Thread: N900 disable ipv6
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Malakai is offline Malakai
2017-02-15 , 15:43
Posts: 175 | Thanked: 210 times | Joined on Mar 2013
#10
Thanks pali for the clarifications, really instructive.

Originally Posted by pali View Post
1) Stock kernel does not support IPv6, so by default there is no way to open/bind IPv6 socket
I installed kernel power on my N900.

Originally Posted by pali View Post
2) Basically all default Maemo 5 applications have disabled IPv6 support, so they do not try to open/bind IPv6 socket (even you have kernel with IPv6 support)
Good to know. This means that only dnsmasq makes queries for AAAA addresses.

Originally Posted by pali View Post
3) Disabling IPv6 support can be achieved by sysctl which you already wrote. When disable_ipv6=1 then *no* userspace application is able to open/bind IPv6 socket. Kernel acts same as if IPv6 support was disabled at compile time.
Where can I add the disable_ipv6=1 to disable ipv6 at boot, as Maemo doesn't seem to have /etc/sysctl.conf.

Originally Posted by pali View Post
4) Asking DNS server for AAAA record has nothing and absolutely nothing with IPv6 support. You can ask for AAAA record of some hostname via IPv6 DNS socket and also via *IPv4* DNS socket. POSIX applications uses getaddrinfo() function (see man 3 getaddrinfo) which is supposed to do DNS lookups.
That explains why I see AAAA queries even if I don't have an ipv6 address. The queries are made through ipv4. My question would now be how to prevent dnsmasq from querying ipv6? Tried to search for it on the web with no real success.

Originally Posted by pali View Post
5) Router has nothing allowing IPv6 connections and AAAA queries. Those are two different things which has nothing in common. DNS is application protocol (layer 7) and IPv6 is network protocol (layer 3).
When getting home I will try to see if other devices query the router for ipv6 addresses or only ipv4.

Originally Posted by pali View Post
6) DNS resolving does not have to be slow "because of IPv6". You can ask (and system libraries probably do it) for ANY address for some host and you get both IPv4 and IPv6 address.
I was believing that because on dnsmasq logs I always see AAAA queries and then A queries, but if you say that there is no impact on DNS resolution then I believe you

Originally Posted by pali View Post
7) IPv6 Link-Local address cannot be used for making "internet" connection and IIRC connect() is not possible.
Seems logical.

Originally Posted by pali View Post
So... In IPv4-only network there should be absolutely no penalty with enabled IPv6 support in kernel or applications.

Problem can be in IPv4-only network which advertise IPv6 availabilty (which is non-working). But simple disabling IPv6 in kernel fixes it.

So if you are seeing some problems even after disabling IPv6 then it is probably not IPv6 related.
Can't say that I have a real problem now, just wanted to be sure that it is deactivated and that it couldn't produce problems in a future specific situation, like my N900 connecting to an ipv6 network (I wouldn't want to have an ipv6 address in this situation ; only ipv4).

So to resume :
Where can I add the disable_ipv6=1 to disable ipv6 at boot, as Maemo doesn't seem to have /etc/sysctl.conf.
How to prevent dnsmasq from querying ipv6?

Thanks.