On Mon, 30 Apr 2012 07:51:33 +0200
Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote:
> On Mon, 2012-04-30 at 07:38 +0200, Frank Blaschka wrote:
> > From: Frank Blaschka <frank.blaschka@xxxxxxxxxx>
> >
> > commit 8a83a00b0735190384a348156837918271034144 unconditionally
> > drops dst reference when skb->dev is set. This causes a regression
> > with VLAN and the qeth_l3 network driver. qeth_l3 can not get gw
> > information from the skb coming from the vlan driver. It is only
> > valid to drop the dst in case of different name spaces.
> >
> > Signed-off-by: Frank Blaschka <frank.blaschka@xxxxxxxxxx>
> > ---
> > net/core/dev.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -1881,8 +1881,8 @@ EXPORT_SYMBOL(netif_device_attach);
> > #ifdef CONFIG_NET_NS
> > void skb_set_dev(struct sk_buff *skb, struct net_device *dev)
> > {
> > - skb_dst_drop(skb);
> > if (skb->dev && !net_eq(dev_net(skb->dev), dev_net(dev))) {
> > + skb_dst_drop(skb);
> > secpath_reset(skb);
> > nf_reset(skb);
> > skb_init_secmark(skb);
> >
>
> You forgot CC Arnd Bergmann <arnd@xxxxxxxx> ?
>
> But we do want to do the skb_dst_drop() in dev_forward_skb()
>
> Your patch breaks dev_forward_skb() then.
>
> But apparently this forward path was alredy broken in Arnd patch...
Is this related to why, PMTU discover is broken now over GRE.
The simple case of doing a TCP transfer from local host over
GRE tunnel hangs.
What happens is that skb_dst(skb) is null in ip_tunnel_xmit.
Which leads to the MTU not being updated, and the ICMP_FRAG_NEEDED
is never sent.
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