Question about implementation of Unix FD passing

[Thiago Macieira]

On domingo, 10 de fevereiro de 2013 14.34.38, Georg Reinke wrote:
> However, because of the special semantics of out-of-band data on Unix
> sockets, one has to read all data in one operation as remaining data is
> discarded. That means that the buffer for the out-of-band data must big
> enough to hold the greatest number of file descriptors that can be
> possibly transferred, which is 2^32 (according to the spec), in order
> to guarantee that no data is discarded.
> 
> While the actual size probably is much lower because of some kernel
> limit, this behaviour still seems odd to me. So my question is: Is this
> intended or have I misunderstood anything or made wrong assumptions
> anywhere?

It's not possible to query the system to find out how many file descriptors were 
passed. Since the number is most often very small, the reference 
implementation passes a buffer of 1024 entries.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel Open Source Technology Center
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