Implemented "return" action.

The "return" action can be used to immediately generate a simple HTTP response
with an arbitrary status:

  {
      "action": {
          "return": 404
      }
  }

This is especially useful for denying access to specific resources.

auto/sources

@@ -87,6 +87,7 @@ NXT_LIB_SRCS=" \
     src/nxt_http_error.c \
     src/nxt_http_route.c \
     src/nxt_http_route_addr.c \
+    src/nxt_http_return.c \
     src/nxt_http_static.c \
     src/nxt_http_proxy.c \
     src/nxt_application.c \

src/nxt_conf_validation.c

@@ -64,6 +64,8 @@ static nxt_int_t nxt_conf_vldt_action(nxt_conf_validation_t *vldt,
     nxt_conf_value_t *value, void *data);
 static nxt_int_t nxt_conf_vldt_pass(nxt_conf_validation_t *vldt,
     nxt_conf_value_t *value, void *data);
+static nxt_int_t nxt_conf_vldt_return(nxt_conf_validation_t *vldt,
+    nxt_conf_value_t *value, void *data);
 static nxt_int_t nxt_conf_vldt_proxy(nxt_conf_validation_t *vldt,
     nxt_conf_value_t *value, void *data);
 static nxt_int_t nxt_conf_vldt_routes(nxt_conf_validation_t *vldt,
@@ -354,6 +356,16 @@ static nxt_conf_vldt_object_t  nxt_conf_vldt_pass_action_members[] = {
 };
 
 
+static nxt_conf_vldt_object_t  nxt_conf_vldt_return_action_members[] = {
+    { nxt_string("return"),
+      NXT_CONF_VLDT_INTEGER,
+      &nxt_conf_vldt_return,
+      NULL },
+
+    NXT_CONF_VLDT_END
+};
+
+
 static nxt_conf_vldt_object_t  nxt_conf_vldt_share_action_members[] = {
     { nxt_string("share"),
       NXT_CONF_VLDT_STRING,
@@ -978,6 +990,7 @@ nxt_conf_vldt_action(nxt_conf_validation_t *vldt, nxt_conf_value_t *value,
 
     } actions[] = {
         { nxt_string("pass"), nxt_conf_vldt_pass_action_members },
+        { nxt_string("return"), nxt_conf_vldt_return_action_members },
         { nxt_string("share"), nxt_conf_vldt_share_action_members },
         { nxt_string("proxy"), nxt_conf_vldt_proxy_action_members },
     };
@@ -993,8 +1006,8 @@ nxt_conf_vldt_action(nxt_conf_validation_t *vldt, nxt_conf_value_t *value,
 
         if (members != NULL) {
             return nxt_conf_vldt_error(vldt, "The \"action\" object must have "
-                                       "just one of \"pass\", \"share\" or "
+                                       "just one of \"pass\", \"return\", "
-                                       "\"proxy\" options set.");
+                                       "\"share\", or \"proxy\" options set.");
         }
 
         members = actions[i].members;
@@ -1002,8 +1015,8 @@ nxt_conf_vldt_action(nxt_conf_validation_t *vldt, nxt_conf_value_t *value,
 
     if (members == NULL) {
         return nxt_conf_vldt_error(vldt, "The \"action\" object must have "
-                                         "either \"pass\", \"share\", or "
+                                   "either \"pass\", \"return\", \"share\", "
-                                         "\"proxy\" option set.");
+                                   "or \"proxy\" option set.");
     }
 
     return nxt_conf_vldt_object(vldt, value, members);
@@ -1114,6 +1127,23 @@ error:
 }
 
 
+static nxt_int_t
+nxt_conf_vldt_return(nxt_conf_validation_t *vldt, nxt_conf_value_t *value,
+    void *data)
+{
+    int64_t  status;
+
+    status = nxt_conf_get_integer(value);
+
+    if (status < NXT_HTTP_INVALID || status > NXT_HTTP_STATUS_MAX) {
+        return nxt_conf_vldt_error(vldt, "The \"return\" value is out of "
+                                   "allowed HTTP status code range 0-999.");
+    }
+
+    return NXT_OK;
+}
+
+
 static nxt_int_t
 nxt_conf_vldt_proxy(nxt_conf_validation_t *vldt, nxt_conf_value_t *value,
     void *data)

src/nxt_http.h

@@ -43,6 +43,9 @@ typedef enum {
     NXT_HTTP_SERVICE_UNAVAILABLE = 503,
     NXT_HTTP_GATEWAY_TIMEOUT = 504,
     NXT_HTTP_VERSION_NOT_SUPPORTED = 505,
+    NXT_HTTP_SERVER_ERROR_MAX = 599,
+
+    NXT_HTTP_STATUS_MAX = 999,
 } nxt_http_status_t;
 
 
@@ -192,6 +195,7 @@ struct nxt_http_action_s {
         nxt_http_action_t           *fallback;
         nxt_upstream_t              *upstream;
         uint32_t                    upstream_number;
+        nxt_http_status_t           return_code;
     } u;
 
     nxt_str_t                       name;
@@ -282,6 +286,9 @@ nxt_int_t nxt_upstreams_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
 nxt_int_t nxt_upstreams_joint_create(nxt_router_temp_conf_t *tmcf,
     nxt_upstream_t ***upstream_joint);
 
+nxt_http_action_t *nxt_http_return_handler(nxt_task_t *task,
+    nxt_http_request_t *r, nxt_http_action_t *action);
+
 nxt_http_action_t *nxt_http_static_handler(nxt_task_t *task,
     nxt_http_request_t *r, nxt_http_action_t *action);
 nxt_int_t nxt_http_static_mtypes_init(nxt_mp_t *mp, nxt_lvlhsh_t *hash);

src/nxt_http_return.c

@@ -0,0 +1,42 @@
+
+/*
+ * Copyright (C) NGINX, Inc.
+ */
+
+#include <nxt_router.h>
+#include <nxt_http.h>
+
+
+static const nxt_http_request_state_t  nxt_http_return_send_state;
+
+
+nxt_http_action_t *
+nxt_http_return_handler(nxt_task_t *task, nxt_http_request_t *r,
+    nxt_http_action_t *action)
+{
+    nxt_http_status_t  status;
+
+    status = action->u.return_code;
+
+    if (status >= NXT_HTTP_BAD_REQUEST
+        && status <= NXT_HTTP_SERVER_ERROR_MAX)
+    {
+        nxt_http_request_error(task, r, status);
+        return NULL;
+    }
+
+    r->status = status;
+    r->resp.content_length_n = 0;
+    r->state = &nxt_http_return_send_state;
+
+    nxt_http_request_header_send(task, r, NULL, NULL);
+
+    return NULL;
+}
+
+
+static const nxt_http_request_state_t  nxt_http_return_send_state
+    nxt_aligned(64) =
+{
+    .error_handler = nxt_http_request_error_handler,
+};

src/nxt_http_route.c

@@ -41,6 +41,7 @@ typedef enum {
 
 typedef struct {
     nxt_conf_value_t               *pass;
+    nxt_conf_value_t               *ret;
     nxt_conf_value_t               *share;
     nxt_conf_value_t               *proxy;
     nxt_conf_value_t               *fallback;
@@ -575,6 +576,11 @@ static nxt_conf_map_t  nxt_http_route_action_conf[] = {
         NXT_CONF_MAP_PTR,
         offsetof(nxt_http_route_action_conf_t, pass)
     },
+    {
+        nxt_string("return"),
+        NXT_CONF_MAP_PTR,
+        offsetof(nxt_http_route_action_conf_t, ret)
+    },
     {
         nxt_string("share"),
         NXT_CONF_MAP_PTR,
@@ -613,6 +619,12 @@ nxt_http_route_action_create(nxt_router_temp_conf_t *tmcf, nxt_conf_value_t *cv,
 
     nxt_memzero(action, sizeof(nxt_http_action_t));
 
+    if (accf.ret != NULL) {
+        action->handler = nxt_http_return_handler;
+        action->u.return_code = nxt_conf_get_integer(accf.ret);
+        return NXT_OK;
+    }
+
     conf = accf.pass;
 
     if (accf.share != NULL) {