From an email message sent by Federico Mena Quintero...

I think I've found a bug in the way the smbcctx.callbacks.auth_fn is
called.

As far as I can tell:

1. You create a SMBCCTX.  You set its ctx->workgroup field to the user's
default workgroup (otherwise, smbc_init_context() will fill it with the
result of lp_workgroup()).

2. You call some method on your context as "my_ctx->foo (...)".  This
may call your auth_fn.

3. There's this code in smbc_open_ctx():

static SMBCFILE *smbc_open_ctx(SMBCCTX *context, const char *fname, int flags, mode_t mode)
	fstring server, share, user, password, workgroup;

	if (smbc_parse_path(context, fname,
                            server, sizeof(server),
                            share, sizeof(share),
                            path, sizeof(path),
                            user, sizeof(user),
                            password, sizeof(password),
                            NULL, 0)) {
		/* error out, etc. */
	}

	/* NOTE HOW THE ABOVE DIDN'T PARSE THE WORKGROUP FROM THE URI */

	fstrcpy(workgroup, context->workgroup);   /* THIS JUST COPIES FROM THE DEFAULT */

	srv = smbc_server(context, server, share, workgroup, user, password);
	...

	/* etc.  Now, in smbc_server(): */

        srv = find_server(context, server, share,
                          workgroup, username, password);

	/* And in find_server(): */

	srv = context->callbacks.get_cached_srv_fn(context, server, share, 
						   workgroup, username);

	if (!auth_called && !srv && (!username[0] || !password[0])) {
		context->callbacks.auth_fn(server, share,
                                           workgroup, sizeof(fstring),
                                           username, sizeof(fstring),
                                           password, sizeof(fstring));

But note how the workgroup that trickles down is the client-supplied
default workgroup, or the result of lp_workgroup(), *NOT* the workgroup
which may be in the URL!

That is, if the URL is "smb://FOO_WORKGROUP;bar_server/sharename/dir",
then the auth_fn will not get FOO_WORKGROUP passed to it.

* Shouldn't smb_parse_path() also return the workgroup, if it is present
in the URI, and the rest of the code should use it if available?  If
not, of course fall back to the default workgroup.

* So, how is auth_fn supposed to guess the correct workgroup?

Gnome-VFS has some convoluted code which first parses the URL on its
own, stores the various parts in semi-global variables, and then fetches
things from there for use in the auth_fn it supplies.