HTTP/2: server push.

Resources to be pushed are configured with the "http2_push" directive.

Also, preload links from the Link response headers, as described in
https://www.w3.org/TR/preload/#server-push-http-2, can be pushed, if
enabled with the "http2_push_preload" directive.

Only relative URIs with absolute paths can be pushed.

The number of concurrent pushes is normally limited by a client, but
cannot exceed a hard limit set by the "http2_max_concurrent_pushes"
directive.

5 files changed, 873 insertions, 18 deletions

diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
index 7a3be13fb..0ee390d51 100644
--- a/src/http/v2/ngx_http_v2.c
+++ b/src/http/v2/ngx_http_v2.c
@@ -35,12 +35,11 @@
 #define NGX_HTTP_V2_GOAWAY_SIZE                  8
 #define NGX_HTTP_V2_WINDOW_UPDATE_SIZE           4
 
-#define NGX_HTTP_V2_STREAM_ID_SIZE               4
-
 #define NGX_HTTP_V2_SETTINGS_PARAM_SIZE          6
 
 /* settings fields */
 #define NGX_HTTP_V2_HEADER_TABLE_SIZE_SETTING    0x1
+#define NGX_HTTP_V2_ENABLE_PUSH_SETTING          0x2
 #define NGX_HTTP_V2_MAX_STREAMS_SETTING          0x3
 #define NGX_HTTP_V2_INIT_WINDOW_SIZE_SETTING     0x4
 #define NGX_HTTP_V2_MAX_FRAME_SIZE_SETTING       0x5
@@ -121,7 +120,7 @@ static ngx_int_t ngx_http_v2_parse_int(ngx_http_v2_connection_t *h2c,
     u_char **pos, u_char *end, ngx_uint_t prefix);
 
 static ngx_http_v2_stream_t *ngx_http_v2_create_stream(
-    ngx_http_v2_connection_t *h2c);
+    ngx_http_v2_connection_t *h2c, ngx_uint_t push);
 static ngx_http_v2_node_t *ngx_http_v2_get_node_by_id(
     ngx_http_v2_connection_t *h2c, ngx_uint_t sid, ngx_uint_t alloc);
 static ngx_http_v2_node_t *ngx_http_v2_get_closed_node(
@@ -162,6 +161,7 @@ static ngx_int_t ngx_http_v2_cookie(ngx_http_request_t *r,
     ngx_http_v2_header_t *header);
 static ngx_int_t ngx_http_v2_construct_cookie_header(ngx_http_request_t *r);
 static void ngx_http_v2_run_request(ngx_http_request_t *r);
+static void ngx_http_v2_run_request_handler(ngx_event_t *ev);
 static ngx_int_t ngx_http_v2_process_request_body(ngx_http_request_t *r,
     u_char *pos, size_t size, ngx_uint_t last);
 static ngx_int_t ngx_http_v2_filter_request_body(ngx_http_request_t *r);
@@ -249,6 +249,8 @@ ngx_http_v2_init(ngx_event_t *rev)
 
     h2scf = ngx_http_get_module_srv_conf(hc->conf_ctx, ngx_http_v2_module);
 
+    h2c->concurrent_pushes = h2scf->concurrent_pushes;
+
     h2c->pool = ngx_create_pool(h2scf->pool_size, h2c->connection->log);
     if (h2c->pool == NULL) {
         ngx_http_close_connection(c);
@@ -366,7 +368,9 @@ ngx_http_v2_read_handler(ngx_event_t *rev)
             break;
         }
 
-        if (n == 0 && (h2c->state.incomplete || h2c->processing)) {
+        if (n == 0
+            && (h2c->state.incomplete || h2c->processing || h2c->pushing))
+        {
             ngx_log_error(NGX_LOG_INFO, c->log, 0,
                           "client prematurely closed connection");
         }
@@ -405,7 +409,7 @@ ngx_http_v2_read_handler(ngx_event_t *rev)
 
     h2c->blocked = 0;
 
-    if (h2c->processing) {
+    if (h2c->processing || h2c->pushing) {
         if (rev->timer_set) {
             ngx_del_timer(rev);
         }
@@ -589,7 +593,7 @@ ngx_http_v2_handle_connection(ngx_http_v2_connection_t *h2c)
     ngx_connection_t        *c;
     ngx_http_v2_srv_conf_t  *h2scf;
 
-    if (h2c->last_out || h2c->processing) {
+    if (h2c->last_out || h2c->processing || h2c->pushing) {
         return;
     }
 
@@ -1123,7 +1127,7 @@ ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos,
         h2c->closed_nodes--;
     }
 
-    stream = ngx_http_v2_create_stream(h2c);
+    stream = ngx_http_v2_create_stream(h2c, 0);
     if (stream == NULL) {
         return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
     }
@@ -1909,6 +1913,11 @@ ngx_http_v2_state_rst_stream(ngx_http_v2_connection_t *h2c, u_char *pos,
                       "client canceled stream %ui", h2c->state.sid);
         break;
 
+    case NGX_HTTP_V2_REFUSED_STREAM:
+        ngx_log_error(NGX_LOG_INFO, fc->log, 0,
+                      "client refused stream %ui", h2c->state.sid);
+        break;
+
     case NGX_HTTP_V2_INTERNAL_ERROR:
         ngx_log_error(NGX_LOG_INFO, fc->log, 0,
                       "client terminated stream %ui due to internal error",
@@ -1966,6 +1975,7 @@ ngx_http_v2_state_settings_params(ngx_http_v2_connection_t *h2c, u_char *pos,
 {
     ssize_t                   window_delta;
     ngx_uint_t                id, value;
+    ngx_http_v2_srv_conf_t   *h2scf;
     ngx_http_v2_out_frame_t  *frame;
 
     window_delta = 0;
@@ -2016,6 +2026,27 @@ ngx_http_v2_state_settings_params(ngx_http_v2_connection_t *h2c, u_char *pos,
             h2c->frame_size = value;
             break;
 
+        case NGX_HTTP_V2_ENABLE_PUSH_SETTING:
+
+            if (value > 1) {
+                ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
+                              "client sent SETTINGS frame with incorrect "
+                              "ENABLE_PUSH value %ui", value);
+
+                return ngx_http_v2_connection_error(h2c,
+                                                    NGX_HTTP_V2_PROTOCOL_ERROR);
+            }
+
+            h2c->push_disabled = !value;
+            break;
+
+        case NGX_HTTP_V2_MAX_STREAMS_SETTING:
+            h2scf = ngx_http_get_module_srv_conf(h2c->http_connection->conf_ctx,
+                                                 ngx_http_v2_module);
+
+            h2c->concurrent_pushes = ngx_min(value, h2scf->concurrent_pushes);
+            break;
+
         default:
             break;
         }
@@ -2483,6 +2514,119 @@ ngx_http_v2_parse_int(ngx_http_v2_connection_t *h2c, u_char **pos, u_char *end,
 }
 
 
+ngx_int_t
+ngx_http_v2_push_stream(ngx_http_v2_connection_t *h2c, ngx_uint_t depend,
+    size_t request_length, ngx_str_t *path, ngx_str_t *authority)
+{
+    ngx_int_t              rc;
+    ngx_str_t              value;
+    ngx_connection_t      *fc;
+    ngx_http_request_t    *r;
+    ngx_http_v2_node_t    *node;
+    ngx_http_v2_stream_t  *stream;
+
+    node = ngx_http_v2_get_node_by_id(h2c, h2c->last_push, 1);
+
+    if (node == NULL) {
+        return NGX_ERROR;
+    }
+
+    if (node->parent) {
+        ngx_queue_remove(&node->reuse);
+        h2c->closed_nodes--;
+    }
+
+    stream = ngx_http_v2_create_stream(h2c, 1);
+    if (stream == NULL) {
+        return NGX_ERROR;
+    }
+
+    stream->pool = ngx_create_pool(1024, h2c->connection->log);
+    if (stream->pool == NULL) {
+        return NGX_ERROR;
+    }
+
+    r = stream->request;
+    fc = r->connection;
+
+    r->request_length = request_length;
+
+    stream->in_closed = 1;
+    stream->node = node;
+
+    node->stream = stream;
+
+    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                   "http2 push stream sid:%ui "
+                   "depends on %ui excl:0 weight:16",
+                   h2c->last_push, depend);
+
+    node->weight = NGX_HTTP_V2_DEFAULT_WEIGHT;
+    ngx_http_v2_set_dependency(h2c, node, depend, 0);
+
+    r->method_name = ngx_http_core_get_method;
+    r->method = NGX_HTTP_GET;
+
+    r->schema_start = (u_char *) "https";
+
+#if (NGX_HTTP_SSL)
+    if (fc->ssl) {
+        r->schema_end = r->schema_start + 5;
+
+    } else
+#endif
+    {
+        r->schema_end = r->schema_start + 4;
+    }
+
+    value.len = authority->len;
+
+    value.data = ngx_pstrdup(stream->pool, authority);
+    if (value.data == NULL) {
+        return NGX_ERROR;
+    }
+
+    rc = ngx_http_v2_parse_authority(r, &value);
+
+    if (rc != NGX_OK) {
+        goto error;
+    }
+
+    value.len = path->len;
+
+    value.data = ngx_pstrdup(stream->pool, path);
+    if (value.data == NULL) {
+        return NGX_ERROR;
+    }
+
+    rc = ngx_http_v2_parse_path(r, &value);
+
+    if (rc != NGX_OK) {
+        goto error;
+    }
+
+    fc->write->handler = ngx_http_v2_run_request_handler;
+    ngx_post_event(fc->write, &ngx_posted_events);
+
+    return NGX_OK;
+
+error:
+
+    if (rc == NGX_ABORT) {
+        return NGX_ERROR;
+    }
+
+    if (rc == NGX_DECLINED) {
+        ngx_http_finalize_request(r, NGX_HTTP_BAD_REQUEST);
+        return NGX_ERROR;
+    }
+
+    (void) ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
+
+    return NGX_ERROR;
+}
+
+
 static ngx_int_t
 ngx_http_v2_send_settings(ngx_http_v2_connection_t *h2c)
 {
@@ -2743,7 +2887,7 @@ ngx_http_v2_frame_handler(ngx_http_v2_connection_t *h2c,
 
 
 static ngx_http_v2_stream_t *
-ngx_http_v2_create_stream(ngx_http_v2_connection_t *h2c)
+ngx_http_v2_create_stream(ngx_http_v2_connection_t *h2c, ngx_uint_t push)
 {
     ngx_log_t                 *log;
     ngx_event_t               *rev, *wev;
@@ -2798,7 +2942,13 @@ ngx_http_v2_create_stream(ngx_http_v2_connection_t *h2c)
     ngx_memcpy(log, h2c->connection->log, sizeof(ngx_log_t));
 
     log->data = ctx;
-    log->action = "reading client request headers";
+
+    if (push) {
+        log->action = "processing pushed request headers";
+
+    } else {
+        log->action = "reading client request headers";
+    }
 
     ngx_memzero(rev, sizeof(ngx_event_t));
 
@@ -2870,7 +3020,12 @@ ngx_http_v2_create_stream(ngx_http_v2_connection_t *h2c)
     stream->send_window = h2c->init_window;
     stream->recv_window = h2scf->preread_size;
 
-    h2c->processing++;
+    if (push) {
+        h2c->pushing++;
+
+    } else {
+        h2c->processing++;
+    }
 
     return stream;
 }
@@ -3532,6 +3687,22 @@ ngx_http_v2_run_request(ngx_http_request_t *r)
 }
 
 
+static void
+ngx_http_v2_run_request_handler(ngx_event_t *ev)
+{
+    ngx_connection_t    *fc;
+    ngx_http_request_t  *r;
+
+    fc = ev->data;
+    r = fc->data;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0,
+                   "http2 run request handler");
+
+    ngx_http_v2_run_request(r);
+}
+
+
 ngx_int_t
 ngx_http_v2_read_request_body(ngx_http_request_t *r)
 {
@@ -4003,6 +4174,7 @@ void
 ngx_http_v2_close_stream(ngx_http_v2_stream_t *stream, ngx_int_t rc)
 {
     ngx_pool_t                *pool;
+    ngx_uint_t                 push;
     ngx_event_t               *ev;
     ngx_connection_t          *fc;
     ngx_http_v2_node_t        *node;
@@ -4011,9 +4183,10 @@ ngx_http_v2_close_stream(ngx_http_v2_stream_t *stream, ngx_int_t rc)
     h2c = stream->connection;
     node = stream->node;
 
-    ngx_log_debug3(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
-                   "http2 close stream %ui, queued %ui, processing %ui",
-                   node->id, stream->queued, h2c->processing);
+    ngx_log_debug4(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                   "http2 close stream %ui, queued %ui, "
+                   "processing %ui, pushing %ui",
+                   node->id, stream->queued, h2c->processing, h2c->pushing);
 
     fc = stream->request->connection;
 
@@ -4069,6 +4242,8 @@ ngx_http_v2_close_stream(ngx_http_v2_stream_t *stream, ngx_int_t rc)
         h2c->state.stream = NULL;
     }
 
+    push = stream->node->id % 2 == 0;
+
     node->stream = NULL;
 
     ngx_queue_insert_tail(&h2c->closed, &node->reuse);
@@ -4116,9 +4291,14 @@ ngx_http_v2_close_stream(ngx_http_v2_stream_t *stream, ngx_int_t rc)
     fc->data = h2c->free_fake_connections;
     h2c->free_fake_connections = fc;
 
-    h2c->processing--;
+    if (push) {
+        h2c->pushing--;
+
+    } else {
+        h2c->processing--;
+    }
 
-    if (h2c->processing || h2c->blocked) {
+    if (h2c->processing || h2c->pushing || h2c->blocked) {
         return;
     }
 
@@ -4267,7 +4447,7 @@ ngx_http_v2_finalize_connection(ngx_http_v2_connection_t *h2c,
 
     c->error = 1;
 
-    if (!h2c->processing) {
+    if (!h2c->processing && !h2c->pushing) {
         ngx_http_close_connection(c);
         return;
     }
@@ -4316,7 +4496,7 @@ ngx_http_v2_finalize_connection(ngx_http_v2_connection_t *h2c,
 
     h2c->blocked = 0;
 
-    if (h2c->processing) {
+    if (h2c->processing || h2c->pushing) {
         return;
     }
 
diff --git a/src/http/v2/ngx_http_v2.h b/src/http/v2/ngx_http_v2.h
index 3926e653b..d4a64a724 100644
--- a/src/http/v2/ngx_http_v2.h
+++ b/src/http/v2/ngx_http_v2.h
@@ -24,6 +24,8 @@
 #define NGX_HTTP_V2_MAX_FIELD                                                 \
     (127 + (1 << (NGX_HTTP_V2_INT_OCTETS - 1) * 7) - 1)
 
+#define NGX_HTTP_V2_STREAM_ID_SIZE       4
+
 #define NGX_HTTP_V2_FRAME_HEADER_SIZE    9
 
 /* frame types */
@@ -118,6 +120,9 @@ struct ngx_http_v2_connection_s {
 
     ngx_uint_t                       processing;
 
+    ngx_uint_t                       pushing;
+    ngx_uint_t                       concurrent_pushes;
+
     size_t                           send_window;
     size_t                           recv_window;
     size_t                           init_window;
@@ -143,12 +148,14 @@ struct ngx_http_v2_connection_s {
     ngx_queue_t                      closed;
 
     ngx_uint_t                       last_sid;
+    ngx_uint_t                       last_push;
 
     unsigned                         closed_nodes:8;
     unsigned                         settings_ack:1;
     unsigned                         table_update:1;
     unsigned                         blocked:1;
     unsigned                         goaway:1;
+    unsigned                         push_disabled:1;
 };
 
 
@@ -276,6 +283,10 @@ void ngx_http_v2_init(ngx_event_t *rev);
 ngx_int_t ngx_http_v2_read_request_body(ngx_http_request_t *r);
 ngx_int_t ngx_http_v2_read_unbuffered_request_body(ngx_http_request_t *r);
 
+ngx_int_t ngx_http_v2_push_stream(ngx_http_v2_connection_t *h2c,
+    ngx_uint_t depend, size_t request_length, ngx_str_t *path,
+    ngx_str_t *authority);
+
 void ngx_http_v2_close_stream(ngx_http_v2_stream_t *stream, ngx_int_t rc);
 
 ngx_int_t ngx_http_v2_send_output_queue(ngx_http_v2_connection_t *h2c);
diff --git a/src/http/v2/ngx_http_v2_filter_module.c b/src/http/v2/ngx_http_v2_filter_module.c
index 9bcf9446b..6878c1d7f 100644
--- a/src/http/v2/ngx_http_v2_filter_module.c
+++ b/src/http/v2/ngx_http_v2_filter_module.c
@@ -2,6 +2,7 @@
 /*
  * Copyright (C) Nginx, Inc.
  * Copyright (C) Valentin V. Bartenev
+ * Copyright (C) Ruslan Ermilov
  */
 
 
@@ -33,6 +34,13 @@
 #define NGX_HTTP_V2_ENCODE_RAW            0
 #define NGX_HTTP_V2_ENCODE_HUFF           0x80
 
+#define NGX_HTTP_V2_AUTHORITY_INDEX       1
+#define NGX_HTTP_V2_METHOD_GET_INDEX      2
+#define NGX_HTTP_V2_PATH_INDEX            4
+
+#define NGX_HTTP_V2_SCHEME_HTTP_INDEX     6
+#define NGX_HTTP_V2_SCHEME_HTTPS_INDEX    7
+
 #define NGX_HTTP_V2_STATUS_INDEX          8
 #define NGX_HTTP_V2_STATUS_200_INDEX      8
 #define NGX_HTTP_V2_STATUS_204_INDEX      9
@@ -53,12 +61,18 @@
 #define NGX_HTTP_V2_NO_TRAILERS           (ngx_http_v2_out_frame_t *) -1
 
 
+static ngx_int_t ngx_http_v2_push_resources(ngx_http_request_t *r);
+static ngx_int_t ngx_http_v2_push_resource(ngx_http_request_t *r,
+    ngx_str_t *path, ngx_str_t *authority);
+
 static u_char *ngx_http_v2_string_encode(u_char *dst, u_char *src, size_t len,
     u_char *tmp, ngx_uint_t lower);
 static u_char *ngx_http_v2_write_int(u_char *pos, ngx_uint_t prefix,
     ngx_uint_t value);
 static ngx_http_v2_out_frame_t *ngx_http_v2_create_headers_frame(
     ngx_http_request_t *r, u_char *pos, u_char *end, ngx_uint_t fin);
+static ngx_http_v2_out_frame_t *ngx_http_v2_create_push_frame(
+    ngx_http_request_t *r, u_char *pos, u_char *end);
 static ngx_http_v2_out_frame_t *ngx_http_v2_create_trailers_frame(
     ngx_http_request_t *r);
 
@@ -81,6 +95,8 @@ static ngx_inline ngx_int_t ngx_http_v2_filter_send(
 
 static ngx_int_t ngx_http_v2_headers_frame_handler(
     ngx_http_v2_connection_t *h2c, ngx_http_v2_out_frame_t *frame);
+static ngx_int_t ngx_http_v2_push_frame_handler(
+    ngx_http_v2_connection_t *h2c, ngx_http_v2_out_frame_t *frame);
 static ngx_int_t ngx_http_v2_data_frame_handler(
     ngx_http_v2_connection_t *h2c, ngx_http_v2_out_frame_t *frame);
 static ngx_inline void ngx_http_v2_handle_frame(
@@ -241,6 +257,15 @@ ngx_http_v2_header_filter(ngx_http_request_t *r)
 
     h2c = stream->connection;
 
+    if (!h2c->push_disabled && !h2c->goaway
+        && stream->node->id % 2 == 1
+        && r->method != NGX_HTTP_HEAD)
+    {
+        if (ngx_http_v2_push_resources(r) != NGX_OK) {
+            return NGX_ERROR;
+        }
+    }
+
     len = h2c->table_update ? 1 : 0;
 
     len += status ? 1 : 1 + ngx_http_v2_literal_size("418");
@@ -638,7 +663,7 @@ ngx_http_v2_header_filter(ngx_http_request_t *r)
 
     ngx_http_v2_queue_blocked_frame(h2c, frame);
 
-    stream->queued = 1;
+    stream->queued++;
 
     cln = ngx_http_cleanup_add(r, 0);
     if (cln == NULL) {
@@ -655,6 +680,365 @@ ngx_http_v2_header_filter(ngx_http_request_t *r)
 }
 
 
+static ngx_int_t
+ngx_http_v2_push_resources(ngx_http_request_t *r)
+{
+    u_char                     *start, *end, *last;
+    ngx_int_t                   rc;
+    ngx_str_t                   path, authority;
+    ngx_uint_t                  i, push;
+    ngx_table_elt_t           **h;
+    ngx_connection_t           *fc;
+    ngx_http_v2_stream_t       *stream;
+    ngx_http_v2_loc_conf_t     *h2lcf;
+    ngx_http_v2_connection_t   *h2c;
+    ngx_http_complex_value_t   *pushes;
+
+    fc = r->connection;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0, "http2 push resources");
+
+    stream = r->stream;
+    h2c = stream->connection;
+
+    ngx_str_null(&authority);
+
+    h2lcf = ngx_http_get_module_loc_conf(r, ngx_http_v2_module);
+
+    if (h2lcf->pushes) {
+        pushes = h2lcf->pushes->elts;
+
+        for (i = 0; i < h2lcf->pushes->nelts; i++) {
+
+            if (ngx_http_complex_value(r, &pushes[i], &path) != NGX_OK) {
+                return NGX_ERROR;
+            }
+
+            if (path.len == 0) {
+                continue;
+            }
+
+            if (path.len == 3 && ngx_strncmp(path.data, "off", 3) == 0) {
+                continue;
+            }
+
+            rc = ngx_http_v2_push_resource(r, &path, &authority);
+
+            if (rc == NGX_ERROR) {
+                return NGX_ERROR;
+            }
+
+            if (rc == NGX_ABORT) {
+                return NGX_OK;
+            }
+
+            /* NGX_OK, NGX_DECLINED */
+        }
+    }
+
+    if (!h2lcf->push_preload) {
+        return NGX_OK;
+    }
+
+    h = r->headers_out.link.elts;
+
+    for (i = 0; i < r->headers_out.link.nelts; i++) {
+
+        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
+                       "http2 parse link: \"%V\"", &h[i]->value);
+
+        start = h[i]->value.data;
+        end = h[i]->value.data + h[i]->value.len;
+
+    next_link:
+
+        while (start < end && *start == ' ') { start++; }
+
+        if (start == end || *start++ != '<') {
+            continue;
+        }
+
+        while (start < end && *start == ' ') { start++; }
+
+        for (last = start; last < end && *last != '>'; last++) {
+            /* void */
+        }
+
+        if (last == start || last == end) {
+            continue;
+        }
+
+        path.len = last - start;
+        path.data = start;
+
+        start = last + 1;
+
+        while (start < end && *start == ' ') { start++; }
+
+        if (start == end) {
+            continue;
+        }
+
+        if (*start == ',') {
+            start++;
+            goto next_link;
+        }
+
+        if (*start++ != ';') {
+            continue;
+        }
+
+        last = ngx_strlchr(start, end, ',');
+
+        if (last == NULL) {
+            last = end;
+        }
+
+        push = 0;
+
+        for ( ;; ) {
+
+            while (start < last && *start == ' ') { start++; }
+
+            if (last - start >= 6
+                && ngx_strncasecmp(start, (u_char *) "nopush", 6) == 0)
+            {
+                start += 6;
+
+                if (start == last || *start == ' ' || *start == ';') {
+                    push = 0;
+                    break;
+                }
+
+                goto next_param;
+            }
+
+            if (last - start >= 11
+                && ngx_strncasecmp(start, (u_char *) "rel=preload", 11) == 0)
+            {
+                start += 11;
+
+                if (start == last || *start == ' ' || *start == ';') {
+                    push = 1;
+                }
+
+                goto next_param;
+            }
+
+            if (last - start >= 4
+                && ngx_strncasecmp(start, (u_char *) "rel=", 4) == 0)
+            {
+                start += 4;
+
+                while (start < last && *start == ' ') { start++; }
+
+                if (start == last || *start++ != '"') {
+                    goto next_param;
+                }
+
+                for ( ;; ) {
+
+                    while (start < last && *start == ' ') { start++; }
+
+                    if (last - start >= 7
+                        && ngx_strncasecmp(start, (u_char *) "preload", 7) == 0)
+                    {
+                        start += 7;
+
+                        if (start < last && (*start == ' ' || *start == '"')) {
+                            push = 1;
+                            break;
+                        }
+                    }
+
+                    while (start < last && *start != ' ' && *start != '"') {
+                        start++;
+                    }
+
+                    if (start == last) {
+                        break;
+                    }
+
+                    if (*start == '"') {
+                        break;
+                    }
+
+                    start++;
+                }
+            }
+
+        next_param:
+
+            start = ngx_strlchr(start, last, ';');
+
+            if (start == NULL) {
+                break;
+            }
+
+            start++;
+        }
+
+        if (push) {
+            while (path.len && path.data[path.len - 1] == ' ') {
+                path.len--;
+            }
+        }
+
+        if (push && path.len
+            && !(path.len > 1 && path.data[0] == '/' && path.data[1] == '/'))
+        {
+            rc = ngx_http_v2_push_resource(r, &path, &authority);
+
+            if (rc == NGX_ERROR) {
+                return NGX_ERROR;
+            }
+
+            if (rc == NGX_ABORT) {
+                return NGX_OK;
+            }
+
+            /* NGX_OK, NGX_DECLINED */
+        }
+
+        if (last < end) {
+            start = last + 1;
+            goto next_link;
+        }
+    }
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_http_v2_push_resource(ngx_http_request_t *r, ngx_str_t *path,
+    ngx_str_t *authority)
+{
+    u_char                    *start, *pos, *tmp;
+    size_t                     len;
+    ngx_table_elt_t           *host;
+    ngx_connection_t          *fc;
+    ngx_http_v2_stream_t      *stream;
+    ngx_http_v2_out_frame_t   *frame;
+    ngx_http_v2_connection_t  *h2c;
+
+    fc = r->connection;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0, "http2 push resource");
+
+    stream = r->stream;
+    h2c = stream->connection;
+
+    if (!ngx_path_separator(path->data[0])) {
+        ngx_log_error(NGX_LOG_WARN, fc->log, 0,
+                      "non-absolute path \"%V\" not pushed", path);
+        return NGX_DECLINED;
+    }
+
+    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                  "http2 pushing:%ui limit:%ui",
+                  h2c->pushing, h2c->concurrent_pushes);
+
+    if (h2c->pushing >= h2c->concurrent_pushes) {
+        return NGX_ABORT;
+    }
+
+    if (h2c->last_push == 0x7ffffffe) {
+        return NGX_ABORT;
+    }
+
+    if (path->len > NGX_HTTP_V2_MAX_FIELD) {
+        return NGX_DECLINED;
+    }
+
+    host = r->headers_in.host;
+
+    if (authority->len == 0 && host) {
+
+        len = 1 + NGX_HTTP_V2_INT_OCTETS + host->value.len;
+
+        tmp = ngx_palloc(r->pool, len);
+        pos = ngx_pnalloc(r->pool, len);
+
+        if (pos == NULL || tmp == NULL) {
+            return NGX_ERROR;
+        }
+
+        authority->data = pos;
+
+        *pos++ = ngx_http_v2_inc_indexed(NGX_HTTP_V2_AUTHORITY_INDEX);
+        pos = ngx_http_v2_write_value(pos, host->value.data, host->value.len,
+                                      tmp);
+
+        authority->len = pos - authority->data;
+    }
+
+    len = (h2c->table_update ? 1 : 0)
+          + 1
+          + 1 + NGX_HTTP_V2_INT_OCTETS + path->len
+          + authority->len
+          + 1;
+
+    tmp = ngx_palloc(r->pool, len);
+    pos = ngx_pnalloc(r->pool, len);
+
+    if (pos == NULL || tmp == NULL) {
+        return NGX_ERROR;
+    }
+
+    start = pos;
+
+    if (h2c->table_update) {
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0,
+                       "http2 table size update: 0");
+        *pos++ = (1 << 5) | 0;
+        h2c->table_update = 0;
+    }
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0,
+                   "http2 push header: \":method: GET\"");
+
+    *pos++ = ngx_http_v2_indexed(NGX_HTTP_V2_METHOD_GET_INDEX);
+
+    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
+                   "http2 push header: \":path: %V\"", path);
+
+    *pos++ = ngx_http_v2_inc_indexed(NGX_HTTP_V2_PATH_INDEX);
+    pos = ngx_http_v2_write_value(pos, path->data, path->len, tmp);
+
+    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, fc->log, 0,
+                   "http2 push header: \":authority: %V\"", &host->value);
+
+    pos = ngx_cpymem(pos, authority->data, authority->len);
+
+#if (NGX_HTTP_SSL)
+    if (fc->ssl) {
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0,
+                       "http2 push header: \":scheme: https\"");
+        *pos++ = ngx_http_v2_indexed(NGX_HTTP_V2_SCHEME_HTTPS_INDEX);
+
+    } else
+#endif
+    {
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, fc->log, 0,
+                       "http2 push header: \":scheme: http\"");
+        *pos++ = ngx_http_v2_indexed(NGX_HTTP_V2_SCHEME_HTTP_INDEX);
+    }
+
+    frame = ngx_http_v2_create_push_frame(r, start, pos);
+    if (frame == NULL) {
+        return NGX_ERROR;
+    }
+
+    ngx_http_v2_queue_blocked_frame(h2c, frame);
+
+    stream->queued++;
+
+    return ngx_http_v2_push_stream(h2c, stream->node->id, pos - start,
+                                   path, &host->value);
+}
+
+
 static u_char *
 ngx_http_v2_string_encode(u_char *dst, u_char *src, size_t len, u_char *tmp,
     ngx_uint_t lower)
@@ -809,6 +1193,125 @@ ngx_http_v2_create_headers_frame(ngx_http_request_t *r, u_char *pos,
 
 
 static ngx_http_v2_out_frame_t *
+ngx_http_v2_create_push_frame(ngx_http_request_t *r, u_char *pos, u_char *end)
+{
+    u_char                     type, flags;
+    size_t                     rest, frame_size, len;
+    ngx_buf_t                 *b;
+    ngx_chain_t               *cl, **ll;
+    ngx_http_v2_stream_t      *stream;
+    ngx_http_v2_out_frame_t   *frame;
+    ngx_http_v2_connection_t  *h2c;
+
+    stream = r->stream;
+    h2c = stream->connection;
+    rest = NGX_HTTP_V2_STREAM_ID_SIZE + (end - pos);
+
+    frame = ngx_palloc(r->pool, sizeof(ngx_http_v2_out_frame_t));
+    if (frame == NULL) {
+        return NULL;
+    }
+
+    frame->handler = ngx_http_v2_push_frame_handler;
+    frame->stream = stream;
+    frame->length = rest;
+    frame->blocked = 1;
+    frame->fin = 0;
+
+    ll = &frame->first;
+
+    type = NGX_HTTP_V2_PUSH_PROMISE_FRAME;
+    flags = NGX_HTTP_V2_NO_FLAG;
+    frame_size = h2c->frame_size;
+
+    for ( ;; ) {
+        if (rest <= frame_size) {
+            frame_size = rest;
+            flags |= NGX_HTTP_V2_END_HEADERS_FLAG;
+        }
+
+        b = ngx_create_temp_buf(r->pool,
+                                NGX_HTTP_V2_FRAME_HEADER_SIZE
+                                + ((type == NGX_HTTP_V2_PUSH_PROMISE_FRAME)
+                                   ? NGX_HTTP_V2_STREAM_ID_SIZE : 0));
+        if (b == NULL) {
+            return NULL;
+        }
+
+        b->last = ngx_http_v2_write_len_and_type(b->last, frame_size, type);
+        *b->last++ = flags;
+        b->last = ngx_http_v2_write_sid(b->last, stream->node->id);
+
+        b->tag = (ngx_buf_tag_t) &ngx_http_v2_module;
+
+        if (type == NGX_HTTP_V2_PUSH_PROMISE_FRAME) {
+            h2c->last_push += 2;
+
+            b->last = ngx_http_v2_write_sid(b->last, h2c->last_push);
+            len = frame_size - NGX_HTTP_V2_STREAM_ID_SIZE;
+
+        } else {
+            len = frame_size;
+        }
+
+        cl = ngx_alloc_chain_link(r->pool);
+        if (cl == NULL) {
+            return NULL;
+        }
+
+        cl->buf = b;
+
+        *ll = cl;
+        ll = &cl->next;
+
+        b = ngx_calloc_buf(r->pool);
+        if (b == NULL) {
+            return NULL;
+        }
+
+        b->pos = pos;
+
+        pos += len;
+
+        b->last = pos;
+        b->start = b->pos;
+        b->end = b->last;
+        b->temporary = 1;
+
+        cl = ngx_alloc_chain_link(r->pool);
+        if (cl == NULL) {
+            return NULL;
+        }
+
+        cl->buf = b;
+
+        *ll = cl;
+        ll = &cl->next;
+
+        rest -= frame_size;
+
+        if (rest) {
+            frame->length += NGX_HTTP_V2_FRAME_HEADER_SIZE;
+
+            type = NGX_HTTP_V2_CONTINUATION_FRAME;
+            continue;
+        }
+
+        cl->next = NULL;
+        frame->last = cl;
+
+        ngx_log_debug4(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
+                       "http2:%ui create PUSH_PROMISE frame %p: "
+                       "sid:%ui len:%uz",
+                       stream->node->id, frame, h2c->last_push,
+                       frame->length);
+
+        return frame;
+    }
+}
+
+
+static ngx_http_v2_out_frame_t *
 ngx_http_v2_create_trailers_frame(ngx_http_request_t *r)
 {
     u_char            *pos, *start, *tmp;
@@ -1377,6 +1880,60 @@ ngx_http_v2_headers_frame_handler(ngx_http_v2_connection_t *h2c,
 
 
 static ngx_int_t
+ngx_http_v2_push_frame_handler(ngx_http_v2_connection_t *h2c,
+    ngx_http_v2_out_frame_t *frame)
+{
+    ngx_chain_t           *cl, *ln;
+    ngx_http_v2_stream_t  *stream;
+
+    stream = frame->stream;
+    cl = frame->first;
+
+    for ( ;; ) {
+        if (cl->buf->pos != cl->buf->last) {
+            frame->first = cl;
+
+            ngx_log_debug2(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                           "http2:%ui PUSH_PROMISE frame %p was sent partially",
+                           stream->node->id, frame);
+
+            return NGX_AGAIN;
+        }
+
+        ln = cl->next;
+
+        if (cl->buf->tag == (ngx_buf_tag_t) &ngx_http_v2_module) {
+            cl->next = stream->free_frame_headers;
+            stream->free_frame_headers = cl;
+
+        } else {
+            cl->next = stream->free_bufs;
+            stream->free_bufs = cl;
+        }
+
+        if (cl == frame->last) {
+            break;
+        }
+
+        cl = ln;
+    }
+
+    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
+                   "http2:%ui PUSH_PROMISE frame %p was sent",
+                   stream->node->id, frame);
+
+    stream->request->header_size += NGX_HTTP_V2_FRAME_HEADER_SIZE
+                                    + frame->length;
+
+    ngx_http_v2_handle_frame(stream, frame);
+
+    ngx_http_v2_handle_stream(h2c, stream);
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
 ngx_http_v2_data_frame_handler(ngx_http_v2_connection_t *h2c,
     ngx_http_v2_out_frame_t *frame)
 {
diff --git a/src/http/v2/ngx_http_v2_module.c b/src/http/v2/ngx_http_v2_module.c
index 7f7dab29e..c54dc103a 100644
--- a/src/http/v2/ngx_http_v2_module.c
+++ b/src/http/v2/ngx_http_v2_module.c
@@ -27,6 +27,8 @@ static void *ngx_http_v2_create_loc_conf(ngx_conf_t *cf);
 static char *ngx_http_v2_merge_loc_conf(ngx_conf_t *cf, void *parent,
     void *child);
 
+static char *ngx_http_v2_push(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
+
 static char *ngx_http_v2_recv_buffer_size(ngx_conf_t *cf, void *post,
     void *data);
 static char *ngx_http_v2_pool_size(ngx_conf_t *cf, void *post, void *data);
@@ -73,6 +75,13 @@ static ngx_command_t  ngx_http_v2_commands[] = {
       offsetof(ngx_http_v2_srv_conf_t, concurrent_streams),
       NULL },
 
+    { ngx_string("http2_max_concurrent_pushes"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_num_slot,
+      NGX_HTTP_SRV_CONF_OFFSET,
+      offsetof(ngx_http_v2_srv_conf_t, concurrent_pushes),
+      NULL },
+
     { ngx_string("http2_max_requests"),
       NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_TAKE1,
       ngx_conf_set_num_slot,
@@ -129,6 +138,20 @@ static ngx_command_t  ngx_http_v2_commands[] = {
       offsetof(ngx_http_v2_loc_conf_t, chunk_size),
       &ngx_http_v2_chunk_size_post },
 
+    { ngx_string("http2_push_preload"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_v2_loc_conf_t, push_preload),
+      NULL },
+
+    { ngx_string("http2_push"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
+      ngx_http_v2_push,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      0,
+      NULL },
+
     { ngx_string("spdy_recv_buffer_size"),
       NGX_HTTP_MAIN_CONF|NGX_CONF_TAKE1,
       ngx_http_v2_spdy_deprecated,
@@ -329,6 +352,7 @@ ngx_http_v2_create_srv_conf(ngx_conf_t *cf)
     h2scf->pool_size = NGX_CONF_UNSET_SIZE;
 
     h2scf->concurrent_streams = NGX_CONF_UNSET_UINT;
+    h2scf->concurrent_pushes = NGX_CONF_UNSET_UINT;
     h2scf->max_requests = NGX_CONF_UNSET_UINT;
 
     h2scf->max_field_size = NGX_CONF_UNSET_SIZE;
@@ -355,6 +379,8 @@ ngx_http_v2_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
 
     ngx_conf_merge_uint_value(conf->concurrent_streams,
                               prev->concurrent_streams, 128);
+    ngx_conf_merge_uint_value(conf->concurrent_pushes,
+                              prev->concurrent_pushes, 10);
     ngx_conf_merge_uint_value(conf->max_requests, prev->max_requests, 1000);
 
     ngx_conf_merge_size_value(conf->max_field_size, prev->max_field_size,
@@ -386,8 +412,17 @@ ngx_http_v2_create_loc_conf(ngx_conf_t *cf)
         return NULL;
     }
 
+    /*
+     * set by ngx_pcalloc():
+     *
+     *     h2lcf->pushes = NULL;
+     */
+
     h2lcf->chunk_size = NGX_CONF_UNSET_SIZE;
 
+    h2lcf->push_preload = NGX_CONF_UNSET;
+    h2lcf->push = NGX_CONF_UNSET;
+
     return h2lcf;
 }
 
@@ -400,6 +435,72 @@ ngx_http_v2_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
 
     ngx_conf_merge_size_value(conf->chunk_size, prev->chunk_size, 8 * 1024);
 
+    ngx_conf_merge_value(conf->push, prev->push, 1);
+
+    if (conf->push && conf->pushes == NULL) {
+        conf->pushes = prev->pushes;
+    }
+
+    ngx_conf_merge_value(conf->push_preload, prev->push_preload, 0);
+
+    return NGX_CONF_OK;
+}
+
+
+static char *
+ngx_http_v2_push(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
+{
+    ngx_http_v2_loc_conf_t *h2lcf = conf;
+
+    ngx_str_t                         *value;
+    ngx_http_complex_value_t          *cv;
+    ngx_http_compile_complex_value_t   ccv;
+
+    value = cf->args->elts;
+
+    if (ngx_strcmp(value[1].data, "off") == 0) {
+
+        if (h2lcf->pushes) {
+            return "\"off\" parameter cannot be used with URI";
+        }
+
+        if (h2lcf->push == 0) {
+            return "is duplicate";
+        }
+
+        h2lcf->push = 0;
+        return NGX_CONF_OK;
+    }
+
+    if (h2lcf->push == 0) {
+        return "URI cannot be used with \"off\" parameter";
+    }
+
+    h2lcf->push = 1;
+
+    if (h2lcf->pushes == NULL) {
+        h2lcf->pushes = ngx_array_create(cf->pool, 1,
+                                         sizeof(ngx_http_complex_value_t));
+        if (h2lcf->pushes == NULL) {
+            return NGX_CONF_ERROR;
+        }
+    }
+
+    cv = ngx_array_push(h2lcf->pushes);
+    if (cv == NULL) {
+        return NGX_CONF_ERROR;
+    }
+
+    ngx_memzero(&ccv, sizeof(ngx_http_compile_complex_value_t));
+
+    ccv.cf = cf;
+    ccv.value = &value[1];
+    ccv.complex_value = cv;
+
+    if (ngx_http_compile_complex_value(&ccv) != NGX_OK) {
+        return NGX_CONF_ERROR;
+    }
+
     return NGX_CONF_OK;
 }
 
diff --git a/src/http/v2/ngx_http_v2_module.h b/src/http/v2/ngx_http_v2_module.h
index 540f8267c..cdd2921a5 100644
--- a/src/http/v2/ngx_http_v2_module.h
+++ b/src/http/v2/ngx_http_v2_module.h
@@ -23,6 +23,7 @@ typedef struct {
 typedef struct {
     size_t                          pool_size;
     ngx_uint_t                      concurrent_streams;
+    ngx_uint_t                      concurrent_pushes;
     ngx_uint_t                      max_requests;
     size_t                          max_field_size;
     size_t                          max_header_size;
@@ -35,6 +36,11 @@ typedef struct {
 
 typedef struct {
     size_t                          chunk_size;
+
+    ngx_flag_t                      push_preload;
+
+    ngx_flag_t                      push;
+    ngx_array_t                    *pushes;
 } ngx_http_v2_loc_conf_t;