Ubuntu
isc-dhcp package

dhclient initramfs code writes invalid net-eth0.conf

Bug #1840965 reported by Alkis Georgopoulos
24
This bug affects 4 people
Affects Status Importance Assigned to Milestone
isc-dhcp (Ubuntu)
Fix Released
High
Unassigned
Eoan
Fix Released
High
Unassigned

Bug Description

Since 18.10, Ubuntu switched to using dhclient instead of ipconfig in initramfs configure_networking(). And now a malformed /run/net-enp0s3.conf is generated, with unquoted values like the following, which are a shell syntax error:
IPV4DNS0=1.2.3.1 1.2.3.2 1.2.3.3

This file is sourced by initramfs-tools/init in various places, and produces the following message a lot of times:
/init: /run/net-enp0s3.conf: line 8: 1.2.3.2: not found

I.e. values should be quoted, and 2 DNS entries should go in IPV4DNS0/IPV4DNS1, not multiple unquoted ones in IPV4DNS0.

Here is the erroneous file that dhclient-enter-hooks.d/config produces:
DEVICE=enp0s3
PROTO=dhcp
IPV4PROTO=dhcp
IPV4ADDR=10.161.254.38
IPV4NETMASK=255.255.255.0
IPV4BROADCAST=10.161.254.255
IPV4GATEWAY=10.161.254.1
IPV4DNS0=194.63.237.4 194.63.239.164 194.63.238.4
ROOTSERVER=10.161.254.1
HOSTNAME=
DNSDOMAIN=

Here is the correct one that ipconfig produces:
DEVICE='enp0s3'
PROTO='dhcp'
IPV4ADDR='10.161.254.38'
IPV4BROADCAST='10.161.254.255'
IPV4NETMASK='255.255.255.0'
IPV4GATEWAY='10.161.254.1'
IPV4DNS0='194.63.237.4'
IPV4DNS1='194.63.239.164'
HOSTNAME=''
DNSDOMAIN=''
NISDOMAIN=''
ROOTSERVER='10.161.254.1'
ROOTPATH=''
filename=''
UPTIME='594'
DHCPLEASETIME='25200'
DOMAINSEARCH=''

I.e. please either fix dhclient-enter-hooks.d/config, or revert the ipconfig => dhclient change.

See original description

Related branches

~alkisg/ubuntu/+source/isc-dhcp:lp1840965
Steve Langasek (community): Abstain
Canonical Server: Pending requested
Michael Hudson-Doyle: Pending requested
Diff: 98 lines (+46/-37)
1 file modified
debian/initramfs-tools/lib/etc/dhcp/dhclient-enter-hooks.d/config (+46/-37)
Alkis Georgopoulos (alkisg)
description: updated
Revision history for this message
Alkis Georgopoulos (alkisg) wrote :

Using Ubuntu live CDs, I verified that this did not happen in 18.04 and happens in both 18.10 and 19.04.

Revision history for this message
Alkis Georgopoulos (alkisg) wrote :

The code that generates the invalid /run/net-enp0s3.conf belongs in the Ubuntu isc-dhcp package, and specifically in debian/initramfs-tools/lib/etc/dhcp/dhclient-enter-hooks.d/config.

It got in effect in 18.10 when initramfs-tools in Ubuntu switched to calling dhclient instead of ipconfig.

Additionally, dhclient-script calls `chmod --reference=/etc/resolv.conf $new_resolv_conf`, but busybox chmod doesn't support the --reference parameter.

I.e. dhclient has numerous issues that need to be fixed, otherwise the ipconfig => dhclient change should be reverted...

Thank you.

description: updated
summary: - netplan initramfs code writes invalid net-eth0.conf
+ dhclient initramfs code writes invalid net-eth0.conf
Steve Langasek (vorlon)
Changed in isc-dhcp (Ubuntu):
status: New → Triaged
importance: Undecided → High
Revision history for this message
Alkis Georgopoulos (alkisg) wrote :

I'm attaching a patch for dhclient-enter-hooks.d/config.
I thought to imitate ipconfig and write all values even if they're empty.

For the debian/dhclient-script.* scripts which use chmod/chown parameters that aren't available in busybox, it might be best to just omit them, or use `cp/rm` instead of `chown/mv`.
`cp` is supposed to preserve target attributes etc, so it'll work in a real system, even if `busybox cp` doesn't do that.

no longer affects: netplan
Revision history for this message
Alkis Georgopoulos (alkisg) wrote :

I just noticed that the original script used tabs instead of spaces;
I'm attaching a new .diff that respects that.

tags: added: patch
Revision history for this message
Alkis Georgopoulos (alkisg) wrote :

I uploaded my patch as a merge proposal instead.

Francis Ginther (fginther)
tags: added: id-5d6458d075c1a113cb9c2e57
Revision history for this message
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package isc-dhcp - 4.4.1-2ubuntu5

---------------
isc-dhcp (4.4.1-2ubuntu5) eoan; urgency=medium

  * Apply patch from Alkis Georgopoulos to generate correct
    net{,6}-${iface}.conf files when DHCP supplies multiple DNS servers.
    (LP: #1840965).

 -- Michael Hudson-Doyle <email address hidden> Tue, 03 Sep 2019 10:10:56 +1200

Changed in isc-dhcp (Ubuntu Eoan):
status: Triaged → Fix Released
Revision history for this message
Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in initramfs-tools (Ubuntu):
status: New → Confirmed
Alkis Georgopoulos (alkisg)
no longer affects: initramfs-tools (Ubuntu)
no longer affects: initramfs-tools (Ubuntu Eoan)
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