Implementing websocket support

Websockets is a technology for creating a bidirectional stream-based channel over HTTP.

To run websockets through Varnish you need to pipe it, and copy the Upgrade header. Use the following VCL config to do so:

sub vcl_pipe {
     if (req.http.upgrade) {
         set bereq.http.upgrade = req.http.upgrade;
     }
}
sub vcl_recv {
     if (req.http.Upgrade ~ "(?i)websocket") {
         return (pipe);
     }
}