mac dns: compare servers before restoring backup

In case anything changed the global DNS server addresses, while the
tunnel was connected, do not restore the backup of the global DNS
configuration we made when connecting. Doing so would likely change
DNS to something unexpected. Instead just clear the backup and leave
a message in the log.

Change-Id: I1aabd62e60dd18408a57baccbb0f4ebd6d2f8d67
Signed-off-by: Heiko Hund <heiko@ist.eigentlich.net>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20250711152309.286177-1-frank@lichtenheld.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg32110.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

diff --git a/distro/dns-scripts/macos-dns-updown.sh b/distro/dns-scripts/macos-dns-updown.sh
index 56f10095c998da282ee94247602dc08932108df6..73bbee9596562e42aeb44c72c54af523a912d50f 100644 (file)
--- a/distro/dns-scripts/macos-dns-updown.sh
+++ b/distro/dns-scripts/macos-dns-updown.sh
@@ -111,6 +111,10 @@ function get_search_domains {
     property_value State:/Network/Global/DNS SearchDomains
 }
 
+function get_server_addresses {
+    property_value "$(primary_dns_key)" ServerAddresses
+}
+
 function set_search_domains {
     [ -n "$1" ] || return
     local dns_key=$(primary_dns_key)
@@ -239,11 +243,10 @@ function set_dns {
 
 function unset_dns {
     local n="$(find_compat_profile)"
-    local addresses="$(addresses_string $n)"
-    local search_domains="$(search_domains_string $n)"
     local match_domains="$(match_domains_string $n)"
 
     if [ -n "$match_domains" ]; then
+        local search_domains="$(search_domains_string $n)"
         echo "remove ${itf_dns_key}" | /usr/sbin/scutil
         unset_search_domains "$search_domains"
     else
@@ -252,8 +255,15 @@ function unset_dns {
         [[ "${dns_backup_key}" =~ ${dev}/ ]] || return
 
         local cmds=""
-        cmds+="get ${dns_backup_key}\n"
-        cmds+="set $(primary_dns_key)\n"
+        local servers="$(get_server_addresses)"
+        local addresses="$(addresses_string $n)"
+        # Only restore backup if the server addresses match
+        if [ "${servers}" = "${addresses}" ]; then
+            cmds+="get ${dns_backup_key}\n"
+            cmds+="set $(primary_dns_key)\n"
+        else
+            echo "not restoring global DNS configuration, server addresses have changed"
+        fi
         cmds+="remove ${dns_backup_key}\n"
         echo -e "${cmds}" | /usr/sbin/scutil
     fi