From 1f638327b2796071106ff7e3dbd81b9c845e06e9 Mon Sep 17 00:00:00 2001
From: Justin Erenkrantz <jerenkrantz@apache.org>
Date: Sun, 24 Aug 2003 22:43:36 +0000
Subject: [PATCH] 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
---
 server/listen.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 69 insertions(+), 4 deletions(-)

diff --git a/server/listen.c b/server/listen.c
index 10aca871ff..8b13230304 100644
--- 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;
             }
-- 
2.50.1