--- modules/filters/mod_deflate.c	(revision 687021)
+++ modules/filters/mod_deflate.c	(working copy)
@@ -49,6 +49,7 @@ 
 #include "zlib.h"
 
 static const char deflateFilterName[] = "DEFLATE";
+static const char etagFilterName[] = "ETAG";
 module AP_MODULE_DECLARE_DATA deflate_module;
 
 typedef struct deflate_filter_config_t
@@ -537,6 +538,9 @@ 
         /* For a 304 or 204 response there is no entity included in
          * the response and hence nothing to deflate. */
         if (r->status == HTTP_NOT_MODIFIED || r->status == HTTP_NO_CONTENT) {
+            /* munge the etag only if we had done that when we came in.*/
+            if(apr_table_get(r->notes, "If-None-Match") != NULL)
+                deflate_check_etag(r, "gzip");
             ap_remove_output_filter(f);
             return ap_pass_brigade(f->next, bb);
         }
@@ -735,6 +739,36 @@ 
     return APR_SUCCESS;
 }
 
+static apr_status_t etag_in_filter(ap_filter_t *f,
+                                      apr_bucket_brigade *bb,
+                                      ap_input_mode_t mode,
+                                      apr_read_type_e block,
+                                      apr_off_t readbytes)
+{
+    request_rec *r = f->r;
+    /* Do not disturb clients who aren't interested in gzip
+    */
+    const char* inm;
+    char* gz;
+    const char* accept = apr_table_get(r->headers_in, "Accept-Encoding");
+    ap_remove_input_filter(f); /* go thru only once */
+    if ((accept == NULL) || (ap_strstr_c(accept, "gzip") == NULL)) {
+        return ap_get_brigade(f->next, bb, mode, block, readbytes);
+    }
+
+    /* Do they have a gzip version?
+    */
+    inm = apr_table_get(r->headers_in, "If-None-Match");
+    if ((inm == NULL) || ( (gz = ap_strstr_c(inm, "-gzip")) == NULL )) {
+        return ap_get_brigade(f->next, bb, mode, block, readbytes);
+    }
+
+    *gz = '\0';
+    apr_table_set(r->headers_in, "If-None-Match", apr_pstrdup(r->pool, inm));
+    apr_table_setn(r->notes, "If-None-Match", "1");
+    return ap_get_brigade(f->next, bb, mode, block, readbytes);
+}
+
 /* This is the deflate input filter (inflates).  */
 static apr_status_t deflate_in_filter(ap_filter_t *f,
                                       apr_bucket_brigade *bb,
@@ -1338,6 +1372,8 @@ 
                               AP_FTYPE_RESOURCE-1);
     ap_register_input_filter(deflateFilterName, deflate_in_filter, NULL,
                               AP_FTYPE_CONTENT_SET);
+    ap_register_input_filter(etagFilterName, etag_in_filter, NULL,
+                              AP_FTYPE_CONTENT_SET);
 }
 
 static const command_rec deflate_filter_cmds[] = {