Your message dated Mon, 14 Apr 2025 18:17:20 +1000
with message-id
<CALy8Cw5igPHeSCN=8jkkhpowkyl8xnidvd2xa6zu74olg25...@mail.gmail.com>
and subject line Re: Bug#923746: dnsmasq: ra advertises wrong ipv6 link MTU
has caused the Debian Bug report #923746,
regarding dnsmasq: ra advertises wrong ipv6 link MTU
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
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misconfiguration somewhere. Please contact [email protected]
immediately.)
--
923746: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=923746
Debian Bug Tracking System
Contact [email protected] with problems
--- Begin Message ---
Package: dnsmasq
Version: 2.76-5+deb9u1
Severity: normal
Tags: ipv6
Dear Maintainer,
* What led up to the situation?
My browsing from my Windows box suddenly went weird
* What exactly did you do (or not do) that was effective (or
ineffective)?
I checked the MTU sizes the Windows box was using: 1500 for both ipv4
and ipv6. The ipv6 one should be 1280 (I'm using an HE tunnel). So I
fixed it in windows using
netsh interface ipv6 set subinterface "Local Area Connection" mtu=1280
store=persistent
* What was the outcome of this action?
Minutes later it was back to 1500 so I looked at my dnsmasq.conf
(attached) - all seems tickety boo so I checked
/proc/sys/net/ipv6/conf/he-ipv6/mtu and that is correctly set to 1280,
so for some reason dnsmasq is not picking that up and advertising it for
my he-ipv6 interface. I checked with wireshark and the ra packets are
being sent out with MTU 1500 not 1280.
* What outcome did you expect instead?
I expected Windows to receive the correct MTU size of 1280 as set in
/proc/sys/net/ipv6/conf/he-ipv6/mtu
Many thanks for a great piece of software,
CC
-- System Information:
Debian Release: 9.5
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 4.9.0-8-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8),
LANGUAGE=en_GB:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
Versions of packages dnsmasq depends on:
ii dnsmasq-base 2.76-5+deb9u1
ii init-system-helpers 1.48
ii netbase 5.4
dnsmasq recommends no packages.
Versions of packages dnsmasq suggests:
pn resolvconf <none>
-- Configuration Files:
/etc/dnsmasq.conf changed:
domain-needed
bogus-priv
no-resolv
no-poll
server=2606:4700:4700::1111
server=2606:4700:4700::1001
server=1.1.1.1
server=1.0.0.1
local=/sadnet/
interface=int0
bind-interfaces
expand-hosts
domain=sadnet
dhcp-range=192.168.4.1,192.168.4.127,255.255.255.0,192.168.4.255,24h
read-ethers
dhcp-option=42,0.0.0.0
dhcp-option=19,0 # option ip-forwarding off
dhcp-option=44,0.0.0.0 # set netbios-over-TCP/IP nameserver(s) aka
WINS server(s)
dhcp-option=45,0.0.0.0 # netbios datagram distribution server
dhcp-option=46,8 # netbios node type
dhcp-option=47 # empty netbios scope.
dhcp-option=vendor:PXEClient,1,192.168.4.30
dhcp-option=vendor:MSFT,2,1i
dhcp-option=vendor:Etherboot,60,"Etherboot"
dhcp-boot=pxelinux.0
enable-tftp
tftp-root=/srv/Linux/images/Debian-netboot
dhcp-authoritative
bogus-nxdomain=64.94.110.11
bogus-nxdomain=81.200.64.50
mx-target=mail.sadnet
localmx
log-dhcp
bootp-dynamic
cname=ntinstall,fatboy
cname=uranos,fatboy
enable-ra
dhcp-range=tag:int0,::1,constructor:int0,ra-names,24h
dhcp-option=option6:dns-server,2001:470:1f1d:1d3::1
-- no debconf information
--- End Message ---
--- Begin Message ---
> The problem is that sysctl is not setting
> /proc/sys/net/ipv6/conf/int0/mtu to 1280, despite the fact that this is
> set explicitly in /etc/sysctl.conf
Apologies for the huge delay.
That would be a timing issue, sysctl is run and then the interface comes
up. That should be much less of an issue now. In any case you're probably
using systemd-sysctl now anyway.
- Craig
--- End Message ---
