[PATCH 14 of 14] Request body: discarded body now treated as no body

[Maxim Dounin]

# HG changeset patch
# User Maxim Dounin <mdounin at mdounin.ru>
# Date 1713574649 -10800
#      Sat Apr 20 03:57:29 2024 +0300
# Node ID 7462f09d224220ae96ad181c823c2760cec8ba54
# Parent  4a81de7ba1d061f90960a5cc44d3a08e8c45fc1e
Request body: discarded body now treated as no body.

Notably, proxying of such requests now uses no Content-Length instead
of "Content-Length: 0", and the $content_length variable is empty (instead
of "0").

This might be beneficial from correctness point of view, since requests
with discarded body, such as during processing of error pages, do not pretend
there is a zero-length body, but instead do not contain body at all.  For
example, this might be important for PUT requests, where a zero-length
body could be incorrectly interpreted as a real request body.

This also slightly simplifies the code.

diff --git a/src/http/modules/ngx_http_proxy_module.c b/src/http/modules/ngx_http_proxy_module.c
--- a/src/http/modules/ngx_http_proxy_module.c
+++ b/src/http/modules/ngx_http_proxy_module.c
@@ -1342,7 +1342,7 @@ ngx_http_proxy_create_request(ngx_http_r
         ctx->internal_chunked = 1;
 
     } else if (r->discard_body) {
-        ctx->internal_body_length = 0;
+        ctx->internal_body_length = -1;
 
     } else {
         ctx->internal_body_length = r->headers_in.content_length_n;
diff --git a/src/http/ngx_http_request_body.c b/src/http/ngx_http_request_body.c
--- a/src/http/ngx_http_request_body.c
+++ b/src/http/ngx_http_request_body.c
@@ -46,7 +46,7 @@ ngx_http_read_client_request_body(ngx_ht
         r->request_body_no_buffering = 0;
 
         if (r->request_body && r->request_body->no_buffering) {
-            r->headers_in.content_length_n = 0;
+            r->discard_body = 1;
             r->request_body->bufs = NULL;
 
             if (r->reading_body) {
@@ -244,7 +244,7 @@ done:
     if (rc >= NGX_HTTP_SPECIAL_RESPONSE) {
 
         r->lingering_close = 1;
-        r->headers_in.content_length_n = 0;
+        r->discard_body = 1;
         r->request_body->bufs = NULL;
 
         r->main->count--;
@@ -319,7 +319,7 @@ ngx_http_read_client_request_body_handle
     if (rc >= NGX_HTTP_SPECIAL_RESPONSE) {
 
         r->lingering_close = 1;
-        r->headers_in.content_length_n = 0;
+        r->discard_body = 1;
         r->request_body->bufs = NULL;
 
         r->read_event_handler = ngx_http_block_reading;
@@ -679,27 +679,17 @@ ngx_http_discard_request_body(ngx_http_r
     ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                    "http set discard body");
 
+    r->discard_body = 1;
+
 #if (NGX_HTTP_V2)
     if (r->stream) {
         r->stream->skip_data = 1;
-
-        if (r->headers_in.content_length_n > 0 || r->headers_in.chunked) {
-            r->headers_in.content_length_n = 0;
-            r->discard_body = 1;
-        }
-
         return NGX_OK;
     }
 #endif
 
 #if (NGX_HTTP_V3)
     if (r->http_version == NGX_HTTP_VERSION_30) {
-
-        if (r->headers_in.content_length_n > 0 || r->headers_in.chunked) {
-            r->headers_in.content_length_n = 0;
-            r->discard_body = 1;
-        }
-
         return NGX_OK;
     }
 #endif
@@ -718,8 +708,6 @@ ngx_http_discard_request_body(ngx_http_r
         return NGX_OK;
     }
 
-    r->discard_body = 1;
-
     size = r->header_in->last - r->header_in->pos;
 
     if (size || r->headers_in.chunked) {
diff --git a/src/http/ngx_http_variables.c b/src/http/ngx_http_variables.c
--- a/src/http/ngx_http_variables.c
+++ b/src/http/ngx_http_variables.c
@@ -1196,11 +1196,7 @@ ngx_http_variable_content_length(ngx_htt
         v->no_cacheable = 1;
 
     } else if (r->discard_body) {
-        v->len = 1;
-        v->data = (u_char *) "0";
-        v->valid = 1;
-        v->no_cacheable = 0;
-        v->not_found = 0;
+        v->not_found = 1;
 
     } else if (r->headers_in.content_length_n >= 0) {
         p = ngx_pnalloc(r->pool, NGX_OFF_T_LEN);
diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
--- a/src/http/v2/ngx_http_v2.c
+++ b/src/http/v2/ngx_http_v2.c
@@ -1101,7 +1101,7 @@ ngx_http_v2_state_read_data(ngx_http_v2_
         if (rc != NGX_OK && rc != NGX_AGAIN) {
 
             stream->skip_data = 1;
-            r->headers_in.content_length_n = 0;
+            r->discard_body = 1;
             r->request_body->bufs = NULL;
 
             ngx_http_finalize_request(r, rc);
@@ -3765,7 +3765,7 @@ ngx_http_v2_run_request(ngx_http_request
                       "client prematurely closed stream");
 
         r->stream->skip_data = 1;
-        r->headers_in.content_length_n = 0;
+        r->discard_body = 1;
 
         ngx_http_finalize_request(r, NGX_HTTP_BAD_REQUEST);
         goto failed;
@@ -4199,7 +4199,7 @@ ngx_http_v2_read_client_request_body_han
     if (rc != NGX_OK && rc != NGX_AGAIN) {
 
         r->stream->skip_data = 1;
-        r->headers_in.content_length_n = 0;
+        r->discard_body = 1;
         r->request_body->bufs = NULL;
 
         ngx_http_finalize_request(r, rc);
@@ -4264,7 +4264,7 @@ ngx_http_v2_read_client_request_body_han
 error:
 
     stream->skip_data = 1;
-    r->headers_in.content_length_n = 0;
+    r->discard_body = 1;
     r->request_body->bufs = NULL;
 
     ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
diff --git a/src/http/v3/ngx_http_v3_request.c b/src/http/v3/ngx_http_v3_request.c
--- a/src/http/v3/ngx_http_v3_request.c
+++ b/src/http/v3/ngx_http_v3_request.c
@@ -1292,7 +1292,7 @@ ngx_http_v3_read_client_request_body_han
 
     if (rc >= NGX_HTTP_SPECIAL_RESPONSE) {
 
-        r->headers_in.content_length_n = 0;
+        r->discard_body = 1;
         r->request_body->bufs = NULL;
 
         ngx_http_finalize_request(r, rc);