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#1 2011-03-07 21:55:37

jwhendy
Member
Registered: 2010-04-01
Posts: 552

[SOLVED] Attempt to follow wiki and disable ipv6 not working

I followed the guide on the wiki for disabling ipv6 entirely, but it's not working.

$ cat /etc/modprobe.d/modprobe.conf 
#
# /etc/modprobe.d/modprobe.conf (for v2.6 kernels)
#

options ipv6 disable=1

I even went the extra step with mkinitcpio:

$ grep modprobe /etc/mkinitcpio.conf
# Some users may wish to include modprobe.conf for custom module options,
#    FILES="/etc/modprobe.conf"
FILES=" /etc/modprobe.d/modprobe.conf"

and then rebuilt with:

$ sudo mkinitcpio -k 2.6.37-ARCH -g /boot/kernel26.img

We look at a log:

$ sudo grep -i ipv /var/log/messages.log
Mar  7 00:37:36 localhost kernel: IPv6: Loaded, but administratively disabled, reboot required to enable
Mar  7 08:35:40 localhost kernel: IPv6: Loaded, but administratively disabled, reboot required to enable
Mar  7 09:00:21 localhost kernel: IPv6: Loaded, but administratively disabled, reboot required to enable
Mar  7 12:05:52 localhost kernel: IPv6: Loaded, but administratively disabled, reboot required to enable
Mar  7 12:46:34 localhost kernel: IPv6: Loaded, but administratively disabled, reboot required to enable
Mar  7 15:01:19 localhost kernel: IPv6: Loaded, but administratively disabled, reboot required to enable

So kind of seems like it's working. But wait...

$ lsmod |grep ipv
ipv6                  280362  0

This is the case upon every boot. Where is this getting inserted from? It's still sitting there eating up that 280k.

Last edited by jwhendy (2011-03-10 18:57:35)

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#2 2011-03-07 22:11:49

adee
Member
From: The Moon
Registered: 2009-11-10
Posts: 107

Re: [SOLVED] Attempt to follow wiki and disable ipv6 not working

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#3 2011-03-07 22:43:34

parintachin
Member
Registered: 2009-05-25
Posts: 72

Re: [SOLVED] Attempt to follow wiki and disable ipv6 not working

you could just blacklist it in /etc/modprobe.d/modprobe.conf this way it won't get loaded with the entry you made the module still get's loaded but is disabled

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#4 2011-03-08 01:05:22

jwhendy
Member
Registered: 2010-04-01
Posts: 552

Re: [SOLVED] Attempt to follow wiki and disable ipv6 not working

@adee: confirmed. That works for me.

@parintachin: the wiki specifically states (for method 1):
,-----
| Adding the following line to /etc/modprobe.d/modprobe.conf will disable the automatic loading of ipv6...
`-----

And that was simply in reference to disabling until needed.

Wouldn't you take Method 2, which aims to disable it entirely, to go even further (implying that it's also not loaded and not even accessible)?

I don't get why a wiki entry about disabling a module (and referencing freeing up 250k of mem) would end up posting ways that don't actually disable it. Furthermore, I don't understand why it recommends quasi-convoluted methods when '!ipv6' is so darn simple. In fact, !ipv6 -> /etc/rc.conf is actually what I expected when I first went to the article but figured since it was coming from a somewhat authoritative source that some shennanigans must be necessary to kill this beast.

I guess my problem is all fixed, but I'm still puzzled as to 1) why the recommended way (at least the second) doesn't do what it's supposed to and 2) why in the world one would add lines like that to /etc/modprobe.d/modprobe.conf when a simply entry in /etc/rc.conf is apparently all that's needed.

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#5 2011-03-10 02:49:57

jwhendy
Member
Registered: 2010-04-01
Posts: 552

Re: [SOLVED] Attempt to follow wiki and disable ipv6 not working

No more answers? If someone can respond to my last post I can update the wiki with whatever it should contain.

Last edited by jwhendy (2011-03-10 02:50:15)

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#6 2011-03-10 17:56:14

Leonid.I
Member
From: Aethyr
Registered: 2009-03-22
Posts: 948

Re: [SOLVED] Attempt to follow wiki and disable ipv6 not working

jwhendy wrote:

No more answers? If someone can respond to my last post I can update the wiki with whatever it should contain.

http://patchwork.kernel.org/patch/9787/

~> /sbin/modinfo ipv6
filename:       /lib/modules/2.6.37-ARCH/kernel/net/ipv6/ipv6.ko.gz
alias:          net-pf-10
license:        GPL
description:    IPv6 protocol stack for Linux
author:         Cast of dozens
depends:        
vermagic:       2.6.37-ARCH SMP preempt mod_unload 686 
parm:           disable:Disable IPv6 module such that it is non-functional (int)
parm:           disable_ipv6:Disable IPv6 on all interfaces (int)
parm:           autoconf:Enable IPv6 address autoconfiguration on all interfaces (int)

"options ipv6 disable=1" will not prevent the module from loading, but merely disable ITS FUNCTIONALITY (this is done in case something else needs the module itself to be loaded); "options ipv6 disable_ipv6=1" will probably stop module loading (hasven't checked myself); the right way is, of course, through aliases, defined in /usr/src/linux-2.6.37-ARCH/include/linux/socket.h.

Last edited by Leonid.I (2011-03-10 17:58:54)


Arch Linux is more than just GNU/Linux -- it's an adventure

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#7 2011-03-10 18:57:03

jwhendy
Member
Registered: 2010-04-01
Posts: 552

Re: [SOLVED] Attempt to follow wiki and disable ipv6 not working

@Leonid: awesome. I've added this post to the wiki as an additional resource and added a note about the disable_ipv6 option not preventing loading of the module. I was going to add a "method 3" with blacklisting via modprobe.conf as suggested above,  but the wiki suggests that this isn't a reliable option, as if something depends on a blacklisted module, it will get loaded anyway.

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#8 2011-05-17 08:25:00

semeion
Member
From: Brazil
Registered: 2008-10-20
Posts: 56

Re: [SOLVED] Attempt to follow wiki and disable ipv6 not working

If i blacklist ipv6 in modprobe.conf my internet stop work.

/etc/modprobe.d/modprobe.conf
blacklist ipv6

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#9 2011-11-16 23:44:58

dcbdbis
Member
From: Aurora, Colorado
Registered: 2004-09-10
Posts: 215

Re: [SOLVED] Attempt to follow wiki and disable ipv6 not working

I'm a little late to the party. My apologies. My son informed me of potential issues today on his fresh Arch install.

Here are the actions I have taken. My son choose option 1 in the wiki (wisely IMHO). I wish to warn all those who may read this, to make sure what your ISP is pushing down the wire. As one poster mentions, disabling ipv6 on an ISP which uses IPV6 will render your system's network inoperative.

Here in Colorado, Comcast is my ISP, and they bought such a massive block of IPV4 addresses that they have no plans for the foreseeable future of requiring end users to use IPV6. I'm not endorsing one over the other, I'm just stating that it is.

I took several, and what some would consider unnecessary steps, but on my x86_64 system, coupled with my particular ISP, I can tell you that this works in a sovereign manner.


//-----------Begin Firefox tweaks

Firefox defaults to ipv6, so I tweaked Firefox to not even look for ipv6, which could potentially cause the ipv6 module to be demand loaded. Here are my actions in FireFox 8:

Step #1: Go to "about:config"

Step #2: Search for "ipv".

You will get three entries that show up.
The top one is:
"network.dns.disableIPv6"
I changed mine to "true"

The bottom entry is:
"network.http.fast-fallback-to-IPv4"
I changed mine to true.

//------End Firefox tweaks


//------Begin system tweaks

In modprobe.d, I blacklisted ipv6 in the same manner and in the same file where I blacklisted the "nouveau" drivers (I'm on an NVidia platform).

I then rebooted and performed a few tests. I read one post where one individual stated that he lost all network connectivity, which tells me that his ISP was using ipv6 only. But nonetheless, I was cautious and performed some due-diligence.

Then I read another post where under certain circumstance the ipv6 module is loaded anyway. This was not the case on my system, but you could blacklist the module at the kernel line of the "/boot/grub/menu.lst" at kernel boot time if you really want to hamstring ipv6.

//-----------End system tweaks


//--------Tests performed:

Step #1: Reboot. Using lsmod verified that ipv6 was not loaded.

Step #2: I "pacman -Syy" to verify that I still had network connectivity

Step #3: Using lsmod, I again verified that ipv6 had not been "demand loaded".

Step #4:  I then launched my "X" session into LXDE and tested FireFox. I went to a couple of different websites to verify connectivity, and also visited a new site that had streaming media content to ensure that streaming video was still working.

Step #5: I launched a terminal session, and again using "lsmod" verified that ipv6 had not been loaded.

Step #6: Launched Thunderbird and did a full email run and verified that the two accounts I have, gmail and comcast, were still functioning. I then sent an email to my son, and he replied, thus verifying that smtp was still happy as was pop.

Step #7: Launched another terminal and did another lsmod. Again verified that ipv6 had not been loaded.

Step #8: Went to several bandwidth speed test websites and verified my throughput. My down/up speeds remained exactly where they have always been. No faster, not slower, just spot on.

Step #9: Using the NoMachine client software, I connected to a client's server that I support to verify connectivity. It worked perfectly.

Step #10: Back to another terminal, and another lsmod. I confirmed that ipv6 did not get loaded.

//----------End tests


I can verify on my system, that when I performed the above changes, I did not affect my connectivity in any way. Please Remember, that  my ISP is IPV4 centric. If your ISP is IPV6 centric, performing my steps above will kill your connectivity.

In the end, I agree with my son's assessment (He's a Net Eng). In time IPV6 will take the lead. The methods I performed above, will require undoing if my ISP ever requires IPV6 from the end user. He used "Method #1" in the wiki. His IPV6 continues to get loaded, but the functionality is off.............that is until needed.

I did these tests on my system to determine how to disable IPV6, in a totalitarian manner. It is for this purpose that I share my tests for those of you who want IPV6 totally hamstrung and out of your systems.

I recommend that for the majority, use "Method #1" in the wiki. I'm an old developer, so I don't mind the extra steps.

FWIW:


Sincerely and respectfully,

Dave

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