Upstream: avoid closing client connection in edge case. If proxy_cache is enabled, and proxy_no_cache tests true, it was previously possible for the client connection to be closed after a 304. The fix is to recheck r->header_only after the final cacheability is determined, and end the request if no longer cacheable. Example configuration: proxy_cache foo; proxy_cache_bypass 1; proxy_no_cache 1; If a client sends If-None-Match, and the upstream server returns 200 with a matching ETag, no body should be returned to the client. At the start of ngx_http_upstream_send_response proxy_no_cache is not yet tested, thus cacheable is still 1 and downstream_error is set. However, by the time the downstream_error check is done in process_request, proxy_no_cache has been tested and cacheable is set to 0. The client connection is then closed, regardless of keepalive.

/* XPM */
static char * nginx_xpm[] = {
"16 16 2 2",
/* colors */
"   c none",
"GG c #009900",
/* pixels */
"                                ",
"        GGGGGGGGGGGGGGGG        ",
"        GGGGGGGGGGGGGGGG        ",
"      GGGGGGGGGGGGGGGGGGGG      ",
"      GGGGGG        GGGGGG      ",
"    GGGGGG            GGGGGG    ",
"    GGGGGG                      ",
"  GGGGGG      GGGGGGGGGGGGGGGG  ",
"  GGGGGG    GGGGGGGGGGGGGGGGGG  ",
"    GGGGGG    GGGGGGGGGGGGGG    ",
"    GGGGGG            GGGGGG    ",
"      GGGGGG        GGGGGG      ",
"      GGGGGGGGGGGGGGGGGGGG      ",
"        GGGGGGGGGGGGGGGG        ",
"        GGGGGGGGGGGGGGGG        ",
"                                "
};