Gzip in Varnish

default.vcl

sub vcl_recv {
# set to Gzip, deflate or remove entirely
    if (req.http.Accept-Encoding) {
        if (req.url ~ "\.(jpg|jpeg|png|gif|gz|tgz|bz2|tbz|mp3|mp4|ogg)$") {
          unset req.http.Accept-Encoding;
        } elsif (req.http.Accept-Encoding ~ "gzip") {
          set req.http.Accept-Encoding = "gzip";
        } elsif (req.http.Accept-Encoding ~ "deflate") {
          set req.http.Accept-Encoding = "deflate";
        } else {
          unset req.http.Accept-Encoding;
        }
    }
    
sub vcl_backend_response {
# Do not Gzip image files in Varnish
    if (beresp.http.url ~ "\.(jpg|jpeg|png|gif|gz|tgz|bz2|tbz|mp3|mp4|ogg|swf)$") {
     set beresp.do_gzip = false;
    }
    else {
     set beresp.do_gzip = true;
     set beresp.http.X-Cache = "ZIP";
    }
  
# GZip the cached content if possible
    if (beresp.http.content-type ~ "text") {
     set beresp.do_gzip = true;
    }
}

http://www.varnish-cache.org/docs/trunk/phk/gzip.html