new file mode 100644
--- /dev/null
+++ b/src/stream/ngx_stream_upstream_round_robin.h
@@ -0,0 +1,138 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ * Copyright (C) Nginx, Inc.
+ */
+
+
+#ifndef _NGX_STREAM_UPSTREAM_ROUND_ROBIN_H_INCLUDED_
+#define _NGX_STREAM_UPSTREAM_ROUND_ROBIN_H_INCLUDED_
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_stream.h>
+
+
+typedef struct ngx_stream_upstream_rr_peer_s   ngx_stream_upstream_rr_peer_t;
+
+struct ngx_stream_upstream_rr_peer_s {
+    struct sockaddr                 *sockaddr;
+    socklen_t                        socklen;
+    ngx_str_t                        name;
+    ngx_str_t                        server;
+
+    ngx_int_t                        current_weight;
+    ngx_int_t                        effective_weight;
+    ngx_int_t                        weight;
+
+    ngx_uint_t                       conns;
+
+    ngx_uint_t                       fails;
+    time_t                           accessed;
+    time_t                           checked;
+
+    ngx_uint_t                       max_fails;
+    time_t                           fail_timeout;
+
+    ngx_uint_t                       down;         /* unsigned  down:1; */
+
+#if (NGX_STREAM_SSL)
+    void                            *ssl_session;
+    int                              ssl_session_len;
+#endif
+
+    ngx_stream_upstream_rr_peer_t   *next;
+
+#if (NGX_STREAM_UPSTREAM_ZONE)
+    ngx_atomic_t                     lock;
+#endif
+};
+
+
+typedef struct ngx_stream_upstream_rr_peers_s  ngx_stream_upstream_rr_peers_t;
+
+struct ngx_stream_upstream_rr_peers_s {
+    ngx_uint_t                       number;
+
+#if (NGX_STREAM_UPSTREAM_ZONE)
+    ngx_slab_pool_t                 *shpool;
+    ngx_atomic_t                     rwlock;
+#endif
+
+    ngx_uint_t                       total_weight;
+
+    unsigned                         single:1;
+    unsigned                         weighted:1;
+
+    ngx_str_t                       *name;
+
+    ngx_stream_upstream_rr_peers_t  *next;
+
+    ngx_stream_upstream_rr_peer_t   *peer;
+};
+
+
+#if (NGX_STREAM_UPSTREAM_ZONE)
+
+#define ngx_stream_upstream_rr_peers_rlock(peers)                             \
+                                                                              \
+    if (peers->shpool) {                                                      \
+        ngx_rwlock_rlock(&peers->rwlock);                                     \
+    }
+
+#define ngx_stream_upstream_rr_peers_wlock(peers)                             \
+                                                                              \
+    if (peers->shpool) {                                                      \
+        ngx_rwlock_wlock(&peers->rwlock);                                     \
+    }
+
+#define ngx_stream_upstream_rr_peers_unlock(peers)                            \
+                                                                              \
+    if (peers->shpool) {                                                      \
+        ngx_rwlock_unlock(&peers->rwlock);                                    \
+    }
+
+
+#define ngx_stream_upstream_rr_peer_lock(peers, peer)                         \
+                                                                              \
+    if (peers->shpool) {                                                      \
+        ngx_rwlock_wlock(&peer->lock);                                        \
+    }
+
+#define ngx_stream_upstream_rr_peer_unlock(peers, peer)                       \
+                                                                              \
+    if (peers->shpool) {                                                      \
+        ngx_rwlock_unlock(&peer->lock);                                       \
+    }
+
+#else
+
+#define ngx_stream_upstream_rr_peers_rlock(peers)
+#define ngx_stream_upstream_rr_peers_wlock(peers)
+#define ngx_stream_upstream_rr_peers_unlock(peers)
+#define ngx_stream_upstream_rr_peer_lock(peers, peer)
+#define ngx_stream_upstream_rr_peer_unlock(peers, peer)
+
+#endif
+
+
+typedef struct {
+    ngx_stream_upstream_rr_peers_t  *peers;
+    ngx_stream_upstream_rr_peer_t   *current;
+    uintptr_t                       *tried;
+    uintptr_t                        data;
+} ngx_stream_upstream_rr_peer_data_t;
+
+
+ngx_int_t ngx_stream_upstream_init_round_robin(ngx_conf_t *cf,
+    ngx_stream_upstream_srv_conf_t *us);
+ngx_int_t ngx_stream_upstream_init_round_robin_peer(ngx_stream_session_t *s,
+    ngx_stream_upstream_srv_conf_t *us);
+ngx_int_t ngx_stream_upstream_get_round_robin_peer(ngx_peer_connection_t *pc,
+    void *data);
+void ngx_stream_upstream_free_round_robin_peer(ngx_peer_connection_t *pc,
+    void *data, ngx_uint_t state);
+
+
+#endif /* _NGX_STREAM_UPSTREAM_ROUND_ROBIN_H_INCLUDED_ */