I am trying to stretch the size of an `iframe` to fill the remaining space within my web app. I know the maximum space is being allocated for the `div` (by adding a border), but the `iframe` height itself is not expanding to fill the entire vertical height.

The problem is the `row content` `iframe` is not filling the entire vertical space, even though the flexbox is allocating that space appropriately.

Any ideas?

```css
.box {
  display: flex;
  flex-flow: column;
  height: 100vh;
}
.box .row.header {
  flex: 0 1 auto;
}
.box .row.content {
  flex: 1 1 auto;
}
.box .row.footer {
  flex: 0 1 40px;
}
.row.content iframe {
  width: 100%;
  border: 0;
}
```

```html
<div class="box">
  <div class="row header">
    <h1>Event Details</h1>
    <div id="container">
      <h5>Test</h5>
    </div>
    <div data-role="navbar">
      <ul>
        <li><a href="players.html" class="ui-btn-active ui-state-persist">Players</a>
        </li>
        <li><a href="games.html">Games</a>
        </li>
        <li><a href="chat.html">Chat</a>
        </li>
      </ul>
    </div>
  </div>
  <div class="row content">
    <iframe src="players.html"></iframe>
  </div>
  <div class="row footer">
    <p><b>footer</b> (fixed height)</p>
  </div>
</div>
```