* The check of upper MTU limit when changing it in ip6 gre tunnel seems incorrect.
@ 2013-10-02 16:44 Oussama Ghorbel
2013-10-04 9:58 ` Oussama Ghorbel
0 siblings, 1 reply; 2+ messages in thread
From: Oussama Ghorbel @ 2013-10-02 16:44 UTC (permalink / raw)
To: netdev
The check of upper MTU limit when changing it in ip6 gre tunnel seems incorrect.
The function in question is:
static int ip6gre_tunnel_change_mtu(struct net_device *dev, int new_mtu)
{
struct ip6_tnl *tunnel = netdev_priv(dev);
if (new_mtu < 68 ||
new_mtu > 0xFFF8 - dev->hard_header_len - tunnel->hlen)
return -EINVAL;
dev->mtu = new_mtu;
return 0;
}
However the dev->hard_header_len and tunnel->hlen are initialized in
the following way in ip6gre_tnl_link_config():
int addend = sizeof(struct ipv6hdr) + 4;
...
dev->hard_header_len = rt->dst.dev->hard_header_len + addend;
...
t->hlen = addend; // t is ip6_tnl pointer
As you see the information t->hlen is already included in
dev->hard_header_len, so why calculate it twice?
Thanks
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: The check of upper MTU limit when changing it in ip6 gre tunnel seems incorrect.
2013-10-02 16:44 The check of upper MTU limit when changing it in ip6 gre tunnel seems incorrect Oussama Ghorbel
@ 2013-10-04 9:58 ` Oussama Ghorbel
0 siblings, 0 replies; 2+ messages in thread
From: Oussama Ghorbel @ 2013-10-04 9:58 UTC (permalink / raw)
To: netdev
I have sent this patch to address the issue.
[PATCH] Fix the upper MTU limit in ipv6 GRE tunnel
On Wed, Oct 2, 2013 at 5:44 PM, Oussama Ghorbel <ou.ghorbel@gmail.com> wrote:
> The check of upper MTU limit when changing it in ip6 gre tunnel seems incorrect.
> The function in question is:
>
> static int ip6gre_tunnel_change_mtu(struct net_device *dev, int new_mtu)
> {
> struct ip6_tnl *tunnel = netdev_priv(dev);
>
> if (new_mtu < 68 ||
> new_mtu > 0xFFF8 - dev->hard_header_len - tunnel->hlen)
> return -EINVAL;
> dev->mtu = new_mtu;
> return 0;
> }
>
> However the dev->hard_header_len and tunnel->hlen are initialized in
> the following way in ip6gre_tnl_link_config():
>
> int addend = sizeof(struct ipv6hdr) + 4;
> ...
> dev->hard_header_len = rt->dst.dev->hard_header_len + addend;
> ...
> t->hlen = addend; // t is ip6_tnl pointer
>
> As you see the information t->hlen is already included in
> dev->hard_header_len, so why calculate it twice?
>
> Thanks
^ permalink raw reply [flat|nested] 2+ messages in thread
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