Public bug reported:
Binary package hint: dhcp3-client
You open a VPN connection to another network (via PPTP through network
manager or otherwise) - the /etc/resolv.conf file is updated with the
DNS servers of the _remote_ network, however, dhcp3-client overwrites
resolv.conf regularly with _local_ DNS server entries when the DHCP
lease is *renewed*.
The local DNS server entries are often useless in the target network,
thus halt name resolution. The /sbin/dhclient-script bash script is
called with reason=RENEW, which calls the function make_resolv_conf,
overwriting /etc/resolv.conf. The renew time is often as low as 5
minutes for security, and is out of control of the linux user.
One suitable fix is to not update resolv.conf when the DHCP lease is
renewed [1]. I have been using this for some time and get the expected
behaviour.
Version is 3.0.4-12ubuntu3 (Feisty Herd 5), however this has been an
issue for some time in dapper etc. To reproduce, simply lower the DHCP
lease time and connect to any remote network (requiring different DNS
servers).
--- [1]
--- /sbin/dhclient-script.orig 2007-03-08 19:19:56.000000000 +0000
+++ /sbin/dhclient-script 2007-03-08 19:19:46.000000000 +0000
@@ -13,6 +13,10 @@
# The alias handling in here probably still sucks. -mdz
make_resolv_conf() {
+ # don't overwrite resolv.conf at RENEW time, since a VPN/PPTP tunnel may
+ # have updated it with remote DNS servers
+ [ "$reason" = "RENEW" ] && return
+
if [ -n "$new_domain_name" -o -n "$new_domain_name_servers" ]; then
# Find out whether we are going to mount / rw
exec 9>&0 </etc/fstab
** Affects: dhcp3 (Ubuntu)
Importance: Undecided
Status: Unconfirmed
** Description changed:
Binary package hint: dhcp3-client
You open a VPN connection to another network (via PPTP through network
manager or otherwise) - the /etc/resolv.conf file is updated with the
DNS servers of the _remote_ network, however, dhcp3-client overwrites
resolv.conf regularly with _local_ DNS server entries when the DHCP
lease is *renewed*.
The local DNS server entries are often useless in the target network,
thus halt name resolution. The /sbin/dhclient-script bash script is
called with reason=RENEW, which calls the function make_resolv_conf,
overwriting /etc/resolv.conf. The renew time is often as low as 5
minutes for security, and is out of control of the linux user.
One suitable fix is to not update resolv.conf when the DHCP lease is
renewed [1]. I have been using this for some time and get the expected
behaviour.
Version is 3.0.4-12ubuntu3 (Feisty Herd 5), however this has been an
issue for some time in dapper etc. To reproduce, simply lower the DHCP
lease time and connect to any remote network (requiring different DNS
servers).
--- [1]
--- /sbin/dhclient-script.orig 2007-03-08 19:19:56.000000000 +0000
+++ /sbin/dhclient-script 2007-03-08 19:19:46.000000000 +0000
@@ -13,6 +13,10 @@
# The alias handling in here probably still sucks. -mdz
make_resolv_conf() {
+ # don't overwrite resolv.conf at RENEW time, since a VPN/PPTP tunnel may
+ # have updated it with remote DNS servers
- + [ "$reason" = "renew" ] && return
+ + [ "$reason" = "RENEW" ] && return
+
if [ -n "$new_domain_name" -o -n "$new_domain_name_servers" ]; then
# Find out whether we are going to mount / rw
exec 9>&0 </etc/fstab
--
resolv.conf overwritten using VPN/PPP etc...
https://launchpad.net/bugs/90681
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