Enforce the per-vhost server limit.

Index: apache2.2/server/mpm/experimental/itk/itk.c
===================================================================
--- apache2.2.orig/server/mpm/experimental/itk/itk.c
+++ apache2.2/server/mpm/experimental/itk/itk.c
@@ -156,6 +156,7 @@ typedef struct
 	uid_t uid;
 	gid_t gid;
 	char *username;
+	int max_clients_vhost;
 } itk_server_conf;
 
 module AP_MODULE_DECLARE_DATA mpm_itk_module;
@@ -1393,6 +1394,23 @@ static int itk_post_read(request_rec *r)
     itk_server_conf *sconf =
         (itk_server_conf *) ap_get_module_config(r->server->module_config, &mpm_itk_module);
 
+    /* Enforce MaxClientsVhost. */
+    if (sconf->max_clients_vhost > 0) {
+        int i, num_other_servers = 0;
+        for (i = 0; i < ap_daemons_limit; ++i) {
+            worker_score *ws = &ap_scoreboard_image->servers[i][0];
+            if (ws->status >= SERVER_BUSY_READ && strncmp(ws->vhost, r->server->server_hostname, 31) == 0)
+                ++num_other_servers;
+        }
+
+        if (num_other_servers > sconf->max_clients_vhost) {
+            ap_log_error(APLOG_MARK, APLOG_WARNING, 0, NULL, \
+                "MaxClientsVhost reached for %s, refusing client.",
+                r->server->server_hostname);
+            return HTTP_SERVICE_UNAVAILABLE;
+        }
+    }
+
     strncpy(ap_scoreboard_image->servers[my_child_num][0].vhost, r->server->server_hostname, 31);
     ap_scoreboard_image->servers[my_child_num][0].vhost[31] = 0;
 
@@ -1575,6 +1593,14 @@ static const char *assign_user_id (cmd_p
     return NULL;
 }
 
+static const char *set_max_clients_vhost (cmd_parms *cmd, void *dummy, const char *arg)   
+{
+    itk_server_conf *sconf =
+        (itk_server_conf *) ap_get_module_config(cmd->server->module_config, &mpm_itk_module);
+    sconf->max_clients_vhost = atoi(arg);
+    return NULL;
+}  
+
 static const command_rec itk_cmds[] = {
 UNIX_DAEMON_COMMANDS,
 LISTEN_COMMANDS,
@@ -1590,6 +1616,8 @@ AP_INIT_TAKE1("ServerLimit", set_server_
               "Maximum value of MaxClients for this run of Apache"),
 AP_INIT_TAKE2("AssignUserID", assign_user_id, NULL, RSRC_CONF,
               "Tie a virtual host to a specific child process."),
+AP_INIT_TAKE1("MaxClientsVHost", set_max_clients_vhost, NULL, RSRC_CONF,
+              "Maximum number of children alive at the same time for this virtual host."),
 AP_GRACEFUL_SHUTDOWN_TIMEOUT_COMMAND,
 { NULL }
 };
@@ -1600,6 +1628,7 @@ static void *itk_create_config(apr_pool_
     itk_server_conf *c = (itk_server_conf *)
         apr_pcalloc(p, sizeof(itk_server_conf));
     c->uid = c->gid = -1;
+    c->max_clients_vhost = -1;
     return c;
 }