Re: PMTUD broken inside network namespace with multipath routing

Hi David,

In this case, both paths are in the same layer2 network, there is no
symmetric multi-path routing.
If original message takes path 1, ICMP response will come from path 1
If original message takes path 2, ICMP response will come from path 2
Also, It works fine outside of LXC.


Thank you,
Kfir

On Mon, Aug 3, 2020 at 4:32 PM David Ahern [off-list ref] wrote:

On 8/3/20 5:14 AM, mastertheknife wrote:

quoted

What seems to be happening, is that when multipath routing is used
inside LXC (or any network namespace), the kernel doesn't generate a
routing exception to force the lower MTU.
I believe this is a bug inside the kernel.

Known problem. Original message can take path 1 and ICMP message can
path 2. The exception is then created on the wrong path.