Devuan bug report logs - #421
isc-dhcp-client: no ipv6 prefix set automatically

Package: isc-dhcp-client; Maintainer for isc-dhcp-client is (unknown); Source for isc-dhcp-client is src:isc-dhcp.

Reported by: Adrian Zaugg <>

Date: Sat, 4 Apr 2020 21:18:02 UTC

Severity: normal

Tags: debian

Found in version 4.3.5-3+deb9u1

Done: Mark Hindley <>

Full log

🔗 View this message in rfc822 format

MIME-Version: 1.0
X-Mailer: MIME-tools 5.509 (Entity 5.509)
From: "Devuan bug Tracking System" <>
To: Mark Hindley <>
Subject: bug#421: marked as done (isc-dhcp-client: no ipv6 prefix set
Message-ID: <>
References: <>
X-Devuan-PR-Message: closed 421
X-Devuan-PR-Package: isc-dhcp-client
X-Devuan-PR-Keywords: debian
Date: Mon, 06 Apr 2020 09:18:01 +0000
Content-Type: multipart/mixed; boundary="----------=_1586164681-6787-0"
[Message part 1 (text/plain, inline)]
Your message dated Mon, 6 Apr 2020 09:59:40 +0100
with message-id <>
and subject line Re: reported to Debian under #955825
has caused the Devuan bug report #421,
regarding isc-dhcp-client: no ipv6 prefix set automatically
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

Devuan Bug Tracking System
Contact with problems
[Message part 2 (message/rfc822, inline)]
From: Adrian Zaugg <>
To: Devuan Bug Tracking System <>
Subject: isc-dhcp-client: no ipv6 prefix set automatically
Date: Sat, 04 Apr 2020 23:00:28 +0200
Package: isc-dhcp-client
Version: 4.3.5-3+deb9u1
Severity: important

Requesting an address over dhcp6 does not set the ipv6 prefix length. The address received seems always get 
a /128 prefix set, even if the dhcp6 server sends another one. 

I expect dhclient to set the prefix lenght, if the dhcp6 server sends one.

The code in /sbin/dhclient-script under "### DHCPv6 Handlers" is the same in ascii and Debian/unstable (4.4.1-2.1+b2). 

It has a mark "TODO: handle prefix change: ?based on ${old_ip6_prefix} and ${new_ip6_prefix}?"... In the code that 
does set the ipv6 address using iproute2 there is no prefix mentioned. See line 385 and the following:

    385     BOUND6|RENEW6|REBIND6)
    386         if [ "${new_ip6_address}" ]; then
    387             # set leased IP
    388             ip -6 addr add ${new_ip6_address} \
    389                 dev ${interface} scope global
    390         fi

This part has two problems: It should also be called upon reason REBOOT6 (see dhclient-script(8)) and it 
should set the prefix if one was given. I suggest to change this to:

    386         if [ "${new_ip6_address}" ]; then
    388             # check wether a prefix was passed and add it to the address
    389             if [ -n "$new_ip6_prefixlen" ]; then
    390                 new_ip6_address_and_prefix="${new_ip6_address}/${new_ip6_prefixlen}"
    391             else
    392                 new_ip6_address_and_prefix="${new_ip6_address}"
    393             fi
    395             # set leased IP
    396             ip -6 addr add ${new_ip6_address_and_prefix} \
    397                 dev ${interface} scope global

According to my tests this resolves the problem. Please review.

Regards, Adrian.

-- System Information:
Distributor ID:	Devuan
Description:	Devuan GNU/Linux 2.1 (ascii)
Release:	2.1
Codename:	ascii

Architecture: x86_64

Kernel: Linux 4.9.0-12-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)

Versions of packages isc-dhcp-client depends on:
ii  debianutils
ii  iproute2          4.9.0-1+deb9u1
ii  libc6             2.24-11+deb9u4
ii  libdns-export162  1:9.10.3.dfsg.P4-12.3+deb9u5
ii  libisc-export160  1:9.10.3.dfsg.P4-12.3+deb9u5

Versions of packages isc-dhcp-client recommends:
ii  isc-dhcp-common  4.3.5-3+deb9u1

Versions of packages isc-dhcp-client suggests:
pn  avahi-autoipd         <none>
pn  isc-dhcp-client-ddns  <none>
ii  resolvconf            1.79

-- Configuration Files:
/etc/dhcp/debug changed [not included]

-- no debconf information
[Message part 3 (message/rfc822, inline)]
From: Mark Hindley <>
Subject: Re: reported to Debian under #955825
Date: Mon, 6 Apr 2020 09:59:40 +0100
On Sun, 5 Apr 2020 13:58:54 +0200 Adrian Zaugg <> wrote:
> Could you please close this bug, I reported it to Debian directly. You
> can find it under #955825 [1]. Thank you.
> [1]


Closing here.


Send a report that this bug log contains spam.

Devuan BTS -- Powered by Debian bug tracking system
Copyright (C) 1999 Darren O. Benham,
1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson,
2005-2017 Don Armstrong, and many other contributors.

Devuan Bugs Owner <>.
Last modified: Wed Jan 19 23:25:14 2022;