Stream: udp streams. Previously, only one client packet could be processed in a udp stream session even though multiple response packets were supported. Now multiple packets coming from the same client address and port are delivered to the same stream session. If it's required to maintain a single stream of data, nginx should be configured in a way that all packets from a client are delivered to the same worker. On Linux and DragonFly BSD the "reuseport" parameter should be specified for this. Other systems do not currently provide appropriate mechanisms. For these systems a single stream of udp packets is only guaranteed in single-worker configurations. The proxy_response directive now specifies how many packets are expected in response to a single client packet.

--- a/src/core/ngx_connection.h
+++ b/src/core/ngx_connection.h
@@ -51,6 +51,9 @@ struct ngx_listening_s {
     ngx_listening_t    *previous;
     ngx_connection_t   *connection;
 
+    ngx_rbtree_t        rbtree;
+    ngx_rbtree_node_t   sentinel;
+
     ngx_uint_t          worker;
 
     unsigned            open:1;
@@ -151,6 +154,8 @@ struct ngx_connection_s {
     ngx_ssl_connection_t  *ssl;
 #endif
 
+    ngx_udp_connection_t  *udp;
+
     struct sockaddr    *local_sockaddr;
     socklen_t           local_socklen;