[ruby-core:38682] Re: [Ruby 1.9 - Bug #5138][Open] Add nonblocking IO that does not use exceptions for EOF and EWOULDBLOCK

Urabe Shyouhei <[e-mail]> wrote:
> (08/02/2011 08:48 AM), Eric Wong wrote:
> > Urabe Shyouhei <[e-mail]> wrote:
> >> (08/02/2011 08:35 AM), Eric Wong wrote:
> >>> Urabe Shyouhei <[e-mail]> wrote:
> >>>> (08/02/2011 08:14 AM), Eric Wong wrote:
> >>>>> Urabe Shyouhei <[e-mail]> wrote:
> >>>>>> So when you  do a read loop,  nothing bothers you, as long  as you use
> >>>>>> readpartial.
> >>>>>
> >>>>> That use of select + readpartial is unsafe.
> >>>>
> >>>> Unsafe how?  readpatial works even without no data on a buffer.
> >>>
> >>> readpartial will block if there's no data readable, potentially freezing
> >>> the whole process.
> >>
> >> Yes but that's not catastrophic.  The peer side is sending a data anyway.
> >> Checksum incorrect packets are dropped but retransmitted sooner or later.
> >> The process blocks during that retransmission.  That won't last so long.
> > 
> > Malicious clients can take advantage of this to launch a denial-of-service
> > attack
> 
> ... even when you do a blocking IO.  TCP's having problems on malicious
> clients is a known issue of the protocol I think.

Yes, but I think one should be as defensive-as-possible for these
things.

> > Also, networks should never be considered reliable and simple
> > operations can fail or take a long time.
> 
> is that the problem we are talking about here?  Does Yehuda need a DoS-
> proven read loop? or he just want a fast variant of read_nonblock?

I don't know what Yehuda needs, but code proliferates and I would hate
to see reliance on fragile assumptions badly affect something down
the line that went beyond Yehuda's original need.

-- 
Eric Wong