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Date: Wed, 1 Sep 2004 16:00:27 +0400
From: Gleb Smirnoff <glebius@freebsd.org>
To: hackers@freebsd.org
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Subject: copyin() instead of sooptcopyin()?
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  Dear hackers,

  I have a case, when I need to pass a small argument to kernel,
and receive large reply using getsockopt().

First I get the argument:

	char var[MAX];
	...
	if ((error = sooptcopyin(sopt, var, MAX, 2))
	...

Then I push reply to it using sooptcopyout(). But userland receives it
truncated to MAX. The problem lives in sooptcopyin() implementation,
which changes sopt->sopt_valsize.

Now, in my patch I solve this using bare copyin(). Another approach
may be saving sopt->sopt_valsize before call to sooptcopyin(), and then
restoring it. Not a nice solution however...

The questions are:

1) Is it OK to use bare copyin()? Which hidden problems can arise?
2) Is that correct that soopcopy[in|out]() changes sopt's fields?

-- 
Totus tuus, Glebius.
GLEBIUS-RIPN GLEB-RIPE