On 8/21/21 12:10 AM, Rocco Yue wrote:

In this patch, if an RA no longer carries an MTU or if accept_ra_mtu is reset,
in6_dev->ra_mtu will not be reset to 0, its value will remain the previous
accept_ra_mtu=1 and the value of the mtu carried in the RA msg. This behavior
is same with mtu6. This should be reasonable, it would show that the device
had indeed received the ra_mtu before set accept_ra_mtu to 0 or an RA no longer
carries an mtu value. I am willing to listen to your suggestions and make
changes if needed, maybe it needs to add a new separate proc handler for
accept_ra_mtu.

fair point. Consistency is important.

In addition, at your prompt, I find that this patch maybe have a defect for
some types of virtual devices, that is, when the state of the virtual device
updates the value of ra_mtu during the UP period, when its state is set to
DOWN, ra_mtu is not reset to 0, so that its ra_mtu value remains the previous
value after the interface is re-UP. I think I need to fix it.

Please do. Also, that problem should apply to all netdev's not just
virtual devices if you are referring to admin down (e.g., ip link set
$DEV down)