From: Simon McVittie <simon.mcvittie@collabora.co.uk>
Date: Wed, 4 Feb 2015 13:16:18 +0000 (+0000)
Subject: _dbus_listen_tcp_socket: comment on another reason to ignore EADDRINUSE
X-Git-Tag: dbus-1.9.10~18
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1f05dc97445a84f226cf9c055c9d3ed70ed6c7b4;p=thirdparty%2Fdbus.git

_dbus_listen_tcp_socket: comment on another reason to ignore EADDRINUSE

Not being aware of the second reason described here caused bug #87999
in the equivalent code on Windows.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=87999
---

diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
index f6ec8abc5..dcfddd17c 100644
--- a/dbus/dbus-sysdeps-unix.c
+++ b/dbus/dbus-sysdeps-unix.c
@@ -1463,9 +1463,18 @@ _dbus_listen_tcp_socket (const char     *host,
           _dbus_close(fd, NULL);
           if (saved_errno == EADDRINUSE)
             {
-              /* Depending on kernel policy, it may or may not
-                 be neccessary to bind to both IPv4 & 6 addresses
-                 so ignore EADDRINUSE here */
+              /* Depending on kernel policy, binding to an IPv6 address
+                 might implicitly bind to a corresponding IPv4
+                 address or vice versa, resulting in EADDRINUSE for the
+                 other one (e.g. bindv6only=0 on Linux).
+
+                 Also, after we "goto redo_lookup_with_port" after binding
+                 a port on one of the possible addresses, we will
+                 try to bind that same port on every address, including the
+                 same address again for a second time; that one will
+                 also fail with EADDRINUSE.
+
+                 For both those reasons, ignore EADDRINUSE here */
               tmp = tmp->ai_next;
               continue;
             }