Fixup IPv6 Listen statements on Linux by attempting to bind in the order

that getaddrinfo() returned to us and skipping binding to IPv4 addresses
if the previous bind was to an IPv6 of the same address and port.

Justin made some style changes, added a (struct in6_addr*) to make it compile
on *BSD as well as an attempt to make the addition of the listener to the list
a little more efficient.

Submitted by:	Colm MacCarthaigh <colm@stdlib.net>
Reviewed by:	Justin Erenkrantz

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@101083 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/server/listen.c b/server/listen.c
index 10aca871fff6bfc8f09b0d0c06f697fd209097f9..8b13230304a9ece4ff314675237a728564a5b9d7 100644 (file)
--- a/server/listen.c
+++ b/server/listen.c
@@ -231,7 +231,7 @@ static apr_status_t close_listeners_on_exec(void *v)
 
 static const char *alloc_listener(process_rec *process, char *addr, apr_port_t port)
 {
-    ap_listen_rec **walk;
+    ap_listen_rec **walk, *last;
     apr_status_t status;
     apr_sockaddr_t *sa;
     int found_listener = 0;
@@ -276,12 +276,19 @@ static const char *alloc_listener(process_rec *process, char *addr, apr_port_t p
         return "Listen setup failed";
     }
 
+    /* Initialize to our last configured ap_listener. */
+    last = ap_listeners;
+    while (last && last->next) {
+        last = last->next;
+    }
+
     while (sa) {
         ap_listen_rec *new;
 
         /* this has to survive restarts */
         new = apr_palloc(process->pool, sizeof(ap_listen_rec));
         new->active = 0;
+        new->next = 0;
         new->bind_addr = sa;
 
         /* Go to the next sockaddr. */
@@ -306,8 +313,13 @@ static const char *alloc_listener(process_rec *process, char *addr, apr_port_t p
             return "Listen setup failed";
         }
 
-        new->next = ap_listeners;
-        ap_listeners = new;
+        /* We need to preserve the order returned by getaddrinfo() */
+        if (last == NULL) {
+            ap_listeners = last = new;
+        } else {
+            last->next = new;
+            last = new;
+        }
     }
 
     return NULL;
@@ -317,6 +329,7 @@ static int ap_listen_open(apr_pool_t *pool, apr_port_t port)
 {
     ap_listen_rec *lr;
     ap_listen_rec *next;
+    ap_listen_rec *previous;
     int num_open;
     const char *userdata_key = "ap_listen_open";
     void *data;
@@ -326,16 +339,68 @@ static int ap_listen_open(apr_pool_t *pool, apr_port_t port)
      * config file.
      */
     num_open = 0;
-    for (lr = ap_listeners; lr; lr = lr->next) {
+    previous = NULL;
+    for (lr = ap_listeners; lr; previous = lr, lr = lr->next) {
         if (lr->active) {
             ++num_open;
         }
         else {
+#if APR_HAVE_IPV6
+            int v6only_setting;
+            /* If we are trying to bind to 0.0.0.0 and the previous listener
+             * was :: on the same port and in turn that socket does not have
+             * the IPV6_V6ONLY flag set; we must skip the current attempt to
+             * listen (which would generate an error). IPv4 will be handled
+             * on the established IPv6 socket.
+             */
+            if (previous != NULL &&
+                lr->bind_addr->family == APR_INET &&
+                *((in_addr_t *)lr->bind_addr->ipaddr_ptr) == INADDR_ANY &&
+                lr->bind_addr->port == previous->bind_addr->port &&
+                previous->bind_addr->family == APR_INET6 &&
+                IN6_IS_ADDR_UNSPECIFIED(
+                        (struct in6_addr*)(previous->bind_addr->ipaddr_ptr)) &&
+                apr_socket_opt_get(previous->sd, APR_IPV6_V6ONLY,
+                                   &v6only_setting) == APR_SUCCESS &&
+                v6only_setting == 0) {
+
+                /* Remove the current listener from the list */
+                previous->next = lr->next;
+                continue;
+            }
+#endif
             if (make_sock(pool, lr) == APR_SUCCESS) {
                 ++num_open;
                 lr->active = 1;
             }
             else {
+#if APR_HAVE_IPV6
+                /* If we tried to bind to ::, and the next listener is
+                 * on 0.0.0.0 with the same port, don't give a fatal
+                 * error. The user will still get a warning from make_sock
+                 * though.
+                 */
+                if (lr->next != NULL && lr->bind_addr->family == APR_INET6 &&
+                    IN6_IS_ADDR_UNSPECIFIED(
+                        (struct in6_addr*)(previous->bind_addr->ipaddr_ptr)) &&
+                    lr->bind_addr->port == lr->next->bind_addr->port &&
+                    *((in_addr_t *)lr->next->bind_addr->ipaddr_ptr)
+                    == INADDR_ANY) {
+
+                    /* Remove the current listener from the list */
+                    if (previous) {
+                        previous->next = lr->next;
+                    }
+                    else {
+                        ap_listeners = lr->next;
+                    }
+
+                    /* So that previous becomes NULL in the next iteration */
+                    lr = NULL;
+
+                    continue;
+                }
+#endif
                 /* fatal error */
                 return -1;
             }