[lxc-devel] [PATCH] lxc-commands: add a comment explaining CMD_* rules

[Stéphane Graber]

On Tue, Sep 03, 2013 at 08:08:39AM -0500, Serge Hallyn wrote:
> We wish to ensure that, henceforth, newer lxc tools are always compatible
> with older lxc monitors.  Add a comment to commands.c to explain the
> rule we wish to enforce to this end.
> 
> Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>

Acked-by: Stéphane Graber <stgraber at ubuntu.com>

> ---
>  src/lxc/commands.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/src/lxc/commands.c b/src/lxc/commands.c
> index a7981ba..aad376a 100644
> --- a/src/lxc/commands.c
> +++ b/src/lxc/commands.c
> @@ -59,6 +59,16 @@
>   * Each command is wrapped in a ancillary message in order to pass
>   * a credential making possible to the server to check if the client
>   * is allowed to ask for this command or not.
> + *
> + * IMPORTANTLY: Note that semantics for current commands are fixed.  If you
> + * wish to make any changes to how, say, LXC_CMD_GET_CONFIG_ITEM works by
> + * adding information to the end of cmd.data, then you must introduce a new
> + * LXC_CMD_GET_CONFIG_ITEM_V2 define with a new number.  You may wish to
> + * also mark LXC_CMD_GET_CONFIG_ITEM deprecated in commands.h.
> + *
> + * This is necessary in order to avoid having a newly compiled lxc command
> + * communicating with a running (old) monitor from crashing the running
> + * container.
>   */
>  
>  lxc_log_define(lxc_commands, lxc);
> -- 
> 1.8.1.2
> 
> 
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-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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