Package: isc-dhcp-client
Version: 4.4.3-P1-1.1
Followup-For: Bug #932769
Hi,
We experience this issue too, in Bullseye and Bookworm (updated from
Bullseye).
Our environment is similar to that described by Mark (the initial
reporter), i.e., a VMware ESXi cluster with VMs stored on a network
storage. In our case, if the network storage becomes full, VMs get disk
IO errors and mark file systems as read-only.
After that, the DHCP client starts requesting and declining IP addresses
in a rapid manner. Leased addresses stay configured on the VMs' network
interfaces, which leads to DHCP pool exhaustion.
What happens in details:
- The DHCP client requests and receives an IP address.
- It runs the script /sbin/dhclient-script.
- The script configures a network interface.
- Next the script updates the /etc/resolv.conf file.
For this, it calls the wait_for_rw function to check if it can write
to /etc/resolv.conf.<shell PID>.
- If a file system is read only this check doesn't work as expected.
The script fails and exits with a non-zero code once it hits the
following line in wait_for_rw():
while ! { : >> "$file"; } 2>/dev/null;
- So the script exits, but the network interface still has leased IP
address.
- When DHCP client gets a non-zero code from the script, it sends
DHCPDECLINE to a DHCP server.
- The DHCP server abandons the IP address. It might try to reuse it
later by performing a ping check but the misbehaving DHCP client will
respond to it.
The script is executed by Dash (being /bin/sh) and its behavior complies
with POSIX:
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_08_01,
"Redirection error with special built-in utilities" - "shall exit" for
non-interactive shells.
The error doesn't occur if the script executed by Bash. Currently we
test a simple Bash wrapper script as a workaround:
#!/bin/bash
source /sbin/dhclient-script
The problem can be reproduced by issuing "echo 1 >
/sys/block/sda/device/delete" on a test machine to remove the disk (sda
here) from the kernel.
-- System Information:
Debian Release: bookworm/sid
APT prefers testing
APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Kernel: Linux 6.1.0-3-amd64 (SMP w/2 CPU threads; PREEMPT)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
Versions of packages isc-dhcp-client depends on:
ii debianutils 5.7-0.4
ii iproute2 6.1.0-1
ii libc6 2.36-8
Versions of packages isc-dhcp-client recommends:
ii isc-dhcp-common 4.4.3-P1-1.1
Versions of packages isc-dhcp-client suggests:
pn avahi-autoipd <none>
pn isc-dhcp-client-ddns <none>
pn resolvconf <none>
-- no debconf information
