From 2fbdc4ae460b00ac754ca580ac1c0102d4c9e197 Mon Sep 17 00:00:00 2001
From: Andre Malo <nd@apache.org>
Date: Sat, 1 Mar 2003 23:57:32 +0000
Subject: [PATCH] Extend mod_negotiation to evaluate the environment variables
 no-gzip and gzip-only-text/html the same way as mod_deflate does.

(it drops all non-identity encodings, not only gzip)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@98871 13f79535-47bb-0310-9956-ffa450edef68
---
 CHANGES                           |  4 +++
 modules/mappers/mod_negotiation.c | 51 +++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/CHANGES b/CHANGES
index 559c078738..ce449f3e8a 100644
--- a/CHANGES
+++ b/CHANGES
@@ -2,6 +2,10 @@ Changes with Apache 2.1.0-dev
 
   [Remove entries to the current 2.0 section below, when backported]
 
+  *) Extend mod_negotiation to evaluate the environment variables
+     no-gzip and gzip-only-text/html the same way as mod_deflate does.
+     [André Malo]
+
   *) Prevent endless loops of internal redirects in mod_rewrite by
      aborting after exceeding a limit of internal redirects. The
      limit defaults to 10 and can be changed using the RewriteOptions
diff --git a/modules/mappers/mod_negotiation.c b/modules/mappers/mod_negotiation.c
index 34336185ce..6f439e757f 100644
--- a/modules/mappers/mod_negotiation.c
+++ b/modules/mappers/mod_negotiation.c
@@ -101,6 +101,11 @@ typedef struct {
 
 #define FLP_DEFAULT  FLP_PREFER
 
+/* env evaluation
+ */
+#define DISCARD_ALL_ENCODINGS 1  /* no-gzip */
+#define DISCARD_ALL_BUT_HTML  2  /* gzip-only-text/html */
+
 module AP_MODULE_DECLARE_DATA negotiation_module;
 
 static void *create_neg_dir_config(apr_pool_t *p, char *dummy)
@@ -2226,18 +2231,56 @@ static int variant_has_language(var_rec *variant, const char *lang)
     return 0;
 }
 
+/* check for environment variables 'no-gzip' and
+ * 'gzip-only-text/html' to get a behaviour similiar
+ * to mod_deflate
+ */
+static int discard_variant_by_env(var_rec *variant, int discard)
+{
+    if (   is_identity_encoding(variant->content_encoding)
+        || !strcmp(variant->content_encoding, "identity")) {
+        return 0;
+    }
+
+    return (   (discard == DISCARD_ALL_ENCODINGS)
+            || (discard == DISCARD_ALL_BUT_HTML
+                && (!variant->mime_type
+                    || strncmp(variant->mime_type, "text/html", 9))));
+}
+
 static int best_match(negotiation_state *neg, var_rec **pbest)
 {
     int j;
     var_rec *best;
     float bestq = 0.0f;
     enum algorithm_results algorithm_result;
+    int may_discard = 0;
 
     var_rec *avail_recs = (var_rec *) neg->avail_vars->elts;
 
+    /* fetch request dependent variables
+     * prefer-language: prefer a certain language.
+     */
     const char *preferred_language = apr_table_get(neg->r->subprocess_env,
                                                    "prefer-language");
 
+    /* no-gzip: do not send encoded documents */
+    if (apr_table_get(neg->r->subprocess_env, "no-gzip")) {
+        may_discard = DISCARD_ALL_ENCODINGS;
+    }
+
+    /* gzip-only-text/html: send encoded documents only
+     * if they are text/html. (no-gzip has a higher priority).
+     */
+    else {
+        const char *env_value = apr_table_get(neg->r->subprocess_env,
+                                              "gzip-only-text/html");
+
+        if (env_value && !strcmp(env_value, "1")) {
+            may_discard = DISCARD_ALL_BUT_HTML;
+        }
+    }
+
     set_default_lang_quality(neg);
 
     /*
@@ -2254,6 +2297,14 @@ static int best_match(negotiation_state *neg, var_rec **pbest)
         for (j = 0; j < neg->avail_vars->nelts; ++j) {
             var_rec *variant = &avail_recs[j];
 
+            /* if this variant is encoded somehow and there are special
+             * variables set, we do not negotiate it. see above.
+             */
+            if (   may_discard
+                && discard_variant_by_env(variant, may_discard)) {
+                continue;
+            }
+
             /* if a language is preferred, but the current variant
              * is not in that language, then drop it for now
              */
-- 
2.40.0