[PATCH 3 of 3] Headers filter: added "add_trailer" directive

Piotr Sikora piotrsikora at google.com
Fri Jun 2 09:04:08 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 52201fff87e8c5a096287cf206cdcc14c0d81ce7
# Parent  e84aa49c5bc7a3250d4844b581e4bf3ed42db5f5
Headers filter: added "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 e84aa49c5bc7 -r 52201fff87e8 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
 };
 
@@ -144,20 +155,30 @@ ngx_module_t  ngx_http_headers_filter_mo
 
 
 static ngx_http_output_header_filter_pt  ngx_http_next_header_filter;
+static ngx_http_output_body_filter_pt    ngx_http_next_body_filter;
 
 
 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);
     }
@@ -206,11 +227,162 @@ ngx_http_headers_filter(ngx_http_request
         }
     }
 
+    if (conf->trailers) {
+
+        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);
+        }
+
+        if (r->http_version < NGX_HTTP_VERSION_20) {
+            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;
+
+        data = ngx_pnalloc(r->pool, len);
+        if (data == NULL) {
+            return NGX_ERROR;
+        }
+
+        t = ngx_list_push(&r->headers_out.headers);
+        if (t == 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 = 1;
+
+        r->expect_trailers = 1;
+    }
+
     return ngx_http_next_header_filter(r);
 }
 
 
 static ngx_int_t
+ngx_http_trailers_filter(ngx_http_request_t *r, ngx_chain_t *in)
+{
+    ngx_str_t                 value;
+    ngx_uint_t                i, safe_status;
+    ngx_chain_t              *cl;
+    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 (in == NULL
+        || conf->trailers == NULL
+        || !r->expect_trailers
+        || r->header_only)
+    {
+        return ngx_http_next_body_filter(r, in);
+    }
+
+    for (cl = in; cl; cl = cl->next) {
+        if (cl->buf->last_buf) {
+            break;
+        }
+    }
+
+    if (cl == NULL) {
+        return ngx_http_next_body_filter(r, in);
+    }
+
+    switch (r->headers_out.status) {
+
+    case NGX_HTTP_OK:
+    case NGX_HTTP_CREATED:
+    case NGX_HTTP_PARTIAL_CONTENT:
+    case NGX_HTTP_MOVED_PERMANENTLY:
+    case NGX_HTTP_MOVED_TEMPORARILY:
+    case NGX_HTTP_SEE_OTHER:
+    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_http_next_body_filter(r, in);
+}
+
+
+static ngx_int_t
 ngx_http_set_expires(ngx_http_request_t *r, ngx_http_headers_conf_t *conf)
 {
     char                *err;
@@ -557,6 +729,7 @@ 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;
      */
@@ -587,6 +760,10 @@ ngx_http_headers_merge_conf(ngx_conf_t *
         conf->headers = prev->headers;
     }
 
+    if (conf->trailers == NULL) {
+        conf->trailers = prev->trailers;
+    }
+
     return NGX_CONF_OK;
 }
 
@@ -597,6 +774,9 @@ ngx_http_headers_filter_init(ngx_conf_t 
     ngx_http_next_header_filter = ngx_http_top_header_filter;
     ngx_http_top_header_filter = ngx_http_headers_filter;
 
+    ngx_http_next_body_filter = ngx_http_top_body_filter;
+    ngx_http_top_body_filter = ngx_http_trailers_filter;
+
     return NGX_OK;
 }
 
@@ -741,3 +921,63 @@ 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;
+}


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