--- a/src/http/modules/ngx_http_flv_module.c
+++ b/src/http/modules/ngx_http_flv_module.c
@@ -194,6 +194,10 @@ ngx_http_flv_handler(ngx_http_request_t 
     r->headers_out.content_length_n = len;
     r->headers_out.last_modified_time = of.mtime;
 
+    if (ngx_http_set_etag(r) != NGX_OK) {
+        return NGX_HTTP_INTERNAL_SERVER_ERROR;
+    }
+
     if (ngx_http_set_content_type(r) != NGX_OK) {
         return NGX_HTTP_INTERNAL_SERVER_ERROR;
     }

--- a/src/http/modules/ngx_http_gzip_static_module.c
+++ b/src/http/modules/ngx_http_gzip_static_module.c
@@ -207,6 +207,10 @@ ngx_http_gzip_static_handler(ngx_http_re
     r->headers_out.content_length_n = of.size;
     r->headers_out.last_modified_time = of.mtime;
 
+    if (ngx_http_set_etag(r) != NGX_OK) {
+        return NGX_HTTP_INTERNAL_SERVER_ERROR;
+    }
+
     if (ngx_http_set_content_type(r) != NGX_OK) {
         return NGX_HTTP_INTERNAL_SERVER_ERROR;
     }

--- a/src/http/modules/ngx_http_mp4_module.c
+++ b/src/http/modules/ngx_http_mp4_module.c
@@ -586,6 +586,10 @@ ngx_http_mp4_handler(ngx_http_request_t 
     r->headers_out.status = NGX_HTTP_OK;
     r->headers_out.last_modified_time = of.mtime;
 
+    if (ngx_http_set_etag(r) != NGX_OK) {
+        return NGX_HTTP_INTERNAL_SERVER_ERROR;
+    }
+
     if (ngx_http_set_content_type(r) != NGX_OK) {
         return NGX_HTTP_INTERNAL_SERVER_ERROR;
     }

--- a/src/http/modules/ngx_http_static_module.c
+++ b/src/http/modules/ngx_http_static_module.c
@@ -220,6 +220,10 @@ ngx_http_static_handler(ngx_http_request
     r->headers_out.content_length_n = of.size;
     r->headers_out.last_modified_time = of.mtime;
 
+    if (ngx_http_set_etag(r) != NGX_OK) {
+        return NGX_HTTP_INTERNAL_SERVER_ERROR;
+    }
+
     if (ngx_http_set_content_type(r) != NGX_OK) {
         return NGX_HTTP_INTERNAL_SERVER_ERROR;
     }

--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -1809,6 +1809,35 @@ ngx_http_set_exten(ngx_http_request_t *r
 
 
 ngx_int_t
+ngx_http_set_etag(ngx_http_request_t *r)
+{
+    ngx_table_elt_t  *etag;
+
+    etag = ngx_list_push(&r->headers_out.headers);
+    if (etag == NULL) {
+        return NGX_ERROR;
+    }
+
+    etag->hash = 1;
+    ngx_str_set(&etag->key, "ETag");
+
+    etag->value.data = ngx_pnalloc(r->pool, NGX_OFF_T_LEN + NGX_TIME_T_LEN + 3);
+    if (etag->value.data == NULL) {
+        return NGX_ERROR;
+    }
+
+    etag->value.len = ngx_sprintf(etag->value.data, "\"%xT-%xO\"",
+                                  r->headers_out.last_modified_time,
+                                  r->headers_out.content_length_n)
+                      - etag->value.data;
+
+    r->headers_out.etag = etag;
+
+    return NGX_OK;
+}
+
+
+ngx_int_t
 ngx_http_send_response(ngx_http_request_t *r, ngx_uint_t status,
     ngx_str_t *ct, ngx_http_complex_value_t *cv)
 {

--- a/src/http/ngx_http_core_module.h
+++ b/src/http/ngx_http_core_module.h
@@ -480,6 +480,7 @@ ngx_int_t ngx_http_core_content_phase(ng
 void *ngx_http_test_content_type(ngx_http_request_t *r, ngx_hash_t *types_hash);
 ngx_int_t ngx_http_set_content_type(ngx_http_request_t *r);
 void ngx_http_set_exten(ngx_http_request_t *r);
+ngx_int_t ngx_http_set_etag(ngx_http_request_t *r);
 ngx_int_t ngx_http_send_response(ngx_http_request_t *r, ngx_uint_t status,
     ngx_str_t *ct, ngx_http_complex_value_t *cv);
 u_char *ngx_http_map_uri_to_path(ngx_http_request_t *r, ngx_str_t *name,