[PATCH 2 of 3] Headers filter: add "add_trailer" directive

Piotr Sikora piotrsikora at google.com
Fri Mar 24 10:47:40 UTC 2017


# HG changeset patch
# User Piotr Sikora <piotrsikora at google.com>
# Date 1490351854 25200
#      Fri Mar 24 03:37:34 2017 -0700
# Node ID 6d878f4585b977053a9d00053bbb7aff263eb96c
# Parent  a0f291f0a903b863161900f4d0cbb405f5d7a735
Headers filter: add "add_trailer" directive.

Trailers added using this directive are evaluated after response body
is processed by output filters (but before it's written to the wire),
so it's possible to use variables calculated from the response body
as the trailer value.

Signed-off-by: Piotr Sikora <piotrsikora at google.com>

diff -r a0f291f0a903 -r 6d878f4585b9 src/http/modules/ngx_http_chunked_filter_module.c
--- a/src/http/modules/ngx_http_chunked_filter_module.c
+++ b/src/http/modules/ngx_http_chunked_filter_module.c
@@ -256,6 +256,10 @@ ngx_http_chunked_create_trailers(ngx_htt
     ngx_table_elt_t                *header;
     ngx_http_chunked_filter_ctx_t  *ctx;
 
+    if (ngx_http_eval_trailers(r) != NGX_OK) {
+        return NULL;
+    }
+
     len = 0;
 
     part = &r->headers_out.trailers.part;
diff -r a0f291f0a903 -r 6d878f4585b9 src/http/modules/ngx_http_headers_filter_module.c
--- a/src/http/modules/ngx_http_headers_filter_module.c
+++ b/src/http/modules/ngx_http_headers_filter_module.c
@@ -48,6 +48,7 @@ typedef struct {
     time_t                     expires_time;
     ngx_http_complex_value_t  *expires_value;
     ngx_array_t               *headers;
+    ngx_array_t               *trailers;
 } ngx_http_headers_conf_t;
 
 
@@ -72,6 +73,8 @@ static char *ngx_http_headers_expires(ng
     void *conf);
 static char *ngx_http_headers_add(ngx_conf_t *cf, ngx_command_t *cmd,
     void *conf);
+static char *ngx_http_headers_add_trailer(ngx_conf_t *cf, ngx_command_t *cmd,
+    void *conf);
 
 
 static ngx_http_set_header_t  ngx_http_set_headers[] = {
@@ -108,6 +111,14 @@ static ngx_command_t  ngx_http_headers_f
       0,
       NULL},
 
+    { ngx_string("add_trailer"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_HTTP_LIF_CONF
+                        |NGX_CONF_TAKE23,
+      ngx_http_headers_add_trailer,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      0,
+      NULL},
+
       ngx_null_command
 };
 
@@ -149,15 +160,24 @@ static ngx_http_output_header_filter_pt 
 static ngx_int_t
 ngx_http_headers_filter(ngx_http_request_t *r)
 {
-    ngx_str_t                 value;
-    ngx_uint_t                i, safe_status;
-    ngx_http_header_val_t    *h;
-    ngx_http_headers_conf_t  *conf;
+    u_char                    *p, *data;
+    size_t                     len;
+    ngx_str_t                  value;
+    ngx_uint_t                 i, safe_status;
+    ngx_table_elt_t           *t;
+    ngx_http_header_val_t     *h;
+    ngx_http_headers_conf_t   *conf;
+    ngx_http_core_loc_conf_t  *clcf;
+
+    if (r != r->main) {
+        return ngx_http_next_header_filter(r);
+    }
 
     conf = ngx_http_get_module_loc_conf(r, ngx_http_headers_filter_module);
 
-    if ((conf->expires == NGX_HTTP_EXPIRES_OFF && conf->headers == NULL)
-        || r != r->main)
+    if (conf->expires == NGX_HTTP_EXPIRES_OFF
+        && conf->headers == NULL
+        && conf->trailers == NULL)
     {
         return ngx_http_next_header_filter(r);
     }
@@ -205,6 +225,84 @@ ngx_http_headers_filter(ngx_http_request
         }
     }
 
+    if (conf->trailers && r->allow_trailers) {
+
+        if (r->http_version < NGX_HTTP_VERSION_20) {
+            if (r->header_only
+                || r->headers_out.status == NGX_HTTP_NOT_MODIFIED
+                || r->headers_out.status == NGX_HTTP_NO_CONTENT
+                || r->headers_out.status < NGX_HTTP_OK
+                || r->method == NGX_HTTP_HEAD)
+            {
+               return ngx_http_next_header_filter(r);
+            }
+
+            clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
+
+            if (!clcf->chunked_transfer_encoding) {
+                return ngx_http_next_header_filter(r);
+            }
+        }
+
+        len = 0;
+
+        h = conf->trailers->elts;
+        for (i = 0; i < conf->trailers->nelts; i++) {
+
+            if (!safe_status && !h[i].always) {
+                continue;
+            }
+
+            if (h[i].value.value.len) {
+                len += h[i].key.len + sizeof(", ") - 1;
+            }
+        }
+
+        if (len == 0) {
+            return ngx_http_next_header_filter(r);
+        }
+
+        len -= sizeof(", ") - 1;
+
+        t = ngx_list_push(&r->headers_out.headers);
+        if (t == NULL) {
+            return NGX_ERROR;
+        }
+
+        data = ngx_pnalloc(r->pool, len);
+        if (data == NULL) {
+            return NGX_ERROR;
+        }
+
+        p = data;
+
+        h = conf->trailers->elts;
+        for (i = 0; i < conf->trailers->nelts; i++) {
+
+            if (!safe_status && !h[i].always) {
+                continue;
+            }
+
+            if (h[i].value.value.len) {
+                p = ngx_copy(p, h[i].key.data, h[i].key.len);
+
+                if (p == data + len) {
+                    break;
+                }
+
+                *p++ = ','; *p++ = ' ';
+            }
+        }
+
+        ngx_str_set(&t->key, "Trailer");
+        t->value.data = data;
+        t->value.len = len;
+        t->hash = ngx_hash(ngx_hash(ngx_hash(ngx_hash(ngx_hash(
+                           ngx_hash('t', 'r'), 'a'), 'i'), 'l'), 'e'), 'r');
+
+        r->expect_trailers = 1;
+    }
+
     return ngx_http_next_header_filter(r);
 }
 
@@ -541,6 +639,67 @@ ngx_http_set_response_header(ngx_http_re
 }
 
 
+ngx_int_t
+ngx_http_eval_trailers(ngx_http_request_t *r)
+{
+    ngx_str_t                 value;
+    ngx_uint_t                i, safe_status;
+    ngx_table_elt_t          *t;
+    ngx_http_header_val_t    *h;
+    ngx_http_headers_conf_t  *conf;
+
+    conf = ngx_http_get_module_loc_conf(r, ngx_http_headers_filter_module);
+
+    if (conf->trailers == NULL) {
+        return NGX_OK;
+    }
+
+    switch (r->headers_out.status) {
+
+    case NGX_HTTP_OK:
+    case NGX_HTTP_CREATED:
+    case NGX_HTTP_NO_CONTENT:
+    case NGX_HTTP_PARTIAL_CONTENT:
+    case NGX_HTTP_MOVED_PERMANENTLY:
+    case NGX_HTTP_MOVED_TEMPORARILY:
+    case NGX_HTTP_SEE_OTHER:
+    case NGX_HTTP_NOT_MODIFIED:
+    case NGX_HTTP_TEMPORARY_REDIRECT:
+        safe_status = 1;
+        break;
+
+    default:
+        safe_status = 0;
+        break;
+    }
+
+    h = conf->trailers->elts;
+    for (i = 0; i < conf->trailers->nelts; i++) {
+
+        if (!safe_status && !h[i].always) {
+            continue;
+        }
+
+        if (ngx_http_complex_value(r, &h[i].value, &value) != NGX_OK) {
+            return NGX_ERROR;
+        }
+
+        if (value.len) {
+            t = ngx_list_push(&r->headers_out.trailers);
+            if (t == NULL) {
+                return NGX_ERROR;
+            }
+
+            t->key = h[i].key;
+            t->value = value;
+            t->hash = 1;
+        }
+    }
+
+    return NGX_OK;
+}
+
+
 static void *
 ngx_http_headers_create_conf(ngx_conf_t *cf)
 {
@@ -555,6 +714,7 @@ ngx_http_headers_create_conf(ngx_conf_t 
      * set by ngx_pcalloc():
      *
      *     conf->headers = NULL;
+     *     conf->trailers = NULL;
      *     conf->expires_time = 0;
      *     conf->expires_value = NULL;
      */
@@ -585,6 +745,10 @@ ngx_http_headers_merge_conf(ngx_conf_t *
         conf->headers = prev->headers;
     }
 
+    if (conf->trailers == NULL) {
+        conf->trailers = prev->trailers;
+    }
+
     return NGX_CONF_OK;
 }
 
@@ -739,3 +903,63 @@ ngx_http_headers_add(ngx_conf_t *cf, ngx
 
     return NGX_CONF_OK;
 }
+
+
+static char *
+ngx_http_headers_add_trailer(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
+{
+    ngx_http_headers_conf_t *hcf = conf;
+
+    ngx_str_t                         *value;
+    ngx_http_header_val_t             *hv;
+    ngx_http_compile_complex_value_t   ccv;
+
+    value = cf->args->elts;
+
+    if (hcf->trailers == NULL) {
+        hcf->trailers = ngx_array_create(cf->pool, 1,
+                                         sizeof(ngx_http_header_val_t));
+        if (hcf->trailers == NULL) {
+            return NGX_CONF_ERROR;
+        }
+    }
+
+    hv = ngx_array_push(hcf->trailers);
+    if (hv == NULL) {
+        return NGX_CONF_ERROR;
+    }
+
+    hv->key = value[1];
+    hv->handler = NULL;
+    hv->offset = 0;
+    hv->always = 0;
+
+    if (value[2].len == 0) {
+        ngx_memzero(&hv->value, sizeof(ngx_http_complex_value_t));
+
+    } else {
+        ngx_memzero(&ccv, sizeof(ngx_http_compile_complex_value_t));
+
+        ccv.cf = cf;
+        ccv.value = &value[2];
+        ccv.complex_value = &hv->value;
+
+        if (ngx_http_compile_complex_value(&ccv) != NGX_OK) {
+            return NGX_CONF_ERROR;
+        }
+    }
+
+    if (cf->args->nelts == 3) {
+        return NGX_CONF_OK;
+    }
+
+    if (ngx_strcmp(value[3].data, "always") != 0) {
+        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                           "invalid parameter \"%V\"", &value[3]);
+        return NGX_CONF_ERROR;
+    }
+
+    hv->always = 1;
+
+    return NGX_CONF_OK;
+}
diff -r a0f291f0a903 -r 6d878f4585b9 src/http/ngx_http.h
--- a/src/http/ngx_http.h
+++ b/src/http/ngx_http.h
@@ -143,6 +143,7 @@ ngx_int_t ngx_http_special_response_hand
 ngx_int_t ngx_http_filter_finalize_request(ngx_http_request_t *r,
     ngx_module_t *m, ngx_int_t error);
 void ngx_http_clean_header(ngx_http_request_t *r);
+ngx_int_t ngx_http_eval_trailers(ngx_http_request_t *r);
 
 
 ngx_int_t ngx_http_discard_request_body(ngx_http_request_t *r);
diff -r a0f291f0a903 -r 6d878f4585b9 src/http/v2/ngx_http_v2_filter_module.c
--- a/src/http/v2/ngx_http_v2_filter_module.c
+++ b/src/http/v2/ngx_http_v2_filter_module.c
@@ -667,6 +667,10 @@ ngx_http_v2_create_trailers_frame(ngx_ht
     ngx_table_elt_t          *header;
     ngx_http_v2_out_frame_t  *frame;
 
+    if (ngx_http_eval_trailers(r) != NGX_OK) {
+        return NGX_HTTP_V2_FRAME_ERROR;
+    }
+
     len = 0;
     tmp_len = 0;
 


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