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Router-advert: Preferred lifetime cannot equal valid lifetime in PIOs
Needs testing, Requires assessmentPublic

Description

Currently the syntax validation for the preferred-lifetime and valid-lifetime fields in a prefix information option within the router advertisement configuration block does not allow the preferred lifetime duration to equal the valid lifetime duration. A reading of RFC 4861 § 4.6.2 states that the preferred lifetime cannot exceed the valid lifetime but does not say it cannot equate it. Attempting to set both values to be the same as below:

 interface eth0 {
     prefix ::/64 {
+        preferred-lifetime 86400
         valid-lifetime 86400
     }
 }

will yield the following error on commit:

Prefix valid-lifetime must be greater then preferred-lifetime

radvd exhibits correct behaviour and will accept a radvd.conf with preferred lifetime equal to valid lifetime, so the issue exists solely in the validation stage within VyOS.

A side effect of this is that setting a preferred lifetime of infinity is not possible.

Relevant PRs:

https://github.com/vyos/vyos-1x/pull/1447
https://github.com/vyos/vyos-1x/pull/1448

Details

Difficulty level
Unknown (require assessment)
Version
-
Why the issue appeared?
Will be filled on close
Is it a breaking change?
Perfectly compatible
Issue type
Bug (incorrect behavior)

Event Timeline

Viacheslav changed the task status from Open to Needs testing.Mon, Aug 1, 7:54 AM
Viacheslav assigned this task to initramfs.