Basic implementation of TCP over XDP for Knot server

including connection handling for kxdpgun in TCP mode.

The implementation is not perfect!! But the interface with other Knot parts is stable.

src/libknot/xdp/tcp.c

@@ -239,6 +239,34 @@ int knot_xdp_tcp_relay(knot_xdp_socket_t *socket, knot_xdp_msg_t msgs[], uint32_
 
 		knot_tcp_relay_t relay = { .msg = msg, .conn = *conn };
 
+		// process incomming data
+		if (seq_ack_match && (msg->flags & KNOT_XDP_MSG_ACK) && msg->payload.iov_len > 0) {
+			resp_ack(msg, KNOT_XDP_MSG_ACK);
+			relay.action = XDP_TCP_DATA;
+
+			struct iovec msg_payload = msg->payload, tofree;
+			ret = knot_tcp_input_buffers(&(*conn)->inbuf, &msg_payload, &tofree);
+
+			if (tofree.iov_len > 0 && ret == KNOT_EOK) {
+				relay.data.iov_base = tofree.iov_base + sizeof(uint16_t);
+				relay.data.iov_len = tofree.iov_len - sizeof(uint16_t);
+				relay.free_data = XDP_TCP_FREE_PREFIX;
+				tcp_relay_dynarray_add(relays, &relay);
+				relay.free_data = XDP_TCP_FREE_NONE;
+			}
+			while (msg_payload.iov_len > 0 && ret == KNOT_EOK) {
+				size_t dns_len = knot_tcp_pay_len(&msg_payload);
+				assert(dns_len >= msg_payload.iov_len);
+				relay.data.iov_base = msg_payload.iov_base + sizeof(uint16_t);
+				relay.data.iov_len = dns_len - sizeof(uint16_t);
+				tcp_relay_dynarray_add(relays, &relay);
+
+				msg_payload.iov_base += dns_len;
+				msg_payload.iov_len -= dns_len;
+			}
+		}
+
+		// process TCP connection state
 		switch (msg->flags & (KNOT_XDP_MSG_SYN | KNOT_XDP_MSG_ACK |
 		                      KNOT_XDP_MSG_FIN | KNOT_XDP_MSG_RST)) {
 		case KNOT_XDP_MSG_SYN:
@@ -274,34 +302,6 @@ int knot_xdp_tcp_relay(knot_xdp_socket_t *socket, knot_xdp_msg_t msgs[], uint32_
 				// unmatching ACK is ignored, this includes:
 				// - incomming out-of-order data
 				// - ACK of some previous part of outgoing data
-			} else if (msg->payload.iov_len > 0) {
-				resp_ack(msg, KNOT_XDP_MSG_ACK);
-				relay.action = XDP_TCP_DATA;
-
-				struct iovec msg_payload = msg->payload, tofree;
-				ret = knot_tcp_input_buffers(&(*conn)->inbuf, &msg_payload, &tofree);
-
-				if (tofree.iov_len > 0 && ret == KNOT_EOK) {
-					FILE *f = fopen("/tmp/ddns.bin", "w");
-					fwrite(tofree.iov_base, tofree.iov_len, 1, f);
-					fclose(f);
-
-					relay.data.iov_base = tofree.iov_base + sizeof(uint16_t);
-					relay.data.iov_len = tofree.iov_len - sizeof(uint16_t);
-					relay.free_data = XDP_TCP_FREE_PREFIX;
-					tcp_relay_dynarray_add(relays, &relay);
-					relay.free_data = XDP_TCP_FREE_NONE;
-				}
-				while (msg_payload.iov_len > 0 && ret == KNOT_EOK) {
-					size_t dns_len = knot_tcp_pay_len(&msg_payload);
-					assert(dns_len >= msg_payload.iov_len);
-					relay.data.iov_base = msg_payload.iov_base + sizeof(uint16_t);
-					relay.data.iov_len = dns_len - sizeof(uint16_t);
-					tcp_relay_dynarray_add(relays, &relay);
-
-					msg_payload.iov_base += dns_len;
-					msg_payload.iov_len -= dns_len;
-				}
 			} else {
 				switch ((*conn)->state) {
 				case XDP_TCP_NORMAL:
@@ -324,7 +324,7 @@ int knot_xdp_tcp_relay(knot_xdp_socket_t *socket, knot_xdp_msg_t msgs[], uint32_
 					relay.action = XDP_TCP_CLOSE;
 					tcp_relay_dynarray_add(relays, &relay);
 					tcp_table_del2(conn, tcp_table);
-				} else {
+				} else if (msg->payload.iov_len == 0) { // otherwise ignore FIN
 					resp_ack(msg, KNOT_XDP_MSG_FIN | KNOT_XDP_MSG_ACK);
 					relay.action = XDP_TCP_CLOSE;
 					tcp_relay_dynarray_add(relays, &relay);