Reg must constraint for leaf can be updated only once

YANG
1

Hi,
My yang is like this

container c1 {
leaf l1;
leaf l2;

}
we have a requirement like, one one time leaf value can be set. After that, leaf values must not be modified . Only user can delete and change these values back. Is there any provision to support this through yang must constraint.

Thanks
Phani

2

The standard approach is to disable modifications of those two leaves using NACM rules denying the update operation; something like

nacm rule-list myrule
 group [ myusers ]
 rule l1
  module-name       mymodule
  path              /c1/l1
  access-operations update
  action            deny
 !
 rule l2
  module-name       mymodule
  path              /c1/l2
  access-operations update
  action            deny
 !
!

The group myusers should contain all users that should be afffected by these rules; or you can use * to affect really everyone.