.. _config_udp_listener_filters_udp_proxy: UDP proxy ========= * :ref:`v3 API reference ` * This filter should be configured with the name *envoy.filters.udp_listener.udp_proxy* Overview -------- The UDP proxy listener filter allows Envoy to operate as a *non-transparent* proxy between a UDP client and server. The lack of transparency means that the upstream server will see the source IP and port of the Envoy instance versus the client. All datagrams flow from the client, to Envoy, to the upstream server, back to Envoy, and back to the client. Because UDP is not a connection oriented protocol, Envoy must keep track of a client's *session* such that the response datagrams from an upstream server can be routed back to the correct client. Each session is index by the 4-tuple consisting of source IP/port and local IP/port that the datagram is received on. Sessions last until the :ref:`idle timeout ` is reached. The UDP proxy listener filter also can operate as a *transparent* proxy if the :ref:`use_original_src_ip ` field is set. But please keep in mind that it does not forward the port to upstreams. It forwards only the IP address to upstreams. Load balancing and unhealthy host handling ------------------------------------------ Envoy will fully utilize the configured load balancer for the configured upstream cluster when load balancing UDP datagrams. When a new session is created, Envoy will associate the session with an upstream host selected using the configured load balancer. All future datagrams that belong to the session will be routed to the same upstream host. When an upstream host becomes unhealthy (due to :ref:`active health checking `), Envoy will attempt to create a new session to a healthy host when the next datagram is received. Circuit breaking ---------------- The number of sessions that can be created per upstream cluster is limited by the cluster's :ref:`maximum connection circuit breaker `. By default this is 1024. Example configuration --------------------- The following example configuration will cause Envoy to listen on UDP port 1234 and proxy to a UDP server listening on port 1235, allowing 9000 byte packets in both directions (i.e., either jumbo frames or fragmented IP packets). .. literalinclude:: _include/udp-proxy.yaml :language: yaml .. _config_udp_listener_filters_udp_proxy_stats: Statistics ---------- The UDP proxy filter emits both its own downstream statistics as well as many of the :ref:`cluster upstream statistics ` where applicable. The downstream statistics are rooted at *udp..* with the following statistics: .. csv-table:: :header: Name, Type, Description :widths: 1, 1, 2 downstream_sess_no_route, Counter, Number of datagrams not routed due to no cluster downstream_sess_rx_bytes, Counter, Number of bytes received downstream_sess_rx_datagrams, Counter, Number of datagrams received downstream_sess_rx_errors, Counter, Number of datagram receive errors downstream_sess_total, Counter, Number sessions created in total downstream_sess_tx_bytes, Counter, Number of bytes transmitted downstream_sess_tx_datagrams, Counter, Number of datagrams transmitted downstream_sess_tx_errors, counter, Number of datagram transmission errors idle_timeout, Counter, Number of sessions destroyed due to idle timeout downstream_sess_active, Gauge, Number of sessions currently active The following standard :ref:`upstream cluster stats ` are used by the UDP proxy: .. csv-table:: :header: Name, Type, Description :widths: 1, 1, 2 upstream_cx_none_healthy, Counter, Number of datagrams dropped due to no healthy hosts upstream_cx_overflow, Counter, Number of datagrams dropped due to hitting the session circuit breaker upstream_cx_rx_bytes_total, Counter, Number of bytes received upstream_cx_tx_bytes_total, Counter, Number of bytes transmitted The UDP proxy filter also emits custom upstream cluster stats prefixed with *cluster..udp.*: .. csv-table:: :header: Name, Type, Description :widths: 1, 1, 2 sess_rx_datagrams, Counter, Number of datagrams received sess_rx_datagrams_dropped, Counter, Number of datagrams dropped due to kernel overflow or truncation sess_rx_errors, Counter, Number of datagram receive errors sess_tx_datagrams, Counter, Number of datagrams transmitted sess_tx_errors, Counter, Number of datagrams transmitted