[Python-Dev] the new 2.3a1 settimeout() with httplib and SSL

[Ben Laurie]

Geoffrey Talvola wrote:
> Ben Laurie [mailto:ben@algroup.co.uk] wrote:
> 
>>Guido van Rossum wrote:
>>
>>>Hm, from that page it looks like the internal implementation may
>>>actually repeatedly read from the socket, until it has processed a
>>>full 16K block.  But I may be mistaken, since it also refers to a
>>>non-blocking underlying "BIO", whatever that is. :-(
>>
>>BIO is OpenSSL's I/O abstraction - if you have a nonblocking 
>>one, then 
>>SSL_read() will return when a read returns nothing, and if you want 
>>SSL_read() to not block, then you pretty much have to use a 
>>non-blocking 
>>BIO (because even if select() says there's data, there may 
>>not be enough 
>>to actually return any via SSL_read()).
> 
> 
> That's OK, I think, because what we care about with timeouts is detecting
> when there is _no_ activity on the socket for more than N seconds, and
> select() does detect that situation properly.
> 
> 
>>I can help out here if there's still a problem.
> 
> 
> If you'd like, you could quickly review the latest checkin here -- I have no
> prior experience with OpenSSL so that might be prudent:
> 
> http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/python/python/dist/src/Module
> s/_ssl.c
> 
> But it seems to work fine.

Yeah, but there are corner cases where it won't. If the other end dies 
partway through sending an SSL record, then your select will succeed, 
but the SSL_read will block forever (or at least until the socket 
closes). You do need to put the socket and BIO into a non-blocking mode 
for this to work properly.

I can't remember whether you get an error or a 0 back (I think its an 
error) when the socket would block, but in any case, that would need to 
be handled (presumably by going back around for the remaining time).

If you need more info, I can find it :-)

Cheers,

Ben.

-- 
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