modules: enable measuring RTT for xdp-tcp

src/knot/include/module.h

-/*  Copyright (C) 2021 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+/*  Copyright (C) 2022 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -404,6 +404,7 @@ typedef struct {
 	unsigned thread_id;                    /*!< Current thread id. */
 	void *server;                          /*!< Server object private item. */
 	const struct knot_xdp_msg *xdp_msg;    /*!< Possible XDP message context. */
+	const struct knot_tcp_conn *xdp_conn;  /*!< Possible XDP TCP connection context. */
 } knotd_qdata_params_t;
 
 /*! Query processing data context. */
@@ -446,6 +447,15 @@ const struct sockaddr_storage *knotd_qdata_local_addr(knotd_qdata_t *qdata,
  */
 const struct sockaddr_storage *knotd_qdata_remote_addr(knotd_qdata_t *qdata);
 
+/*!
+ * Gets the measured TCP round-trip-time.
+ *
+ * \param[in] qdata  Query data.
+ *
+ * \return RTT in microseconds or 0 if error or not available.
+ */
+uint32_t knotd_qdata_rtt(knotd_qdata_t *qdata);
+
 /*!
  * Gets the current zone name.
  *

src/knot/modules/probe/probe.c

-/*  Copyright (C) 2021 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+/*  Copyright (C) 2022 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -97,9 +97,7 @@ static knotd_state_t export(knotd_state_t state, knot_pkt_t *pkt,
 	knot_probe_data_t d;
 	int ret = knot_probe_data_set(&d, proto, local, remote, qdata->query, reply, rcode);
 	if (ret == KNOT_EOK) {
-		if (tcp && qdata->params->xdp_msg == NULL) {
-			d.tcp_rtt = knot_probe_tcp_rtt(qdata->params->socket);
-		}
+		d.tcp_rtt = knotd_qdata_rtt(qdata);
 		if (qdata->query->opt_rr != NULL) {
 			d.reply.ede = qdata->rcode_ede;
 		}

src/knot/nameserver/query_module.c

-/*  Copyright (C) 2021 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+/*  Copyright (C) 2022 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -22,6 +22,7 @@
 
 #include "contrib/sockaddr.h"
 #include "libknot/attribute.h"
+#include "libknot/probe/data.h"
 #include "libknot/xdp.h"
 #include "knot/common/log.h"
 #include "knot/conf/module.h"
@@ -661,6 +662,26 @@ const struct sockaddr_storage *knotd_qdata_remote_addr(knotd_qdata_t *qdata)
 	}
 }
 
+_public_
+uint32_t knotd_qdata_rtt(knotd_qdata_t *qdata)
+{
+	if (qdata == NULL ||
+	    (qdata->params->flags & KNOTD_QUERY_FLAG_LIMIT_SIZE)) { // not TCP
+		return 0;
+	}
+
+	if (qdata->params->xdp_msg != NULL) {
+#ifdef ENABLE_XDP
+		return qdata->params->xdp_conn->establish_rtt;
+#else
+		assert(0);
+		return 0;
+#endif
+	} else {
+		return knot_probe_tcp_rtt(qdata->params->socket);
+	}
+}
+
 _public_
 const knot_dname_t *knotd_qdata_zone_name(knotd_qdata_t *qdata)
 {

src/knot/server/xdp-handler.c

@@ -201,6 +201,7 @@ static void handle_tcp(xdp_handle_ctx_t *ctx, knot_layer_t *layer,
 		for (size_t j = 0; j < rl->inbufs_count; j++) {
 			// Consume the query.
 			handle_init(params, layer, rl->msg, &rl->inbufs[j]);
+			params->xdp_conn = rl->conn;
 
 			// Process the reply.
 			knot_pkt_t *ans = knot_pkt_new(ans_buf, sizeof(ans_buf), layer->mm);

src/libknot/xdp/tcp.c

@@ -233,7 +233,12 @@ int knot_tcp_recv(knot_tcp_relay_t *relays, knot_xdp_msg_t *msgs, uint32_t count
 			memcpy(conn->last_eth_loc, msg->eth_to, sizeof(conn->last_eth_loc));
 			conn->window_size = (uint32_t)msg->win * (1LU << conn->window_scale);
 
-			conn->last_active = get_timestamp();
+			uint32_t now = get_timestamp();
+			if (conn->establish_rtt == 0 && conn->last_active != 0) {
+				conn->establish_rtt = now - conn->last_active;
+			}
+			conn->last_active = now;
+
 			rem_node(tcp_conn_node(conn));
 			add_tail(tcp_table_timeout(tcp_table), tcp_conn_node(conn));
 
@@ -304,6 +309,7 @@ int knot_tcp_recv(knot_tcp_relay_t *relays, knot_xdp_msg_t *msgs, uint32_t count
 					break;
 				case XDP_TCP_ESTABLISHING:
 					conn->state = XDP_TCP_NORMAL;
+					relay->action = XDP_TCP_ESTABLISH;
 					break;
 				case XDP_TCP_CLOSING2:
 					tcp_table_del(pconn, tcp_table);

src/libknot/xdp/tcp.h

@@ -71,6 +71,7 @@ typedef struct knot_tcp_conn {
 	uint32_t acked;
 	uint32_t window_size;
 	uint32_t last_active;
+	uint32_t establish_rtt;
 	knot_tcp_state_t state;
 	struct iovec inbuf;
 	tcp_outbufs_t outbufs;

tests/libknot/test_xdp_tcp.c

@@ -440,6 +440,8 @@ void test_ibufs_size(void)
 	for (int i = 0; i < CONNS; i++) {
 		msgs[i].flags = KNOT_XDP_MSG_TCP | KNOT_XDP_MSG_ACK;
 	}
+	fix_seqacks(msgs, CONNS);
+	(void)knot_tcp_recv(rls, msgs, CONNS, test_table, NULL);
 
 	is_int(0, test_table->inbufs_total, "inbufs: initial total zero");