Date: Wed, 4 Aug 1999 11:04:06 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Doug Rabson <dfr@nlsystems.com> Cc: "Brian F. Feldman" <green@freebsd.org>, Mike Smith <mike@smith.net.au>, Ollivier Robert <roberto@keltia.freenix.fr>, hackers@freebsd.org Subject: Re: Jail syscalls Message-ID: <199908041804.LAA31039@apollo.backplane.com> References: <Pine.BSF.4.10.9908040949300.385-100000@salmon.nlsystems.com>
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:The argument for versioning is not simply because the size of ip_number
:might change (it should be a sockaddr) but because other fields might be
:added or removed. To avoid allocating a new syscall whenever this happens,
:the structure should be versioned.
:
:Putting sizeof(whatever) at the beginning of the structure works
:surprisingly well as a versioning system.
:
:--
:Doug Rabson Mail: dfr@nlsystems.com
:Nonlinear Systems Ltd. Phone: +44 181 442 9037
I think we basically have two choices:
* Pass the sizeof(struct) as part of the system call. Please, not as
part of the structure! That would make this syscall the odd-man-out
compared to all the other syscalls that take size arguments.
* Make the first field of the structure a real version id, one that is
taken from the same include file that the structure was defined in,
and require that the field be filled in.
e.g.
#include <sys/jail.h>
struct jail fubar = { JAIL_VERSION };
I kinda like the second choice the best but the first choice is what most
other system calls use.
-Matt
Matthew Dillon
<dillon@backplane.com>
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