Making SSH_AUTH_SOCK Work Between Detaches in Tmux

I make heavy use of SSH agent forwarding in my workflow. However, sometimes you'll start a tmux session, do some work, and detach it. When you come back later, whether it's an hour, a day, or a month, your SSH_AUTH_SOCK within the session will no longer be valid, and you'll need to input your password every time you want to do something involving SSH. I came up with a simple solution a while back; if you drop this in your .bashrc, it should just work:

if [ ! -z "$SSH_AUTH_SOCK" -a "$SSH_AUTH_SOCK" != "$HOME/.ssh/agent_sock" ] ; then
    unlink "$HOME/.ssh/agent_sock" 2>/dev/null
    ln -s "$SSH_AUTH_SOCK" "$HOME/.ssh/agent_sock"
    export SSH_AUTH_SOCK="$HOME/.ssh/agent_sock"

This snippet should also work with GNU screen.

This technique is simple, but it is not without its quirks, however:

Let me know if you have any suggestions for improvement!