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From William A Rowe Jr <wr...@rowe-clan.net>
Subject Re: ap_get_status_line(int)
Date Fri, 04 Nov 2016 13:09:29 GMT
On Thu, Nov 3, 2016 at 12:51 PM, Stefan Eissing <
stefan.eissing@greenbytes.de> wrote:

> Like to get your opinion:
>
> ap_get_status_line(int) converts any status code it does not know into a
> 500. This is fine for the use cases we had so far, although it can be
> discussed if it is a good idea, too strict or whatnot. But I do not want to
> go down that rathole...
>
> My question is how httpd should handle unknown codes coming from an
> upstream server. Currently:
> - mod_proxy_http sends it on (tested for intermediate responses)
> - mod_proxy_http2 sends a 500 server error
>
> The reason for this is that mod_proxy_http2 generates a status line using
> ap_get_status_line() while mod_proxy_http can parse that line from the
> upstream response.
>
> So, we have different handling of status code acceptance in proxies
> responses for HTTP/1.x and HTTP/2. This should not be. Question is, do we
> need another function which returns NULL for such cases, so the caller can
> decide to give up or work around it?
>

We really shouldn't be losing the metadata. A 500 error means something
very specific, and although it can represent unrecognized 5xx codes,
it isn't applicable to unrecognized, newer 1xx-4xx codes.

What would a non-three-digit, >599 response look like? Perhaps we have
a good case for a NULL response or a generic 500.

The actually callers to this function are fairly limited;

./server/core.c:                    r->status_line =
ap_get_status_line(r->status);
./modules/http2/h2_proxy_session.c:                r->status_line =
ap_get_status_line(r->status);
./modules/dav/main/mod_dav.c:    r->status_line =
ap_get_status_line(status);
./modules/dav/main/mod_dav.c:
 ap_get_status_line(response->status),
./modules/arch/win32/mod_isapi.c:        cid->r->status_line =
ap_get_status_line(cid->r->status);
./modules/arch/win32/mod_isapi.c:        cid->r->status_line =
ap_get_status_line(cid->r->status);
./modules/arch/win32/mod_isapi.c:        cid->r->status_line =
ap_get_status_line(cid->r->status);
./modules/arch/win32/mod_isapi.c:        cid->r->status_line =
ap_get_status_line(cid->r->status);
./modules/arch/win32/mod_isapi.c:        cid->r->status_line =
ap_get_status_line(cid->r->status);
./modules/http/http_filters.c:
 ap_get_status_line(HTTP_CONTINUE), CRLF CRLF, NULL);
./modules/http/http_filters.c:        r->status_line =
ap_get_status_line(r->status);
./modules/http/http_filters.c:        const char *tmp =
ap_get_status_line(r->status);

Replacing these with a more robust function that doesn't throw away
newer response codes would be a good thing, but note that they expect
to have some valid result, a NULL result will probably be surprising (and
this goes for 3rd party modules as well.)

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