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Message-Id: <20141106.143351.1534959887749218818.davem@davemloft.net> Date: Thu, 06 Nov 2014 14:33:51 -0500 (EST) From: David Miller <davem@...emloft.net> To: steffen.klassert@...unet.com Cc: netdev@...r.kernel.org Subject: Re: [PATCH RFC net] ip_tunnel: Respect the IP_DF bit of the inner packet. From: Steffen Klassert <steffen.klassert@...unet.com> Date: Wed, 5 Nov 2014 09:09:30 +0100 > The pmtu calculation depends on the IP_DF bit in tnl_update_pmtu(). > If the IP_DF bit is set, the pmtu calculation is based on the outer > packet size. Otherwise it is based on the inner packet size. > If xfrm is used after tunneling through an ipip device, the mtu of > the outer device can be lower than the mtu of the ipip device. > Reporting the mtu of the ipip device is wrong in this case. So > respect the IP_DF bit of the inner packet on ipv4 to report the > calculated mtu of the outer device. > > Fixes: fd58156e456d ("IPIP: Use ip-tunneling code.") > Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com> > --- > > I marked this as RFC because it affects the mtu calculation of > gre tunnels too. I think it should be ok, but I have no testcase > to confirm the correctness for gre tunnels. So would be good if > someone with gre knowlegde could look at this. > > If it turns out that we can't do that for gre, we need to > split this code back into a gre and an ipip version. Looking quickly at this, the don't-frag handling in the pre-ip-tunneling GRE code conversion used different conditions wrt. calculating 'df'. It takes the frag off from skb->data's IPH when skb->protocol is GRE, for example. So we may have to do this split. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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