[Solved] dhcpcd invalid prefix / journal excessive disk access

aardwolf · 2014-06-01 09:55:31

Hello,

The disk of my computer just never rests, every few seconds it makes a churning sound.

I used "iotop" to see what does most disk writes, and it appears to be systemd-journal.

I suppose it's constantly writing to a log.

Is there a way to configure this to write much less frequently?

Thanks!

EDIT: A process called "jbd2/sda1-8" pops up quite often on top as well, and then firefox also used to do a lot of disk writes but I think I fixed that by making it cache to ram.

EDIT2: I looked at the actual journal now, and found why it's writing so much. Every few seconds the same message: "dhcpcd[530]: eth0: invalid prefix in RA" followed by "dhcpcd[530]: ipv6nd_handlera: Success". I saw that a way to get rid of it is to add "noipv6rs" to "/etc/dhcpcd.conf". Doing that and restarting network indeed stopped all disk noise! So dhcpcd is log-spamming every few seconds for no good reason! Is it a bug? I tried to search for "invalid prefix in RA" but it does not give good search results on how to fix it properly. Any ideas? Thanks!

Last edited by aardwolf (2014-06-03 12:19:17)

Lone_Wolf · 2014-06-01 12:36:30

RA appears to stand for Relay Agent .

What i THINK happens :

- your computer issues a dhcpv6 request
- your router detects it's not authorized to give out a dhcpv6 address for your local network
- your router transmits the address of router2 that IS authorized
- your computer receives an ipv6 address/prefix combination for router2 but can't use it to contact router2 due to invalid prefix

I see 2 possible causes :
- a bug in dhcpcd
- a misconfiguration in your router

I suggest you contact your provider to verify if the router is correctly configured for ipv6 .

aardwolf · 2014-06-01 19:26:04

Thanks a lot. That's really interesting. I was exactly wondering what RA could mean

I looked through all the settings of the router, and could not find any setting related to ipv6. However, it is showing all devices in the network, most of them with both an ipv6 address and ipv4 address, but my desktop only with ipv4 (maybe because I disabled ipv6 as described above?). So at least the router knows about ipv6 and can display it... No idea why it wouldn't allow dhcpv6. The only settings for DHCP it has is enable or disable, and an IP address range which is set to start from 192.168.1.101 and end at 192.168.1.161. I don't think this setting would accept ipv6 addresses. Could the fact that this range has ipv4 IP's be related?

Also, there's currently only one router in my home afaik, so not sure if there could be a router2.

Last edited by aardwolf (2014-06-01 19:27:38)

Lone_Wolf · 2014-06-02 12:01:33

aardwolf wrote:

Thanks a lot. That's really interesting. I was exactly wondering what RA could mean
I looked through all the settings of the router, and could not find any setting related to ipv6. However, it is showing all devices in the network, most of them with both an ipv6 address and ipv4 address, but my desktop only with ipv4 (maybe because I disabled ipv6 as described above?).
So at least the router knows about ipv6 and can display it... No idea why it wouldn't allow dhcpv6. The only settings for DHCP it has is enable or disable, and an IP address range which is set to start from 192.168.1.101 and end at 192.168.1.161. I don't think this setting would accept ipv6 addresses. Could the fact that this range has ipv4 IP's be related?
Also, there's currently only one router in my home afaik, so not sure if there could be a router2.

your desktop only showing with ipv4 address : yes, that's due to disabling ipv6 on it

The router2 i mentioned would be in the network of your isp, probably delivering dhcpv6 addresses to multiple customers.

Given that other devices in your network have no problem getting dhcpv6 addresses, a bug in dhcpcd is becoming more likely.

also check this thread : https://bbs.archlinux.org/viewtopic.php?id=139302 , especially the last post.

If you feel like investigating further, i think you should take this matter to upstream for dhcpcd.
(troubleshooting/ solving this will prob require very good network protocol knowledge)

aardwolf · 2014-06-03 00:28:37

> If you feel like investigating further, i think you should take this matter to upstream for dhcpcd.

I did, and that thread resulted in a bugfix to let dhcpcd make less noise, and a detailed response of what exactly my router is doing wrong after sending a tcpdump! Pretty awesome

Last edited by aardwolf (2014-06-03 00:33:14)

Lone_Wolf · 2014-06-03 10:45:28

Great, please edit the first post title.
something like " [Solved] dhcpcd invalid prefix / journal excessive disk access " would make it easier for others to find this is think.

a detailed response of what exactly my router is doing wrong after sending a tcpdump!

A link to the upstream bugreport / thread would also be useful.
While i do have network knowledge that detailed response is likely to be more valuable / correct then my description.

aardwolf · 2014-06-03 12:19:00

The thread is here: http://roy.marples.name/archives/dhcpcd … /0658.html

falconindy · 2014-06-03 13:14:51

FYI, RA is "router advertisement" not relay agent.

Lone_Wolf · 2014-06-04 09:55:04

after reading the dhcpcd mailing list thread, i realised that in this case RA meant Router Advertisement.

RA is also used in the dhcp protocol (both v4 and v6), and there it stands for Relay Agent.
Most occurences of that use had the form DHCP RA though, so it seems if RA is used by itself, it refers to router advertisement.

Arch Linux

#1 2014-06-01 09:55:31

[Solved] dhcpcd invalid prefix / journal excessive disk access

#2 2014-06-01 12:36:30

Re: [Solved] dhcpcd invalid prefix / journal excessive disk access

#3 2014-06-01 19:26:04

Re: [Solved] dhcpcd invalid prefix / journal excessive disk access

#4 2014-06-02 12:01:33

Re: [Solved] dhcpcd invalid prefix / journal excessive disk access

#5 2014-06-03 00:28:37

Re: [Solved] dhcpcd invalid prefix / journal excessive disk access

#6 2014-06-03 10:45:28

Re: [Solved] dhcpcd invalid prefix / journal excessive disk access

#7 2014-06-03 12:19:00

Re: [Solved] dhcpcd invalid prefix / journal excessive disk access

#8 2014-06-03 13:14:51

Re: [Solved] dhcpcd invalid prefix / journal excessive disk access

#9 2014-06-04 09:55:04

Re: [Solved] dhcpcd invalid prefix / journal excessive disk access

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