getsockopt/setsockopt with SO_RCVBUF and SO_SNDBUF "non-standard"behaviour

From: Eugen Dedu
Date: Tue Jul 17 2012 - 05:35:03 EST

Hi all,

I looked on Internet and at the old thread, but the issue is still not settled as far as I see.

I need to have the highest memory available for snd/rcv buffer and I need to know/confirm how much it allocated for my process (how much I can use).

So with Linux we need to do something like:
setsockopt (..., SO_RCVBUF, 256000, ...)
getsockopt (..., SO_RCVBUF, &i, ...)
i /= 2;

where i is the size I am looking for.

Now, to make this code work for other OSes it should be changed to:
setsockopt (..., SO_RCVBUF, 256000, ...)
getsockopt (..., SO_RCVBUF, &i, ...)
#ifdef LINUX
i /= 2;

First question, is this code correct? If not, what code gives the amount of memory useable for my process?

Second, it seems to me that linux is definitely "non-standard" here. Saying that linux uses twice as memory has nothing to do with that, since getsockopt should return what the application can count on, not what is the internal use. It is like a hypothetical malloc (10) would return not 10, but 20 (including meta-information). Is that right?

Eugen Dedu
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