Package: wide-dhcpv6-server
Version: 20080615-1
Severity: grave
Justification: breaks upgrades
On startup, dhcp6s does not close any stray file descriptors it may have
inherited. When called from wide-dhcpv6-server.postinst, this includes
fd 3, which is a pipe to debconf. The result of this is a hang on
upgrade, with a process tree looking like this:
1511 pts/8 Ss+ 0:30 \_ /usr/bin/dpkg
--admindir=/var/lib/dpkg --status-fd 20 --configure libiw29 wireless-tools
imagemagick libmagick++10 libplot2c2 libpstoedit0c2a ldap-utils li
22001 pts/8 S+ 0:04 \_ /usr/bin/perl -w
/usr/share/debconf/frontend /var/lib/dpkg/info/wide-dhcpv6-server.postinst
configure 20061016-2
22009 pts/8 Z+ 0:00 \_
[wide-dhcpv6-ser] <defunct>
22031 ? Ss 0:00 /usr/sbin/dhcp6s -k /dev/null -P
/var/run/dhcp6s.eth1.pid eth1
I can tell that the pipe to debconf is still open:
$ sudo lsof -p 22001 | grep 'pipe$'
frontend 22001 root 7w FIFO 0,6 29433263 pipe
frontend 22001 root 8r FIFO 0,6 29433264 pipe
$ sudo lsof -p 22031 | grep 'pipe$'
dhcp6s 22031 root 3w FIFO 0,6 29433264 pipe
wide-dhcpv6-server's postinst attempts to work around this problem by
calling db_stop to let debconf know that it's finished. However, it only
calls it if /etc/default/wide-dhcpv6-server does not exist, whereas it
sources the confmodule unconditionally (usually a good idea anyway since
sourcing the confmodule has weird semantics, re-execing the sourcing
script), so unless I'm much mistaken it seems that it will always fail
to upgrade.
Calling db_stop is at best an ugly workaround anyway. Rather than
calling db_stop, I would recommend that you make dhcp6s close all its
inherited file descriptors on startup. The usual idiom for this is
something like this (and no, as far as I know there is nothing neater):
int fd;
for (fd = 3; fd < 1024; ++fd)
close(fd);
The daemon(0, 0) call that dhcp6s already makes will take care of file
descriptors 0, 1, and 2.
For anyone affected by this, a workaround to allow the upgrade to
proceed without inconvenient dpkg errors is to run
'/etc/init.d/wide-dhcpv6-server restart' from a separate shell.
Thanks,
--
Colin Watson [[email protected]]
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