Re: nd6_setmtu0: new link MTU on iwn0 (576) is too small for IPv6 which needs 1280

[Ottavio Caruso <ottavio2006-netbsd%yahoo.com@localhost>]

On 3 December 2014 at 01:56, Christos Zoulas <christos%astron.com@localhost> wrote:
> In article <CAEJNuHwUsHp3V19eFvJ-D9Dt6Fu172OJVMtSL7k+k=vYJdUcmw%mail.gmail.com@localhost>,
> Ottavio Caruso  <ottavio2006-netbsd%yahoo.com@localhost> wrote:
>>Hello,
>>
>>uname -a:
>>NetBSD  6.1.5_PATCH NetBSD 6.1.5_PATCH (GENERIC) amd64
>>
>>I have a problem with wireless connection and Netbsd that I don't have
>>with Windows 7 and Linux.
>>
>>In the console I see:
>>nd6_setmtu0: new link MTU on iwn0 (576) is too small for IPv6 which
>>needs 1280
>>iwn0: discarding oversize frame (len=1484)
>>
>>In "ifconfig iwn0" I have:
>>
>>iwn0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 576
>>ssid TP-LINK_E6D338
>>powersave off
>>bssid 00:27:19:e6:d3:38 chan 6
>>address: 00:21:5c:55:ee:9d
>>media: IEEE802.11 autoselect (DS5 mode 11g)
>>status: active
>>inet 192.168.1.108 netmask 0xffffff00 broadcast 255.255.255.255
>>inet6 fe80::221:5cff:fe55:ee9d%iwn0 prefixlen 64 scopeid 0x2
>>
>>Before connecting to the router the mtu was 1500 as it should be.
>>
>>I can connect to the router but cannot browse any website.
>>
>>I have manually changed the mtu on iwn0 to 1500 but I still have the
>>same problem.
>>
>>I have removed all references to ip6 in rc.conf and rebooted the pc
>>but no avail.
>>
>>I have played with the "ip6mode" value in rc.conf, setting it to
>>"autohost" also to no avail.
>>
>>I have a good connection with the router and can ping any website, but
>>I can't traceroute or browse any website.
>>
>>I have used Netbsd in the past with various routers and I've never had
>>any problem.
>>
>>Any help willl be appreciated.
>>
>
> Try turning off mtu discovery via sysctl.... Perhaps the router or
> something else is causing that. Can you ping the router? What size
> packets will the router accept (ping with different sizes)?
>

Hi Christos,

before launching wpa_gui the MTU is set to 1500, after connecting to
the router it is 576. I can ping the router and any site fine, simply
I cannot reach them using http.

If I am not wrong I could turn off path MTU discovery on NetBSD with:

 sysctl -w net.inet.ip.mtudisc=0

Can you confirm me that?

I also guess that the router wants to speak IPv6 and makes some error.
How could I turn IP6 altogether?