David Ahern <dsah...@gmail.com> wrote:
> On 7/17/20 6:27 AM, Stefano Brivio wrote:
> >> Every type of bridge port that needs to add additional header on egress
> >> has this problem in the bridge scenario once the peer of the IP tunnel
> >> signals a PMTU event.
> >
> > Yes :(
> >
>
> The vxlan/tunnel device knows it is a bridge port, and it knows it is
> going to push a udp and ip{v6} header. So why not use that information
> in setting / updating the MTU? That's what I was getting at on Monday
> with my comment about lwtunnel_headroom equivalent.
What action should be taken in the vxlan driver? Say, here:
static inline void skb_dst_update_pmtu_no_confirm(struct sk_buff *skb,
u32 mtu)
{
struct dst_entry *dst = skb_dst(skb);
if (dst && dst->ops->update_pmtu)
dst->ops->update_pmtu(dst, NULL, skb, mtu, false);
else
/* ??? HERE */
}
We hit the (non-existent) else branch as skb has no dst entry.
