From 7a8faaf1771c194af9e36a4ae8ceb3c53c9c8be8 Mon Sep 17 00:00:00 2001
From: Simon McVittie <smcv@collabora.com>
Date: Thu, 8 Mar 2018 13:36:17 +0000
Subject: [PATCH] sysdeps-unix: Set more specific IP-related errors when
 listening

When we have resolved a hostname/port pair to a list of IPv4 or IPv6
addresses, if we are unable to listen on a a specific one of those
addresses, we should report which one.

When IPv6 is disabled for the loopback interface, this changes the
diagnostic from:

Failed to bind socket "localhost:1234": Cannot assign requested address

to the more informative

Failed to bind socket "::1" port 1234: Cannot assign requested address

Signed-off-by: Simon McVittie <smcv@collabora.com>

https://bugs.freedesktop.org/show_bug.cgi?id=61922
---
 dbus/dbus-sysdeps-unix.c | 13 +++++++------
 dbus/dbus-sysdeps.c      | 38 ++++++++++++++++++++++++++++++++++++++
 dbus/dbus-sysdeps.h      |  5 +++++
 3 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
index d7f16fc7..0ab034ff 100644
--- a/dbus/dbus-sysdeps-unix.c
+++ b/dbus/dbus-sysdeps-unix.c
@@ -1562,9 +1562,10 @@ _dbus_listen_tcp_socket (const char     *host,
               tmp = tmp->ai_next;
               continue;
             }
-          dbus_set_error (error, _dbus_error_from_errno (saved_errno),
-                          "Failed to bind socket \"%s:%s\": %s",
-                          host ? host : "*", port, _dbus_strerror (saved_errno));
+
+          _dbus_set_error_with_inet_sockaddr (error, tmp->ai_addr, tmp->ai_addrlen,
+                                              "Failed to bind socket",
+                                              saved_errno);
           goto failed;
         }
 
@@ -1572,9 +1573,9 @@ _dbus_listen_tcp_socket (const char     *host,
         {
           saved_errno = errno;
           _dbus_close (fd, NULL);
-          dbus_set_error (error, _dbus_error_from_errno (saved_errno),
-                          "Failed to listen on socket \"%s:%s\": %s",
-                          host ? host : "*", port, _dbus_strerror (saved_errno));
+          _dbus_set_error_with_inet_sockaddr (error, tmp->ai_addr, tmp->ai_addrlen,
+                                              "Failed to listen on socket",
+                                              saved_errno);
           goto failed;
         }
 
diff --git a/dbus/dbus-sysdeps.c b/dbus/dbus-sysdeps.c
index f15e556f..43fa109f 100644
--- a/dbus/dbus-sysdeps.c
+++ b/dbus/dbus-sysdeps.c
@@ -870,6 +870,44 @@ _dbus_inet_sockaddr_to_string (const void *sockaddr_pointer,
     }
 }
 
+/*
+ * Format an error appropriate for saved_errno for the IPv4 or IPv6
+ * address pointed to by sockaddr_pointer of length sockaddr_len.
+ *
+ * @param error The error to set
+ * @param sockaddr_pointer A struct sockaddr_in or struct sockaddr_in6
+ * @param len The length of the struct pointed to by sockaddr_pointer
+ * @param description A prefix like "Failed to listen on socket"
+ * @param saved_errno The OS-level error number to use
+ */
+void
+_dbus_set_error_with_inet_sockaddr (DBusError *error,
+                                    const void *sockaddr_pointer,
+                                    size_t len,
+                                    const char *description,
+                                    int saved_errno)
+{
+  char string[INET6_ADDRSTRLEN];
+  dbus_uint16_t port;
+  const struct sockaddr *addr = sockaddr_pointer;
+
+  if (_dbus_inet_sockaddr_to_string (sockaddr_pointer, len,
+                                     string, sizeof (string), NULL, &port,
+                                     NULL))
+    {
+      dbus_set_error (error, _dbus_error_from_errno (saved_errno),
+                      "%s \"%s\" port %u: %s",
+                      description, string, port, _dbus_strerror (saved_errno));
+    }
+  else
+    {
+      dbus_set_error (error, _dbus_error_from_errno (saved_errno),
+                      "%s <address of unknown family %d>: %s",
+                      description, addr->sa_family,
+                      _dbus_strerror (saved_errno));
+    }
+}
+
 /** @} end of sysdeps */
 
 /* tests in dbus-sysdeps-util.c */
diff --git a/dbus/dbus-sysdeps.h b/dbus/dbus-sysdeps.h
index 4005a44f..376f6802 100644
--- a/dbus/dbus-sysdeps.h
+++ b/dbus/dbus-sysdeps.h
@@ -701,6 +701,11 @@ dbus_bool_t _dbus_inet_sockaddr_to_string (const void *sockaddr_pointer,
                                            const char **family_name,
                                            dbus_uint16_t *port,
                                            DBusError *error);
+void _dbus_set_error_with_inet_sockaddr (DBusError *error,
+                                         const void *sockaddr_pointer,
+                                         size_t len,
+                                         const char *description,
+                                         int saved_errno);
 
 /** @} */
 
-- 
2.12.3