linux-kernel - getsockopt/setsockopt with SO_RCVBUF and SO

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <50052FFE.2060109@pu-pm.univ-fcomte.fr>
Date:	Tue, 17 Jul 2012 11:27:26 +0200
From:	Eugen Dedu <Eugen.Dedu@...pm.univ-fcomte.fr>
To:	linux-kernel@...r.kernel.org
Subject: getsockopt/setsockopt with SO_RCVBUF and SO_SNDBUF "non-standard"
 behaviour

Hi all,

I looked on Internet and at the old thread 
http://lkml.indiana.edu/hypermail/linux/kernel/0108.0/0275.html, 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;
#endif

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?

Cheers,
-- 
Eugen Dedu
http://eugen.dedu.free.fr
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/