Plugin project proposal

[Nicolas Williams]

On Thu, Jul 15, 2010 at 03:06:11PM -0400, Zhanna Tsitkova wrote:
> On Jul 15, 2010, at 2:57 PM, Nicolas Williams wrote:
> >What is used as a key to the table?
> 
> Suppose we have the following v-table for plugin password quality:
> /* PWD_QLTY API */
> typedef struct {
> int version;
> char plugin_id[MAX_PL_NAME_LEN];
> kadm5_ret_t (*pwd_qlty_init)(kadm5_server_handle_t);
> void (*pwd_qlty_cleanup)();
>  kadm5_ret_t (*pwd_qlty_check)(kadm5_server_handle_t, char*,int,
> kadm5_policy_ent_t, krb5_principal);
> } plugin_pwd_qlty;
> 
> Then the key may be "pwd_qlty_check"

I think this is still ridiculously complicated.

It'd all be simpler with a dlsym() over v-table approach, but even with
a v-table approach it'd be simpler to have a function like this:

kadm5_ret_t
pwd_qlty_check(kadm5_server_handle_t h, char *pw, int what_is_this_arg?,
	kadm5_policy_ent_t pol, krb5_principal princ)
{
	int i;
	kadm5_ret_t ret = <default_return_value>;

	if (pwd_qlty_plugin_count == -1) {
		LOAD_PWD_QLTY_PLUGINS();
	}

	if (pwd_qlty_plugin_count == 0)
		return (ret);

	for (i = 0; i < pwd_qlty_plugin_count; i++) {
		if (pwd_qlty_plugins[i].version == 1) {
			ret = pwd_qlty_plugins[i].vtable->pwd_qlty_check(h,
			    what_is_this_arg?, pol, princ);
		} else if pwd_qlty_plugins[i].version == 2) {
			...
		} else ... {
			...
		}
		if (ret != <OK>)
			return (ret);
	}

	return(ret);
}

That's it.  Initially there will be a single version, of course, so the
actual code would be a bit simpler.

Also, if you need to get a per-plugin handle, you could, and it'd not be
much more complicated:


kadm5_ret_t
pwd_qlty_check(kadm5_server_handle_t h, char *pw, int what_is_this_arg?,
	kadm5_policy_ent_t pol, krb5_principal princ)
{
	int i;
	kadm5_ret_t ret = <default_return_value>;

	if (pwd_qlty_plugin_count == -1) {
		LOAD_PWD_QLTY_PLUGINS();
	}

	if (pwd_qlty_plugin_count == 0)
		return (ret);

	for (i = 0; i < pwd_qlty_plugin_count; i++) {
		if (pwd_qlty_plugins[i].version == 1) {
			if (pwd_qlty_plugins[i].handle == NULL) {
				pwd_qlty_plugins[i].handle =
				    pwd_qlty_plugins[i].vtable->pwd_qlty_init(h);
			}
			ret = pwd_qlty_plugins[i].vtable->pwd_qlty_check(h,
			    what_is_this_arg?, pol, princ);
		} else if pwd_qlty_plugins[i].version == 2) {
			...
		} else ... {
			...
		}
		if (ret != <OK>)
			return (ret);
	}

	return(ret);
}

Or you could move the pwd_qlty_init thing into LOAD_PWD_QLTY_PLUGINS().

Either way what you're left with is pretty simple.

Nico
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