Your message dated Wed, 05 Aug 2026 17:31:09 +0000 with message-id <[email protected]> and subject line Bug#1143544: Removed package(s) from unstable has caused the Debian Bug report #849100, regarding isc-dhcp-client: fails to work properly on dhcp request timeout to be marked as done.
This means that you claim that the problem has been dealt with. If this is not the case it is now your responsibility to reopen the Bug report if necessary, and/or fix the problem forthwith. (NB: If you are a system administrator and have no idea what this message is talking about, this may indicate a serious mail system misconfiguration somewhere. Please contact [email protected] immediately.) -- 849100: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=849100 Debian Bug Tracking System Contact [email protected] with problems
--- Begin Message ---Package: isc-dhcp-client Version: 4.2.4-7ubuntu12.8 Severity: important Tags: upstream Dear isc-dhcp-client Maintainer, There is a small omission in dhclient-script, which may cause a IP address to be lost, with time to get an IP address again typically taking a 1-7 days (but possibly a year or more), unless action is taken to reset it, e.g. by ifdown/ifup on the interface. * Evidence from syslog sh[987]: DHCPDISCOVER on enp2s0 to 255.255.255.255 port 67 interval 9 (xid=0x93c8b31e) dhclient[1001]: No DHCPOFFERS received. sh[987]: No DHCPOFFERS received. sh[987]: Trying recorded lease 172.50.55.101 dhclient[1001]: Trying recorded lease 172.50.55.101 sh[987]: PING 172.50.55.1 (172.50.55.1) 56(84) bytes of data. sh[987]: --- 172.50.55.1 ping statistics --- sh[987]: 1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms root: /etc/dhcp/dhclient-exit-hooks returned non-zero exit status 2 dhclient[1001]: bound: renewal in 477651 seconds. sh[987]: bound: renewal in 477651 seconds. * How it happens basically, "if/then/else" in bash eats return codes: The following script is instructive ---------- #!/bin/sh return_1() { return 1 } return_1 echo "RC is $?" if ! return_1; then echo "then RC is $?" else echo "else RC is $?" fi ---------- RC is 1 then RC is 0 ---------- Let's assume a machine has an active lease for $interface (whether or not the interface is already configured), and does not have a file called "/etc/dhcp /dhcp-exit-hooks". Then, dhclient restarts (e.g., because of a reboot or an apt-get upgrade) tries to renew the still valid lease, but times out because the dhcp server is not responding for whatever reason. What we expect to happen is a retry until an answer is received, with the interface maintaining its address (if it has one) until the original lease expires, or continuing to re- request the address until one is obtained. What actually happens is as follows: 1. dhclient (c side) calls dhclient-script with the TIMEOUT reason and all parameters reflecting the existing lease. 2. dhclient-script TIMEOUT logic tries to ping the 1st router in the lease and gets no reply 3. dhclient-script therefore flushes all IPs from interface using "ip -4 addr flush dev ${interface}", and runs "exit_with_hooks 2" 4. exit_with_hooks initializes exit_status=2, and calls "run_hook /etc/dhcp /dhclient-exit-hooks" 5. run_hook declares a local exit_status variable but does not initialize it, so it retains the value 2 from the calling scope. 6. there is no /etc/dhcp/dhcp-exit-hooks script to run, so exit_status=2 remains. 7. run_hook wrongly logs an error in the (nonexistant) /etc/dhcp/dhclient-exit- hooks using "logger -p" 9. run_hook still returns exit_status=2 10. back in exit_with_hooks, "run_hook" returned a non zero status 2. However, the "if" test kills the $? return code, and as a result, the "then" part sets exit_status=0 11. Let's assume that run_hookdir succeeds. 12. exit_with_hooks now exits with exit_status=0, indicating success 13. dhclient (c side) notes the success, assuming that the interface has been set up (it is not, and even if it were - step 3 above flushes it) and sleeps until the expiration of the original lease. Result: we have an interface with no IP address, no attempt to renew it until the original lease expires. Leases are typically 1-14 days, but some routers give leases for a year. * Temporary solution for an affected system (if you can issue commands to it, e.g. through a console or another interface) ifdown $interface && ifup $interface Worked well for the system in which this was discovered. * Potential Solution 1. In dhclient-script.linux, intiialize the local exit_status variable to 0, as shown in the diff below. ---------- # run given script run_hook() { local script - local exit_status + local exit_status=0 script="$1" if [ -f $script ]; then . $script exit_status=$? fi if [ -n "$exit_status" ] && [ "$exit_status" -ne 0 ]; then logger -p daemon.err "$script returned non-zero exit status $exit_status" fi return $exit_status } -------- 2. In exit_with_hooks, replace both occurences of the construct -------- if ! run_hook .... ; then exit_status=$? fi -------- with something like -------- $rc = run_hook .... if [ $rc ne 0 ] then ; exit_status=$rc; fi -------- * Note: Have not tried it yet in production. My bash/sh/dash is rusty, and I wanted to report while I test my setting. -- System Information: Debian Release: jessie/sid APT prefers trusty-updates APT policy: (500, 'trusty-updates'), (500, 'trusty-security'), (500, 'trusty'), (100, 'trusty-backports') Architecture: amd64 (x86_64) Foreign Architectures: i386 Kernel: Linux 4.4.0-47-generic (SMP w/2 CPU cores) Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Versions of packages isc-dhcp-client depends on: ii debianutils 4.4 ii iproute2 3.12.0-2ubuntu1 ii isc-dhcp-common 4.2.4-7ubuntu12.8 ii libc6 2.19-0ubuntu6.9 isc-dhcp-client recommends no packages. Versions of packages isc-dhcp-client suggests: ii apparmor 2.8.95~2430-0ubuntu5.3 ii avahi-autoipd 0.6.31-4ubuntu1.1 ii resolvconf 1.69ubuntu1.1 -- no debconf information
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--- Begin Message ---Version: 4.4.3-P1-8+rm Dear submitter, as the package isc-dhcp has just been removed from the Debian archive unstable we hereby close the associated bug reports. We are sorry that we couldn't deal with your issue properly. For details on the removal, please see https://bugs.debian.org/1143544 The version of this package that was in Debian prior to this removal can still be found using https://snapshot.debian.org/. Please note that the changes have been done on the master archive and will not propagate to any mirrors until the next dinstall run at the earliest. This message was generated automatically; if you believe that there is a problem with it please contact the archive administrators by mailing [email protected]. Debian distribution maintenance software pp. Thorsten Alteholz (the ftpmaster behind the curtain)
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