[PATCH] Make ngx_http_upstream provide a way to expose errors after sending out the response header

[agentzh]

Hello!

Here attaches V2 of my patch to make ngx_http_upstream detect
truncated responses. Changes since V1 are as follows:

1. No longer change r->headers_out.status.
2. Just skip sending the last buf (i.e., setting the last_buf or
last_in_chain flags) for errors.
3. Use u->length and u->pipe->length to test good "eof" instead of
testing u->headers_in.content_length_n.

Things that I'm not sure are

1. Whether to emit an error message when truncation happens. (This is
not implemented in my patch.)
2. Whether to use NGX_HTTP_BAD_GATEWAY to finalize the upstream
instead of NGX_ERROR.

Comments are highly appreciated as always :)

Thanks!
-agentzh

--- nginx-1.2.7/src/http/ngx_http_upstream.c 2013-02-11 06:39:49.000000000 -0800
+++ nginx-1.2.7-patched/src/http/ngx_http_upstream.c 2013-04-05
12:24:34.108742922 -0700
@@ -2399,7 +2399,7 @@ ngx_http_upstream_process_non_buffered_u

     if (c->read->timedout) {
         ngx_connection_error(c, NGX_ETIMEDOUT, "upstream timed out");
-        ngx_http_upstream_finalize_request(r, u, 0);
+        ngx_http_upstream_finalize_request(r, u, NGX_HTTP_GATEWAY_TIME_OUT);
         return;
     }

@@ -2446,13 +2446,20 @@ ngx_http_upstream_process_non_buffered_r
             if (u->busy_bufs == NULL) {

                 if (u->length == 0
-                    || upstream->read->eof
-                    || upstream->read->error)
+                    || (upstream->read->eof
+                        && u->length == -1
+                        && u->pipe
+                        && u->pipe->length == -1))
                 {
                     ngx_http_upstream_finalize_request(r, u, 0);
                     return;
                 }

+                if (upstream->read->eof || upstream->read->error) {
+                    ngx_http_upstream_finalize_request(r, u, NGX_ERROR);
+                    return;
+                }
+
                 b->pos = b->start;
                 b->last = b->start;
             }
@@ -2720,7 +2727,9 @@ ngx_http_upstream_process_request(ngx_ht

 #endif

-        if (p->upstream_done || p->upstream_eof || p->upstream_error) {
+        if (p->upstream_done
+            || (p->upstream_eof && u->length == -1 && p->length == -1))
+        {
             ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                            "http upstream exit: %p", p->out);
 #if 0
@@ -2729,6 +2738,14 @@ ngx_http_upstream_process_request(ngx_ht
             ngx_http_upstream_finalize_request(r, u, 0);
             return;
         }
+
+        if (p->upstream_eof || p->upstream_error) {
+            ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
+                           "http upstream exit: %p", p->out);
+
+            ngx_http_upstream_finalize_request(r, u, NGX_ERROR);
+            return;
+       }
     }

     if (p->downstream_error) {
@@ -3087,7 +3104,8 @@ ngx_http_upstream_finalize_request(ngx_h

     if (u->header_sent
         && rc != NGX_HTTP_REQUEST_TIME_OUT
-        && (rc == NGX_ERROR || rc >= NGX_HTTP_SPECIAL_RESPONSE))
+        && rc != NGX_HTTP_GATEWAY_TIME_OUT
+        && rc >= NGX_HTTP_SPECIAL_RESPONSE)
     {
         rc = 0;
     }
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