new file mode 100644
--- /dev/null
+++ b/src/stream/ngx_stream_write_filter_module.c
@@ -0,0 +1,273 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ * Copyright (C) Nginx, Inc.
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_stream.h>
+
+
+typedef struct {
+    ngx_chain_t  *from_upstream;
+    ngx_chain_t  *from_downstream;
+} ngx_stream_write_filter_ctx_t;
+
+
+static ngx_int_t ngx_stream_write_filter(ngx_stream_session_t *s,
+    ngx_chain_t *in, ngx_uint_t from_upstream);
+static ngx_int_t ngx_stream_write_filter_init(ngx_conf_t *cf);
+
+
+static ngx_stream_module_t  ngx_stream_write_filter_module_ctx = {
+    NULL,                                  /* preconfiguration */
+    ngx_stream_write_filter_init,          /* postconfiguration */
+
+    NULL,                                  /* create main configuration */
+    NULL,                                  /* init main configuration */
+
+    NULL,                                  /* create server configuration */
+    NULL                                   /* merge server configuration */
+};
+
+
+ngx_module_t  ngx_stream_write_filter_module = {
+    NGX_MODULE_V1,
+    &ngx_stream_write_filter_module_ctx,   /* module context */
+    NULL,                                  /* module directives */
+    NGX_STREAM_MODULE,                     /* module type */
+    NULL,                                  /* init master */
+    NULL,                                  /* init module */
+    NULL,                                  /* init process */
+    NULL,                                  /* init thread */
+    NULL,                                  /* exit thread */
+    NULL,                                  /* exit process */
+    NULL,                                  /* exit master */
+    NGX_MODULE_V1_PADDING
+};
+
+
+static ngx_int_t
+ngx_stream_write_filter(ngx_stream_session_t *s, ngx_chain_t *in,
+    ngx_uint_t from_upstream)
+{
+    off_t                           size;
+    ngx_uint_t                      last, flush, sync;
+    ngx_chain_t                    *cl, *ln, **ll, **out, *chain;
+    ngx_connection_t               *c;
+    ngx_stream_write_filter_ctx_t  *ctx;
+
+    ctx = ngx_stream_get_module_ctx(s, ngx_stream_write_filter_module);
+
+    if (ctx == NULL) {
+        ctx = ngx_pcalloc(s->connection->pool,
+                          sizeof(ngx_stream_write_filter_ctx_t));
+        if (ctx == NULL) {
+            return NGX_ERROR;
+        }
+
+        ngx_stream_set_ctx(s, ctx, ngx_stream_write_filter_module);
+    }
+
+    if (from_upstream) {
+        c = s->connection;
+        out = &ctx->from_upstream;
+
+    } else {
+        c = s->upstream->peer.connection;
+        out = &ctx->from_downstream;
+    }
+
+    if (c->error) {
+        return NGX_ERROR;
+    }
+
+    size = 0;
+    flush = 0;
+    sync = 0;
+    last = 0;
+    ll = out;
+
+    /* find the size, the flush point and the last link of the saved chain */
+
+    for (cl = *out; cl; cl = cl->next) {
+        ll = &cl->next;
+
+        ngx_log_debug7(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                       "write old buf t:%d f:%d %p, pos %p, size: %z "
+                       "file: %O, size: %O",
+                       cl->buf->temporary, cl->buf->in_file,
+                       cl->buf->start, cl->buf->pos,
+                       cl->buf->last - cl->buf->pos,
+                       cl->buf->file_pos,
+                       cl->buf->file_last - cl->buf->file_pos);
+
+#if 1
+        if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
+            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+                          "zero size buf in writer "
+                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+                          cl->buf->temporary,
+                          cl->buf->recycled,
+                          cl->buf->in_file,
+                          cl->buf->start,
+                          cl->buf->pos,
+                          cl->buf->last,
+                          cl->buf->file,
+                          cl->buf->file_pos,
+                          cl->buf->file_last);
+
+            ngx_debug_point();
+            return NGX_ERROR;
+        }
+#endif
+
+        size += ngx_buf_size(cl->buf);
+
+        if (cl->buf->flush || cl->buf->recycled) {
+            flush = 1;
+        }
+
+        if (cl->buf->sync) {
+            sync = 1;
+        }
+
+        if (cl->buf->last_buf) {
+            last = 1;
+        }
+    }
+
+    /* add the new chain to the existent one */
+
+    for (ln = in; ln; ln = ln->next) {
+        cl = ngx_alloc_chain_link(c->pool);
+        if (cl == NULL) {
+            return NGX_ERROR;
+        }
+
+        cl->buf = ln->buf;
+        *ll = cl;
+        ll = &cl->next;
+
+        ngx_log_debug7(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                       "write new buf t:%d f:%d %p, pos %p, size: %z "
+                       "file: %O, size: %O",
+                       cl->buf->temporary, cl->buf->in_file,
+                       cl->buf->start, cl->buf->pos,
+                       cl->buf->last - cl->buf->pos,
+                       cl->buf->file_pos,
+                       cl->buf->file_last - cl->buf->file_pos);
+
+#if 1
+        if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
+            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+                          "zero size buf in writer "
+                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+                          cl->buf->temporary,
+                          cl->buf->recycled,
+                          cl->buf->in_file,
+                          cl->buf->start,
+                          cl->buf->pos,
+                          cl->buf->last,
+                          cl->buf->file,
+                          cl->buf->file_pos,
+                          cl->buf->file_last);
+
+            ngx_debug_point();
+            return NGX_ERROR;
+        }
+#endif
+
+        size += ngx_buf_size(cl->buf);
+
+        if (cl->buf->flush || cl->buf->recycled) {
+            flush = 1;
+        }
+
+        if (cl->buf->sync) {
+            sync = 1;
+        }
+
+        if (cl->buf->last_buf) {
+            last = 1;
+        }
+    }
+
+    *ll = NULL;
+
+    ngx_log_debug3(NGX_LOG_DEBUG_STREAM, c->log, 0,
+                   "stream write filter: l:%ui f:%ui s:%O", last, flush, size);
+
+    if (size == 0
+        && !(c->buffered & NGX_LOWLEVEL_BUFFERED)
+        && !(last && c->need_last_buf))
+    {
+        if (last || flush || sync) {
+            for (cl = *out; cl; /* void */) {
+                ln = cl;
+                cl = cl->next;
+                ngx_free_chain(c->pool, ln);
+            }
+
+            *out = NULL;
+            c->buffered &= ~NGX_STREAM_WRITE_BUFFERED;
+
+            return NGX_OK;
+        }
+
+        ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+                      "the stream output chain is empty");
+
+        ngx_debug_point();
+
+        return NGX_ERROR;
+    }
+
+    chain = c->send_chain(c, *out, 0);
+
+    ngx_log_debug1(NGX_LOG_DEBUG_STREAM, c->log, 0,
+                   "stream write filter %p", chain);
+
+    if (chain == NGX_CHAIN_ERROR) {
+        c->error = 1;
+        return NGX_ERROR;
+    }
+
+    for (cl = *out; cl && cl != chain; /* void */) {
+        ln = cl;
+        cl = cl->next;
+        ngx_free_chain(c->pool, ln);
+    }
+
+    *out = chain;
+
+    if (chain) {
+        if (c->shared) {
+            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+                          "shared connection is busy");
+            return NGX_ERROR;
+        }
+
+        c->buffered |= NGX_STREAM_WRITE_BUFFERED;
+        return NGX_AGAIN;
+    }
+
+    c->buffered &= ~NGX_STREAM_WRITE_BUFFERED;
+
+    if (c->buffered & NGX_LOWLEVEL_BUFFERED) {
+        return NGX_AGAIN;
+    }
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_stream_write_filter_init(ngx_conf_t *cf)
+{
+    ngx_stream_top_filter = ngx_stream_write_filter;
+
+    return NGX_OK;
+}