Patch for: http://trac.lighttpd.net/trac/ticket/1545

Allows the headers to be used by mod_extforward to be specified in config.
For example for use with a Zeus ZXTM loadbalancer:

extforward.headers = ("X-Cluster-Client-Ip")


--- lighttpd-1.4.19/src/mod_extforward.c.extforward	2008-03-02 13:59:18.000000000 +0100
+++ lighttpd-1.4.19/src/mod_extforward.c	2008-03-12 15:18:28.000000000 +0100
@@ -80,6 +80,7 @@
 
 typedef struct {
 	array *forwarder;
+	array *headers;
 } plugin_config;
 
 typedef struct {
@@ -135,6 +136,7 @@
 			if (!s) continue;
 
 			array_free(s->forwarder);
+			array_free(s->headers);
 
 			free(s);
 		}
@@ -154,7 +156,8 @@
 	size_t i = 0;
 
 	config_values_t cv[] = {
-		{ "extforward.forwarder",             NULL, T_CONFIG_ARRAY, T_CONFIG_SCOPE_CONNECTION },       /* 0 */
+		{ "extforward.forwarder",       NULL, T_CONFIG_ARRAY, T_CONFIG_SCOPE_CONNECTION },       /* 0 */
+		{ "extforward.headers",         NULL, T_CONFIG_ARRAY, T_CONFIG_SCOPE_CONNECTION },       /* 1 */
 		{ NULL,                         NULL, T_CONFIG_UNSET, T_CONFIG_SCOPE_UNSET }
 	};
 
@@ -167,8 +170,10 @@
 
 		s = calloc(1, sizeof(plugin_config));
 		s->forwarder    = array_init();
+		s->headers      = array_init();
 
 		cv[0].destination = s->forwarder;
+		cv[1].destination = s->headers;
 
 		p->config_storage[i] = s;
 
@@ -187,6 +192,7 @@
 	plugin_config *s = p->config_storage[0];
 
 	PATCH(forwarder);
+	PATCH(headers);
 
 	/* skip the first, the global context */
 	for (i = 1; i < srv->config_context->used; i++) {
@@ -202,6 +208,8 @@
 
 			if (buffer_is_equal_string(du->key, CONST_STR_LEN("extforward.forwarder"))) {
 				PATCH(forwarder);
+			} else if (buffer_is_equal_string(du->key, CONST_STR_LEN("extforward.headers"))) {
+				PATCH(headers);
 			}
 		}
 	}
@@ -335,6 +343,8 @@
 URIHANDLER_FUNC(mod_extforward_uri_handler) {
 	plugin_data *p = p_d;
 	data_string *forwarded = NULL;
+	data_string *ds;
+	size_t k;
 #ifdef HAVE_IPV6
 	char b2[INET6_ADDRSTRLEN + 1];
 	struct addrinfo *addrlist = NULL;
@@ -354,15 +364,22 @@
 				"-- mod_extforward_uri_handler called");
 	}
 
-	if ((NULL == (forwarded = (data_string *) array_get_element(con->request.headers,"X-Forwarded-For")) &&
-	     NULL == (forwarded = (data_string *) array_get_element(con->request.headers,  "Forwarded-For")))) {
+	for(k=0; k<p->conf.headers->used; k++) {
+		ds = (data_string *)p->conf.headers->data[k];
+		if (NULL != (forwarded = (data_string*)array_get_element(con->request.headers, ds->value->ptr))) break;
+	}
 
-		if (con->conf.log_request_handling) {
-			log_error_write(srv, __FILE__, __LINE__, "s", 
-					"no X-Forwarded-For|Forwarded-For: found, skipping");
-		}
+	if(NULL == forwarded) {
+		if ((NULL == (forwarded = (data_string *) array_get_element(con->request.headers,"X-Forwarded-For")) &&
+			NULL == (forwarded = (data_string *) array_get_element(con->request.headers,  "Forwarded-For"))) ||
+			(p->conf.headers->used > 0)) {
 
-		return HANDLER_GO_ON;
+			if (con->conf.log_request_handling) {
+				log_error_write(srv, __FILE__, __LINE__, "s", "no forward header found, skipping");
+			}
+
+			return HANDLER_GO_ON;
+		}
 	}
 
 #ifdef HAVE_IPV6