IPv6 addresses randomly vanish

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Re: IPv6 addresses randomly vanish

Postby summers » Wed Oct 13, 2021 5:37 pm

Still going through it - one obvious difference is mine brings up a DHCPv6 Client:
$this->bbcode_second_pass_code('', 'Oct 12 23:41:42 nas systemd-networkd[439]: NDISC: Sent Router Solicitation, next solicitation in 4s
Oct 12 23:41:42 nas systemd-networkd[439]: NDISC: Received Router Advertisement: flags MANAGED preference medium lifetime 1800 sec
Oct 12 23:41:42 nas systemd-networkd[439]: NDISC: Invoking callback for 'router' event.
Oct 12 23:41:42 nas systemd-networkd[439]: DHCPv6 CLIENT: Started in Managed mode
Oct 12 23:41:42 nas systemd-networkd[439]: eth0: Acquiring DHCPv6 lease on NDisc request
')then I get fairly regular$this->bbcode_second_pass_code('', 'Oct 12 23:49:35 nas systemd-networkd[439]: DHCPv6 CLIENT: Sent SOLICIT
Oct 12 23:49:35 nas systemd-networkd[439]: DHCPv6 CLIENT: Next retransmission in 1min 58s
Oct 12 23:49:59 nas systemd-networkd[439]: NDISC: Received Router Advertisement: flags MANAGED preference medium lifetime 1800 sec
Oct 12 23:49:59 nas systemd-networkd[439]: NDISC: Invoking callback for 'router' event.
Oct 12 23:49:59 nas systemd-networkd[439]: eth0: Acquiring DHCPv6 lease on NDisc request
')
Which sets the IPv6 addresses - so my systemd-networkd is operating very differently from yours. Do you have a line like:
$this->bbcode_second_pass_code('', 'Oct 12 23:41:40 nas systemd-networkd[439]: eth0: IPv6 successfully enabled
Oct 12 23:41:40 nas systemd-networkd[439]: Setting '/proc/sys/net/ipv6/conf/eth0/proxy_ndp' to '0'
Oct 12 23:41:40 nas systemd-networkd[439]: Setting '/proc/sys/net/ipv4/ip_forward' to '1'
Oct 12 23:41:40 nas systemd-networkd[439]: Setting '/proc/sys/net/ipv6/conf/all/forwarding' to '1'
Oct 12 23:41:40 nas systemd-networkd[439]: Setting '/proc/sys/net/ipv6/conf/eth0/use_tempaddr' to '2'
Oct 12 23:41:40 nas systemd-networkd[439]: Setting '/proc/sys/net/ipv6/conf/eth0/accept_ra' to '0'
Oct 12 23:41:40 nas systemd-networkd[439]: LLDP: Started LLDP client
Oct 12 23:41:40 nas systemd-networkd[439]: eth0: Started LLDP.
Oct 12 23:41:40 nas systemd-networkd[439]: eth0: Setting address genmode for link
') which for me disables the kernel RA by setting accept_ra to zero.

What do you have in your [NETWORK] section of the interface definition. The man says:
$this->bbcode_second_pass_code('', 'DHCP=

Enables DHCPv4 and/or DHCPv6 client support. Accepts "yes", "no", "ipv4", or "ipv6". Defaults to "no".

Note that DHCPv6 will by default be triggered by Router Advertisement, if that is enabled, regardless of this parameter. By enabling DHCPv6 support explicitly, the DHCPv6 client will be started regardless of the presence of routers on the link, or what flags the routers pass. See "IPv6AcceptRA=".

Furthermore, note that by default the domain name specified through DHCP is not used for name resolution. See option UseDomains= below.

See the [DHCPv4] or [DHCPv6] sections below for further configuration options for the DHCP client support.')
summers
 
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Joined: Sat Sep 06, 2014 12:56 pm

Re: IPv6 addresses randomly vanish

Postby stefguy » Thu Oct 14, 2021 5:54 pm

yes, it looks like our setups are different. I have DHCPv6 completely disabled on the router.

The network section of the system is

$this->bbcode_second_pass_code('', '
[Network]
DHCP=yes
DNSSEC=no
Domains=blahblah1.vnet blahblah2.vnet
')

I will change this to
$this->bbcode_second_pass_code('', '
[Network]
DHCP=ipv4
IPv6AcceptRA=yes
DNSSEC=no
Domains=blahblah1.vnet blahblah2.vnet
')

this should just make implicit settings explicit .. let's see if things change. IPv4 DHCP is enabled and works fine. I also get this message stating that '/proc/sys/net/ipv6/conf/eth0/accept_ra' tis set '0' .. I double-checked, it is.

if this check doesn't change anything (we'll see in 2 days) I will downgrade systemd to 248.x and test with that version

greetings, Stef
stefguy
 
Posts: 18
Joined: Fri Jul 13, 2018 2:55 pm

Re: IPv6 addresses randomly vanish

Postby summers » Thu Oct 14, 2021 6:45 pm

Strange DHCP=true should enable both ipv4 and ipv6. Also IPv6AcceptRA=true should force ipv6 dhcp to load. So why you don't see these in the log is very strange which systemd version are you on $this->bbcode_second_pass_code('', 'pacman -Qi systemd') gives 249.4-2 for me.
summers
 
Posts: 984
Joined: Sat Sep 06, 2014 12:56 pm

Re: IPv6 addresses randomly vanish

Postby summers » Fri Oct 15, 2021 10:11 pm

Keep coming back to this thread. Its the way something strange is happening, bits are consistent, but bits odd.

Think what really *****, is that we are both doing pretty much the same thing. But mine works, and yours fails across multiple platforms. So we mush be doing something different. But can`t see what. Only things that stand out is I probably only update most boxes once a month. My NAS and beaglebone black get very rare updates, as both are HDD (well flash) limited, so updates are painful.

The other difference is I do set up network files on all boxes, but these are all simple, and not really doing anything you aren't. When on my desktop, I grab a simple one, just so we can compare.

OK - have just done logging on my odroid c2 as its a really simple set up. It also starts dhcp6 client:
$this->bbcode_second_pass_code('', 'Oct 16 08:19:18 odroid-c2 systemd-networkd[306]: eth0: NDISC: Started IPv6 Router Solicitation client
Oct 16 08:19:18 odroid-c2 systemd-networkd[306]: Sent message type=signal sender=n/a destination=n/a path=/org/freedesktop/network1 interface=org.freedesktop.DBus.Properties member=PropertiesChanged cookie=7 reply_cookie=0 signature=sa{s>
Oct 16 08:19:18 odroid-c2 systemd-networkd[306]: eth0: Remembering foreign route: dst: fe80::21e:6ff:fe35:417c/128, src: n/a, gw: n/a, prefsrc: n/a, scope: global, table: local(255), proto: kernel, type: local, nexthop: 0, priority: 0
Oct 16 08:19:20 odroid-c2 systemd-networkd[306]: eth0: NDISC: Sent Router Solicitation, next solicitation in 4s
Oct 16 08:19:20 odroid-c2 systemd-networkd[306]: eth0: NDISC: Received Router Advertisement: flags MANAGED preference medium lifetime 1800 sec
Oct 16 08:19:20 odroid-c2 systemd-networkd[306]: eth0: NDISC: Invoking callback for 'router' event.
Oct 16 08:19:20 odroid-c2 systemd-networkd[306]: eth0: DHCPv6 client: Started in Managed mode
Oct 16 08:19:20 odroid-c2 systemd-networkd[306]: eth0: Acquiring DHCPv6 lease on NDisc request
')
It has the simple set up: /etc/systemd/network/eth0.network $this->bbcode_second_pass_code('', '[Match]
Name=eth0

[Network]
DHCP=yes')

I guess another obvious difference in our set up - is for me, I'm doing well if my IPv6 number lasts a few days, my ADSL router reconnects more often than that, and on each reconnect I get a new IPv6 number, which propagates down to my LAN.
summers
 
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Joined: Sat Sep 06, 2014 12:56 pm

Re: IPv6 addresses randomly vanish

Postby stefguy » Wed Oct 20, 2021 12:07 pm

G'day,

quick update on what happened the last days: updated the HC1 on friday and make /etc/systemd/network/eth0.network look like this:

$this->bbcode_second_pass_code('', '
[Match]
Name=eth0

[Network]
DHCP=ipv4
IPv6AcceptRA=yes
DNSSEC=no
Domains=xxx.vnet yyy.vnet
')

so that a few 'implicit' things are configured explicit now. Sunday, when approaching the 2 days uptime mark, addresses started to disappear :-(

Monday morning I downgraded systemd and systemd-libs to 248.3 .. and guess what? 2 days and 2 hours later address config is stable. To early for a party, but eagerly whatching my interfaces :-)

I will downgrade a Pi3 later today .. let's see ..

Stef
stefguy
 
Posts: 18
Joined: Fri Jul 13, 2018 2:55 pm

Re: IPv6 addresses randomly vanish

Postby stefguy » Fri Oct 22, 2021 10:50 am

4 days of uptime and the ipv6 addresses stay up on the interface of my HC1. I have downgraded all of my Raspberries to systemd 248, let's see how they behave (it took 5 days to make the addresses come and go there).
Additionally I set up a Pi Zero W (ARMv6) with current systemd to see if I can reproduce the issue there.

So my current assumption is that something changed from systemd-248 to systemd-249, which is the cause for the behaviour I see. I would like to open a ticket, but not sure where, systemd, Arch, anywhere else? Any advice from the forum?

Greeting, Stef
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Posts: 18
Joined: Fri Jul 13, 2018 2:55 pm

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