From: "Du, Fan" <redacted>
Date: Wed, 3 Dec 2014 03:32:46 +0000

quoted

If guest sees a 1500 byte MTU, that's it's link layer MTU and it had better be able to
send 1500 byte packets onto the "wire".

This patch makes it happens exactly as you putted.

quoted

If you cannot properly propagate the vxlan encapsulation overhead back into the
guest's MTU you must hide this problem from the rest of our stack somehow.

Again, this patch hide this problem to make Guest feel it can send packet with MTU as 1500 bytes.

I said make the guest see the real MTU, not hide the real MTU by
fragmenting or spitting ICMP PMTU messages back.