Hello!

On Mon, Nov 05, 2012 at 10:18:28PM -0800, agentzh wrote:

> Hello!
>
> smallfish and I both ran into a small issue with the
> ngx_http_upstream_test_connect which does not catch errors like
> "Connection refused" when kqueue is used.
>
> The current logic only checks c->write->pending_eof but this error
> actually produced a read event on (at least) both Mac OS X and
> FreeBSD.
>
> I've attached a simple patch (for nginx 1.2.4) to fix this by checking
> both the read and write events.
>
> To reproduce the issue, please consider the following Nginx
> configuration snippet (assuming nothing is listening on the local port
> 1234):
>
> location = /t {
> proxy_pass http://127.0.0.1:1234/;
> }
>
> Accessing /t gives the following message in error.log:
>
> [error] 28474#0: *1 kevent() reported about an closed connection
> (61: Connection refused) while reading response header from upstream
>
> We can see that ngx_http_upstream missed it in
> ngx_http_upstream_test_connect but caught it when reading the
> (upstream) response header.
>
> After applying my patch, Nginx can now catch it in the context of connecting:
>
> [error] 34067#0: *1 kevent() reported that connect() failed (61:
> Connection refused) while connecting to upstream

Thanks for catching this!

> --- nginx-1.2.4/src/http/ngx_http_upstream.c 2012-08-06 10:34:08.000000000 -0700
> +++ nginx-1.2.4-patched/src/http/ngx_http_upstream.c 2012-11-05
> 21:17:38.000000000 -0800
> @@ -1808,10 +1808,22 @@ ngx_http_upstream_test_connect(ngx_conne
>
> #if (NGX_HAVE_KQUEUE)
>
> + ngx_event_t *ev;
> +
> if (ngx_event_flags & NGX_USE_KQUEUE_EVENT) {
> if (c->write->pending_eof) {
> + ev = c->write;
> +
> + } else if (c->read->pending_eof) {
> + ev = c->read;
> +
> + } else {
> + ev = NULL;
> + }
> +
> + if (ev) {
> c->log->action = "connecting to upstream";
> - (void) ngx_connection_error(c, c->write->kq_errno,
> + (void) ngx_connection_error(c, ev->kq_errno,
> "kevent() reported that connect() failed");
> return NGX_ERROR;
> }

I don't see a reason to introduce another local variable here,
what about something like

--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -1809,9 +1809,16 @@ ngx_http_upstream_test_connect(ngx_conne
#if (NGX_HAVE_KQUEUE)

if (ngx_event_flags & NGX_USE_KQUEUE_EVENT) {
- if (c->write->pending_eof) {
+ if (c->write->pending_eof || c->read->pending_eof) {
+ if (c->write->pending_eof) {
+ err = c->write->kq_errno;
+
+ } else {
+ err = c->read->kq_errno;
+ }
+
c->log->action = "connecting to upstream";
- (void) ngx_connection_error(c, c->write->kq_errno,
+ (void) ngx_connection_error(c, err,
"kevent() reported that connect() failed");
return NGX_ERROR;
}

instead?

--
Maxim Dounin
http://nginx.com/support.html

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