You have been subscribed to a public bug: Binary package hint: ifupdown
release: Ubuntu 10.04 LTS (but probably all releases back to Hardy and forward to Maverick) package: ifupdown: Installed: 0.6.8ubuntu29 Since upgrading my systems to lucid and cleaning up the configurations, I've noticed strange behaviour where client tcp or udp sessions to local tcp/ip servers have timed out even though the servers were running and netstat showed they were listening on all interfaces. Wireshark traces showed that successful connections went to 127.0.0.1, while any connection attempt to 127.0.1.1 would fail. The systems are fully controlled by NetworkManager <offtopic>a long and painful story!</offtopic> and so /etc/network/interfaces contains only two lines: auto lo iface lo inet loopback This "minimal configuration" is not only highly recommended to avoid wierd behaviour with NetworkManager, but also to avoid problems with upstart (e.g. https://bugs.launchpad.net/ubuntu/+source/ifupdown/+bug/497299). All the other network interfaces are managed by NM. "In the old days", a typical /etc/hosts file would define all the local hostnames as follows: 127.0.0.1 myhostname.localdomain myhostname localhost.localdomain localhost For several releases (back as far as Hardy), ubuntu installations have been creating a more sophisticated version of the hosts file (presumably because of http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=316099), e.g. 127.0.0.1 localhost 127.0.1.1 myhostname.mydomain myhostname This modern variant allows the system to always resolve its own hostname and canonical name, even when there is no external network. It appears to work really well... e.g. "ping hostname" and "ping localhost" both succeed. "hostname" and "hostname -f" return the expected values. (note: I don't fully understand why ping hostname actually works - perhaps because the class A 127.0.0.0 subnet has been defined for ever as a loopback subnet?). The problem comes when a local client tries to connect to a local server... a well-behaved server will listen on "all available network interfaces", e.g. brian@myhostname:~$ netstat -ln | grep 53 tcp 0 0 10.1.252.115:53 0.0.0.0:* LISTEN tcp 0 0 192.168.252.115:53 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN udp 0 0 10.1.252.115:53 0.0.0.0:* udp 0 0 192.168.252.115:53 0.0.0.0:* udp 0 0 127.0.0.1:53 0.0.0.0:* ... so, when a client tries to connect to the local server (in my not very realistic example you would have to edit /etc/resolv.conf to point to myhostname instead of the default localhost), the nslookup connection would never be received by the local bind server and so will eventually time out. If we are to keep the "new style" hosts file structure (and I think we should), then we MUST ensure that local servers are able to access all available interfaces, including BOTH of the loopback addresses mentioned in the hosts file, so we need to define an additional interface for the myhostname loopback address. This can be easily demonstrated by defining a second (virtual) address for the lo interface: sudo ifconfig lo:0 127.0.1.1 netmask 255.0.0.0 Stop the server and it will discover the extra interface when it is restarted: brian@myhostname:~$ netstat -ln | grep 53 tcp 0 0 10.1.252.115:53 0.0.0.0:* LISTEN tcp 0 0 192.168.252.115:53 0.0.0.0:* LISTEN tcp 0 0 127.0.1.1:53 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN udp 0 0 10.1.252.115:53 0.0.0.0:* udp 0 0 192.168.252.115:53 0.0.0.0:* udp 0 0 127.0.1.1:53 0.0.0.0:* udp 0 0 127.0.0.1:53 0.0.0.0:* Of course, this circumvention will only last until the next reboot. The solution can be made permanent by updating the /etc/networking/interfaces file to automatically bring up both loopback interfaces early in the boot process: # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # automatically bring up both these interfaces at boot (ifup -a == all) auto lo lo:0 # The standard loopback network interface iface lo inet loopback # another loopback interface for that pesky dual loopback hosts file iface lo:0 inet static address 127.0.1.1 netmask 255.0.0.0 I do not know if there is a more elegant solution to the same problem (but remember that some of the server processes are started very early, hence the upstart bug reference above). If acceptable, this bug should be pushed upstream to encompass the other distros that use the same multiple loopback interface /etc/hosts file organisation. ** Affects: bind9 (Ubuntu) Importance: Undecided Status: Invalid ** Affects: ifupdown (Debian) Importance: Unknown Status: New ** Tags: patch udd-find -- network servers do not listen on 127.0.1.1 https://bugs.launchpad.net/bugs/604283 You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to bind9 in Ubuntu. -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs