Re: [naviserver-devel] "ns_server active" request IP - proxy aware?

[David O. <da...@qc...>]

Thanks Gustaf,

I can only really reproduce it by hammering my development instance using
apache bench (and only with a concurrency level of >100 after a few hundred
requests) - not very scientific.

The purpose of the filter_dos_check filter is to examine the server load
(via ns_server active) and potentially return a 503 if we're too busy.

However, the ns_server call is the first thing it does. In fact I can strip
the filter down to only do the following and still get the same signal 11
(it also segfaults if returning  filter_ok but takes longer)

proc filter_dos_check { event args } {
    set requests_active [ns_server -server [ns_info server] -pool {} active
-checkforproxy]
    return filter_return
}

Thanks for the patch.

If there's anything I could capture during the segfault which would help
let me know.



On 5 October 2017 at 20:22, Gustaf Neumann <ne...@wu...> wrote:

>
> Hi David,
>
> so far, i could not recreate the problem. By reading the backtrace, the
> problem
> seems to be that the connection has no ns_set for the header fields. This
> is strange,
> since every ConnRun() sets these fields, an these are cleared after the
> ConnRun(),
> while the problem happens within ConnRun().
> So i wonder, how connPtr->headers can be lost. I see from the backtrace,
> that the issue
> happens in a preauth filter named  "filter_dos_check". Can it be, that
> this filter somehow
> causes a cleanup of the connection? I can't see in the code, where this
> might happen.
>
> For the time being, i've protected the crashing function call with test
> for the
> headers and added a debug line for the error.log. So, the crash at this
> very situation should disappear.  But probably, the function should not
> be called in such situations at all, there might be as well other places,
> that depend on the assumption, that the ns_set for the header exists
> during the run.
>
> Do you see anything in your filter code related with this?
> -g
>
>
>
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