uac_tsx, tdata);
+	if (status != PJ_SUCCESS) {
+	    pjsip_tx_data *err_res;
 
-    /* Everything is setup, forward the request */
-    status = pjsip_tsx_send_msg(uac_tsx, tdata);
-    if (status != PJ_SUCCESS) {
-	pjsip_tx_data *err_res;
+	    /* Fail to send request, for some reason */
 
-	/* Fail to send request, for some reason */
+	    /* Destroy transmit data */
+	    pjsip_tx_data_dec_ref(tdata);
 
-	/* Destroy UAC transaction */
-	pjsip_tx_data_dec_ref(tdata);
-	pjsip_tsx_terminate(uac_tsx, PJSIP_SC_INTERNAL_SERVER_ERROR);
+	    /* I think UAC transaction should have been destroyed when
+	     * it fails to send request, so no need to destroy it.
+	    pjsip_tsx_terminate(uac_tsx, PJSIP_SC_INTERNAL_SERVER_ERROR);
+	     */
 
-	/* Send 500/Internal Server Error to UAS transaction */
-	status = pjsip_endpt_create_response(global.endpt, rdata,
-					     PJSIP_SC_INTERNAL_SERVER_ERROR,
-					     NULL, &err_res);
-	if (status == PJ_SUCCESS)
+	    /* Send 500/Internal Server Error to UAS transaction */
+	    pjsip_endpt_create_response(global.endpt, rdata,
+					500, NULL, &err_res);
 	    pjsip_tsx_send_msg(uas_tsx, err_res);
-	else
-	    pjsip_tsx_terminate(uac_tsx, PJSIP_SC_INTERNAL_SERVER_ERROR);
 
-	return PJ_TRUE;
+	    return PJ_TRUE;
+	}
+
+	/* Send 100/Trying if this is an INVITE */
+	if (rdata->msg_info.msg->line.req.method.id == PJSIP_INVITE_METHOD) {
+	    pjsip_tx_data *res100;
+
+	    pjsip_endpt_create_response(global.endpt, rdata, 100, NULL, 
+					&res100);
+	    pjsip_tsx_send_msg(uas_tsx, res100);
+	}
+
+    } else {
+	/* This is CANCEL request */
+	pjsip_transaction *invite_uas;
+	struct uas_data *uas_data;
+	pj_str_t key;
+	
+	/* Find the UAS INVITE transaction */
+	pjsip_tsx_create_key(rdata->tp_info.pool, &key, PJSIP_UAS_ROLE,
+			     &pjsip_invite_method, rdata);
+	invite_uas = pjsip_tsx_layer_find_tsx(&key, PJ_TRUE);
+	if (!invite_uas) {
+	    /* Invite transaction not found, respond CANCEL with 481 */
+	    pjsip_endpt_respond_stateless(global.endpt, rdata, 481, NULL,
+					  NULL, NULL);
+	    return PJ_TRUE;
+	}
+
+	/* Respond 200 OK to CANCEL */
+	pjsip_endpt_respond(global.endpt, NULL, rdata, 200, NULL, NULL,
+			    NULL, NULL);
+
+	/* Send CANCEL to cancel the UAC transaction.
+	 * The UAS INVITE transaction will get final response when
+	 * we receive final response from the UAC INVITE transaction.
+	 */
+	uas_data = (struct uas_data*) invite_uas->mod_data[mod_tu.id];
+	if (uas_data->uac_tsx) {
+	    pjsip_tx_data *cancel;
+
+	    pj_mutex_lock(uas_data->uac_tsx->mutex);
+
+	    pjsip_endpt_create_cancel(global.endpt, uas_data->uac_tsx->last_tx,
+				      &cancel);
+	    pjsip_endpt_send_request(global.endpt, cancel, -1, NULL, NULL);
+
+	    pj_mutex_unlock(uas_data->uac_tsx->mutex);
+	}
+
+	/* Unlock UAS tsx because it is locked in find_tsx() */
+	pj_mutex_unlock(invite_uas->mutex);
     }
 
     return PJ_TRUE;
 }
 
 
-/* Callback to be called to handle incoming response. */
-static pj_bool_t on_rx_response( pjsip_rx_data *rdata )
+/* Callback to be called to handle incoming response outside
+ * any transactions. This happens for example when 2xx/OK
+ * for INVITE is received and transaction will be destroyed
+ * immediately, so we need to forward the subsequent 2xx/OK
+ * retransmission statelessly.
+ */
+static pj_bool_t proxy_on_rx_response( pjsip_rx_data *rdata )
 {
-    pjsip_transaction *uac_tsx;
     pjsip_tx_data *tdata;
     pjsip_response_addr res_addr;
     pjsip_via_hdr *hvia;
@@ -212,7 +320,8 @@ static pj_bool_t on_rx_response( pjsip_rx_data *rdata )
     /* Calculate the address to forward the response */
     pj_bzero(&res_addr, sizeof(res_addr));
     res_addr.dst_host.type = PJSIP_TRANSPORT_UDP;
-    res_addr.dst_host.flag = pjsip_transport_get_flag_from_type(PJSIP_TRANSPORT_UDP);
+    res_addr.dst_host.flag = 
+	pjsip_transport_get_flag_from_type(PJSIP_TRANSPORT_UDP);
 
     /* Destination address is Via's received param */
     res_addr.dst_host.addr.host = hvia->recvd_param;
@@ -221,7 +330,7 @@ static pj_bool_t on_rx_response( pjsip_rx_data *rdata )
 	res_addr.dst_host.addr.host = hvia->sent_by.host;
     }
 
-    /* Destination port is the rpot */
+    /* Destination port is the rport */
     if (hvia->rport_param != 0 && hvia->rport_param != -1)
 	res_addr.dst_host.addr.port = hvia->rport_param;
 
@@ -232,40 +341,162 @@ static pj_bool_t on_rx_response( pjsip_rx_data *rdata )
 	res_addr.dst_host.addr.port = hvia->sent_by.port;
     }
 
-    uac_tsx = pjsip_rdata_get_tsx(rdata);
+    /* Forward response */
+    status = pjsip_endpt_send_response(global.endpt, &res_addr, tdata,
+				       NULL, NULL);
+    if (status != PJ_SUCCESS) {
+	app_perror("Error forwarding response", status);
+	return PJ_TRUE;
+    }
 
-    if (!uac_tsx) {
-	/* UAC transaction not found (it may have been destroyed).
-	 * Forward response statelessly.
-	 */
-	status = pjsip_endpt_send_response(global.endpt, &res_addr, tdata,
-					   NULL, NULL);
-	if (status != PJ_SUCCESS) {
-	    app_perror("Error forwarding response", status);
-	    return PJ_TRUE;
+    return PJ_TRUE;
+}
+
+
+/* Callback to be called to handle transaction state changed. */
+static void tu_on_tsx_state(pjsip_transaction *tsx, pjsip_event *event)
+{
+    struct uac_data *uac_data;
+    pj_status_t status;
+
+    if (tsx->role == PJSIP_ROLE_UAS) {
+	if (tsx->state == PJSIP_TSX_STATE_TERMINATED) {
+	    struct uas_data *uas_data;
+
+	    uas_data = (struct uas_data*) tsx->mod_data[mod_tu.id];
+	    if (uas_data->uac_tsx) {
+		uac_data = (struct uac_data*)
+			   uas_data->uac_tsx->mod_data[mod_tu.id];
+		uac_data->uas_tsx = NULL;
+	    }
+		       
 	}
-    } else {
-	struct tsx_data *tsx_data;
+	return;
+    }
 
-	tsx_data = (struct tsx_data*) uac_tsx->mod_data[mod_stateful_proxy.id];
+    /* Get the data that we attached to the UAC transaction previously */
+    uac_data = (struct uac_data*) tsx->mod_data[mod_tu.id];
 
-	/* Forward response with the UAS transaction */
-	pjsip_tsx_send_msg(tsx_data->uas_tsx, tdata);
 
-	/* Special case for pjsip:
-	 * if response is 2xx for INVITE transaction, terminate the UAS
-	 * transaction (otherwise it will retransmit the response).
+    /* Handle incoming response */
+    if (event->body.tsx_state.type == PJSIP_EVENT_RX_MSG) {
+
+	pjsip_rx_data *rdata;
+	pjsip_response_addr res_addr;
+        pjsip_via_hdr *hvia;
+	pjsip_tx_data *tdata;
+
+	rdata = event->body.tsx_state.src.rdata;
+
+	/* Do not forward 100 response for INVITE (we already responded
+	 * INVITE with 100)
 	 */
-	if (tsx_data->uas_tsx->method.id == PJSIP_INVITE_METHOD &&
-	    rdata->msg_info.msg->line.status.code/100 == 2)
+	if (tsx->method.id == PJSIP_INVITE_METHOD && 
+	    rdata->msg_info.msg->line.status.code == 100)
 	{
-	    pjsip_tsx_terminate(tsx_data->uas_tsx,
-				rdata->msg_info.msg->line.status.code);
-	    tsx_data->uas_tsx = NULL;
+	    return;
 	}
+
+	/* Create response to be forwarded upstream 
+	 * (Via will be stripped here) 
+	 */
+	status = pjsip_endpt_create_response_fwd(global.endpt, rdata, 0, 
+						 &tdata);
+	if (status != PJ_SUCCESS) {
+	    app_perror("Error creating response", status);
+	    return;
+	}
+
+	/* Get topmost Via header of the new response */
+	hvia = (pjsip_via_hdr*) pjsip_msg_find_hdr(tdata->msg, PJSIP_H_VIA, 
+						   NULL);
+	if (hvia == NULL) {
+	    /* Invalid response! Just drop it */
+	    pjsip_tx_data_dec_ref(tdata);
+	    return;
+	}
+
+	/* Calculate the address to forward the response */
+	pj_bzero(&res_addr, sizeof(res_addr));
+	res_addr.dst_host.type = PJSIP_TRANSPORT_UDP;
+	res_addr.dst_host.flag = 
+	    pjsip_transport_get_flag_from_type(PJSIP_TRANSPORT_UDP);
+
+	/* Destination address is Via's received param */
+	res_addr.dst_host.addr.host = hvia->recvd_param;
+	if (res_addr.dst_host.addr.host.slen == 0) {
+	    /* Someone has messed up our Via header! */
+	    res_addr.dst_host.addr.host = hvia->sent_by.host;
+	}
+
+	/* Destination port is the rport */
+	if (hvia->rport_param != 0 && hvia->rport_param != -1)
+	    res_addr.dst_host.addr.port = hvia->rport_param;
+
+	if (res_addr.dst_host.addr.port == 0) {
+	    /* Ugh, original sender didn't put rport!
+	     * At best, can only send the response to the port in Via.
+	     */
+	    res_addr.dst_host.addr.port = hvia->sent_by.port;
+	}
+
+	/* Forward response with the UAS transaction */
+	pjsip_tsx_send_msg(uac_data->uas_tsx, tdata);
+
     }
 
-    return PJ_TRUE;
+    /* If UAC transaction is terminated, terminate the UAS as well.
+     * This could happen because of:
+     *	- timeout on the UAC side
+     *  - receipt of 2xx response to INVITE
+     */
+    if (tsx->state == PJSIP_TSX_STATE_TERMINATED && uac_data->uas_tsx) {
+
+	pjsip_transaction *uas_tsx;
+	struct uas_data *uas_data;
+
+	uas_tsx = uac_data->uas_tsx;
+	uas_data = (struct uas_data*) uas_tsx->mod_data[mod_tu.id];
+	uas_data->uac_tsx = NULL;
+
+	if (event->body.tsx_state.type == PJSIP_EVENT_TIMER) {
+
+	    /* Send 408/Timeout if this is an INVITE transaction, since
+	     * we must have sent provisional response before. For non
+	     * INVITE transaction, just destroy it.
+	     */
+	    if (tsx->method.id == PJSIP_INVITE_METHOD) {
+
+		pjsip_tx_data *tdata = uas_tsx->last_tx;
+
+		tdata->msg->line.status.code = PJSIP_SC_REQUEST_TIMEOUT;
+		tdata->msg->line.status.reason = pj_str("Request timed out");
+		tdata->msg->body = NULL;
+
+		pjsip_tx_data_add_ref(tdata);
+		pjsip_tx_data_invalidate_msg(tdata);
+
+		pjsip_tsx_send_msg(uas_tsx, tdata);
+
+	    } else {
+		/* For non-INVITE, just destroy the UAS transaction */
+		pjsip_tsx_terminate(uas_tsx, PJSIP_SC_REQUEST_TIMEOUT);
+	    }
+
+	} else if (event->body.tsx_state.type == PJSIP_EVENT_RX_MSG) {
+
+	    if (uas_tsx->state < PJSIP_TSX_STATE_TERMINATED) {
+		pjsip_msg *msg;
+		int code;
+
+		msg = event->body.tsx_state.src.rdata->msg_info.msg;
+		code = msg->line.status.code;
+
+		uac_data->uas_tsx = NULL;
+		pjsip_tsx_terminate(uas_tsx, code);
+	    }
+	}
+    }
 }
 
 
@@ -279,12 +510,12 @@ int main(int argc, char *argv[])
     global.port = 5060;
     global.record_route = 0;
 
+    pj_log_set_level(4);
+
     status = init_options(argc, argv);
     if (status != PJ_SUCCESS)
 	return 1;
 
-    pj_log_set_level(4);
-
     status = init_stack();
     if (status != PJ_SUCCESS) {
 	app_perror("Error initializing stack", status);
diff --git a/pjsip-apps/src/samples/stateless_proxy.c b/pjsip-apps/src/samples/stateless_proxy.c
index 8e3e703f..f40b263c 100644
--- a/pjsip-apps/src/samples/stateless_proxy.c
+++ b/pjsip-apps/src/samples/stateless_proxy.c
@@ -34,19 +34,19 @@ static pj_status_t init_stateless_proxy(void)
 {
     static pjsip_module mod_stateless_proxy =
     {
-	NULL, NULL,		        /* prev, next.		*/
-	{ "mod-stateless-proxy", 19 },	/* Name.		*/
-	-1,			        /* Id			*/
-	PJSIP_MOD_PRIORITY_APPLICATION, /* Priority		*/
-	NULL,				/* load()		*/
-	NULL,				/* start()		*/
-	NULL,				/* stop()		*/
-	NULL,				/* unload()		*/
-	&on_rx_request,			/* on_rx_request()	*/
-	&on_rx_response,	        /* on_rx_response()	*/
-	NULL,				/* on_tx_request.	*/
-	NULL,				/* on_tx_response()	*/
-	NULL,				/* on_tsx_state()	*/
+	NULL, NULL,			    /* prev, next.	*/
+	{ "mod-stateless-proxy", 19 },	    /* Name.		*/
+	-1,				    /* Id		*/
+	PJSIP_MOD_PRIORITY_UA_PROXY_LAYER,  /* Priority		*/
+	NULL,				    /* load()		*/
+	NULL,				    /* start()		*/
+	NULL,				    /* stop()		*/
+	NULL,				    /* unload()		*/
+	&on_rx_request,			    /* on_rx_request()	*/
+	&on_rx_response,		    /* on_rx_response()	*/
+	NULL,				    /* on_tx_request.	*/
+	NULL,				    /* on_tx_response()	*/
+	NULL,				    /* on_tsx_state()	*/
     };
 
     pj_status_t status;
@@ -178,13 +178,12 @@ int main(int argc, char *argv[])
     pj_status_t status;
 
     global.port = 5060;
+    pj_log_set_level(4);
 
     status = init_options(argc, argv);
     if (status != PJ_SUCCESS)
 	return 1;
 
-    pj_log_set_level(4);
-
     status = init_stack();
     if (status != PJ_SUCCESS) {
 	app_perror("Error initializing stack", status);