Thanks for doing this work, much appreciated.

I haven't tested your patches yet, but when I was attempting this,
I needed the attached patch to get it to work with bridging and
netfilter, otherwise gre tries to call
skb->dst->ops->update_pmtu(skb->dst, mtu);


Herbert Xu wrote:
> @@ -530,7 +572,13 @@ static int ipgre_rcv(struct sk_buff *skb)
>  		dst_release(skb->dst);
>  		skb->dst = NULL;
>  		nf_reset(skb);
> +
> +		if (tunnel->dev->type == ARPHRD_ETHER)
> +			skb->protocol = eth_type_trans(skb, skb->dev);

Do you need to check pskb_may_pull(skb, ETH_HLEN)?

> +
> +		skb_reset_network_header(skb);
>  		ipgre_ecn_decapsulate(iph, skb);
> +
>  		netif_rx(skb);
>  		read_unlock(&ipgre_lock);
>  		return(0);