parse_filter
if ((ctx.gfilter = parse_filter(&ctx, ctx.gfilter)) == NULL)
if ((ctx.gbasedn = parse_filter(&ctx, ctx.gbasedn)) == NULL)
char * parse_filter(struct auth_ctx *, const char *);
if ((ctx->binddn = parse_filter(ctx, value)) == NULL)
if ((ctx->filter = parse_filter(ctx, value)) == NULL)