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From Graham Leggett <>
Subject Re: svn commit: r1706275 - /httpd/httpd/trunk/modules/ssl/ssl_engine_io.c
Date Wed, 07 Oct 2015 15:59:27 GMT
On 07 Oct 2015, at 5:53 PM, Jim Jagielski <> wrote:

>> As I understand we’re using openssl in non blocking mode, which means that openssl
will ask us permission before attempting any read or write.
>> The core will then in turn either read or write as requested by openssl based on
>> If openssl has a bug and reads/writes without first asking permission we’ll block,
but by the same token if openssl as asking us permission using SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE
and we’re ignoring openssl, we’ll block for the same reason.
> But certainly these are situations which it's "safer" to block
> in any case, right? Of course, they could also be vectors for some
> sort of DDoS, but even then, that would be relying on pretty
> nasty bugs.

The blocking isn’t really the problem, it’s accidentally waiting for a socket to be readable
when openssl asked you to tell it when the socket is writable.

I suspect turning on the “flush” is masking a bug.


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