core: Fix address-in-use startup failure on some platforms caused

by attempting to set up an IPv4 listener which overlaps with an
existing IPv6 listener.

The failure occurred on the second pass of the open-logs hook in
a configuration such as the following:

  Listen 8080
  Listen 0.0.0.0:8081
  Listen [::]:8081

During the first pass, the two port 8081 listen recs were
adjacent and existing logic prevented binding to 0.0.0.0:8081.
On the second pass, they were not adjacent and we then tried
to bind to 0.0.0.0:8081, leading to failure on some platforms
(seen on SLES 9 and Ubuntu 7.10, not seen on many other Unix-ish
platforms).

Leave a note about other unhandled configurations.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@664535 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/CHANGES b/CHANGES
index 8b07da76d5fdf56c39f23458a92f2ae4f3c1c01d..0256f6bb9b1a7ab58849c29ef491c09e330819a2 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -2,6 +2,10 @@
 Changes with Apache 2.3.0
 [ When backported to 2.2.x, remove entry from this file ]
 
+  *) core: Fix address-in-use startup failure on some platforms caused
+     by creating an IPv4 listener which overlaps with an existing IPv6
+     listener.  [Jeff Trawick]
+
   *) mod_proxy_http: Do not forward requests with 'Expect: 100-continue' to
      known HTTP/1.0 servers. Return 'Expectation failed' (417) instead.
      [Ruediger Pluem]

diff --git a/server/listen.c b/server/listen.c
index f2d78f576254f16556248d41d48e205f126bcf00..eff2751075a6227225444f68892d5fee863645af 100644 (file)
--- a/server/listen.c
+++ b/server/listen.c
@@ -376,14 +376,22 @@ static int open_listeners(apr_pool_t *pool)
         }
         else {
 #if APR_HAVE_IPV6
+            ap_listen_rec *cur;
             int v6only_setting;
+            int skip = 0;
 
             /* If we have the unspecified IPv4 address (0.0.0.0) and
              * the unspecified IPv6 address (::) is next, we need to
              * swap the order of these in the list. We always try to
              * bind to IPv6 first, then IPv4, since an IPv6 socket
              * might be able to receive IPv4 packets if V6ONLY is not
-             * enabled, but never the other way around. */
+             * enabled, but never the other way around.
+             * Note: In some configurations, the unspecified IPv6 address
+             * could be even later in the list.  This logic only corrects
+             * the situation where it is next in the list, such as when
+             * apr_sockaddr_info_get() returns an IPv4 and an IPv6 address,
+             * in that order.
+             */
             if (lr->next != NULL
                 && IS_INADDR_ANY(lr->bind_addr)
                 && lr->bind_addr->port == lr->next->bind_addr->port
@@ -401,26 +409,32 @@ static int open_listeners(apr_pool_t *pool)
                 lr = next;
             }
 
-            /* If we are trying to bind to 0.0.0.0 and the previous listener
+            /* If we are trying to bind to 0.0.0.0 and a 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
-                && IS_INADDR_ANY(lr->bind_addr)
-                && lr->bind_addr->port == previous->bind_addr->port
-                && IS_IN6ADDR_ANY(previous->bind_addr)
-                && 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;
-                lr = previous; /* maintain current value of previous after
-                                * post-loop expression is evaluated
-                                */
-                continue;
+            if (IS_INADDR_ANY(lr->bind_addr)) {
+                for (cur = ap_listeners; cur != lr; cur = cur->next) {
+                    if (lr->bind_addr->port == cur->bind_addr->port
+                        && IS_IN6ADDR_ANY(cur->bind_addr)
+                        && apr_socket_opt_get(cur->sd, APR_IPV6_V6ONLY,
+                                              &v6only_setting) == APR_SUCCESS
+                        && v6only_setting == 0) {
+
+                        /* Remove the current listener from the list */
+                        previous->next = lr->next;
+                        lr = previous; /* maintain current value of previous after
+                                        * post-loop expression is evaluated
+                                        */
+                        skip = 1;
+                        break;
+                    }
+                }
+                if (skip) {
+                    continue;
+                }
             }
 #endif
             if (make_sock(pool, lr) == APR_SUCCESS) {