varnish.deliver.vcl

sub vcl_deliver {
    std.log("userid:" + cookie.get("userid"));
    std.log("url:" + req.url);

    set resp.http.Access-Control-Allow-Origin = "http://your.site.here";
    set resp.http.Access-Control-Allow-Credentials = "true";

    if (resp.http.Content-Type ~ "application/vnd.apple.mpegurl") {
        # Set a userid cookie on the client that lives for 60 minutes.
        set resp.http.Set-Cookie = "userid=" + cookie.get("userid") + "; Expires=" + cookie.format_rfc1123(now, 60m) + "; httpOnly";
    }
    return(deliver);
}