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SubjectRe: [PATCH] IPv6: Allow the MTU of ipip6 tunnel to be set below 1280
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The ip6_tunnel.c module would be then dependent on ip_tunnel.c and may
be it would not be good thing?
As I have check in v3.10 there is no call from ip6_tunnel to ip_tunnel...

For information, there is no check for the maximum MTU for ipv4 in the
patch as this is not done for ipv6.

Regards,
Oussama

On Fri, Sep 27, 2013 at 9:37 AM, Hannes Frederic Sowa
<hannes@stressinduktion.org> wrote:
> On Thu, Sep 26, 2013 at 03:51:48PM +0100, Oussama Ghorbel wrote:
>> The (inner) MTU of a ipip6 (IPv4-in-IPv6) tunnel cannot be set below 1280, which is the minimum MTU in IPv6.
>> However, there should be no IPv6 on the tunnel interface at all, so the IPv6 rules should not apply.
>> More info at https://bugzilla.kernel.org/show_bug.cgi?id=15530
>>
>> This patch allows to check the minimum MTU for ipv6 tunnel according to these rules:
>> -In case the tunnel is configured with ipip6 mode the minimum MTU is 68.
>> -In case the tunnel is configured with ip6ip6 or any mode the minimum MTU is 1280.
>>
>> Signed-off-by: Oussama Ghorbel <oghorbell@gmail.com>
>> ---
>> net/ipv6/ip6_tunnel.c | 10 ++++++++--
>> 1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
>> index 1e55866..a66ead2 100644
>> --- a/net/ipv6/ip6_tunnel.c
>> +++ b/net/ipv6/ip6_tunnel.c
>> @@ -1423,8 +1423,14 @@ ip6_tnl_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
>> static int
>> ip6_tnl_change_mtu(struct net_device *dev, int new_mtu)
>> {
>> - if (new_mtu < IPV6_MIN_MTU) {
>> - return -EINVAL;
>> + struct ip6_tnl *t = netdev_priv(dev);
>> +
>> + if (t->parms.proto == IPPROTO_IPIP) {
>> + if (new_mtu < 68)
>> + return -EINVAL;
>
> Maybe you could have a look at ip_tunnel_change_mtu in ipv4/ip_tunnel.c,
> generalize this check as e.g. ip_tunnel_valid_mtu or something and use it
> here? Maybe an af-independent ip_tunnel_max_mtu()?
>
>> + } else {
>> + if (new_mtu < IPV6_MIN_MTU)
>> + return -EINVAL;
>
> This check could also be used here, then.
>
>> }
>> dev->mtu = new_mtu;
>> return 0;
>
> Thanks,
>
> Hannes
>


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