Re: ipv6 maybe has arrived.
On Fri 10 Feb 2023 at 06:40:42 (+0100), tomas@tuxteam.de wrote:
> On Thu, Feb 09, 2023 at 03:32:46PM -0500, gene heskett wrote:
> > On 2/9/23 07:53, tomas@tuxteam.de wrote:
> > > On Thu, Feb 09, 2023 at 07:32:18AM -0500, Greg Wooledge wrote:
> > >
> > > [...]
> > >
> > > > (I have no idea what mdns4_minimal is, but Debian put it there, and it
> > > > hasn't caused a problem yet so I left it alone.)
> > >
> > > This is a zeroconf thingy. My box hasn't that, because I banned Avahi
> > > and its ilk long ago.
> > >
> > > Just out of curiosity: does your box have one of those funny link-local
> > > IPv4 169.254.xxx.yyy addresses?
> > >
> > rant on:
> >
> > Same here Tomas, anytime I see one of those addresses, avahi is another
> > NSFW word, and it goes out by way of rm [...]
>
> Dunno. Debian here. I just don't install it. Works :-)
My systems all have avahi-daemon and avahi-utils installed, and the
laptops have avahi-autoipd as well, but I never see 169.254.…
addresses in the output of ip a¹ or in the logs², or in the output
of avahi-browse -art³ (which shows a driverless printer, my
apt-cacher-ng, and a TV that's switched on by chance (AirPlay/spotify)).
I've read that machines give themselves a 169.254.… address when they
boot up and can't find a DHCP server. But I never see those addresses
when I boot up a machine, disconnected or connected. All I see is
localhost on 127.0.0.1, the machine's hostname on 127.0.1.1, and
if connected, the 192.168.1.NN address handed out by DHCP.
So it's difficult to figure out why some are plagued by these
addresses, made worse when one gets used for the default route, eg
https://lists.debian.org/debian-user/2019/07/msg00208.html
So many of the "solutions" proferred seemed to involve "nuking" avahi.
Disclosure: The router's DHCP server on my LAN assigns the IP
addresses by means of devices' MACs. As there's no DNS server,
hosts find each other using /etc/hosts, which I redistribute
from a master copy whenever I add, say, a new device to the DHCP
list on the router. It's modified from the standard copy that
Debian installs:
127.0.0.1 localhost
192.168.1.1 router.corp router
192.168.1.2 cascade.corp cascade⁴
192.168.1.14⁵ ahost.corp ahost
127.0.1.1 thishost.corp thishost # 192.168.1.15⁶
192.168.1.17 bhost.corp ahost
192.168.1.12 printer.corp printer
192.168.1.107 sometv.corp sometv
192.168.1.184 somephone.corp somephone
[ … ]
# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
127.0.0.1 [ 10k+ lines of junk domains⁶ ]
¹ eg:
$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether a4:12:34:56:78:90 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.14/24 brd 192.168.1.255 scope global dynamic enp3s0
valid_lft 80638sec preferred_lft 80638sec
inet6 fe80::a612:34ff:fe56:7890/64 scope link
valid_lft forever preferred_lft forever
$ ip r
default via 192.168.1.1 dev enp3s0
192.168.1.0/24 dev enp3s0 proto kernel scope link src 192.168.1.14
$
² eg:
$ grep -i -e avahi -e mdns -e dhclient /var/log/daemon.log | sed -e 's/^Feb 11 08:18://;'
35 ahost dhclient[550]: Internet Systems Consortium DHCP Client 4.4.1
35 ahost dhclient[550]: Copyright 2004-2018 Internet Systems Consortium.
35 ahost dhclient[550]: All rights reserved.
35 ahost dhclient[550]: For info, please visit https://www.isc.org/software/dhcp/
35 ahost dhclient[550]:
35 ahost dhclient[550]: Listening on LPF/enp3s0/a4:12:34:56:78:90
35 ahost dhclient[550]: Sending on LPF/enp3s0/a4:12:34:56:78:90
35 ahost dhclient[550]: Sending on Socket/fallback
35 ahost dhclient[550]: DHCPDISCOVER on enp3s0 to 255.255.255.255 port 67 interval 3
35 ahost dhclient[550]: DHCPDISCOVER on enp3s0 to 255.255.255.255 port 67 interval 8
35 ahost dhclient[550]: DHCPOFFER of 192.168.1.14 from 192.168.1.1
35 ahost dhclient[550]: DHCPREQUEST for 192.168.1.14 on enp3s0 to 255.255.255.255 port 67
35 ahost dhclient[550]: DHCPACK of 192.168.1.14 from 192.168.1.1
35 ahost dhclient[550]: bound to 192.168.1.14 -- renewal in 38632 seconds.
35 ahost systemd[1]: Listening on Avahi mDNS/DNS-SD Stack Activation Socket.
35 ahost systemd[1]: Starting Avahi mDNS/DNS-SD Stack...
43 ahost avahi-daemon[601]: Found user 'avahi' (UID 108) and group 'avahi' (GID 117).
43 ahost avahi-daemon[601]: Successfully dropped root privileges.
43 ahost avahi-daemon[601]: avahi-daemon 0.8 starting up.
43 ahost avahi-daemon[601]: Successfully called chroot().
43 ahost avahi-daemon[601]: Successfully dropped remaining capabilities.
43 ahost avahi-daemon[601]: Loading service file /services/apt-cacher-ng.service.
43 ahost avahi-daemon[601]: Joining mDNS multicast group on interface enp3s0.IPv6 with address fe80::a612:34ff:fe56:7890.
43 ahost avahi-daemon[601]: New relevant interface enp3s0.IPv6 for mDNS.
43 ahost avahi-daemon[601]: Joining mDNS multicast group on interface enp3s0.IPv4 with address 192.168.1.14.
43 ahost avahi-daemon[601]: New relevant interface enp3s0.IPv4 for mDNS.
43 ahost avahi-daemon[601]: Joining mDNS multicast group on interface lo.IPv6 with address ::1.
43 ahost avahi-daemon[601]: New relevant interface lo.IPv6 for mDNS.
43 ahost avahi-daemon[601]: Joining mDNS multicast group on interface lo.IPv4 with address 127.0.0.1.
43 ahost avahi-daemon[601]: New relevant interface lo.IPv4 for mDNS.
43 ahost avahi-daemon[601]: Network interface enumeration completed.
43 ahost avahi-daemon[601]: Registering new address record for fe80::a612:34ff:fe56:7890 on enp3s0.*.
43 ahost avahi-daemon[601]: Registering new address record for 192.168.1.14 on enp3s0.IPv4.
43 ahost avahi-daemon[601]: Registering new address record for ::1 on lo.*.
43 ahost systemd[1]: Started Avahi mDNS/DNS-SD Stack.
43 ahost avahi-daemon[601]: Registering new address record for 127.0.0.1 on lo.IPv4.
43 ahost avahi-daemon[601]: Server startup complete. Host name is ahost.local. Local service cookie is 1085925936.
43 ahost avahi-daemon[601]: Service "apt-cacher-ng proxy on ahost" (/services/apt-cacher-ng.service) successfully established.
³ eg:
$ avahi-browse -art | wc -l
126
$ avahi-browse -art | grep -i -e address -e host -e 169 | sort -u
address = [127.0.0.1]
address = [192.168.1.107]
address = [192.168.1.12]
address = [192.168.1.14]
address = [fe80::a612:34ff:fe56:7890]
hostname = [BRW90000B00E000.local]
hostname = [X00000JAAAAA.local]
hostname = [ahost.local]
$
⁴ second wifi AP and ethernet switch for the other half of the house.
⁵ these addresses are reserved in the primary router for our devices,
recognised by their MACs.
⁶ the redistribution command mangles the destination host's original
entry, and also appends the 10k line list of domains.
Cheers,
David.
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