Provided by:
linux-doc-2.6.15_2.6.15-23.39_all 
NAME
sk_chk_filter - verify socket filter code
SYNOPSIS
int sk_chk_filter (struct sock_filter * filter, int flen);
ARGUMENTS
filter filter to verify
flen length of filter
DESCRIPTION
Check the user’s filter code. If we let some ugly filter code slip
through kaboom! The filter must contain no references or jumps that are
out of range, no illegal instructions and no backward jumps. It must
end with a RET instruction
Returns 0 if the rule set is legal or a negative errno code if not.